Push record return type classification into CGCXXABI

In the Microsoft C++ ABI, instance methods always return records
indirectly via the second hidden parameter.  This was implemented in
X86_32ABIInfo, but not WinX86_64ABIInfo.

Rather than exposing a handful of boolean methods in the CGCXXABI
interface, we can expose a single method that applies C++ ABI return
value classification rules.

llvm-svn: 208733

clang/lib/CodeGen/CGCXXABI.h

@@ -93,8 +93,9 @@ class CGCXXABI {
   /// when called virtually, and code generation does not support the case.
   virtual bool HasThisReturn(GlobalDecl GD) const { return false; }
 
-  /// Returns true if the given record type should be returned indirectly.
-  virtual bool isReturnTypeIndirect(const CXXRecordDecl *RD) const = 0;
+  /// If the C++ ABI requires the given type be returned in a particular way,
+  /// this method sets RetAI and returns true.
+  virtual bool classifyReturnType(CGFunctionInfo &FI) const = 0;
 
   /// Specify how one should pass an argument of a record type.
   enum RecordArgABI {

clang/lib/CodeGen/ItaniumCXXABI.cpp

@@ -52,11 +52,7 @@ class ItaniumCXXABI : public CodeGen::CGCXXABI {
     CGCXXABI(CGM), UseARMMethodPtrABI(UseARMMethodPtrABI),
     UseARMGuardVarABI(UseARMGuardVarABI) { }
 
-  bool isReturnTypeIndirect(const CXXRecordDecl *RD) const override {
-    // Structures with either a non-trivial destructor or a non-trivial
-    // copy constructor are always indirect.
-    return !RD->hasTrivialDestructor() || RD->hasNonTrivialCopyConstructor();
-  }
+  bool classifyReturnType(CGFunctionInfo &FI) const override;
 
   RecordArgABI getRecordArgABI(const CXXRecordDecl *RD) const override {
     // Structures with either a non-trivial destructor or a non-trivial
@@ -761,6 +757,21 @@ ItaniumCXXABI::EmitMemberPointerIsNotNull(CodeGenFunction &CGF,
   return Result;
 }
 
+bool ItaniumCXXABI::classifyReturnType(CGFunctionInfo &FI) const {
+  const CXXRecordDecl *RD = FI.getReturnType()->getAsCXXRecordDecl();
+  if (!RD)
+    return false;
+
+  // Return indirectly if we have a non-trivial copy ctor or non-trivial dtor.
+  if (RD->hasNonTrivialDestructor() || RD->hasNonTrivialCopyConstructor()) {
+    FI.getReturnInfo() = ABIArgInfo::getIndirect(0, /*ByVal=*/false);
+    return true;
+  }
+
+  // Otherwise, use the normal C ABI rules.
+  return false;
+}
+
 /// The Itanium ABI requires non-zero initialization only for data
 /// member pointers, for which '0' is a valid offset.
 bool ItaniumCXXABI::isZeroInitializable(const MemberPointerType *MPT) {

clang/lib/CodeGen/MicrosoftCXXABI.cpp

@@ -39,10 +39,7 @@ class MicrosoftCXXABI : public CGCXXABI {
 
   bool HasThisReturn(GlobalDecl GD) const override;
 
-  bool isReturnTypeIndirect(const CXXRecordDecl *RD) const override {
-    // Structures that are not C++03 PODs are always indirect.
-    return !RD->isPOD();
-  }
+  bool classifyReturnType(CGFunctionInfo &FI) const override;
 
   RecordArgABI getRecordArgABI(const CXXRecordDecl *RD) const override;
 
@@ -459,6 +456,27 @@ bool MicrosoftCXXABI::HasThisReturn(GlobalDecl GD) const {
   return isa<CXXConstructorDecl>(GD.getDecl());
 }
 
+bool MicrosoftCXXABI::classifyReturnType(CGFunctionInfo &FI) const {
+  const CXXRecordDecl *RD = FI.getReturnType()->getAsCXXRecordDecl();
+  if (!RD)
+    return false;
+
+  if (FI.isInstanceMethod()) {
+    // If it's an instance method, aggregates are always returned indirectly via
+    // the second parameter.
+    FI.getReturnInfo() = ABIArgInfo::getIndirect(0, /*ByVal=*/false);
+    FI.getReturnInfo().setSRetAfterThis(FI.isInstanceMethod());
+    return true;
+  } else if (!RD->isPOD()) {
+    // If it's a free function, non-POD types are returned indirectly.
+    FI.getReturnInfo() = ABIArgInfo::getIndirect(0, /*ByVal=*/false);
+    return true;
+  }
+
+  // Otherwise, use the C ABI rules.
+  return false;
+}
+
 void MicrosoftCXXABI::BuildConstructorSignature(
     const CXXConstructorDecl *Ctor, CXXCtorType Type, CanQualType &ResTy,
     SmallVectorImpl<CanQualType> &ArgTys) {