FreeBSD I386 and AMD64 options

These `-m' options are defined for the
[url=javascript:;]i386[/url]
and x86-64 family of computers:
-mtune=cpu-type
Tune to cpu-type everything applicable about the generated code, except for the ABI and the set of available instructions. The choices for cpu-type are:
generic
Produce code optimized for the most common IA32/AMD64/EM64T processors. If you know the CPU on which your code will run, then you should use the corresponding -mtune option instead of -mtune=generic. But, if you do not know exactly what CPU users of your application will have, then you should use this option.
As new processors are deployed in the marketplace, the behavior of this option will change. Therefore, if you upgrade to a newer version of GCC, the code generated option will change to reflect the processors that were most common when that version of GCC was released.
There is no -march=generic option because -march indicates the instruction set the compiler can use, and there is no generic instruction set applicable to all processors. In contrast, -mtune indicates the processor (or, in this case, collection of processors) for which the code is optimized.
native
This selects the CPU to tune for at compilation time by determining the processor type of the compiling machine. Using -mtune=native will produce code optimized for the local machine under the constraints of the selected instruction set. Using -march=native will enable all instruction subsets supported by the local machine (hence the result might not run on different machines).
i386
Original Intel's i386 CPU.
i486
Intel's i486 CPU. (No scheduling is implemented for this chip.)
i586, pentium
Intel Pentium CPU with no MMX support.
pentium-mmx
Intel PentiumMMX CPU based on Pentium core with MMX instruction set support.
pentiumpro
Intel PentiumPro CPU.
i686
Same as generic, but when used as march option, PentiumPro instruction set will be used, so the code will run on all i686 family chips.
pentium2
Intel Pentium2 CPU based on PentiumPro core with MMX instruction set support.
pentium3, pentium3m
Intel Pentium3 CPU based on PentiumPro core with MMX and SSE instruction set support.
pentium-m
Low power version of Intel Pentium3 CPU with MMX, SSE and SSE2 instruction set support. Used by Centrino notebooks.
pentium4, pentium4m
Intel Pentium4 CPU with MMX, SSE and SSE2 instruction set support.
prescott
Improved version of Intel Pentium4 CPU with MMX, SSE, SSE2 and SSE3 instruction set support.
nocona
Improved version of Intel Pentium4 CPU with 64-bit extensions, MMX, SSE, SSE2 and SSE3 instruction set support.
core2
Intel Core2 CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3 and SSSE3 instruction set support.
k6
AMD K6 CPU with MMX instruction set support.
k6-2, k6-3
Improved versions of AMD K6 CPU with MMX and 3dNOW! instruction set support.

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