Index: lib/Transforms/InstCombine/InstCombineCasts.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -1107,12 +1107,14 @@
   Value *Src = CI.getOperand(0);
   Type *SrcTy = Src->getType(), *DestTy = CI.getType();
 
-  // Attempt to extend the entire input expression tree to the destination
-  // type.   Only do this if the dest type is a simple type, don't convert the
+  // Attempt to extend the entire input expression tree to the wide destination
+  // type. Only do this if the dest type is a simple type. Do not convert the
   // expression tree to something weird like i93 unless the source is also
-  // strange.
+  // strange. Do not attempt this with vectors because it might create
+  // unsupported operations that the backend can not narrow back to the original
+  // type.
   unsigned BitsToClear;
-  if ((DestTy->isVectorTy() || shouldChangeType(SrcTy, DestTy)) &&
+  if (!DestTy->isVectorTy() && shouldChangeType(SrcTy, DestTy) &&
       canEvaluateZExtd(Src, DestTy, BitsToClear, *this, &CI)) {
     assert(BitsToClear <= SrcTy->getScalarSizeInBits() &&
            "Can't clear more bits than in SrcTy");
@@ -1389,11 +1391,13 @@
     return replaceInstUsesWith(CI, ZExt);
   }
 
-  // Attempt to extend the entire input expression tree to the destination
-  // type.   Only do this if the dest type is a simple type, don't convert the
+  // Attempt to extend the entire input expression tree to the wide destination
+  // type. Only do this if the dest type is a simple type. Do not convert the
   // expression tree to something weird like i93 unless the source is also
-  // strange.
-  if ((DestTy->isVectorTy() || shouldChangeType(SrcTy, DestTy)) &&
+  // strange. Do not attempt this with vectors because it might create
+  // unsupported operations that the backend can not narrow back to the original
+  // type.
+  if (!DestTy->isVectorTy() && shouldChangeType(SrcTy, DestTy) &&
       canEvaluateSExtd(Src, DestTy)) {
     // Okay, we can transform this!  Insert the new expression now.
     LLVM_DEBUG(
Index: test/Transforms/InstCombine/cast.ll
===================================================================
--- test/Transforms/InstCombine/cast.ll
+++ test/Transforms/InstCombine/cast.ll
@@ -592,9 +592,11 @@
 
 define <2 x i64> @test46vec(<2 x i64> %A) {
 ; CHECK-LABEL: @test46vec(
-; CHECK-NEXT:    [[C:%.*]] = shl <2 x i64> [[A:%.*]], <i64 8, i64 8>
-; CHECK-NEXT:    [[D:%.*]] = and <2 x i64> [[C]], <i64 10752, i64 10752>
-; CHECK-NEXT:    ret <2 x i64> [[D]]
+; CHECK-NEXT:    [[B:%.*]] = trunc <2 x i64> [[A:%.*]] to <2 x i32>
+; CHECK-NEXT:    [[C:%.*]] = shl <2 x i32> [[B]], <i32 8, i32 8>
+; CHECK-NEXT:    [[D:%.*]] = and <2 x i32> [[C]], <i32 10752, i32 10752>
+; CHECK-NEXT:    [[E:%.*]] = zext <2 x i32> [[D]] to <2 x i64>
+; CHECK-NEXT:    ret <2 x i64> [[E]]
 ;
   %B = trunc <2 x i64> %A to <2 x i32>
   %C = and <2 x i32> %B, <i32 42, i32 42>
@@ -749,9 +751,9 @@
 
 define <2 x i64> @test56vec(<2 x i16> %A) {
 ; CHECK-LABEL: @test56vec(
-; CHECK-NEXT:    [[P353:%.*]] = sext <2 x i16> [[A:%.*]] to <2 x i64>
-; CHECK-NEXT:    [[P354:%.*]] = lshr <2 x i64> [[P353]], <i64 5, i64 5>
-; CHECK-NEXT:    [[P355:%.*]] = and <2 x i64> [[P354]], <i64 134217727, i64 134217727>
+; CHECK-NEXT:    [[P353:%.*]] = sext <2 x i16> [[A:%.*]] to <2 x i32>
+; CHECK-NEXT:    [[P354:%.*]] = lshr <2 x i32> [[P353]], <i32 5, i32 5>
+; CHECK-NEXT:    [[P355:%.*]] = zext <2 x i32> [[P354]] to <2 x i64>
 ; CHECK-NEXT:    ret <2 x i64> [[P355]]
 ;
   %p353 = sext <2 x i16> %A to <2 x i32>
@@ -774,8 +776,9 @@
 
