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28 #ifndef V8_HYDROGEN_GVN_H_
29 #define V8_HYDROGEN_GVN_H_
32 #include "hydrogen-instructions.h"
39 // Perform common subexpression elimination and loop-invariant code motion.
40 class HGlobalValueNumberingPhase : public HPhase {
42 explicit HGlobalValueNumberingPhase(HGraph* graph);
46 // Trigger a second analysis pass to further eliminate duplicate values
47 // that could only be discovered by removing side-effect-generating
48 // instructions during the first pass.
49 if (FLAG_smi_only_arrays && removed_side_effects_) {
51 // TODO(danno): Turn this into a fixpoint iteration.
57 GVNFlagSet CollectSideEffectsOnPathsToDominatedBlock(
58 HBasicBlock* dominator,
59 HBasicBlock* dominated);
61 void ComputeBlockSideEffects();
62 void LoopInvariantCodeMotion();
63 void ProcessLoopBlock(HBasicBlock* block,
64 HBasicBlock* before_loop,
65 GVNFlagSet loop_kills,
66 GVNFlagSet* accumulated_first_time_depends,
67 GVNFlagSet* accumulated_first_time_changes);
68 bool AllowCodeMotion();
69 bool ShouldMove(HInstruction* instr, HBasicBlock* loop_header);
71 bool removed_side_effects_;
73 // A map of block IDs to their side effects.
74 ZoneList<GVNFlagSet> block_side_effects_;
76 // A map of loop header block IDs to their loop's side effects.
77 ZoneList<GVNFlagSet> loop_side_effects_;
79 // Used when collecting side effects on paths from dominator to
81 BitVector visited_on_paths_;
83 DISALLOW_COPY_AND_ASSIGN(HGlobalValueNumberingPhase);
87 } } // namespace v8::internal
89 #endif // V8_HYDROGEN_GVN_H_