-mcpu (-qarch)
Category
Pragma equivalent
None.
Purpose
Specifies the processor architecture for which the code (instructions) should be generated.
Syntax
.-=power8-. +-=pwr8---+ >>- -m--cpu--+---------+---------------------------------------><
Defaults
- -mcpu=pwr8, -mcpu=power8, or -qarch=pwr8
- -qarch=auto when -O4 or -O5 is in effect
Parameters
- auto
- Automatically detects the specific architecture of the compiling machine. It assumes that the execution environment will be the same as the compilation environment. This option is implied if the -O4 or -O5 option is set or implied. You can specify the auto suboption with -qarch only.
- pwr8
- Produces object code containing instructions that run on the POWER8® hardware platforms.
- power8
- Produces object code containing instructions that run on the POWER8 hardware platforms. You can specify this suboption with -march only.
Usage
For any given -mcpu or -qarch setting, the compiler defaults to a specific, matching -mtune or -qtune setting, which can provide additional performance improvements. For detailed information about using -mcpu (-qarch) and -mtune (-qtune) together, see -mtune (-qtune).
The POWER8 architecture supports graphics, square root, Vector Multimedia Extension (VMX) processing, Vector Scalar Extension (VSX) processing, hardware transactional memory, and cryptography.
Predefined macros
See Macros related to architecture settings for a list of macros that are predefined by -mcpu (-qarch) suboptions.
Examples
To specify that the executable
program testing compiled from myprogram.c is
to run on a computer with VSX instruction
support, enter:
xlc -o testing myprogram.c -mcpu=pwr8
