+Constant *ObjCARCContract::getRetainRVCallee(Module *M) {
+ if (!RetainRVCallee) {
+ LLVMContext &C = M->getContext();
+ Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
+ Type *Params[] = { I8X };
+ FunctionType *FTy = FunctionType::get(I8X, Params, /*isVarArg=*/false);
+ AttributeSet Attribute =
+ AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
+ Attribute::NoUnwind);
+ RetainRVCallee =
+ M->getOrInsertFunction("objc_retainAutoreleasedReturnValue", FTy,
+ Attribute);
+ }
+ return RetainRVCallee;
+}
+
+/// Turn objc_retain into objc_retainAutoreleasedReturnValue if the operand is a
+/// return value. We do this late so we do not disrupt the dataflow analysis in
+/// ObjCARCOpt.
+bool
+ObjCARCContract::OptimizeRetainCall(Function &F, Instruction *Retain) {
+ ImmutableCallSite CS(GetObjCArg(Retain));
+ const Instruction *Call = CS.getInstruction();
+ if (!Call)
+ return false;
+ if (Call->getParent() != Retain->getParent())
+ return false;
+
+ // Check that the call is next to the retain.
+ BasicBlock::const_iterator I = Call;
+ ++I;
+ while (IsNoopInstruction(I)) ++I;
+ if (&*I != Retain)
+ return false;
+
+ // Turn it to an objc_retainAutoreleasedReturnValue.
+ Changed = true;
+ ++NumPeeps;
+
+ DEBUG(dbgs() << "Transforming objc_retain => "
+ "objc_retainAutoreleasedReturnValue since the operand is a "
+ "return value.\nOld: "<< *Retain << "\n");
+
+ // We do not have to worry about tail calls/does not throw since
+ // retain/retainRV have the same properties.
+ cast<CallInst>(Retain)->setCalledFunction(getRetainRVCallee(F.getParent()));
+
+ DEBUG(dbgs() << "New: " << *Retain << "\n");
+ return true;
+}
+