XL Fortran Enterprise Edition for AIX : User's Guide - IBM

-qarch Option
Syntax
-qarch=architecture
Controls which instructions the compiler can generate. Changing the default can
improve performance but might produce code that can only be run on specific
machines.
In general, the -qarch option allows you to target a specific architecture for the
compilation. For any given -qarch setting, the compiler defaults to a specific,
matching -qtune setting, which can provide additional performance improvements.
The resulting code may not run on other architectures, but it will provide the best
performance for the selected architecture. To generate code that can run on more
than one architecture, specify a -qarch suboption, such as com, ppc, or ppc64, that
supports a group of architectures; doing this will generate code that runs on all
supported architectures, PowerPC, or 64–bit PowerPC architectures, respectively.
When a -qarch suboption is specified with a group argument, you can specify
-qtune as either auto, or provide a specific architecture in the group. In the case of
-qtune=auto, the compiler will generate code that runs on all architectures in the
group specified by the -qarch suboption, but select instruction sequences that have
best performance on the architecture of the machine used to compile. Alternatively
you can target a specific architecture for tuning performance.
Arguments
The choices for architecture are:
auto
com
pwr
pwr2
Automatically detects the specific architecture of the compiling machine. It
assumes that the execution environment will be the same as the
compilation environment.
You can run the executable file that the compiler generated on any
hardware platform supported by the compiler, because the file contains
only instructions that are common to all machines. This choice is the
default if you specify -q32.
If you specify the -q64 and -qarch=com options together, the target
platform is 64-bit, and the -qarch option is silently upgraded to ppc64grsq.
The instruction set will be restricted to those instructions common to all
64-bit machines. See “Using XL Fortran in a 64-Bit Environment” on page
279 for details. Also, the rndsngl suboption of the -qfloat option is
automatically turned on and cannot be turned off. While this yields better
performance on PowerPC systems, you may get slightly different results
than if you compile with -qarch=com and -q32.
You can run the executable file on any POWER or POWER2 hardware
platform. Because executable files for these platforms may contain
instructions that are not available on PowerPC systems, they may be
incompatible with those newer systems, or they may run more slowly
because missing instructions are emulated through software traps.
You can run the executable file on any POWER2 hardware platform.
Because executable files for these platforms may contain instructions that
are not available on POWER and PowerPC (including POWER3) systems,
they may be incompatible with those systems.
Note that pwrx is a synonym for pwr2, but pwr2 is preferable.
XL Fortran Compiler-Option Reference 127