tor-browser

The Tor Browser
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ValueNumbering.h (4647B)

      1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
      2 * vim: set ts=8 sts=2 et sw=2 tw=80:
      3 * This Source Code Form is subject to the terms of the Mozilla Public
      4 * License, v. 2.0. If a copy of the MPL was not distributed with this
      5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
      6 
      7 #ifndef jit_ValueNumbering_h
      8 #define jit_ValueNumbering_h
      9 
     10 #include "jit/JitAllocPolicy.h"
     11 #include "js/HashTable.h"
     12 #include "js/Vector.h"
     13 
     14 namespace js {
     15 namespace jit {
     16 
     17 class MDefinition;
     18 class MBasicBlock;
     19 class MIRGraph;
     20 class MPhi;
     21 class MIRGenerator;
     22 class MResumePoint;
     23 
     24 class ValueNumberer {
     25  // Value numbering data.
     26  class VisibleValues {
     27    // Hash policy for ValueSet.
     28    struct ValueHasher {
     29      using Lookup = const MDefinition*;
     30      using Key = MDefinition*;
     31      static HashNumber hash(Lookup ins);
     32      static bool match(Key k, Lookup l);
     33      static void rekey(Key& k, Key newKey);
     34    };
     35 
     36    using ValueSet = HashSet<MDefinition*, ValueHasher, JitAllocPolicy>;
     37 
     38    ValueSet set_;  // Set of visible values
     39 
     40   public:
     41    explicit VisibleValues(TempAllocator& alloc);
     42 
     43    using Ptr = ValueSet::Ptr;
     44    using AddPtr = ValueSet::AddPtr;
     45 
     46    Ptr findLeader(const MDefinition* def) const;
     47    AddPtr findLeaderForAdd(MDefinition* def);
     48    [[nodiscard]] bool add(AddPtr p, MDefinition* def);
     49    void overwrite(AddPtr p, MDefinition* def);
     50    void forget(const MDefinition* def);
     51    void clear();
     52 #ifdef DEBUG
     53    bool has(const MDefinition* def) const;
     54 #endif
     55  };
     56 
     57  using BlockWorklist = Vector<MBasicBlock*, 4, JitAllocPolicy>;
     58  using DefWorklist = Vector<MDefinition*, 4, JitAllocPolicy>;
     59 
     60  const MIRGenerator* const mir_;
     61  MIRGraph& graph_;
     62  VisibleValues values_;           // Numbered values
     63  DefWorklist deadDefs_;           // Worklist for deleting values
     64  BlockWorklist remainingBlocks_;  // Blocks remaining with fewer preds
     65  MDefinition* nextDef_;           // The next definition; don't discard
     66  size_t totalNumVisited_;         // The number of blocks visited
     67  bool rerun_;                     // Should we run another GVN iteration?
     68  bool blocksRemoved_;             // Have any blocks been removed?
     69  bool updateAliasAnalysis_;       // Do we care about AliasAnalysis?
     70  bool dependenciesBroken_;        // Have we broken AliasAnalysis?
     71  bool hasOSRFixups_;              // Have we created any OSR fixup blocks?
     72 
     73  enum ImplicitUseOption { DontSetImplicitUse, SetImplicitUse };
     74  enum class AllowEffectful : bool { No, Yes };
     75 
     76  [[nodiscard]] bool handleUseReleased(MDefinition* def,
     77                                       ImplicitUseOption implicitUseOption);
     78  [[nodiscard]] bool discardDefsRecursively(
     79      MDefinition* def, AllowEffectful allowEffectful = AllowEffectful::No);
     80  [[nodiscard]] bool releaseResumePointOperands(MResumePoint* resume);
     81  [[nodiscard]] bool releaseAndRemovePhiOperands(MPhi* phi);
     82  [[nodiscard]] bool releaseOperands(MDefinition* def);
     83  [[nodiscard]] bool discardDef(
     84      MDefinition* def, AllowEffectful allowEffectful = AllowEffectful::No);
     85  [[nodiscard]] bool processDeadDefs();
     86 
     87  [[nodiscard]] bool fixupOSROnlyLoop(MBasicBlock* block);
     88  [[nodiscard]] bool removePredecessorAndDoDCE(MBasicBlock* block,
     89                                               MBasicBlock* pred,
     90                                               size_t predIndex);
     91  [[nodiscard]] bool removePredecessorAndCleanUp(MBasicBlock* block,
     92                                                 MBasicBlock* pred);
     93 
     94  MDefinition* simplified(MDefinition* def) const;
     95  MDefinition* leader(MDefinition* def);
     96  bool hasLeader(const MPhi* phi, const MBasicBlock* phiBlock) const;
     97  bool loopHasOptimizablePhi(MBasicBlock* header) const;
     98 
     99  [[nodiscard]] bool visitDefinition(MDefinition* def);
    100  [[nodiscard]] bool visitControlInstruction(MBasicBlock* block);
    101  [[nodiscard]] bool visitUnreachableBlock(MBasicBlock* block);
    102  [[nodiscard]] bool visitBlock(MBasicBlock* block);
    103  [[nodiscard]] bool visitDominatorTree(MBasicBlock* root);
    104  [[nodiscard]] bool visitGraph();
    105 
    106  [[nodiscard]] bool insertOSRFixups();
    107  [[nodiscard]] bool cleanupOSRFixups();
    108 
    109 public:
    110  ValueNumberer(const MIRGenerator* mir, MIRGraph& graph);
    111 
    112  enum UpdateAliasAnalysisFlag { DontUpdateAliasAnalysis, UpdateAliasAnalysis };
    113 
    114  // Optimize the graph, performing expression simplification and
    115  // canonicalization, eliminating statically fully-redundant expressions,
    116  // deleting dead instructions, and removing unreachable blocks.
    117  [[nodiscard]] bool run(UpdateAliasAnalysisFlag updateAliasAnalysis);
    118 };
    119 
    120 }  // namespace jit
    121 }  // namespace js
    122 
    123 #endif /* jit_ValueNumbering_h */