Index: lib/Transforms/InstCombine/InstCombineCalls.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -736,7 +736,8 @@
   return Builder.CreateInsertElement(Dst, Res, (uint64_t)0);
 }
 
-static Value *simplifyX86movmsk(const IntrinsicInst &II) {
+static Value *simplifyX86movmsk(const IntrinsicInst &II,
+                                InstCombiner::BuilderTy &Builder) {
   Value *Arg = II.getArgOperand(0);
   Type *ResTy = II.getType();
   Type *ArgTy = Arg->getType();
@@ -749,29 +750,46 @@
   if (!ArgTy->isVectorTy())
     return nullptr;
 
-  auto *C = dyn_cast<Constant>(Arg);
-  if (!C)
-    return nullptr;
+  if (auto *C = dyn_cast<Constant>(Arg)) {
+    // Extract signbits of the vector input and pack into integer result.
+    APInt Result(ResTy->getPrimitiveSizeInBits(), 0);
+    for (unsigned I = 0, E = ArgTy->getVectorNumElements(); I != E; ++I) {
+      auto *COp = C->getAggregateElement(I);
+      if (!COp)
+        return nullptr;
+      if (isa<UndefValue>(COp))
+        continue;
 
-  // Extract signbits of the vector input and pack into integer result.
-  APInt Result(ResTy->getPrimitiveSizeInBits(), 0);
-  for (unsigned I = 0, E = ArgTy->getVectorNumElements(); I != E; ++I) {
-    auto *COp = C->getAggregateElement(I);
-    if (!COp)
-      return nullptr;
-    if (isa<UndefValue>(COp))
-      continue;
+      auto *CInt = dyn_cast<ConstantInt>(COp);
+      auto *CFp = dyn_cast<ConstantFP>(COp);
+      if (!CInt && !CFp)
+        return nullptr;
 
-    auto *CInt = dyn_cast<ConstantInt>(COp);
-    auto *CFp = dyn_cast<ConstantFP>(COp);
-    if (!CInt && !CFp)
-      return nullptr;
+      if ((CInt && CInt->isNegative()) || (CFp && CFp->isNegative()))
+        Result.setBit(I);
+    }
+    return Constant::getIntegerValue(ResTy, Result);
+  }
 
-    if ((CInt && CInt->isNegative()) || (CFp && CFp->isNegative()))
-      Result.setBit(I);
+  // If the argument is bitcast, look through that, but make sure the source of
+  // that bitcast is still a vector with the same number of elements.
+  // TODO: We can also convert a bitcast with wider elements, but that requires
+  // duplicating the bool source sign bits to match the number of elements
+  // expected by the movmsk call.
+  Arg = peekThroughBitcast(Arg);
+  Value *BoolSrc;
+  if (Arg->getType()->isVectorTy() &&
+      Arg->getType()->getVectorNumElements() == ArgTy->getVectorNumElements() &&
+      match(Arg, m_SExt(m_Value(BoolSrc))) &&
+      BoolSrc->getType()->getScalarSizeInBits() == 1) {
+    // call iM movmsk(sext <N x i1> X) --> zext (bitcast <N x i1> X to iN) to iM
+    unsigned NumElts = BoolSrc->getType()->getVectorNumElements();
+    Type *ScalarTy = Type::getIntNTy(Arg->getContext(), NumElts);
+    Value *BC = Builder.CreateBitCast(BoolSrc, ScalarTy);
+    return Builder.CreateZExtOrTrunc(BC, ResTy);
   }
 
-  return Constant::getIntegerValue(ResTy, Result);
+  return nullptr;
 }
 
 static Value *simplifyX86insertps(const IntrinsicInst &II,
@@ -2543,7 +2561,7 @@
   case Intrinsic::x86_avx_movmsk_pd_256:
   case Intrinsic::x86_avx_movmsk_ps_256:
   case Intrinsic::x86_avx2_pmovmskb:
-    if (Value *V = simplifyX86movmsk(*II))
+    if (Value *V = simplifyX86movmsk(*II, Builder))
       return replaceInstUsesWith(*II, V);
     break;
 
