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 PGF77,PGF95, PGFORTRAN, PGC++, PGCC ANSI C compilers, the PGI profiler, and the PGI debugger. They work in conjunction with an x64 assembler and linker. You can use the PGI compilers and tools to compile, debug, optimize, and profile serial and parallel applications for x64 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. The PGI compilers are available on a variety of x86-64/x64 hardware platforms and operating systems. You 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 x64 processor-based systems.

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

Fortran Module/Library Interfaces for Windows provides a description of the Fortran module library interfaces that PVF supports.

C/C++ MMX/SSE Intrinsics provides tables that list the MMX Inline Intrinsics (mmintrin.h), the SSE1 inline intrinsics (xmmintrin.h), and SSE2 inline intrinsics (emmintrin.h).

Messages provides a list of compiler error messages.

Hardware and Software Constraints

This guide describes versions of the PGI compilers that produce assembly code forx64 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=medium shared library
AVX host -mcmodel=small SIMD
CUDA hyperthreading (HT) MPI SSE
device large arrays MPICH static linking
DLL license keys multicore Win64
driver linux86-64 NUMA x64
DWARF LLVM OpenPOWER s86
dynamic library manycore osx86-64 x87

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
PGF77 ANSI FORTRAN 77 pgf77
PGFORTRAN ISO/ANSI Fortran 2003 pgfortran
PGCC ISO/ANSI C11 and K&R C pgcc
PGC++ ISO/ANSI C++14 with GNU compatibility pgc++ on Linux and macOS
PGI Debugger Source code debugger pgdbg
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 the PGF77 compiler, whose features are a subset of PGFORTRAN, is similar.Usage of PGC⁠+⁠+ and PGCC is consistent with PGFORTRAN and PGF77, though there are command-line options and features of these compilers that do not apply to PGFORTRAN and PGF77, and vice versa.

There are a wide variety of 64-bit x86-compatible processors in use. All are supported by the PGI compilers and tools. Most of these processors are forward-compatible, but not backward-compatible, meaning that code compiled to target a given processor will not necessarily execute correctly on a previous-generation processor.

A table listing the processor options that PGI supports is available in the Release Notes. The table also includes the features utilized by the PGI compilers that distinguish them from a compatibility standpoint.

In this manual, the convention is to use "x86" to specify the group of processors that are "32-bit" but not "64-bit". The convention is to use "x64" to specify the group of processors that are both "32-bit" and "64-bit". x86 processor-based systems can run only 32-bit operating systems. x64 processor-based systems can run either 32-bit or 64-bit operating systems, and can execute all 32-bit x86 binaries in either case. x64 processors have additional registers and 64-bit addressing capabilities that are utilized by the PGI compilers and tools when running on a 64-bit operating system. The prefetch, SSE1, SSE2, SSE3, and AVX processor features further distinguish the various processors. Where such distinctions are important with respect to a given compiler option or feature, it is explicitly noted in this manual.

Note: The default for performing scalar floating-point arithmetic is to use SSE instructions on targets that support SSE1 and SSE2.
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 on 64-bit operating systems.

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 77 Aggregate Data Type Extensions

The PGFORTRAN compiler supports de facto standard extensions to FORTRAN 77 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 2's complement integer -128 to 127
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] (win64) 4 2's complement integer -231 to 231-1
[signed] long [int] (linux86-64) 8 2's complement integer -263 to 263-1
unsigned long [int] (win64) 4 ordinal 0 to 232-1
unsigned long [int] (linux86-64) 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 IEEE extended-precision floating-point 10-4931 to 104932(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 (32-bit operating system) 4 address 0 to 232-1
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 8-byte boundary.
long double (64-bit operating system) 16-byte boundary.
long [int] 32-bit on Win64 4-byte boundary, signed or unsigned.
long [int] linux86-64 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

On Windows, you can create the DLL obj1.dll and its import library obj1.lib using the following series of commands:

% pgfortran -Bdynamic -c object1.f
% pgfortran -Mmakedll object1.obj -o obj1.dll

Then compile the main program using this command:

$ pgfortran -# prog.f

For a complete example in Windows, refer to the example: ‘Build a DLL: Fortran’ in the ‘Creating and Using Libraries’ section of the PGI Compiler User’s Guide.

Description

Use this option to compile for and link to the shared object version of the PGI runtime libraries. This flag is required when linking with any DLL built by the PGI compilers. For Windows, this flag corresponds to the /MD flag used by Microsoft’s cl compilers.

Note:

On Windows, -⁠Bdynamic must be used for both compiling and linking.

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.

Note:

On Windows, -⁠Bstatic must be used for both compiling and linking.

For more information on using static libraries on Windows, refer to ‘Creating and Using Static Libraries on Windows’ in the ‘Creating and Using Libraries’ section of the PGI Compiler User’s Guide.

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.

For more information on using static libraries on Windows, refer to ‘Creating and Using Static Libraries on Windows’ in the ‘Creating and Using Libraries’ section of the PGI Compiler User's Guide.

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: Auto-selection of the appropriate -⁠tp option means that programs built using the -⁠fastsse option on a given system are not necessarily backward-compatible with older systems.
Note: C/C++ compilers enable -⁠Mautoinline with -⁠fast.

2.3.17. -fastsse

Synonymous with -⁠fast.

2.3.18. --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.

2.3.19. -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.

2.3.20. -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.

2.3.21. -fPIC

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

2.3.22. -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.

2.3.23. -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.

2.3.24. -g77libs

(Linux only) Used on the link line, this option instructs the pgfortran driver to search the necessary g77 support libraries to resolve references specific to g77 compiled program units.

Note: The g77 compiler must be installed on the system on which linking occurs in order for this option to function correctly.

Default

The compiler does not search g77 support libraries to resolve references at link time.

