late-escape-analysis-reducer.h

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// Copyright 2022 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
 
#ifndef V8_COMPILER_TURBOSHAFT_LATE_ESCAPE_ANALYSIS_REDUCER_H_
#define V8_COMPILER_TURBOSHAFT_LATE_ESCAPE_ANALYSIS_REDUCER_H_
 
#include "src/compiler/turboshaft/assembler.h"
#include "src/compiler/turboshaft/graph.h"
#include "src/compiler/turboshaft/utils.h"
#include "src/zone/zone-containers.h"
#include "src/zone/zone.h"
 
namespace v8::internal::compiler::turboshaft {
 
// LateEscapeAnalysis removes allocation that have no uses besides the stores
// initializing the object.
 
class LateEscapeAnalysisAnalyzer {
 public:
  LateEscapeAnalysisAnalyzer(Graph& graph, Zone* zone)
      : graph_(graph), phase_zone_(zone), alloc_uses_(zone), allocs_(zone) {}
 
  void Run();
 
 private:
  void RecordAllocateUse(OpIndex alloc, OpIndex use);
 
  void CollectUsesAndAllocations();
  void FindRemovableAllocations();
  bool AllocationIsEscaping(OpIndex alloc);
  bool EscapesThroughUse(OpIndex alloc, OpIndex using_op_idx);
  void MarkToRemove(OpIndex alloc);
 
  Graph& graph_;
  Zone* phase_zone_;
 
  // {alloc_uses_} records all the uses of each AllocateOp.
  ZoneAbslFlatHashMap<OpIndex, ZoneVector<OpIndex>> alloc_uses_;
  // {allocs_} is filled with all of the AllocateOp of the graph, and then
  // iterated upon to determine which allocations can be removed and which
  // cannot.
  ZoneVector<OpIndex> allocs_;
};
 
template <class Next>
class LateEscapeAnalysisReducer : public Next {
 public:
  TURBOSHAFT_REDUCER_BOILERPLATE(LateEscapeAnalysis)
 
  void Analyze() {
    analyzer_.Run();
    Next::Analyze();
  }
 
 private:
  LateEscapeAnalysisAnalyzer analyzer_{Asm().modifiable_input_graph(),
                                       Asm().phase_zone()};
};
 
}  // namespace v8::internal::compiler::turboshaft
 
#endif  // V8_COMPILER_TURBOSHAFT_LATE_ESCAPE_ANALYSIS_REDUCER_H_