Index: test/Transforms/InstCombine/X86/x86-movmsk.ll
===================================================================
--- test/Transforms/InstCombine/X86/x86-movmsk.ll
+++ test/Transforms/InstCombine/X86/x86-movmsk.ll
@@ -315,10 +315,9 @@
 
 define i32 @sext_sse_movmsk_ps(<4 x i1> %x) {
 ; CHECK-LABEL: @sext_sse_movmsk_ps(
-; CHECK-NEXT:    [[SEXT:%.*]] = sext <4 x i1> [[X:%.*]] to <4 x i32>
-; CHECK-NEXT:    [[BC:%.*]] = bitcast <4 x i32> [[SEXT]] to <4 x float>
-; CHECK-NEXT:    [[R:%.*]] = call i32 @llvm.x86.sse.movmsk.ps(<4 x float> [[BC]])
-; CHECK-NEXT:    ret i32 [[R]]
+; CHECK-NEXT:    [[TMP1:%.*]] = bitcast <4 x i1> [[X:%.*]] to i4
+; CHECK-NEXT:    [[TMP2:%.*]] = zext i4 [[TMP1]] to i32
+; CHECK-NEXT:    ret i32 [[TMP2]]
 ;
   %sext = sext <4 x i1> %x to <4 x i32>
   %bc = bitcast <4 x i32> %sext to <4 x float>
@@ -328,10 +327,9 @@
 
 define i32 @sext_sse2_movmsk_pd(<2 x i1> %x) {
 ; CHECK-LABEL: @sext_sse2_movmsk_pd(
-; CHECK-NEXT:    [[SEXT:%.*]] = sext <2 x i1> [[X:%.*]] to <2 x i64>
-; CHECK-NEXT:    [[BC:%.*]] = bitcast <2 x i64> [[SEXT]] to <2 x double>
-; CHECK-NEXT:    [[R:%.*]] = call i32 @llvm.x86.sse2.movmsk.pd(<2 x double> [[BC]])
-; CHECK-NEXT:    ret i32 [[R]]
+; CHECK-NEXT:    [[TMP1:%.*]] = bitcast <2 x i1> [[X:%.*]] to i2
+; CHECK-NEXT:    [[TMP2:%.*]] = zext i2 [[TMP1]] to i32
+; CHECK-NEXT:    ret i32 [[TMP2]]
 ;
   %sext = sext <2 x i1> %x to <2 x i64>
   %bc = bitcast <2 x i64> %sext to <2 x double>
@@ -341,9 +339,9 @@
 
 define i32 @sext_sse2_pmovmskb_128(<16 x i1> %x) {
 ; CHECK-LABEL: @sext_sse2_pmovmskb_128(
-; CHECK-NEXT:    [[SEXT:%.*]] = sext <16 x i1> [[X:%.*]] to <16 x i8>
-; CHECK-NEXT:    [[R:%.*]] = call i32 @llvm.x86.sse2.pmovmskb.128(<16 x i8> [[SEXT]])
-; CHECK-NEXT:    ret i32 [[R]]
+; CHECK-NEXT:    [[TMP1:%.*]] = bitcast <16 x i1> [[X:%.*]] to i16
+; CHECK-NEXT:    [[TMP2:%.*]] = zext i16 [[TMP1]] to i32
+; CHECK-NEXT:    ret i32 [[TMP2]]
 ;
   %sext = sext <16 x i1> %x to <16 x i8>
   %r = call i32 @llvm.x86.sse2.pmovmskb.128(<16 x i8> %sext)
@@ -352,10 +350,9 @@
 
 define i32 @sext_avx_movmsk_ps_256(<8 x i1> %x) {
 ; CHECK-LABEL: @sext_avx_movmsk_ps_256(
-; CHECK-NEXT:    [[SEXT:%.*]] = sext <8 x i1> [[X:%.*]] to <8 x i32>
-; CHECK-NEXT:    [[BC:%.*]] = bitcast <8 x i32> [[SEXT]] to <8 x float>
-; CHECK-NEXT:    [[R:%.*]] = call i32 @llvm.x86.avx.movmsk.ps.256(<8 x float> [[BC]])
-; CHECK-NEXT:    ret i32 [[R]]
+; CHECK-NEXT:    [[TMP1:%.*]] = bitcast <8 x i1> [[X:%.*]] to i8
+; CHECK-NEXT:    [[TMP2:%.*]] = zext i8 [[TMP1]] to i32
+; CHECK-NEXT:    ret i32 [[TMP2]]
 ;
   %sext = sext <8 x i1> %x to <8 x i32>
   %bc = bitcast <8 x i32> %sext to <8 x float>
@@ -365,10 +362,9 @@
 