Usage

The following command-line requests that g77 support libraries be searched at link time:

$ pgfortran -g77libs myprog.f g77_object.o

Description

(Linux only) Use the -⁠g77libs option on the link line if you are linking g77-compiled program units into a pgfortran-compiled main program using the pgfortran driver. When this option is present, the pgfortran driver searches the necessary g77 support libraries to resolve references specific to g77 compiled program units.

2.3.25. -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.'

2.3.26. -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'

2.3.27. -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.

2.3.28. -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.

2.3.29. --keeplnk

(Windows only.) Preserves the temporary file when the compiler generates a temporary indirect file for a long linker command.

Usage

In the following example the compiler preserves each temporary file rather than deleting it.

$ pgfortran --keeplnk myprog.f

Description

If the compiler generates a temporary indirect file for a long linker command, use this option to instruct the compiler to preserve the temporary file instead of deleting it.

2.3.30. -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.

2.3.31. -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.

2.3.32. -M

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

2.3.33. -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

When the following example is executed on Windows, pgfortran creates a link map in the file myprog.map.

$ pgfortran -m myprog.f

Description

Use this option to display a link map.

  • On Linux, the map is written to stdout.
  • On Windows, the map is written to a .map file whose name depends on the executable. If the executable is myprog.f, the map file is in myprog.map.

2.3.34. -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.

2.3.35. -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
chkfpstk Check for internal consistency of the x87 FP stack in the prologue of a function and after returning from a function or subroutine call (-⁠tp px/p5/p6/piii targets only). Miscellaneous
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
dll Link with the DLL version of the runtime libraries (Windows only). Miscellaneous
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 F77-style fixed format source code (pgf95, pgfortran only). Fortran Language
[no]flushz Do/don't set SSE 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
largeaddressaware [Win64 only] Generates code that allows for addresses greater than 2GB, using RIP-relative addressing. Code Generation
[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]loop32 Aligns [does not align] innermost loops on 32 byte boundaries with -⁠tp barcelona Code Generation
[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
makedll Generate a dynamic link library (DLL).(Windows only). Miscellaneous
makeimplib Passes the -def switch to the librarian without a deffile, when used without -⁠def:deffile.(Windows only) Miscellaneous
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
nopgdllmain Do not link the module containing the default DllMain() into the DLL(Windows only). 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
[no]scalarsse Do [do not] use SSE/SSE2 instructions to perform scalar floating-point arithmetic. Optimization
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]smart Do [do not] enable optional post-pass assembly optimizer. Optimization
[no]smartalloc[=huge| huge:<n>|hugebss] Add a call to the routine mallopt in the main routine. Supports large TLBs on Linux and Windows.
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 (pgf77, pgf95, and pgfortran only). Code Generation
[no]vect Do [do not] invoke the code vectorizer. Optimization

2.3.36. -mcmodel=medium

(For use only on 64-bit Linux targets) Generates code for the medium memory model in the linux86-64 execution environment. Implies -⁠Mlarge_arrays.

Default: The compiler generates code for the small memory model.

Usage

The following command line requests position independent code be generated, and the option -⁠mcmodel=medium be passed to the assembler and linker:

$ pgfortran -mcmodel=medium myprog.f

Description

The default small memory model of the linux86-64 environment limits the combined area for a user’s object or executable to 1GB, with the Linux kernel managing usage of the second 1GB of address for system routines, shared libraries, stacks, and so on. Programs are started at a fixed address, and the program can use a single instruction to make most memory references.

The medium memory model allows for larger than 2GB data areas, or .bss sections. Program units compiled using either -⁠mcmodel=medium or -⁠fpic require additional instructions to reference memory. The effect on performance is a function of the data-use of the application. The -⁠mcmodel=medium switch must be used at both compile time and link time to create 64-bit executables. Program units compiled for the default small memory model can be linked into medium memory model executables as long as they are compiled with the option -⁠fpic, or position-independent.

The linux86-64 environment provides static libxxx.a archive libraries, that are built both with and without -⁠fpic, and dynamic libxxx.so shared object libraries that are compiled with -⁠fpic. Using the link switch -⁠mcmodel=medium implies the -⁠fpic switch and utilizes the shared libraries by default. The directory $PGI/linux86-64/<rel>/lib contains the libraries for building small memory model codes; and the directory $PGI/linux86-64/<rel>/libso contains shared libraries for building both -⁠fpic and -⁠mcmodel=medium executables.

Note:

-⁠mcmodel=medium -fpic is not allowed to create shared libraries. However, you can create static archive libraries (.a) that are -⁠fpic.

2.3.37. -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.

2.3.38. -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.

The suboptions are one or more of the following:

align
Forces loop iterations to be allocated to OpenMP processes using an algorithm that maximizes alignment of vector sub-sections in loops that are both parallelized and vectorized for SSE. This allocation can improve performance in program units that include many such loops. It can also result in load-balancing problems that significantly decrease performance in program units with relatively short loops that contain a large amount of work in each iteration. The numa suboption uses libnuma on systems where it is available.
allcores
Instructs the compiler to target all available cores. You specify this suboption at link time.
bind
Instructs the compiler to bind threads to cores. You specify this suboption at link time.
[no]numa
Uses [does not use] libnuma on systems where it is available.

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.

2.3.39. -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.

2.3.40. -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.

2.3.41. -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

2.3.42. -pc

Note: This option is available only for -⁠tp px/p5/p6/piii targets.

Allows you to control the precision of operations performed using the x87 floating point unit, and their representation on the x87 floating point stack.

Syntax

-pc { 32 | 64 | 80 }

Usage

$ pgfortran -pc 64 myprog.f

Description

The x87 architecture implements a floating-point stack using eight 80-bit registers. Each register uses bits 0–63 as the significant, bits 64–78 for the exponent, and bit 79 is the sign bit. This 80-bit real format is the default format, called the extended format. When values are loaded into the floating point stack they are automatically converted into extended real format. The precision of the floating point stack can be controlled, however, by setting the precision control bits (bits 8 and 9) of the floating control word appropriately. In this way, you can explicitly set the precision to standard IEEE double-precision using 64 bits, or to single precision using 32 bits.

