User's Guide

Compiler Options for the 64-bit Environment

The compiler options that are described in this section enable you to do the following:

• Develop applications for the 64-bit environment.
• Help migrate source code from the 32-bit environment to a 64-bit environment.

Some of these options already exist in the 32-bit environment, but have new settings particular to the 64-bit architecture. This section only covers the new settings for these cases. The options that are grouped here are primarily for developers who are targetting 64-bit platforms.

-q32 Option

Syntax:

-q32

Enables 32-bit compilation bit mode (or, more briefly, 32-bit mode) support in a 64-bit environment. The -q32 option indicates the compilation bit mode, and together with the -qarch option, determines the target machines that the 32-bit executable will run on.

Rules:

• The default integer and default real size are 4 bytes in 32-bit mode.
• The default integer pointer size is 4 bytes in 32-bit mode.
• 32-bit object modules are created in 32-bit mode.
• -q32 is the default if you have not specified either -q32 or -q64, and if you have not set the OBJECT_MODE environment variable. For a description of the OBJECT_MODE environment variable, see Default Bit Mode.
• -q64 may override -q32.
• All settings for -qarch are compatible with -q32. If you specify -q32, the default -qarch suboption is com and the default -qtune suboption for -q32 is pwr2.
• The LOC intrinsic returns an INTEGER(4) value.

Examples

• Using 32-bit compilation mode and targetting the 601 architecture:

     -qarch=601 -q32
  

• Now keep the same compilation mode, but change the target to RS64I:

     -qarch=601 -q32 -qarch=rs64a
  

  Notice that the last setting for -qarch wins.

• Now keep the same target, but change the compilation mode to 64-bit:

     -qarch=601 -q32 -qarch=rs64a -q64
  

  Notice that specifying -q64 overrides the earlier instance of -q32.

-q64 Option

Syntax:

-q64

Indicates the 64-bit compilation bit mode and, together with the -qarch option, determines the target machines on which the 64-bit executable will run. The -q64 option indicates that the object module will be created in 64-bit object format and that the 64-bit instruction set will be generated. Note that you may compile in a 32-bit environment to create 64-bit objects, but you must link them in a 64-bit environment with the -q64 option.

The -q64 option is also compatible with the C for AIX compiler and the tools provided on AIX 4.3.

Rules:

• Settings for -qarch that are compatible with -q64 are as follows:
  • -qarch=auto (if compiling on a 64-bit system)
  • -qarch=com
  • -qarch=ppc
  • -qarch=rs64a
  • -qarch=rs64b
  • -qarch=pwr3
• The default -qarch setting for -q64 is ppc.
• 64-bit object modules are created in 64-bit mode.
• -q32 may override -q64.
• -q64 will override a conflicting setting for -qarch. For example,

  -q64 -qarch=601
  

  will result in the setting -q64 -qarch=ppc along with a warning message.
• The default tune setting for -q64 is -qtune=pwr3.
• The default integer and default real size is 4 bytes in 64-bit mode.
• The default integer pointer size is 8 bytes in 64-bit mode.
• The maximum array size increases to approximately 2**40 bytes (in static storage) or 2**60 bytes (in dynamic allocation on the heap). The maximum dimension bound range is extended to -2**63, 2**63-1 bytes. The maximum array size for array constants has not been extended and will remain the same as the maximum in 32-bit mode. The maximum array size that you can initialize is 2**28 bytes.
• The maximum iteration count for array constructor implied DO loops increases to 2**63-1 bytes.
• The maximum character variable length extends to approximately 2**40 bytes. The maximum length of character constants and subobjects of constants remains the same as in 32-bit mode, which is 32 767 bytes (32 KB).
• The LOC intrinsic returns an INTEGER(8) value.

When you use -qautodbl=dblpad in 64-bit mode, you should use -qintsize=8 to promote INTEGER(4) to INTEGER(8) for 8 byte integer arithmetic.

Examples

• 64-bit compilation that targets the RS64I:

  -q32 -qarch=rs64a -q64
  

• 64-bit compilation that targets the common group of 64-bit architectures (which currently consists only of the RS64I, RS64II, and POWER3):

  -q64 -qarch=com
  

• Conflicting -qarch option with -q64:

  -qarch=601 -q64
  

  results in a setting of -q64 -qarch=ppc and a warning message.
• Conflicting -qarch option with -q64:

  -q64 -qarch=601
  

  results in a setting of -q64 -qarch=ppc and a warning message.

-qarch=rs64a Option

Syntax:

-qarch=rs64a

Indicates that the target architecture for the executable to run on is the RS64I.

Rules:

• You can specify the -qarch=rs64a option with either the -q32 or -q64 option.

• The RS64I belongs to the 64-bit common architecture group that is specified with the combination of options -qarch=com -q64.

• The supported tune option for -qarch=rs64a is -qtune=rs64a. The default tune option for -qarch=rs64a is -qtune=rs64a.

Related Information:

For more information on the -qarch compiler option, see -qarch Option.

-qarch=rs64b Option

Syntax:

-qarch=rs64b

Indicates that the target architecture for the executable to run on is the RS64II.

Rules:

• You can specify the -qarch=rs64b option with either the -q32 or -q64 option.

• The RS64II belongs to the 64-bit common architecture group that is specified with the combination of options -qarch=com -q64.

• The supported tune option for -qarch=rs64b is -qtune=rs64b. The default tune option for -qarch=rs64b is -qtune=rs64b.

Related Information:

For more information on the -qarch compiler option, see -qarch Option.

-qtune=rs64a Option

Syntax:

-qtune=rs64a

Tune optimizations for the PowerPC RS64I processor.

You can specify the -qtune=rs64a option when you also specify any of the following options:

• -qarch=rs64a
• -qarch=ppc
• -qarch=com
• -qarch=auto (if compiling on an RS64I system)

The -qtune=rs64a option is the default for the -qarch=rs64a option or the -q64 option.

Related Information:

For more information on the -qtune compiler option, see -qtune Option.

-qtune=rs64b Option

Syntax:

-qtune=rs64b

Tune optimizations for the PowerPC RS64II processor.

You can specify the -qtune=rs64b option when you also specify any of the following options:

• -qarch=rs64b
• -qarch=ppc
• -qarch=com
• -qarch=auto (if compiling on an RS64II system)

The -qtune=rs64b option is the default for the -qarch=rs64b option or the -q64 option.

Related Information:

For more information on the -qtune compiler option, see -qtune Option.

-qwarn64 Option

Syntax:

-qwarn64 | -qnowarn64

Aids in porting code from a 32-bit environment to a 64-bit environment, by detecting the truncation of an 8-byte integer pointer to 4 bytes. The -qwarn64 option uses informational messages to identify statements that may cause problems with the 32-bit to 64-bit migration. The option name provides compatibility with the C for AIX compiler.

Rules:

• The default setting is -qnowarn64.
• You can use the -qwarn64 option in both 32-bit and 64-bit modes.
• The compiler flags the following situations with informational messages:
  • The assignment of a reference to the LOC intrinsic to an INTEGER(4) variable.
  • The assignment between an INTEGER(4) variable or INTEGER(4) constant and an integer pointer.
  • The specification of an integer pointer within a common block. We recommend the -qextchk option for common block length changes.
  • The specification of an integer pointer within an equivalence statement.
• We recommend the -qextchk option and interface blocks for argument checking.