Intel ARCHITECTURE IA-32 - Manual (Page 438)

IA-32 Intel® Architecture Optimization
A-4
default, and targets the Intel Pentium 4 processor and subsequent
processors. Code produced will run on any Intel architecture 32-bit
processor, but will be optimized specifically for the targeted processor.
Automatic Processor Dispatch Support
(-Qx[extensions] and -Qax[extensions])
The -Qx[extensions] and -Qax[extensions] options provide
support to generate code that is specific to processor-instruction
extensions. The corresponding options on Linux are -x[extensions] and
-ax[extensions].
-Qx[extensions] generates specialized code to run exclusively on
the processors indicated by the extension(s).
-Qax[extensions] generates code specialized to processors which
support the specified extensions, but also
generates generic IA-32 code. The generic code
usually executes slower than the specialized
version. A runtime check for the processor type
is made to determine which code executes.
You can specify the same extensions for either option as follows:
i Pentium II and Pentium III processors, which use the
CMOV and FCMOV instructions.
M Pentium processor with MMX technology, Pentium II,
and Pentium III processors.
K Streaming SIMD Extensions. Includes the i and M
extensions.
W Streaming SIMD Extensions 2. Includes the i, M,
and K extensions.
B Streaming SIMD Extensions 2 and optimizations for
the Intel Pentium M processor. Includes the
i, M,
K,k and W extensions.
P Streaming SIMD Extensions 3. Includes the i, M, K,
and W extensions.