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// Copyright 2013 the V8 project authors. All rights reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following
// disclaimer in the documentation and/or other materials provided
// with the distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived
// from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#ifndef V8_HYDROGEN_ENVIRONMENT_LIVENESS_H_
#define V8_HYDROGEN_ENVIRONMENT_LIVENESS_H_
#include "hydrogen.h"
namespace v8 {
namespace internal {
// Trims live ranges of environment slots by doing explicit liveness analysis.
// Values in the environment are kept alive by every subsequent LInstruction
// that is assigned an LEnvironment, which creates register pressure and
// unnecessary spill slot moves. Therefore it is beneficial to trim the
// live ranges of environment slots by zapping them with a constant after
// the last lookup that refers to them.
// Slots are identified by their index and only affected if whitelisted in
// HOptimizedGraphBuilder::IsEligibleForEnvironmentLivenessAnalysis().
class EnvironmentSlotLivenessAnalyzer {
public:
explicit EnvironmentSlotLivenessAnalyzer(HGraph* graph);
void AnalyzeAndTrim();
private:
void ZapEnvironmentSlot(int index, HSimulate* simulate);
void ZapEnvironmentSlotsInSuccessors(HBasicBlock* block, BitVector* live);
void ZapEnvironmentSlotsForInstruction(HEnvironmentMarker* marker);
void UpdateLivenessAtBlockEnd(HBasicBlock* block, BitVector* live);
void UpdateLivenessAtInstruction(HInstruction* instr, BitVector* live);
Zone* zone() { return &zone_; }
HGraph* graph_;
// Use a dedicated Zone for this phase, with a ZoneScope to ensure it
// gets freed.
Zone zone_;
ZoneScope zone_scope_;
int block_count_;
// Largest number of local variables in any environment in the graph
// (including inlined environments).
int maximum_environment_size_;
// Per-block data. All these lists are indexed by block_id.
ZoneList<BitVector*>* live_at_block_start_;
ZoneList<HSimulate*>* first_simulate_;
ZoneList<BitVector*>* first_simulate_invalid_for_index_;
// List of all HEnvironmentMarker instructions for quick iteration/deletion.
// It is populated during the first pass over the graph, controlled by
// |collect_markers_|.
ZoneList<HEnvironmentMarker*>* markers_;
bool collect_markers_;
// Keeps track of the last simulate seen, as well as the environment slots
// for which a new live range has started since (so they must not be zapped
// in that simulate when the end of another live range of theirs is found).
HSimulate* last_simulate_;
BitVector* went_live_since_last_simulate_;
};
} } // namespace v8::internal
#endif /* V8_HYDROGEN_ENVIRONMENT_LIVENESS_H_ */
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