1 //===- ObjCARCAliasAnalysis.h - ObjC ARC Alias Analysis ---------*- C++ -*-===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 /// \file
10 /// This file declares a simple ARC-aware AliasAnalysis using special knowledge
11 /// of Objective C to enhance other optimization passes which rely on the Alias
12 /// Analysis infrastructure.
13 ///
14 /// WARNING: This file knows about certain library functions. It recognizes them
15 /// by name, and hardwires knowledge of their semantics.
16 ///
17 /// WARNING: This file knows about how certain Objective-C library functions are
18 /// used. Naive LLVM IR transformations which would otherwise be
19 /// behavior-preserving may break these assumptions.
20 ///
21 //===----------------------------------------------------------------------===//
22 
23 #ifndef LLVM_ANALYSIS_OBJCARCALIASANALYSIS_H
24 #define LLVM_ANALYSIS_OBJCARCALIASANALYSIS_H
25 
26 #include "llvm/Analysis/AliasAnalysis.h"
27 #include "llvm/Analysis/TargetLibraryInfo.h"
28 #include "llvm/Pass.h"
29 
30 namespace llvm {
31 namespace objcarc {
32 
33 /// \brief This is a simple alias analysis implementation that uses knowledge
34 /// of ARC constructs to answer queries.
35 ///
36 /// TODO: This class could be generalized to know about other ObjC-specific
37 /// tricks. Such as knowing that ivars in the non-fragile ABI are non-aliasing
38 /// even though their offsets are dynamic.
39 class ObjCARCAAResult : public AAResultBase<ObjCARCAAResult> {
40   friend AAResultBase<ObjCARCAAResult>;
41 
42   const DataLayout &DL;
43 
44 public:
ObjCARCAAResult(const DataLayout & DL,const TargetLibraryInfo & TLI)45   explicit ObjCARCAAResult(const DataLayout &DL, const TargetLibraryInfo &TLI)
46       : AAResultBase(TLI), DL(DL) {}
ObjCARCAAResult(ObjCARCAAResult && Arg)47   ObjCARCAAResult(ObjCARCAAResult &&Arg)
48       : AAResultBase(std::move(Arg)), DL(Arg.DL) {}
49 
50   /// Handle invalidation events from the new pass manager.
51   ///
52   /// By definition, this result is stateless and so remains valid.
invalidate(Function &,const PreservedAnalyses &)53   bool invalidate(Function &, const PreservedAnalyses &) { return false; }
54 
55   AliasResult alias(const MemoryLocation &LocA, const MemoryLocation &LocB);
56   bool pointsToConstantMemory(const MemoryLocation &Loc, bool OrLocal);
57 
58   using AAResultBase::getModRefBehavior;
59   FunctionModRefBehavior getModRefBehavior(const Function *F);
60 
61   using AAResultBase::getModRefInfo;
62   ModRefInfo getModRefInfo(ImmutableCallSite CS, const MemoryLocation &Loc);
63 };
64 
65 /// Analysis pass providing a never-invalidated alias analysis result.
66 class ObjCARCAA {
67 public:
68   typedef ObjCARCAAResult Result;
69 
70   /// \brief Opaque, unique identifier for this analysis pass.
ID()71   static void *ID() { return (void *)&PassID; }
72 
73   ObjCARCAAResult run(Function &F, AnalysisManager<Function> *AM);
74 
75   /// \brief Provide access to a name for this pass for debugging purposes.
name()76   static StringRef name() { return "ObjCARCAA"; }
77 
78 private:
79   static char PassID;
80 };
81 
82 /// Legacy wrapper pass to provide the ObjCARCAAResult object.
83 class ObjCARCAAWrapperPass : public ImmutablePass {
84   std::unique_ptr<ObjCARCAAResult> Result;
85 
86 public:
87   static char ID;
88 
89   ObjCARCAAWrapperPass();
90 
getResult()91   ObjCARCAAResult &getResult() { return *Result; }
getResult()92   const ObjCARCAAResult &getResult() const { return *Result; }
93 
94   bool doInitialization(Module &M) override;
95   bool doFinalization(Module &M) override;
96   void getAnalysisUsage(AnalysisUsage &AU) const override;
97 };
98 
99 } // namespace objcarc
100 } // namespace llvm
101 
102 #endif
103