diff --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -4751,7 +4751,7 @@
       SmallVector<ValueList, 2> OperandsVec;
       for (unsigned I = 0, E = PH->getNumIncomingValues(); I < E; ++I) {
         if (!DT->isReachableFromEntry(PH->getIncomingBlock(I))) {
-          ValueList Operands(VL.size(), PoisonValue::get(PH->getType()));
+          ValueList Operands(VL.size(), UndefValue::get(PH->getType()));
           TE->setOperand(I, Operands);
           OperandsVec.push_back(Operands);
           continue;
diff --git a/llvm/test/Transforms/SLPVectorizer/X86/landing_pad.ll b/llvm/test/Transforms/SLPVectorizer/X86/landing_pad.ll
--- a/llvm/test/Transforms/SLPVectorizer/X86/landing_pad.ll
+++ b/llvm/test/Transforms/SLPVectorizer/X86/landing_pad.ll
@@ -10,7 +10,7 @@
 ; CHECK:       bb2.loopexit:
 ; CHECK-NEXT:    br label [[BB2:%.*]]
 ; CHECK:       bb2:
-; CHECK-NEXT:    [[TMP0:%.*]] = phi <4 x i32> [ [[SHUFFLE:%.*]], [[BB9:%.*]] ], [ poison, [[BB2_LOOPEXIT:%.*]] ]
+; CHECK-NEXT:    [[TMP0:%.*]] = phi <4 x i32> [ [[SHUFFLE:%.*]], [[BB9:%.*]] ], [ undef, [[BB2_LOOPEXIT:%.*]] ]
 ; CHECK-NEXT:    ret void
 ; CHECK:       bb3:
 ; CHECK-NEXT:    [[TMP1:%.*]] = phi <2 x i32> [ [[TMP5:%.*]], [[BB6:%.*]] ], [ poison, [[BB1:%.*]] ]
diff --git a/llvm/test/Transforms/SLPVectorizer/X86/malformed_phis.ll b/llvm/test/Transforms/SLPVectorizer/X86/malformed_phis.ll
--- a/llvm/test/Transforms/SLPVectorizer/X86/malformed_phis.ll
+++ b/llvm/test/Transforms/SLPVectorizer/X86/malformed_phis.ll
@@ -116,7 +116,7 @@
 ; CHECK:       bb2:
 ; CHECK-NEXT:    br label [[BB3]]
 ; CHECK:       bb3:
-; CHECK-NEXT:    [[TMP0:%.*]] = phi <2 x i32> [ undef, [[BB1]] ], [ poison, [[BB2:%.*]] ]
+; CHECK-NEXT:    [[TMP0:%.*]] = phi <2 x i32> [ undef, [[BB1]] ], [ undef, [[BB2:%.*]] ]
 ; CHECK-NEXT:    [[SHUFFLE:%.*]] = shufflevector <2 x i32> [[TMP0]], <2 x i32> poison, <8 x i32> <i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 1>
 ; CHECK-NEXT:    [[TMP1:%.*]] = extractelement <8 x i32> [[SHUFFLE]], i32 0
 ; CHECK-NEXT:    [[TMP2:%.*]] = insertelement <16 x i32> poison, i32 [[TMP1]], i32 0
diff --git a/llvm/test/Transforms/SLPVectorizer/X86/phi-unreachable-input-block.ll b/llvm/test/Transforms/SLPVectorizer/X86/phi-unreachable-input-block.ll
--- a/llvm/test/Transforms/SLPVectorizer/X86/phi-unreachable-input-block.ll
+++ b/llvm/test/Transforms/SLPVectorizer/X86/phi-unreachable-input-block.ll
@@ -15,7 +15,7 @@
 ; CHECK:       bb2:
 ; CHECK-NEXT:    br label [[BB3]]
 ; CHECK:       bb3:
-; CHECK-NEXT:    [[TMP2:%.*]] = phi <2 x i8> [ [[TMP1]], [[BB1:%.*]] ], [ poison, [[BB2:%.*]] ]
+; CHECK-NEXT:    [[TMP2:%.*]] = phi <2 x i8> [ [[TMP1]], [[BB1:%.*]] ], [ undef, [[BB2:%.*]] ]
 ; CHECK-NEXT:    [[TMP3:%.*]] = zext <2 x i8> [[TMP2]] to <2 x i64>
 ; CHECK-NEXT:    [[GEP0:%.*]] = getelementptr i64, i64* [[PTR:%.*]], i64 0
