ValueNumbering.h - mozsearch

Enable keyboard shortcuts

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-

 * vim: set ts=8 sts=2 et sw=2 tw=80:

 * This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef jit_ValueNumbering_h

#define jit_ValueNumbering_h

#include "jit/JitAllocPolicy.h"

#include "js/HashTable.h"

#include "js/Vector.h"

namespace js {

namespace jit {

class MDefinition;

class MBasicBlock;

class MIRGraph;

class MPhi;

class MIRGenerator;

class MResumePoint;

class ValueNumberer {

  // Value numbering data.

  class VisibleValues {

    // Hash policy for ValueSet.

    struct ValueHasher {

      using Lookup = const MDefinition*;

      using Key = MDefinition*;

      static HashNumber hash(Lookup ins);

      static bool match(Key k, Lookup l);

      static void rekey(Key& k, Key newKey);

};

    typedef HashSet<MDefinition*, ValueHasher, JitAllocPolicy> ValueSet;

    ValueSet set_;  // Set of visible values

   public:

    explicit VisibleValues(TempAllocator& alloc);

    using Ptr = ValueSet::Ptr;

    using AddPtr = ValueSet::AddPtr;

    Ptr findLeader(const MDefinition* def) const;

    AddPtr findLeaderForAdd(MDefinition* def);

    [[nodiscard]] bool add(AddPtr p, MDefinition* def);

    void overwrite(AddPtr p, MDefinition* def);

    void forget(const MDefinition* def);

    void clear();

#ifdef DEBUG

    bool has(const MDefinition* def) const;

#endif

};

  typedef Vector<MBasicBlock*, 4, JitAllocPolicy> BlockWorklist;

  typedef Vector<MDefinition*, 4, JitAllocPolicy> DefWorklist;

  MIRGenerator* const mir_;

  MIRGraph& graph_;

  VisibleValues values_;           // Numbered values

  DefWorklist deadDefs_;           // Worklist for deleting values

  BlockWorklist remainingBlocks_;  // Blocks remaining with fewer preds

  MDefinition* nextDef_;           // The next definition; don't discard

  size_t totalNumVisited_;         // The number of blocks visited

  bool rerun_;                     // Should we run another GVN iteration?

  bool blocksRemoved_;             // Have any blocks been removed?

  bool updateAliasAnalysis_;       // Do we care about AliasAnalysis?

  bool dependenciesBroken_;        // Have we broken AliasAnalysis?

  bool hasOSRFixups_;              // Have we created any OSR fixup blocks?

  enum ImplicitUseOption { DontSetImplicitUse, SetImplicitUse };

  enum class AllowEffectful : bool { No, Yes };

  [[nodiscard]] bool handleUseReleased(MDefinition* def,

                                       ImplicitUseOption implicitUseOption);

  [[nodiscard]] bool discardDefsRecursively(

      MDefinition* def, AllowEffectful allowEffectful = AllowEffectful::No);

  [[nodiscard]] bool releaseResumePointOperands(MResumePoint* resume);

  [[nodiscard]] bool releaseAndRemovePhiOperands(MPhi* phi);

  [[nodiscard]] bool releaseOperands(MDefinition* def);

  [[nodiscard]] bool discardDef(

      MDefinition* def, AllowEffectful allowEffectful = AllowEffectful::No);

  [[nodiscard]] bool processDeadDefs();

  [[nodiscard]] bool fixupOSROnlyLoop(MBasicBlock* block);

  [[nodiscard]] bool removePredecessorAndDoDCE(MBasicBlock* block,

                                               MBasicBlock* pred,

                                               size_t predIndex);

  [[nodiscard]] bool removePredecessorAndCleanUp(MBasicBlock* block,

                                                 MBasicBlock* pred);

  MDefinition* simplified(MDefinition* def) const;

  MDefinition* leader(MDefinition* def);

  bool hasLeader(const MPhi* phi, const MBasicBlock* phiBlock) const;

  bool loopHasOptimizablePhi(MBasicBlock* header) const;

  [[nodiscard]] bool visitDefinition(MDefinition* def);

  [[nodiscard]] bool visitControlInstruction(MBasicBlock* block);

  [[nodiscard]] bool visitUnreachableBlock(MBasicBlock* block);

  [[nodiscard]] bool visitBlock(MBasicBlock* block);

  [[nodiscard]] bool visitDominatorTree(MBasicBlock* root);

  [[nodiscard]] bool visitGraph();

  [[nodiscard]] bool insertOSRFixups();

  [[nodiscard]] bool cleanupOSRFixups();

 public:

  ValueNumberer(MIRGenerator* mir, MIRGraph& graph);

  enum UpdateAliasAnalysisFlag { DontUpdateAliasAnalysis, UpdateAliasAnalysis };

  // Optimize the graph, performing expression simplification and

  // canonicalization, eliminating statically fully-redundant expressions,

  // deleting dead instructions, and removing unreachable blocks.

  [[nodiscard]] bool run(UpdateAliasAnalysisFlag updateAliasAnalysis);

};

}  // namespace jit

}  // namespace js

#endif /* jit_ValueNumbering_h */