diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -4385,16 +4385,16 @@
   if (VecC && ValC && IdxC)
     return ConstantExpr::getInsertElement(VecC, ValC, IdxC);
 
-  // For fixed-length vector, fold into undef if index is out of bounds.
+  // For fixed-length vector, fold into poison if index is out of bounds.
   if (auto *CI = dyn_cast<ConstantInt>(Idx)) {
     if (isa<FixedVectorType>(Vec->getType()) &&
         CI->uge(cast<FixedVectorType>(Vec->getType())->getNumElements()))
-      return UndefValue::get(Vec->getType());
+      return PoisonValue::get(Vec->getType());
   }
 
   // If index is undef, it might be out of bounds (see above case)
   if (Q.isUndefValue(Idx))
-    return UndefValue::get(Vec->getType());
+    return PoisonValue::get(Vec->getType());
 
   // If the scalar is undef, and there is no risk of propagating poison from the
   // vector value, simplify to the vector value.
diff --git a/llvm/test/Transforms/InstCombine/out-of-bounds-indexes.ll b/llvm/test/Transforms/InstCombine/out-of-bounds-indexes.ll
--- a/llvm/test/Transforms/InstCombine/out-of-bounds-indexes.ll
+++ b/llvm/test/Transforms/InstCombine/out-of-bounds-indexes.ll
@@ -34,7 +34,7 @@
 
 define <4 x double> @inselt_bad_index(<4 x double> %a) {
 ; CHECK-LABEL: @inselt_bad_index(
-; CHECK-NEXT:    ret <4 x double> undef
+; CHECK-NEXT:    ret <4 x double> poison
 ;
   %I = insertelement <4 x double> %a, double 0.0, i64 4294967296
   ret <4 x double> %I
diff --git a/llvm/test/Transforms/InstCombine/vector_insertelt_shuffle-inseltpoison.ll b/llvm/test/Transforms/InstCombine/vector_insertelt_shuffle-inseltpoison.ll
--- a/llvm/test/Transforms/InstCombine/vector_insertelt_shuffle-inseltpoison.ll
+++ b/llvm/test/Transforms/InstCombine/vector_insertelt_shuffle-inseltpoison.ll
@@ -57,7 +57,7 @@
 ; Out of bounds index folds to undef
 define <4 x float> @bazzz(<4 x float> %x) {
 ; CHECK-LABEL: @bazzz(
-; CHECK-NEXT:    ret <4 x float> <float undef, float undef, float 2.000000e+00, float undef>
+; CHECK-NEXT:    ret <4 x float> <float poison, float poison, float 2.000000e+00, float poison>
 ;
   %ins1 = insertelement<4 x float> %x, float 1.0, i32 5
   %ins2 = insertelement<4 x float> %ins1, float 2.0, i32 2
@@ -66,7 +66,7 @@
 
 define <4 x float> @bazzzz(<4 x float> %x) {
 ; CHECK-LABEL: @bazzzz(
-; CHECK-NEXT:    ret <4 x float> <float undef, float undef, float 2.000000e+00, float undef>
+; CHECK-NEXT:    ret <4 x float> <float poison, float poison, float 2.000000e+00, float poison>
 ;
   %ins1 = insertelement<4 x float> %x, float 1.0, i32 undef
   %ins2 = insertelement<4 x float> %ins1, float 2.0, i32 2
diff --git a/llvm/test/Transforms/InstCombine/vector_insertelt_shuffle.ll b/llvm/test/Transforms/InstCombine/vector_insertelt_shuffle.ll
--- a/llvm/test/Transforms/InstCombine/vector_insertelt_shuffle.ll
+++ b/llvm/test/Transforms/InstCombine/vector_insertelt_shuffle.ll
@@ -57,7 +57,7 @@
 ; Out of bounds index folds to undef
 define <4 x float> @bazzz(<4 x float> %x) {
 ; CHECK-LABEL: @bazzz(
-; CHECK-NEXT:    ret <4 x float> <float undef, float undef, float 2.000000e+00, float undef>
+; CHECK-NEXT:    ret <4 x float> <float poison, float poison, float 2.000000e+00, float poison>
 ;
   %ins1 = insertelement<4 x float> %x, float 1.0, i32 5
   %ins2 = insertelement<4 x float> %ins1, float 2.0, i32 2
@@ -66,7 +66,7 @@
 
 define <4 x float> @bazzzz(<4 x float> %x) {
 ; CHECK-LABEL: @bazzzz(
-; CHECK-NEXT:    ret <4 x float> <float undef, float undef, float 2.000000e+00, float undef>
+; CHECK-NEXT:    ret <4 x float> <float poison, float poison, float 2.000000e+00, float poison>
 ;
   %ins1 = insertelement<4 x float> %x, float 1.0, i32 undef
   %ins2 = insertelement<4 x float> %ins1, float 2.0, i32 2
diff --git a/llvm/test/Transforms/InstSimplify/insertelement.ll b/llvm/test/Transforms/InstSimplify/insertelement.ll
--- a/llvm/test/Transforms/InstSimplify/insertelement.ll
+++ b/llvm/test/Transforms/InstSimplify/insertelement.ll
@@ -3,7 +3,7 @@
 
