Index: lib/IR/ConstantFold.cpp
===================================================================
--- lib/IR/ConstantFold.cpp
+++ lib/IR/ConstantFold.cpp
@@ -800,23 +800,30 @@
 Constant *llvm::ConstantFoldInsertElementInstruction(Constant *Val,
                                                      Constant *Elt,
                                                      Constant *Idx) {
+  if (isa<UndefValue>(Idx))
+    return UndefValue::get(Val->getType());
+
   ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx);
   if (!CIdx) return nullptr;
-  const APInt &IdxVal = CIdx->getValue();
-  
+
+  unsigned NumElts = Val->getType()->getVectorNumElements();
+  if (CIdx->uge(NumElts))
+    return UndefValue::get(Val->getType());
+
   SmallVector<Constant*, 16> Result;
-  Type *Ty = IntegerType::get(Val->getContext(), 32);
-  for (unsigned i = 0, e = Val->getType()->getVectorNumElements(); i != e; ++i){
+  Result.reserve(NumElts);
+  auto *Ty = Type::getInt32Ty(Val->getContext());
+  uint64_t IdxVal = CIdx->getZExtValue();
+  for (unsigned i = 0; i != NumElts; ++i) {    
     if (i == IdxVal) {
       Result.push_back(Elt);
       continue;
     }
     
-    Constant *C =
-      ConstantExpr::getExtractElement(Val, ConstantInt::get(Ty, i));
+    Constant *C = ConstantExpr::getExtractElement(Val, ConstantInt::get(Ty, i));
     Result.push_back(C);
   }
-  
+
   return ConstantVector::get(Result);
 }
 
Index: test/Transforms/ConstProp/InsertElement.ll
===================================================================
--- test/Transforms/ConstProp/InsertElement.ll
+++ test/Transforms/ConstProp/InsertElement.ll
@@ -1,12 +1,32 @@
 ; RUN: opt < %s -constprop -S | FileCheck %s
 
+; CHECK-LABEL: @test1
 define i32 @test1() {
   %A = bitcast i32 2139171423 to float
   %B = insertelement <1 x float> undef, float %A, i32 0
   %C = extractelement <1 x float> %B, i32 0
   %D = bitcast float %C to i32
   ret i32 %D
-; CHECK: @test1
 ; CHECK: ret i32 2139171423
 }
 
+; CHECK-LABEL: @insertelement
+define <4 x i64> @insertelement() {
+  %vec1 = insertelement <4 x i64> undef, i64 -1, i32 0
+  %vec2 = insertelement <4 x i64> %vec1, i64 -2, i32 1
+  %vec3 = insertelement <4 x i64> %vec2, i64 -3, i32 2
+  %vec4 = insertelement <4 x i64> %vec3, i64 -4, i32 3
+  ; CHECK: ret <4 x i64> <i64 -1, i64 -2, i64 -3, i64 -4>
+  ret <4 x i64> %vec4
+}
+
+; CHECK-LABEL: @insertelement_undef
+define <4 x i64> @insertelement_undef() {
+  %vec1 = insertelement <4 x i64> undef, i64 -1, i32 0
+  %vec2 = insertelement <4 x i64> %vec1, i64 -2, i32 1
+  %vec3 = insertelement <4 x i64> %vec2, i64 -3, i32 2
+  %vec4 = insertelement <4 x i64> %vec3, i64 -4, i32 3
+  %vec5 = insertelement <4 x i64> %vec3, i64 -5, i32 4
+  ; CHECK: ret <4 x i64> undef
+  ret <4 x i64> %vec5
+}
Index: unittests/IR/ConstantsTest.cpp
===================================================================
--- unittests/IR/ConstantsTest.cpp
+++ unittests/IR/ConstantsTest.cpp
@@ -190,7 +190,10 @@
   Constant *Two = ConstantInt::get(Int64Ty, 2);
   Constant *Big = ConstantInt::get(getGlobalContext(),
                                    APInt{256, uint64_t(-1), true});
-  Constant *Undef = UndefValue::get(Int64Ty);
+  Constant *Elt = ConstantInt::get(Int16Ty, 2015);
+  Constant *Undef16  = UndefValue::get(Int16Ty);
+  Constant *Undef64  = UndefValue::get(Int64Ty);
+  Constant *UndefV16 = UndefValue::get(P6->getType());
 
   #define P0STR "ptrtoint (i32** @dummy to i32)"
   #define P1STR "uitofp (i32 ptrtoint (i32** @dummy to i32) to float)"
@@ -260,9 +263,15 @@
   CHECK(ConstantExpr::getExtractElement(P6, One), "extractelement <2 x i16> "
         P6STR ", i32 1");
 
-  EXPECT_TRUE(isa<UndefValue>(ConstantExpr::getExtractElement(P6, Two)));
-  EXPECT_TRUE(isa<UndefValue>(ConstantExpr::getExtractElement(P6, Big)));
-  EXPECT_TRUE(isa<UndefValue>(ConstantExpr::getExtractElement(P6, Undef)));
+  EXPECT_EQ(Undef16, ConstantExpr::getExtractElement(P6, Two));
+  EXPECT_EQ(Undef16, ConstantExpr::getExtractElement(P6, Big));
+  EXPECT_EQ(Undef16, ConstantExpr::getExtractElement(P6, Undef64));
+
+  EXPECT_EQ(Elt, ConstantExpr::getExtractElement(
+                 ConstantExpr::getInsertElement(P6, Elt, One), One));
+  EXPECT_EQ(UndefV16, ConstantExpr::getInsertElement(P6, Elt, Two));
+  EXPECT_EQ(UndefV16, ConstantExpr::getInsertElement(P6, Elt, Big));
+  EXPECT_EQ(UndefV16, ConstantExpr::getInsertElement(P6, Elt, Undef64));
 }
 
 #ifdef GTEST_HAS_DEATH_TEST