[CodeView] Initial support for emitting S_THUNK32 symbols for compiler...

When emitting CodeView debug information, compiler-generated thunk routines
should be emitted using S_THUNK32 symbols instead of S_GPROC32_ID symbols so
Visual Studio can properly step into the user code.  This initial support only
handles standard thunk ordinals.

Differential Revision: https://reviews.llvm.org/D43838

llvm-svn: 330132
diff --git a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h
index e58c4c6..e16c035 100644
--- a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h
+++ b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h
@@ -251,6 +251,10 @@
 
   void emitInlineeLinesSubsection();
 
+  void emitDebugInfoForThunk(const Function *GV,
+                             FunctionInfo &FI,
+                             const MCSymbol *Fn);
+
   void emitDebugInfoForFunction(const Function *GV, FunctionInfo &FI);
 
   void emitDebugInfoForGlobals();