1 //===- ObjCARC.h - ObjC ARC Optimization --------------*- C++ -*-----------===//
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //===----------------------------------------------------------------------===//
9 /// This file defines common definitions/declarations used by the ObjC ARC
10 /// Optimizer. ARC stands for Automatic Reference Counting and is a system for
11 /// managing reference counts for objects in Objective C.
13 /// WARNING: This file knows about certain library functions. It recognizes them
14 /// by name, and hardwires knowledge of their semantics.
16 /// WARNING: This file knows about how certain Objective-C library functions are
17 /// used. Naive LLVM IR transformations which would otherwise be
18 /// behavior-preserving may break these assumptions.
20 //===----------------------------------------------------------------------===//
22 #ifndef LLVM_LIB_TRANSFORMS_OBJCARC_OBJCARC_H
23 #define LLVM_LIB_TRANSFORMS_OBJCARC_OBJCARC_H
25 #include "llvm/ADT/StringSwitch.h"
26 #include "llvm/Analysis/AliasAnalysis.h"
27 #include "llvm/Analysis/ObjCARCAnalysisUtils.h"
28 #include "llvm/Analysis/ObjCARCInstKind.h"
29 #include "llvm/Analysis/Passes.h"
30 #include "llvm/Transforms/Utils/Local.h"
31 #include "llvm/Analysis/ValueTracking.h"
32 #include "llvm/IR/CallSite.h"
33 #include "llvm/IR/InstIterator.h"
34 #include "llvm/IR/Module.h"
35 #include "llvm/Pass.h"
36 #include "llvm/Transforms/ObjCARC.h"
45 /// Erase the given instruction.
47 /// Many ObjC calls return their argument verbatim,
48 /// so if it's such a call and the return value has users, replace them with the
51 static inline void EraseInstruction(Instruction *CI) {
52 Value *OldArg = cast<CallInst>(CI)->getArgOperand(0);
54 bool Unused = CI->use_empty();
57 // Replace the return value with the argument.
58 assert((IsForwarding(GetBasicARCInstKind(CI)) ||
59 (IsNoopOnNull(GetBasicARCInstKind(CI)) &&
60 IsNullOrUndef(OldArg->stripPointerCasts()))) &&
61 "Can't delete non-forwarding instruction with users!");
62 CI->replaceAllUsesWith(OldArg);
65 CI->eraseFromParent();
68 RecursivelyDeleteTriviallyDeadInstructions(OldArg);
71 /// If Inst is a ReturnRV and its operand is a call or invoke, return the
72 /// operand. Otherwise return null.
73 static inline const Instruction *getreturnRVOperand(const Instruction &Inst,
75 if (Class != ARCInstKind::RetainRV)
78 const auto *Opnd = Inst.getOperand(0)->stripPointerCasts();
79 if (const auto *C = dyn_cast<CallInst>(Opnd))
81 return dyn_cast<InvokeInst>(Opnd);
84 /// Return the list of PHI nodes that are equivalent to PN.
85 template<class PHINodeTy, class VectorTy>
86 void getEquivalentPHIs(PHINodeTy &PN, VectorTy &PHIList) {
87 auto *BB = PN.getParent();
88 for (auto &P : BB->phis()) {
89 if (&P == &PN) // Do not add PN to the list.
91 unsigned I = 0, E = PN.getNumIncomingValues();
93 auto *BB = PN.getIncomingBlock(I);
94 auto *PNOpnd = PN.getIncomingValue(I)->stripPointerCasts();
95 auto *POpnd = P.getIncomingValueForBlock(BB)->stripPointerCasts();
100 PHIList.push_back(&P);
104 } // end namespace objcarc
105 } // end namespace llvm