diff --git a/llvm/lib/IR/ConstantFold.cpp b/llvm/lib/IR/ConstantFold.cpp
--- a/llvm/lib/IR/ConstantFold.cpp
+++ b/llvm/lib/IR/ConstantFold.cpp
@@ -710,9 +710,9 @@
       ElementCount::get(MaskNumElts, isa<ScalableVectorType>(V1VTy));
   Type *EltTy = V1VTy->getElementType();
 
-  // Undefined shuffle mask -> undefined value.
+  // Poison shuffle mask -> poison value.
   if (all_of(Mask, [](int Elt) { return Elt == PoisonMaskElem; })) {
-    return UndefValue::get(VectorType::get(EltTy, MaskEltCount));
+    return PoisonValue::get(VectorType::get(EltTy, MaskEltCount));
   }
 
   // If the mask is all zeros this is a splat, no need to go through all
diff --git a/llvm/lib/IR/Instructions.cpp b/llvm/lib/IR/Instructions.cpp
--- a/llvm/lib/IR/Instructions.cpp
+++ b/llvm/lib/IR/Instructions.cpp
@@ -2290,7 +2290,7 @@
   SmallVector<Constant *, 16> MaskConst;
   for (int Elem : Mask) {
     if (Elem == PoisonMaskElem)
-      MaskConst.push_back(UndefValue::get(Int32Ty));
+      MaskConst.push_back(PoisonValue::get(Int32Ty));
     else
       MaskConst.push_back(ConstantInt::get(Int32Ty, Elem));
   }
diff --git a/llvm/test/Transforms/InstCombine/shufflevec-constant.ll b/llvm/test/Transforms/InstCombine/shufflevec-constant.ll
--- a/llvm/test/Transforms/InstCombine/shufflevec-constant.ll
+++ b/llvm/test/Transforms/InstCombine/shufflevec-constant.ll
@@ -18,7 +18,7 @@
 
 define <4 x i1> @shuffle_undef_fixed() {
 ; CHECK-LABEL: @shuffle_undef_fixed(
-; CHECK-NEXT:    ret <4 x i1> undef
+; CHECK-NEXT:    ret <4 x i1> poison
 ;
   %S = shufflevector <4 x i1> zeroinitializer, <4 x i1> zeroinitializer, <4 x i32> undef
   ret <4 x i1> %S
@@ -26,7 +26,7 @@
 
 define <vscale x 4 x i1> @suffle_undef_scalable() {
 ; CHECK-LABEL: @suffle_undef_scalable(
-; CHECK-NEXT:    ret <vscale x 4 x i1> undef
+; CHECK-NEXT:    ret <vscale x 4 x i1> poison
 ;
   %S = shufflevector <vscale x 4 x i1> zeroinitializer, <vscale x 4 x i1> zeroinitializer, <vscale x 4 x i32> undef
   ret <vscale x 4 x i1> %S