Add support for thiscall calling convention.
Patch by Charles Davis and Steven Watanabe!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103902 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/MSIL/MSILWriter.cpp b/lib/Target/MSIL/MSILWriter.cpp
index 332a150..3de173c 100644
--- a/lib/Target/MSIL/MSILWriter.cpp
+++ b/lib/Target/MSIL/MSILWriter.cpp
@@ -278,6 +278,8 @@
     return "modopt([mscorlib]System.Runtime.CompilerServices.CallConvFastcall) ";
   case CallingConv::X86_StdCall:
     return "modopt([mscorlib]System.Runtime.CompilerServices.CallConvStdcall) ";
+  case CallingConv::X86_ThisCall:
+    return "modopt([mscorlib]System.Runtime.CompilerServices.CallConvThiscall) ";
   default:
     errs() << "CallingConvID = " << CallingConvID << '\n';
     llvm_unreachable("Unsupported calling convention");