-march=xxx

Scott Alfter salfter at salfter.dyndns.org
Thu Jan 25 10:01:19 PST 2001


On Tue, Jan 23, 2001 at 11:29:02AM -0800, Mike Hildebrandt wrote:
> I'm not sure about i686, but i586 works fine on my AMD K6-2.  You can also
> use -march=k6, but I'm not sure how different that is from i586.

The differences are more than likely to account for microarchitecural
differences between the Pentium and the K6 (different execution times for an
instruction, different pipelining, etc.).  I built up a K6-optimized LFS on
a P5-133 (it wasn't doing anything else at the time), and it ran OK (if not
optimally) on that.  AFAIK, there's no K6-only code that would be generated
with -march=k6.  (The only instructions that wouldn't be present in an Intel
processor would be the 3DNow! instructions.  gcc isn't even generating MMX
code yet, let alone 3DNow!/SSE/SSE2 code.)

  _/_
 / v \
(IIGS(  Scott Alfter (salfter at salfter.dyndns.org)
 \_^_/  http://salfter.dyndns.org
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