According to Intel documentation, this only affects the x87 operations of add, subtract, multiply, divide, and square root. In particular, it does not appear to affect the x87 transcendental instructions.

The default precision is system dependent. To alter the precision in a given program unit, the main program must be compiled with the same -pc option. The command line option -⁠pc val lets the programmer set the compiler’s precision preference.

Valid values for val are:

32 single precision 64 double precision 80 extended precision

Extended Precision Option – Operations performed exclusively on the floating-point stack using extended precision, without storing into or loading from memory, can cause problems with accumulated values within the extra 16 bits of extended precision values. This can lead to answers, when rounded, that do not match expected results.

For example, if the argument to sin is the result of previous calculations performed on the floating-point stack, then an 80-bit value used instead of a 64-bit value can result in slight discrepancies. Results can even change sign due to the sin curve being too close to an x-intercept value when evaluated. To maintain consistency in this case, you can assure that the compiler generates code that calls a function. According to the x86 ABI, a function call must push its arguments on the stack (in this way memory is guaranteed to be accessed, even if the argument is an actual constant). Thus, even if the called function simply performs the inline expansion, using the function call as a wrapper to sin has the effect of trimming the argument precision down to the expected size. Using the -⁠Mnobuiltin option on the command line for C accomplishes this task by resolving all math routines in the library libm, performing a function call of necessity. The other method of generating a function call for math routines, but one that may still produce the inline instructions, is by using the -⁠Kieee switch.

A second example illustrates the precision control problem using a section of code to determine machine precision:

program find_precision 
			 
	 w = 1.0
	100 w=w+w
	 y=w+1
	 z=y-w
	 if (z .gt. 0) goto 100
	C now w is just big enough that |((w+1)-w)-1| >= 1
	...
	 print*,w
	 end

In this case, where the variables are implicitly real*4, operations are performed on the floating-point stack where optimization removes unnecessary loads and stores from memory. The general case of copy propagation being performed follows this pattern:

a = x
  y = 2.0 + a

Instead of storing x into a, then loading a to perform the addition, the value of x can be left on the floating-point stack and added to 2.0. Thus, memory accesses in some cases can be avoided, leaving answers in the extended real format. If copy propagation is disabled, stores of all left-hand sides will be performed automatically and reloaded when needed. This will have the effect of rounding any results to their declared sizes.

The find_precision program has a value of 1.8446744E+19 when executed using default (extended) precision. If, however, -⁠Kieee is set, the value becomes 1.6777216E+07 (single precision.) This difference is due to the fact that -⁠Kieee disables copy propagation, so all intermediate results are stored into memory, then reloaded when needed. Copy propagation is only disabled for floating-point operations, not integer. With this particular example, setting the -⁠pc switch will also adjust the result.

The -⁠Kieee switch also has the effect of making function calls to perform all transcendental operations. Except when the -⁠Mnobuiltin switch is set in C, the function still produces the x86 machine instruction for computation, and arguments are passed on the stack, which results in a memory store and load.

Finally, -⁠Kieee also disables reciprocal division for constant divisors. That is, for a/b with unknown a and constant b, the expression is usually converted at compile time to a*(1/b), thus turning an expensive divide into a relatively fast scalar multiplication. However, numerical discrepancies can occur when this optimization is used.

Understanding and correctly using the -⁠pc, -⁠Mnobuiltin, and -⁠Kieee switches should enable you to produce the desired and expected precision for calculations which utilize floating-point operations.

2.3.43. --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

2.3.44. -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.

2.3.45. -pgc++libs

Instructs the compiler to append C⁠+⁠+ runtime libraries to the link line for programs built using either PGF77 or PGF90 .

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 pgf77 .

$ pgf90 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 either PGF77 or PGF90 .

2.3.46. -pgf77libs

Instructs the compiler to append PGF77 runtime libraries to the link line.

Default

The C/C++ compilers do not append the PGF77 runtime libraries to the link line.

Usage

In the following example a .c main program is linked with an object file compiled with pgf77.

$ pgcc main.c myf77.o -pgf77libs

Description

Use this option to instruct the compiler to append PGF77 runtime libraries to the link line.

2.3.47. -pgf90libs

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

Default

The C/C++ compilers do not append the PGF90/PGF95/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 PGF90/PGF95/PGFORTRAN runtime libraries to the link line.

2.3.48. -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.

2.3.49. -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.

2.3.50. -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).

2.3.51. -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/linux86-64/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.

2.3.52. -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.

2.3.53. -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.

2.3.54. -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.

2.3.55. -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.

2.3.56. -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.

2.3.57. -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.

2.3.58. -stack

(Windows only) Allows you to explicitly set stack properties for your program.

Default

If -⁠stack is not specified, then the defaults are as followed:

Win64
No default setting

Syntax

-stack={ (reserved bytes)[,(committed bytes)] }{, [no]check }

Usage

The following example demonstrates how to reserve 524,288 stack bytes (512KB), commit 262,144 stack bytes for each routine (256KB), and disable the stack initialization code with the nocheck argument.

$ pgfortran -stack=524288,262144,nocheck myprog.f

Description

Use this option to explicitly set stack properties for your program. The -⁠stack option takes one or more arguments: (reserved bytes), (committed bytes), [no]check.

reserved bytes
Specifies the total stack bytes required in your program.
committed bytes
Specifies the number of stack bytes that the Operating System will allocate for each routine in your program. This value must be less than or equal to the stack reserved bytes value.

Default for this argument is 4096 bytes.

[no]check
Instructs the compiler to generate or not to generate stack initialization code upon entry of each routine. Check is the default, so stack initialization code is generated.

