[llvm] 31d8bdb - [Scalarizer] Fold -1 mask in shufflevector to poison instead of undef

[Nuno Lopes via llvm-commits]

Author: Nuno Lopes
Date: 2023-07-23T15:02:23+01:00
New Revision: 31d8bdbcad91c0b2547f0836406ce119fe0e11ea

URL: https://github.com/llvm/llvm-project/commit/31d8bdbcad91c0b2547f0836406ce119fe0e11ea
DIFF: https://github.com/llvm/llvm-project/commit/31d8bdbcad91c0b2547f0836406ce119fe0e11ea.diff

LOG: [Scalarizer] Fold -1 mask in shufflevector to poison instead of undef
Per latest LangRef

Added: 
    

Modified: 
    llvm/lib/Transforms/Scalar/Scalarizer.cpp

Removed: 
    


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diff  --git a/llvm/lib/Transforms/Scalar/Scalarizer.cpp b/llvm/lib/Transforms/Scalar/Scalarizer.cpp
index ec8e5c2eecc2e7..86b55dfd304a05 100644
--- a/llvm/lib/Transforms/Scalar/Scalarizer.cpp
+++ b/llvm/lib/Transforms/Scalar/Scalarizer.cpp
@@ -1109,7 +1109,7 @@ bool ScalarizerVisitor::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
   for (unsigned I = 0; I < VS->NumFragments; ++I) {
     int Selector = SVI.getMaskValue(I);
     if (Selector < 0)
-      Res[I] = UndefValue::get(VS->VecTy->getElementType());
+      Res[I] = PoisonValue::get(VS->VecTy->getElementType());
     else if (unsigned(Selector) < Op0.size())
       Res[I] = Op0[Selector];
     else