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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_GVN_H_
#define V8_HYDROGEN_GVN_H_
#include "hydrogen.h"
#include "hydrogen-instructions.h"
#include "compiler.h"
#include "zone.h"
namespace v8 {
namespace internal {
// Perform common subexpression elimination and loop-invariant code motion.
class HGlobalValueNumberingPhase : public HPhase {
public:
explicit HGlobalValueNumberingPhase(HGraph* graph);
void Run() {
Analyze();
// Trigger a second analysis pass to further eliminate duplicate values
// that could only be discovered by removing side-effect-generating
// instructions during the first pass.
if (FLAG_smi_only_arrays && removed_side_effects_) {
Analyze();
ASSERT(!removed_side_effects_);
}
}
private:
void Analyze();
GVNFlagSet CollectSideEffectsOnPathsToDominatedBlock(
HBasicBlock* dominator,
HBasicBlock* dominated);
void AnalyzeGraph();
void ComputeBlockSideEffects();
void LoopInvariantCodeMotion();
void ProcessLoopBlock(HBasicBlock* block,
HBasicBlock* before_loop,
GVNFlagSet loop_kills,
GVNFlagSet* accumulated_first_time_depends,
GVNFlagSet* accumulated_first_time_changes);
bool AllowCodeMotion();
bool ShouldMove(HInstruction* instr, HBasicBlock* loop_header);
bool removed_side_effects_;
// A map of block IDs to their side effects.
ZoneList<GVNFlagSet> block_side_effects_;
// A map of loop header block IDs to their loop's side effects.
ZoneList<GVNFlagSet> loop_side_effects_;
// Used when collecting side effects on paths from dominator to
// dominated.
BitVector visited_on_paths_;
DISALLOW_COPY_AND_ASSIGN(HGlobalValueNumberingPhase);
};
} } // namespace v8::internal
#endif // V8_HYDROGEN_GVN_H_
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