Add support for the ARM GHC calling convention, this patch was in 3.0,
but somehow managed to be dropped later.

Patch by Karel Gardas.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@161226 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/ARM/ARMISelLowering.cpp b/lib/Target/ARM/ARMISelLowering.cpp
index 9d8b7df..119dc5b 100644
--- a/lib/Target/ARM/ARMISelLowering.cpp
+++ b/lib/Target/ARM/ARMISelLowering.cpp
@@ -1171,6 +1171,8 @@
     return (Return ? RetCC_ARM_AAPCS : CC_ARM_AAPCS);
   case CallingConv::ARM_APCS:
     return (Return ? RetCC_ARM_APCS : CC_ARM_APCS);
+  case CallingConv::GHC:
+    return (Return ? RetCC_ARM_APCS : CC_ARM_APCS_GHC);
   }
 }