diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 4abac988c2e43..f38dc436722dc 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -3364,6 +3364,23 @@ static Value *foldICmpWithLowBitMaskedVal(ICmpInst &I,
     llvm_unreachable("All possible folds are handled.");
   }
 
+  // The mask value may be a vector constant that has undefined elements. But it
+  // may not be safe to propagate those undefs into the new compare, so replace
+  // those elements by copying an existing, defined, and safe scalar constant.
+  Type *OpTy = M->getType();
+  auto *VecC = dyn_cast<Constant>(M);
+  if (OpTy->isVectorTy() && VecC && VecC->containsUndefElement()) {
+    Constant *SafeReplacementConstant = nullptr;
+    for (unsigned i = 0, e = OpTy->getVectorNumElements(); i != e; ++i) {
+      if (!isa<UndefValue>(VecC->getAggregateElement(i))) {
+        SafeReplacementConstant = VecC->getAggregateElement(i);
+        break;
+      }
+    }
+    assert(SafeReplacementConstant && "Failed to find undef replacement");
+    M = Constant::replaceUndefsWith(VecC, SafeReplacementConstant);
+  }
+
   return Builder.CreateICmp(DstPred, X, M);
 }
 
diff --git a/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-ne-to-icmp-ugt.ll b/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-ne-to-icmp-ugt.ll
index f1f2528fe3d20..49f76fd9f407f 100644
--- a/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-ne-to-icmp-ugt.ll
+++ b/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-ne-to-icmp-ugt.ll
@@ -82,7 +82,7 @@ define <2 x i1> @p2_vec_nonsplat_edgecase1(<2 x i8> %x) {
 
 define <3 x i1> @p3_vec_splat_undef(<3 x i8> %x) {
 ; CHECK-LABEL: @p3_vec_splat_undef(
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp ugt <3 x i8> [[X:%.*]], <i8 3, i8 undef, i8 3>
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp ugt <3 x i8> [[X:%.*]], <i8 3, i8 3, i8 3>
 ; CHECK-NEXT:    ret <3 x i1> [[TMP1]]
 ;
   %tmp0 = and <3 x i8> %x, <i8 3, i8 undef, i8 3>
@@ -92,7 +92,7 @@ define <3 x i1> @p3_vec_splat_undef(<3 x i8> %x) {
 
 define <3 x i1> @p3_vec_nonsplat_undef(<3 x i8> %x) {
 ; CHECK-LABEL: @p3_vec_nonsplat_undef(
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp ugt <3 x i8> [[X:%.*]], <i8 -1, i8 undef, i8 3>
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp ugt <3 x i8> [[X:%.*]], <i8 -1, i8 -1, i8 3>
 ; CHECK-NEXT:    ret <3 x i1> [[TMP1]]
 ;
   %tmp0 = and <3 x i8> %x, <i8 -1, i8 undef, i8 3>
diff --git a/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-sgt-to-icmp-sgt.ll b/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-sgt-to-icmp-sgt.ll
index d3ef5e54f010a..16d063ee05524 100644
--- a/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-sgt-to-icmp-sgt.ll
+++ b/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-sgt-to-icmp-sgt.ll
@@ -76,7 +76,7 @@ define <2 x i1> @p2_vec_nonsplat_edgecase() {
 define <3 x i1> @p3_vec_splat_undef() {
 ; CHECK-LABEL: @p3_vec_splat_undef(
 ; CHECK-NEXT:    [[X:%.*]] = call <3 x i8> @gen3x8()
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp sgt <3 x i8> [[X]], <i8 3, i8 undef, i8 3>
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp sgt <3 x i8> [[X]], <i8 3, i8 3, i8 3>
 ; CHECK-NEXT:    ret <3 x i1> [[TMP1]]
 ;
   %x = call <3 x i8> @gen3x8()
@@ -88,7 +88,7 @@ define <3 x i1> @p3_vec_splat_undef() {
 define <3 x i1> @p3_vec_nonsplat_undef() {
 ; CHECK-LABEL: @p3_vec_nonsplat_undef(
 ; CHECK-NEXT:    [[X:%.*]] = call <3 x i8> @gen3x8()
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp sgt <3 x i8> [[X]], <i8 15, i8 3, i8 undef>
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp sgt <3 x i8> [[X]], <i8 15, i8 3, i8 15>
 ; CHECK-NEXT:    ret <3 x i1> [[TMP1]]
 ;
   %x = call <3 x i8> @gen3x8()
diff --git a/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-slt-to-icmp-sgt.ll b/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-slt-to-icmp-sgt.ll
index 6366fed23c3fd..b71172b426345 100644
--- a/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-slt-to-icmp-sgt.ll
+++ b/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-slt-to-icmp-sgt.ll
@@ -61,7 +61,7 @@ define <2 x i1> @p2_vec_nonsplat_edgecase(<2 x i8> %x) {
 
