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68 lines
2.5 KiB
68 lines
2.5 KiB
// Copyright 2013 the V8 project authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef V8_HYDROGEN_ENVIRONMENT_LIVENESS_H_
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#define V8_HYDROGEN_ENVIRONMENT_LIVENESS_H_
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#include "src/hydrogen.h"
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namespace v8 {
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namespace internal {
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// Trims live ranges of environment slots by doing explicit liveness analysis.
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// Values in the environment are kept alive by every subsequent LInstruction
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// that is assigned an LEnvironment, which creates register pressure and
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// unnecessary spill slot moves. Therefore it is beneficial to trim the
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// live ranges of environment slots by zapping them with a constant after
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// the last lookup that refers to them.
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// Slots are identified by their index and only affected if whitelisted in
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// HOptimizedGraphBuilder::IsEligibleForEnvironmentLivenessAnalysis().
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class HEnvironmentLivenessAnalysisPhase : public HPhase {
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public:
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explicit HEnvironmentLivenessAnalysisPhase(HGraph* graph);
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void Run();
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private:
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void ZapEnvironmentSlot(int index, HSimulate* simulate);
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void ZapEnvironmentSlotsInSuccessors(HBasicBlock* block, BitVector* live);
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void ZapEnvironmentSlotsForInstruction(HEnvironmentMarker* marker);
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void UpdateLivenessAtBlockEnd(HBasicBlock* block, BitVector* live);
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void UpdateLivenessAtInstruction(HInstruction* instr, BitVector* live);
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#ifdef DEBUG
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bool VerifyClosures(Handle<JSFunction> a, Handle<JSFunction> b);
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#endif
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int block_count_;
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// Largest number of local variables in any environment in the graph
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// (including inlined environments).
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int maximum_environment_size_;
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// Per-block data. All these lists are indexed by block_id.
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ZoneList<BitVector*> live_at_block_start_;
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ZoneList<HSimulate*> first_simulate_;
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ZoneList<BitVector*> first_simulate_invalid_for_index_;
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// List of all HEnvironmentMarker instructions for quick iteration/deletion.
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// It is populated during the first pass over the graph, controlled by
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// |collect_markers_|.
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ZoneList<HEnvironmentMarker*> markers_;
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bool collect_markers_;
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// Keeps track of the last simulate seen, as well as the environment slots
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// for which a new live range has started since (so they must not be zapped
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// in that simulate when the end of another live range of theirs is found).
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HSimulate* last_simulate_;
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BitVector went_live_since_last_simulate_;
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DISALLOW_COPY_AND_ASSIGN(HEnvironmentLivenessAnalysisPhase);
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};
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} } // namespace v8::internal
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#endif /* V8_HYDROGEN_ENVIRONMENT_LIVENESS_H_ */
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