 define <2 x i64> @test57vec(<2 x i64> %A) {
 ; CHECK-LABEL: @test57vec(
-; CHECK-NEXT:    [[C:%.*]] = lshr <2 x i64> [[A:%.*]], <i64 8, i64 8>
-; CHECK-NEXT:    [[E:%.*]] = and <2 x i64> [[C]], <i64 16777215, i64 16777215>
+; CHECK-NEXT:    [[B:%.*]] = trunc <2 x i64> [[A:%.*]] to <2 x i32>
+; CHECK-NEXT:    [[C:%.*]] = lshr <2 x i32> [[B]], <i32 8, i32 8>
+; CHECK-NEXT:    [[E:%.*]] = zext <2 x i32> [[C]] to <2 x i64>
 ; CHECK-NEXT:    ret <2 x i64> [[E]]
 ;
   %B = trunc <2 x i64> %A to <2 x i32>
Index: test/Transforms/InstCombine/select-bitext.ll
===================================================================
--- test/Transforms/InstCombine/select-bitext.ll
+++ test/Transforms/InstCombine/select-bitext.ll
@@ -98,9 +98,8 @@
 
 define <2 x i64> @trunc_sel_larger_sext_vec(<2 x i32> %a, <2 x i1> %cmp) {
 ; CHECK-LABEL: @trunc_sel_larger_sext_vec(
-; CHECK-NEXT:    [[TRUNC:%.*]] = zext <2 x i32> [[A:%.*]] to <2 x i64>
-; CHECK-NEXT:    [[SEXT:%.*]] = shl <2 x i64> [[TRUNC]], <i64 48, i64 48>
-; CHECK-NEXT:    [[TMP1:%.*]] = ashr exact <2 x i64> [[SEXT]], <i64 48, i64 48>
+; CHECK-NEXT:    [[TRUNC:%.*]] = trunc <2 x i32> [[A:%.*]] to <2 x i16>
+; CHECK-NEXT:    [[TMP1:%.*]] = sext <2 x i16> [[TRUNC]] to <2 x i64>
 ; CHECK-NEXT:    [[EXT:%.*]] = select <2 x i1> [[CMP:%.*]], <2 x i64> [[TMP1]], <2 x i64> <i64 42, i64 43>
 ; CHECK-NEXT:    ret <2 x i64> [[EXT]]
 ;
@@ -125,9 +124,8 @@
 
 define <2 x i32> @trunc_sel_smaller_sext_vec(<2 x i64> %a, <2 x i1> %cmp) {
 ; CHECK-LABEL: @trunc_sel_smaller_sext_vec(
-; CHECK-NEXT:    [[TRUNC:%.*]] = trunc <2 x i64> [[A:%.*]] to <2 x i32>
-; CHECK-NEXT:    [[SEXT:%.*]] = shl <2 x i32> [[TRUNC]], <i32 16, i32 16>
-; CHECK-NEXT:    [[TMP1:%.*]] = ashr exact <2 x i32> [[SEXT]], <i32 16, i32 16>
+; CHECK-NEXT:    [[TRUNC:%.*]] = trunc <2 x i64> [[A:%.*]] to <2 x i16>
+; CHECK-NEXT:    [[TMP1:%.*]] = sext <2 x i16> [[TRUNC]] to <2 x i32>
 ; CHECK-NEXT:    [[EXT:%.*]] = select <2 x i1> [[CMP:%.*]], <2 x i32> [[TMP1]], <2 x i32> <i32 42, i32 43>
 ; CHECK-NEXT:    ret <2 x i32> [[EXT]]
 ;
@@ -152,9 +150,9 @@
 
 define <2 x i32> @trunc_sel_equal_sext_vec(<2 x i32> %a, <2 x i1> %cmp) {
 ; CHECK-LABEL: @trunc_sel_equal_sext_vec(
-; CHECK-NEXT:    [[SEXT:%.*]] = shl <2 x i32> [[A:%.*]], <i32 16, i32 16>
-; CHECK-NEXT:    [[TMP1:%.*]] = ashr exact <2 x i32> [[SEXT]], <i32 16, i32 16>
-; CHECK-NEXT:    [[EXT:%.*]] = select <2 x i1> [[CMP:%.*]], <2 x i32> [[TMP1]], <2 x i32> <i32 42, i32 43>
+; CHECK-NEXT:    [[TMP1:%.*]] = shl <2 x i32> [[A:%.*]], <i32 16, i32 16>
+; CHECK-NEXT:    [[TMP2:%.*]] = ashr exact <2 x i32> [[TMP1]], <i32 16, i32 16>
+; CHECK-NEXT:    [[EXT:%.*]] = select <2 x i1> [[CMP:%.*]], <2 x i32> [[TMP2]], <2 x i32> <i32 42, i32 43>
 ; CHECK-NEXT:    ret <2 x i32> [[EXT]]
 ;
   %trunc = trunc <2 x i32> %a to <2 x i16>
@@ -178,9 +176,9 @@
 
