AST: support protocol conformances on id/class/interfaces in MS ABI

[compnerd]

Summary

Add support for mangling ObjC protocol conformances in MS ABI as if they are COM interfaces. By diverging from the itanium mangling of objc_protocol prefixed names, this approach allows for a semi-reasonable, albeit of questionable sanity, undecoration via existing tooling. There is also the possibility of adding an extension and taking part of the namespace to add the conformance via the L and Z "modifiers", but the existing tooling would not be able to properly undecorated the symbol even though incidentally undname currently produces something legible while wine's implementation is not able to cope with the extension.

This allows for the disambiguation of overloads where the parameter differs only in the protocol conformance of the ObjC type, e.g.

@protocol P;
void f(std::vector<id>);
void f(std::vector<id<P>>);

which clang would previously fail due to the mangling being identical as the protocol conformance was ignored.

[majnemer]

lib/AST/MicrosoftMangle.cpp

2459–2465

Hmm, this is a template... I don't think this will do the right thing wrt backreferences.

2468

Probably want a comment stating that this is cointerface.

[rjmccall]

The basic idea here seems fine to me; I'll leave David to review the details.

[compnerd]

scope the template back references and add a comment.

[compnerd]

Add additional test cases as discussed on IRC. These ensure that the back reference handling is correct.

[majnemer]

LGTM

[compnerd]

SVN r323547

lib/AST/MicrosoftMangle.cpp

 
 void MicrosoftCXXNameMangler::mangleType(const ObjCObjectType *T, Qualifiers,
                                          SourceRange Range) {
-  // We don't allow overloading by different protocol qualification,
-  // so mangling them isn't necessary.
-  mangleType(T->getBaseType(), Range, QMM_Drop);
+  if (T->qual_empty())
+    return mangleType(T->getBaseType(), Range, QMM_Drop);
+
+  mangleTagTypeKind(TTK_Struct);
+
+  Out << "?$";
+  if (T->isObjCId())
+    mangleSourceName("objc_object");
+  else if (T->isObjCClass())
+    mangleSourceName("objc_class");
+  else
+    mangleSourceName(T->getInterface()->getName());
+
+  for (const auto &Q : T->quals()) {
+    Out << 'Y';
+    mangleSourceName(Q->getName());
+    Out << '@';
+  }
+  Out << '@';
+
+  Out << '@';
 }
 
 void MicrosoftCXXNameMangler::mangleType(const BlockPointerType *T,

test/CodeGenObjCXX/msabi-protocol-conformance.mm

+// RUN: %clang_cc1 -triple thumbv7-windows-msvc -fobjc-runtime=ios-6.0 -o - -emit-llvm %s | FileCheck %s
+
+@protocol P;
+@protocol Q;
+
+@class I;
+
+void f(id<P>) {}
+// CHECK-LABEL: "\01?f@@YAXPAU?$objc_object@YP@@@@@Z"
+
+void f(id<P, Q>) {}
+// CHECK-LABEL: "\01?f@@YAXPAU?$objc_object@YP@@YQ@@@@@Z"
+
+void f(Class<P>) {}
+// CHECK-LABEL: "\01?f@@YAXPAU?$objc_class@YP@@@@@Z"
+
+void f(Class<P, Q>) {}
+// CHECK-LABEL: "\01?f@@YAXPAU?$objc_class@YP@@YQ@@@@@Z"
+
+void f(I<P> *) {}
+// CHECK-LABEL: "\01?f@@YAXPAU?$I@YP@@@@@Z"
+
+void f(I<P, Q> *) {}
+// CHECK-LABEL: "\01?f@@YAXPAU?$I@YP@@YQ@@@@@Z"
+