Index: llvm/trunk/lib/Analysis/ConstantFolding.cpp
===================================================================
--- llvm/trunk/lib/Analysis/ConstantFolding.cpp
+++ llvm/trunk/lib/Analysis/ConstantFolding.cpp
@@ -224,8 +224,19 @@
 
   // Loop over each source value, expanding into multiple results.
   for (unsigned i = 0; i != NumSrcElt; ++i) {
-    auto *Src = dyn_cast_or_null<ConstantInt>(C->getAggregateElement(i));
-    if (!Src)  // Reject constantexpr elements.
+    auto *Element = C->getAggregateElement(i);
+
+    if (!Element) // Reject constantexpr elements.
+      return ConstantExpr::getBitCast(C, DestTy);
+
+    if (isa<UndefValue>(Element)) {
+      // Correctly Propagate undef values.
+      Result.append(Ratio, UndefValue::get(DstEltTy));
+      continue;
+    }
+
+    auto *Src = dyn_cast<ConstantInt>(Element);
+    if (!Src)
       return ConstantExpr::getBitCast(C, DestTy);
 
     unsigned ShiftAmt = isLittleEndian ? 0 : DstBitSize*(Ratio-1);
Index: llvm/trunk/test/Transforms/InstCombine/x86-sse4a.ll
===================================================================
--- llvm/trunk/test/Transforms/InstCombine/x86-sse4a.ll
+++ llvm/trunk/test/Transforms/InstCombine/x86-sse4a.ll
@@ -57,8 +57,7 @@
 
 define <2 x i64> @test_extrq_call_constexpr(<2 x i64> %x) {
 ; CHECK-LABEL: @test_extrq_call_constexpr(
-; CHECK-NEXT:    [[TMP1:%.*]] = call <2 x i64> @llvm.x86.sse4a.extrq(<2 x i64> %x, <16 x i8> bitcast (<2 x i64> <i64 0, i64 undef> to <16 x i8>))
-; CHECK-NEXT:    ret <2 x i64> [[TMP1]]
+; CHECK-NEXT:    ret <2 x i64> %x
 ;
   %1 = call <2 x i64> @llvm.x86.sse4a.extrq(<2 x i64> %x, <16 x i8> bitcast (<2 x i64> <i64 0, i64 undef> to <16 x i8>))
   ret <2 x i64> %1
@@ -133,7 +132,7 @@
 
 define <2 x i64> @test_extrqi_call_constexpr() {
 ; CHECK-LABEL: @test_extrqi_call_constexpr(
-; CHECK-NEXT:    ret <2 x i64> bitcast (<16 x i8> <i8 extractelement (<16 x i8> trunc (<16 x i16> bitcast (<4 x i64> <i64 0, i64 undef, i64 2, i64 undef> to <16 x i16>) to <16 x i8>), i32 2), i8 0, i8 0, i8 0, i8 0, i8 0, i8 0, i8 0, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef> to <2 x i64>)
+; CHECK-NEXT:    ret <2 x i64> zeroinitializer
 ;
   %1 = tail call <2 x i64> @llvm.x86.sse4a.extrqi(<2 x i64> bitcast (<16 x i8> trunc (<16 x i16> bitcast (<4 x i64> <i64 0, i64 undef, i64 2, i64 undef> to <16 x i16>) to <16 x i8>) to <2 x i64>), i8 8, i8 16)
   ret <2 x i64> %1
@@ -179,7 +178,7 @@
 
