arch

Option Type Default Value #pragma options C C++
-qoption arch=com - x x

Syntax 

    -qarch=suboption

Purpose
Specifies the general processor architecture for which the code (instructions) should be generated.

Notes
If you want maximum performance on a specific architecture and will not be using the program on other architectures, use the appropriate architecture option. You can specify the architecture using the following basic suboptions:

com In 32-bit execution mode, produces object code that contains instructions that will run on all the POWER, POWER2*, and PowerPC* hardware platforms (that is, the instructions generated are common to all platforms. Using -qarch=com is referred to as compiling in common mode. 

In 64-bit mode, produces object code that will run on all the 64-bit PowerPC hardware platforms but not 32-bit-only platforms.

This is the default option unless the -O4 compiler option was specified.

Defines the _ARCH_COM macro and produces portable programs.

pwr Produces object code that contains instructions that will run on any of the POWER and POWER2 and 601 hardware platforms. Defines the _ARCH_PWR macro.
pwr2 Produces object code that contains instructions that will run on the POWER2 hardware platforms including pwr2s and p2sc. Defines the _ARCH_PWR and _ARCH_PWR2 macros.
pwr3 Produces object code that contains instructions that will run on the POWER3 hardware platforms. Defines the _ARCH_PWR and _ARCH_PWR3 macros.
ppc In 32-bit mode, produces object code that contains instructions that will run on any of the 32-bit PowerPC hardware platforms. This suboption will cause the compiler to produce single-precision instructions to be used with single-precision data.

In 64-bit mode, produces object code that will run on any of the 64-bit PowerPC hardware platforms but not 32-bit-only platforms.

Defines the _ARCH_PPC macro.

ppcgr In 32-bit mode, produces object code that contains optional graphics instructions for PowerPC processors.

In 64-bit mode, produces object code that contains optional graphics instructions for 64-bit PowerPC hardware platforms but not 32-bit-only platforms.

Defines the _ARCH_PPC and _ARCH_PPCGR macros.

auto Produces object code that contains instructions that will run on the hardware platform on which it is compiled.

Note: Using -qarch=ppc or any ppc family architecture with -qfloat=hssngl or -qfloat=hsflt may produce incorrect results on rs64b or future systems.

You can use -qarch=suboption with -qtune=suboption. -qarch=suboption specifies the architecture for which the instructions are to be generated, and -qtune=suboption specifies the target platform for which the code is optimized.

Default
The default setting of  -qarch is -qarch=com unless the OBJECT_MODE environment variable is set to 64.

Example
To specify that the executable program testing compiled from myprogram.c is to run on a computer with a 32-bit PowerPC architecture, enter:

xlC -o testing myprogram.c -qarch=ppc


Specify Compiler Options for Architecture-Specific, 32- or 64-bit Compilation


Acceptable Compiler Mode and Processor Architecture Combinations
List of Batch Compiler Options and Their Defaults
Options that Define the Compiler Object Code Produced
Equivalent Batch Compile-Link and Incremental Build Options