Preface

This guide is part of a set of manuals that describe how to use the PGI Fortran, C, and C++ compilers and program development tools. These compilers and tools include the PGF95, PGFORTRAN, PGC++, PGCC ANSI C compilers and the PGI profiler. They work in conjunction with an OpenPOWER assembler and linker. You can use the PGI compilers and tools to compile, debug, optimize, and profile serial and parallel applications for OpenPOWER processor-based systems.

The PGI Compiler Reference Manual is the reference companion to the PGI Compiler User's Guide which provides operating instructions for the PGI command-level development environment. It also contains details concerning the PGI compilers' interpretation of the Fortran language, implementation of Fortran language extensions, and command-level compilation. Users are expected to have previous experience with or knowledge of the Fortran programming language. Neither guide teaches the Fortran programming language.

Audience Description

This manual is intended for scientists and engineers using the PGI compilers. To use these compilers, you should be aware of the role of high-level languages, such as Fortran, C, and C⁠+⁠+, as well as assembly-language in the software development process; and you should have some level of understanding of programming. You also need to be familiar with the basic commands available on your system.

Compatibility and Conformance to Standards

Your system needs to be running a properly installed and configured version of this PGI product. For information on installing PGI compilers and tools, refer to the Release Notes and Installation Guide included with your software.

For further information, refer to the following:

  • American National Standard Programming Language FORTRAN, ANSI X3. -1978 (1978).
  • ISO/IEC 1539-1 : 1991, Information technology – Programming Languages – Fortran, Geneva, 1991 (Fortran 90).
  • ISO/IEC 1539-1 : 1997, Information technology – Programming Languages – Fortran, Geneva, 1997 (Fortran 95).
  • ISO/IEC 1539-1 : 2004, Information technology – Programming Languages – Fortran, Geneva, 2004 (Fortran 2003).
  • ISO/IEC 1539-1 : 2010, Information technology – Programming Languages – Fortran, Geneva, 2010 (Fortran 2008).
  • Fortran 95 Handbook Complete ISO/ANSI Reference, Adams et al, The MIT Press, Cambridge, Mass, 1997.
  • The Fortran 2003 Handbook, Adams et al, Springer, 2009.
  • OpenMP Application Program Interface, Version 3.1, July 2011, http://www.openmp.org.
  • Programming in VAX Fortran, Version 4.0, Digital Equipment Corporation (September, 1984).
  • IBM VS Fortran, IBM Corporation, Rev. GC26-4119.
  • Military Standard, Fortran, DOD Supplement to American National Standard Programming Language Fortran, ANSI x.3-1978, MIL-STD-1753 (November 9, 1978).
  • American National Standard Programming Language C, ANSI X3.159-1989.
  • ISO/IEC 9899:1999, Information technology – Programming Languages – C, Geneva, 1999 (C99).
  • ISO/IEC 9899:2011, Information Technology – Programming Languages – C, Geneva, 2011 (C11).
  • ISO/IEC 14882:2011, Information Technology – Programming Languages – C++, Geneva, 2011 (C++11).

Organization

Users typically begin by wanting to know how to use a product and often then find that they need more information and facts about specific areas of the product. Knowing how as well as why you might use certain options or perform certain tasks is key to using the PGI compilers and tools effectively and efficiently. However, once you have this knowledge and understanding, you very likely might find yourself wanting to know much more about specific areas or specific topics.

To facilitate ease of use, this manual contains detailed reference information about specific aspects of the compiler, such as the details of compiler options, directives, and more. This guide contains these sections:

Fortran, C, and C++ Data Types describes the data types that are supported by the PGI Fortran, C, and C++ compilers.

Command-Line Options Reference provides a detailed description of each command-line option.

C++ Name Mangling describes the name mangling facility and explains the transformations of names of entities to names that include information on aspects of the entity’s type and a fully qualified name.

Directives and Pragmas Reference contains detailed descriptions of PGI’s proprietary directives and pragmas.

Runtime Environment describes the programming model supported for compiler code generation, including register conventions and calling conventions for OpenPOWER processor-based systems.

C++ Dialect Supported lists more details of the version of the C++ language that PGC++ supports.

Messages provides a list of compiler error messages.

Hardware and Software Constraints

This guide describes versions of the PGI compilers that produce assembly code forOpenPOWER processor-based systems. Details concerning environment-specific values and defaults and system-specific features or limitations are presented in the release notes delivered with the PGI compilers.

Conventions

This guide uses the following conventions:

italic
is used for emphasis.
Constant Width
is used for filenames, directories, arguments, options, examples, and for language statements in the text, including assembly language statements.
Bold
is used for commands.
[ item1 ]
in general, square brackets indicate optional items. In this case item1 is optional. In the context of p/t-sets, square brackets are required to specify a p/t-set.
{ item2 | item 3 }
braces indicate that a selection is required. In this case, you must select either item2 or item3.
filename ...
ellipsis indicate a repetition. Zero or more of the preceding item may occur. In this example, multiple filenames are allowed.
FORTRAN
Fortran language statements are shown in the text of this guide using a reduced fixed point size.
C/C++
C/C++ language statements are shown in the test of this guide using a reduced fixed point size.

The PGI compilers and tools are supported on a wide variety of Linux, macOS and Windows operating systems running on 64-bit x86-compatible processors, and on Linux running on OpenPOWER processors. (Currently, the PGI debugger is supported on x86-64/x64 only.) See the Compatibility and Installation section on the PGI website for a comprehensive listing of supported platforms.

Note: Support for 32-bit development was deprecated in PGI 2016 and is no longer available as of the PGI 2017 release. PGI 2017 is only available for 64-bit operating systems and does not include the ability to compile 32-bit applications for execution on either 32- or 64-bit operating systems.

Terms

A number of terms related to systems, processors, compilers and tools are used throughout this guide. For example:

accelerator FMA -mcmodel=small shared library
AVX host MPI SIMD
CUDA large arrays MPICH static linking
device license keys multicore  
driver LLVM NUMA  
DWARF -mcmodel=medium OpenPOWER  

For a complete definition of these terms and other terms in this guide with which you may be unfamiliar, please refer to the PGI online glossary.

The following table lists the PGI compilers and tools and their corresponding commands:

Table 1. PGI Compilers and Commands
Compiler or Tool Language or Function Command
PGFORTRAN ISO/ANSI Fortran 2003 pgfortran
PGCC ISO/ANSI C11 and K&R C pgcc
PGC++ ISO/ANSI C++14 with GNU compatibility pgc++
PGI Profiler Performance profiler pgprof

In general, the designation PGI Fortran is used to refer to the PGI Fortran 2003 compiler, and pgfortran is used to refer to the command that invokes the compiler. A similar convention is used for each of the PGI compilers and tools.

For simplicity, examples of command-line invocation of the compilers generally reference the pgfortran command, and most source code examples are written in Fortran. Usage of PGC⁠+⁠+ and PGCC is consistent with PGFORTRAN, though there are command-line options and features of these compilers that do not apply to PGFORTRAN, and vice versa.

Note: Support for 32-bit development was deprecated in PGI 2016 and is no longer available as of the PGI 2017 release. PGI 2017 is only available for 64-bit operating systems and does not include the ability to compile 32-bit applications for execution on either 32-bit or 64-bit operating systems.

1. Fortran, C, and C++ Data Types

This section describes the scalar and aggregate data types recognized by the PGI Fortran, C, and C++ compilers, the format and alignment of each type in memory, and the range of values each type can have.

1.1. Fortran Data Types

1.1.1. Fortran Scalars

A scalar data type holds a single value, such as the integer value 42 or the real value 112.6. The next table lists scalar data types, their size, format and range. Table 3 shows the range and approximate precision for Fortran real data types. Table 4 shows the alignment for different scalar data types. The alignments apply to all scalars, whether they are independent or contained in an array, a structure or a union.

Table 2. Representation of Fortran Data Types
Fortran Data Type Format Range
INTEGER 2's complement integer -231 to 231-1
INTEGER*2 2's complement integer -32768 to 32767
INTEGER*4 2's complement integer -231 to 231-1
INTEGER*8 2's complement integer -263 to 263-1
LOGICAL 32-bit value true or false
LOGICAL*1 8-bit value true or false
LOGICAL*2 16-bit value true or false
LOGICAL*4 32-bit value true or false
LOGICAL*8 64-bit value true or false
BYTE 2's complement -128 to 127
REAL Single-precision floating point 10-37 to 1038(1)
REAL*4 Single-precision floating point 10-37 to 10 38(1)
REAL*8 Double-precision floating point 10-307 to 10 308(1)
DOUBLE PRECISION Double-precision floating point 10-307 to 10308(1)
COMPLEX Single-precision floating point 10-37 to 1038(1)
DOUBLE COMPLEX Double-precision floating point 10-307 to 10308(1)
COMPLEX*16 Double-precision floating point 10-307 to 10308(1)
CHARACTER*n Sequence of n bytes  

(1) Approximate value

The logical constants .TRUE. and .FALSE. are all ones and all zeroes, respectively. Internally, the value of a logical variable is true if the least significant bit is one and false otherwise. When the option -⁠Munixlogical is set, a logical variable with a non-zero value is true and with a zero value is false.

Note: A variable of logical type may appear in an arithmetic context, and the logical type is then treated as an integer of the same size.
Table 3. Real Data Type Ranges
Data Type Binary Range Decimal Range Digits of Precision
REAL -2-126 to 2128 10-37 to 1038(1) 7–8
REAL*8 -2-1022 to 21024 10-307 to 10308(1) 15–16
Table 4. Scalar Type Alignment
This Type... ...Is aligned on this size boundary
LOGICAL*1 1-byte
LOGICAL*2 2-byte
LOGICAL*4 4-byte
LOGICAL*8 8-byte
BYTE 1-byte
INTEGER*2 2-byte
INTEGER*4 4-byte
INTEGER*8 8-byte
REAL*4 4-byte
REAL*8 8-byte
COMPLEX*8 4-byte
COMPLEX*16 8-byte

1.1.2. FORTRAN Aggregate Data Type Extensions

The PGFORTRAN compiler supports de facto standard extensions to FORTRAN that allow for aggregate data types. An aggregate data type consists of one or more scalar data type objects. You can declare the following aggregate data types:

  • An array consists of one or more elements of a single data type placed in contiguous locations from first to last.
  • A structure can contain different data types. The members are allocated in the order they appear in the definition but may not occupy contiguous locations.
  • A union is a single location that can contain any of a specified set of scalar or aggregate data types. A union can have only one value at a time. The data type of the union member to which data is assigned determines the data type of the union after that assignment.

The alignment of an array, a structure or union (an aggregate) affects how much space the object occupies and how efficiently the processor can address members. Arrays use the alignment of their members.

Array types
align according to the alignment of the array elements. For example, an array of INTEGER*2 data aligns on a 2-byte boundary.
Structures and Unions
align according to the alignment of the most restricted data type of the structure or union. In the next example, the union aligns on a 4-byte boundary since the alignment of c, the most restrictive element, is four.
STRUCTURE /astr/
UNION
 MAP
 INTEGER*2 a ! 2 bytes
 END MAP
 MAP
 BYTE b ! 1 byte
 END MAP
 MAP
 INTEGER*4 c ! 4 bytes
 END MAP
END UNION
END STRUCTURE

Structure alignment can result in unused space called padding. Padding between members of the structure is called internal padding. Padding between the last member and the end of the space is called tail padding.

The offset of a structure member from the beginning of the structure is a multiple of the member's alignment. For example, since an INTEGER*2 aligns on a 2-byte boundary, the offset of an INTEGER*2 member from the beginning of a structure is a multiple of two bytes.

1.1.3. Fortran 90 Aggregate Data Types (Derived Types)

The Fortran 90 standard added formal support for aggregate data types. The TYPE statement begins a derived type data specification or declares variables of a specified user-defined type. For example, the following would define a derived type ATTENDEE:

TYPE ATTENDEE
 CHARACTER(LEN=30) NAME
 CHARACTER(LEN=30) ORGANIZATION
 CHARACTER (LEN=30) EMAIL
END TYPE ATTENDEE

In order to declare a variable of type ATTENDEE and access the contents of such a variable, code such as the following would be used:

TYPE (ATTENDEE) ATTLIST(100)
. . .
ATTLIST(1)%NAME = ‘JOHN DOE’

1.2. C and C++ Data Types

1.2.1. C and C++ Scalars

Table 5 lists C and C++ scalar data types, providing their size and format. The alignment of a scalar data type is equal to its size. Table 6 shows scalar alignments that apply to individual scalars and to scalars that are elements of an array or members of a structure or union. Wide characters are supported (character constants prefixed with an L). The size of each wide character is 4 bytes.

Table 5. C/C++ Scalar Data Types
Data Type Size (bytes) Format Range
unsigned char 1 ordinal 0 to 255
signed char 1 2's complement integer -128 to 127
char 1 ordinal 0 to 255
unsigned short 2 ordinal 0 to 65535
[signed] short 2 2's complement integer -32768 to 32767
unsigned int 4 ordinal 0 to 232 -1
[signed] int 4 2's complement integer -231 to 231-1
[signed] long [int] 8 2's complement integer -263 to 263-1
unsigned long [int] 8 ordinal 0 to 264-1
[signed] long long [int] 8 2's complement integer -263 to 263-1
unsigned long long [int] 8 ordinal 0 to 264-1
float 4 IEEE single-precision floating-point 10-37 to 1038(1)
double 8 IEEE double-precision floating-point 10-307 to 10308(1)
long double 16 IBM double-double 10-307 to 10308(1)
bit field(2) (unsigned value) 1 to 32 bits ordinal 0 to 2size-1, where size is the number of bits in the bit field
bit field(2) (signed value) 1 to 32 bits 2's complement integer -2size-1 to 2size-1-1, where size is the number of bits in the bit field
pointer 8 address 0 to 264-1
enum 4 2's complement integer -231 to 231-1

(1) Approximate value

(2) Bit fields occupy as many bits as you assign them, up to 4 bytes, and their length need not be a multiple of 8 bits (1 byte)

Table 6. Scalar Alignment
Data Type Alignment on this size boundary
char 1-byte boundary, signed or unsigned.
short 2-byte boundary, signed or unsigned.
int 4-byte boundary, signed or unsigned.
enum 4-byte boundary.
pointer 8-byte boundary.
float 4-byte boundary.
double 8-byte boundary.
long double 16-byte boundary.
long [int] 8-byte boundary, signed or unsigned.
long long [int] 8-byte boundary, signed or unsigned.

1.2.2. C and C++ Aggregate Data Types

An aggregate data type consists of one or more scalar data type objects. You can declare the following aggregate data types:

array
consists of one or more elements of a single data type placed in contiguous locations from first to last.
class
(C++ only) is a class that defines an object and its member functions. The object can contain fundamental data types or other aggregates including other classes. The class members are allocated in the order they appear in the definition but may not occupy contiguous locations.
struct
is a structure that can contain different data types. The members are allocated in the order they appear in the definition but may not occupy contiguous locations. When a struct is defined with member functions, its alignment rules are the same as those for a class.
union
is a single location that can contain any of a specified set of scalar or aggregate data types. A union can have only one value at a time. The data type of the union member to which data is assigned determines the data type of the union after that assignment.

1.2.3. Class and Object Data Layout

Class and structure objects with no virtual entities and with no base classes, that is just direct data field members, are laid out in the same manner as C structures. The following section describes the alignment and size of these C-like structures. C++ classes (and structures as a special case of a class) are more difficult to describe. Their alignment and size is determined by compiler generated fields in addition to user-specified fields. The following paragraphs describe how storage is laid out for more general classes. The user is warned that the alignment and size of a class (or structure) is dependent on the existence and placement of direct and virtual base classes and of virtual function information. The information that follows is for informational purposes only, reflects the current implementation, and is subject to change. Do not make assumptions about the layout of complex classes or structures.

All classes are laid out in the same general way, using the following pattern (in the sequence indicated):

  • First, storage for all of the direct base classes (which implicitly includes storage for non-virtual indirect base classes as well):
    • When the direct base class is also virtual, only enough space is set aside for a pointer to the actual storage, which appears later.
    • In the case of a non-virtual direct base class, enough storage is set aside for its own non-virtual base classes, its virtual base class pointers, its own fields, and its virtual function information, but no space is allocated for its virtual base classes.
  • Next, storage for the class’s own fields.
  • Next, storage for virtual function information (typically, a pointer to a virtual function table).
  • Finally, storage for its virtual base classes, with space enough in each case for its own non-virtual base classes, virtual base class pointers, fields, and virtual function information.

1.2.4. Aggregate Alignment

The alignment of an array, a structure or union (an aggregate) affects how much space the object occupies and how efficiently the processor can address members.

Arrays
align according to the alignment of the array elements. For example, an array of short data type aligns on a 2-byte boundary.
Structures and Unions
align according to the most restrictive alignment of the enclosing members. In the following example, the union un1 aligns on a 4-byte boundary since the alignment of c, the most restrictive element, is four:
union un1 {
 short a; /* 2 bytes */
 char b; /* 1 byte */
 int c; /* 4 bytes */
 };

Structure alignment can result in unused space, called padding. Padding between members of a structure is called internal padding. Padding between the last member and the end of the space occupied by the structure is called tail padding. Figure 1 illustrates structure alignment. Consider the following structure:

struct strc1 {
 char a; /* occupies byte 0 */
 short b; /* occupies bytes 2 and 3 */
 char c; /* occupies byte 4 */
 int d; /* occupies bytes 8 through 11 */
 };
Figure 1. Internal Padding in a Structure
png for PDF.

Figure 2 shows how tail padding is applied to a structure aligned on a doubleword (8 byte) boundary.

struct strc2{
 int m1[4]; /* occupies bytes
0 through 15 */
 double m2; /* occupies bytes 16 through 23 */
 short m3; /* occupies bytes 24 and 25 */
} st;

1.2.5. Bit-field Alignment

Bit-fields have the same size and alignment rules as other aggregates, with several additions to these rules:

  • Bit-fields are allocated from right to left.
  • A bit-field must entirely reside in a storage unit appropriate for its type. Bit-fields never cross unit boundaries.
  • Bit-fields may share a storage unit with other structure/union members, including members that are not bit-fields.
  • Unnamed bit-field's types do not affect the alignment of a structure or union.
Figure 2. Tail Padding in a Structure
png for PDF.

1.2.6. Other Type Keywords in C and C++

The void data type is neither a scalar nor an aggregate. You can use void or void* as the return type of a function to indicate the function does not return a value, or as a pointer to an unspecified data type, respectively.

The const and volatile type qualifiers do not in themselves define data types, but associate attributes with other types. Use const to specify that an identifier is a constant and is not to be changed. Use volatile to prevent optimization problems with data that can be changed from outside the program, such as memory-mapped I/O buffers.

2. Command-Line Options Reference

A command-line option allows you to specify specific behavior when a program is compiled and linked. Compiler options perform a variety of functions, such as setting compiler characteristics, describing the object code to be produced, controlling the diagnostic messages emitted, and performing some preprocessor functions. Most options that are not explicitly set take the default settings. This reference section describes the syntax and operation of each compiler option. For easy reference, the options are arranged in alphabetical order.

For an overview and tips on options usage and which options are best for which tasks, refer to the ‘Using Command-line Options’ section of the PGI Compiler User's Guide, which also provides summary tables of the different options.

This section uses the following notation:

[item]
Square brackets indicate that the enclosed item is optional.
{item | item}
Braces indicate that you must select one and only one of the enclosed items. A vertical bar (|) separates the choices.
...
Horizontal ellipses indicate that zero or more instances of the preceding item are valid.

2.1. PGI Compiler Option Summary

The following tables include all the PGI compiler options that are not language-specific. The options are separated by category for easier reference.

For a complete description of each option, refer to the detailed information later in this section.

2.2. C and C++ Compiler Options

There are a large number of compiler options specific to the PGCC and PGC++ compilers, especially PGC++. The next table lists several of these options, but is not exhaustive. For a complete list of available options, including an exhaustive list of PGC++ options, use the -⁠help command-line option. For further detail on a given option, use -⁠help and specify the option explicitly. The majority of these options are related to building your program or application.

Table 11. C and C++ -specific Compiler Options
Option Description
-A (pgc++ only) Accept proposed ANSI C++, issuing errors for non-conforming code.
-a (pgc++ only) Accept proposed ANSI C++, issuing warnings for non-conforming code.
--[no_]alternative_tokens (pgc++ only) Enable/disable recognition of alternative tokens. These are tokens that make it possible to write C++ without the use of the ,, [, ], #, &, and ^ and characters. The alternative tokens include the operator keywords (e.g., and, bitand, etc.) and digraphs. The default is --⁠⁠no_alternative_tokens.
-B Allow C++ comments (using //) in C source.
--[no_]bool (pgc++ only) Enable or disable recognition of bool. The default value is --bool.
--[no_]builtin Do/don’t compile with math subroutine builtin support, which causes selected math library routines to be inlined. The default is --builtin.
--compress_names (pgc++ only) Create a precompiled header file with the name filename.
-⁠d<arg> (pgcc only) Prints additional information from the preprocessor.
--dependencies (see -⁠M) (pgc++ only) Print makefile dependencies to stdout.
--dependencies_to_file filename (pgc++ only) Print makefile dependencies to file filename.
--display_error_number (pgc++ only) Display the error message number in any diagnostic messages that are generated.
--diag_error<number> (pgc++ only) Override the normal error severity of the specified diagnostic messages.
--diag_remark<number> (pgc++ only) Override the normal error severity of the specified diagnostic messages.
--diag_suppress<number> (pgc++ only) Override the normal error severity of the specified diagnostic messages.
--diag_warning<number> (pgc++ only) Override the normal error severity of the specified diagnostic messages.
-e<number> (pgc++ only) Set the C++ front-end error limit to the specified <number>.
--no_exceptions (pgc++ only) Disable exception handling support.
--gnu_version <num> (pgc++ only) Sets the GNU C++ compatibility version.
--[no]llalign (pgc++ only) Do/don’t align longlong integers on integer boundaries. The default is --⁠⁠llalign.
-M Generate make dependence lists.
-MD Generate make dependence lists.
-MD,filename (pgc++ only) Generate make dependence lists and print them to file filename.
--optk_allow_dollar_in_id_chars (pgc++ only) Accept dollar signs in identifiers.
-P Stops after the preprocessing phase and saves the preprocessed file in filename.i.
--pch (pgc++ only) Automatically use and/or create a precompiled header file.
--preinclude=<filename> (pgc++ only) Specify file to be included at the beginning of compilation so you can set system-dependent macros, types, and so on.
--[no_]using_std (pgc++ only) Enable/disable implicit use of the std namespace when standard header files are included.
-X filename (pgc++ only) Generate cross-reference information into file filename.

2.3. Generic PGI Compiler Options

The following descriptions are for all the PGI options. For easy reference, the options are arranged in alphabetical order. For a list of options by tasks, refer to the tables in the beginning of this section.

2.3.1. -#

Displays the invocations of the compiler, assembler and linker.

Default

The compiler does not display individual phase invocations.

Usage

The following command-line requests verbose invocation information.

$ pgfortran -# prog.f

Description

The -⁠# option displays the invocations of the compiler, assembler and linker. These invocations are command-lines created by the driver from your command-line input and the default value.

2.3.2. -###

Displays the invocations of the compiler, assembler and linker, but does not execute them.

Default

The compiler does not display individual phase invocations.

Usage

The following command-line requests verbose invocation information.

$ pgfortran -### myprog.f

Description

Use the -⁠### option to display the invocations of the compiler, assembler and linker but not to execute them. These invocations are command lines created by the compiler driver from the rc files and the command-line options.

2.3.3. -acc

Enables OpenACC directives.

Default

The compiler enables OpenACC directives.

Syntax

-acc[=[no]autopar|[no]required|strict|verystrict]
[no]autopar
Enable [default] loop autoparallelization within acc parallel. The default is to autopar, that is, to enable loop autoparallelization.
[no]required
Instructs the compiler to issue a compiler error if the compute regions fail to accelerate. The default is required.
strict
Instructs the compiler to issue warnings for non-OpenACC accelerator directives.
verystrict
Instructs the compiler to fail with an error for any non-OpenACC accelerator directive.

Usage

The following command-line requests that OpenACC directives be enabled and that an error be issued for any non-OpenACC accelerator directive.

$ pgfortran -acc=verystrict -g prog.f

Description

The -⁠acc option enables OpenACC directives. You can use the suboptions to specify loop autoparallelization, how the compiler reports compute regions failures to accelerate, and whether to issue a warning or an error for non-OpenACC accelerator directives.

Starting in PGI 14.1, you control the OpenACC compiler behavior related to accelerator code generation failures with the required suboption. The OpenACC compilers now issue a compile-time error if accelerator code generation fails. In previous releases, the compiler would issue a warning, then generate code to run the compute kernel on the host. This previous behavior generates incorrect results if the compute kernels are inside a data region and the host and device memory values are inconsistent. You can enable the old behavior by using the -acc norequired switch.

2.3.4. -Bdynamic

Compiles for and links to the shared object version of the PGI runtime libraries.

Default

The compiler uses static libraries.

Usage

Description

When you use the PGI compiler flag -⁠Bdynamic to create an executable that links to the shared object form of the runtime, the executable built is smaller than one built without -⁠Bdynamic. The PGI runtime shared object(s), however, must be available on the system where the executable is run. The -⁠Bdynamic flag must be used when an executable is linked against a shared object built by the PGI compilers.

2.3.5. -Bstatic

Compiles for and links to the static version of the PGI runtime libraries.

Default

The compiler uses static libraries.

Usage

The following command line explicitly compiles for and links to the static version of the PGI runtime libraries:
% pgfortran -Bstatic -c object1.f

Description

You can use this option to explicitly compile for and link to the static version of the PGI runtime libraries.

2.3.6. -Bstatic_pgi

Linux only. Compiles for and links to the static version of the PGI runtime libraries. Implies -⁠Mnorpath.

Default

The compiler uses static libraries.