 define <2 x i64> @test_insertq_call_constexpr(<2 x i64> %x) {
 ; CHECK-LABEL: @test_insertq_call_constexpr(
-; CHECK-NEXT:    [[TMP1:%.*]] = tail call <2 x i64> @llvm.x86.sse4a.insertq(<2 x i64> %x, <2 x i64> bitcast (<16 x i8> trunc (<16 x i16> bitcast (<4 x i64> <i64 0, i64 undef, i64 2, i64 undef> to <16 x i16>) to <16 x i8>) to <2 x i64>))
+; CHECK-NEXT:    [[TMP1:%.*]] = call <2 x i64> @llvm.x86.sse4a.insertqi(<2 x i64> %x, <2 x i64> <i64 0, i64 undef>, i8 2, i8 0)
 ; CHECK-NEXT:    ret <2 x i64> [[TMP1]]
 ;
   %1 = tail call <2 x i64> @llvm.x86.sse4a.insertq(<2 x i64> %x, <2 x i64> bitcast (<16 x i8> trunc (<16 x i16> bitcast (<4 x i64> <i64 0, i64 undef, i64 2, i64 undef> to <16 x i16>) to <16 x i8>) to <2 x i64>))
@@ -224,7 +223,7 @@
 
 define <2 x i64> @test_insertqi_call_constexpr(<2 x i64> %x) {
 ; CHECK-LABEL: @test_insertqi_call_constexpr(
-; CHECK-NEXT:    [[TMP1:%.*]] = tail call <2 x i64> @llvm.x86.sse4a.insertqi(<2 x i64> %x, <2 x i64> bitcast (<16 x i8> trunc (<16 x i16> bitcast (<4 x i64> <i64 0, i64 undef, i64 2, i64 undef> to <16 x i16>) to <16 x i8>) to <2 x i64>), i8 48, i8 3)
+; CHECK-NEXT:    [[TMP1:%.*]] = tail call <2 x i64> @llvm.x86.sse4a.insertqi(<2 x i64> %x, <2 x i64> <i64 0, i64 undef>, i8 48, i8 3)
 ; CHECK-NEXT:    ret <2 x i64> [[TMP1]]
 ;
   %1 = tail call <2 x i64> @llvm.x86.sse4a.insertqi(<2 x i64> %x, <2 x i64> bitcast (<16 x i8> trunc (<16 x i16> bitcast (<4 x i64> <i64 0, i64 undef, i64 2, i64 undef> to <16 x i16>) to <16 x i8>) to <2 x i64>), i8 48, i8 3)
Index: llvm/trunk/test/Transforms/InstSimplify/bitcast-vector-fold.ll
===================================================================
--- llvm/trunk/test/Transforms/InstSimplify/bitcast-vector-fold.ll
+++ llvm/trunk/test/Transforms/InstSimplify/bitcast-vector-fold.ll
@@ -126,7 +126,7 @@
 
 define <4 x i32> @bitcast_constexpr_4i32_2i64_u2() {
 ; CHECK-LABEL: @bitcast_constexpr_4i32_2i64_u2(
-; CHECK-NEXT:    ret <4 x i32> bitcast (<2 x i64> <i64 undef, i64 2> to <4 x i32>)
+; CHECK-NEXT:    ret <4 x i32> <i32 undef, i32 undef, i32 2, i32 0>
 ;
   %cast = bitcast <2 x i64><i64 undef, i64 2> to <4 x i32>
   ret <4 x i32> %cast
@@ -134,7 +134,7 @@
 
 define <4 x i32> @bitcast_constexpr_4i32_2i64_1u() {
 ; CHECK-LABEL: @bitcast_constexpr_4i32_2i64_1u(
-; CHECK-NEXT:    ret <4 x i32> bitcast (<2 x i64> <i64 1, i64 undef> to <4 x i32>)
+; CHECK-NEXT:    ret <4 x i32> <i32 1, i32 0, i32 undef, i32 undef>
 ;
   %cast = bitcast <2 x i64><i64 1, i64 undef> to <4 x i32>
   ret <4 x i32> %cast
@@ -142,7 +142,7 @@
 
