Add support for the 'x' constraint.

Part of rdar://9307836 and rdar://9119939


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134215 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/ARM/ARMISelLowering.cpp b/lib/Target/ARM/ARMISelLowering.cpp
index 7828447..22cd78f 100644
--- a/lib/Target/ARM/ARMISelLowering.cpp
+++ b/lib/Target/ARM/ARMISelLowering.cpp
@@ -7483,6 +7483,7 @@
     case 'l': return C_RegisterClass;
     case 'w': return C_RegisterClass;
     case 'h': return C_RegisterClass;
+    case 'x': return C_RegisterClass;
     }
   } else if (Constraint.size() == 2) {
     switch (Constraint[0]) {
@@ -7555,6 +7556,14 @@
       if (VT.getSizeInBits() == 128)
         return RCPair(0U, ARM::QPRRegisterClass);
       break;
+    case 'x':
+      if (VT == MVT::f32)
+	return RCPair(0U, ARM::SPR_8RegisterClass);
+      if (VT.getSizeInBits() == 64)
+	return RCPair(0U, ARM::DPR_8RegisterClass);
+      if (VT.getSizeInBits() == 128)
+	return RCPair(0U, ARM::QPR_8RegisterClass);
+      break;
     }
   }
   if (StringRef("{cc}").equals_lower(Constraint))