Usage

The following command line explicitly compiles for and links to the static version of the PGI runtime libraries:

% pgfortran -Bstatic -c object1.f

Description

You can use this option to explicitly compile for and link to the static version of the PGI runtime libraries.

Note: On Linux, -⁠Bstatic_pgi results in code that runs on most Linux systems without requiring a Portability package.

2.3.7. -byteswapio

Swaps the byte-order of data in unformatted Fortran data files on input/output.

Default

The compiler does not byte-swap data on input/output.

Usage

The following command-line requests that byte-swapping be performed on input/output.

$ pgfortran -byteswapio myprog.f

Description

Use the -⁠byteswapio option to swap the byte-order of data in unformatted Fortran data files on input/output. When this option is used, the order of bytes is swapped in both the data and record control words; the latter occurs in unformatted sequential files.

You can use this option to convert big-endian format data files produced by most legacy RISC workstations to the little-endian format used on x86-64/x64 or OpenPOWER systems on the fly during file reads/writes.

This option assumes that the record layouts of unformatted sequential access and direct access files are the same on the systems. It further assumes that the IEEE representation is used for floating-point numbers. In particular, the format of unformatted data files produced by PGI Fortran compilers is identical to the format used on Sun and SGI workstations; this format allows you to read and write unformatted Fortran data files produced on those platforms from a program compiled for an x86-64/x64 or OpenPOWER platform using the -⁠byteswapio option.

2.3.8. -C

(Fortran only) Generates code to check array bounds.

Default

The compiler does not enable array bounds checking.

Usage

In this example, the compiler instruments the executable produced from myprog.f to perform array bounds checking at runtime:

$ pgfortran -C myprog.f

Description

Use this option to enable array bounds checking. If an array is an assumed size array, the bounds checking only applies to the lower bound. If an array bounds violation occurs during execution, an error message describing the error is printed and the program terminates. The text of the error message includes the name of the array, the location where the error occurred (the source file and the line number in the source), and information about the out of bounds subscript (its value, its lower and upper bounds, and its dimension).

2.3.9. -c

Halts the compilation process after the assembling phase and writes the object code to a file.

Default

The compiler produces an executable file and does not use the -⁠c option.

Usage

In this example, the compiler produces the object file myprog.o in the current directory.

$ pgfortran -c myprog.f

Description

Use the -⁠c option to halt the compilation process after the assembling phase and write the object code to a file. If the input file is filename.f, the output file is filename.o.

2.3.10. -d<arg>

Prints additional information from the preprocessor. [Valid only for c (pgcc)]

Default

No additional information is printed from the preprocessor.

Syntax

-d[D|I|M|N]
-dD
Print macros and values from source files.
-dI
Print include file names.
-dM
Print macros and values, including predefined and command-line macros.
-dN
Print macro names from source files.

Usage

In the following example, the compiler prints macro names from the source file.

$ pgfortran -dN myprog.f

Description

Use the -d<arg> option to print additional information from the preprocessor.

2.3.11. -D

Creates a preprocessor macro with a given value.

Note:

You can use the -⁠D option more than once on a compiler command line. The number of active macro definitions is limited only by available memory.

Syntax

-Dname[=value]

Where name is the symbolic name and value is either an integer value or a character string.

Default

If you define a macro name without specifying a value, the preprocessor assigns the string 1 to the macro name.

Usage

In the following example, the macro PATHLENGTH has the value 256 until a subsequent compilation. If the -⁠D option is not used, PATHLENGTH is set to 128.

$ pgfortran -DPATHLENGTH=256 myprog.F

The source text in myprog.F is this:

	#ifndef PATHLENGTH
#define PATHLENGTH 128 	
#endif 	SUBROUTINE SUB 	CHARACTER*PATHLENGTH path 
	... 	
END

Description

Use the -⁠D option to create a preprocessor macro with a given value. The value must be either an integer or a character string.

You can use macros with conditional compilation to select source text during preprocessing. A macro defined in the compiler invocation remains in effect for each module on the command line, unless you remove the macro with an #undef preprocessor directive or with the -⁠U option. The compiler processes all of the -⁠U options in a command line after processing the -⁠D options.

2.3.12. -dryrun

Displays the invocations of the compiler, assembler, and linker but does not execute them.

Default

The compiler does not display individual phase invocations.

Usage

The following command line requests verbose invocation information.

$ pgfortran -dryrun myprog.f

Description

Use the -⁠dryrun option to display the invocations of the compiler, assembler, and linker but not have them executed. These invocations are command lines created by the compiler driver from the rc files and the command-line supplied with -⁠dryrun.

2.3.13. -drystdinc

Displays the standard include directories and then exits the compiler.

Default

The compiler does not display standard include directories.

Usage

The following command line requests a display for the standard include directories.

$ pgfortran -drystdinc myprog.f

Description

Use the -⁠drystdinc option to display the standard include directories and then exit the compiler.

2.3.14. -E

Halts the compilation process after the preprocessing phase and displays the preprocessed output on the standard output.

Default

The compiler produces an executable file.

Usage

In the following example the compiler displays the preprocessed myprog.f on the standard output.

$ pgfortran -E myprog.f

Description

Use the -⁠E option to halt the compilation process after the preprocessing phase and display the preprocessed output on the standard output.

2.3.15. -F

Stops compilation after the preprocessing phase.

Default

The compiler produces an executable file.

Usage

In the following example the compiler produces the preprocessed file myprog.f in the current directory.

$ pgfortran -F myprog.F

Description

Use the -⁠F option to halt the compilation process after preprocessing and write the preprocessed output to a file. If the input file is filename.F, then the output file is filename.f.

2.3.16. -fast

Enables vectorization with SIMD instructions, cache alignment, and flushz for 64-bit targets.

Default

The compiler enables vectorization with SIMD instructions, cache alignment, and flushz.

Usage

In the following example the compiler produces vector SIMD code when targeting a 64-bit machine.

$ pgfortran -fast vadd.f95

Description

When you use this option, a generally optimal set of options is chosen for targets that support SIMD capability. In addition, the appropriate -⁠tp option is automatically included to enable generation of code optimized for the type of system on which compilation is performed. This option enables vectorization with SIMD instructions, cache alignment, and flushz.

Note: C/C++ compilers enable -⁠Mautoinline with -⁠fast.

2.3.17. --flagcheck

Causes the compiler to check that flags are correct and then exit without any compilation occuring.

Default

The compiler begins a compile without the additional step to first validate that flags are correct.

Usage

In the following example the compiler checks that flags are correct, and then exits.

$ pgfortran --flagcheck myprog.f

Description

Use this option to make the compiler check that flags are correct and then exit. If flags are all correct then the compiler returns a zero status. No compilation occurs.

2.3.18. -flags

Displays valid driver options on the standard output.

Default

The compiler does not display the driver options.

Usage

In the following example the user requests information about the known switches.

$ pgfortran -flags

Description

Use this option to display driver options on the standard output. When you use this option with -⁠v, in addition to the valid options, the compiler lists options that are recognized and ignored.

2.3.19. -fpic

(Linux only) Generates position-independent code suitable for inclusion in shared object (dynamically linked library) files.

Default

The compiler does not generate position-independent code.

Usage

In the following example the resulting object file, myprog.o, can be used to generate a shared object.

$ pgfortran -fpic myprog.f

(Linux only) Use the -fpic option to generate position-independent code suitable for inclusion in shared object (dynamically linked library) files.

2.3.20. -fPIC

(Linux only) Equivalent to -⁠fpic. Provided for compatibility with other compilers.

2.3.21. -g

Instructs the compiler to include symbolic debugging information in the object module; sets the optimization level to zero unless a -⁠O option is present on the command line.

Default

The compiler does not put debugging information into the object module.

Usage

In the following example, the object file myprog.o contains symbolic debugging information.

$ pgfortran -c -g myprog.f

Description

Use the -⁠g option to instruct the compiler to include symbolic debugging information in the object module. Debuggers, including the PGI debugger, require symbolic debugging information in the object module to display and manipulate program variables and source code.

If you specify the -⁠g option on the command-line, the compiler sets the optimization level to -⁠O0 (zero), unless you specify the -⁠O option. For more information on the interaction between the -⁠g and -⁠O options, refer to the -⁠O entry. Symbolic debugging may give confusing results if an optimization level other than zero is selected.

Note:

Including symbolic debugging information increases the size of the object module.

2.3.22. -gopt

Instructs the compiler to include symbolic debugging information in the object file, and to generate optimized code identical to that generated when -⁠g is not specified.

Default

The compiler does not put debugging information into the object module.

Usage

In the following example, the object file myprog.o contains symbolic debugging information.

$ pgfortran -c -gopt myprog.f

Description

Using -⁠g alters how optimized code is generated in ways that are intended to enable or improve debugging of optimized code. The -⁠gopt option instructs the compiler to include symbolic debugging information in the object file, and to generate optimized code identical to that generated when -⁠g is not specified.

2.3.23. -help

Used with no other options, -⁠help displays options recognized by the driver on the standard output. When used in combination with one or more additional options, usage information for those options is displayed to standard output.

Default

The compiler does not display usage information.

Usage

In the following example, usage information for -⁠Minline is printed to standard output.

$ pgcc -⁠help -⁠Minline   
-Minline[=lib:<inlib>|<maxsize>|<func>|except:<func>|name:<func>|maxsize:<n>|
totalsize:<n>|smallsize:<n>|reshape]
                    Enable function inlining
    lib:<inlib>     Use extracted functions from inlib
    <maxsize>       Set maximum function size to inline
    <func>          Inline function func
    except:<func>   Do not inline function func
    name:<func>     Inline function func
    maxsize:<n>     Inline only functions smaller than n
    totalsize:<n>   Limit inlining to total size of n
    smallsize:<n>   Always inline functions smaller than n
    reshape         Allow inlining in Fortran even when array shapes do not
                    match
    -Minline        Inline all functions that were extracted

In the following example, usage information for -⁠help shows how groups of options can be listed or examined according to function.

$ pgcc -help -help 
-help[=groups|asm|debug|language|linker|opt|other|
overall|phase|prepro|suffix|switch|target|variable]

Description

Use the -⁠help option to obtain information about available options and their syntax. You can use -⁠help in one of three ways:

  • Use -⁠help with no parameters to obtain a list of all the available options with a brief one-line description of each.
  • Add a parameter to -⁠help to restrict the output to information about a specific option. The syntax for this usage is this:
    -help <command line option>
  • Add a parameter to -⁠help to restrict the output to a specific set of options or to a building process. The syntax for this usage is this:
    -help=<subgroup>

The following table lists and describes the subgroups available with -⁠help.

Table 12. Subgroups for -⁠help Option
Use this -⁠help option To get this information...
-help=asm A list of options specific to the assembly phase.
-help=debug A list of options related to debug information generation.
-help=groups A list of available switch classifications.
-help=language A list of language-specific options.
-help=linker A list of options specific to link phase.
-help=opt A list of options specific to optimization phase.
-help=other A list of other options, such as ANSI conformance pointer aliasing for C.
-help=overall A list of options generic to any PGI compiler.
-help=phase A list of build process phases and to which compiler they apply.
-help=prepro A list of options specific to the preprocessing phase.
-help=suffix A list of known file suffixes and to which phases they apply.
-help=switch A list of all known options; this is equivalent to usage of -⁠help without any parameter.
-help=target A list of options specific to target processor.
-help=variable A list of all variables and their current value. They can be redefined on the command line using syntax VAR=VALUE.

For more examples of -⁠help, refer to 'Help with Command-line Options.'

2.3.24. -I

Adds a directory to the search path for files that are included using either the INCLUDE statement or the preprocessor directive #include.

Default

The compiler searches only certain directories for included files.

  • For gcc-lib includes:/usr/lib64/gcc-lib
  • For system includes:/usr/include

Syntax

-Idirectory

Where directory is the name of the directory added to the standard search path for include files.

Usage

In the following example, the compiler first searches the directory mydir and then searches the default directories for include files.

$ pgfortran -Imydir

Description

Adds a directory to the search path for files that are included using the INCLUDE statement or the preprocessor directive #include. Use the -⁠I option to add a directory to the list of where to search for the included files. The compiler searches the directory specified by the -⁠I option before the default directories.

The Fortran INCLUDE statement directs the compiler to begin reading from another file. The compiler uses two rules to locate the file:

  • If the file name specified in the INCLUDE statement includes a path name, the compiler begins reading from the file it specifies.
  • If no path name is provided in the INCLUDE statement, the compiler searches (in order):
    1. Any directories specified using the -⁠I option (in the order specified)
    2. The directory containing the source file
    3. The current directory

    For example, the compiler applies rule (1) to the following statements:

    INCLUDE '/bob/include/file1' (absolute path name)
    INCLUDE '../../file1' (relative path name)

    and rule (2) to this statement:

    INCLUDE 'file1'

2.3.25. -i2, -⁠i4, -⁠i8

Treat INTEGER and LOGICAL variables as either two, four, or eight bytes.

Default

The compiler treats INTERGER and LOGICAL variables as four bytes.

Usage

In the following example, using the -⁠i8 switch causes the integer variables to be treated as 64 bits.

$ pgfortran -i8 int.f

int.f is a function similar to this:

int.f
     print *, "Integer size:", bit_size(i)
     end

Description

Use this option to treat INTEGER and LOGICAL variables as either two, four, or eight bytes. INTEGER*8 values not only occupy 8 bytes of storage, but operations use 64 bits, instead of 32 bits.

  • -i2: Treat INTEGER variables as 2 bytes.
  • -i4: Treat INTEGER variables as 4 bytes.
  • -i8: Treat INTEGER and LOGICAL variables as 8 bytes and use 64-bits for INTEGER*8 operations.

2.3.26. -K<flag>

Requests that the compiler provide special compilation semantics with regard to conformance to IEEE 754.

Default

The default is -⁠Knoieee and the compiler does not provide special compilation semantics.

Syntax

-K<flag>

Where flag is one of the following:

ieee Perform floating-point operations in strict conformance with the IEEE 754 standard. Some optimizations are disabled, and on some systems a more accurate math library is linked if -⁠Kieee is used during the link step.
noieee Default flag. Use the fastest available means to perform floating-point operations, link in faster non-IEEE libraries if available, and disable underflow traps.
PIC or pic (Linux only) Generate position-independent code. Equivalent to -⁠fpic. Provided for compatibility with other compilers.
trap=option

[,option]...

Controls the behavior of the processor when floating-point exceptions occur.

Possible options include:

  • fp
  • align (ignored)
  • inv
  • denorm
  • divz
  • ovf
  • unf
  • inexact

Usage

In the following example, the compiler performs floating-point operations in strict conformance with the IEEE 754 standard

$ pgfortran -Kieee myprog.f

Description

Use -⁠K to instruct the compiler to provide special compilation semantics.

-⁠Ktrap is only processed by the compilers when compiling main functions or programs. The options inv, denorm, divz, ovf, unf, and inexact correspond to the processor’s exception mask bits: invalid operation, denormalized operand, divide-by-zero, overflow, underflow, and precision, respectively.

Normally, the processor’s exception mask bits are on, meaning that floating-point exceptions are masked – the processor recovers from the exceptions and continues. If a floating-point exception occurs and its corresponding mask bit is off, or "unmasked", execution terminates with an arithmetic exception (C's SIGFPE signal).

-⁠Ktrap=fp is equivalent to -⁠Ktrap=inv,divz,ovf.

Note: The PGI compilers do not support exception-free execution for -⁠Ktrap=inexact. The purpose of this hardware support is for those who have specific uses for its execution, along with the appropriate signal handlers for handling exceptions it produces. It is not designed for normal floating point operation code support.

2.3.27. -L

Specifies a directory to search for libraries.

Note: Multiple -⁠L options are valid. However, the position of multiple -⁠L options is important relative to -⁠l options supplied.

Default

The compiler searches the standard library directory.

Syntax

-Ldirectory

Where directory is the name of the library directory.

Usage

In the following example, the library directory is /lib and the linker links in the standard libraries required by PGFORTRAN from this directory.

$ pgfortran -L/lib myprog.f

In the following example, the library directory /lib is searched for the library file libx.a and both the directories /lib and /libz are searched for liby.a.

$ pgfortran -L/lib -lx -L/libz -ly myprog.f

Description

Use the -⁠L option to specify a directory to search for libraries. Using -⁠L allows you to add directories to the search path for library files.

2.3.28. -l<library>

Instructs the linker to load the specified library. The linker searches <library>in addition to the standard libraries.

Note: The linker searches the libraries specified with -⁠l in order of appearance before searching the standard libraries.

Syntax

-llibrary

Where library is the name of the library to search.

Usage: In the following example, if the standard library directory is /lib the linker loads the library /lib/libmylib.a, in addition to the standard libraries.

$ pgfortran myprog.f -lmylib

Description

Use this option to instruct the linker to load the specified library. The compiler prepends the characters lib to the library name and adds the .a extension following the library name. The linker searches each library specified before searching the standard libraries.

2.3.29. -M

Generate make dependence lists. You can use -⁠MD,filename (pgc++ only) to generate make dependence lists and print them to the specified file.

2.3.30. -m

Displays a link map on the standard output.

Default

The compiler does display the link map and does not use the -⁠m option.

Usage

$ pgfortran -m myprog.f

Description

Use this option to display a link map. The map is written to stdout.

2.3.31. -m64

Use the 64-bit compiler for the default processor type.

Usage

When the following example is executed, pgfortran uses the 64-bit compiler for the default processor type.

$ pgfortran -m64 myprog.f

Description

Use this option to specify the 64-bit compiler as the default processor type.

2.3.32. -M<pgflag>

Selects options for code generation. The options are divided into the following categories:

Code generation Fortran Language Controls Optimization
Environment C/C++ Language Controls Miscellaneous
Inlining    

The following table lists and briefly describes the options alphabetically and includes a field showing the category. For more details about the options as they relate to these categories, refer to ‘-⁠M Options by Category’ on page 113.

Table 13. -M Options Summary
pgflag Description Category
allocatable=95|03 Controls whether to use Fortran 95 or Fortran 2003 semantics in allocatable array assignments. Fortran Language
anno Annotate the assembly code with source code. Miscellaneous
[no]autoinline When a C/C++ function is declared with the inline keyword, inline it at -⁠O2. Inlining
[no]asmkeyword Specifies whether the compiler allows the asm keyword in C/C++ source files (pgcc and pgc++ only). C/C++ Language
[no]backslash Determines how the backslash character is treated in quoted strings (Fortran only). Fortran Language
[no]bounds Specifies whether array bounds checking is enabled or disabled. Miscellaneous
--[no_]builtin Do/don't compile with math subroutine builtin support, which causes selected math library routines to be inlined (pgcc and pgc++ only). Optimization
byteswapio Swap byte-order (big-endian to little-endian or vice versa) during I/O of Fortran unformatted data. Miscellaneous
cache_align Where possible, align data objects of size greater than or equal to 16 bytes on cache-line boundaries. Optimization
chkptr Check for NULL pointers (pgf95, pgfortran only). Miscellaneous
chkstk Check the stack for available space upon entry to and before the start of a parallel region. Useful when many private variables are declared. Miscellaneous
concur Enable auto-concurrentization of loops. Multiple processors or cores will be used to execute parallelizable loops. Optimization
cpp Run the PGI cpp-like preprocessor without performing subsequent compilation steps. Miscellaneous
cray Force Cray Fortran (CF77) compatibility (Fortran only). Optimization
cuda Enables CUDA Fortran. Fortran Language
[no]daz Do/don’t treat denormalized numbers as zero. Code Generation
[no]dclchk Determines whether all program variables must be declared (Fortran only). Fortran Language
[no]defaultunit Determines how the asterisk character ("*") is treated in relation to standard input and standard output, regardless of the status of I/O units 5 and 6. (Fortran only). Fortran Language
[no]depchk Checks for potential data dependencies. Optimization
[no]dse Enables [disables] dead store elimination phase for programs making extensive use of function inlining. Optimization
[no]dlines Determines whether the compiler treats lines containing the letter "D" in column one as executable statements (Fortran only). Fortran Language
dollar,char Specifies the character to which the compiler maps the dollar sign code(Fortran only). Fortran Language
[no]dwarf Specifies not to add DWARF debug information. Code Generation
dwarf1 When used with -⁠g, generate DWARF1 format debug information. Code Generation
dwarf2 When used with -⁠g, generate DWARF2 format debug information. Code Generation
dwarf3 When used with -⁠g, generate DWARF3 format debug information. Code Generation
extend Instructs the compiler to accept 132-column source code; otherwise it accepts 72-column code (Fortran only). Fortran Language
extract invokes the function extractor. Inlining
[no]f[=option] Perform certain floating point intrinsic functions using relaxed precision. Optimization
fixed Instructs the compiler to assume FORTRAN-style fixed format source code (pgfortran only). Fortran Language
[no]flushz Do/don't set SIMD flush-to-zero mode Code Generation
[no]fpapprox Specifies not to use low-precision fp approximation operations. Optimization
free Instructs the compiler to assume F90-style free format source code(pgf95, pgfortran only). Fortran Language
func32 The compiler aligns all functions to 32-byte boundaries. Code Generation
gccbug[s] Matches behavior of certain gcc bugs Miscellaneous
info Prints informational messages regarding optimization and code generation to standard output as compilation proceeds. Miscellaneous
inform Specifies the minimum level of error severity that the compiler displays. Miscellaneous
inline Invokes the function inliner. Inlining
[no]iomutex Determines whether critical sections are generated around Fortran I/O calls(Fortran only). Fortran Language
[no]ipa Invokes interprocedural analysis and optimization. Optimization
keepasm Instructs the compiler to keep the assembly file. Miscellaneous
[no]large_arrays Enables support for 64-bit indexing and single static data objects of size larger than 2GB. Code Generation
list Specifies whether the compiler creates a listing file. Miscellaneous
[no]lre Enable [disable] loop-carried redundancy elimination. Optimization
[no]m128 Recognizes [ignores] __m128, __m128d, and __m128i datatypes. (C only) Code Generation
[no]m128 Instructs the compiler to treat floating-point constants as float data types (pgcc and pgc++ only). C/C++ Language
mpi=option Link to MPI libraries: MPICH, SGI, or Microsoft MPI libraries Code Generation
neginfo Instructs the compiler to produce information on why certain optimizations are not performed. Miscellaneous
noframe Eliminates operations that set up a true stack frame pointer for functions. Optimization
noi4 Determines how the compiler treats INTEGER variables(Fortran only). Optimization
nomain When the link step is called, don’t include the object file that calls the Fortran main program.(Fortran only). Code Generation
noopenmp When used in combination with the -⁠mp option, the compiler ignores OpenMP parallelization directives or pragmas, but still processes SGI-style parallelization directives or pragmas. Miscellaneous
norpath On Linux, do not add -⁠rpath paths to the link line. Miscellaneous
nosgimp When used in combination with the -⁠mp option, the compiler ignores SGI-style parallelization directives or pragmas, but still processes OpenMP directives or pragmas. Miscellaneous
[no]stddef Instructs the compiler to not recognize the standard preprocessor macros. Environment
nostdinc Instructs the compiler to not search the standard location for include files. Environment
nostdlib Instructs the linker to not link in the standard libraries. Environment
[no]onetrip Determines whether each DO loop executes at least once(Fortran only). Language
novintr Disable idiom recognition and generation of calls to optimized vector functions. Optimization
pfi Instrument the generated code and link in libraries for dynamic collection of profile and data information at runtime. Optimization
pre Read a pgfi.out trace file and use the information to enable or guide optimizations. Optimization
[no]pre Force [disable] generation of non-temporal moves and prefetching. Code Generation
[no]prefetch Enable [disable] generation of prefetch instructions. Optimization
preprocess Perform cpp-like preprocessing on assembly language and Fortran input source files. Miscellaneous
prof Enable Compiler feedback and modify DWARF sections. Code Generation
[no]r8 Determines whether the compiler promotes REAL variables and constants to DOUBLE PRECISION(Fortran only). Optimization
[no]r8intrinsics Determines how the compiler treats the intrinsics CMPLX and REAL(Fortran only). Optimization
[no]recursive Allocate [do not allocate] local variables on the stack; this allows recursion. SAVEd, data-initialized, or namelist members are always allocated statically, regardless of the setting of this switch(Fortran only). Code Generation
[no]reentrant Specifies whether the compiler avoids optimizations that can prevent code from being reentrant. Code Generation
[no]ref_externals Do [do not] force references to names appearing in EXTERNAL statements(Fortran only). Code Generation
safeptr Instructs the compiler to override data dependencies between pointers and arrays (pgcc and pgc++ only). Optimization
safe_lastval In the case where a scalar is used after a loop, but is not defined on every iteration of the loop, the compiler does not by default parallelize the loop. However, this option tells the compiler it is safe to parallelize the loop. For a given loop, the last value computed for all scalars make it safe to parallelize the loop. Code Generation
[no]save Determines whether the compiler assumes that all local variables are subject to the SAVE statement(Fortran only). Fortran Language
schar Specifies signed char for characters (pgcc and pgc++ only – also see uchar). C/C++ Language
[no]second_underscore Do [do not] add the second underscore to the name of a Fortran global if its name already contains an underscore(Fortran only). Code Generation
[no]signextend Do [do not] extend the sign bit, if it is set. Code Generation
[no]single Do [do not] convert float parameters to double parameter characters (pgcc and pgc++ only). C/C++ Language
[no]smartalloc[=huge| huge:<n>|hugebss] Add a call to the routine mallopt in the main routine. Supports large TLBs.
Tip: To be effective, this switch must be specified when compiling the file containing the Fortran, C, or C++ main program.
Environment
standard Causes the compiler to flag source code that does not conform to the ANSI standard(Fortran only). Fortran Language
[no]stride0 Do [do not] generate alternate code for a loop that contains an induction variable whose increment may be zero(Fortran only). Code Generation
uchar Specifies unsigned char for characters (pgcc and pgc++ only – also see schar). C/C++ Language
[no]unixlogical Determines how the compiler treats logical values.(Fortran only). Fortran Language
[no]unroll Controls loop unrolling. Optimization
[no]upcase Determines whether the compiler preserves uppercase letters in identifiers.(Fortran only). Fortran Language
varargs Forces Fortran program units to assume calls are to C functions with a varargs type interface (pgfortran only). Code Generation
[no]vect Do [do not] invoke the code vectorizer. Optimization

2.3.33. -module <moduledir>

Allows you to specify a particular directory in which generated intermediate .mod files should be placed.