 define <4 x i32> @bitcast_constexpr_4i32_2i64() {
 ; CHECK-LABEL: @bitcast_constexpr_4i32_2i64(
-; CHECK-NEXT:    ret <4 x i32> bitcast (<2 x i64> <i64 undef, i64 2> to <4 x i32>)
+; CHECK-NEXT:    ret <4 x i32> <i32 undef, i32 undef, i32 2, i32 0>
 ;
   %cast = bitcast <2 x i64><i64 undef, i64 2> to <4 x i32>
   ret <4 x i32> %cast
@@ -150,7 +150,7 @@
 
 define <8 x i16> @bitcast_constexpr_8i16_2i64_u2() {
 ; CHECK-LABEL: @bitcast_constexpr_8i16_2i64_u2(
-; CHECK-NEXT:    ret <8 x i16> bitcast (<2 x i64> <i64 undef, i64 2> to <8 x i16>)
+; CHECK-NEXT:    ret <8 x i16> <i16 undef, i16 undef, i16 undef, i16 undef, i16 2, i16 0, i16 0, i16 0>
 ;
   %cast = bitcast <2 x i64><i64 undef, i64 2> to <8 x i16>
   ret <8 x i16> %cast
@@ -158,7 +158,7 @@
 
 define <8 x i16> @bitcast_constexpr_8i16_2i64_1u() {
 ; CHECK-LABEL: @bitcast_constexpr_8i16_2i64_1u(
-; CHECK-NEXT:    ret <8 x i16> bitcast (<2 x i64> <i64 1, i64 undef> to <8 x i16>)
+; CHECK-NEXT:    ret <8 x i16> <i16 1, i16 0, i16 0, i16 0, i16 undef, i16 undef, i16 undef, i16 undef>
 ;
   %cast = bitcast <2 x i64><i64 1, i64 undef> to <8 x i16>
   ret <8 x i16> %cast
@@ -166,7 +166,7 @@
 
 define <8 x i16> @bitcast_constexpr_8i16_2i64_u65536() {
 ; CHECK-LABEL: @bitcast_constexpr_8i16_2i64_u65536(
-; CHECK-NEXT:    ret <8 x i16> bitcast (<2 x i64> <i64 undef, i64 65536> to <8 x i16>)
+; CHECK-NEXT:    ret <8 x i16> <i16 undef, i16 undef, i16 undef, i16 undef, i16 0, i16 1, i16 0, i16 0>
 ;
   %cast = bitcast <2 x i64><i64 undef, i64 65536> to <8 x i16>
   ret <8 x i16> %cast
@@ -174,7 +174,7 @@
 
 define <16 x i8> @bitcast_constexpr_16i8_2i64_u2() {
 ; CHECK-LABEL: @bitcast_constexpr_16i8_2i64_u2(
-; CHECK-NEXT:    ret <16 x i8> bitcast (<2 x i64> <i64 undef, i64 2> to <16 x i8>)
+; CHECK-NEXT:    ret <16 x i8> <i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 2, i8 0, i8 0, i8 0, i8 0, i8 0, i8 0, i8 0>
 ;
   %cast = bitcast <2 x i64><i64 undef, i64 2> to <16 x i8>
   ret <16 x i8> %cast
@@ -182,7 +182,7 @@
 
 define <16 x i8> @bitcast_constexpr_16i8_2i64_256u() {
 ; CHECK-LABEL: @bitcast_constexpr_16i8_2i64_256u(
-; CHECK-NEXT:    ret <16 x i8> bitcast (<2 x i64> <i64 256, i64 undef> to <16 x i8>)
+; CHECK-NEXT:    ret <16 x i8> <i8 0, i8 1, i8 0, i8 0, i8 0, i8 0, i8 0, i8 0, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef>
 ;
   %cast = bitcast <2 x i64><i64 256, i64 undef> to <16 x i8>
   ret <16 x i8> %cast
@@ -190,7 +190,7 @@
 
