[PATCH] D40078: [x86][icelake]VAES introduction

[coby via Phabricator via llvm-commits]

coby added inline comments.


================
Comment at: lib/Support/Host.cpp:433
   FEATURE_SHA,
+  FEATURE_VAES,
 };
----------------
craig.topper wrote:
> coby wrote:
> > craig.topper wrote:
> > > This isn't needed if it isn't used by code in getHostCPUName
> > I see, thanks.
> > I assume same logic is to be applied to entries like FEATURE_PCLMUL?
> The first 31 values need to be kept in sync with compiler-rt since we have a copy and paste of some of this code in compiler-rt. For runtime CPU detection in compiled binaries. It makes diffing easier if they are synchronized. I just committed some comments that clarify that a little better. I'm hoping to move this enum to a header file that clang can use as a proxy for what's in compiler-rt as well since clang can't include any files from the compiler-rt project. Currently we just have a separate copy code in clang too.
I see. thanks for the elaborated explanation!


================
Comment at: lib/Target/X86/X86.td:174
+                       "Promote selected AES instructions to AVX512/AVX registers",
+                        [FeatureAVX]>;
 def FeatureTBM     : SubtargetFeature<"tbm", "HasTBM", "true",
----------------
craig.topper wrote:
> coby wrote:
> > craig.topper wrote:
> > > Should this imply FeatureAES as well?
> > not sure,
> > it has no direct dependency afaiu, like AVX, for example, i.e. it does not imply that AES insns are apparent.
> > practically, if you want to use 'vaesenc', for example, you ought to have a Key, so you'll probably want to use 'aeskeygenassist' which is on AES solely, but than again - it (vaes) may still be provided on its own, so I find it yet questionable
> > 
> > 
> The EVEX->VEX pass is going to turn 128-bit EVEX encoded AES instructions into VEX encoded versions. So those instructions better be available with VAES.
isn't it implies that only the (AES) subset implemented by VAES need to be available?


Repository:
  rL LLVM

https://reviews.llvm.org/D40078