Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 1 | // Copyright 2013 the V8 project authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style license that can be |
| 3 | // found in the LICENSE file. |
| 4 | |
| 5 | #ifndef V8_CRANKSHAFT_HYDROGEN_GVN_H_ |
| 6 | #define V8_CRANKSHAFT_HYDROGEN_GVN_H_ |
| 7 | |
| 8 | #include <iosfwd> |
| 9 | |
| 10 | #include "src/crankshaft/hydrogen.h" |
| 11 | #include "src/crankshaft/hydrogen-instructions.h" |
| 12 | #include "src/zone.h" |
| 13 | |
| 14 | namespace v8 { |
| 15 | namespace internal { |
| 16 | |
| 17 | // This class extends GVNFlagSet with additional "special" dynamic side effects, |
| 18 | // which can be used to represent side effects that cannot be expressed using |
| 19 | // the GVNFlags of an HInstruction. These special side effects are tracked by a |
| 20 | // SideEffectsTracker (see below). |
| 21 | class SideEffects final { |
| 22 | public: |
| 23 | static const int kNumberOfSpecials = 64 - kNumberOfFlags; |
| 24 | |
| 25 | SideEffects() : bits_(0) { |
| 26 | DCHECK(kNumberOfFlags + kNumberOfSpecials == sizeof(bits_) * CHAR_BIT); |
| 27 | } |
| 28 | explicit SideEffects(GVNFlagSet flags) : bits_(flags.ToIntegral()) {} |
| 29 | bool IsEmpty() const { return bits_ == 0; } |
| 30 | bool ContainsFlag(GVNFlag flag) const { |
| 31 | return (bits_ & MaskFlag(flag)) != 0; |
| 32 | } |
| 33 | bool ContainsSpecial(int special) const { |
| 34 | return (bits_ & MaskSpecial(special)) != 0; |
| 35 | } |
| 36 | bool ContainsAnyOf(SideEffects set) const { return (bits_ & set.bits_) != 0; } |
| 37 | void Add(SideEffects set) { bits_ |= set.bits_; } |
| 38 | void AddSpecial(int special) { bits_ |= MaskSpecial(special); } |
| 39 | void RemoveFlag(GVNFlag flag) { bits_ &= ~MaskFlag(flag); } |
| 40 | void RemoveAll() { bits_ = 0; } |
| 41 | uint64_t ToIntegral() const { return bits_; } |
| 42 | |
| 43 | private: |
| 44 | uint64_t MaskFlag(GVNFlag flag) const { |
| 45 | return static_cast<uint64_t>(1) << static_cast<unsigned>(flag); |
| 46 | } |
| 47 | uint64_t MaskSpecial(int special) const { |
| 48 | DCHECK(special >= 0); |
| 49 | DCHECK(special < kNumberOfSpecials); |
| 50 | return static_cast<uint64_t>(1) << static_cast<unsigned>( |
| 51 | special + kNumberOfFlags); |
| 52 | } |
| 53 | |
| 54 | uint64_t bits_; |
| 55 | }; |
| 56 | |
| 57 | |
| 58 | struct TrackedEffects; |
| 59 | |
| 60 | // Tracks global variable and inobject field loads/stores in a fine grained |
| 61 | // fashion, and represents them using the "special" dynamic side effects of the |
| 62 | // SideEffects class (see above). This way unrelated global variable/inobject |
| 63 | // field stores don't prevent hoisting and merging of global variable/inobject |
| 64 | // field loads. |
| 65 | class SideEffectsTracker final BASE_EMBEDDED { |
| 66 | public: |
| 67 | SideEffectsTracker() : num_global_vars_(0), num_inobject_fields_(0) {} |
| 68 | SideEffects ComputeChanges(HInstruction* instr); |
| 69 | SideEffects ComputeDependsOn(HInstruction* instr); |
| 70 | |
| 71 | private: |
| 72 | friend std::ostream& operator<<(std::ostream& os, const TrackedEffects& f); |
