Index: lib/CodeGen/CGExprScalar.cpp
===================================================================
--- lib/CodeGen/CGExprScalar.cpp
+++ lib/CodeGen/CGExprScalar.cpp
@@ -1166,6 +1166,16 @@
   return llvm::ConstantInt::get(I32Ty, Off+MV);
 }
 
+static llvm::Constant *getAsInt32(llvm::ConstantInt *C, llvm::Type *I32Ty) {
+  if (C->getBitWidth() != 32) {
+      assert(llvm::ConstantInt::isValueValidForType(I32Ty,
+                                                    C->getZExtValue()) &&
+             "Index operand too large for shufflevector mask!");
+      return llvm::ConstantInt::get(I32Ty, C->getZExtValue());
+  }
+  return C;
+}
+
 Value *ScalarExprEmitter::VisitInitListExpr(InitListExpr *E) {
   bool Ignore = TestAndClearIgnoreResultAssign();
   (void)Ignore;
@@ -1216,7 +1226,8 @@
           Value *LHS = nullptr, *RHS = nullptr;
           if (CurIdx == 0) {
             // insert into undef -> shuffle (src, undef)
-            Args.push_back(C);
+            // shufflemask must use an i32
+            Args.push_back(getAsInt32(C, CGF.Int32Ty));
             Args.resize(ResElts, llvm::UndefValue::get(CGF.Int32Ty));
 
             LHS = EI->getVectorOperand();