 define <3 x i1> @p3_vec_splat_undef(<3 x i8> %x) {
 ; CHECK-LABEL: @p3_vec_splat_undef(
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp sgt <3 x i8> [[X:%.*]], <i8 3, i8 undef, i8 3>
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp sgt <3 x i8> [[X:%.*]], <i8 3, i8 3, i8 3>
 ; CHECK-NEXT:    ret <3 x i1> [[TMP1]]
 ;
   %tmp0 = and <3 x i8> %x, <i8 3, i8 undef, i8 3>
@@ -71,7 +71,7 @@ define <3 x i1> @p3_vec_splat_undef(<3 x i8> %x) {
 
 define <3 x i1> @p3_vec_nonsplat_undef(<3 x i8> %x) {
 ; CHECK-LABEL: @p3_vec_nonsplat_undef(
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp sgt <3 x i8> [[X:%.*]], <i8 undef, i8 15, i8 3>
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp sgt <3 x i8> [[X:%.*]], <i8 15, i8 15, i8 3>
 ; CHECK-NEXT:    ret <3 x i1> [[TMP1]]
 ;
   %tmp0 = and <3 x i8> %x, <i8 undef, i8 15, i8 3>
diff --git a/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-ugt-to-icmp-ugt.ll b/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-ugt-to-icmp-ugt.ll
index 9e0008611b588..9b1d405935d0f 100644
--- a/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-ugt-to-icmp-ugt.ll
+++ b/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-ugt-to-icmp-ugt.ll
@@ -99,7 +99,7 @@ define <2 x i1> @p2_vec_nonsplat_edgecase1() {
 define <3 x i1> @p3_vec_splat_undef() {
 ; CHECK-LABEL: @p3_vec_splat_undef(
 ; CHECK-NEXT:    [[X:%.*]] = call <3 x i8> @gen3x8()
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp ugt <3 x i8> [[X]], <i8 3, i8 undef, i8 3>
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp ugt <3 x i8> [[X]], <i8 3, i8 3, i8 3>
 ; CHECK-NEXT:    ret <3 x i1> [[TMP1]]
 ;
   %x = call <3 x i8> @gen3x8()
@@ -111,7 +111,7 @@ define <3 x i1> @p3_vec_splat_undef() {
 define <3 x i1> @p3_vec_nonsplat_undef() {
 ; CHECK-LABEL: @p3_vec_nonsplat_undef(
 ; CHECK-NEXT:    [[X:%.*]] = call <3 x i8> @gen3x8()
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp ugt <3 x i8> [[X]], <i8 3, i8 undef, i8 15>
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp ugt <3 x i8> [[X]], <i8 3, i8 3, i8 15>
 ; CHECK-NEXT:    ret <3 x i1> [[TMP1]]
 ;
   %x = call <3 x i8> @gen3x8()
diff --git a/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-ult-to-icmp-ugt.ll b/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-ult-to-icmp-ugt.ll
index f6a85d4860ee3..728f9e0ddf8ab 100644
--- a/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-ult-to-icmp-ugt.ll
+++ b/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-ult-to-icmp-ugt.ll
@@ -83,7 +83,7 @@ define <2 x i1> @p2_vec_nonsplat_edgecase1(<2 x i8> %x) {
 
 define <3 x i1> @p3_vec_splat_undef(<3 x i8> %x) {
 ; CHECK-LABEL: @p3_vec_splat_undef(
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp ugt <3 x i8> [[X:%.*]], <i8 3, i8 undef, i8 3>
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp ugt <3 x i8> [[X:%.*]], <i8 3, i8 3, i8 3>
 ; CHECK-NEXT:    ret <3 x i1> [[TMP1]]
 ;
   %tmp0 = and <3 x i8> %x, <i8 3, i8 undef, i8 3>
@@ -93,7 +93,7 @@ define <3 x i1> @p3_vec_splat_undef(<3 x i8> %x) {
 
 define <3 x i1> @p3_vec_nonsplat_undef(<3 x i8> %x) {
 ; CHECK-LABEL: @p3_vec_nonsplat_undef(
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp ugt <3 x i8> [[X:%.*]], <i8 7, i8 31, i8 undef>
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp ugt <3 x i8> [[X:%.*]], <i8 7, i8 31, i8 7>
 ; CHECK-NEXT:    ret <3 x i1> [[TMP1]]
 ;
   %tmp0 = and <3 x i8> %x, <i8 7, i8 31, i8 undef>