On Wed, 26 Feb 2003, Nuno Teixeira wrote:
Does -march=k6-2 implies -m3dnow? Or -march=pentiumpro implies -mmmx?
I always thought that when I use -march it will enable other porcessor specific optimizations like mmx and 3dnow (if available).
IIRC, 166 and 180 Mhz PPros don't support MMX.
Neither do PPro's 200: CPU: Pentium Pro (199.43-MHz 686-class CPU) Origin = "GenuineIntel" Id = 0x619 Stepping = 9 Features=0xf9ff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,SEP,MTRR,PGE,MCA,CMOV>
I'm seeing differences in compiled code between simple -march=athlon-xp and -march=athlon-xp -mmmx -m3dnow -msse.
The documentation says the same: those options have to be enabled to use extended instruction sets. -march/-mcpu just optmizes boundaries of jump labels, variables, etc... - and sometimes the kind of instructions to use, eg. 'loop label' or 'dec bcx, jne label', but that's all, AFAIK.
So long,
Jens
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