Stack initialization code is required when a routine's stack exceeds the committed bytes size. When your committed bytes is equal to the reserved bytes or equal to the stack bytes required for each routine, then you can turn off the stack initialization code using the -stack=nocheck compiler option. If you do this, the compiler assumes that you are specifying enough committed stack space; and therefore, your program does not have to manage its own stack size.

For more information on determining the amount of stack required by your program, refer to -⁠Mchkstk compiler option, described in ‘Miscellaneous Controls’.

Note:-stack=(reserved bytes),(committed bytes) are linker options.

-stack=[no]check is a compiler option.

If you specify -stack=(reserved bytes),(committed bytes) on your compile line, it is only used during the link step of your build. Similarly, -stack=[no]check can be specified on your link line, but it's only used during the compile step of your build.

2.3.59. -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.
cc50
Generate code for compute capability 5.0.
cc60
Generate code for compute capability 6.0.
cc70
Generate code for compute capability 7.0.
[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.

2.3.60. -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.

2.3.61. -tp <target>[,target...]

Sets the target processor.

Default

The PGI compilers produce code specifically targeted to the type of processor on which the compilation is performed. In particular, the default is to use all supported instructions wherever possible when compiling on a given system.

The default target processor is auto-selected depending on the processor on which the compilation is performed. You can specify a target processor to compile for a different processor type, such as to select a more generic processor, allowing the code to run on more system types. Specifying two or more target processors enables unified binary code generation, where two or more versions of each function may be generated, each version optimized for the specific instruction set available in each target processor.

Executables created on a given system without the -tp flag may not be usable on previous generation systems. For example, executables created on an Intel Sandybridge processor may use instructions that are not available on earlier Intel Nehalem or Intel P7 systems.

Syntax

Syntax for 64-bit targets:

-tp {k8-64 | k8-64e | p7-64 | core2-64 | x64}

Usage

In the following example, pgfortran sets the target processor to a 64-bit Intel Nehalem processor:

$ pgfortran -tp=nehalem-64 myprog.f

Description

Use this option to set the target architecture. By default, the PGI compiler uses all supported instructions wherever possible when compiling on a given system.

Processor-specific optimizations can be specified or limited explicitly by using the -⁠tp option. Thus, it is possible to create executables that are usable on previous generation systems.

The following list contains the possible suboptions for -⁠tp and the processors that each suboption is intended to target. Options without a bit-length suffix use the current width associated with the driver on your path.

barcelona
generate code for AMD Opteron/Quadcore and compatible processors.
bulldozer
generate code for AMD Bulldozer and compatible processors.
core2
generate code for Intel Core 2 Duo and compatible processors.
haswell
generate code that is usable on any Haswell processor-based system.
istanbul
generate code that is usable on any Istanbul processor-based system.
k8
generate code hat is usable on any AMD64 and compatible processor.
k8-64e
generate 64-bit code for AMD Opteron Revision E, AMD Turion, and compatible processors.
nehalem
generate code that is usable on any Nehalem processor-based system.
p7
generate code for Pentium 4 and compatible processors.
penryn
generate code for Intel Penryn Architecture and compatible processors.
piledriver
generate code that is usable on any Piledriver processor-based system.
px
generate code that is usable on any x86-64 processor-based system.
sandybridge
generate code for Intel Sandy Bridge and compatible processors.
shanghai
generate code that is usable on any AMD Shanghai processor-based system.
x64
generate 64-bit unified binary code including full optimizations and support for both AMD and Intel x86-64 processors.

Refer to the PGI Release Notes for a concise list of the features of these processors that distinguish them as separate targets when using the PGI compilers and tools.

Different processors have differences, some subtle, in hardware features such as instruction sets and cache size. The compilers make architecture-specific decisions about such things as instruction selection, instruction scheduling, and vectorization. Any of these decisions can have significant effects on performance and compatibility. PGI unified binaries provide a low-overhead means for a single program to run well on a number of hardware platforms.

You can use the -⁠tp option to produce PGI Unified Binary programs. The compilers generate, and combine into one executable, multiple binary code streams, each optimized for a specific platform. At runtime, this one executable senses the environment and dynamically selects the appropriate code stream.

The target processor switch, -⁠tp , accepts a comma-separated list of 64-bit targets and will generate code optimized for each listed target. For example, the following switch generates optimized code for three targets: k8-64, p7-64, and core2-64.

Syntax for optimizing for multiple targets:

-tp k8-64,p7-64,core2-64

The -⁠tp k8-64 and -⁠tp k8-64e options result in generation of code supported on and optimized for AMD x64 processors, while the -⁠tp p7-64 option results in generation of code that is supported on and optimized for Intel x86-64 processors. Performance of k8-64 or k8-64e code executed on Intel x86-64 processors, or of p7-64 code executed on AMD x86-64 processors, can often be significantly less than that obtained with a native binary.

The special -⁠tp x64 option is equivalent to -⁠tp k8-64,p7-64 . This switch produces PGI Unified Binary programs containing code streams fully optimized and supported for bothAMD64 and Intel 64 processors.

For more information on unified binaries, refer to the section ’Processor-Specific Optimization and the Unified Binary’ in the PGI Compiler User’s Guide.

2.3.62. -[no]traceback

Adds debug information for runtime traceback for use with the environment variable PGI_TERM.

Default

The compiler enables traceback for FORTRAN and disables traceback for C and C++.

Syntax

-traceback

Usage

In this example, pgfortran enables traceback for the program myprog.f.

$ pgfortran -traceback myprog.f

Description

Use this option to enable or disable runtime traceback information for use with the environment variable PGI_TERM.

Setting setTRACEBACK=OFF; in siterc or .mypg*rc also disables default traceback.

Using ON instead of OFF enables default traceback.

2.3.63. -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.

2.3.64. -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.

2.3.65. -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.

2.3.66. -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.