| 73 | bool ComputeGlobalVar(Unique<PropertyCell> cell, int* index); |
| 74 | bool ComputeInobjectField(HObjectAccess access, int* index); |
| 75 | |
| 76 | static int GlobalVar(int index) { |
| 77 | DCHECK(index >= 0); |
| 78 | DCHECK(index < kNumberOfGlobalVars); |
| 79 | return index; |
| 80 | } |
| 81 | static int InobjectField(int index) { |
| 82 | DCHECK(index >= 0); |
| 83 | DCHECK(index < kNumberOfInobjectFields); |
| 84 | return index + kNumberOfGlobalVars; |
| 85 | } |
| 86 | |
| 87 | // Track up to four global vars. |
| 88 | static const int kNumberOfGlobalVars = 4; |
| 89 | Unique<PropertyCell> global_vars_[kNumberOfGlobalVars]; |
| 90 | int num_global_vars_; |
| 91 | |
| 92 | // Track up to n inobject fields. |
| 93 | static const int kNumberOfInobjectFields = |
| 94 | SideEffects::kNumberOfSpecials - kNumberOfGlobalVars; |
| 95 | HObjectAccess inobject_fields_[kNumberOfInobjectFields]; |
| 96 | int num_inobject_fields_; |
| 97 | }; |
| 98 | |
| 99 | |
| 100 | // Helper class for printing, because the effects don't know their tracker. |
| 101 | struct TrackedEffects { |
| 102 | TrackedEffects(SideEffectsTracker* t, SideEffects e) |
| 103 | : tracker(t), effects(e) {} |
| 104 | SideEffectsTracker* tracker; |
| 105 | SideEffects effects; |
| 106 | }; |
| 107 | |
| 108 | |
| 109 | std::ostream& operator<<(std::ostream& os, const TrackedEffects& f); |
| 110 | |
| 111 | |
| 112 | // Perform common subexpression elimination and loop-invariant code motion. |
| 113 | class HGlobalValueNumberingPhase final : public HPhase { |
| 114 | public: |
| 115 | explicit HGlobalValueNumberingPhase(HGraph* graph); |
| 116 | |
| 117 | void Run(); |
| 118 | |
| 119 | private: |
| 120 | SideEffects CollectSideEffectsOnPathsToDominatedBlock( |
| 121 | HBasicBlock* dominator, |
| 122 | HBasicBlock* dominated); |
| 123 | void AnalyzeGraph(); |
| 124 | void ComputeBlockSideEffects(); |
| 125 | void LoopInvariantCodeMotion(); |
| 126 | void ProcessLoopBlock(HBasicBlock* block, |
| 127 | HBasicBlock* before_loop, |
| 128 | SideEffects loop_kills); |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 129 | bool ShouldMove(HInstruction* instr, HBasicBlock* loop_header); |
| 130 | TrackedEffects Print(SideEffects side_effects) { |
| 131 | return TrackedEffects(&side_effects_tracker_, side_effects); |
| 132 | } |
| 133 | |
| 134 | SideEffectsTracker side_effects_tracker_; |
| 135 | bool removed_side_effects_; |
| 136 | |
| 137 | // A map of block IDs to their side effects. |
| 138 | ZoneList<SideEffects> block_side_effects_; |
| 139 | |
| 140 | // A map of loop header block IDs to their loop's side effects. |
| 141 | ZoneList<SideEffects> loop_side_effects_; |
| 142 | |
| 143 | // Used when collecting side effects on paths from dominator to |
| 144 | // dominated. |
| 145 | BitVector visited_on_paths_; |
| 146 | |
| 147 | DISALLOW_COPY_AND_ASSIGN(HGlobalValueNumberingPhase); |
| 148 | }; |
| 149 | |
| 150 | } // namespace internal |
| 151 | } // namespace v8 |
| 152 | |
| 153 | #endif // V8_CRANKSHAFT_HYDROGEN_GVN_H_ |