Default

The compiler places .mod files in the current working directory, and searches only in the current working directory for pre-compiled intermediate .mod files.

Usage

The following command line requests that any intermediate module file produced during compilation of myprog.f be placed in the directory mymods; specifically, the file ./mymods/myprog.mod is used.

$ pgfortran -module mymods myprog.f

Description

Use the -⁠module option to specify a particular directory in which generated intermediate .mod files should be placed. If the -⁠module <moduledir> option is present, and USE statements are present in a compiled program unit, then <moduledir> is searched for .mod intermediate files prior to a search in the default local directory.

2.3.34. -mp

Instructs the compiler to interpret user-inserted OpenMP shared-memory parallel programming directives and pragmas, and to generate an executable file which will utilize multiple processors in a shared-memory parallel system.

Default

The compiler interprets user-inserted shared-memory parallel programming directives and pragmas when linking. To disable this option, use the -⁠nomp option when linking.

Usage

The following command line requests processing of any shared-memory directives present in myprog.f:

$ pgfortran -mp myprog.f

Description

Use the -⁠mp option to instruct the compiler to interpret user-inserted OpenMP shared-memory parallel programming directives and to generate an executable file which utilizes multiple processors in a shared-memory parallel system.

For a detailed description of this programming model and the associated directives and pragmas, refer to Section 9, ‘Using OpenMP’ of the PGI Compiler User's Guide.

2.3.35. -noswitcherror

Issues warnings instead of errors for unknown switches. Ignores unknown command line switches after printing a warning message.

Default

The compiler prints an error message and then halts.

Usage

In the following example, the compiler ignores unknown command line switches after printing a warning message.

$ pgfortran -noswitcherror myprog.f

Description

Use this option to instruct the compiler to ignore unknown command line switches after printing an warning message.

Tip: You can configure this behavior in the siterc file by adding: set NOSWITCHERROR=1.

2.3.36. -O<level>

Invokes code optimization at the specified level.

Default

The compiler optimizes at level 2.

Syntax

-O [level]

Where level is an integer from 0 to 4.

Usage

In the following example, since no -⁠O option is specified, the compiler sets the optimization to level 1.

$ pgfortran myprog.f

In the following example, since no optimization level is specified and a -⁠O option is specified, the compiler sets the optimization to level 2.

$ pgfortran -O myprog.f

Description

Use this option to invoke code optimization.Using the PGI compiler commands with the -⁠Olevel option (the capital O is for Optimize), you can specify any of the following optimization levels:

-O0
Level zero specifies no optimization. A basic block is generated for each language statement.
-O1
Level one specifies local optimization. Scheduling of basic blocks is performed. Register allocation is performed.
-O
When no level is specified, level two global optimizations are performed, including traditional scalar optimizations, induction recognition, and loop invariant motion. No SIMD vectorization is enabled.
-O2
Level two specifies global optimization. This level performs all level-one local optimization as well as level-two global optimization described in -⁠O. In addition, this level enables more advanced optimizations such as SIMD code generation, cache alignment, and partial redundancy elimination.
-O3
Level three specifies aggressive global optimization. This level performs all level-one and level-two optimizations and enables more aggressive hoisting and scalar replacement optimizations that may or may not be profitable.
-O4
Level four performs all level-one, level-two, and level-three optimizations and enables hoisting of guarded invariant floating point expressions.

The following table shows the interaction between the -⁠O option, -⁠g option, -⁠Mvect, and -⁠Mconcur options.

Table 14. Optimization and -⁠O, -⁠g, -⁠Mvect, and -⁠Mconcur Options
Optimize Option Debug Option -M Option Optimization Level
none none none 1
none none -Mvect 2
none none -Mconcur 2
none -g none 0
-O none or -⁠g none 2
-Olevel none or -⁠g none level
-Olevel < 2 none or -⁠g -Mvect 2
-Olevel < 2 none or -⁠g -Mconcur 2

Unoptimized code compiled using the option -⁠O0 can be significantly slower than code generated at other optimization levels. Like the -⁠Mvect option, the -⁠Munroll option sets the optimization level to level-2 if no -⁠O or -⁠g options are supplied. The -⁠gopt option is recommended for generation of debug information with optimized code. For more information on optimization, refer to the ‘Optimizing and Parallelizing’ section of the PGI Compiler User's Guide.

2.3.37. -o

Names the executable file. Use the -⁠o option to specify the filename of the compiler object file. The final output is the result of linking.

Default

The compiler creates executable filenames as needed. If you do not specify the -⁠o option, the default filename is the linker output file a.out .

Syntax

-o filename

Where filename is the name of the file for the compilation output. The filename should not have a .f extension.

Usage

In the following example, the executable file ismyprog instead of the default a.outmyprog.exe.

$ pgfortran myprog.f -o myprog

2.3.38. --pedantic

Prints warnings from included <system header files>.

Default

The compiler prints the warnings from the included system header files.

Usage

In the following example, the compiler prints the warnings from the included system header files.

$ pgc++ --power myprog.cc

2.3.39. -pg

(Linux only) Instructs the compiler to instrument the generated executable for gprof-style gmon.out sample-based profiling trace file.

Default

The compiler does not instrument the generated executable for gprof-style profiling.

Usage:

In the following example the program is compiled for profiling using pgdbg or gprof.

$ pgfortran -pg myprog.c

Description

Use this option to instruct the compiler to instrument the generated executable for gprof-style sample-based profiling. You must use this option at both the compile and link steps. A gmon.out style trace is generated when the resulting program is executed, and can be analyzed using gprof.

2.3.40. -pgc++libs

Instructs the compiler to append C⁠+⁠+ runtime libraries to the link line for programs built using PGFORTRAN.

Default

The C/C++ compilers do not append the C++ runtime libraries to the link line.

Usage

In the following example the C⁠+⁠+ runtime libraries are linked with an object file compiled with pgfortran.

$ pgfortran main.f90 mycpp.o -pgc++libs

Description

Use this option to instruct the compiler to append C⁠+⁠+ runtime libraries to the link line for programs built using PGFORTRAN.

2.3.41. -pgf90libs

Instructs the compiler to append PGF90/PGF95/PGFORTRAN runtime libraries to the link line.

Default

The C/C++ compilers do not append the PGFORTRAN runtime libraries to the link line.

Usage

In the following example a .c main program is linked with an object file compiled with pgfortran.

$ pgcc main.c myf95.o -pgf90libs

Description

Use this option to instruct the compiler to append PGFORTRAN runtime libraries to the link line.

2.3.42. -R<directory>

(Linux only) Instructs the linker to hard-code the pathname <directory>into the search path for generated shared object (dynamically linked library) files.

Note: There cannot be a space between R and <directory>.

Usage

In the following example, at runtime the a.out executable searches the specified directory, in this case /home/Joe/myso, for shared objects.

$ pgfortran -R/home/Joe/myso myprog.f

Description

Use this option to instruct the compiler to pass information to the linker to hard-code the pathname <directory> into the search path for shared object (dynamically linked library) files.

2.3.43. -r

Linux only.Creates a relocatable object file.

Default

The compiler does not create a relocatable object file and does not use the -⁠r option.

Usage

In this example, pgfortran creates a relocatable object file.

$ pgfortran -r myprog.f

Description

Use this option to create a relocatable object file.

2.3.44. -r4 and -⁠r8

Interprets DOUBLE PRECISION variables as REAL (-⁠r4), or interprets REAL variables as DOUBLE PRECISION (-⁠r8).

Usage

In this example, the double precision variables are interpreted as REAL.

$ pgfortran -r4 myprog.f

Description

Interpret DOUBLE PRECISION variables as REAL (-⁠r4) or REAL variables as DOUBLE PRECISION (-⁠r8).

2.3.45. -rc

Specifies the name of the driver startup configuration file. If the file or pathname supplied is not a full pathname, the path for the configuration file loaded is relative to the $DRIVER path (the path of the currently executing driver). If a full pathname is supplied, that file is used for the driver configuration file.

Syntax

-rc [path] filename

Where path is either a relative pathname, relative to the value of $DRIVER, or a full pathname beginning with "/". Filename is the driver configuration file.

Usage

In the following example, the file .pgfortranrctest, relative to /usr/pgi/linuxpower/bin, the value of $DRIVER, is the driver configuration file.

$ pgfortran -rc .pgfortranrctest myprog.f

Description

Use this option to specify the name of the driver startup configuration file. If the file or pathname supplied is not a full pathname, the path for the configuration file loaded is relative to the $DRIVER path – the path of the currently executing driver. If a full pathname is supplied, that file is used for the driver configuration file.

2.3.46. -s

(Linux only) Strips the symbol-table information from the executable file.

Default

The compiler includes all symbol-table information and does not use the -⁠s option.

Usage

In this example, pgfortran strips symbol-table information from the a.out. executable file.

$ pgfortran -s myprog.f

Description

Use this option to strip the symbol-table information from the executable.

2.3.47. -S

Stops compilation after the compiling phase and writes the assembly-language output to a file.

Default

The compiler does not retain a .s file.

Usage

In this example, pgfortran produces the file myprog.s in the current directory.

$ pgfortran -S myprog.f

Description

Use this option to stop compilation after the compiling phase and then write the assembly-language output to a file. If the input file is filename.f, then the output file is filename.s.

2.3.48. -shared

(Linux only) Instructs the compiler to pass information to the linker to produce a shared object (dynamically linked library) file.

Default

The compiler does not pass information to the linker to produce a shared object file.

Usage

In the following example the compiler passes information to the linker to produce the shared object file:myso.so.

$ pgfortran -shared myprog.f -o myso.so

Description

Use this option to instruct the compiler to pass information to the linker to produce a shared object (dynamically linked library) file.

2.3.49. -show

Produces driver help information describing the current driver configuration.

Default

The compiler does not show driver help information.

Usage

In the following example, the driver displays configuration information to the standard output after processing the driver configuration file.

$ pgfortran -show myprog.f

Description

Use this option to produce driver help information describing the current driver configuration.

2.3.50. -silent

Do not print warning messages.

Default

The compiler prints warning messages.

Usage

In the following example, the driver does not display warning messages.

$ pgfortran -silent myprog.f

Description

Use this option to suppress warning messages.

2.3.51. -soname

(Linux only) The compiler recognizes the -⁠soname option and passes it through to the linker.

Default

The compiler does not recognize the -⁠soname option.

Usage

In the following example, the driver passes the soname option and its argument through to the linker.

$ pgfortran -soname library.so myprog.f

Description

Use this option to instruct the compiler to recognize the -⁠soname option and pass it through to the linker.

2.3.52. -ta=tesla(tesla_suboptions),host

Defines the target accelerator and the type of code to generate. This flag is valid for Fortran, C, and C++ on supported platforms.

Note: There are three major suboptions:
  • tesla(:tesla_suboptions)
  • host
  • multicore

Default

The compiler uses -ta=tesla,host.

Usage

In the following example, tesla is the accelerator target architecture and the accelerator generates code for compute capability 3.0.

$ pgfortran -ta=tesla,cc30

Description

Use this option to select the accelerator target and, optionally, to define the type of code to genertate.

The -ta flag has the following options:

tesla
Select the tesla accelerator target. This option has the following tesla-suboptions:
cc30
Generate code for compute capability 3.0.
cc35
Generate code for compute capability 3.5.
cc3x
Generate code for the lowest 3.x compute capability possible.
cc3+
Is equivalent to cc3x.
[no]debug
Enable[disable] debug information generation in device code.
fastmath
Use routines from the fast math library.
[no]flushz
Enable[disable] flush-to-zero mode for floating point computations in the GPU code generated forPGI Accelerator model compute regions.
keep
Keep the kernel files.
kepler
is equivalent to cc3x.
kepler+
is equivalent to cc3+.
llvm
Generate code using the llvm-based back-end.
[no]debug
Enable[disable] GPU debug information generation.
deepcopy
Enable full deep copy of aggregate data structions in OpenACC; Fortran only.
[no]lineinfo
Enable[disable] GPU line information generation.
maxregcount:n
Specify the maximum number of registers to use on the GPU. Leaving this blank indicates no limit.
[no]fma
Do not generate fused multiply-add instructions.
noL1
Prevents the use of L1 hardware data cache to cache global variables.
pin+
is equivalent to cc3+.
[no]rdc
Generate [do not generate] relocatable device code.
[no]required
Generate [do not generate] a compiler error if accelerator device code cannot be generated.
tesla
is equivalent to -ta=tesla,cc2+
host
Use the host option to generate code to execute OpenACC regions on the host.

The -ta=host flag has no suboptions.

multicore
Use the multicore option to generate OpenACC parallel regions to execute in parallel on individual host cores.

The -ta=multicore flag has no suboptions.

Multiple Targets

When host is one of the multiple targets, such as -⁠ta=tesla,host, the result is generated code that can be run with or without an attached accelerator.

Relocatable Device Code

A rdc option is available for the -⁠ta and -⁠Mcuda flags that specifies to generate relocatable device code. Starting in PGI 14.1, the default code generation and linking mode for NVIDIA-target OpenACC and CUDA Fortran is rdc, relocatable device code.

You can disable the default and enable the old behavior and non-relocatable code by specifying any of the following: -⁠ta=tesla:nordc, -⁠Mcuda=nordc.

LLVM and Native GPU Code Generation

For accelerator code generation, PGI 2017 has two options.

  • The compilers generate an LLVM-based intermediate representation by default.
  • In legacy mode, the compilers generate low-level CUDA C code. To enable this code generation, use -⁠ta=tesla:nollvm on NVIDIA Tesla hardware.

DWARF Debugging Formats

PGI's debugging capability for Tesla uses the LLVM back-end. Use the compiler's -⁠g option to enable the generation of full dwarf information on both the host and device; in the absence of other optimization flags, -⁠g sets the optimization level to zero. If a -⁠O option raises the optimization level to one or higher, only GPU line information is generated on the device even when -⁠g is specified. To enforce full dwarf generation for device code at optimization levels above zero, use the debug suboption to -⁠ta=tesla. Conversely, to prevent the generation of dwarf information for device code, use the nodebug suboption to -⁠ta=tesla. Both debug and nodebug can be used independently of -⁠g.

2.3.53. -time

Print execution times for various compilation steps.

Default

The compiler does not print execution times for compilation steps.

Usage

In the following example, pgfortran prints the execution times for the various compilation steps.

$ pgfortran -time myprog.f

Description

Use this option to print execution times for various compilation steps.

2.3.54. -u

Initializes the symbol-table with <symbol>, which is undefined for the linker. An undefined symbol triggers loading of the first member of an archive library.

Default

The compiler does not use the -⁠u option.

Syntax

-usymbol

Where symbol is a symbolic name.

Usage

In this example, pgfortran initializes symbol-table with test.

$ pgfortran -utest myprog.f

Description

Use this option to initialize the symbol-table with <symbol>, which is undefined for the linker. An undefined symbol triggers loading of the first member of an archive library.

2.3.55. -U

Undefines a preprocessor macro.

Syntax

-Usymbol

Where symbol is a symbolic name.

Usage

The following examples undefine the macro test.

$ pgfortran -Utest myprog.F
$ pgfortran -Dtest -Utest myprog.F

Description

Use this option to undefine a preprocessor macro. You can also use the #undef pre-processor directive to undefine macros.

2.3.56. -V[release_number]

Displays additional information, including version messages. Further, if a release_number is appended, the compiler driver attempts to compile using the specified release instead of the default release.

Note: There can be no space between -V and release_number.

Default

The compiler does not display version information and uses the release specified by your path to compile.

Usage

The following command-line shows the output using the -⁠V option.

% pgfortran -V myprog.f

The following command-line causes pgcc to compile using the 5.2 release instead of the default release.

% pgcc -V5.2 myprog.c

Description

Use this option to display additional information, including version messages or, if a release_number is appended, to instruct the compiler driver to attempt to compile using the specified release instead of the default release.

The specified release must be co-installed with the default release, and must have a release number greater than or equal to 4.1, which was the first release that supported this functionality.

2.3.57. -v

Displays the invocations of the compiler, assembler, and linker.

Default

The compiler does not display individual phase invocations.

Usage

In the following example you use -⁠v to see the commands sent to compiler tools, assembler, and linker.

$ pgfortran -v myprog.f90

Description

Use the -⁠v option to display the invocations of the compiler, assembler, and linker. These invocations are command lines created by the compiler driver from the files and the -⁠W options you specify on the compiler command-line.

2.3.58. -W

Passes arguments to a specific phase.

Syntax

-W{0 | a | l },option[,option...]
Note: You cannot have a space between the -⁠W and the single-letter pass identifier, between the identifier and the comma, or between the comma and the option.
0
(the number zero) specifies the compiler.
a
specifies the assembler.
l
(lowercase letter l) specifies the linker.
option
is a string that is passed to and interpreted by the compiler, assembler or linker. Options separated by commas are passed as separate command line arguments.

Usage

In the following example the linker loads the text segment at address 0xffc00000 and the data segment at address 0xffe00000.

$ pgfortran -Wl,-k,-t,0xffc00000,-d,0xffe00000 myprog.f

Description

Use this option to pass arguments to a specific phase. You can use the -⁠W option to specify options for the assembler, compiler, or linker.

A given PGI compiler command invokes the compiler driver, which parses the command-line, and generates the appropriate commands for the compiler, assembler, and linker.

2.3.59. -w

Do not print warning messages.

Default

The compiler prints warning messages.

Usage

In the following example no warning messages are printed.

$ pgfortran -w myprog.f

Description

Use the -⁠w option to not print warning messages. Sometimes the compiler issues many warning in which you may have no interest. You can use this option to not issue those warnings.

2.3.60. -Xs

Use legacy standard mode for C and C++.

Default

None.

Usage

In the following example the compiler uses legacy standard mode.

$ pgcc -Xs myprog.c

Description

Use this option to use legacy standard mode for C and C++. Further, this option implies -alias=traditional.

2.3.61. -Xt

Use legacy transitional mode for C and C++.

Default

None.

Usage

In the following example the compiler uses legacy transitional mode.

$ pgcc -Xt myprog.c

Description

Use this option to use legacy transitional mode for C and C++. Further, this option implies -alias=traditional.

2.3.62. -Xlinker

Pass options to the linker.

Syntax

-Xlinker option[,option...]

Default

None.

Usage

In the following example the option --trace-symbol=foo is passed to the linker, which will cause the Linux linker to list all the files that reference symbol foo.

$ pgcc -Xliker --trace-symbol=foo myprog.c

Description

Use this option pass options to the linker. This is useful when the link step needs to be customized but the compiler doesn't understand the necessary linker options. The options supported by the linker are platform dependent and are not listed here. This option has the same effect as -Wl.

2.4. C and C++ -specific Compiler Options

There are a large number of compiler options specific to the PGCC and PGC++ compilers, especially PGC++. This section provides the details of several of these options, but is not exhaustive. For a complete list of available options, including an exhaustive list of PGC++ options, use the -⁠help command-line option. For further detail on a given option, use -⁠help and specify the option explicitly

2.4.1. -A

(pgc++ only) Instructs the PGC++ compiler to accept code conforming to the ISO C++ standard, issuing errors for non-conforming code.

Default

By default, the compiler accepts code conforming to the standard C++ Annotated Reference Manual.

Usage

The following command-line requests ISO conforming C++.

	$ pgc++ -A hello.cc

Description

Use this option to instruct the PGC++ compiler to accept code conforming to the ISO C++ standard and to issues errors for non-conforming code.

2.4.2. -a

(pgc++ only) Instructs the PGC++ compiler to accept code conforming to the ISO C++ standard, issuing warnings for non-conforming code.

Default

By default, the compiler accepts code conforming to the standard C++ Annotated Reference Manual.

Usage

The following command-line requests ISO conforming C++, issuing warnings for non-conforming code.

$ pgc++ -a hello.cc

Description

Use this option to instruct the PGC++ compiler to accept code conforming to the ISO C++ standard and to issues warnings for non-conforming code.

2.4.3. -alias

select optimizations based on type-based pointer alias rules in C and C++.

Syntax

-alias=[ansi|traditional]

Default

None.

Usage

The following command-line enables optimizations.

   $ pgc++ -alias=ansi hello.cc

Description

Use this option to select optimizations based on type-based pointer alias rules in C and C++.

ansi
Enable optimizations using ANSI C type-based pointer disambiguation
traditional
Disable type-based pointer disambiguation

2.4.4. --[no_]alternative_tokens

(pgc++ only) Enables or disables recognition of alternative tokens. These are tokens that make it possible to write C++ without the use of the comma (,) , [, ], #, &, ^, and characters. The alternative tokens include the operator keywords (e.g., and, bitand, etc.) and digraphs.

Default

The default behavior is --no_alternative_tokens, that is, to disable recognition of alternative tokens.

Usage

The following command-line enables alternative token recognition.

	$ pgc++ --alternative_tokens hello.cc

(pgc++ only) Use this option to enable or disable recognition of alternative tokens. These tokens make it possible to write C++ without the use of the comma (,), [, ], #, &, ^, and characters. The alternative tokens include digraphs and the operator keywords, such as and, bitand, and so on. The default behavior is disabled recognition of alternative tokens: --no_alternative_tokens.

2.4.5. -B

(pgcc and pgc++ only) Enables use of C++ style comments starting with // in C program units.

Default

The PGCC ANSI and K&R C compiler does not allow C++ style comments.

Usage

In the following example the compiler accepts C++ style comments.

	$ pgcc -B myprog.cc

Description

Use this option to enable use of C++ style comments starting with // in C program units.

2.4.6. -b

(pgc++ only) Enables compilation of C++ with cfront 2.1 compatibility and acceptance of anachronisms.

Default

The compiler does not accept cfront language constructs that are not part of the C++ language definition.

Usage

In the following example the compiler accepts cfront constructs.

	$ pgc++ -b myprog.cc

Description

Use this option to enable compilation of C++ with cfront 2.1 compatibility. The compiler then accepts language constructs that, while not part of the C++ language definition, are accepted by the AT&T C++ Language System (cfront release 2.1).

This option also enables acceptance of anachronisms.

2.4.7. -b3

(pgc++ only) Enables compilation of C++ with cfront 3.0 compatibility and acceptance of anachronisms.

Default

The compiler does not accept cfront language constructs that are not part of the C++ language definition.

Usage

In the following example, the compiler accepts cfront constructs.

	$ pgc++ -b3 myprog.cc

Description

Use this option to enable compilation of C++ with cfront 3.0 compatibility. The compiler then accepts language constructs that, while not part of the C++ language definition, are accepted by the AT&T C++ Language System (cfront release 3.0).

This option also enables acceptance of anachronisms.

2.4.8. --[no_]bool

(pgc++ only) Enables or disables recognition of bool.

Default

The compile recognizes bool: --bool.

Usage

In the following example, the compiler does not recognize bool.

	$ pgc++ --no_bool myprog.cc

Description

Use this option to enable or disable recognition of bool.

2.4.9. --[no_]builtin

Compile with or without math subroutine builtin support.

Default

The default is to compile with math subroutine support: --builtin.

Usage

In the following example, the compiler does not build with math subroutine support.

   $ pgc++ --no_builtin myprog.cc

Description

Use this option to enable or disable compiling with math subroutine builtin support. When you compile with math subroutine builtin support, the selected math library routines are inlined.

2.4.10. --cfront_2.1

(pgc++ only) Enables compilation of C++ with cfront 2.1 compatibility and acceptance of anachronisms.

Default

The compiler does not accept cfront language constructs that are not part of the C++ language definition.

Usage

In the following example, the compiler accepts cfront constructs.

	$ pgc++ --cfront_2.1 myprog.cc

Description

Use this option to enable compilation of C++ with cfront 2.1 compatibility. The compiler then accepts language constructs that, while not part of the C++ language definition, are accepted by the AT&T C++ Language System (cfront release 2.1).

This option also enables acceptance of anachronisms.

2.4.11. --cfront_3.0

(pgc++ only) Enables compilation of C++ with cfront 3.0 compatibility and acceptance of anachronisms.

Default

The compiler does not accept cfront language constructs that are not part of the C++ language definition.

Usage

In the following example, the compiler accepts cfront constructs.

	$ pgc++ --cfront_3.0 myprog.cc

Description

Use this option to enable compilation of C++ with cfront 3.0 compatibility. The compiler then accepts language constructs that, while not part of the C++ language definition, are accepted by the AT&T C++ Language System (cfront release 3.0).

This option also enables acceptance of anachronisms.

2.4.12. --[no_]compress_names

Compresses long function names in the file.

Default

The compiler does not compress names: --no_compress_names.

Usage

In the following example, the compiler compresses long function names.

	$ pgc++ --ccmpress_names myprog.cc

Description

Use this option to specify to compress long function names. Highly nested template parameters can cause very long function names. These long names can cause problems for older assemblers. Users encountering these problems should compile all C++ code, including library code with --compress_names. Libraries supplied by PGI work with --compress_names.

2.4.13. --create_pch filename

(pgc++ only) If other conditions are satisfied, create a precompiled header file with the specified name.

Note:

If --pch (automatic PCH mode) appears on the command line following this option, its effect is erased.

Default

The compiler does not create a precompiled header file.

Usage

In the following example, the compiler creates a precompiled header file, hdr1.

	$ pgc++ --create_pch hdr1 myprog.cc

Description

If other conditions are satisfied, use this option to create a precompiled header file with the specified name.

2.4.14. --diag_error <number>

(pgc++ only) Overrides the normal error severity of the specified diagnostic messages.

Default

The compiler does not override normal error severity.

Description

Use this option to override the normal error severity of the specified diagnostic messages. The message(s) may be specified using a mnemonic error tag or using an error number.

2.4.15. --diag_remark <number>

(pgc++ only) Overrides the normal error severity of the specified diagnostic messages.

Default

The compiler does not override normal error severity.