 define <2 x i64> @trunc_sel_larger_zext_vec(<2 x i32> %a, <2 x i1> %cmp) {
 ; CHECK-LABEL: @trunc_sel_larger_zext_vec(
-; CHECK-NEXT:    [[TMP1:%.*]] = and <2 x i32> [[A:%.*]], <i32 65535, i32 65535>
-; CHECK-NEXT:    [[TMP2:%.*]] = zext <2 x i32> [[TMP1]] to <2 x i64>
-; CHECK-NEXT:    [[EXT:%.*]] = select <2 x i1> [[CMP:%.*]], <2 x i64> [[TMP2]], <2 x i64> <i64 42, i64 43>
+; CHECK-NEXT:    [[TRUNC_MASK:%.*]] = and <2 x i32> [[A:%.*]], <i32 65535, i32 65535>
+; CHECK-NEXT:    [[TMP1:%.*]] = zext <2 x i32> [[TRUNC_MASK]] to <2 x i64>
+; CHECK-NEXT:    [[EXT:%.*]] = select <2 x i1> [[CMP:%.*]], <2 x i64> [[TMP1]], <2 x i64> <i64 42, i64 43>
 ; CHECK-NEXT:    ret <2 x i64> [[EXT]]
 ;
   %trunc = trunc <2 x i32> %a to <2 x i16>
@@ -204,9 +202,9 @@
 
 define <2 x i32> @trunc_sel_smaller_zext_vec(<2 x i64> %a, <2 x i1> %cmp) {
 ; CHECK-LABEL: @trunc_sel_smaller_zext_vec(
-; CHECK-NEXT:    [[TRUNC:%.*]] = trunc <2 x i64> [[A:%.*]] to <2 x i32>
-; CHECK-NEXT:    [[TMP1:%.*]] = and <2 x i32> [[TRUNC]], <i32 65535, i32 65535>
-; CHECK-NEXT:    [[EXT:%.*]] = select <2 x i1> [[CMP:%.*]], <2 x i32> [[TMP1]], <2 x i32> <i32 42, i32 43>
+; CHECK-NEXT:    [[TMP1:%.*]] = trunc <2 x i64> [[A:%.*]] to <2 x i32>
+; CHECK-NEXT:    [[TMP2:%.*]] = and <2 x i32> [[TMP1]], <i32 65535, i32 65535>
+; CHECK-NEXT:    [[EXT:%.*]] = select <2 x i1> [[CMP:%.*]], <2 x i32> [[TMP2]], <2 x i32> <i32 42, i32 43>
 ; CHECK-NEXT:    ret <2 x i32> [[EXT]]
 ;
   %trunc = trunc <2 x i64> %a to <2 x i16>
Index: test/Transforms/InstCombine/vector-casts.ll
===================================================================
--- test/Transforms/InstCombine/vector-casts.ll
+++ test/Transforms/InstCombine/vector-casts.ll
@@ -163,8 +163,8 @@
 
 define <2 x i65> @foo(<2 x i64> %t) {
 ; CHECK-LABEL: @foo(
-; CHECK-NEXT:    [[TMP1:%.*]] = and <2 x i64> [[T:%.*]], <i64 4294967295, i64 4294967295>
-; CHECK-NEXT:    [[B:%.*]] = zext <2 x i64> [[TMP1]] to <2 x i65>
+; CHECK-NEXT:    [[A_MASK:%.*]] = and <2 x i64> [[T:%.*]], <i64 4294967295, i64 4294967295>
+; CHECK-NEXT:    [[B:%.*]] = zext <2 x i64> [[A_MASK]] to <2 x i65>
 ; CHECK-NEXT:    ret <2 x i65> [[B]]
 ;
   %a = trunc <2 x i64> %t to <2 x i32>
@@ -174,8 +174,8 @@
 
