Have LowerOperandForConstraint handle multiple character constraints.

Part of rdar://9119939


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@132510 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 7820509..a39e453 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -12594,12 +12594,16 @@
 /// LowerAsmOperandForConstraint - Lower the specified operand into the Ops
 /// vector.  If it is invalid, don't add anything to Ops.
 void X86TargetLowering::LowerAsmOperandForConstraint(SDValue Op,
-                                                     char Constraint,
+                                                     std::string &Constraint,
                                                      std::vector<SDValue>&Ops,
                                                      SelectionDAG &DAG) const {
   SDValue Result(0, 0);
 
-  switch (Constraint) {
+  // Only support length 1 constraints for now.
+  if (Constraint.length() > 1) return;
+  
+  char ConstraintLetter = Constraint[0];
+  switch (ConstraintLetter) {
   default: break;
   case 'I':
     if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Op)) {