[PATCH] D118534: [X86] Update generic process model to x86-64-v3 to match with GCC

Sat Jan 29 17:29:44 PST 2022

pengfei added inline comments.

================
Comment at: llvm/lib/Target/X86/X86.td:1491
+                [FeatureX87, FeatureCMPXCHG8B, Feature64Bit],
+                ProcessorFeatures.HSWTuning>;
+
----------------
craig.topper wrote:
> pengfei wrote:
> > RKSimon wrote:
> > > The old tuning flags didn't match all of SandyBridge's - do we really want to match all of Haswell's?
> > The GCC [[ https://gcc.gnu.org/onlinedocs/gcc/x86-Options.html | doc ]] says `generic` will be updated with compiler iteration. I think it's reasonable since the common processors will be upgraded with time.
> This turns in some fast shuffle flags that aren’t used by any AMD CPU except znver3. Do those flags make sense for generic?
I saw someone checked on znver1 and gave a conclusion the haswell tuning works reasonably well for both cores and zens. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81616
I have no idea how to check it with LLVM, so I'll remove the shuffle flags for conservative.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D118534/new/

https://reviews.llvm.org/D118534