[PATCH] D127073: [SLP] Treat undef as any other constant

[Harald van Dijk via Phabricator via llvm-commits]

hvdijk added inline comments.


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Comment at: llvm/test/Transforms/SLPVectorizer/X86/diamond_broadcast_extra_shuffle.ll:121
+; CHECK-NEXT:    [[TMP0:%.*]] = insertelement <4 x i32> <i32 poison, i32 undef, i32 poison, i32 poison>, i32 [[LD]], i32 0
+; CHECK-NEXT:    [[SHUFFLE:%.*]] = shufflevector <4 x i32> [[TMP0]], <4 x i32> poison, <4 x i32> <i32 0, i32 0, i32 0, i32 1>
+; CHECK-NEXT:    [[SHUFFLE1:%.*]] = shufflevector <4 x i32> [[TMP0]], <4 x i32> poison, <4 x i32> <i32 0, i32 0, i32 1, i32 0>
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nlopes wrote:
> this is also a regression.
> Before we were doing a broadcast of %ld and doing `mul %ld, %ld` in all 4 lanes, as the undefs were replaced with %ld.
Replacing undef with %ld is only valid if we can prove %ld is not poison, and we have no checks for that. It might be valid here, but it is not valid in general, is it?


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  https://reviews.llvm.org/D127073/new/

https://reviews.llvm.org/D127073