[PATCH] D29874: [X86] Generate VZEROUPPER for Skylake-avx512

[Craig Topper via Phabricator via llvm-commits]

craig.topper added inline comments.


================
Comment at: lib/Target/X86/X86VZeroUpper.cpp:225
 
     // The VZEROUPPER instruction resets the upper 128 bits of all AVX
     // registers. In addition, the processor changes back to Clean state, after
----------------
aaboud wrote:
> aaboud wrote:
> > craig.topper wrote:
> > > aaboud wrote:
> > > > craig.topper wrote:
> > > > > This comments is stale with ZMM. It's not upper 128 bits.
> > > > Actually, this is what it does. even for the ZMM registers it reset the upper 128bits of the YMM corresponding register. Is not it?
> > > > 
> > > > The important behavior is the next sentence, which emphasize that processor changes back to Clean state.
> > > Doesn't it clear the upper 384 bits of ZMM? The comment itself doesn't say YMM. It just says "AVX registers".
> > I am fine with rephrasing the comment, though AVX registers does not include any ZMM, just YMM.
> > Do you think I should replace YMM with ZMM?
> > I am fine with rephrasing the comment, though AVX registers does not include any ZMM, just YMM.
> > Do you think I should replace YMM with ZMM?
> 
> I meant to say: Do you think I should replace AVX with YMM (or YMM0-16)?
Probably should at least say YMM. "AVX register" is potentially confusing since the letters AVX appear in AVX512.


https://reviews.llvm.org/D29874