2.3.67. -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.

2.3.68. -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.

2.3.69. -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.

2.3.70. -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.

2.3.71. -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 SSE 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 SSE 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.
-Minstrument[=functions] (linux86-64 only)
Generate additional code to enable instrumentation of functions. The option -⁠Minstrument=functions is the same as -⁠Minstrument.
Implies -⁠Minfo=ccff and -⁠Mframe.
-Mlargeaddressaware=[no]
[Win64 only] Generates code that allows for addresses greater than 2 GB, using RIP-relative addressing.
Use-⁠Mlargeaddressaware=no for a direct addressing mechanism that restricts the total addressable memory.
Note: Do not use -⁠Mlargeaddressaware=no if the object file will be placed in a DLL.

If -⁠Mlargeaddressaware=no is used to compile any object file, it must also be used when linking.
-Mlarge_arrays
Enable support for 64-bit indexing and single static data objects larger than 2 GB in size. This option is the default in the presence of -⁠mcmodel=medium. It can be used separately together with the default small memory model for certain 64-bit applications that manage their own memory space.
For more information, refer to the ‘Programming Considerations for 64-Bit Environments’ section of the PGI Compiler User's Guide .
-Mnolarge_arrays
Disable support for 64-bit indexing and single static data objects larger than 2 GB in size. When this option is placed after -⁠mcmodel=medium on the command line, it disables use of 64-bit indexing for applications that have no single data object larger than 2 GB.
For more information, refer to the ‘Programming Considerations for 64-Bit Environments’ section of the PGI Compiler User's Guide .
-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).
-Mmpi=option
-⁠Mmpi adds the include and library options to the compile and link commands necessary to build an MPI application using MPI header files and libraries.
To use -⁠Mmpi, you must have a version of MPI installed on your system.
This option tells the compiler to use the headers and libraries for the specified version of MPI.
The -Mmpi options are as specified:
  • -Mmpi=mpich – Selects the default MPICH v3 libraries on Linux and macOS.
  • -Mmpi=mpich1 – This option has been deprecated. It continues to direct the compiler to include the appropriate MPICH1 header files and to link against the correct MPICH1 libraries but only if you set the environment variable MPIDIR to the root of an MPICH1 installation.
  • -Mmpi=mpich2 – This option has been deprecated. It continues to direct the compiler to include the appropriate MPICH2 header files and to link against the correct MPICH2 libraries but only if you set the environment variable MPIDIR to the root of an MPICH2 installation.
  • -Mmpi=mvapich1 – This option has been deprecated. It continues to direct the compiler to include the appropriate MVAPICH1 header files and to link against the correct MVAPICH1 libraries but only if you set the environment variable MPIDIR to the root of an MVAPICH1 installation.

For more information, refer to the ‘Programming Considerations for 64-Bit Environments’ section of the PGI Compiler User's Guide .
Note: On Linux and macOS, you can set the environment variable MPIDIR to override the default locations that the compiler looks to find the MPI directory.
-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 g77, 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.
-Mstack_arrays
places automatic arrays on the stack.
-Mnostack_arrays
allocates automatic arrays on the heap. -Mnostack_arrays is the default and what traditionally has been the approach used.
-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 (pgf77, pgf95, andpgfortran 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.
Note: The current default is to support gcc's extended asm, where the syntax of extended asm includes asm strings. The -⁠M[no]asmkeyword switch is useful only if the target device is a Pentium 3 or older cpu type (-⁠tp piii|p6|k7|athlon|athlonxp|px).
-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 on Linux and Windows. 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.
huge:<n>
Link the huge page runtime library and allocate n huge pages. Use this suboption to limit the number of huge pages allocated to n.
You can also limit the pages allocated by using the environment variable PGI_HUGE_PAGES.
hugebss
(64-bit only) Puts the BSS section in huge pages; attempts to put a program's uninitialized data section into huge pages.
Note: This flag dynamically links the library libhugetlbfs_pgi even if -⁠Bstatic is used.
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.
cc70
Generate code for compute capability 7.0.
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.
cuda9.0 or 9.0
Specify the NVIDIA CUDA 9.0 version of the toolkit.
Note: Compile with the CUDA 8.0 or CUDA 9.0 toolkit either by using the -Mcuda=8.0 or -Mcuda=9.0 option, or by adding set DEFCUDAVERSION=8.0 or set DEFCUDAVERSION=9.0 to the siterc file. This action generates binaries that may not work on machines with an earlier CUDA driver.
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 77-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 F77 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 SSE instructions enabled.

>$ pgfortran -Mvect=sse -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.
Note: As of the PGI 16.3 release, -⁠Mipa has been disabled on Windows.
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.
w
use the AMD-specific prefetchw 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
(pgf77, pgf95, andpgfortran only) The compiler treats the intrinsics CMPLX and REAL as DCMPLX and DBLE, respectively.
-Mnor8intrinsics
(pgf77, pgf95, andpgfortran 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.
-Mscalarsse
Use SSE/SSE2 instructions to perform scalar floating-point arithmetic. This option is valid only on option -⁠tp [p7 | k8-32 | k8-64] targets.
-Mnoscalarsse
Do not use SSE/SSE2 instructions to perform scalar floating-point arithmetic; use x87 instructions instead. This option is not valid in combination with the -⁠tp k8-64 option.
-Msmart
instructs the compiler driver to invoke a post-pass assembly optimization utility.
-Mnosmart
instructs the compiler not to invoke an AMD64-specific post-pass assembly optimization utility.
-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 SSE, SSE2, 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, such as using the -⁠stack option on Windows.
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.
-Mdll
This Windows-only flag has been deprecated. Refer to -⁠Bdynamic. This flag was used to link with the DLL versions of the runtime libraries, and it was required when linking with any DLL built by any PGI compilers. This option implied -⁠D_DLL, which defines the preprocessor symbol _DLL.
-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. (linux86-64 only).
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.
-Mmakedll
(Windows only) generate a dynamic link library (DLL).
-Mmakeimplib
(Windows only) generate an import library for a DLL without creating the DLL. When used without -def:deffile, passes the switch -def to the librarian without a deffile.
-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.
-Mnosgimp
when used in combination with the -⁠mp option, the compiler ignores SGI-style parallelization directives or pragmas, but still processes OpenMP parallelization directives or pragmas.
-Mnopgdllmain
(Windows only) do not link the module containing the default DllMain() into the DLL. This flag applies to building DLLs with the PGFORTRAN compilers. If you want to replace the default DllMain() routine with a custom DllMain(), use this flag and add the object containing the custom DllMain() to the link line. The latest version of the default DllMain() used by PGFORTRAN is included in the Release Notes for each release. The PGFORTRAN-specific code in this routine must be incorporated into the custom version of DllMain() to ensure the appropriate function of your DLL.
-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 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=sse 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.

