Support __builtin_ms_va_list.

Summary:
This change adds support for `__builtin_ms_va_list`, a GCC extension for
variadic `ms_abi` functions. The existing `__builtin_va_list` support is
inadequate for this because `va_list` is defined differently in the Win64
ABI vs. the System V/AMD64 ABI.

Depends on D1622.

Reviewers: rsmith, rnk, rjmccall

CC: cfe-commits

Differential Revision: http://reviews.llvm.org/D1623

llvm-svn: 247941

clang/lib/CodeGen/CodeGenFunction.cpp

@@ -1718,6 +1718,10 @@ Address CodeGenFunction::EmitVAListRef(const Expr* E) {
   return EmitLValue(E).getAddress();
 }
 
+Address CodeGenFunction::EmitMSVAListRef(const Expr *E) {
+  return EmitLValue(E).getAddress();
+}
+
 void CodeGenFunction::EmitDeclRefExprDbgValue(const DeclRefExpr *E,
                                               llvm::Constant *Init) {
   assert (Init && "Invalid DeclRefExpr initializer!");