Description

Use this option to override the normal error severity of the specified diagnostic messages. The message(s) may be specified using a mnemonic error tag or using an error number.

2.4.16. --diag_suppress <number>

(pgc++ only) Overrides the normal error severity of the specified diagnostic messages.

Default

The compiler does not override normal error severity.

Usage

In the following example, the compiler overrides the normal error severity of the specified diagnostic messages.

	$ pgc++ --diag_suppress error_tag prog.cc

Description

Use this option to override the normal error severity of the specified diagnostic messages. The message(s) may be specified using a mnemonic error tag or using an error number.

2.4.17. --diag_warning <number>

(pgc++ only) Overrides the normal error severity of the specified diagnostic messages.

Default

The compiler does not override normal error severity.

Usage

In the following example, the compiler overrides the normal error severity of the specified diagnostic messages.

	$ pgc++ --diag_suppress an_error_tag myprog.cc

Description

Use this option to override the normal error severity of the specified diagnostic messages. The message(s) may be specified using a mnemonic error tag or using an error number.

2.4.18. --display_error_number

(pgc++ only) Displays the error message number in any diagnostic messages that are generated. The option may be used to determine the error number to be used when overriding the severity of a diagnostic message.

Default

The compiler does not display error message numbers for generated diagnostic messages.

Usage

In the following example, the compiler displays the error message number for any generated diagnostic messages.

	$ pgc++ --display_error_number myprog.cc

Description

Use this option to display the error message number in any diagnostic messages that are generated. You can use this option to determine the error number to be used when overriding the severity of a diagnostic message.

2.4.19. -e<number>

(pgc++ only) Set the C++ front-end error limit to the specified <number>.

2.4.20. --no_exceptions

(pgc++ only) Disables exception handling support.

Default

Exception handling support is enabled.

Usage

In the following example, the compiler does not provide exception handling support.

	$ pgc++ --no_exceptions myprog.cc

Description

Use this option to disable exception handling support. When exception handling is turned off, any try/catch blocks or throw expressions in the code will result in a compilation error, and any exception specifications will be ignored.

2.4.21. --gnu_version <num>

(pgc++ only) Sets the GNU C++ compatibility version.

Default

The compiler uses the latest version.

Usage

In the following example, the compiler sets the GNU version to 4.3.4.

    $ pgc++ --gnu_version 4.3.4 myprog.cc

Description

Use this option to set the GNU C++ compatibility version to use when you compile.

2.4.22. --[no]llalign

(pgc++ only) Enables or disables alignment of long long integers on long long boundaries.

Default

The compiler aligns long long integers on long long boundaries: --llalign.

Usage

In the following example, the compiler does not align long long integers on long long boundaries.

	$ pgc++ --nollalign myprog.cc

Description

Use this option to allow enable or disable alignment of long long integers on long long boundaries.

2.4.23. -M

Generates a list of make dependencies and prints them to stdout.

Note:

The compilation stops after the preprocessing phase.

Default

The compiler does not generate a list of make dependencies.

Usage

In the following example, the compiler generates a list of make dependencies.

	$ pgc++ -M myprog.cc

Description

Use this option to generate a list of make dependencies and print them to stdout.

2.4.24. -MD

Generates a list of make dependencies and prints them to a file.

Default

The compiler does not generate a list of make dependencies.

Usage

In the following example, the compiler generates a list of make dependencies and prints them to the file myprog.d.

	$ pgc++ -MD myprog.cc

Description

Use this option to generate a list of make dependencies and print them to a file. The name of the file is determined by the name of the file under compilation.dependencies_file<file>.

2.4.25. --optk_allow_dollar_in_id_chars

(pgc++ only) Accepts dollar signs ($) in identifiers.

Default

The compiler does not accept dollar signs ($) in identifiers.

Usage

In the following example, the compiler allows dollar signs ($) in identifiers.

	$ pgc++ -optk_allow_dollar_in_id_chars myprog.cc

Description

Use this option to instruct the compiler to accept dollar signs ($) in identifiers.

2.4.26. -P

Halts the compilation process after preprocessing and writes the preprocessed output to a file.

Default

The compiler produces an executable file.

Usage

In the following example, the compiler produces the preprocessed file myprog.i in the current directory.

	$ pgc++ -P myprog.cc

Description

Use this option to halt the compilation process after preprocessing and write the preprocessed output to a file. If the input file is filename.c or filename.cc., then the output file is filename.i.

2.4.27. -+p

(pgc++ only) Disallow all anachronistic constructs.

Default

The compiler disallows all anachronistic constructs.

Usage

In the following example, the compiler disallows all anachronistic constructs.

	$ pgc++ -+p myprog.cc

Description

Use this option to disallow all anachronistic constructs.

2.4.28. --pch

(pgc++ only) Automatically use and/or create a precompiled header file.

Note:

If --use_pch or --create_pch (manual PCH mode) appears on the command line following this option, this option has no effect.

Default

The compiler does not automatically use or create a precompiled header file.

Usage

In the following example, the compiler automatically uses a precompiled header file.

	$ pgc++ --pch myprog.cc

Description

Use this option to automatically use and/or create a precompiled header file.

2.4.29. --pch_dir directoryname

(pgc++ only) Specifies the directory in which to search for and/or create a precompiled header file.

The compiler searches your PATH for precompiled header files / use or create a precompiled header file.

Usage

In the following example, the compiler searches in the directory myhdrdir for a precompiled header file.

	$ pgc++ --pch_dir myhdrdir myprog.cc

Description

Use this option to specify the directory in which to search for and/or create a precompiled header file. You may use this option with automatic PCH mode (-⁠-⁠pch) or manual PCH mode (-⁠-⁠create_pch or -⁠-⁠use_pch).

2.4.30. --[no_]pch_messages

(pgc++ only) Enables or disables the display of a message indicating that the current compilation used or created a precompiled header file.

The compiler displays a message when it uses or creates a precompiled header file.

In the following example, no message is displayed when the precompiled header file located in myhdrdir is used in the compilation.

	$ pgc++ --pch_dir myhdrdir --no_pch_messages myprog.cc

Description

Use this option to enable or disable the display of a message indicating that the current compilation used or created a precompiled header file.

2.4.31. --preinclude=<filename>

(pgc++ only) Specifies the name of a file to be included at the beginning of the compilation.

In the following example, the compiler includes the file incl_file.c at the beginning of the compilation. me

	$ pgc++ --preinclude=incl_file.c myprog.cc

Description

Use this option to specify the name of a file to be included at the beginning of the compilation. For example, you can use this option to set system-dependent macros and types.

2.4.32. --use_pch filename

(pgc++ only) Uses a precompiled header file of the specified name as part of the current compilation.

Note:

If --pch (automatic PCH mode) appears on the command line following this option, its effect is erased.

Default

The compiler does not use a precompiled header file.

In the following example, the compiler uses the precompiled header file, hdr1 as part of the current compilation.

	$ pgc++ --use_pch hdr1 myprog.cc

Use a precompiled header file of the specified name as part of the current compilation. If --pch (automatic PCH mode) appears on the command line following this option, its effect is erased.

2.4.33. --[no_]using_std

(pgc++ only) Enables or disables implicit use of the std namespace when standard header files are included.

Default

The compiler uses std namespace when standard header files are included: --using_std.

Usage

The following command-line disables implicit use of the std namespace:

	$ pgc++ --no_using_std hello.cc

Description

Use this option to enable or disable implicit use of the std namespace when standard header files are included in the compilation.

2.4.34. -Xfilename

(pgc++ only) Generates cross-reference information and places output in the specified file.

Syntax:

-Xfoo

where foo is the specified file for the cross reference information.

Default

The compiler does not generate cross-reference information.

Usage

In the following example, the compiler generates cross-reference information, placing it in the file:xreffile.

	$ pgc++ -Xxreffile myprog.cc

Description

Use this option to generate cross-reference information and place output in the specified file. This is an EDG option.

2.5. -M Options by Category

This section describes each of the options available with -⁠M by the categories:

Code Generation Fortran Language Controls Optimization Environment
C/C++ Language Controls Inlining Miscellaneous  

The following sections provide detailed descriptions of several, but not all, of the -⁠M<pgflag> options. For a complete alphabetical list of all the options, refer to Table 13. These options are grouped according to categories and are listed with exact syntax, defaults, and notes concerning similar or related options.

For the latest information and description of a given option, or to see all available options, use the -⁠help command-line option, described in -help.

2.5.1. Code Generation Controls

This section describes the -⁠M<pgflag> options that control code generation.

Default: For arguments that you do not specify, the default code generation controls are these:

nodaz norecursive nosecond_underscore
noflushz noreentrant nostride0
largeaddressaware noref_externals signextend

Related options:-⁠D, -⁠I, -⁠L, -⁠l, -⁠U.

The following list provides the syntax for each -⁠M<pgflag> option that controls code generation. Each option has a description and, if appropriate, any related options.

-Mdaz
Set IEEE denormalized input values to zero; there is a performance benefit but misleading results can occur, such as when dividing a small normalized number by a denormalized number.
To take effect, this option must be set for the main program.
-Mnodaz
Do not treat denormalized numbers as zero.
To take effect, this option must be set for the main program.
-Mnodwarf
Specifies not to add DWARF debug information.
To take effect, this option must be used in combination with -⁠g.
-Mdwarf1
Generate DWARF1 format debug information.
To take effect, this option must be used in combination with -⁠g.
-Mdwarf2
Generate DWARF2 format debug information.
To take effect, this option must be used in combination with -⁠g.
-Mdwarf3
Generate DWARF3 format debug information.
To take effect, this option must be used in combination with -⁠g.
-Mflushz
Set SIMD flush-to-zero mode; if a floating-point underflow occurs, the value is set to zero.
To take effect, this option must be set for the main program.
-Mnoflushz
Do not set SIMD flush-to-zero mode; generate underflows.
To take effect, this option must be set for the main program.
-Mfunc32
Align functions on 32-byte boundaries.
-Mnomain
Instructs the compiler not to include the object file that calls the Fortran main program as part of the link step. This option is useful for linking programs in which the main program is written in C/C++ and one or more subroutines are written in Fortran (Fortran only).
-M[no]movnt
Instructs the compiler to generate nontemporal move and prefetch instructions even in cases where the compiler cannot determine statically at compile-time that these instructions will be beneficial.
-M[no]pre
enables [disables] partial redundancy elimination.
-Mprof[=option[,option,...]]
Set performance profiling options. Use of these options changes which sections are included in the binary. These sections can be read by the PGI profiler.
The option argument can be any of the following:
[no]ccff
Enable [disable] common compiler feedback format, CCFF, information.
dwarf
Add limited DWARF symbol information sufficient for most performance profilers.
-Mrecursive
instructs the compiler to allow Fortran subprograms to be called recursively.
-Mnorecursive
Fortran subprograms may not be called recursively.
-Mref_externals
force references to names appearing in EXTERNAL statements (Fortran only).
-Mnoref_externals
do not force references to names appearing in EXTERNAL statements (Fortran only).
-Mreentrant
instructs the compiler to avoid optimizations that can prevent code from being reentrant.
-Mnoreentrant
instructs the compiler not to avoid optimizations that can prevent code from being reentrant.
-Msecond_underscore
instructs the compiler to add a second underscore to the name of a Fortran global symbol if its name already contains an underscore. This option is useful for maintaining compatibility with object code compiled using pgfortran, which uses this convention by default (Fortran only).
-Mnosecond_underscore
instructs the compiler not to add a second underscore to the name of a Fortran global symbol if its name already contains an underscore (Fortran only).
-Msafe_lastval
When a scalar is used after a loop, but is not defined on every iteration of the loop, the compiler does not by default parallelize the loop. However, this option tells the compiler it’s safe to parallelize the loop. For a given loop, the last value computed for all scalars makes it safe to parallelize the loop.
-Msignextend
instructs the compiler to extend the sign bit that is set as a result of converting an object of one data type to an object of a larger signed data type.
-Mnosignextend
instructs the compiler not to extend the sign bit that is set as the result of converting an object of one data type to an object of a larger data type.
-Mstride0
instructs the compiler to inhibit certain optimizations and to allow for stride 0 array references. This option may degrade performance and should only be used if zero-stride induction variables are possible.
-Mnostride0
instructs the compiler to perform certain optimizations and to disallow for stride 0 array references.
-Mvarargs
force Fortran program units to assume procedure calls are to C functions with a varargs-type interface ( pgfortran only).

2.5.2. C/C++ Language Controls

This section describes the -⁠M<pgflag> options that affect C/C++ language interpretations by the PGI C and C++ compilers. These options are only valid to the pgcc and pgc++ compiler drivers.

Default: For arguments that you do not specify, the defaults are as follows:

noasmkeyword nosingle
dollar,_ schar

Usage:

In this example, the compiler allows the asm keyword in the source file.

	$ pgcc -Masmkeyword myprog.c

In the following example, the compiler maps the dollar sign to the dot character.

	$ pgcc -Mdollar,. myprog.c

In the following example, the compiler treats floating-point constants as float values.

	$ pgcc -Mfcon myprog.c

In the following example, the compiler does not convert float parameters to double parameters.

	$ pgcc -Msingle myprog.c

Without -⁠Muchar or with -⁠Mschar, the variable ch is a signed character:

	char ch;
	signed char sch;

If -⁠Muchar is specified on the command line:

	$ pgcc -Muchar myprog.c

char ch in the preceding declaration is equivalent to:

 unsigned char ch;

The following list provides the syntax for each -⁠M<pgflag> option that controls code generation in C/C++. Each option has a description and, if appropriate, any related options.

-Masmkeyword
instructs the compiler to allow the asm keyword in C source files. The syntax of the asm statement is as follows:
asm("statement");
Where statement is a legal assembly-language statement. The quote marks are required.
-Mnoasmkeyword
instructs the compiler not to allow the asm keyword in C source files. If you use this option and your program includes the asm keyword, unresolved references are generated
-Mdollar,char
char specifies the character to which the compiler maps the dollar sign ($). The PGCC compiler allows the dollar sign in names; ANSI C does not allow the dollar sign in names.
-M[no]eh_frame
instructs the linker to keep eh_frame call frame sections in the executable.
Note: The eh_frame option is available only on newer Linux systems that supply the system unwind libraries.
-Mfcon
instructs the compiler to treat floating-point constants as float data types, instead of double data types. This option can improve the performance of single-precision code.
-M[no]m128
instructs the compiler to recognize [ignore] __m128, __m128d, and __m128i datatypes. floating-point constants as float data types, instead of double data types. This option can improve the performance of single-precision code.
-Mschar
specifies signed char characters. The compiler treats "plain" char declarations as signed char.
-Msingle
do not to convert float parameters to double parameters in non-prototyped functions. This option can result in faster code if your program uses only float parameters. However, since ANSI C specifies that routines must convert float parameters to double parameters in non-prototyped functions, this option results in non-ANSI conformant code.
-Mnosingle
instructs the compiler to convert float parameters to double parameters in non-prototyped functions.
-Muchar
instructs the compiler to treat "plain" char declarations as unsigned char.

2.5.3. Environment Controls

This section describes the -⁠M<pgflag> options that control environments.

Default: For arguments that you do not specify, the default environment option depends on your configuration.

The following list provides the syntax for each -⁠M<pgflag> option that controls environments. Each option has a description and, if appropriate, a list of any related options.

-Mnostartup
instructs the linker not to link in the standard startup routine that contains the entry point (_start) for the program.
Note: If you use the -⁠Mnostartup option and do not supply an entry point, the linker issues the following error message: Warning: cannot find entry symbol _start
-M[no]smartalloc[=huge|huge:<n>|hugebss|nohuge]
adds a call to the routine mallopt in the main routine. This option supports large TLBs. This option must be used to compile the main routine to enable optimized malloc routines.
The option arguments can be any of the following:
huge
Link in the huge page runtime library.
Enables large 2-megabyte pages to be allocated. The effect is to reduce the number of TLB entries required to execute a program. This option is most effective on Barcelona and Core 2 systems; older architectures do not have enough TLB entries for this option to be beneficial. By itself, the huge suboption tries to allocate as many huge pages as required.
nohuge
Overrides a previous -⁠Msmartalloc=huge setting.
Tip: To be effective, this switch must be specified when compiling the file containing the Fortran, C, or C++ main program.
-M[no]hugetlb
links in the huge page runtime library.
Enables large 2-megabyte pages to be allocated. The effect is to reduce the number of TLB entries required to execute a program. This option is most effective on Barcelona and Core 2 systems; older architectures do not have enough TLB entries for this option to be beneficial. By itself, the huge suboption tries to allocate as many huge pages as required.
You can also limit the pages allocated by using the environment variable PGI_HUGE_PAGES.
-M[no]stddef
instructs the compiler not to predefine any macros to the preprocessor when compiling a C program.
-Mnostdinc
instructs the compiler to not search the standard location for include files.
-Mnostdlib
instructs the linker not to link in the standard librarieslibpgftnrtl.a, libm.a, libc.a, and libpgc.a in the library directory lib within the standard directory. You can link in your own library with the -⁠l option or specify a library directory with the -⁠L option.

2.5.4. Fortran Language Controls

This section describes the -⁠M<pgflag> options that affect Fortran language interpretations by the PGI Fortran compilers. These options are valid only for the Fortran compiler drivers.

Default: Before looking at all the options, let's look at the defaults. For arguments that you do not specify, the defaults are as follows:

nobackslash nodefaultunit dollar,_ noonetrip nounixlogical
nodclchk nodlines noiomutex nosave noupcase

The following list provides the syntax for each -⁠M<pgflag> option that affect Fortran language interpretations. Each option has a description and, if appropriate, a list of any related options.

-Mallocatable=95|03
controls whether Fortran 95 or Fortran 2003 semantics are used in allocatable array assignments. The default behavior is to use Fortran 95 semantics; the 03 option instructs the compiler to use Fortran 2003 semantics.
-Mbackslash
instructs the compiler to treat the backslash as a normal character, and not as an escape character in quoted strings.
-Mnobackslash
instructs the compiler to recognize a backslash as an escape character in quoted strings (in accordance with standard C usage).
-Mcuda
instructs the compiler to enable CUDA Fortran.

The following suboptions exist:

Note: If more than one option is on the command line, all the specified options occur.
cc30
Generate code for compute capability 3.0.
cc35
Generate code for compute capability 3.5.
cc3x
Generate code for the lowest 3.x compute capability possible.
cc3+
Is equivalent to cc3x.
cc50
Generate code for compute capability 5.0.
cc60
Generate code for compute capability 6.0.
cuda7.5 or 7.5
Specify the NVIDIA CUDA 7.5 version of the toolkit. This is the default.
cuda8.0 or 8.0
Specify the NVIDIA CUDA 8.0 version of the toolkit.
Note: Compile with the CUDA 7.5 or CUDA 8.0 toolkit either by using the -Mcuda=7.5 or -Mcuda=8.0 option, or by adding set DEFCUDAVERSION=7.5 or set DEFCUDAVERSION=8.0 to the siterc file. This action generates binaries that may not work on machines with an earlier CUDA driver.
pgaccelinfo prints the driver version as the first line of output.
  • For a 7.5 driver: CUDA Driver Version 7050
  • For an 8.0 driver: CUDA Driver Version 8000
emu
Enable CUDA Fortran emulation mode.
fastmath
Use routines from the fast math library.
fermi
is equivalent to -Mcuda,cc2x
[no]flushz
Enable[disable] flush-to-zero mode for floating point computations in the GPU code generated for CUDA Fortran kernels.
generate rdc
Generate relocatable device code
keepbin
Keep the generated binary (.bin) file for CUDA Fortran.
keepgpu
Keep the generated GPU code for CUDA Fortran.
keepptx
Keep the portable assembly (.ptx) file for the GPU code.
kepler
is equivalent to -Mcuda,cc3x
llvm
Generate code using the llvm-based back-end.
[no]debug
Enable[disable] GPU debug information generation.
[no]lineinfo
Enable[disable] GPU line information generation.
maxregcount:n
Specify the maximum number of registers to use on the GPU. Leaving this blank indicates no limit.
nofma
Do not generate fused multiply-add instructions.
noL1
Prevent the use of L1 hardware data cache to cache global variables.
ptxinfo
Show PTXAS informational messages during compilation.
rdc
Enable CUDA Fortran separate compilation and linking of device routines, including device routines in Fortran modules.
To enable separate compilation and linking, include the command line option -Mcuda=rdc on both the compile and the link steps.
-Mdclchk
instructs the compiler to require that all program variables be declared.
-Mnodclchk
instructs the compiler not to require that all program variables be declared.
-Mdefaultunit
instructs the compiler to treat "*" as a synonym for standard input for reading and standard output for writing.
-Mnodefaultunit
instructs the compiler to treat "*" as a synonym for unit 5 on input and unit 6 on output.
-Mdlines
instructs the compiler to treat lines containing "D" in column 1 as executable statements (ignoring the "D").
-Mnodlines
instructs the compiler not to treat lines containing "D" in column 1 as executable statements. The compiler does not ignore the "D".
-Mdollar,char
char specifies the character to which the compiler maps the dollar sign. The compiler allows the dollar sign in names.
-Mextend
instructs the compiler to accept 132-column source code; otherwise it accepts 72-column code.
-Mfixed
instructs the compiler to assume input source files are in FORTRAN-style fixed form format.
-Mfree
instructs the compiler to assume input source files are in Fortran 90/95 freeform format.
-Miomutex
instructs the compiler to generate critical section calls around Fortran I/O statements.
-Mnoiomutex
instructs the compiler not to generate critical section calls around Fortran I/O statements.
-Monetrip
instructs the compiler to force each DO loop to execute at least once. This option is useful for programs written for earlier versions of Fortran.
-Mnoonetrip
instructs the compiler not to force each DO loop to execute at least once.
-Msave
instructs the compiler to assume that all local variables are subject to the SAVE statement.
This may allow older Fortran programs to run, but it can greatly reduce performance.
-Mnosave
instructs the compiler not to assume that all local variables are subject to the SAVE statement.
-Mstandard
instructs the compiler to flag non-ANSI-conforming source code.
-Munixlogical
directs the compiler to treat logical values as true if the value is non-zero and false if the value is zero (UNIX FORTRAN convention). When -⁠Munixlogical is enabled, a logical value or test that is non-zero is .TRUE., and a value or test that is zero is .FALSE.. In addition, the value of a logical expression is guaranteed to be one (1) when the result is .TRUE..
-Mnounixlogical
directs the compiler to use the VMS convention for logical values for true and false. Even values are true and odd values are false.
-Mupcase
instructs the compiler to preserve uppercase letters in identifiers.
With -⁠Mupcase, the identifiers "X" and "x" are different. Keywords must be in lower case.
This selection affects the linking process. If you compile and link the same source code using -⁠Mupcase on one occasion and -⁠Mnoupcase on another, you may get two different executables – depending on whether the source contains uppercase letters. The standard libraries are compiled using the default -⁠Mnoupcase .
-Mnoupcase
instructs the compiler to convert all identifiers to lower case.
This selection affects the linking process. If you compile and link the same source code using -⁠Mupcase on one occasion and -⁠Mnoupcase on another, you may get two different executables, depending on whether the source contains uppercase letters. The standard libraries are compiled using -⁠Mnoupcase.

2.5.5. Inlining Controls

This section describes the -⁠M<pgflag> options that control function inlining.

Usage:Before looking at all the options, let’s look at a couple examples. In the following example, the compiler extracts functions that have 500 or fewer statements from the source file myprog.f and saves them in the file extract.il.

$ pgfortran -Mextract=500 -o extract.il myprog.f

In the following example, the compiler inlines functions with fewer than approximately 100 statements in the source file myprog.f.

$ pgfortran -Minline=maxsize:100 myprog.f

Related options: -⁠o, -⁠Mextract

The following list provides the syntax for each -⁠M<pgflag> option that controls function inlining. Each option has a description and, if appropriate, a list of any related options.

- M[no]autoinline[=option[,option,...]]
instructs the compiler to inline [not to inline] a C/C++ function at -⁠O2, where the option can be any of these:
maxsize:n
instructs the compiler not to inline functions of size > n. The default size is 100.
totalsize:n
instructs the compiler to stop inlining when the size equals n. The default size is 800.
-Mextract[=option[,option,...]]
Extracts functions from the file indicated on the command line and creates or appends to the specified extract directory where option can be any of the following:
name:func
instructs the extractor to extract function func from the file.
size:number
instructs the extractor to extract functions with number or fewer statements from the file.
lib:filename.ext
instructs the extractor to use directory filename.ext as the extract directory, which is required to save and re-use inline libraries.

If you specify both name and size, the compiler extracts functions that match func, or that have number or fewer statements. For examples of extracting functions, refer to the ‘Using Function Inlining’ section of the PGI Compiler User's Guide.

-Minline[=option[,option,...]]
instructs the compiler to pass options to the function inliner, where the option can be any of the following:
except:func
Inlines all eligible functions except func, a function in the source text. You can use a comma-separated list to specify multiple functions.
[name:]func
Inlines all functions in the source text whose name matches func. You can use a comma-separated list to specify multiple functions.

The function name should be a non-numeric string that does not contain a period. You can also use a name: prefix followed by the function name. If name: is specified, what follows is always the name of a function.

[maxsize:]number
A numeric option is assumed to be a size. Functions of size number or less are inlined. If both number and function are specified, then functions matching the given name(s) or meeting the size requirements are inlined.

The size number need not exactly equal the number of statements in a selected function; the size parameter is merely a rough guage.

[no]reshape
instructs the inliner to allow [disallow] inlining in Fortran even when array shapes do not match. The default is -⁠Minline=noreshape, except with -⁠Mconcur or -⁠mp, where the default is -⁠Minline=reshape,=reshape.
smallsize:number
Always inline functions of size smaller than number regardless of other size limits.
totalsize:number
Stop inlining in a function when the function's total inlined size reaches the number specified.
[lib:]filename.ext
instructs the inliner to inline the functions within the library file filename.ext. The compiler assumes that a filename.ext option containing a period is a library file.
Tip: Create the library file using the -⁠Mextract option. You can also use a lib: prefix followed by the library name.
  • If lib: is specified, no period is necessary in the library name. Functions from the specified library are inlined.
  • If no library is specified, functions are extracted from a temporary library created during an extract prepass.

