diff --git a/llvm/lib/IR/AutoUpgrade.cpp b/llvm/lib/IR/AutoUpgrade.cpp
--- a/llvm/lib/IR/AutoUpgrade.cpp
+++ b/llvm/lib/IR/AutoUpgrade.cpp
@@ -2417,7 +2417,7 @@
                                           EltTy->getPointerTo());
       Value *Load = Builder.CreateLoad(EltTy, Cast);
       Type *I32Ty = Type::getInt32Ty(C);
-      Rep = UndefValue::get(VecTy);
+      Rep = PoisonValue::get(VecTy);
       for (unsigned I = 0; I < EltNum; ++I)
         Rep = Builder.CreateInsertElement(Rep, Load,
                                           ConstantInt::get(I32Ty, I));
diff --git a/llvm/lib/Target/NVPTX/NVPTXGenericToNVVM.cpp b/llvm/lib/Target/NVPTX/NVPTXGenericToNVVM.cpp
--- a/llvm/lib/Target/NVPTX/NVPTXGenericToNVVM.cpp
+++ b/llvm/lib/Target/NVPTX/NVPTXGenericToNVVM.cpp
@@ -212,7 +212,7 @@
   // If any of the elements has been  modified, construct the equivalent
   // vector or aggregate value with a set instructions and the converted
   // elements.
-  Value *NewValue = UndefValue::get(C->getType());
+  Value *NewValue = PoisonValue::get(C->getType());
   if (isa<ConstantVector>(C)) {
     for (unsigned i = 0; i < NumOperands; ++i) {
       Value *Idx = ConstantInt::get(Type::getInt32Ty(M->getContext()), i);
diff --git a/llvm/unittests/IR/IRBuilderTest.cpp b/llvm/unittests/IR/IRBuilderTest.cpp
--- a/llvm/unittests/IR/IRBuilderTest.cpp
+++ b/llvm/unittests/IR/IRBuilderTest.cpp
@@ -878,7 +878,7 @@
   auto VecTy = FixedVectorType::get(Builder.getInt64Ty(), 4);
   auto Elt1 = Builder.getInt64(-1);
   auto Elt2 = Builder.getInt64(-2);
-  Value *Vec = UndefValue::get(VecTy);
+  Value *Vec = PoisonValue::get(VecTy);
   Vec = Builder.CreateInsertElement(Vec, Elt1, Builder.getInt8(1));
   Vec = Builder.CreateInsertElement(Vec, Elt2, 2);
   auto X1 = Builder.CreateExtractElement(Vec, 1);
diff --git a/llvm/unittests/IR/PatternMatch.cpp b/llvm/unittests/IR/PatternMatch.cpp
--- a/llvm/unittests/IR/PatternMatch.cpp
+++ b/llvm/unittests/IR/PatternMatch.cpp
@@ -940,8 +940,8 @@
   VecElemIdxs.push_back(ConstantInt::get(i32, 2));
   auto *IdxVec = ConstantVector::get(VecElemIdxs);
 
-  Value *UndefVec = UndefValue::get(VecTy);
-  Value *VI1 = IRB.CreateInsertElement(UndefVec, IRB.getInt8(1), (uint64_t)0);
+  Value *PoisonVec = PoisonValue::get(VecTy);
+  Value *VI1 = IRB.CreateInsertElement(PoisonVec, IRB.getInt8(1), (uint64_t)0);
   Value *VI2 = IRB.CreateInsertElement(VI1, Val2, Val);
   Value *VI3 = IRB.CreateInsertElement(VI1, Val2, (uint64_t)1);
   Value *VI4 = IRB.CreateInsertElement(VI1, IRB.getInt8(2), Val);