[objc] Fix memory leak in CGObjCMac.cpp

[rjmccall]

Summary

A memory leak was introduced in https://reviews.llvm.org/D88329

CGObjCMac.cpp was leaking a MangleContext everytime it mangled
an ObjC method. We now have an instance variable that allocates
and deallocates the context.

[rjmccall]

Oh, oops, I should've caught this in review. I assume you still need a commit?

[ellis]

Yes please commit for me :)

[ellis]

Fix a comment to reference the correct method.

Thanks to @vsapsai for pointing this out.

[JDevlieghere]

Thanks for updating the comment in dsymutil!

[rjmccall]

Committed (with substantial changes) as 984744a1314ce165378e7945bc45995302a8cb80

clang/lib/CodeGen/CGObjCMac.cpp

CodeGen::RValue EmitMessageSend(CodeGen::CodeGenFunction &CGF,
                                   const ObjCInterfaceDecl *ClassReceiver,
                                   const ObjCCommonTypesHelper &ObjCTypes);
 
   /// EmitImageInfo - Emit the image info marker used to encode some module
   /// level information.
   void EmitImageInfo();
 
 public:
-  CGObjCCommonMac(CodeGen::CodeGenModule &cgm) :
-    CGObjCRuntime(cgm), VMContext(cgm.getLLVMContext()) { }
+  CGObjCCommonMac(CodeGen::CodeGenModule &cgm)
+      : CGObjCRuntime(cgm), VMContext(cgm.getLLVMContext()),
+        Mangler(cgm.getContext().createMangleContext()) {}
 
   bool isNonFragileABI() const {
     return ObjCABI == 2;
   }
 
   ConstantAddress GenerateConstantString(const StringLiteral *SL) override;
   ConstantAddress GenerateConstantNSString(const StringLiteral *SL);
 
public:
   std::string getRCBlockLayoutStr(CodeGen::CodeGenModule &CGM,
                                   const CGBlockInfo &blockInfo) override;
 
   llvm::Constant *BuildByrefLayout(CodeGen::CodeGenModule &CGM,
                                    QualType T) override;
 
 private:
   void fillRunSkipBlockVars(CodeGenModule &CGM, const CGBlockInfo &blockInfo);
+  std::unique_ptr<MangleContext> Mangler;
 };
 
 namespace {
 
 enum class MethodListType {
   CategoryInstanceMethods,
   CategoryClassMethods,
   InstanceMethods,
llvm::Function *CGObjCCommonMac::GenerateMethod(const ObjCMethodDecl *OMD,
                                                 const ObjCContainerDecl *CD) {
   llvm::Function *Method;
 
   if (OMD->isDirectMethod()) {
     Method = GenerateDirectMethod(OMD, CD);
   } else {
     SmallString<256> Name;
     llvm::raw_svector_ostream OS(Name);
-    const auto &MC = CGM.getContext().createMangleContext();
-    MC->mangleObjCMethodName(OMD, OS, /*includePrefixByte=*/true,
+    Mangler->mangleObjCMethodName(OMD, OS, /*includePrefixByte=*/true,
                                   /*includeCategoryNamespace=*/true);
 
     CodeGenTypes &Types = CGM.getTypes();
     llvm::FunctionType *MethodTy =
         Types.GetFunctionType(Types.arrangeObjCMethodDeclaration(OMD));
     Method =
         llvm::Function::Create(MethodTy, llvm::GlobalValue::InternalLinkage,
                                Name.str(), &CGM.getModule());
   }
OldFn->replaceAllUsesWith(
         llvm::ConstantExpr::getBitCast(Fn, OldFn->getType()));
     OldFn->eraseFromParent();
 
     // Replace the cached function in the map.
     I->second = Fn;
   } else {
     SmallString<256> Name;
     llvm::raw_svector_ostream OS(Name);
-    const auto &MC = CGM.getContext().createMangleContext();
-    MC->mangleObjCMethodName(OMD, OS, /*includePrefixByte=*/true,
+    Mangler->mangleObjCMethodName(OMD, OS, /*includePrefixByte=*/true,
                                   /*includeCategoryNamespace=*/false);
 
     Fn = llvm::Function::Create(MethodTy, llvm::GlobalValue::ExternalLinkage,
                                 Name.str(), &CGM.getModule());
     DirectMethodDefinitions.insert(std::make_pair(COMD, Fn));
   }
 
   return Fn;
 }