 ; CHECK-NEXT:    [[TMP4:%.*]] = bitcast i64* [[GEP0]] to <2 x i64>*
@@ -50,7 +50,7 @@
 ; CHECK:       bb2:
 ; CHECK-NEXT:    br label [[BB3]]
 ; CHECK:       bb3:
-; CHECK-NEXT:    [[TMP2:%.*]] = phi <2 x i8> [ [[TMP1]], [[BB1:%.*]] ], [ poison, [[BB2:%.*]] ]
+; CHECK-NEXT:    [[TMP2:%.*]] = phi <2 x i8> [ [[TMP1]], [[BB1:%.*]] ], [ undef, [[BB2:%.*]] ]
 ; CHECK-NEXT:    [[TMP3:%.*]] = zext <2 x i8> [[TMP2]] to <2 x i64>
 ; CHECK-NEXT:    [[GEP0:%.*]] = getelementptr i64, i64* [[PTR:%.*]], i64 0
 ; CHECK-NEXT:    [[TMP4:%.*]] = bitcast i64* [[GEP0]] to <2 x i64>*
@@ -85,7 +85,7 @@
 ; CHECK:       bb2:
 ; CHECK-NEXT:    br label [[BB3]]
 ; CHECK:       bb3:
-; CHECK-NEXT:    [[TMP2:%.*]] = phi <2 x i8> [ [[TMP1]], [[BB1:%.*]] ], [ poison, [[BB2:%.*]] ]
+; CHECK-NEXT:    [[TMP2:%.*]] = phi <2 x i8> [ [[TMP1]], [[BB1:%.*]] ], [ undef, [[BB2:%.*]] ]
 ; CHECK-NEXT:    [[TMP3:%.*]] = zext <2 x i8> [[TMP2]] to <2 x i64>
 ; CHECK-NEXT:    [[GEP0:%.*]] = getelementptr i64, i64* [[PTR:%.*]], i64 0
 ; CHECK-NEXT:    [[TMP4:%.*]] = bitcast i64* [[GEP0]] to <2 x i64>*
diff --git a/llvm/test/Transforms/SLPVectorizer/X86/reduction-same-vals.ll b/llvm/test/Transforms/SLPVectorizer/X86/reduction-same-vals.ll
--- a/llvm/test/Transforms/SLPVectorizer/X86/reduction-same-vals.ll
+++ b/llvm/test/Transforms/SLPVectorizer/X86/reduction-same-vals.ll
@@ -8,7 +8,7 @@
 ; CHECK:       bb2:
 ; CHECK-NEXT:    br label [[BB3]]
 ; CHECK:       bb3:
-; CHECK-NEXT:    [[TMP0:%.*]] = phi <2 x i32> [ poison, [[BB2:%.*]] ], [ zeroinitializer, [[BB1:%.*]] ]
+; CHECK-NEXT:    [[TMP0:%.*]] = phi <2 x i32> [ undef, [[BB2:%.*]] ], [ zeroinitializer, [[BB1:%.*]] ]
 ; CHECK-NEXT:    [[SHUFFLE:%.*]] = shufflevector <2 x i32> [[TMP0]], <2 x i32> poison, <4 x i32> <i32 0, i32 0, i32 0, i32 1>
 ; CHECK-NEXT:    [[TMP1:%.*]] = shufflevector <2 x i32> [[TMP0]], <2 x i32> poison, <8 x i32> zeroinitializer
 ; CHECK-NEXT:    [[TMP2:%.*]] = call i32 @llvm.vector.reduce.mul.v8i32(<8 x i32> [[TMP1]])
diff --git a/llvm/test/Transforms/SLPVectorizer/X86/unreachable.ll b/llvm/test/Transforms/SLPVectorizer/X86/unreachable.ll
--- a/llvm/test/Transforms/SLPVectorizer/X86/unreachable.ll
+++ b/llvm/test/Transforms/SLPVectorizer/X86/unreachable.ll
@@ -15,7 +15,7 @@
 ; CHECK-NEXT:    [[BAD:%.*]] = fadd float [[BAD]], 0.000000e+00
 ; CHECK-NEXT:    br label [[BB2]]
 ; CHECK:       bb2:
-; CHECK-NEXT:    [[TMP0:%.*]] = phi <4 x i32> [ poison, [[BB1:%.*]] ], [ <i32 2, i32 2, i32 2, i32 2>, [[ENTRY:%.*]] ]
+; CHECK-NEXT:    [[TMP0:%.*]] = phi <4 x i32> [ undef, [[BB1:%.*]] ], [ <i32 2, i32 2, i32 2, i32 2>, [[ENTRY:%.*]] ]
 ; CHECK-NEXT:    [[TMP1:%.*]] = bitcast i32* [[X:%.*]] to <4 x i32>*
 ; CHECK-NEXT:    store <4 x i32> [[TMP0]], <4 x i32>* [[TMP1]], align 4
 ; CHECK-NEXT:    ret void