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/ARM/ARMISelLowering.cpp b/lib/Target/ARM/ARMISelLowering.cpp
index 1e90d42..574d4ec 100644
--- a/lib/Target/ARM/ARMISelLowering.cpp
+++ b/lib/Target/ARM/ARMISelLowering.cpp
@@ -7376,12 +7376,16 @@
 /// LowerAsmOperandForConstraint - Lower the specified operand into the Ops
 /// vector.  If it is invalid, don't add anything to Ops.
 void ARMTargetLowering::LowerAsmOperandForConstraint(SDValue Op,
-                                                     char Constraint,
+                                                     std::string &Constraint,
                                                      std::vector<SDValue>&Ops,
                                                      SelectionDAG &DAG) const {
   SDValue Result(0, 0);
 
-  switch (Constraint) {
+  // Currently only support length 1 constraints.
+  if (Constraint.length() != 1) return;
+  
+  char ConstraintLetter = Constraint[0];
+  switch (ConstraintLetter) {
   default: break;
   case 'I': case 'J': case 'K': case 'L':
   case 'M': case 'N': case 'O':
@@ -7396,7 +7400,7 @@
     if (CVal != CVal64)
       return;
 
-    switch (Constraint) {
+    switch (ConstraintLetter) {
       case 'I':
         if (Subtarget->isThumb1Only()) {
           // This must be a constant between 0 and 255, for ADD