[ObjC][ARC] Don't add operand bundle `clang.arc.attachedcall` to a call if the call already has the operand bundle

[ahatanak]

Summary

This bug was causing the call to replaceAllUsesWith to crash because the old call instruction and the new call instruction were the same.

rdar://74957948

[ahatanak]

We could emit a call to @llvm.objc.retain instead of the call to @llvm.objc.retainAutoreleasedReturnValue, but this doesn't seem to happen often and ARC optimizer can remove or replace the call anyway, so I'm just letting the front-end emit @llvm.objc.retainAutoreleasedReturnValue for simplicity.

[ahatanak]

On second thought, I think we should emit a call to @llvm.objc.retain instead of a call to @llvm.objc.retainAutoreleasedReturnValue. I think we might want to remove ARC optimizer's code that converts calls to @llvm.objc.retainAutoreleasedReturnValue to calls to @llvm.objc.retain since it sometimes does the transformation when it shouldn't and we won't need that transformation once we switch to using the clang.arc.attachedcall operand bundle.

[ahatanak]

Emit a call to @llvm.objc.retain instead of a call to @llvm.objc.retainAutoreleasedReturnValue.

[ahatanak]

Check the presence of the operand bundle earlier in emitARCOperationAfterCall.

[rjmccall]

LGTM

clang/lib/CodeGen/CGObjC.cpp

 
 // FIXME: We should find a way to emit the runtime call immediately
 // after the call is emitted to eliminate the need for this function.
 static llvm::Value *emitARCOperationAfterCall(CodeGenFunction &CGF,
                                               llvm::Value *value,
                                               ValueTransform doAfterCall,
                                               ValueTransform doFallback) {
   CGBuilderTy::InsertPoint ip = CGF.Builder.saveIP();
+  auto *callBase = dyn_cast<llvm::CallBase>(value);
 
-  if (llvm::CallInst *call = dyn_cast<llvm::CallInst>(value)) {
+  if (callBase && llvm::objcarc::hasAttachedCallOpBundle(callBase)) {
+    // Fall back if the call base has operand bundle "clang.arc.attachedcall".
+    value = doFallback(CGF, value);
+  } else if (llvm::CallInst *call = dyn_cast<llvm::CallInst>(value)) {
     // Place the retain immediately following the call.
     CGF.Builder.SetInsertPoint(call->getParent(),
                                ++llvm::BasicBlock::iterator(call));
     value = doAfterCall(CGF, value);
   } else if (llvm::InvokeInst *invoke = dyn_cast<llvm::InvokeInst>(value)) {
     // Place the retain at the beginning of the normal destination block.
     llvm::BasicBlock *BB = invoke->getNormalDest();
     CGF.Builder.SetInsertPoint(BB, BB->begin());

clang/test/CodeGenObjCXX/arc-rv-attr.mm

+// RUN: %clang_cc1 -triple arm64-apple-ios9 -fobjc-runtime=ios-9.0 -fobjc-arc -std=c++11 -O -disable-llvm-passes -emit-llvm -o - %s | FileCheck %s -check-prefix=CHECK
+
+id foo(void);
+
+// CHECK-LABEL: define{{.*}} void @_Z14test_list_initv(
+// CHECK: %[[CALL1:.*]] = call i8* @_Z3foov() [ "clang.arc.attachedcall"(i64 0) ]
+// CHECK: call i8* @llvm.objc.retain(i8* %[[CALL1]])
+
+void test_list_init() {
+  auto t = id{foo()};
+}