[clang] [CIR] Upstream support for C++ member function calls (PR #140290)

[Erich Keane via cfe-commits]

================
@@ -0,0 +1,45 @@
+//===----- CirGenCXXABI.cpp - Interface to C++ ABIs -----------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This provides an abstract class for C++ code generation. Concrete subclasses
+// of this implement code generation for specific C++ ABIs.
+//
+//===----------------------------------------------------------------------===//
+
+#include "CIRGenCXXABI.h"
+#include "CIRGenFunction.h"
+
+#include "clang/AST/Decl.h"
+#include "clang/AST/GlobalDecl.h"
+
+using namespace clang;
+using namespace clang::CIRGen;
+
+CIRGenCXXABI::~CIRGenCXXABI() {}
+
+void CIRGenCXXABI::buildThisParam(CIRGenFunction &cgf,
+                                  FunctionArgList &params) {
+  const auto *md = cast<CXXMethodDecl>(cgf.curGD.getDecl());
+
+  // FIXME: I'm not entirely sure I like using a fake decl just for code
----------------
erichkeane wrote:

Ah, shoot :D  Welp!  IMO CIR should probably model 'member function' some day, but if this is that old/preexisting, we can just live with it.

I'm generally happy with this patch, but hoping the ot hers can do a more thorough review.

https://github.com/llvm/llvm-project/pull/140290