If you specify both func and number, the compiler inlines functions that match the function name or have number or fewer statements.

Inlining can be disabled with -⁠Mnoinline.

For examples of inlining functions, refer to ‘Using Function Inlining’ in the PGI Compiler User’s Guide.

2.5.6. Optimization Controls

This section describes the -⁠M<pgflag> options that control optimization.

Default: Before looking at all the options, let's look at the defaults. For arguments that you do not specify, the default optimization control options are as follows:

depchk noipa nounroll nor8
i4 nolre novect nor8intrinsics
nofprelaxed noprefetch    
Note: If you do not supply an option to -⁠Mvect, the compiler uses defaults that are dependent upon the target system.

Usage: In this example, the compiler invokes the vectorizer with use of packed SIMD instructions enabled.

>$ pgfortran -Mvect=simd -Mcache_align myprog.f

Related options:-⁠g, -⁠O

The following list provides the syntax for each -⁠M<pgflag> option that controls optimization. Each option has a description and, if appropriate, a list of any related options.

-Mcache_align
Align unconstrained objects of length greater than or equal to 16 bytes on cache-line boundaries. An unconstrained object is a data object that is not a member of an aggregate structure or common block. This option does not affect the alignment of allocatable or automatic arrays.
To effect cache-line alignment of stack-based local variables, the main program or function must be compiled with -⁠Mcache_align.
-Mconcur[=option [,option,...]]
Instructs the compiler to enable auto-concurrentization of loops. If -⁠Mconcur is specified, multiple processors will be used to execute loops that the compiler determines to be parallelizable.
option is one of the following:
allcores
Instructs the compiler to use all available cores. Use this option at link time.
[no]altcode:n
Instructs the parallelizer to generate alternate serial code for parallelized loops.
  • If altcode is specified without arguments, the parallelizer determines an appropriate cutoff length and generates serial code to be executed whenever the loop count is less than or equal to that length.
  • If altcode:n is specified, the serial altcode is executed whenever the loop count is less than or equal to n.
  • If noaltcode is specified, the parallelized version of the loop is always executed regardless of the loop count.
cncall
Indicates that calls in parallel loops are safe to parallelize.
Loops containing calls are candidates for parallelization. Also, no minimum loop count threshold must be satisfied before parallelization will occur, and last values of scalars are assumed to be safe.
[no]innermost
Instructs the parallelizer to enable parallelization of innermost loops. The default is to not parallelize innermost loops, since it is usually not profitable on dual-core processors.
noassoc
Instructs the parallelizer to disable parallelization of loops with reductions.
When linking, the -⁠Mconcur switch must be specified or unresolved references result. The NCPUS environment variable controls how many processors or cores are used to execute parallelized loops.
Note: This option applies only on shared-memory multi-processor (SMP) or multicore processor-based systems.
-Mcray[=option[,option,...]]
(Fortran only) Force Cray Fortran (CF77) compatibility with respect to the listed options. Possible values of option include:
pointer
for purposes of optimization, it is assumed that pointer-based variables do not overlay the storage of any other variable.
-Mdepchk
instructs the compiler to assume unresolved data dependencies actually conflict.
-Mnodepchk
Instructs the compiler to assume potential data dependencies do not conflict. However, if data dependencies exist, this option can produce incorrect code.
-Mdse
Enables a dead store elimination phase that is useful for programs that rely on extensive use of inline function calls for performance. This is disabled by default.
-Mnodse
Disables the dead store elimination phase. This is the default.
-M[no]fpapprox[=option]
Perform certain floating point operations using low-precision approximation.
-⁠Mnofpapprox specifies not to use low-precision fp approximation operations.
By default -⁠Mfpapprox is not used.
If -⁠Mfpapprox is used without suboptions, it defaults to use approximate div, sqrt, and rsqrt. The available suboptions are these:
div
Approximate floating point division
sqrt
Approximate floating point square root
rsqrt
Approximate floating point reciprocal square root
-M[no]fpmisalign
Instructs the compiler to allow (not allow) vector arithmetic instructions with memory operands that are not aligned on 16-byte boundaries. The default is -⁠Mnofpmisalign on all processors.
Note: Applicable only with one of these options: -⁠tp barcelona or -⁠tp barcelona-64 or newer processors.
-M[no]fprelaxed[=option]
Instructs the compiler to use [not use] relaxed precision in the calculation of some intrinsic functions. Can result in improved performance at the expense of numerical accuracy.
The possible values for option are:
div
Perform divide using relaxed precision.
intrinsic
Enables use of relaxed precision intrinsics.
noorder
Do not allow expression reordering or factoring.
order
Allow expression reordering, including factoring.
recip
Perform reciprocal using relaxed precision.
rsqrt
Perform reciprocal square root (1/sqrt) using relaxed precision.
sqrt
Perform square root with relaxed precision.
With no options, -⁠Mfprelaxed generates relaxed precision code for those operations that generate a significant performance improvement, depending on the target processor.
The default is -⁠Mnofprelaxed which instructs the compiler to not use relaxed precision in the calculation of intrinsic functions.
-Mi4
(Fortran only) instructs the compiler to treat INTEGER variables as INTEGER*4.
-Mipa=<option>[,<option>[,...]]
Pass options to the interprocedural analyzer. Note:-⁠Mipa is not compatible with parallel make environments (e.g., pmake).
-⁠Mipa implies -⁠O2, and the minimum optimization level that can be specified in combination with -⁠Mipa is -⁠O2.
For example, if you specify -⁠Mipa -⁠O1 on the command line, the optimization level is automatically elevated to -⁠O2 by the compiler driver. Typically, as recommended, you would use -⁠Mipa=fast. Many of the following suboptions can be prefaced with no, which reverses or disables the effect of the suboption if it's included in an aggregate suboption such as -⁠Mipa=fast. The choices of option are:
[no]align
recognize when targets of a pointer dummy are aligned. The default is noalign.
[no]arg
remove arguments replaced by const, ptr. The default is noarg.
[no]cg
generate call graph information for viewing using the pgicg command-line utility. The default is nocg.
[no]const
perform interprocedural constant propagation. The default is const.
except:<func>
used with inline to specify functions which should not be inlined. The default is to inline all eligible functions according to internally defined heuristics. Valid only immediately following the inline suboption.
[no]f90ptr
F90/F95 pointer disambiguation across calls. The default is nof90ptr.
fast
choose IPA options generally optimal for the target. To see settings for -⁠Mipa=fast on a given target, use -⁠help.
force
force all objects to re-compile regardless of whether IPA information has changed.
[no]globals
optimize references to global variables. The default is noglobals.
inline[:n]
perform automatic function inlining. If the optional :n is provided, limit inlining to at most n levels. IPA-based function inlining is performed from leaf routines upward.
ipofile
save IPA information in an .ipo file rather than incorporating it into the object file.
jobs[:n]
recompile n jobs in parallel and print source file names as they are compiled.
[no]keepobj
keep the optimized object files, using file name mangling, to reduce re-compile time in subsequent builds. The default is keepobj.
[no]libc
optimize calls to certain standard C library routines. The default is nolibc.
[no]libinline
allow inlining of routines from libraries; implies -⁠Mipa=inline. The default is nolibinline.
[no]libopt
allow recompiling and optimization of routines from libraries using IPA information. The default is nolibopt.
[no]localarg
equivalent to arg plus externalization of local pointer targets. The default is nolocalarg.
main:<func>
specify a function to appear as a global entry point. May appear multiple times and it disables linking.
reaggregation
Enables IPA-guided structure reaggregation, which automatically attempts to reorder elements in a struct, or to split structs into substructs to improve memory locality and cache utilization.
rsqrt
Perform reciprocal square root (1/sqrt) using relaxed precision.
[no]pfo
enable profile feedback information. The nopfo option is valid only immediately following the inline suboption. -⁠Mipa=inline,nopfo tells IPA to ignore PFO information when deciding what functions to inline, if PFO information is available.
[no]ptr
enable pointer disambiguation across procedure calls. The default is noptr.
[no]pure
pure function detection. The default is nopure.
required
return an error condition if IPA is inhibited for any reason, rather than the default behavior of linking without IPA optimization.
[no]reshape
enable [disable] Fortran inline with mismatched array shapes. Valid only immediately following the inline suboption.
safe:[<function>|<library>]
declares that the named function, or all functions in the named library, are safe. A safe procedure does not call back into the known procedures and does not change any known global variables.
Without -⁠Mipa=safe, any unknown procedures cause IPA to fail.
[no]safeall
declares that all unknown procedures are safe. The default is nosafeall. For more information, refer to -⁠Mipa=safe.
[no]shape
perform Fortran 90 array shape propagation. The default is noshape.
summary
only collect IPA summary information when compiling. This option prevents IPA optimization of this file, but allows optimization for other files linked with this file.
[no]vestigial
remove uncalled (vestigial) functions. The default is novestigial.
If you use -⁠Mipa=vestigial in combination with -⁠Mipa=libopt with PGCC, you may encounter unresolved references at link time. These unresolved references are a result of erroneous removal of functions by the vestigial sub-option to -⁠Mipa. You can work around this problem by listing specific sub-options to -⁠Mipa, not including vestigial.
-Mlre[=array | assoc | noassoc]
Enables loop-carried redundancy elimination, an optimization that can reduce the number of arithmetic operations and memory references in loops. The available suboptions are:
array
treat individual array element references as candidates for possible loop-carried redundancy elimination. The default is to eliminate only redundant expressions involving two or more operands.
assoc
allow expression re-association. Specifying this suboption can increase opportunities for loop-carried redundancy elimination but may alter numerical results.
noassoc
disallow expression re-association.
-Mnolre
Disable loop-carried redundancy elimination.
-Mnoframe
Eliminate operations that set up a true stack frame pointer for every function. With this option enabled, you cannot perform a traceback on the generated code and you cannot access local variables.
-Mnoi4
(Fortran only) instructs the compiler to treat INTEGER variables as INTEGER*2.
-Mpre
Enables partial redundancy elimination.
-Mprefetch[=option [,option...]]
enables generation of prefetch instructions on processors where they are supported. Possible values for option include:
d:m
set the fetch-ahead distance for prefetch instructions to m cache lines.
n:p
set the maximum number of prefetch instructions to generate for a given loop to p.
nta
use the prefetch instruction.
plain
use the prefetch instruction (default).
t0
use the prefetcht0 instruction.
-Mnoprefetch
Disables generation of prefetch instructions.
-M[no]propcond
Enables or disables constant propagation from assertions derived from equality conditionals.
The default is enabled.
-Mr8
(Fortran only) The compiler promotes REAL variables and constants to DOUBLE PRECISION variables and constants, respectively. DOUBLE PRECISION elements are 8 bytes in length.
-Mnor8
(Fortran only) The compiler does not promote REAL variables and constants to DOUBLE PRECISION. REAL variables will be single precision (4 bytes in length).
-Mr8intrinsics
( pgfortran only) The compiler treats the intrinsics CMPLX and REAL as DCMPLX and DBLE, respectively.
-Mnor8intrinsics
( pgfortran only) The compiler does not promote the intrinsics CMPLX and REAL to DCMPLX and DBLE, respectively.
-Msafeptr[=option[,option,...]]
(pgcc and pgc++ only) instructs the C/C++ compiler to override data dependencies between pointers of a given storage class. Possible values of option include:
all
assume all pointers and arrays are independent and safe for aggressive optimizations, and in particular that no pointers or arrays overlap or conflict with each other.
arg
instructs the compiler to treat arrays and pointers with the same copyin and copyout semantics as Fortran dummy arguments.
global
instructs the compiler that global or external pointers and arrays do not overlap or conflict with each other and are independent.
local/auto
instructs the compiler that local pointers and arrays do not overlap or conflict with each other and are independent.
static
instructs the compiler that static pointers and arrays do not overlap or conflict with each other and are independent.
-Munroll[=option [,option...]]
invokes the loop unroller to execute multiple instances of the loop during each iteration. This also sets the optimization level to 2 if the level is set to less than 2, or if no -⁠O or -⁠g options are supplied. The option is one of the following:
c:m
instructs the compiler to completely unroll loops with a constant loop count less than or equal to m, a supplied constant. If this value is not supplied, the m count is set to 4.
m:<n>
instructs the compiler to unroll multi-block loops n times. This option is useful for loops that have conditional statements. If n is not supplied, then the default value is 4. The default setting is not to enable -⁠Munroll=m.
n:<n>
instructs the compiler to unroll single-block loops n times, a loop that is not completely unrolled, or has a non-constant loop count. If n is not supplied, the unroller computes the number of times a candidate loop is unrolled.
-Mnounroll
instructs the compiler not to unroll loops.
-M[no]vect[=option [,option,...]]
enable [disable] the code vectorizer, where option is one of the following:
altcode
Instructs the vectorizer to generate alternate code (altcode) for vectorized loops when appropriate. For each vectorized loop the compiler decides whether to generate altcode and what type or types to generate, which may be any or all of: altcode without iteration peeling, altcode with non-temporal stores and other data cache optimizations, and altcode based on array alignments calculated dynamically at runtime. The compiler also determines suitable loop count and array alignment conditionals for executing the altcode. This option is enabled by default.
noaltcode
Instructs the vectorizer to disable alternate code generation for vectorized loops.
assoc
Instructs the vectorizer to enable certain associativity conversions that can change the results of a computation due to roundoff error. A typical optimization is to change an arithmetic operation to an arithmetic operation that is mathematically correct, but can be computationally different, due to round-off error.
noassoc
Instructs the vectorizer to disable associativity conversions.
cachesize:n
Instructs the vectorizer, when performing cache tiling optimizations, to assume a cache size of n. The default is set per processor type, either using the -⁠tp switch or auto-detected from the host computer.
[no]gather
Instructs the vectorizer to vectorize loops containing indirect array references, such as this one:
sum = 0.d0
do k=d(j),d(j+1)-1
     sum = sum + a(k)*b(c(k))
enddo
The default is gather.
partial
Instructs the vectorizer to enable partial loop vectorization through innermost loop distribution.
prefetch
Instructs the vectorizer to search for vectorizable loops and, wherever possible, make use of prefetch instructions.
[no]short
Instructs the vectorizer to enable [disable] short vector operations. -Mvect=short enables generation of packed SIMD instructions for short vector operations that arise from scalar code outside of loops or within the body of a loop iteration.
[no]sizelimit
Instructs the vectorizer to generate vector code for all loops where possible regardless of the number of statements in the loop. This overrides a heuristic in the vectorizer that ordinarily prevents vectorization of loops with a number of statements that exceeds a certain threshold. The default is nosizelimit.
smallvect[:n]
Instructs the vectorizer to assume that the maximum vector length is less than or equal to n. The vectorizer uses this information to eliminate generation of the stripmine loop for vectorized loops wherever possible. If the size n is omitted, the default is 100.
Note: No space is allowed on either side of the colon (:).
[no]sse
Instructs the vectorizer to search for vectorizable loops and, wherever possible, make use of SIMD and prefetch instructions. The default is nosse.
[no]uniform
Instructs the vectorizer to perform the same optimizations in the vectorized and residual loops.
Note: This option may affect the performance of the residual loop.
-Mnovect
instructs the compiler not to perform vectorization. You can use this option to override a previous instance of -⁠Mvect on the command-line, in particular for cases in which -⁠Mvect is included in an aggregate option such as -⁠fastsse.
-Mvect=[option]
instructs the compiler to enable loop vectorization, where option is one of the following:
partial
Enable partial loop vectorization through innermost loop distribution.
[no]short
Enable [disable] short vector operations. Enables [disables] generation of packed SIMD instructions for short vector operations that arise from scalar code outside of loops or within the body of a loop iteration.
simd[:{128|256}]
Specifies to vectorize using SIMD instructions and data, either 128 bits or 256 bits wide, on processors where there is a choice.
tile
Enable tiling/blocking over multiple nested loops for more efficient cache utilization.
-Mnovintr
instructs the compiler not to perform idiom recognition or introduce calls to hand-optimized vector functions.

2.5.7. Miscellaneous Controls

This section describes the -⁠M<pgflag> options that do not easily fit into one of the other categories of -⁠M<pgflag> options.

Default: Before looking at all the options, let’s look at the defaults. For arguments that you do not specify, the default miscellaneous options are as follows:

inform nobounds nolist warn

Related options: -⁠m, -⁠S, -⁠V, -⁠v

Usage: In the following example, the compiler includes Fortran source code with the assembly code.

 $ pgfortran -Manno -S myprog.f

In the following example, the assembler does not delete the assembly file myprog.s after the assembly pass.

 $ pgfortran -Mkeepasm myprog.f

In the following example, the compiler displays information about inlined functions with fewer than approximately 20 source lines in the source file myprog.f.

 $ pgfortran -Minfo=inline -Minline=20 myprog.f

In the following example, the compiler creates the listing file myprog.lst.

 $ pgfortran -Mlist myprog.f

In the following example, array bounds checking is enabled.

 $ pgfortran -Mbounds myprog.f

The following list provides the syntax for each miscellaneous -⁠M<pgflag> option. Each option has a description and, if appropriate, a list of any related options.

-Manno
annotate the generated assembly code with source code. Implies -⁠Mkeepasm.
-Mbounds
enables array bounds checking.
  • If an array is an assumed size array, the bounds checking only applies to the lower bound.
  • If an array bounds violation occurs during execution, an error message describing the error is printed and the program terminates. The text of the error message includes the name of the array, the location where the error occurred (the source file and the line number in the source), and information about the out of bounds subscript (its value, its lower and upper bounds, and its dimension).
The following is a sample error message:
PGFTN-F-Subscript out of range for array a (a.f: 2) 
subscript=3, lower bound=1, upper bound=2, dimension=2
-Mnobounds
disables array bounds checking.
-Mbyteswapio
swap byte-order from big-endian to little-endian or vice versa upon input/output of Fortran unformatted data files.
-Mchkptr
instructs the compiler to check for pointers that are dereferenced while initialized to NULL (Fortran only).
-Mchkstk
instructs the compiler to check the stack for available space in the prologue of a function and before the start of a parallel region. Prints a warning message and aborts the program gracefully if stack space is insufficient.
This option is useful when many local and private variables are declared in an OpenMP program.
If the user also sets the PGI_STACK_USAGE environment variable to any value, then the program displays the stack space allocated and used after the program exits. For example, you might see something similar to the following message:
thread 0 stack: max 8180KB, used 48KB
This message indicates that the program used 48KB of a 8180KB allocated stack. This information is useful when you want to explicitly set a reserved and committed stack size for your programs.
For more information on the PGI_STACK_USAGE, refer to ‘PGI_STACK_USAGE’ in the PGI Compiler User’s Guide.
-Mcpp[=option [,option,...]]
run the PGI cpp-like preprocessor without execution of any subsequent compilation steps. This option is useful for generating dependence information to be included in makefiles.
Note: Only one of the m, md, mm or mmd options can be present; if multiple of these options are listed, the last one listed is accepted and the others are ignored.
The option is one or more of the following:
m
print makefile dependencies to stdout.
md
print makefile dependencies to filename.d, where filename is the root name of the input file being processed, ignoring system include files.
mm
print makefile dependencies to stdout, ignoring system include files.
mmd
print makefile dependencies to filename.d, where filename is the root name of the input file being processed, ignoring system include files.
[no]comment
do [do not] retain comments in output.
[suffix:]<suff>
use <suff> as the suffix of the output file containing makefile dependencies.
-Mgccbug[s]
instructs the compiler to match the behavior of certain gcc bugs.
-Miface[=option]
adjusts the calling conventions for Fortran, where option is one of the following:
cref
uses CREF calling conventions, no trailing underscores.
mixed_str_len_arg
places the lengths of character arguments immediately after their corresponding argument. Has affect only with the CREF calling convention.
nomixed_str_len_arg
places the lengths of character arguments at the end of the argument list. Has affect only with the CREF calling convention.
-Minfo[=option [,option,...]]
instructs the compiler to produce information on standard error, where option is one of the following:
all
instructs the compiler to produce all available -⁠Minfo information. Implies a number of suboptions:
-Mneginfo=accel,inline,ipa,loop,lre,mp,opt,par,vect 
accel
instructs the compiler to enable accelerator information.
ccff
instructs the compiler to append common compiler feedback format information, such as optimization information, to the object file.
ftn
instructs the compiler to enable Fortran-specific information.
inline
instructs the compiler to display information about extracted or inlined functions. This option is not useful without either the -⁠Mextract or -⁠Minline option.
intensity
instructs the compiler to provide informational messages about the intensity of the loop. Specify <n> to get messages on nested loops.
  • For floating point loops, intensity is defined as the number of floating point operations divided by the number of floating point loads and stores.
  • For integer loops, the loop intensity is defined as the total number of integer arithmetic operations, which may include updates of loop counts and addresses, divided by the total number of integer loads and stores.
  • By default, the messages just apply to innermost loops.
ipa
instructs the compiler to display information about interprocedural optimizations.
loop
instructs the compiler to display information about loops, such as information on vectorization.
lre
instructs the compiler to enable LRE, loop-carried redundancy elimination, information.
mp
instructs the compiler to display information about parallelization.
opt
instructs the compiler to display information about optimization.
par
instructs the compiler to enable parallelizer information.
pfo
instructs the compiler to enable profile feedback information.
time
instructs the compiler to display compilation statistics.
unroll
instructs the compiler to display information about loop unrolling.
vect
instructs the compiler to enable vectorizer information.
-Minform=level
instructs the compiler to display error messages at the specified and higher levels, where level is one of the following:
fatal
instructs the compiler to display fatal error messages.
[no]file
instructs the compiler to print or not print source file names as they are compiled. The default is to print the names: -⁠Minform=file.
inform
instructs the compiler to display all error messages (inform, warn, severe and fatal).
severe
instructs the compiler to display severe and fatal error messages.
warn
instructs the compiler to display warning, severe and fatal error messages.
-Minstrumentation=option
specifies the level of instrumentation calls generated. This option implies -Minfo=ccff, -Mframe.
option is one of the following:
level
specifies the level of instrumentation calls generated.
function (default)
generates instrumentation calls for entry and exit to functions.
Just after function entry and just before function exit, the following profiling functions are called with the address of the current function and its call site.
void __cyg_profile_func_enter (void *this_fn, void *call_site);
void __cyg_profile_func_exit (void *this_fn, void *call_site);
In these calls, the first argument is the address of the start of the current function.
-Mkeepasm
instructs the compiler to keep the assembly file as compilation continues. Normally, the assembler deletes this file when it is finished. The assembly file has the same filename as the source file, but with a .s extension.
-M list
instructs the compiler to create a listing file. The listing file is filename.lst, where the name of the source file is filename.f.
-Mnames=lowercase|uppercase
specifies the case for the names of Fortran externals.
  • lowercase - Use lowercase for Fortran externals.
  • uppercase - Use uppercase for Fortran externals.
-Mneginfo[=option [,option,...]]
instructs the compiler to produce information on standard error, where option is one of the following:
all
instructs the compiler to produce all available information on why various optimizations are not performed.
accel
instructs the compiler to enable accelerator information.
ccff
instructs the compiler to append information, such as optimization information, to the object file.
concur
instructs the compiler to produce all available information on why loops are not automatically parallelized. In particular, if a loop is not parallelized due to potential data dependence, the variable(s) that cause the potential dependence are listed in the messages that you see when using the option -⁠Mneginfo.
ftn
instructs the compiler to enable Fortran-specific information.
inline
instructs the compiler to display information about extracted or inlined functions. This option is not useful without either the -⁠Mextract or -⁠Minline option.
ipa
instructs the compiler to display information about interprocedural optimizations.
loop
instructs the compiler to display information about loops, such as information on vectorization.
lre
instructs the compiler to enable LRE, loop-carried redundancy elimination, information.
mp
instructs the compiler to display information about parallelization.
opt
instructs the compiler to display information about optimization.
par
instructs the compiler to enable parallelizer information.
pfo
instructs the compiler to enable profile feedback information.
vect
instructs the compiler to enable vectorizer information.
-Mnolist
the compiler does not create a listing file. This is the default.
-Mnoopenmp
when used in combination with the -⁠mp option, the compiler ignores OpenMP parallelization directives or pragmas, but still processes SGI-style parallelization directives or pragmas.
-Mnorpath
(Linux only) Do not add -⁠rpath to the link line.
-Mpreprocess
instruct the compiler to perform cpp-like preprocessing on assembly and Fortran input source files.
-Mwritable_strings
stores string constants in the writable data segment.
Note: Options -⁠Xs and -⁠Xst include -⁠Mwritable_strings.

3. C++ Name Mangling

Name mangling transforms the names of entities so that the names include information on aspects of the entity’s type and fully qualified name. This ability is necessary since the intermediate language into which a program is translated contains fewer and simpler name spaces than there are in the C++ language; specifically:

  • Overloaded function names are not allowed in the intermediate language.
  • Classes have their own scopes in C++, but not in the generated intermediate language. For example, an entity x from inside a class must not conflict with an entity x from the file scope.
  • External names in the object code form a completely flat name space. The names of entities with external linkage must be projected onto that name space so that they do not conflict with one another. A function f from a class A, for example, must not have the same external name as a function f from class B.
  • Some names are not names in the conventional sense of the word, they're not strings of alphanumeric characters, for example: operator=.

There are two main problems here:

  1. Generating external names that will not clash.
  2. Generating alphanumeric names for entities with strange names in C++.

Name mangling solves these problems by generating external names that will not clash, and alphanumeric names for entities with strange names in C++. It also solves the problem of generating hidden names for some behind-the-scenes language support in such a way that they match up across separate compilations.

You see mangled names if you view files that are translated by PGC++ or PGCC, and you do not use tools that demangle the C++ names. Intermediate files that use mangled names include the assembly and object files created by the PGC++ command. To view demangled names, use the tool pggdecode, which takes input from stdin. pggdecode demangles PGC++ names.

prompt> pggdecode
_ZN1A1gEf
A::g(float)

The name mangling algorithm for the PGC++ compiler is IA-64 ABI compliant and is described at http://mentorembedded.github.io/cxx-abi. Refer to this document for a complete description of the name mangling algorithm.