Refer to -tp <target>[,target...] for a list of targets that can be used as parameters to the tp directive.

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, Win64, and macOS 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.

4.5. !DEC\$ Directives

PGI Fortran compilers for Microsoft Windows support directives that help with inter-language calling and importing and exporting routines to and from DLLs. These directives all take the form:

!DEC$ directive

For specific format requirements, refer to the section ‘!DEC$ Directives’ in the PGI Compiler User's Guide.

4.5.1. ALIAS Directive

This directive specifies an alternative name with which to resolve a routine.

The syntax for the ALIAS directive is either of the following:

!DEC$ ALIAS routine_name , external_name
!DEC$ ALIAS routine_name : external_name

In this syntax, external_name is used as the external name for the specified routine_name.

If external_name is an identifier name, the name (in uppercase) is used as the external name for the specified routine_name. If external_name is a character constant, it is used as-is; the string is not changed to uppercase, nor are blanks removed.

You can also supply an alias for a routine using the ATTRIBUTES directive, described in the next section:

!DEC$ ATTIRIBUTES ALIAS : 'alias_name' :: routine_name

This directive specifies an alternative name with which to resolve a routine, as illustrated in the following code fragment that provides external names for three routines. In this fragment, the external name for sub1 is name1, for sub2 is name2, and for sub3 is name3.

subroutine sub
!DEC$ alias sub1 , 'name1'
!DEC$ alias sub2 : 'name2'
!DEC$ attributes alias : 'name3' :: sub3 

4.5.2. ATTRIBUTES Directive

This directive lets you specify properties for data objects and procedures.

The syntax for the ATTRIBUTES directive is this:

!DEC$ ATTRIBUTES <list>

where <list> is one of the following:

ALIAS : 'alias_name' :: routine_name
Specifies an alternative name with which to resolve routine_name.
C :: routine_name
Specifies that the routine routine_name will have its arguments passed by value. When a routine marked C is called, arguments, except arrays, are sent by value. For characters, only the first character is passed. The standard Fortran calling convention is pass by reference.
DLLEXPORT :: name
Specifies that name is being exported from a DLL.
DLLIMPORT :: name
Specifies that name is being imported from a DLL.
NOMIXED_STR_LEN_ARG
Specifies that hidden lengths are placed in sequential order at the end of the list.
Note: This attribute only applies to routines that are compiled with -Miface=cref or that use the default Windows calling conventions.
REFERENCE :: name
Specifies that the argument name is being passed by reference. Often this attribute is used in conjunction with STDCALL, where STDCALL refers to an entire routine; then individual arguments are modified with REFERENCE.
STDCALL :: routine_name
Specifies that routine routine_name will have its arguments passed by value. When a routine marked STDCALL is called, arguments (except arrays and characters) will be sent by value. The standard Fortran calling convention is pass by reference.
VALUE :: name
Specifies that the argument 'name' is being passed by value.

4.5.3. DECORATE Directive

The DECORATE directive specifies that the name specified in the ALIAS directive should have the prefix and postfix decorations performed on it that are associated with the calling conventions that are in effect. These declarations are the same ones performed on the name when ALIAS is not specified.

The syntax for the DECORATE directive is this:

!DEC$ DECORATE
Note: When ALIAS is not specified, this directive has no effect.

4.5.4. DISTRIBUTE Directive

This directive is front-end based, and tells the compiler at what point within a loop to split into two loops.

The syntax for the DISTRIBUTE directive is either of the following:

!DEC$ DISTRIBUTE POINT
!DEC$ DISTRIBUTEPOINT

Example:

subroutine dist(a,b,n)
    integer i
    integer n
    integer a(*)
    integer b(*)
    do i = 1,n
        a(i) = a(i)+2
!DEC$ DISTRIBUTE POINT
        b(i) = b(i)*4
    enddo
end subroutine 

5. Runtime Environment

This section describes the programming model supported for compiler code generation, including register conventions and calling conventions for x64 processor-based systems. It addresses these conventions for processors running linux86-64 operating systems and for processors running Win64 operating 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. Linux86-64 Programming Model

This section defines compiler and assembly language conventions for the use of certain aspects of an x86-64 processor running a linux86-64 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 System V Application Binary Interface: AMD64 Architecture Processor Supplement and the System V Application Binary Interface, listed in the Related Publications section in the Preface.

Note: The programming model used for Win64 differs from the Linux86-64 model. For more information, refer to Win64 Programming Model.

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 x86-64 Architecture provides a variety of registers. All the general purpose registers, XMM registers, and x87 registers are visible to all procedures in a running program.