 define <2 x i64> @bar(<2 x i65> %t) {
 ; CHECK-LABEL: @bar(
-; CHECK-NEXT:    [[A:%.*]] = trunc <2 x i65> [[T:%.*]] to <2 x i64>
-; CHECK-NEXT:    [[B:%.*]] = and <2 x i64> [[A]], <i64 4294967295, i64 4294967295>
+; CHECK-NEXT:    [[TMP1:%.*]] = trunc <2 x i65> [[T:%.*]] to <2 x i64>
+; CHECK-NEXT:    [[B:%.*]] = and <2 x i64> [[TMP1]], <i64 4294967295, i64 4294967295>
 ; CHECK-NEXT:    ret <2 x i64> [[B]]
 ;
   %a = trunc <2 x i65> %t to <2 x i32>
@@ -185,9 +185,8 @@
 
 define <2 x i64> @bars(<2 x i65> %t) {
 ; CHECK-LABEL: @bars(
-; CHECK-NEXT:    [[A:%.*]] = trunc <2 x i65> [[T:%.*]] to <2 x i64>
-; CHECK-NEXT:    [[SEXT:%.*]] = shl <2 x i64> [[A]], <i64 32, i64 32>
-; CHECK-NEXT:    [[B:%.*]] = ashr exact <2 x i64> [[SEXT]], <i64 32, i64 32>
+; CHECK-NEXT:    [[A:%.*]] = trunc <2 x i65> [[T:%.*]] to <2 x i32>
+; CHECK-NEXT:    [[B:%.*]] = sext <2 x i32> [[A]] to <2 x i64>
 ; CHECK-NEXT:    ret <2 x i64> [[B]]
 ;
   %a = trunc <2 x i65> %t to <2 x i32>
@@ -197,8 +196,8 @@
 
 define <2 x i64> @quxs(<2 x i64> %t) {
 ; CHECK-LABEL: @quxs(
-; CHECK-NEXT:    [[SEXT:%.*]] = shl <2 x i64> [[T:%.*]], <i64 32, i64 32>
-; CHECK-NEXT:    [[B:%.*]] = ashr exact <2 x i64> [[SEXT]], <i64 32, i64 32>
+; CHECK-NEXT:    [[TMP1:%.*]] = shl <2 x i64> [[T:%.*]], <i64 32, i64 32>
+; CHECK-NEXT:    [[B:%.*]] = ashr exact <2 x i64> [[TMP1]], <i64 32, i64 32>
 ; CHECK-NEXT:    ret <2 x i64> [[B]]
 ;
   %a = trunc <2 x i64> %t to <2 x i32>
@@ -384,9 +383,10 @@
 
 define <2 x i64> @sext_less_casting_with_wideop(<2 x i64> %x, <2 x i64> %y) {
 ; CHECK-LABEL: @sext_less_casting_with_wideop(
-; CHECK-NEXT:    [[MUL:%.*]] = mul <2 x i64> [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT:    [[SEXT:%.*]] = shl <2 x i64> [[MUL]], <i64 32, i64 32>
-; CHECK-NEXT:    [[R:%.*]] = ashr exact <2 x i64> [[SEXT]], <i64 32, i64 32>
+; CHECK-NEXT:    [[XNARROW:%.*]] = trunc <2 x i64> [[X:%.*]] to <2 x i32>
+; CHECK-NEXT:    [[YNARROW:%.*]] = trunc <2 x i64> [[Y:%.*]] to <2 x i32>
+; CHECK-NEXT:    [[MUL:%.*]] = mul <2 x i32> [[XNARROW]], [[YNARROW]]
+; CHECK-NEXT:    [[R:%.*]] = sext <2 x i32> [[MUL]] to <2 x i64>
 ; CHECK-NEXT:    ret <2 x i64> [[R]]
 ;
   %xnarrow = trunc <2 x i64> %x to <2 x i32>
@@ -398,8 +398,10 @@
 
 define <2 x i64> @zext_less_casting_with_wideop(<2 x i64> %x, <2 x i64> %y) {
 ; CHECK-LABEL: @zext_less_casting_with_wideop(
-; CHECK-NEXT:    [[MUL:%.*]] = mul <2 x i64> [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT:    [[R:%.*]] = and <2 x i64> [[MUL]], <i64 4294967295, i64 4294967295>
+; CHECK-NEXT:    [[XNARROW:%.*]] = trunc <2 x i64> [[X:%.*]] to <2 x i32>
+; CHECK-NEXT:    [[YNARROW:%.*]] = trunc <2 x i64> [[Y:%.*]] to <2 x i32>
+; CHECK-NEXT:    [[MUL:%.*]] = mul <2 x i32> [[XNARROW]], [[YNARROW]]
+; CHECK-NEXT:    [[R:%.*]] = zext <2 x i32> [[MUL]] to <2 x i64>
 ; CHECK-NEXT:    ret <2 x i64> [[R]]
 ;
   %xnarrow = trunc <2 x i64> %x to <2 x i32>