4. Directives and Pragmas Reference

PGI Fortran compilers support proprietary directives and pragmas. These directives and pragmas override corresponding command-line options. For usage information such as the scope and related command-line options, refer to the PGI Compiler User’s Guide.

This section contains detailed descriptions of PGI’s proprietary directives and pragmas.

4.1. PGI Proprietary Fortran Directive and C/C++ Pragma Summary

Directives (Fortran comments) and C/C++ pragmas may be supplied by the user in a source file to provide information to the compiler. Directives and pragmas alter the effects of certain command line options or default behavior of the compiler. They provide pragmatic information that control the actions of the compiler in a particular portion of a program without affecting the program as a whole. That is, while a command line option affects the entire source file that is being compiled, directives and pragmas apply, or disable, the effects of a command line option to selected subprograms or to selected loops in the source file, for example, to optimize a specific area of code. Use directives and pragmas to tune selected routines or loops.

The Fortran directives may have any of the following forms:

!pgi$g directive
!pgi$r directive
!pgi$l directive
!pgi$ directive

where the scope indicator follows the $ and is either g (global), r (routine), or l (loop). This indicator controls the scope of the directive, though some directives ignore the scope indicator.

Note: If the input is in fixed format, the comment character, !, * or C, must begin in column 1.

Directives and pragmas override corresponding command-line options. For usage information such as the scope and related command-line options, refer to the the ‘Using Directives and Pragmas’ section of the PGI Compiler User's Guide.

4.1.1. altcode (noaltcode)

The altcode directive or pragma instructs the compiler to generate alternate code for vectorized or parallelized loops.

The noaltcode directive or pragma disables generation of alternate code.

Scope: This directive or pragma affects the compiler only when -⁠Mvect=sse-⁠Mvect=simd or -⁠Mconcur is enabled on the command line.

!pgi$ altcode
Enables alternate code (altcode) generation for vectorized loops. For each loop the compiler decides whether to generate altcode and what type(s) to generate, which may be any or all of: altcode without iteration peeling, altcode with non-temporal stores and other data cache optimizations, and altcode based on array alignments calculated dynamically at runtime. The compiler also determines suitable loop count and array alignment conditions for executing the alternate code.
!pgi$ altcode alignment
For a vectorized loop, if possible, generates an alternate vectorized loop containing additional aligned moves which is executed if a runtime array alignment test is passed.
!pgi$ altcode [(n)] concur
For each auto-parallelized loop, generates an alternate serial loop to be executed if the loop count is less than or equal to n. If n is omitted or n is 0, the compiler determines a suitable value of n for each loop.
!pgi$ altcode [(n)] concurreduction
Sets the loop count threshold for parallelization of reduction loops to n. For each auto-parallelized reduction loop, generate an alternate serial loop to be executed if the loop count is less than or equal to n. If n is omitted or n is 0, the compiler determines a suitable value of n for each loop.
!pgi$ altcode [(n)] nontemporal
For a vectorized loop, if possible, generates an alternate vectorized loop containing non-temporal stores and other cache optimizations to be executed if the loop count is greater than n. If n is omitted or n is 1, the compiler determines a suitable value of n for each loop. The alternate code is optimized for the case when the data referenced in the loop does not all fit in level 2 cache.
!pgi$ altcode [(n)] nopeel
For a vectorized loop where iteration peeling is performed by default, if possible, generates an alternate vectorized loop without iteration peeling to be executed if the loop count is less than or equal to n. If n is omitted or n is 1, the compiler determines a suitable value of n for each loop, and in some cases it may decide not to generate an alternate unpeeled loop.
!pgi$ altcode [(n)] vector
For each vectorized loop, generates an alternate scalar loop to be executed if the loop count is less than or equal to n. If n is omitted or n is 1, the compiler determines a suitable value of n for each loop.
!pgi$ noaltcode
Sets the loop count thresholds for parallelization of all innermost loops to 0, and disables alternate code generation for vectorized loops.

4.1.2. assoc (noassoc)

This directive or pragma toggles the effects of the -⁠Mvect=noassoc command-line option, an optimization -⁠M control.

Scope: This directive or pragma affects the compiler only when -⁠Mvect=simd is enabled on the command line.

By default, when scalar reductions are present the vectorizer may change the order of operations, such as dot product, so that it can generate better code. Such transformations may change the result of the computation due to roundoff error. The noassoc directive disables these transformations.

4.1.3. bounds (nobounds)

This directive or pragma alters the effects of the -⁠Mbounds command line option. This directive enables the checking of array bounds when subscripted array references are performed. By default, array bounds checking is not performed.

4.1.4. cncall (nocncall)

This directive or pragma indicates that loops within the specified scope are considered for parallelization, even if they contain calls to user-defined subroutines or functions. A nocncall directive cancels the effect of a previous cncall.

4.1.5. concur (noconcur)

This directive or pragma alters the effects of the -⁠Mconcur command-line option. The directive instructs the auto-parallelizer to enable auto-concurrentization of loops.

Scope: This directive or pragma affects the compiler only when -⁠Mconcur is enabled on the command line.

If concur is specified, the compiler uses multiple processors to execute loops which the auto-parallelizer determines to be parallelizable. The noconcur directive disables these transformations; however, use of concur overrides previous noconcur statements.

4.1.6. depchk (nodepchk)

This directive or pragma alters the effects of the -⁠Mdepchk command line option. When potential data dependencies exist, the compiler, by default, assumes that there is a data dependence that in turn may inhibit certain optimizations or vectorizations. nodepchk directs the compiler to ignore unknown data dependencies.

4.1.7. eqvchk (noeqvchk)

The eqvchk directive or pragma specifies to check dependencies between EQUIVALENCE associated elements. When examining data dependencies, noeqvchk directs the compiler to ignore any dependencies between variables appearing in EQUIVALENCE statements.

4.1.8. fcon (nofcon)

This C/C++ pragma alters the effects of the -⁠Mfcon (a -⁠M Language control) command-line option.

The pragma instructs the compiler to treat non-suffixed floating-point constants as float rather than double. By default, all non-suffixed floating-point constants are treated as double.

Note:

Only routine or global scopes are allowed for this C/C++ pragma.

4.1.9. invarif (noinvarif)

This directive or pragma has no corresponding command-line option. Normally, the compiler removes certain invariant if constructs from within a loop and places them outside of the loop. The directive noinvarif directs the compiler not to move such constructs. The directive invarif toggles a previous noinvarif.

4.1.10. ivdep

The ivdep directive assists the compiler's dependence analysis and is equivalent to the directive nodepchk.

4.1.11. lstval (nolstval)

This directive or pragma has no corresponding command-line option. The compiler determines whether the last values for loop iteration control variables and promoted scalars need to be computed. In certain cases, the compiler must assume that the last values of these variables are needed and therefore computes their last values. The directive nolstval directs the compiler not to compute the last values for those cases.

4.1.12. opt

The opt directive or pragma overrides the value specified by the -⁠On command line option.

The syntax of this directive or pragma is:

!pgi$<scope> opt=<level>

where the optional <scope> is r or g and <level> is an integer constant representing the optimization level to be used when compiling a subprogram (routine scope) or all subprograms in a file (global scope).

4.1.13. prefetch

The prefetch directive or pragma the compiler emits prefetch instructions whereby elements are fetched into the data cache prior to first use. By varying the prefetch distance, it is sometimes possible to reduce the effects of main memory latency and improve performance.

The syntax of this directive or pragma is:

!$mem prefetch <var1>[,<var2>[,...]]

where <varn> is any valid variable, member, or array element reference.

4.1.14. safe (nosafe)

This C/C++ pragma has no corresponding command-line option. By default, the compiler assumes that all pointer arguments are unsafe. That is, the storage located by the pointer can be accessed by other pointers.

The formats of the safe pragma are:

#pragma [scope] [no]safe
#pragma safe (variable [, variable]...)

where scope is either global or routine.

  • When the pragma safe is not followed by a variable name or a list of variable names:
    • If the scope is routine, then the compiler treats all pointer arguments appearing in the routine as safe.
    • If the scope is global, then the compiler treats all pointer arguments appearing in all routines as safe.
  • When the pragma safe is followed by a variable name or a list of variable names, each name is the name of a pointer argument in the current function, and the compiler considers that named argument to be safe.
    Note: If only one variable name is specified, you may omit the surrounding parentheses.

4.1.15. safe_lastval

During parallelization, scalars within loops need to be privatized. Problems are possible if a scalar is accessed outside the loop. If you know that a scalar is assigned on the last iteration of the loop, making it safe to parallelize the loop, you use the safe_lastval directive or pragma to let the compiler know the loop is safe to parallelize.

For example, use the following Fortran directive or C pragma to tell the compiler that for a given loop the last value computed for all scalars make it safe to parallelize the loop:

!pgi$l safe_lastval
#pragma loop safe_lastval

The command-line option-Msafe_lastval provides the same information for all loops within the routines being compiled, essentially providing global scope.

In the following example, the value of t may not be computed on the last iteration of the loop.

do i = 1, N
   if( f(x(i)) > 5.0) then
       t = x(i)
   endif
enddo
v = t

If a scalar assigned within a loop is used outside the loop, we normally save the last value of the scalar. Essentially the value of the scalar on the "last iteration" is saved, in this case when i=N.

If the loop is parallelized and the scalar is not assigned on every iteration, it may be difficult to determine on what iteration t is last assigned, without resorting to costly critical sections. Analysis allows the compiler to determine if a scalar is assigned on every iteration, thus the loop is safe to parallelize if the scalar is used later. An example loop is:

do i = 1, N
   if( x(i) > 0.0 ) then
       t = 2.0
   else
     t = 3.0
   endif
   ...
   y(i) = t
   ...
enddo
v = t

where t is assigned on every iteration of the loop. However, there are cases where a scalar may be privatizable. If it is used after the loop, it is unsafe to parallelize. Examine this loop:

do i = 1,N
   if( x(i) > 0.0 ) then
       t = x(i)
       ...
       y(i) = t
       ...
   endif
enddo
v = t

where each use of t within the loop is reached by a definition from the same iteration. Here t is privatizable, but the use of t outside the loop may yield incorrect results since the compiler may not be able to detect on which iteration of the parallelized loop t is assigned last.

The compiler detects these cases. When a scalar is used after the loop, but is not defined on every iteration of the loop, parallelization does not occur.

4.1.16. safeptr (nosafeptr)

The pragma safeptr directs the compiler to treat pointer variables of the indicated storage class as safe. The pragma nosafeptr directs the compiler to treat pointer variables of the indicated storage class as unsafe. This pragma alters the effects of the -⁠Msafeptr command-line option.

The syntax of this pragma is:

!pgi$[] [no]safeptr={arg|local|auto|global|static|all},..
#pragma [scope] [no]safeptr={arg|local|auto|global|static|all},... 

where scope is one of global, routine, or loop. and the values local and auto are equivalent.

  • all – All pointers are safe
  • arg – Argument pointers are safe
  • local – local pointers are safe
  • global – global pointers are safe
  • static – static local pointers are safe

In a file containing multiple functions, the command-line option -⁠Msafeptr might be helpful for one function, but can’t be used because another function in the file would produce incorrect results. In such a file, the safeptr pragma, used with routine scope could improve performance and produce correct results.

4.1.17. single (nosingle)

The pragma single directs the compiler not to implicitly convert float values to double non-prototyped functions. This can result in faster code if the program uses only float parameters.

Note: Since ANSI C specifies that floats must be converted to double, this pragma results in non-ANSI conforming code. Valid only for routine or global scope.

4.1.18. tp

You use the directive or pragmatp to specify one or more processor targets for which to generate code.

!pgi$ tp [target]... 
Note: The tp directive or pragma can only be applied at the routine or global level. For more information about these levels, refer to the ‘Scope of C/C++ Pragmas and Command-Line Options’ section of the PGI Compiler User's Guide.

4.1.19. unroll (nounroll)

The unroll directive or pragma enables loop unrolling while nounroll disables loop unrolling.

Note:

The unroll directive or pragma has no effect on vectorized loops.

The unroll directive or pragma takes arguments c, n and m.

  • c specifies that c complete unrolling should be turned on or off.
  • n specifies single block loop unrolling.
  • m specifies multi-block loop unrolling.

In addition, a constant may be specified for the c, n and m arguments.

  • c:v sets the threshold to which c unrolling applies. v is a constant; and a loop whose constant loop count is less than or equal to (<=) v is completely unrolled.
    !pgi$ unroll = c:v
  • n:v unrolls single block loops v times.
    !pgi$ unroll = n:v
  • m:v unrolls single block loops v times.
    !pgi$ unroll = m:v

The directives unroll and nounroll only apply if-⁠Munroll is selected on the command line.

4.1.20. vector (novector)

The directive or pragma novector disables vectorization. The directive or pragma vector re-enables vectorization after a previous novector directive. The directives vector and novector only apply if -⁠Mvect has been selected on the command line.

4.1.21. vintr (novintr)

The directive or pragma novintr directs the vectorizer to disable recognition of vector intrinsics. The directive vintr is re-enables recognition of vector intrinsics after a previous novintr directive. The directives vintr and novintr only apply if -⁠Mvect has been selected on the command line.

4.2. Prefetch Directives and Pragmas

Prefetch instructions can increase the speed of an application substantially by bringing data into cache so that it is available when the processor needs it. The PGI prefetch directive takes the form:

The syntax of a prefetch directive in Fortran is as follows:

!$mem prefetch <var1>[,<var2>[,...]]

where <varn> is any valid variable, member, or array element reference.

The syntax of a prefetch pragma in C/C++ is as follows:

#pragma mem prefetch <var1>[,<var2>[,...]]

where <varn is any valid variable, member, or array element reference.

For examples on how to use the prefetch directive or pragma, refer to the Prefetch Directives and Pragmas section of the PGI Compiler User's Guide.

4.3. !$PRAGMA C

When programs are compiled using one of the PGI Fortran compilers on Linux systems, an underscore is appended to Fortran global names, including names of functions, subroutines, and common blocks. This mechanism distinguishes Fortran name space from C/C++ name space.

IGNORE_TKR Directive

This directive indicates to the compiler to ignore the type, kind, and/or rank (/TKR/) of the specified dummy arguments in an interface of a procedure. The compiler also ignores the type, kind, and/or rank of the actual arguments when checking all the specifics in a generic call for ambiguities.

4.4.1. IGNORE_TKR Directive Syntax

The syntax for the IGNORE_TKR directive is this:

!DIR$ IGNORE_TKR [ [(<letter>) <dummy_arg>] ... ]
<letter>
is one or any combination of the following:
T – type K – kind R – rank

For example, KR indicates to ignore both kind and rank rules and TKR indicates to ignore the type, kind, and rank arguments.

<dummy_arg>
if specified, indicates the dummy argument for which TKR rules should be ignored. If not specified, TKR rules are ignored for all dummy arguments in the procedure that contains the directive.

4.4.2. IGNORE_TKR Directive Format Requirements

The following rules apply to this directive:

  • IGNORE_TKR must not specify dummy arguments that are allocatable, Fortran 90 pointers, or assumed-shape arrays.
  • IGNORE_TKR may appear in the body of an interface block or in the body of a module procedure, and may specify dummy argument names only.
  • IGNORE_TKR may appear before or after the declarations of the dummy arguments it specifies.
  • If dummy argument names are specified, IGNORE_TKR applies only to those particular dummy arguments.
  • If no dummy argument names are specified, IGNORE_TKR applies to all dummy arguments except those that are allocatable objects, Fortran 90 pointers, or assumed-shape arrays.

4.4.3. Sample Usage of IGNORE_TKR Directive

Consider this subroutine fragment:

subroutine example(A,B,C,D)
!DIR$ IGNORE_TKR A, (R) B, (TK) C, (K) D

Table 15 indicates which rules are ignored for which dummy arguments in the preceding sample subroutine fragment:

Table 15. IGNORE_TKR Example
Dummy Argument Ignored Rules
A Type, Kind and Rank
B Only rank
C Type and Kind
D Only Kind

Notice that no letters were specified for A, so all type, kind, and rank rules are ignored.

5. Runtime Environment

This section describes the programming model supported for compiler code generation, including register conventions and calling conventions for OpenPOWER processor-based systems.

Note: In this section we sometimes refer to word, halfword, and double word. The equivalent byte information is word (4 byte), halfword (2 byte), and double word (8 byte).

5.1. Linux Programming Model

This section defines compiler and assembly language conventions for the use of certain aspects of an OpenPOWER processor running a linux operating system. These standards must be followed to guarantee that compilers, application programs, and operating systems written by different people and organizations will work together. The conventions supported by the PGCC ANSI C compiler implement the application binary interface (ABI) as defined in the OpenPOWER for Linux Supplement, Power Architecture 64-Bit ELF V2 ABI Specification, listed in the Related Publications section in the Preface.

5.1.1. Function Calling Sequence

This section describes the standard function calling sequence, including the stack frame, register usage, and parameter passing.

Register Usage Conventions

The following table defines the standard for register allocation. The OpenPOWER Architecture provides a variety of registers. All the general purpose registers, vector scalar registers, and vector registers are visible to all procedures in a running program.

In the 64-bit OpenPOWER Architecture, there are always 32 general-purpose registers, each 64 bits wide. Throughout this document the symbol rN is used, where N is a register number, to refer to general-purpose register N.

Table 16. Register Allocation
Type Name Preservation Rules Purpose
General r0 Volatile Optional use in function linkage. Used in function prologues.
r1 Nonvolatile Stack frame pointer.
r2 Nonvolatile(1) TOC pointer.
r3–r10 Volatile Parameter and return values.
r11 Volatile Optional use in function linkage. Used as an environment pointer in languages that require environment pointers.
r12 Volatile Optional use in function linkage. Function entry address at the global entry point.
r13 Reserved Thread pointer.
r14–r31(2) Nonvolatile Local variables.
Floating-point f0 Volatile Local variables.
f1–f13 Volatile Used for parameter passing and return values of binary float types.
f14–f31 Nonvolatile Local variables.
Vector v0–v1 Volatile Local variables.
v2–v13 Volatile Used for parameter passing and return values.
v14–v19 Volatile Local variables.
v20–v31 Nonvolatile Local variables.

(1) Register r2 is nonvolatile with respect to calls between functions in the same compilation unit. It is saved and restored by code inserted by the linker resolving a call to an external function.

(2) If a function needs a frame pointer, assigning r31 to the role of the frame pointer is recommended.

In OpenPOWER-compliant processors, floating-point and vector functions are implemented using a unified vector-scalar model. As shown in Figure 3 and Figure 4, there are 64 vector-scalar registers; each is 128 bits wide.

The vector-scalar registers can be addressed with vector-scalar instructions, for vector and scalar processing of all 64 registers, or with the “classic” Power floating-point instructions to refer to a 32-register subset of 64 bits per register. They can also be addressed with VMX instructions to refer to a 32-register subset of 128-bit wide registers.

Figure 3. Floating-point Registers as Part of Vector Scalar Registers
Showing how floating-point registers take up a                     quarter portion of the vector scalar space.

Figure 4. Vector Registers as Part of Vector Scalar Registers
Showing how vector registers take up a half                     portion of the vector scalar space.

The classic floating-point repertoire consists of 32 floating-point registers, each 64 bits wide, and an associated special-purpose register to provide floating-point status and control. Throughout this document, the symbol fN is used, where N is a register number, to refer to floating-point register N.

For the purpose of function calls, the right half of VSX registers, corresponding to the classic floating-point registers (that is, vsr0–vsr31), is volatile.

Single-precision and double-precision shall be passed in the floating-point registers. Single-precision decimal floating-point shall occupy the lower half of a floating-point register. When a floating-point register is skipped during input parameter allocation, words in the corresponding GPR or memory doubleword in the parameter list are not skipped.

The OpenPOWER vector-category instruction repertoire provides the ability to reference 32 vector registers, each 128 bits wide, of the vector-scalar register file, and a special-purpose register VSCR. Throughout this document, the symbol vN is used, where N is a register number, to refer to vector register N.

Parameters in the long double format with a pair of two double-precision floating-point values shall be passed in two successive floating-point registers.

If only one value can be passed in a floating-point register, the second parameter will be passed in a GPR or in memory in accordance with the parameter passing rules for structure aggregates.

In addition to the registers, each function has a frame on the run-time stack. This stack grows downward from high addresses. Figure 5 shows the stack frame organization, in which the white areas indicate an optional save area of the stack frame. For a description of the optional save areas described by this ABI, see Optional Save Areas.

Figure 5. Stack Frame Organization
Relative layout of an allocated stack frame                     following a nonleaf function call, where the                     stack pointer points to the back-chain word                     of the caller's stack frame.

Key points concerning the stack frame:

  • The stack shall be quadword aligned.
  • The minimum stack frame size shall be 32 bytes. A minimum stack frame consists of the first 4 doublewords (back-chain doubleword, CR save word and reserved word, LR save doubleword, and TOC pointer doubleword), with padding to meet the 16-byte alignment requirement.
  • There is no maximum stack frame size defined.
  • Padding shall be added to the Local Variable Space of the stack frame to maintain the defined stack frame alignment.
  • The stack pointer, r1, shall always point to the lowest address doubleword of the most recently allocated stack frame.
  • The stack shall start at high addresses and grow downward toward lower addresses.
  • The lowest address doubleword (the back-chain word in Figure 5) shall point to the previously allocated stack frame when a back chain is present. As an exception, the first stack frame shall have a value of 0 (NULL).
  • If required, the stack pointer shall be decremented in the called function's prologue and restored in the called function's epilogue.
  • The stack pointer shall be updated atomically so that, at all times, it points to a valid back-chain doubleword if a back chain is maintained.
  • Before a function calls any other functions, it shall save the value of the LR register into the LR save doubleword of the caller's stack frame.

Back Chain Doubleword

When a back chain is not present, alternate information compatible with the ABI unwind framework to unwind a stack must be provided by the compiler, for all languages, regardless of language features. A compiler that does not provide such system-compatible unwind information must generate a back chain. All compilers shall generate back chain information by default, and default libraries shall contain a back chain.

CR Save Word

If a function changes the value in any nonvolatile field of the condition register, it shall first save at least the value of those nonvolatile fields of the condition register, to restore before function exit. The caller frame CR Save Word may be used as the save location. This location in the current frame may be used as temporary storage, which is volatile over function calls.

Reserved Word

This word is reserved for system functions. Modifications of the value contained in this word are prohibited unless explicitly allowed by future ABI amendments.

LR Save Doubleword

If a function changes the value of the link register, it must first save the old value to restore before function exit. The caller frame LR Save Doubleword may be used as the save location. This location in the current frame may be used as temporary storage, which is volatile over a function call.

TOC Pointer Doubleword

If a function changes the value of the TOC pointer register, it shall first save it in the TOC pointer doubleword.

Optional Save Areas

This ABI provides a stack frame with a number of optional save areas. These areas are always present, but may be of size 0. This section indicates the relative position of these save areas in relation to each other and the primary elements of the stack frame.

Because the back-chain word of a stack frame must maintain quadword alignment, a reserved word is introduced above the CR save word to provide a quadword-aligned minimal stack frame and align the doublewords within the fixed stack frame portion at doubleword boundaries.

An optional alignment padding to a quadword-boundary element might be necessary above the Vector Register Save Area to provide 16-byte alignment, as shown in Figure 5.

Floating-Point Register Save Area

If a function changes the value in any nonvolatile floating-point register fN, it shall first save the value in fN in the Floating-Point Register Save Area and restore the register upon function exit.

The Floating-Point Register Save Area is always doubleword aligned. The size of the Floating-Point Register Save Area depends upon the number of floating-point registers that must be saved. If no floating-point registers are to be saved, the Floating-Point Register Save Area has a zero size.

General-Purpose Register Save Area

If a function changes the value in any nonvolatile general-purpose register rN, it shall first save the value in rN in the General-Purpose Register Save Area and restore the register upon function exit.

The General-Purpose Register Save Area is always doubleword aligned. The size of the General-Purpose Register Save Area depends upon the number of general registers that must be saved. If no general-purpose registers are to be saved, the General-Purpose Register Save Area has a zero size.

Vector Register Save Area

If a function changes the value in any nonvolatile vector register vN, it shall first save the value in vN in the Vector Register Save Area and restore the register upon function exit.

The Vector Register Save Area is always quadword aligned. If necessary to ensure suitable alignment of the vector save area, a padding doubleword may be introduced between the vector register and General- Purpose Register Save Areas, and/or the Local Variable Space may be expanded to the next quadword boundary. The size of the Vector Register Save Area depends upon the number of vector registers that must be saved. It ranges from 0 bytes to a maximum of 192 bytes (12 × 16). If no vector registers are to be saved, the Vector Register Save Area has a zero size.

Local Variable Space

The Local Variable Space is used for allocation of local variables. The Local Variable Space is located immediately above the Parameter Save Area, at a higher address. There is no restriction on the size of this area.

Note: Sometimes a register spill area is needed. It is typically positioned above the Local Variable Space.

The Local Variable Space also contains any parameters that need to be assigned a memory address when the function's parameter list does not require a save area to be allocated by the caller.

Parameter Save Area

The Parameter Save Area shall be allocated by the caller for function calls unless a prototype is provided for the callee indicating that all parameters can be passed in registers. (This requires a Parameter Save Area to be created for functions where the number and type of parameters exceeds the registers available for parameter passing in registers, for those functions where the prototype contains an ellipsis to indicate a variadic function, and functions are declared without prototype.)

When the caller allocates the Parameter Save Area, it will always be automatically quadword aligned because it must always start at SP + 32. It shall be at least 8 doublewords in length. If a function needs to pass more than 8 doublewords of arguments, the Parameter Save Area shall be large enough to spill all register-based parameters and to contain the arguments that the caller stores in it.

The calling function cannot expect that the contents of this save area are valid when returning from the callee.

