MS ABI: Handle member function pointers returning a member data pointer

MSVC doesn't decide what the inheritance model for a returned member
pointer *until* a call expression returns it.

This fixes PR20017.

llvm-svn: 215164

3 files changed, 16 insertions, 1 deletions

diff --git a/clang/lib/CodeGen/CGCXXABI.h b/clang/lib/CodeGen/CGCXXABI.h
index 91e49707bae..40418b60c1b 100644
--- a/clang/lib/CodeGen/CGCXXABI.h
+++ b/clang/lib/CodeGen/CGCXXABI.h
@@ -156,6 +156,11 @@ public:
   /// (in the C++ sense) with an LLVM zeroinitializer.
   virtual bool isZeroInitializable(const MemberPointerType *MPT);
 
+  /// Return whether or not a member pointers type is convertible to an IR type.
+  virtual bool isMemberPointerConvertible(const MemberPointerType *MPT) const {
+    return true;
+  }
+
   /// Create a null member pointer of the given type.
   virtual llvm::Constant *EmitNullMemberPointer(const MemberPointerType *MPT);
 
diff --git a/clang/lib/CodeGen/CodeGenTypes.cpp b/clang/lib/CodeGen/CodeGenTypes.cpp
index d4e22623e02..6b0e4ad8b31 100644
--- a/clang/lib/CodeGen/CodeGenTypes.cpp
+++ b/clang/lib/CodeGen/CodeGenTypes.cpp
@@ -187,6 +187,11 @@ static bool isSafeToConvert(const RecordDecl *RD, CodeGenTypes &CGT) {
 /// we've temporarily deferred expanding the type because we're in a recursive
 /// context.
 bool CodeGenTypes::isFuncParamTypeConvertible(QualType Ty) {
+  // Some ABIs cannot have their member pointers represented in IR unless
+  // certain circumstances have been reached.
+  if (const auto *MPT = Ty->getAs<MemberPointerType>())
+    return getCXXABI().isMemberPointerConvertible(MPT);
+
   // If this isn't a tagged type, we can convert it!
   const TagType *TT = Ty->getAs<TagType>();
   if (!TT) return true;
@@ -194,7 +199,7 @@ bool CodeGenTypes::isFuncParamTypeConvertible(QualType Ty) {
   // Incomplete types cannot be converted.
   if (TT->isIncompleteType())
     return false;
-  
+
   // If this is an enum, then it is always safe to convert.
   const RecordType *RT = dyn_cast<RecordType>(TT);
   if (!RT) return true;
diff --git a/clang/lib/CodeGen/MicrosoftCXXABI.cpp b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
index 23f9768d4a8..d01fb7bf34f 100644
--- a/clang/lib/CodeGen/MicrosoftCXXABI.cpp
+++ b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
@@ -482,6 +482,11 @@ public:
 
   bool isZeroInitializable(const MemberPointerType *MPT) override;
 
+  bool isMemberPointerConvertible(const MemberPointerType *MPT) const override {
+    const CXXRecordDecl *RD = MPT->getMostRecentCXXRecordDecl();
+    return RD->getAttr<MSInheritanceAttr>() != nullptr;
+  }
+
   llvm::Constant *EmitNullMemberPointer(const MemberPointerType *MPT) override;
 
   llvm::Constant *EmitMemberDataPointer(const MemberPointerType *MPT,