ab added a comment.
Unless I'm misunderstanding, I believe this has much less impact than you're
thinking; there are three cases:
- x86_64: no change (-mno-mmx is guarded by x86)
- x86, with -mno-mmx: no change (because previously, we'd only set avx/avx512
for x86_64)
- x86, without -mno-mmx:
rjmccall added a comment.
This gives no-MMX priority over turning on SSE, which sounds like a major
change in behavior to me. There are definitely clients that specifically never
want to use MMX but do care deeply about SSE; my understanding is that modern
microarchitectures heavily punish
rjmccall added a comment.
In http://reviews.llvm.org/D12390#234458, @ab wrote:
Unless I'm misunderstanding, I believe this has much less impact than you're
thinking; there are three cases:
- x86_64: no change (-mno-mmx is guarded by x86)
- x86, with -mno-mmx: no change (because previously,
ab created this revision.
ab added a reviewer: rjmccall.
ab added a subscriber: cfe-commits.
One problem that came up in D12389 is that i386 doesn't know about the avx
ABIs. Judging by the commit that originally introduced the X86_64 check and
the avx ABI (r145652), it was just unnecessary.