The Parameter Save Area, which is located at a fixed offset of 32 bytes from the stack pointer, is reserved in each stack frame for use as an argument list when an in-memory argument list is required. For example, a Parameter Save Area must be allocated by the caller when calling functions with the following characteristics:

  • Prototyped functions where the parameters cannot be contained in the parameter registers
  • Prototyped functions with variadic arguments
  • Functions without a suitable declaration available to the caller to determine the called function's characteristics (for example, functions in C without a prototype in scope).

Under these circumstances, a minimum of 8 doublewords are always reserved. The size of this area must be sufficient to hold the longest argument list being passed by the function that owns the stack frame. Although not all arguments for a particular call are located in storage, when an in-memory parameter list is required, consider the parameters to be forming a list in this area. Each argument occupies one or more doublewords.

More arguments might be passed than can be stored in the parameter registers. In that case, the remaining arguments are stored in the Parameter Save Area. The values passed on the stack are identical to the values placed in registers. Therefore, the stack contains register images for the values that are not placed into registers.

This ABI uses a simple va_list type for variable lists to point to the memory location of the next parameter. Therefore, regardless of type, variable arguments must always be in the same location so that they can be found at runtime. The first 8 doublewords are located in general registers r3–r10. Any additional doublewords are located in the stack Parameter Save Area. Alignment requirements such as those for vector types may require the va_list pointer to first be aligned before accessing a value.

Follow these rules for parameter passing:

  • Map each argument to enough doublewords in the Parameter Save Area to hold its value.
  • Map single-precision floating-point values to the least-significant word in a single doubleword.
  • Map double-precision floating-point values to a single doubleword.
  • Map simple integer types (char, short, int, long, enum) to a single doubleword. Sign or zero extend values shorter than a doubleword to a doubleword based on whether the source data type is signed or unsigned.
  • When 128-bit integer types are passed by value, map each to two consecutive GPRs, two consecutive doublewords, or a GPR and a doubleword. The required alignment of int128 data types is 16 bytes. Therefore, by-value parameters must be copied to a new location in the local variable area of the callee's stack frame before the address of the type can be provided (for example, using the address-of operator, or when the variable is to be passed by reference), when the incoming parameter is not aligned at a 16-byte boundary.
  • Map long double to two consecutive doublewords. The required alignment of long double data types is 16 bytes. Therefore, by-value parameters must be copied to a new location in the local variable area of the callee's stack frame before the address of the type can be provided (for example, using the address-of operator, or when the variable is to be passed by reference), when the incoming parameter is not aligned at a 16-byte boundary.
  • Map complex floating-point and complex integer types as if the argument was specified as separate real and imaginary parts.
  • Map pointers to a single doubleword.
  • Map vectors to a single quadword, quadword aligned. This might result in skipped doublewords in the Parameter Save Area.
  • Map fixed-size aggregates and unions passed by value to as many doublewords of the Parameter Save Area as the value uses in memory. Align aggregates and unions as follows:
    • Aggregates that contain qualified floating-point or vector arguments are normally aligned at the alignment of their base type. For more information about qualified arguments, see Parameter Passing in Registers.
    • Other aggregates are normally aligned in accordance with the aggregate's defined alignment.
    • The alignment will never be larger than the stack frame alignment (16 bytes).

    This might result in doublewords being skipped for alignment. When a doubleword in the Parameter Save Area (or its GPR copy) contains at least a portion of a structure, that doubleword must contain all other portions mapping to the same doubleword. (That is, a doubleword can either be completely valid, or completely invalid, but not partially valid and invalid, except in the last doubleword where invalid padding may be present.)

  • Pad an aggregate or union smaller than one doubleword in size so that it is in the least-significant bits of the doubleword. Pad all others, if necessary, at their tail. Variable size aggregates or unions are passed by reference.
  • Map other scalar values to the number of doublewords required by their size.
  • Future data types that have an architecturally defined quadword-required alignment will be aligned at a quadword boundary.
  • If the callee has a known prototype, arguments are converted to the type of the corresponding parameter when loaded to their parameter registers or when being mapped into the Parameter Save Area. For example, if a long is used as an argument to a float double parameter, the value is converted to double precision and mapped to a doubleword in the Parameter Save Area.

Protected Zone

The 288 bytes below the stack pointer are available as volatile program storage that is not preserved across function calls. Interrupt handlers and any other functions that might run without an explicit call must take care to preserve a protected zone, also referred to as the red zone, of 512 bytes that consists of:

  • The 288-byte volatile program storage region that is used to hold saved registers and local variables
  • An additional 224 bytes below the volatile program storage region that is set aside as a volatile system storage region for system functions

If a function does not call other functions and does not need more stack space than is available in the volatile program storage region (that is, 288 bytes), it does not need to have a stack frame. The 224-byte volatile system storage region is not available to compilers for allocation to saved registers and local variables.

Parameter Passing in Registers

For the OpenPOWER Architecture, it is more efficient to pass arguments to functions in registers rather than through memory. For more information about passing parameters through memory, see Parameter Save Area under Optional Save Areas. For the OpenPOWER ABI, the following parameters can be passed in registers:

  • Up to eight arguments can be passed in general-purpose registers r3–r10.
  • Up to thirteen qualified floating-point arguments can be passed in floating-point registers f1–f13 or up to twelve in vector registers v2–v13.
  • Up to thirteen single-precision or double-precision decimal floating-point arguments can be passed in floating-point registers f1–f13.
  • Up to six quad-precision decimal floating-point arguments can be passed in even-odd floating-point register pairs f2–f13.
  • Up to 12 qualified vector arguments can be passed in v2–v13.

A qualified floating-point argument corresponds to:

  • A scalar floating-point data type
  • Each member of a complex floating-point type
  • A member of a homogeneous aggregate of multiple like data types passed in up to eight floating-point registers

    A homogeneous aggregate can consist of a variety of nested constructs including structures, unions, and array members, which shall be traversed to determine the types and number of members of the base floating-point type. (A complex floating-point data type is treated as if two separate scalar values of the base type were passed.)

    Homogeneous floating-point aggregates can have up to four long double members or eight members of floating-point types. (Unions are treated as their largest member. For homogeneous unions, different union alternatives may have different sizes, provided that all union members are homogeneous with respect to each other.) They are passed in floating-point registers if parameters of that type would be passed in floating-point registers. They are passed in vector registers if parameters of that type would be passed in vector registers. They are passed as if each member was specified as a separate parameter.

A qualified vector argument corresponds to:

  • A vector data type
  • A member of a homogeneous aggregate of multiple like data types passed in up to eight vector registers
  • Any future type requiring 16-byte alignment (see Optional Save Areas) or processed in vector registers

    A homogeneous aggregate can consist of a variety of nested constructs including structures, unions, and array members, which shall be traversed to determine the types and number of members of the base vector type. Homogeneous vector aggregates with up to eight members are passed in up to eight vector registers as if each member was specified as a separate parameter. (Unions are treated as their largest member. For homogeneous unions, different union alternatives may have different sizes, provided that all union members are homogeneous with respect to each other.)

Note: Floating-point and vector aggregates that contain padding words and integer fields with a width of 0 should not be treated as homogeneous aggregates.

A homogeneous aggregate is either a homogeneous floating-point aggregate or a homogeneous vector aggregate. This ABI does not specify homogeneous aggregates for integer types.

Long double numbers in are passed using two successive floating-point registers. A floating-point register might be skipped to allocate an even/odd register pair when necessary. When a floating-point register is skipped, no corresponding memory word is skipped in the natural home location; that is, the corresponding GPR or memory doubleword in the parameter list.

All other aggregates are passed in consecutive GPRs, in GPRs and in memory, or in memory.

When a parameter is passed in a floating-point or vector register, a number of GPRs are skipped, in allocation order, commensurate to the size of the corresponding in-memory representation of the passed argument's type.

Each parameter is allocated to at least one doubleword.

Full doubleword rule:

When a doubleword in the Parameter Save Area (or its GPR copy) contains at least a portion of a structure, that doubleword must contain all other portions mapping to the same doubleword. (That is, a doubleword can either be completely valid, or completely invalid, but not partially valid and invalid, except in the last doubleword where invalid padding may be present.)

Long Double

Long double parameters are passed as if they were a struct consisting of separate double parameters.

Long double parameters shall be considered as a distinct type for the determination of homogeneous aggregates.

If fewer arguments are needed, the unused registers defined previously will contain undefined values on entry to the called function.

If there are more arguments than registers or no function prototype is provided, a function must provide space for all arguments in its stack frame. When this happens, only the minimum storage needed to contain all arguments (including allocating space for parameters passed in registers) needs to be allocated in the stack frame.

General-purpose registers r3–r10 correspond to the allocation of parameters to the first 8 doublewords of the Parameter Save Area. Specifically, this requires a suitable number of general-purpose registers to be skipped to correspond to parameters passed in floating-point and vector registers.

If a parameter corresponds to an unnamed parameter that corresponds to the ellipsis, a caller shall promote float values to double. If a parameter corresponds to an unnamed parameter that corresponds to the ellipsis, the parameter shall be passed in a GPR or in the Parameter Save Area.

If no function prototype is available, the caller shall promote float values to double and pass floating-point parameters in both available floating-point registers and in the Parameter Save Area. If no function prototype is available, the caller shall pass vector parameters in both available vector registers and in the Parameter Save Area. (If the callee expects a float parameter, the result will be incorrect.)

It is the callee's responsibility to allocate storage for the stored data in the local variable area. When the callee's parameter list indicates that the caller must allocate the Parameter Save Area (because at least one parameter must be passed in memory or an ellipsis is present in the prototype), the callee may use the preallocated Parameter Save Area to save incoming parameters.

Parameter Passing Register Selection Algorithm

The following algorithm describes where arguments are passed for the C language. In this algorithm, arguments are assumed to be ordered from left (first argument) to right. The actual order of evaluation for arguments is unspecified.

  • gr contains the number of the next available general-purpose register.
  • fr contains the number of the next available floating-point register.
  • vr contains the number of the next available vector register.
Note: The following types refer to the type of the argument as declared by the function prototype. The argument values are converted (if necessary) to the types of the prototype arguments before passing them to the called function.

If a prototype is not present, or it is a variable argument prototype and the argument is after the ellipsis, the type refers to the type of the data objects being passed to the called function.

  • INITIALIZE: If the function return type requires a storage buffer, set gr = 4; else set gr = 3.
    Set fr = 1
    Set vr = 2
  • SCAN: If there are no more arguments, terminate. Otherwise, allocate as follows based on the class of the function argument:
    switch(class(argument))
    
    integer:
    pointer:
    
        if gr > 10
            goto mem_argument
        pass (GPR, gr, argument);
        gr++
    
        break;
    
    aggregate:
        if (homogeneous(argument,float) and regs_needed(members(argument)) <= 8)
            n_fregs = n_fregs_for_type(member_type(argument,0))
            agg_size = members(argument * n_fregs
            reg_size = min(agg_size, 15-fr)
            pass(FPR,fr,first_n_DW(argument,reg_size)
            fr += reg_size;
            gr += size_in_DW (first_n_DW(argument,reg_size))
    
            if remaining_members
                argument = after_n_DW(argument,reg_size))
                goto gpr_struct
        break;
    
        if (homogeneous(argument,vector) and members(argument) <= 8)
            use_vrs:
                agg_size = members(argument)
                reg_size = min(agg_size, 14-vr)
                if (gr&1 = 0) // align vector in memory
                    gr++
                pass(VR,vr,first_n_elements(argument,reg_size);
                vr += reg_size
                gr += size_in_DW (first_n_elements(argument,reg_size)
    
                if remaining_members
                    argument = after_n_elements(argument,reg_size))
                    goto gpr_struct
    
        break;
    
        if gr > 10
            goto mem_argument
    
        size = size_in_DW(argument)
    
    gpr_struct:
        reg_size = min(size, 11-gr)
        pass (GPR, gr, first_n_DW (argument, reg_size));
        gr += size_in_DW (first_n_DW (argument, reg_size))
    
        if remaining_members
            argument = after_n_DW(argument,reg_size))
            goto mem_argument
    
        break;
    
    float:
    
    // float is passed in one FPR.
    // double is passed in one FPR.
    
        if (register_type_used (type (argument)) == vr)
            goto use_vr;
        if fr > 14
            goto mem_argument
    
        n_fregs = n_fregs_for_type(argument) // Assumes n_fregs_for_type == 2
                                             // for long double == 1 for float
                                             // or double
        pass(FPR,fr,argument)
        fr += n_fregs
        gr += size_in_DW(argument)
    
        break;
    
    vector:
        Use vr:
            if vr > 13
                goto mem_argument
    
            if (gr&1 = 0) // align vector in memory
                gr++
    
            pass(VR,vr,argument)
            vr ++
            gr += 2
    
            break;
    
    next argument;
    
    mem_argument:
        need_save_area = TRUE
        pass (stack, gr, argument)
        gr += size_in_DW(argument)
    
    next argument;

All complex data types are handled as if two scalar values of the base type were passed as separate parameters.

If the callee takes the address of any of its parameters, values passed in registers are stored to memory. It is the callee's responsibility to allocate storage for the stored data in the local variable area. When the callee's parameter list indicates that the caller must allocate the Parameter Save Area (because at least one parameter must be passed in memory, or an ellipsis is present in the prototype), the callee may use the preallocated Parameter Save Area to save incoming parameters. (If an ellipsis is present, using the preallocated Parameter Save Area ensures that all arguments are contiguous.) If the compilation unit for the caller contains a function prototype, but the callee has a mismatching definition, this may result in the wrong values being stored.

Note: If the declaration of a function that is used by the caller does not match the definition for the called function, corruption of the caller's stack space can occur.

Variable Argument Lists

C programs that are intended to be portable across different compilers and architectures must use the header file <stdarg.h> to deal with variable argument lists. This header file contains a set of macro definitions that define how to step through an argument list. The implementation of this header file may vary across different architectures, but the interface is the same.

C programs that do not use this header file for the variable argument list and assume that all the arguments are passed on the stack in increasing order on the stack are not portable, especially on architectures that pass some of the arguments in registers. The OpenPOWER Architecture is one of the architectures that passes some of the arguments in registers.

The parameter list may be zero length and is only allocated when parameters are spilled, when a function has unnamed parameters, or when no prototype is provided. When the Parameter Save Area is allocated, the Parameter Save Area must be large enough to accommodate all parameters, including parameters passed in registers.

Return Values

Functions that return a value shall place the result in the same registers as if the return value was the first named input argument to a function unless the return value is a nonhomogeneous aggregate larger than 2 doublewords or a homogeneous aggregate with more than eight registers.1 (Homogeneous aggregates are arrays, structs, or unions of a homogeneous floating-point or vector type and of a known fixed size.) Therefore, long double functions are returned in f1:f2.

Homogeneous floating-point or vector aggregate return values that consist of up to eight registers with up to eight elements will be returned in floating-point or vector registers that correspond to the parameter registers that would be used if the return value type were the first input parameter to a function.

Aggregates that are not returned by value are returned in a storage buffer provided by the caller. The address is provided as a hidden first input argument in general-purpose register r3.

Functions that return values of the following types shall place the result in register r3 as signed or unsigned integers, as appropriate, and sign extended or zero extended to 64 bits where necessary:

  • char
  • enum
  • short
  • int
  • long
  • pointer to any type
  • _Bool

5.1.2. Linux OpenPOWER Fortran Supplement

Sections A2.4.1 through A2.4.4 of the ABI for Linux define the Fortran supplement. The register usage conventions set forth in that document remain the same for Fortran.

Fortran Fundamental Types

Table 17. Linux OpenPOWER Fortran Fundamental Types
Fortran Type Size (bytes) Alignment (bytes)
INTEGER 4 4
INTEGER*1 1 1
INTEGER*2 2 2
INTEGER*4 4 4
INTEGER*8 8 8
LOGICAL 4 4
LOGICAL*1 1 1
LOGICAL*2 2 2
LOGICAL*4 4 4
LOGICAL*8 8 8
BYTE 1 1
CHARACTER*n n 1
REAL 4 4
REAL*4 4 4
REAL*8 8 8
DOUBLE PRECISION 8 8
COMPLEX 8 4
COMPLEX*8 8 4
COMPLEX*16 16 8
DOUBLE COMPLEX 16 8

A logical constant is one of:

  • .TRUE.
  • .FALSE.

The logical constants .TRUE. and .FALSE. are defined to be the four-byte values -1 and 0 respectively. A logical expression is defined to be .TRUE. if its least significant bit is 1 and .FALSE. otherwise.

Note that the value of a character is not automatically NULL-terminated.

Naming Conventions

By default, all globally visible Fortran symbol names (subroutines, functions, common blocks) are converted to lower-case. In addition, an underscore is appended to Fortran global names to distinguish the Fortran name space from the C/C⁠+⁠+ name space.

Argument Passing and Return Conventions

Arguments are passed by reference (i.e., the address of the argument is passed, rather than the argument itself). In contrast, C/C⁠+⁠+ arguments are passed by value.

When passing an argument declared as Fortran type CHARACTER, an argument representing the length of the CHARACTER argument is also passed to the function. This length argument is a four-byte integer passed by value, and is passed at the end of the parameter list following the other formal arguments. A length argument is passed for each CHARACTER argument; the length arguments are passed in the same order as their respective CHARACTER arguments.

A Fortran function, returning a value of type CHARACTER, adds two arguments to the beginning of its argument list. The first additional argument is the address of the area created by the caller for the return value; the second additional argument is the length of the return value. If a Fortran function is declared to return a character value of constant length, for example CHARACTER*4 FUNCTION CHF(), the second extra parameter representing the length of the return value must still be supplied.

A Fortran complex function returns its value in the same manner as complex functions.

Alternate return specifiers of a Fortran function are not passed as arguments by the caller. The alternate return function passes the appropriate return value back to the caller in r1.

The handling of the following Fortran 90 features is implementation-defined: internal procedures, pointer arguments, assumed-shape arguments, functions returning arrays, and functions returning derived types.

Inter-language Calling

Inter-language calling between Fortran and C/C⁠+⁠+ is possible if function/subroutine parameters and return values match types.

  • If a C/C⁠+⁠+ function returns a value, call it from Fortran as a function, otherwise, call it as a subroutine.
  • If a Fortran function has type CHARACTER, call it from C/C⁠+⁠+ as a void function.
  • If a Fortran subroutine has alternate returns, call it from C/C⁠+⁠+ as a function returning int; the value of such a subroutine is the value of the integer expression specified in the alternate RETURN statement.
  • If a Fortran subroutine does not contain alternate returns, call it from C/C⁠+⁠+ as a void function.

Fortran 2003 also provides a mechanism to support interoperability with C. This mechanism inclues the ISO_C_BINDING intrinsic module, binding labels, and the BIND attribute.

Table 18 provides the C/C⁠+⁠+ data type corresponding to each Fortran data type.

Table 18. Fortran and C/C⁠+⁠+ Data Type Compatibility
Fortran Type C/C++ Type Size (bytes)
CHARACTER*n x char x[n] n
REAL x float x 4
REAL*4 x float x 4
REAL*8 x double x 8
DOUBLE PRECISION x double x 8
INTEGER x int x 4
INTEGER*1 x signed char x 1
INTEGER*2 x short x 2
INTEGER*4 x int x 4
INTEGER*8 x long x, or long long x 8
LOGICAL x int x 4
LOGICAL*1 x char x 1
LOGICAL*2 x short x 2
LOGICAL*4 x int x 4
LOGICAL*8 x long x, or long long x 8
Table 19. Fortran and C/C++ Representation of the COMPLEX Type
Fortran Type (lower case) C/C++ Type Size (bytes)
complex x struct {float r,i;} x; 8
  float complex x;  
complex*8 x struct {float r,i;} x; 8
  float complex x; 8
double complex x struct {double dr,di;} x; 16
  double complex x; 16
complex *16 x struct {double dr,di;} x; 16
  double complex x; 16
Note: For C/C++, the complex type implies C99 or later.

Arrays

C/C++ arrays and Fortran arrays use different default initial array index values. By default, C/C⁠+⁠+ arrays start at 0 and Fortran arrays start at 1. A Fortran array can be declared to start at zero.

Another difference between Fortran and C/C⁠+⁠+ arrays is the storage method used. Fortran uses column-major order and C/C⁠+⁠+ use row-major order. For one-dimensional arrays, this poses no problems. For two-dimensional arrays, where there are an equal number of rows and columns, row and column indexes can simply be reversed. Inter-language function mixing is not recommended for arrays other than single dimensional arrays and square two-dimensional arrays.

Structures, Unions, Maps, and Derived Types

Fields within Fortran structures and derived types, and multiple map declarations within a Fortran union, conform to the same alignment requirements used by C structures.

Common Blocks

A named Fortran common block can be represented in C/C⁠+⁠+ by a structure whose members correspond to the members of the common block. The name of the structure in C/C⁠+⁠+ must have the added underscore.

For example, the Fortran common block:

INTEGER I, J
COMPLEX C
DOUBLE COMPLEX CD
DOUBLE PRECISION D
COMMON /COM/ i, j, c, cd, d

is represented in C with the following equivalent:

extern struct {
    int i;
    int j;
    struct {float real, imag;} c;
    struct {double real, imag;} cd;
    double d;
} com_;

and in C++ with the following equivalent:

extern "C" struct {
    int i;
    int j;
    struct {float real, imag;} c;
    struct {double real, imag;} cd;
    double d;
} com_;
Note: The compiler-provided name of the BLANK COMMON block is implementation specific.

Calling Fortran COMPLEX and CHARACTER functions from C/C⁠+⁠+ is not as straightforward as calling other types of Fortran functions. Additional arguments must be passed to the Fortran function by the C/C⁠+⁠+ caller. A Fortran COMPLEX function returns its value in memory; the first argument passed to the function must contain the address of the storage for this value. A Fortran CHARACTER function adds two arguments to the beginning of its argument list. The following example of calling a Fortran CHARACTER function from C/C⁠+⁠+ illustrates these caller-provided extra parameters:

CHARACTER*(*) FUNCTION CHF(C1, I)
CHARACTER*(*) C1
INTEGER I
END
extern void chf_();
char tmp[10];
char c1[9];
int i;
chf_(tmp, 10, c1, &i, 9);

The extra parameters tmp and 10 are supplied for the return value, while 9 is supplied as the length of c1.

6. C++ Dialect Supported

The PGC++ compiler accepts the C++ language of the ISO/IEC 14882:2003 standard, the ISO/IEC 14882:2011 standard, plus substantially all GNU C++ extensions.

Command-line options provide full support of many C++ variants, including strict standard conformance. PGC++ provides command line options that enable the user to specify whether anachronisms and/or cfront 2.1/3.0 compatibility features should be accepted. C++11 and C++14 are also supported via command line options.

6.1. Extensions Accepted in Normal C++ Mode

The following extensions are accepted in all modes, except when strict ANSI violations are diagnosed as errors, described in the -⁠A option:

  • A friend declaration for a class may omit the class keyword:
    class A {
        friend B; // Should be "friend class B"
    };
  • Constants of scalar type may be defined within classes:
    class A {
        const int size = 10; 
        int a[size]; 
    };
  • In the declaration of a class member, a qualified name may be used:
    struct A{
        int A::f(); // Should be int f();
    }
  • The preprocessing symbol c_plusplus is defined in addition to the standard __cplusplus.
  • An assignment operator declared in a derived class with a parameter type matching one of its base classes is treated as a "default'' assignment operator—that is, such a declaration blocks the implicit generation of a copy assignment operator. (This is cfront behavior that is known to be relied upon in at least one widely used library.)

    Here's an example:

    struct A { } ;
    struct B : public A {
        B& operator=(A&);
    };
  • By default, as well as in cfront-compatibility mode, there will be no implicit declaration of B::operator=(const B&), whereas in strict-ANSI mode B::operator=(A&) is not a copy assignment operator and B::operator=(const B&) is implicitly declared.
  • Implicit type conversion between a pointer to an extern "C" function and a pointer to an extern "C++" function is permitted. Here’s an example:
    extern "C" void f();  // f's type has extern "C" linkage
    void (*pf) ()         // pf points to an extern "C++" function  = &f;
                          // error unless implicit conv is allowed

6.2. cfront 2.1 Compatibility Mode

The following extensions are accepted in cfront 2.1 compatibility mode in addition to the extensions listed in the following section. These things were corrected in the 3.0 release of cfront:

  • The dependent statement of an if, while, do-while, or for is not considered to define a scope. The dependent statement may not be a declaration. Any objects constructed within the dependent statement are destroyed at exit from the dependent statement.
  • Implicit conversion from integral types to enumeration types is allowed.
  • A non-const member function may be called for a const object. A warning is issued.
  • A const void * value may be implicitly converted to a void * value, e.g., when passed as an argument.
  • When, in determining the level of argument match for overloading, a reference parameter is initialized from an argument that requires a non-class standard conversion, the conversion counts as a user-defined conversion. (This is an outright bug, which unfortunately happens to be exploited in some class libraries.)
  • When a builtin operator is considered alongside overloaded operators in overload resolution, the match of an operand of a builtin type against the builtin type required by the builtin operator is considered a standard conversion in all cases (e.g., even when the type is exactly right without conversion).
  • A reference to a non-const type may be initialized from a value that is a const-qualified version of the same type, but only if the value is the result of selecting a member from a const class object or a pointer to such an object.
  • A cast to an array type is allowed; it is treated like a cast to a pointer to the array element type. A warning is issued.
  • When an array is selected from a class, the type qualifiers on the class object (if any) are not preserved in the selected array. (In the normal mode, any type qualifiers on the object are preserved in the element type of the resultant array.)
  • An identifier in a function is allowed to have the same name as a parameter of the function. A warning is issued.
  • An expression of type void may be supplied on the return statement in a function with a void return type. A warning is issued.
  • cfront has a bug that causes a global identifier to be found when a member of a class or one of its base classes should actually be found. This bug is not emulated in cfront compatibility mode.
  • A parameter of type "const void *'' is allowed on operator delete; it is treated as equivalent to "void *".
  • A period (".") may be used for qualification where "::" should be used. Only "::'' may be used as a global qualifier. Except for the global qualifier, the two kinds of qualifier operators may not be mixed in a given name (i.e., you may say A::B::C or A.B.C but not A::B.C or A.B::C). A period may not be used in a vacuous destructor reference nor in a qualifier that follows a template reference such as A<T>::B.
  • cfront 2.1 does not correctly look up names in friend functions that are inside class definitions. In this example function f should refer to the functions and variables (e.g., f1 and a1) from the class declaration. Instead, the global definitions are used.
    int a1;
    int e1;
    void f1();
    class A {
       int a1;
        void f1();
        friend void f()
        {
            int i1 = a1;  // cfront uses global a1
            f1();         // cfront uses global f1
        }
    };
  • Only the innermost class scope is (incorrectly) skipped by cfront as illustrated in the following example.
    int a1;
    int b1;
    struct A {
        static int a1;
        class B {
            static int b1;
            friend void f()
            {
                int i1 = a1;  // cfront uses A::a1
                int j1 = b1;  // cfront uses global b1
            }
        };
    };
  • operator= may be declared as a nonmember function. (This is flagged as an anachronism by cfront 2.1)
  • A type qualifier is allowed (but ignored) on the declaration of a constructor or destructor. For example:
    class A {
        A() const;  // No error in cfront 2.1 mode
    };

6.3. cfront 2.1/3.0 Compatibility Mode

The following extensions are accepted in both cfront 2.1 and cfront 3.0 compatibility mode (i.e., these are features or problems that exist in both cfront 2.1 and 3.0):

  • Type qualifiers on this parameter may to be dropped in contexts such as this example:
    struct A {
        void f() const;
    };
    void (A::*fp)() = &A::f;

    This is actually a safe operation. A pointer to a const function may be put into a pointer to non-const, because a call using the pointer is permitted to modify the object and the function pointed to will actually not modify the object. The opposite assignment would not be safe.

