lib/Transforms/ObjCARC/ProvenanceAnalysis.h

   1 //===- ProvenanceAnalysis.h - ObjC ARC Optimization -------------*- 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 //
   9 /// \file
  10 ///
  11 /// This file declares a special form of Alias Analysis called ``Provenance
  12 /// Analysis''. The word ``provenance'' refers to the history of the ownership
  13 /// of an object. Thus ``Provenance Analysis'' is an analysis which attempts to
  14 /// use various techniques to determine if locally
  15 ///
  16 /// WARNING: This file knows about certain library functions. It recognizes them
  17 /// by name, and hardwires knowledge of their semantics.
  18 ///
  19 /// WARNING: This file knows about how certain Objective-C library functions are
  20 /// used. Naive LLVM IR transformations which would otherwise be
  21 /// behavior-preserving may break these assumptions.
  22 //
  23 //===----------------------------------------------------------------------===//
  24
  25 #ifndef LLVM_LIB_TRANSFORMS_OBJCARC_PROVENANCEANALYSIS_H
  26 #define LLVM_LIB_TRANSFORMS_OBJCARC_PROVENANCEANALYSIS_H
  27
  28 #include "llvm/ADT/DenseMap.h"
  29 #include "llvm/Analysis/AliasAnalysis.h"
  30 #include "llvm/IR/ValueHandle.h"
  31 #include <utility>
  32
  33 namespace llvm {
  34
  35 class DataLayout;
  36 class PHINode;
  37 class SelectInst;
  38 class Value;
  39
  40 namespace objcarc {
  41
  42 /// This is similar to BasicAliasAnalysis, and it uses many of the same
  43 /// techniques, except it uses special ObjC-specific reasoning about pointer
  44 /// relationships.
  45 ///
  46 /// In this context ``Provenance'' is defined as the history of an object's
  47 /// ownership. Thus ``Provenance Analysis'' is defined by using the notion of
  48 /// an ``independent provenance source'' of a pointer to determine whether or
  49 /// not two pointers have the same provenance source and thus could
  50 /// potentially be related.
  51 class ProvenanceAnalysis {
  52   AliasAnalysis *AA;
  53
  54   using ValuePairTy = std::pair<const Value *, const Value *>;
  55   using CachedResultsTy = DenseMap<ValuePairTy, bool>;
  56
  57   CachedResultsTy CachedResults;
  58
  59   DenseMap<const Value *, WeakTrackingVH> UnderlyingObjCPtrCache;
  60
  61   bool relatedCheck(const Value *A, const Value *B, const DataLayout &DL);
  62   bool relatedSelect(const SelectInst *A, const Value *B);
  63   bool relatedPHI(const PHINode *A, const Value *B);
  64
  65 public:
  66   ProvenanceAnalysis() = default;
  67   ProvenanceAnalysis(const ProvenanceAnalysis &) = delete;
  68   ProvenanceAnalysis &operator=(const ProvenanceAnalysis &) = delete;
  69
  70   void setAA(AliasAnalysis *aa) { AA = aa; }
  71
  72   AliasAnalysis *getAA() const { return AA; }
  73
  74   bool related(const Value *A, const Value *B, const DataLayout &DL);
  75
  76   void clear() {
  77     CachedResults.clear();
  78     UnderlyingObjCPtrCache.clear();
  79   }
  80 };
  81
  82 } // end namespace objcarc
  83
  84 } // end namespace llvm
  85
  86 #endif // LLVM_LIB_TRANSFORMS_OBJCARC_PROVENANCEANALYSIS_H