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

[Andy Kaylor via cfe-commits]

================
@@ -76,11 +77,30 @@ static void appendParameterTypes(const CIRGenTypes &cgt,
   cgt.getCGModule().errorNYI("appendParameterTypes: hasExtParameterInfos");
 }
 
+/// Derives the 'this' type for CIRGen purposes, i.e. ignoring method CVR
+/// qualification. Either or both of `rd` and `md` may be null. A null `rd`
+/// indicates that there is no meaningful 'this' type, and a null `md` can occur
+/// when calling a method pointer.
+CanQualType CIRGenTypes::deriveThisType(const CXXRecordDecl *rd,
+                                        const CXXMethodDecl *md) {
+  QualType recTy;
+  if (rd)
+    recTy = getASTContext().getTagDeclType(rd)->getCanonicalTypeInternal();
+  else
+    recTy = getASTContext().VoidTy;
----------------
andykaylor wrote:

No. It looks like this is an MS ABI thing. Would you prefer I put an `errorNYI` here until we can add a test for it?

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