Table 16. Register Allocation
Type Name Purpose
General %rax 1st return register
  %rbx callee-saved; optional base pointer
  %rcx pass 4th argument to functions
  %rdx pass 3rd argument to functions; 2nd return register
  %rsp stack pointer
  %rbp callee-saved; optional stack frame pointer
  %rsi pass 2nd argument to functions
  %rdi pass 1st argument to functions
  %r8 pass 5th argument to functions
  %r9 pass 6th argument to functions
  %r10 temporary register; pass a function's static chain pointer
  %r11 temporary register
  %r12-r15 callee-saved registers
XMM %xmm0-%xmm1 pass and return floating point arguments
  %xmm2-%xmm7 pass floating point arguments
  %xmm8-%xmm15 temporary registers
x87 %st(0) temporary register; return long double arguments
  %st(1) temporary register; return long double arguments
  %st(2) - %st(7) temporary registers

In addition to the registers, each function has a frame on the run-time stack. This stack grows downward from high addresses. Table 17 shows the stack frame organization.

Table 17. Standard Stack Frame
Position Contents Frame
8n+16 (%rbp) argument eightbyte n previous
  . . .  
16 (%rbp) argument eightbyte 0  
8 (%rbp) return address current
0 (%rbp) caller's %rbp current
-8 (%rbp) unspecified  
  . . .  
0 (%rsp) variable size  
-128 (%rsp) red zone  

Key points concerning the stack frame:

  • The end of the input argument area is aligned on a 16-byte boundary.
  • The 128-byte area beyond the location of %rsp is called the red zone and can be used for temporary local data storage. This area is not modified by signal or interrupt handlers.
  • A call instruction pushes the address of the next instruction (the return address) onto the stack. The return instruction pops the address off the stack and effectively continues execution at the next instruction after the call instruction. A function must preserve non-volatile registers, a register whose contents must be preserved across subroutine calls. Additionally, the called function must remove the return address from the stack, leaving the stack pointer (%rsp) with the value it had before the call instruction was executed.

All registers on an x86-64 system are visible to both a calling and a called function. Registers %rbx, %rsp, %rbp, %r12, %r13, %r14, and %r15 are non-volatile across function calls. Therefore, a function must preserve these registers' values for its caller. Remaining registers are volatile (scratch) registers, that is a register whose contents need not be preserved across subroutine calls. If a calling function wants to preserve such a register value across a function call, it must save its value explicitly.

Registers are used extensively in the standard calling sequence. The first six integer and pointer arguments are passed in these registers (listed in order): %rdi, %rsi, %rdx, %rcx, %r8, %r9. The first eight floating point arguments are passed in the first eight XMM registers: %xmm0, %xmm1, ..., %xmm7. The registers %rax and %rdx are used to return integer and pointer values. The registers %xmm0 and %xmm1 are used to return floating point values.

Additional registers with assigned roles in the standard calling sequence:

%rsp
The stack pointer holds the limit of the current stack frame, which is the address of the stack's bottom-most, valid word. The stack must be 16-byte aligned.
%rbp
The frame pointer holds a base address for the current stack frame. Consequently, a function has registers pointing to both ends of its frame. Incoming arguments reside in the previous frame, referenced as positive offsets from %rbp, while local variables reside in the current frame, referenced as negative offsets from %rbp. A function must preserve this register value for its caller.
RFLAGS
The flags register contains the system flags, such as the direction flag and the carry flag. The direction flag must be set to the "forward" (i.e., zero) direction before entry and upon exit from a function. Other user flags have no specified role in the standard calling sequence and are not preserved.
Floating Point Control Word
The control word contains the floating-point flags, such as the rounding mode and exception masking. This register is initialized at process initialization time and its value must be preserved.

Signals can interrupt processes. Functions called during signal handling have no unusual restriction on their use of registers. Moreover, if a signal handling function returns, the process resumes its original execution path with registers restored to their original values. Thus, programs and compilers may freely use all registers without danger of signal handlers changing their values.

5.1.2. Function Return Values

Functions Returning Scalars or No Value

  • A function that returns an integral or pointer value places its result in the next available register of the sequence %rax, %rdx.
  • A function that returns a floating point value that fits in the XMM registers returns this value in the next available XMM register of the sequence %xmm0, %xmm1.
  • An X87 floating-point return value appears on the top of the floating point stack in %st(0) as an 80-bit X87 number. If this X87 return value is a complex number, the real part of the value is returned in %st(0) and the imaginary part in %st(1).
  • A function that returns a value in memory also returns the address of this memory in %rax.
  • Functions that return no value (also called procedures or void functions) put no particular value in any register.

Functions Returning Structures or Unions

A function can use either registers or memory to return a structure or union. The size and type of the structure or union determine how it is returned. If a structure or union is larger than 16 bytes, it is returned in memory allocated by the caller.

To determine whether a 16-byte or smaller structure or union can be returned in one or more return registers, examine the first eight bytes of the structure or union. The type or types of the structure or union’s fields making up these eight bytes determine how these eight bytes will be returned. If the eight bytes contain at least one integral type, the eight bytes will be returned in %rax even if non-integral types are also present in the eight bytes. If the eight bytes only contain floating point types, these eight bytes will be returned in %xmm0.

If the structure or union is larger than eight bytes but smaller than 17 bytes, examine the type or types of the fields making up the second eight bytes of the structure or union. If these eight bytes contain at least one integral type, these eight bytes will be returned in %rdx even if non-integral types are also present in the eight bytes. If the eight bytes only contain floating point types, these eight bytes will be returned in %xmm1.

If a structure or union is returned in memory, the caller provides the space for the return value and passes its address to the function as a "hidden" first argument in %rdi. This address will also be returned in %rax.

5.1.3. Argument Passing

Integral and Pointer Arguments

Integral and pointer arguments are passed to a function using the next available register of the sequence %rdi, %rsi, %rdx, %rcx, %r8, %r9. After this list of registers has been exhausted, all remaining integral and pointer arguments are passed to the function via the stack.

Floating-Point Arguments

Float and double arguments are passed to a function using the next available XMM register taken in the order from %xmm0 to %xmm7. After this list of registers has been exhausted, all remaining float and double arguments are passed to the function via the stack.

