Add support for the 'h' constraint.

Part of rdar://9119939


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134203 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/ARM/ARMISelLowering.cpp b/lib/Target/ARM/ARMISelLowering.cpp
index 092ff17..1b9bcc9 100644
--- a/lib/Target/ARM/ARMISelLowering.cpp
+++ b/lib/Target/ARM/ARMISelLowering.cpp
@@ -7482,6 +7482,7 @@
     default:  break;
     case 'l': return C_RegisterClass;
     case 'w': return C_RegisterClass;
+    case 'h': return C_RegisterClass;
     }
   } else if (Constraint.size() == 2) {
     switch (Constraint[0]) {
@@ -7534,11 +7535,16 @@
   if (Constraint.size() == 1) {
     // GCC ARM Constraint Letters
     switch (Constraint[0]) {
-    case 'l':
+    case 'l': // Low regs or general regs.
       if (Subtarget->isThumb())
         return Pair(0U, ARM::tGPRRegisterClass);
       else
         return Pair(0U, ARM::GPRRegisterClass);
+    case 'h': // High regs or no regs.
+      if (Subtarget->isThumb())
+	return Pair(0U, ARM::hGPRRegisterClass);
+      else
+	return Pair(0u, static_cast<const TargetRegisterClass*>(0));
     case 'r':
       return Pair(0U, ARM::GPRRegisterClass);
     case 'w':