include/llvm/Analysis/PhiValues.h

   1 //===- PhiValues.h - Phi Value 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 //
   9 // This file defines the PhiValues class, and associated passes, which can be
  10 // used to find the underlying values of the phis in a function, i.e. the
  11 // non-phi values that can be found by traversing the phi graph.
  12 //
  13 // This information is computed lazily and cached. If new phis are added to the
  14 // function they are handled correctly, but if an existing phi has its operands
  15 // modified PhiValues has to be notified by calling invalidateValue.
  16 //
  17 //===----------------------------------------------------------------------===//
  18
  19 #ifndef LLVM_ANALYSIS_PHIVALUES_H
  20 #define LLVM_ANALYSIS_PHIVALUES_H
  21
  22 #include "llvm/ADT/DenseMap.h"
  23 #include "llvm/ADT/DenseSet.h"
  24 #include "llvm/ADT/SmallPtrSet.h"
  25 #include "llvm/ADT/SmallVector.h"
  26 #include "llvm/IR/PassManager.h"
  27 #include "llvm/IR/ValueHandle.h"
  28 #include "llvm/Pass.h"
  29
  30 namespace llvm {
  31
  32 class Use;
  33 class Value;
  34 class PHINode;
  35 class Function;
  36
  37 /// Class for calculating and caching the underlying values of phis in a
  38 /// function.
  39 ///
  40 /// Initially the PhiValues is empty, and gets incrementally populated whenever
  41 /// it is queried.
  42 class PhiValues {
  43 public:
  44   using ValueSet = SmallPtrSet<Value *, 4>;
  45
  46   /// Construct an empty PhiValues.
  47   PhiValues(const Function &F) : F(F) {}
  48
  49   /// Get the underlying values of a phi.
  50   ///
  51   /// This returns the cached value if PN has previously been processed,
  52   /// otherwise it processes it first.
  53   const ValueSet &getValuesForPhi(const PHINode *PN);
  54
  55   /// Notify PhiValues that the cached information using V is no longer valid
  56   ///
  57   /// Whenever a phi has its operands modified the cached values for that phi
  58   /// (and the phis that use that phi) become invalid. A user of PhiValues has
  59   /// to notify it of this by calling invalidateValue on either the operand or
  60   /// the phi, which will then clear the relevant cached information.
  61   void invalidateValue(const Value *V);
  62
  63   /// Free the memory used by this class.
  64   void releaseMemory();
  65
  66   /// Print out the values currently in the cache.
  67   void print(raw_ostream &OS) const;
  68
  69   /// Handle invalidation events in the new pass manager.
  70   bool invalidate(Function &, const PreservedAnalyses &,
  71                   FunctionAnalysisManager::Invalidator &);
  72
  73 private:
  74   using PhiSet = SmallPtrSet<const PHINode *, 4>;
  75   using ConstValueSet = SmallPtrSet<const Value *, 4>;
  76
  77   /// The next depth number to be used by processPhi.
  78   unsigned int NextDepthNumber = 1;
  79
  80   /// Depth numbers of phis. Phis with the same depth number are part of the
  81   /// same strongly connected component.
  82   DenseMap<const PHINode *, unsigned int> DepthMap;
  83
  84   /// Non-phi values reachable from each component.
  85   DenseMap<unsigned int, ValueSet> NonPhiReachableMap;
  86
  87   /// All values reachable from each component.
  88   DenseMap<unsigned int, ConstValueSet> ReachableMap;
  89
  90   /// A CallbackVH to notify PhiValues when a value is deleted or replaced, so
  91   /// that the cached information for that value can be cleared to avoid
  92   /// dangling pointers to invalid values.
  93   class PhiValuesCallbackVH final : public CallbackVH {
  94     PhiValues *PV;
  95     void deleted() override;
  96     void allUsesReplacedWith(Value *New) override;
  97
  98   public:
  99     PhiValuesCallbackVH(Value *V, PhiValues *PV = nullptr)
 100         : CallbackVH(V), PV(PV) {}
 101   };
 102
 103   /// A set of callbacks to the values that processPhi has seen.
 104   DenseSet<PhiValuesCallbackVH, DenseMapInfo<Value *>> TrackedValues;
 105
 106   /// The function that the PhiValues is for.
 107   const Function &F;
 108
 109   /// Process a phi so that its entries in the depth and reachable maps are
 110   /// fully populated.
 111   void processPhi(const PHINode *PN, SmallVector<const PHINode *, 8> &Stack);
 112 };
 113
 114 /// The analysis pass which yields a PhiValues
 115 ///
 116 /// The analysis does nothing by itself, and just returns an empty PhiValues
 117 /// which will get filled in as it's used.
 118 class PhiValuesAnalysis : public AnalysisInfoMixin<PhiValuesAnalysis> {
 119   friend AnalysisInfoMixin<PhiValuesAnalysis>;
 120   static AnalysisKey Key;
 121
 122 public:
 123   using Result = PhiValues;
 124   PhiValues run(Function &F, FunctionAnalysisManager &);
 125 };
 126
 127 /// A pass for printing the PhiValues for a function.
 128 ///
 129 /// This pass doesn't print whatever information the PhiValues happens to hold,
 130 /// but instead first uses the PhiValues to analyze all the phis in the function
 131 /// so the complete information is printed.
 132 class PhiValuesPrinterPass : public PassInfoMixin<PhiValuesPrinterPass> {
 133   raw_ostream &OS;
 134
 135 public:
 136   explicit PhiValuesPrinterPass(raw_ostream &OS) : OS(OS) {}
 137   PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
 138 };
 139
 140 /// Wrapper pass for the legacy pass manager
 141 class PhiValuesWrapperPass : public FunctionPass {
 142   std::unique_ptr<PhiValues> Result;
 143
 144 public:
 145   static char ID;
 146   PhiValuesWrapperPass();
 147
 148   PhiValues &getResult() { return *Result; }
 149   const PhiValues &getResult() const { return *Result; }
 150
 151   bool runOnFunction(Function &F) override;
 152   void releaseMemory() override;
 153   void getAnalysisUsage(AnalysisUsage &AU) const override;
 154 };
 155
 156 } // namespace llvm
 157
 158 #endif