  • Conversion operators specifying conversion to void are allowed.
  • A nonstandard friend declaration may introduce a new type. A friend declaration that omits the elaborated type specifier is allowed in default mode, but in cfront mode the declaration is also allowed to introduce a new type name.
    struct A {
        friend B;
    };
  • The third operator of the ? operator is a conditional expression instead of an assignment expression.
  • A reference to a pointer type may be initialized from a pointer value without use of a temporary even when the reference pointer type has additional type qualifiers above those present in the pointer value. For example,
    int *p;  
    const int *&r = p;
    // No temporary use
  • A reference may be initialized with a null.

6.4. Extensions accepted in GNU compatibility mode ( pgc++ )

New GNU C++ features are added as needed, with priority given to features used in system headers. Because the GNU compiler frequently changes behavior between releases, PGC++ is configured to emulate the specific release currently on the user's system. The most recent versions of GCC implement some C++14 features that the front end does not yet implement.

A few GCC extensions that are likely not going to be supported in the foreseeable future are these:

  • The forward declaration of function parameters (so they can participate in variable-length array parameters).
  • GNU-style complex integral types (complex floating-point types are supported)
  • Nested functions
  • Local structs with variable-length array fields. Such fields are treated (with a warning) as zero-length arrays.

6.5. C++11 Language Features Accepted

The following features added in the C++11 standard are enabled in C++11 mode. This mode can be combined with the option for strict standard conformance. Several of these features are also enabled in default (nonstrict) C++ mode.

  • A ‘right shift token’ (>>) can be treated as two closing angle brackets. For example:
    template<typename T> struct S {};
    S<S<int>> s;  // Okay.
    // No whitespace needed between closing angle brackets.
  • The static_;assert construct is supported. For example:
    template<typename T> struct S {
        static_;assert(sizeof(T) > 1, "Type T too small");
    };
    S<char[2]> s1;  // Okay.
    S<char> s2;     // Instantiation error due to failing static_;assert
  • The friend class syntax is extended to allow nonclass types as well as class types expressed through a typedef or without an elaborated type name. For example:
    typedef struct S ST;
    class C {
        friend S;        // Okay (requires S to be in scope).
        friend ST;       // Okay (same as "friend S;").
        friend int;      // Okay (no effect).
        friend S const;  // Error: cv-qualifiers cannot appear directly.
    };
  • Mixed string literal concatenations are accepted, a feature carried over from C99 preprocessor extensions. For example:
    wchar_;t *str = "a" L"b";  // Okay, same as L"ab".
  • Variadic macros and empty macro arguments are accepted, as in C99.
  • In function bodies, the reserved identifier _;_;func_;_; refers to a predefined array containing a string representing the function’s name (a feature carried over from C99).
  • A trailing comma in the definition of an enumeration type is silently accepted (a feature carried over from C99):
    enum E { e, };
  • The type long long is accepted. Unsuffixed integer literals that cannot be represented by type long, but could potentially be represented by type unsigned long, have type long long instead (this matches C99, but not the treatment of the long long extension in C89 or default C++ mode).
  • An explicit instantiation directive may be prefixed with the extern keyword to suppress the instantiation of the specified entity.
  • The keyword typename followed by a qualified-id can appear outside a template declaration.
    struct S { struct N {}; };
    typename S::N *p;  // Silently accepted in C++11 mode.
  • The keyword auto can be used as a type specifier in the declaration of a variable or reference. In such cases, the actual type is deduced from the associated initializer. This feature can be used for variable declarations, for inclass declarations of static const members, and for new-expressions.
    auto x = 3.0;      // Same as "double x = 3.0;"
    auto p = new auto(x);         // Same as "double *p = new double(x);"
    struct S {
        static auto const m = 3;  // Same as "static int const m = 3;"
    };

    By default, auto is no longer accepted as a storage class specifier (but an option is available to re-enable it).

  • The keyword decltype is supported: It allows types to be described in terms of expressions. For example:
    template<typename T> struct S {
        decltype(f(T())) *p;  // A pointer to the return type of f.
    };
  • The constraints on the code points implied by universal character names (UCNs) are slightly different: UCNs for surrogate code points (0xD000 through 0xDFFF) are never permitted, and UCN corresponding to control characters or to characters in the basic source character set are permitted in string literals.
  • Scoped enumeration types (defined with the keyword sequence enum class) and explicit underlying integer types for enumeration types are supported. For example:
    enum class Primary { red, green, blue };
    enum class Danger { green, yellow, red }; // No conflict on "red".
    enum Code: unsigned char { yes, no, maybe };
    void f() {
        Primary p = Primary::red; // Enum-qualifier is required to access
                                  // scoped enumerator filepaths.
        Code c = Code::maybe;     // Enum qualifier is allowed (but not required)
    }                             // for unscoped enumeration types.
  • Lambdas are supported. For example:
    template<class F> int z(F f) { return f(0); }
    int g() {
        int v = 7;
        return z([v](int x)->int { return x+v; });
    }
  • The C99-style _;Pragma operator is supported.
  • Rvalue references are supported. For example:
    int f(int);
    int &&rr = f(3);
  • Functions can be ‘deleted’. For example:
    int f(int) = delete;
    short f(short);
    int x = f(3);         // Error: selected function is deleted.
    int y = f((short)3);  // Okay.
  • Special member functions can be explicitly ‘defaulted’ (i.e., given a default definition). For example:
    struct S { S(S const&) = default; };
    struct T { T(T const&); };
    T::T(T const&) = default;
  • The operand of sizeof, typeid, or decltype can refer directly to a non-static data member of a class without using a member access expression. For example:
    struct S { 
        int i;
    };
    decltype(S::i) j = sizeof(S;;i);
  • The keyword nullptr, conventionally known by its standard typedef std::nullptr_;t, can be used as both a null pointer and a null pointer-to-member filepath. Variables and other expressions whose type is that of the nullptr keyword can also be used as null pointer(-to-member) filepaths, although they are only filepath expressions if they wotherwise would be. For example:
    #include <cstddef>  // to get std::nullptr_;t
    struct S { };
    template <int *> struct X { };
    std::nullptr_;t null();
    void f()  {
        void *p = nullptr      // Initializes p to null pointer
        int S::* mp = nullptr  // Initializes mp to null ptr-to-member
        p = null();            // Sets p to null pointer
        X<nullptr> xnull0;  // Instantiates X with null int * value
        x<null()> xnull1    // Error: templeate argument not a
                               // filepath expression
    }
  • Attributes delimited by double square brackets ([[...]]) are accepted in declarations. The standard attributes noreturn and carries_;dependency are supported. For example:
    [[noreturn]] void f();
  • The context-sensitive keyword final is accepted on class types, to indicate they cannot be derived from, and on virtual member functions, to indicate they cannot be overridden. The context-sensitive keyword override can be specified on virtual member functions to assert that they override a corresponding base class member.
  • Alias and alias template declarations are supported. For example:
    using X = int;
    X x;           // equivalent to `int x'
    template <typename T> using Y = T*
    Y<int> yi;  // equivalent to `int* yi'
  • Variadic templates are supported. For example:
    template<class ...T> void f(T ...args)  {
        int i = sizeof...(args);
    }
    int main()  {
        f(1, 2, 3, 4);
    }
  • U-literals as well as the char16_;t and char32_;t keywords are supported. For example:
    char16_;t *str = U'A 16-bit character string';
    char32_;t ch = U'\U00012345';  // A 32-bit character string literal
  • Substitution Failure is Not An Error (SFINAE) for expressions. Many errors in expression that arise during the substitution of template parameters in function templates are now treated as deduction failures rather than definite errors. This approach may result in a valid program if another (overloaded) function template allows the substitution. In the original C++ standard (1998, 2003) SFINAE was mostly limited to simple type substitutions.
  • Access checking of names used as base classes is done in the context of the class being defined. For example:
    class B {protected: class N {} };
    class D: B;;N, B {};   // now allowed
  • Inline namespaces are supported. For example:
    namespace N  {
        template <class T> struct A {};
        template <class T> void g(T){}
        inline namespace M  {
            template <class T> void f(T){}
            template <> void f(A,int>);
            struct B;
        }
    }
    template <> void N;;f(a<int>){}  // specialized as if member of N
    struct N:: B {};         // defined as if member of N
    int main()   {
        N::A<int> na;
        f(na);               // argument dependent lookup finds N::M::f
        g(na);               // argument dependent lookup finds N::g
        N::B nb;
        f(nb);               // argument dependent lookup finds N::M::f
        g(nb);               // argument dependent lookup finds N::g
    }
  • Initializer lists are supported. These are brace-enclosed lists used as variable initializes and call arguments, and in casts, mem-initializers, default arguments, range-based ‘for’ statements, and return statements. For example:
    struct A { int a1; double a2; };
    struct B { B(int, double); };
    A a{1, 2.0}
    B b{1, 2.0};
    B b2 = B{1, 2.0};
  • The noexcept specifier and operator are supported. For example:
    void f(int) noexcept;       // never throws
    const int version = 5;
    void f(float) noexcept(version >=;5);  // does not throw if expr true
    int main()  {
        int arr[noexcept(f(1.0f))];        // operator is true if expression
                                           // cannot throw, so true in this case
    }

    In strict mode, implicit exception specifications are generated for destructors and deallocation functions declared without an explicit exception specification. This can also be enabled in nonstrict modes using the command line option --implicit_;noexcept.

  • Range-based ‘for’ loops are supported. For example:
    int f()  {
        auto x = {1, 2, 3};
        int sum = 0;
        for (auto i | x) sum += i;
        return sum;
    };

6.6. C++14 Language Features Accepted

The following features added in the C++14 standard are enabled in C++14 mode. This mode can be combined with the option for strict standard conformance. Several of these features are also enabled in default (nonstrict) C++ mode.

  • The implicit conversion rules are modified to allow multiple conversion functions in a class type such as a smart pointer, with the best match for the context chosen by overload resolution. Previous versions of the standard required a single conversion function in such classes.
  • Binary literals such as 0b0110 are accepted.
  • Function return types can be deduced from the return statements of the function definition, and the decl-type(auto) specifier is supported. For example:
    auto f() { return 5; }    // return type is int
  • Lambdas can specify expressions, not just local variables, to be captured. For example:
    auto l = [x = 42]{ return x + 1; };
  • Class aggregates can have member initializers. For example:
    struct S { int i = 3; } s{};    // s.i has value 3
  • Generic lambdas are accepted, allowing auto parameters to define a call operator template. For example:
    auto l = [](auto p) {return p*2; };
  • The deprecated standard attribute is accepted.
  • The apostrophe is accepted in numeric literals as a digit separator. For example:
    long l = 123'456'789;    // Equivalent to 123456789

7. Messages

This section describes the various messages that the compiler produces. These messages include the sign-on message and diagnostic messages for remarks, warnings, and errors. The compiler always displays any error messages, along with the erroneous source line, on the screen. If you specify the -⁠Mlist option, the compiler places any error messages in the listing file. You can also use the -⁠v option to display more information about the compiler, assembler, and linker invocations and about the host system. For more information on the -⁠Mlist and -⁠v options, refer to ‘Using Command-line Options’ in the PGI Compiler User’s Guide.

7.1. Diagnostic Messages

Diagnostic messages provide syntactic and semantic information about your source text. Syntactic information includes information such as syntax errors. Semantic information includes information such as unreachable code, incorrect number of arguments specified for a call to a routine, illegal data type usage, etc.

You can specify that the compiler displays error messages at a certain level with the -Minform option.

The compiler messages refer to a severity level, a message number, and the line number where the error occurs.

The compiler can also display internal error messages on standard error. If your compilation produces any internal errors, please contact the PGI technical reporting service.

If you use the listing file option -⁠Mlist, the compiler places diagnostic messages after the source lines in the listing file, in the following format:

   PGFTN-etype-enum-message (filename: line)

Where:

etype
is a character signifying the severity level
enum
is the error number
message
is the error message
filename
is the source filename
line
is the line number where the compiler detected an error.

7.2. Phase Invocation Messages

You can display compiler, assembler, and linker phase invocations by using the -⁠v command line option. For further information about this option, refer to the ‘Using Command-line Options’ section of the PGI Compiler User's Guide.

7.3. Fortran Compiler Error Messages

This section presents the error messages generated by the PGFORTRAN compiler. The compilers display error messages in the program listing and on standard output. They can also display internal error messages on standard error.

7.3.1. Message Format

Each message is numbered. Each message also lists the line and column number where the error occurs. A dollar sign ($) in a message represents information that is specific to each occurrence of the message.

7.3.2. Message List

Error message severities:

I
informative
W
warning
S
severe error
F
fatal error
V
variable
V000 Internal compiler error. $ $

This message indicates an error in the compiler, rather than a user error – although it may be possible for a user error to cause an internal error. The severity may vary; if it is informative or warning, correct object code was probably generated, but it is not safe to rely on this. Regardless of the severity or cause, internal errors should be reported to the PGI technical reporting service.

F001 Source input file name not specified

On the command line, source file name should be specified either before all the switches, or after them.

F002 Unable to open source input file: $

Source file name is misspelled, file is not in current working directory, or file is read protected.

F003 Unable to open listing file

This message typically occurs when the user does not have write permission for the current working directory.

F004 $ $

Generic message for file errors.

F005 Unable to open temporary file

Compiler uses directory "/usr/tmp" or "/tmp" in which to create temporary files. If neither of these directories is available on the node on which the compiler is being used, this error will occur.

S006 Input file empty

Source input file does not contain any Fortran statements other than comments or compiler directives.

F007 Subprogram too large to compile at this optimization level $

Internal compiler data structure overflow, working storage exhausted, or some other non-recoverable problem related to the size of the subprogram. If this error occurs at opt level 2, reducing the opt level to 1 may work around the problem. Moving the subprogram being compiled to its own source file may eliminate the problem. If this error occurs while compiling a subprogram of fewer than 2000, please report the problem to the PGI technical reporting service.

F008 Error limit exceeded

The compiler gives up because too many severe errors were issued; the error limit can be reset on the command line.

F009 Unable to open assembly file

This message typically occurs when the user does not have write permission for the current working directory.

F010 File write error occurred $

The file system may be full.

S011 Unrecognized command line switch: $

Refer to the PGI Compiler User’s Guide for a list of allowed compiler switches.

S012 Value required for command line switch: $

Certain switches require an immediately following value, such as "-opt 2".

S013 Unrecognized value specified for command line switch: $

S014 Ambiguous command line switch: $

Too short an abbreviation was used for one of the switches.

W015 Hexadecimal or octal constant truncated to fit data type

I016 Identifier, $, truncated to 63 chars

An identifier may be at most 63 characters in length; characters after the 63rd are ignored.

S017 Unable to open include file: $

File is missing, read protected, or maximum include depth (10) exceeded. Remember that the file name should be enclosed in quotes.

S018 Illegal label $ $

Used for label ‘field’ errors or illegal values. E.g., in fixed source form, the label field (first five characters) of the indicated line contains a non-numeric character.

S019 Illegally placed continuation line

A continuation line does not follow an initial line, or more than 99 continuation lines were specified.

S020 Unrecognized compiler directive

Refer to Directives and Pragmas Reference for list of allowed compiler directives.

S021 Label field of continuation line is not blank

The first five characters of a continuation line must be blank.

S022 Unexpected end of file - missing END statement

The source file is missing and END statement, or the file is truncated.

S023 Syntax error - unbalanced $

Unbalanced parentheses or brackets.

W024 CHARACTER or Hollerith constant truncated to fit data type

A character or hollerith constant was converted to a data type that was not large enough to contain all of the characters in the constant. This type conversion occurs when the constant is used in an arithmetic expression or is assigned to a non-character variable. The character or hollerith constant is truncated on the right, that is, if 4 characters are needed then the first 4 are used and the remaining characters are discarded.

W025 Illegal character ($) - ignored

The current line contains a character, possibly non-printing, which is not a legal Fortran character (characters inside of character or Hollerith constants cannot cause this error). As a general rule, all non-printing characters are treated as white space characters (blanks and tabs); no error message is generated when this occurs. If for some reason, a non-printing character is not treated as a white space character, its hex representation is printed in the form dd where each d is a hex digit.

S026 Unmatched quote

A character constant is missing a closing quote or the source file is truncated.

S027 Illegal integer constant: $

Integer constant is too large for 32 bit word.

S028 Illegal real or double precision constant: $

S029 Illegal $ constant: $

Illegal hexadecimal, octal, or binary constant. A hexadecimal constant consists of digits 0..9 and letters A..F or a..f; any other character in a hexadecimal constant is illegal. An octal constant consists of digits 0..7; any other digit or character in an octal constant is illegal. A binary constant consists of digits 0 or 1; any other digit or character in a binary constant is illegal.

S030 Explicit shape must be specified for $

A shape for an array expression is effected in this context.

S031 Illegal data type length specifier for $

The data type length specifier (e.g. 4 in INTEGER*4) is not a constant expression that is a member of the set of allowed values for this particular data type.

W032 Data type length specifier not allowed for $

The data type length specifier (e.g. 4 in INTEGER*4) is not allowed in the given syntax (e.g. DIMENSION A(10)*4).

S033 Illegal use of constant $

A constant was used in an illegal context, such as on the left side of an assignment statement or as the target of a data initialization statement.

S034 Syntax error at or near $

Illegal command specified.

I035 Predefined intrinsic $ loses intrinsic property

An intrinsic name was used in a manner inconsistent with the language definition for that intrinsic. The compiler, based on the context, will treat the name as a variable or an external function.

S036 Illegal implicit character range

First character must alphabetically precede second.

S037 Contradictory data type specified for $

The indicated identifier appears in more than one type specification statement and different data types are specified for it.

S038 Symbol, $, has not been explicitly declared

The indicated identifier must be declared in a type statement; this is required when the IMPLICIT NONE statement occurs in the subprogram.

W039 Symbol, $, appears illegally in a SAVE statement $

An identifier appearing in a SAVE statement must be a local variable or array.

S040 Illegal common variable $

Indicated identifier is a dummy variable, is already in a common block, or has previously been defined to be something other than a variable or array.

W041 Illegal use of dummy argument $

This error can occur in several situations. It can occur if dummy arguments were specified on a PROGRAM statement. It can also occur if a dummy argument name occurs in a DATA, COMMON, SAVE, or EQUIVALENCE statement. A program statement must have an empty argument list.

S042 $ is a duplicate dummy argument

Each dummy argument must have a unique name.

S043 Illegal attempt to redefine $ $

An attempt was made to define a symbol in a manner inconsistent with an earlier definition of the same symbol. This can happen for a number of reasons. The message attempts to indicate the situation that occurred.

intrinsic – An attempt was made to redefine an intrinsic function. A symbol that represents an intrinsic function may be redefined if that symbol has not been previously verified to be an intrinsic function. For example, the intrinsic sin can be defined to be an integer array. If a symbol is verified to be an intrinsic function via the INTRINSIC statement or via an intrinsic function reference then it must be referred to as an intrinsic function for the remainder of the program unit.

symbol – An attempt was made to redefine a symbol that was previously defined. An example of this is to declare a symbol to be a PARAMETER which was previously declared to be a subprogram argument.

S044 Multiple declaration for symbol $

A redundant declaration of a symbol has occurred. For example, an attempt was made to declare a symbol as an ENTRY when that symbol was previously declared as an ENTRY.

S045 Data type of entry point $ disagrees with function $

The current function has entry points with data types inconsistent with the data type of the current function. For example, the function returns type character and an entry point returns type complex.

S046 Data type length specifier in wrong position

The CHARACTER data type specifier has a different position for the length specifier from the other data types. Suppose, we want to declare arrays ARRAYA and ARRAYB to have 8 elements each having an element length of 4 bytes. The difference is that ARRAYA is character and ARRAYB is integer. The declarations would be CHARACTER ARRAYA(8)*4 and INTEGER ARRAYB*4(8).

S047 More than seven dimensions specified for array

The compiler currently supports up to seven dimensions for arrays.

S048 Illegal use of '*' in declaration of array $

An asterisk may be used only as the upper bound of the last dimension.

S049 Illegal use of '*' in non-subroutine subprogram

The alternate return specifier ‘*’ is legal only in the subroutine statement. Programs, functions, and block data are not allowed to have alternate return specifiers.

S050 Assumed size array, $, is not a dummy argument

Arrays with ‘*’ in their dimension(s) may only be declared as dummy arguments.

S051 Unrecognized built-in % function

The allowable built-in functions are %VAL, %REF, %LOC, and %FILL. One was encountered that did not match one of these allowed forms.

S052 Illegal argument to %VAL or %LOC

S053 %REF or %VAL not legal in this context

The built-in functions %REF and %VAL can only be used as actual parameters in procedure calls.

W054 Implicit character $ used in a previous implicit statement

An implicit character has been given an implied data type more than once. The implied data type for the implicit character is changed anyway.

W055 Multiple implicit none statements

The IMPLICIT NONE statement can occur only once in a subprogram.

W056 Implicit type declaration

The -Mdclchk switch and an implicit declaration following an IMPLICIT NONE statement will produce a warning message for IMPLICIT statements.

S057 Illegal equivalence of dummy variable, $

Dummy arguments may not appear in EQUIVALENCE statements.

S058 Equivalenced variables $ and $ not in same common block

A common block variable must not be equivalenced with a variable in another common block.

S059 Conflicting equivalence between $ and $

The indicated equivalence implies a storage layout inconsistent with other equivalences.

S060 Illegal equivalence of structure variable, $

STRUCTURE and UNION variables may not appear in EQUIVALENCE statements.

S061 Equivalence of $ and $ extends common block backwards

W062 Equivalence forces $ to be unaligned

EQUIVALENCE statements have defined an address for the variable which has an alignment not optimal for variables of its data type. This can occur when INTEGER and CHARACTER data are equivalenced, for instance.

I063 Gap in common block $ before $

S064 Illegal use of $ in DATA statement implied DO loop

The indicated variable is referenced where it is not an active implied DO index variable.

S065 Repeat factor less than zero

S066 Too few data constants in initialization statement

S067 Too many data constants in initialization statement

S068 Numeric initializer for CHARACTER $ out of range 0 through 255

A CHARACTER*1 variable or character array element can be initialized to an integer, octal, or hexadecimal constant if that constant is in the range 0 through 255.

S069 Illegal implied DO expression

The only operations allowed within an implied DO expression are integer +, -, *, and /.

S070 Incorrect sequence of statements $

The statement order is incorrect. For instance, an IMPLICIT NONE statement must precede a specification statement which in turn must precede an executable statement.

S071 Executable statements not allowed in block data

S072 Assignment operation illegal to $ $

The destination of an assignment operation must be a variable, array reference, or vector reference. The assignment operation may be by way of an assignment statement, a data statement, or the index variable of an implied DO-loop. The compiler has determined that the identifier used as the destination is not a storage location. The error message attempts to indicate the type of entity used.

entry point – An assignment to an entry point that was not a function procedure was attempted.

external procedure – An assignment to an external procedure or a Fortran intrinsic name was attempted. If the identifier is the name of an entry point that is not a function, an external procedure.

S073 Intrinsic or predeclared, $, cannot be passed as an argument

S074 Illegal number or type of arguments to $ $

The indicated symbol is an intrinsic or generic function, or a predeclared subroutine or function, requiring a certain number of arguments of a fixed data type.

S075 Subscript, substring, or argument illegal in this context for $

This can happen if you try to doubly index an array such as ra(2)(3). This also applies to substring and function references.

S076 Subscripts specified for non-array variable $

S077 Subscripts omitted from array $

S078 Wrong number of subscripts specified for $

S079 Keyword form of argument illegal in this context for $$

S080 Subscript for array $ is out of bounds

S081 Illegal selector $ $

S082 Illegal substring expression for variable $

Substring expressions must be of type integer and if constant must be greater than zero.

S083 Vector expression used where scalar expression required

A vector expression was used in an illegal context. For example, iscalar = iarray, where a scalar is assigned the value of an array. Also, character and record references are not vectorizable.

S084 Illegal use of symbol $ $

This message is used for many different errors.

S085 Incorrect number of arguments to statement function $

S086 Dummy argument to statement function must be a variable

S087 Non-constant expression where constant expression required

S088 Recursive subroutine or function call of $

A function may not call itself.

<