diff --git a/lib/Transforms/InstCombine/InstCombineCalls.cpp b/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 2ab07eb42a2..9f9bf4094c5 100644
--- a/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -515,9 +515,9 @@ static Value *simplifyX86muldq(const IntrinsicInst &II) {
   Value *Arg1 = II.getArgOperand(1);
   Type *ResTy = II.getType();
 
-  // muldq/muludq(undef, undef) -> undef
+  // muldq/muludq(undef, undef) -> zero (matches generic mul behavior)
   if (isa<UndefValue>(Arg0) && isa<UndefValue>(Arg1))
-    return UndefValue::get(ResTy);
+    return ConstantAggregateZero::get(ResTy);
 
   return nullptr;
 }
diff --git a/test/Transforms/InstCombine/x86-muldq.ll b/test/Transforms/InstCombine/x86-muldq.ll
index 28c9d021630..70d4ab22d2d 100644
--- a/test/Transforms/InstCombine/x86-muldq.ll
+++ b/test/Transforms/InstCombine/x86-muldq.ll
@@ -7,7 +7,7 @@
 
 define <2 x i64> @undef_pmuludq_128(<4 x i32> %a0, <4 x i32> %a1) {
 ; CHECK-LABEL: @undef_pmuludq_128(
-; CHECK-NEXT:    ret <2 x i64> undef
+; CHECK-NEXT:    ret <2 x i64> zeroinitializer
 ;
   %1 = call <2 x i64> @llvm.x86.sse2.pmulu.dq(<4 x i32> undef, <4 x i32> undef)
   ret <2 x i64> %1
@@ -15,7 +15,7 @@ define <2 x i64> @undef_pmuludq_128(<4 x i32> %a0, <4 x i32> %a1) {
 
 define <4 x i64> @undef_pmuludq_256(<8 x i32> %a0, <8 x i32> %a1) {
 ; CHECK-LABEL: @undef_pmuludq_256(
-; CHECK-NEXT:    ret <4 x i64> undef
+; CHECK-NEXT:    ret <4 x i64> zeroinitializer
 ;
   %1 = call <4 x i64> @llvm.x86.avx2.pmulu.dq(<8 x i32> undef, <8 x i32> undef)
   ret <4 x i64> %1
@@ -23,7 +23,7 @@ define <4 x i64> @undef_pmuludq_256(<8 x i32> %a0, <8 x i32> %a1) {
 
 define <8 x i64> @undef_pmuludq_512(<16 x i32> %a0, <16 x i32> %a1) {
 ; CHECK-LABEL: @undef_pmuludq_512(
-; CHECK-NEXT:    ret <8 x i64> undef
+; CHECK-NEXT:    ret <8 x i64> zeroinitializer
 ;
   %1 = call <8 x i64> @llvm.x86.avx512.pmulu.dq.512(<16 x i32> undef, <16 x i32> undef)
   ret <8 x i64> %1
@@ -31,7 +31,7 @@ define <8 x i64> @undef_pmuludq_512(<16 x i32> %a0, <16 x i32> %a1) {
 
 define <2 x i64> @undef_pmuldq_128(<4 x i32> %a0, <4 x i32> %a1) {
 ; CHECK-LABEL: @undef_pmuldq_128(
-; CHECK-NEXT:    ret <2 x i64> undef
+; CHECK-NEXT:    ret <2 x i64> zeroinitializer
 ;
   %1 = call <2 x i64> @llvm.x86.sse41.pmuldq(<4 x i32> undef, <4 x i32> undef)
   ret <2 x i64> %1
@@ -39,7 +39,7 @@ define <2 x i64> @undef_pmuldq_128(<4 x i32> %a0, <4 x i32> %a1) {
 
 define <4 x i64> @undef_pmuldq_256(<8 x i32> %a0, <8 x i32> %a1) {
 ; CHECK-LABEL: @undef_pmuldq_256(
-; CHECK-NEXT:    ret <4 x i64> undef
+; CHECK-NEXT:    ret <4 x i64> zeroinitializer
 ;
   %1 = call <4 x i64> @llvm.x86.avx2.pmul.dq(<8 x i32> undef, <8 x i32> undef)
   ret <4 x i64> %1
@@ -47,7 +47,7 @@ define <4 x i64> @undef_pmuldq_256(<8 x i32> %a0, <8 x i32> %a1) {
 
 define <8 x i64> @undef_pmuldq_512(<16 x i32> %a0, <16 x i32> %a1) {
 ; CHECK-LABEL: @undef_pmuldq_512(
-; CHECK-NEXT:    ret <8 x i64> undef
+; CHECK-NEXT:    ret <8 x i64> zeroinitializer
 ;
   %1 = call <8 x i64> @llvm.x86.avx512.pmul.dq.512(<16 x i32> undef, <16 x i32> undef)
   ret <8 x i64> %1