Structure and Union Arguments

Structure and union arguments can be passed to a function in either registers or on the stack. The size and type of the structure or union determine how it is passed. If a structure or union is larger than 16 bytes, it is passed to the function in memory.

To determine whether a 16-byte or smaller structure or union can be passed to a function in one or two registers, examine the first eight bytes of the structure or union. The type or types of the structure or union’s fields making up these eight bytes determine how these eight bytes will be passed. If the eight bytes contain at least one integral type, the eight bytes will be passed in the first available general purpose register of the sequence %rdi, %rsi, %rdx, %rcx, %r8, %r9 even if non-integral types are also present in the eight bytes. If the eight bytes only contain floating point types, these eight bytes will be passed in the first available XMM register of the sequence from %xmm0 to %xmm7.

If the structure or union is larger than eight bytes but smaller than 17 bytes, examine the type or types of the fields making up the second eight bytes of the structure or union. If the eight bytes contain at least one integral type, the eight bytes will be passed in the next available general purpose register of the sequence %rdi, %rsi, %rdx, %rcx, %r8, %r9 even if non-integral types are also present in the eight bytes. If these eight bytes only contain floating point types, these eight bytes will be passed in the next available XMM register of the sequence from %xmm0 to %xmm7.

If the first or second eight bytes of the structure or union cannot be passed in a register for some reason, the entire structure or union must be passed in memory.

Passing Arguments on the Stack

If there are arguments left after every argument register has been allocated, the remaining arguments are passed to the function on the stack. The unassigned arguments are pushed on the stack in reverse order, with the last argument pushed first.

Parameter Passing

Table 18 shows the register allocation and stack frame offsets for the function declaration and call shown in the following example. Both table and example are adapted from System V Application Binary Interface: AMD64 Architecture Processor Supplement.

typedef struct {
    int a, b;
    double d; 
    } 
    structparam; 
    structparam s;
    int e, f, g, h, i, j, k; 
    float flt;  
    double m, n; 
    extern void func(int e, int f, structparam s, int g, int h,  
    float flt, double m, double n, int i, int j, int k);
    void func2() 
    {  
    func(e, f, s, g, h, flt, m, n, i, j, k); 
    }
Table 18. Register Allocation for Example A-2
General Purpose Registers Floating Point Registers Stack Frame Offset
%rdi: e %xmm0: s.d 0: j
%rsi: f %xmm1: flt 8: k
%rdx: s.a,s.b %xmm2: m  
%rcx: g %xmm3: n  
%r8: h    
%r9: i    

Implementing a Stack

In general, compilers and programmers must maintain a software stack. The stack pointer, register %rsp, is set by the operating system for the application when the program is started. The stack must grow downwards from high addresses.

A separate frame pointer enables calls to routines that change the stack pointer to allocate space on the stack at run-time (e.g. alloca). Some languages can also return values from a routine allocated on stack space below the original top-of-stack pointer. Such a routine prevents the calling function from using %rsp-relative addressing for values on the stack. If the compiler does not call routines that leave %rsp in an altered state when they return, a frame pointer is not needed and may not be used if the compiler option -⁠Mnoframe is specified.

The stack must be kept aligned on 16-byte boundaries.

Variable Length Parameter Lists

Parameter passing in registers can handle a variable number of parameters. The C language uses a special method to access variable-count parameters. The stdarg.h and varargs.h files define several functions to access these parameters. A C routine with variable parameters must use the va_start macro to set up a data structure before the parameters can be used. The va_arg macro must be used to access the successive parameters.

For calls that use varargs or stdargs, the register %rax acts as a hidden argument whose value is the number of XMM registers used in the call.

C Parameter Conversion

In C, for a called prototyped function, the parameter type in the called function must match the argument type in the calling function. If the called function is not prototyped, the calling convention uses the types of the arguments but promotes char or short to int, and unsigned char or unsigned short to unsigned int and promotes float to double, unless you use the -⁠Msingle option. For more information on the -⁠Msingle option, refer to -M Options by Category .

Calling Assembly Language Programs

The following example shows a C program calling an assembly-language routine sum_3.

C Program Calling an Assembly-language Routine

/* File: testmain.c */
#include <stdio.h>
int
main() {
 long l_para1 = 2;
 float f_para2 = 1.0;
 double d_para3 = 0.5;
 float f_return;
 extern float sum_3(long para1, float para2, double para3);
 f_return = sum_3(l_para1, f_para2, d_para3);
 printf("Parameter one, type long = %ld\n", l_para1);
 printf("Parameter two, type float = %f\n", f_para2);
 printf("Parameter three, type double = %f\n", d_para3);
 printf("The sum after conversion = %f\n", f_return);
 return 0;
}
# File: sum_3.s
# Computes ( para1 + para2 ) + para3
	.text
	.align	16
	.globl	sum_3
sum_3:
	pushq	%rbp
	movq	%rsp, %rbp
	cvtsi2ssq %rdi, %xmm2
	addss	%xmm0, %xmm2
	cvtss2sd %xmm2,%xmm2
	addsd %xmm1, %xmm2
	cvtsd2ss %xmm2, %xmm2
	movaps	%xmm2, %xmm0
	popq	%rbp
	ret
	.type	sum_3, @function
	.size	sum_3,.-sum_3

5.1.4. Linux86-64 Fortran Supplement

Sections A2.4.1 through A2.4.4 of the ABI for x64 Linux and macOS define the Fortran supplement. The register usage conventions set forth in that document remain the same for Fortran.

Fortran Fundamental Types

Table 19. Linux86-64 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 memory. The caller provides space for the return value and passes the address of this storage as if it were the first argument to the function.

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 %rax.

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 or COMPLEX, 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 20 provides the C/C⁠+⁠+ data type corresponding to each Fortran data type.

Table 20. 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