1 //===- ObjCARCAliasAnalysis.h - ObjC ARC Alias Analysis ---------*- C++ -*-===//
2 //
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
6 //
7 //===----------------------------------------------------------------------===//
8 /// \file
9 /// This file declares a simple ARC-aware AliasAnalysis using special knowledge
10 /// of Objective C to enhance other optimization passes which rely on the Alias
11 /// Analysis infrastructure.
12 ///
13 /// WARNING: This file knows about certain library functions. It recognizes them
14 /// by name, and hardwires knowledge of their semantics.
15 ///
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.
19 ///
20 //===----------------------------------------------------------------------===//
21 
22 #ifndef LLVM_ANALYSIS_OBJCARCALIASANALYSIS_H
23 #define LLVM_ANALYSIS_OBJCARCALIASANALYSIS_H
24 
25 #include "llvm/Analysis/AliasAnalysis.h"
26 #include "llvm/Pass.h"
27 
28 namespace llvm {
29 namespace objcarc {
30 
31 /// This is a simple alias analysis implementation that uses knowledge
32 /// of ARC constructs to answer queries.
33 ///
34 /// TODO: This class could be generalized to know about other ObjC-specific
35 /// tricks. Such as knowing that ivars in the non-fragile ABI are non-aliasing
36 /// even though their offsets are dynamic.
37 class ObjCARCAAResult : public AAResultBase<ObjCARCAAResult> {
38   friend AAResultBase<ObjCARCAAResult>;
39 
40   const DataLayout &DL;
41 
42 public:
ObjCARCAAResult(const DataLayout & DL)43   explicit ObjCARCAAResult(const DataLayout &DL) : AAResultBase(), DL(DL) {}
ObjCARCAAResult(ObjCARCAAResult && Arg)44   ObjCARCAAResult(ObjCARCAAResult &&Arg)
45       : AAResultBase(std::move(Arg)), DL(Arg.DL) {}
46 
47   /// Handle invalidation events from the new pass manager.
48   ///
49   /// By definition, this result is stateless and so remains valid.
invalidate(Function &,const PreservedAnalyses &,FunctionAnalysisManager::Invalidator &)50   bool invalidate(Function &, const PreservedAnalyses &,
51                   FunctionAnalysisManager::Invalidator &) {
52     return false;
53   }
54 
55   AliasResult alias(const MemoryLocation &LocA, const MemoryLocation &LocB,
56                     AAQueryInfo &AAQI);
57   bool pointsToConstantMemory(const MemoryLocation &Loc, AAQueryInfo &AAQI,
58                               bool OrLocal);
59 
60   using AAResultBase::getModRefBehavior;
61   FunctionModRefBehavior getModRefBehavior(const Function *F);
62 
63   using AAResultBase::getModRefInfo;
64   ModRefInfo getModRefInfo(const CallBase *Call, const MemoryLocation &Loc,
65                            AAQueryInfo &AAQI);
66 };
67 
68 /// Analysis pass providing a never-invalidated alias analysis result.
69 class ObjCARCAA : public AnalysisInfoMixin<ObjCARCAA> {
70   friend AnalysisInfoMixin<ObjCARCAA>;
71   static AnalysisKey Key;
72 
73 public:
74   typedef ObjCARCAAResult Result;
75 
76   ObjCARCAAResult run(Function &F, FunctionAnalysisManager &AM);
77 };
78 
79 /// Legacy wrapper pass to provide the ObjCARCAAResult object.
80 class ObjCARCAAWrapperPass : public ImmutablePass {
81   std::unique_ptr<ObjCARCAAResult> Result;
82 
83 public:
84   static char ID;
85 
86   ObjCARCAAWrapperPass();
87 
getResult()88   ObjCARCAAResult &getResult() { return *Result; }
getResult()89   const ObjCARCAAResult &getResult() const { return *Result; }
90 
91   bool doInitialization(Module &M) override;
92   bool doFinalization(Module &M) override;
93   void getAnalysisUsage(AnalysisUsage &AU) const override;
94 };
95 
96 } // namespace objcarc
97 } // namespace llvm
98 
99 #endif
100