[PATCH] D119654: [SDAG] enable binop identity constant folds for add/sub

[LuoYuanke via Phabricator via llvm-commits]

LuoYuanke added inline comments.


================
Comment at: llvm/test/CodeGen/X86/avx512-intrinsics-upgrade.ll:4241
+; X86-NEXT:    vpaddq %zmm0, %zmm1, %zmm1 {%k1} ## encoding: [0x62,0xf1,0xf5,0x49,0xd4,0xc8]
+; X86-NEXT:    vmovdqa64 %zmm1, %zmm0 ## encoding: [0x62,0xf1,0xfd,0x48,0x6f,0xc1]
 ; X86-NEXT:    retl ## encoding: [0xc3]
----------------
LuoYuanke wrote:
> This vmovdqa64 is emitted because the function need to return value by zmm0. Not sure if it is a regression.
It seems fold select to its previous operands (psrl) is better, because the add operands is communitive so there is more chance to meet the hint (return register) of register allocator.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D119654/new/

https://reviews.llvm.org/D119654