 define i32 @sext_avx_movmsk_pd_256(<4 x i1> %x) {
 ; CHECK-LABEL: @sext_avx_movmsk_pd_256(
-; CHECK-NEXT:    [[SEXT:%.*]] = sext <4 x i1> [[X:%.*]] to <4 x i64>
-; CHECK-NEXT:    [[BC:%.*]] = bitcast <4 x i64> [[SEXT]] to <4 x double>
-; CHECK-NEXT:    [[R:%.*]] = call i32 @llvm.x86.avx.movmsk.pd.256(<4 x double> [[BC]])
-; CHECK-NEXT:    ret i32 [[R]]
+; CHECK-NEXT:    [[TMP1:%.*]] = bitcast <4 x i1> [[X:%.*]] to i4
+; CHECK-NEXT:    [[TMP2:%.*]] = zext i4 [[TMP1]] to i32
+; CHECK-NEXT:    ret i32 [[TMP2]]
 ;
   %sext = sext <4 x i1> %x to <4 x i64>
   %bc = bitcast <4 x i64> %sext to <4 x double>
@@ -378,15 +374,60 @@
 
 define i32 @sext_avx2_pmovmskb(<32 x i1> %x) {
 ; CHECK-LABEL: @sext_avx2_pmovmskb(
-; CHECK-NEXT:    [[SEXT:%.*]] = sext <32 x i1> [[X:%.*]] to <32 x i8>
-; CHECK-NEXT:    [[R:%.*]] = call i32 @llvm.x86.avx2.pmovmskb(<32 x i8> [[SEXT]])
-; CHECK-NEXT:    ret i32 [[R]]
+; CHECK-NEXT:    [[TMP1:%.*]] = bitcast <32 x i1> [[X:%.*]] to i32
+; CHECK-NEXT:    ret i32 [[TMP1]]
 ;
   %sext = sext <32 x i1> %x to <32 x i8>
   %r = call i32 @llvm.x86.avx2.pmovmskb(<32 x i8> %sext)
   ret i32 %r
 }
 
+; Negative test - bitcast from scalar.
+
+define i32 @sext_sse_movmsk_ps_scalar_source(i1 %x) {
+; CHECK-LABEL: @sext_sse_movmsk_ps_scalar_source(
+; CHECK-NEXT:    [[SEXT:%.*]] = sext i1 [[X:%.*]] to i128
+; CHECK-NEXT:    [[BC:%.*]] = bitcast i128 [[SEXT]] to <4 x float>
+; CHECK-NEXT:    [[R:%.*]] = call i32 @llvm.x86.sse.movmsk.ps(<4 x float> [[BC]])
+; CHECK-NEXT:    ret i32 [[R]]
+;
+  %sext = sext i1 %x to i128
+  %bc = bitcast i128 %sext to <4 x float>
+  %r = call i32 @llvm.x86.sse.movmsk.ps(<4 x float> %bc)
+  ret i32 %r
+}
+
+; Negative test - bitcast from vector type with more elements.
+
+define i32 @sext_sse_movmsk_ps_too_many_elts(<8 x i1> %x) {
+; CHECK-LABEL: @sext_sse_movmsk_ps_too_many_elts(
+; CHECK-NEXT:    [[SEXT:%.*]] = sext <8 x i1> [[X:%.*]] to <8 x i16>
+; CHECK-NEXT:    [[BC:%.*]] = bitcast <8 x i16> [[SEXT]] to <4 x float>
+; CHECK-NEXT:    [[R:%.*]] = call i32 @llvm.x86.sse.movmsk.ps(<4 x float> [[BC]])
+; CHECK-NEXT:    ret i32 [[R]]
+;
+  %sext = sext <8 x i1> %x to <8 x i16>
+  %bc = bitcast <8 x i16> %sext to <4 x float>
+  %r = call i32 @llvm.x86.sse.movmsk.ps(<4 x float> %bc)
+  ret i32 %r
+}
+
+; TODO: We could handle this by doing a bitcasted sign-bit test after the sext?
+; But need to make sure the backend handles that correctly.
+
+define i32 @sext_sse_movmsk_ps_must_replicate_bits(<2 x i1> %x) {
+; CHECK-LABEL: @sext_sse_movmsk_ps_must_replicate_bits(
+; CHECK-NEXT:    [[SEXT:%.*]] = sext <2 x i1> [[X:%.*]] to <2 x i64>
+; CHECK-NEXT:    [[BC:%.*]] = bitcast <2 x i64> [[SEXT]] to <4 x float>
+; CHECK-NEXT:    [[R:%.*]] = call i32 @llvm.x86.sse.movmsk.ps(<4 x float> [[BC]])
+; CHECK-NEXT:    ret i32 [[R]]
+;
+  %sext = sext <2 x i1> %x to <2 x i64>
+  %bc = bitcast <2 x i64> %sext to <4 x float>
+  %r = call i32 @llvm.x86.sse.movmsk.ps(<4 x float> %bc)
+  ret i32 %r
+}
+
 declare i32 @llvm.x86.mmx.pmovmskb(x86_mmx)
 
 declare i32 @llvm.x86.sse.movmsk.ps(<4 x float>)