ObjCARCAliasAnalysis.h revision 36b56886974eae4f9c5ebc96befd3e7bfe5de338 
1//===- ObjCARCAliasAnalysis.h - ObjC ARC Optimization -*- 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_TRANSFORMS_OBJCARC_OBJCARCALIASANALYSIS_H
24#define LLVM_TRANSFORMS_OBJCARC_OBJCARCALIASANALYSIS_H
25
26#include "llvm/Analysis/AliasAnalysis.h"
27#include "llvm/Pass.h"
28
29namespace llvm {
30namespace objcarc {
31
32  /// \brief This is a simple alias analysis implementation that uses knowledge
33  /// of ARC constructs to answer queries.
34  ///
35  /// TODO: This class could be generalized to know about other ObjC-specific
36  /// tricks. Such as knowing that ivars in the non-fragile ABI are non-aliasing
37  /// even though their offsets are dynamic.
38  class ObjCARCAliasAnalysis : public ImmutablePass,
39                               public AliasAnalysis {
40  public:
41    static char ID; // Class identification, replacement for typeinfo
42    ObjCARCAliasAnalysis() : ImmutablePass(ID) {
43      initializeObjCARCAliasAnalysisPass(*PassRegistry::getPassRegistry());
44    }
45
46  private:
47    void initializePass() override {
48      InitializeAliasAnalysis(this);
49    }
50
51    /// This method is used when a pass implements an analysis interface through
52    /// multiple inheritance.  If needed, it should override this to adjust the
53    /// this pointer as needed for the specified pass info.
54    void *getAdjustedAnalysisPointer(const void *PI) override {
55      if (PI == &AliasAnalysis::ID)
56        return static_cast<AliasAnalysis *>(this);
57      return this;
58    }
59
60    void getAnalysisUsage(AnalysisUsage &AU) const override;
61    AliasResult alias(const Location &LocA, const Location &LocB) override;
62    bool pointsToConstantMemory(const Location &Loc, bool OrLocal) override;
63    ModRefBehavior getModRefBehavior(ImmutableCallSite CS) override;
64    ModRefBehavior getModRefBehavior(const Function *F) override;
65    ModRefResult getModRefInfo(ImmutableCallSite CS,
66                               const Location &Loc) override;
67    ModRefResult getModRefInfo(ImmutableCallSite CS1,
68                               ImmutableCallSite CS2) override;
69  };
70
71} // namespace objcarc
72} // namespace llvm
73
74#endif // LLVM_TRANSFORMS_OBJCARC_OBJCARCALIASANALYSIS_H
75