 define <16 x i8> @bitcast_constexpr_16i8_2i64_u256() {
 ; CHECK-LABEL: @bitcast_constexpr_16i8_2i64_u256(
-; CHECK-NEXT:    ret <16 x i8> bitcast (<2 x i64> <i64 undef, i64 256> to <16 x i8>)
+; CHECK-NEXT:    ret <16 x i8> <i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 0, i8 1, i8 0, i8 0, i8 0, i8 0, i8 0, i8 0>
 ;
   %cast = bitcast <2 x i64><i64 undef, i64 256> to <16 x i8>
   ret <16 x i8> %cast
@@ -198,7 +198,7 @@
 
 define <8 x i16> @bitcast_constexpr_8i16_4i32_uu22() {
 ; CHECK-LABEL: @bitcast_constexpr_8i16_4i32_uu22(
-; CHECK-NEXT:    ret <8 x i16> bitcast (<4 x i32> <i32 undef, i32 undef, i32 2, i32 2> to <8 x i16>)
+; CHECK-NEXT:    ret <8 x i16> <i16 undef, i16 undef, i16 undef, i16 undef, i16 2, i16 0, i16 2, i16 0>
 ;
   %cast = bitcast <4 x i32><i32 undef, i32 undef, i32 2, i32 2> to <8 x i16>
   ret <8 x i16> %cast
@@ -206,7 +206,7 @@
 
 define <8 x i16> @bitcast_constexpr_8i16_4i32_10uu() {
 ; CHECK-LABEL: @bitcast_constexpr_8i16_4i32_10uu(
-; CHECK-NEXT:    ret <8 x i16> bitcast (<4 x i32> <i32 1, i32 0, i32 undef, i32 undef> to <8 x i16>)
+; CHECK-NEXT:    ret <8 x i16> <i16 1, i16 0, i16 0, i16 0, i16 undef, i16 undef, i16 undef, i16 undef>
 ;
   %cast = bitcast <4 x i32><i32 1, i32 0, i32 undef, i32 undef> to <8 x i16>
   ret <8 x i16> %cast
@@ -214,7 +214,7 @@
 
 define <8 x i16> @bitcast_constexpr_8i16_4i32_u257u256() {
 ; CHECK-LABEL: @bitcast_constexpr_8i16_4i32_u257u256(
-; CHECK-NEXT:    ret <8 x i16> bitcast (<4 x i32> <i32 undef, i32 65536, i32 undef, i32 65536> to <8 x i16>)
+; CHECK-NEXT:    ret <8 x i16> <i16 undef, i16 undef, i16 0, i16 1, i16 undef, i16 undef, i16 0, i16 1>
 ;
   %cast = bitcast <4 x i32><i32 undef, i32 65536, i32 undef, i32 65536> to <8 x i16>
   ret <8 x i16> %cast
@@ -222,7 +222,7 @@
 
 define <16 x i8> @bitcast_constexpr_16i8_4i32_u2u2() {
 ; CHECK-LABEL: @bitcast_constexpr_16i8_4i32_u2u2(
-; CHECK-NEXT:    ret <16 x i8> bitcast (<4 x i32> <i32 undef, i32 2, i32 undef, i32 2> to <16 x i8>)
+; CHECK-NEXT:    ret <16 x i8> <i8 undef, i8 undef, i8 undef, i8 undef, i8 2, i8 0, i8 0, i8 0, i8 undef, i8 undef, i8 undef, i8 undef, i8 2, i8 0, i8 0, i8 0>
 ;
   %cast = bitcast <4 x i32><i32 undef, i32 2, i32 undef, i32 2> to <16 x i8>
   ret <16 x i8> %cast
@@ -230,7 +230,7 @@
 
 define <16 x i8> @bitcast_constexpr_16i8_4i32_1u1u() {
 ; CHECK-LABEL: @bitcast_constexpr_16i8_4i32_1u1u(
-; CHECK-NEXT:    ret <16 x i8> bitcast (<4 x i32> <i32 1, i32 undef, i32 1, i32 undef> to <16 x i8>)
+; CHECK-NEXT:    ret <16 x i8> <i8 1, i8 0, i8 0, i8 0, i8 undef, i8 undef, i8 undef, i8 undef, i8 1, i8 0, i8 0, i8 0, i8 undef, i8 undef, i8 undef, i8 undef>
 ;
   %cast = bitcast <4 x i32><i32 1, i32 undef, i32 1, i32 undef> to <16 x i8>
   ret <16 x i8> %cast
@@ -238,7 +238,7 @@
 
