[llvm-branch-commits] [llvm] AMDGPU: Replace unused permlane inputs with poison instead of undef (PR #131288)

[Nuno Lopes via llvm-branch-commits]

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@@ -1115,7 +1115,7 @@ GCNTTIImpl::instCombineIntrinsic(InstCombiner &IC, IntrinsicInst &II) const {
   case Intrinsic::amdgcn_permlanex16_var: {
     // Discard vdst_in if it's not going to be read.
     Value *VDstIn = II.getArgOperand(0);
-    if (isa<UndefValue>(VDstIn))
+    if (isa<PoisonValue>(VDstIn))
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nunoplopes wrote:

I don't know how prevalent this intrinsic is, but I would maybe leave this one as-is to preserve compatibility with older IR. We can always do a search & replace later when we get rid of undef.
The rest LGTM, thanks!

https://github.com/llvm/llvm-project/pull/131288