 define <4 x i32> @test1(<4 x i32> %A) {
 ; CHECK-LABEL: @test1(
-; CHECK-NEXT:    ret <4 x i32> undef
+; CHECK-NEXT:    ret <4 x i32> poison
 ;
   %I = insertelement <4 x i32> %A, i32 5, i64 4294967296
   ret <4 x i32> %I
@@ -11,7 +11,7 @@
 
 define <4 x i32> @test2(<4 x i32> %A) {
 ; CHECK-LABEL: @test2(
-; CHECK-NEXT:    ret <4 x i32> undef
+; CHECK-NEXT:    ret <4 x i32> poison
 ;
   %I = insertelement <4 x i32> %A, i32 5, i64 4
   ret <4 x i32> %I
@@ -28,7 +28,7 @@
 
 define <4 x i32> @test4(<4 x i32> %A) {
 ; CHECK-LABEL: @test4(
-; CHECK-NEXT:    ret <4 x i32> undef
+; CHECK-NEXT:    ret <4 x i32> poison
 ;
   %I = insertelement <4 x i32> %A, i32 5, i128 100
   ret <4 x i32> %I
@@ -36,7 +36,7 @@
 
 define <4 x i32> @test5(<4 x i32> %A) {
 ; CHECK-LABEL: @test5(
-; CHECK-NEXT:    ret <4 x i32> undef
+; CHECK-NEXT:    ret <4 x i32> poison
 ;
   %I = insertelement <4 x i32> %A, i32 5, i64 undef
   ret <4 x i32> %I
@@ -44,7 +44,7 @@
 
 define <4 x i32> @test5_poison(<4 x i32> %A) {
 ; CHECK-LABEL: @test5_poison(
-; CHECK-NEXT:    ret <4 x i32> undef
+; CHECK-NEXT:    ret <4 x i32> poison
 ;
   %I = insertelement <4 x i32> %A, i32 5, i64 poison
   ret <4 x i32> %I
diff --git a/llvm/test/Transforms/InstSimplify/vscale-inseltpoison.ll b/llvm/test/Transforms/InstSimplify/vscale-inseltpoison.ll
--- a/llvm/test/Transforms/InstSimplify/vscale-inseltpoison.ll
+++ b/llvm/test/Transforms/InstSimplify/vscale-inseltpoison.ll
@@ -9,7 +9,7 @@
 
 define <vscale x 4 x i32> @insertelement_idx_undef(<vscale x 4 x i32> %a) {
 ; CHECK-LABEL: @insertelement_idx_undef(
-; CHECK-NEXT:    ret <vscale x 4 x i32> undef
+; CHECK-NEXT:    ret <vscale x 4 x i32> poison
 ;
   %r = insertelement <vscale x 4 x i32> %a, i32 5, i64 undef
   ret <vscale x 4 x i32> %r
diff --git a/llvm/test/Transforms/InstSimplify/vscale.ll b/llvm/test/Transforms/InstSimplify/vscale.ll
--- a/llvm/test/Transforms/InstSimplify/vscale.ll
+++ b/llvm/test/Transforms/InstSimplify/vscale.ll
@@ -9,7 +9,7 @@
 
 define <vscale x 4 x i32> @insertelement_idx_undef(<vscale x 4 x i32> %a) {
 ; CHECK-LABEL: @insertelement_idx_undef(
-; CHECK-NEXT:    ret <vscale x 4 x i32> undef
+; CHECK-NEXT:    ret <vscale x 4 x i32> poison
 ;
   %r = insertelement <vscale x 4 x i32> %a, i32 5, i64 undef
   ret <vscale x 4 x i32> %r
@@ -133,8 +133,9 @@
 define <vscale x 2 x i1> @cmp_le_smax_always_true(<vscale x 2 x i64> %x) {
 ; CHECK-LABEL: @cmp_le_smax_always_true(
 ; CHECK-NEXT:    ret <vscale x 2 x i1> shufflevector (<vscale x 2 x i1> insertelement (<vscale x 2 x i1> undef, i1 true, i32 0), <vscale x 2 x i1> undef, <vscale x 2 x i32> zeroinitializer)
-   %cmp = icmp sle <vscale x 2 x i64> %x, shufflevector (<vscale x 2 x i64> insertelement (<vscale x 2 x i64> undef, i64 9223372036854775807, i32 0), <vscale x 2 x i64> undef, <vscale x 2 x i32> zeroinitializer)
-   ret <vscale x 2 x i1> %cmp
+;
+  %cmp = icmp sle <vscale x 2 x i64> %x, shufflevector (<vscale x 2 x i64> insertelement (<vscale x 2 x i64> undef, i64 9223372036854775807, i32 0), <vscale x 2 x i64> undef, <vscale x 2 x i32> zeroinitializer)
+  ret <vscale x 2 x i1> %cmp
 }
 
 define <vscale x 4 x float> @bitcast() {