 define <16 x i8> @bitcast_constexpr_16i8_4i32_u256uu() {
 ; CHECK-LABEL: @bitcast_constexpr_16i8_4i32_u256uu(
-; CHECK-NEXT:    ret <16 x i8> bitcast (<4 x i32> <i32 undef, i32 256, i32 undef, i32 undef> to <16 x i8>)
+; CHECK-NEXT:    ret <16 x i8> <i8 undef, i8 undef, i8 undef, i8 undef, i8 0, i8 1, i8 0, i8 0, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef>
 ;
   %cast = bitcast <4 x i32><i32 undef, i32 256, i32 undef, i32 undef> to <16 x i8>
   ret <16 x i8> %cast
@@ -246,7 +246,7 @@
 
 define <16 x i8> @bitcast_constexpr_16i8_8i16_u2u2u2u2() {
 ; CHECK-LABEL: @bitcast_constexpr_16i8_8i16_u2u2u2u2(
-; CHECK-NEXT:    ret <16 x i8> bitcast (<8 x i16> <i16 undef, i16 2, i16 undef, i16 2, i16 undef, i16 2, i16 undef, i16 2> to <16 x i8>)
+; CHECK-NEXT:    ret <16 x i8> <i8 undef, i8 undef, i8 2, i8 0, i8 undef, i8 undef, i8 2, i8 0, i8 undef, i8 undef, i8 2, i8 0, i8 undef, i8 undef, i8 2, i8 0>
 ;
   %cast = bitcast <8 x i16><i16 undef, i16 2, i16 undef, i16 2, i16 undef, i16 2, i16 undef, i16 2> to <16 x i8>
   ret <16 x i8> %cast
@@ -254,7 +254,7 @@
 
 define <16 x i8> @bitcast_constexpr_16i8_8i16_1u1u1u1u() {
 ; CHECK-LABEL: @bitcast_constexpr_16i8_8i16_1u1u1u1u(
-; CHECK-NEXT:    ret <16 x i8> bitcast (<8 x i16> <i16 1, i16 undef, i16 1, i16 undef, i16 1, i16 undef, i16 1, i16 undef> to <16 x i8>)
+; CHECK-NEXT:    ret <16 x i8> <i8 1, i8 0, i8 undef, i8 undef, i8 1, i8 0, i8 undef, i8 undef, i8 1, i8 0, i8 undef, i8 undef, i8 1, i8 0, i8 undef, i8 undef>
 ;
   %cast = bitcast <8 x i16><i16 1, i16 undef, i16 1, i16 undef, i16 1, i16 undef, i16 1, i16 undef> to <16 x i8>
   ret <16 x i8> %cast
@@ -262,7 +262,7 @@
 
 define <16 x i8> @bitcast_constexpr_16i8_8i16_u256uuu256uu() {
 ; CHECK-LABEL: @bitcast_constexpr_16i8_8i16_u256uuu256uu(
-; CHECK-NEXT:    ret <16 x i8> bitcast (<8 x i16> <i16 undef, i16 256, i16 undef, i16 undef, i16 undef, i16 256, i16 undef, i16 undef> to <16 x i8>)
+; CHECK-NEXT:    ret <16 x i8> <i8 undef, i8 undef, i8 0, i8 1, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 0, i8 1, i8 undef, i8 undef, i8 undef, i8 undef>
 ;
   %cast = bitcast <8 x i16><i16 undef, i16 256, i16 undef, i16 undef, i16 undef, i16 256, i16 undef, i16 undef> to <16 x i8>
   ret <16 x i8> %cast