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

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon added inline comments.


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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]
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LuoYuanke wrote:
> 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.
These adds were just used for simplicity to make the result dependent on all 3 intrinsics.

We'd avoid all of the intrinsics-upgrade changes if we just changed these add ops to something else, preferably something that we're not going to add to foldSelectWithIdentityConstant in the future.

Alternatively we split these tests into the 3 normal / {k} / {k}{z} variants


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D119654/new/

https://reviews.llvm.org/D119654