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