include/llvm/Analysis/CFLSteensAliasAnalysis.h

   1 //==- CFLSteensAliasAnalysis.h - Unification-based 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 is the interface for LLVM's unification-based alias analysis
  10 /// implemented with CFL graph reachability.
  11 ///
  12 //===----------------------------------------------------------------------===//
  13
  14 #ifndef LLVM_ANALYSIS_CFLSTEENSALIASANALYSIS_H
  15 #define LLVM_ANALYSIS_CFLSTEENSALIASANALYSIS_H
  16
  17 #include "llvm/ADT/DenseMap.h"
  18 #include "llvm/ADT/Optional.h"
  19 #include "llvm/Analysis/AliasAnalysis.h"
  20 #include "llvm/Analysis/CFLAliasAnalysisUtils.h"
  21 #include "llvm/Analysis/MemoryLocation.h"
  22 #include "llvm/IR/PassManager.h"
  23 #include "llvm/Pass.h"
  24 #include "llvm/Support/Casting.h"
  25 #include <forward_list>
  26 #include <memory>
  27
  28 namespace llvm {
  29
  30 class Function;
  31 class TargetLibraryInfo;
  32
  33 namespace cflaa {
  34
  35 struct AliasSummary;
  36
  37 } // end namespace cflaa
  38
  39 class CFLSteensAAResult : public AAResultBase<CFLSteensAAResult> {
  40   friend AAResultBase<CFLSteensAAResult>;
  41
  42   class FunctionInfo;
  43
  44 public:
  45   explicit CFLSteensAAResult(const TargetLibraryInfo &TLI);
  46   CFLSteensAAResult(CFLSteensAAResult &&Arg);
  47   ~CFLSteensAAResult();
  48
  49   /// Handle invalidation events from the new pass manager.
  50   ///
  51   /// By definition, this result is stateless and so remains valid.
  52   bool invalidate(Function &, const PreservedAnalyses &,
  53                   FunctionAnalysisManager::Invalidator &) {
  54     return false;
  55   }
  56
  57   /// Inserts the given Function into the cache.
  58   void scan(Function *Fn);
  59
  60   void evict(Function *Fn);
  61
  62   /// Ensures that the given function is available in the cache.
  63   /// Returns the appropriate entry from the cache.
  64   const Optional<FunctionInfo> &ensureCached(Function *Fn);
  65
  66   /// Get the alias summary for the given function
  67   /// Return nullptr if the summary is not found or not available
  68   const cflaa::AliasSummary *getAliasSummary(Function &Fn);
  69
  70   AliasResult query(const MemoryLocation &LocA, const MemoryLocation &LocB);
  71
  72   AliasResult alias(const MemoryLocation &LocA, const MemoryLocation &LocB,
  73                     AAQueryInfo &AAQI) {
  74     if (LocA.Ptr == LocB.Ptr)
  75       return MustAlias;
  76
  77     // Comparisons between global variables and other constants should be
  78     // handled by BasicAA.
  79     // CFLSteensAA may report NoAlias when comparing a GlobalValue and
  80     // ConstantExpr, but every query needs to have at least one Value tied to a
  81     // Function, and neither GlobalValues nor ConstantExprs are.
  82     if (isa<Constant>(LocA.Ptr) && isa<Constant>(LocB.Ptr))
  83       return AAResultBase::alias(LocA, LocB, AAQI);
  84
  85     AliasResult QueryResult = query(LocA, LocB);
  86     if (QueryResult == MayAlias)
  87       return AAResultBase::alias(LocA, LocB, AAQI);
  88
  89     return QueryResult;
  90   }
  91
  92 private:
  93   const TargetLibraryInfo &TLI;
  94
  95   /// Cached mapping of Functions to their StratifiedSets.
  96   /// If a function's sets are currently being built, it is marked
  97   /// in the cache as an Optional without a value. This way, if we
  98   /// have any kind of recursion, it is discernable from a function
  99   /// that simply has empty sets.
 100   DenseMap<Function *, Optional<FunctionInfo>> Cache;
 101   std::forward_list<cflaa::FunctionHandle<CFLSteensAAResult>> Handles;
 102
 103   FunctionInfo buildSetsFrom(Function *F);
 104 };
 105
 106 /// Analysis pass providing a never-invalidated alias analysis result.
 107 ///
 108 /// FIXME: We really should refactor CFL to use the analysis more heavily, and
 109 /// in particular to leverage invalidation to trigger re-computation of sets.
 110 class CFLSteensAA : public AnalysisInfoMixin<CFLSteensAA> {
 111   friend AnalysisInfoMixin<CFLSteensAA>;
 112
 113   static AnalysisKey Key;
 114
 115 public:
 116   using Result = CFLSteensAAResult;
 117
 118   CFLSteensAAResult run(Function &F, FunctionAnalysisManager &AM);
 119 };
 120
 121 /// Legacy wrapper pass to provide the CFLSteensAAResult object.
 122 class CFLSteensAAWrapperPass : public ImmutablePass {
 123   std::unique_ptr<CFLSteensAAResult> Result;
 124
 125 public:
 126   static char ID;
 127
 128   CFLSteensAAWrapperPass();
 129
 130   CFLSteensAAResult &getResult() { return *Result; }
 131   const CFLSteensAAResult &getResult() const { return *Result; }
 132
 133   void initializePass() override;
 134   void getAnalysisUsage(AnalysisUsage &AU) const override;
 135 };
 136
 137 // createCFLSteensAAWrapperPass - This pass implements a set-based approach to
 138 // alias analysis.
 139 ImmutablePass *createCFLSteensAAWrapperPass();
 140
 141 } // end namespace llvm
 142
 143 #endif // LLVM_ANALYSIS_CFLSTEENSALIASANALYSIS_H