[-cxx-abi microsoft] Mangle __uuidof correctly into template parameters

Summary:
It seems that __uuidof introduces a global extern "C" declaration of
type __s_GUID.  However, our implementation of __uuidof does not provide
such a declaration and thus must open-code the mangling for __uuidof in
template parameters.

This allows us to codegen scoped COM pointers and other such things.

This fixes PR16836.
Depends on D1356.

Reviewers: rnk, cdavis5x, rsmith

Reviewed By: rnk

CC: cfe-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D1357

llvm-svn: 188252

clang/lib/CodeGen/CodeGenModule.cpp

@@ -1046,17 +1046,7 @@ llvm::Constant *CodeGenModule::GetAddrOfUuidDescriptor(
     const CXXUuidofExpr* E) {
   // Sema has verified that IIDSource has a __declspec(uuid()), and that its
   // well-formed.
-  StringRef Uuid;
-  if (E->isTypeOperand())
-    Uuid = CXXUuidofExpr::GetUuidAttrOfType(E->getTypeOperand())->getGuid();
-  else {
-    // Special case: __uuidof(0) means an all-zero GUID.
-    Expr *Op = E->getExprOperand();
-    if (!Op->isNullPointerConstant(Context, Expr::NPC_ValueDependentIsNull))
-      Uuid = CXXUuidofExpr::GetUuidAttrOfType(Op->getType())->getGuid();
-    else
-      Uuid = "00000000-0000-0000-0000-000000000000";
-  }
+  StringRef Uuid = E->getUuidAsStringRef(Context);
   std::string Name = "_GUID_" + Uuid.lower();
   std::replace(Name.begin(), Name.end(), '-', '_');