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#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();

 private:
  GVNFlagSet CollectSideEffectsOnPathsToDominatedBlock(
      HBasicBlock* dominator,
      HBasicBlock* dominated);
  void AnalyzeGraph();
  void ComputeBlockSideEffects();
  void LoopInvariantCodeMotion();
  void ProcessLoopBlock(HBasicBlock* block,
                        HBasicBlock* before_loop,
                        GVNFlagSet loop_kills);
  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_
