| // Copyright 2013 the V8 project authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef V8_HYDROGEN_GVN_H_ |
| #define V8_HYDROGEN_GVN_H_ |
| |
| #include "src/hydrogen.h" |
| #include "src/hydrogen-instructions.h" |
| #include "src/compiler.h" |
| #include "src/zone.h" |
| |
| namespace v8 { |
| namespace internal { |
| |
| // This class extends GVNFlagSet with additional "special" dynamic side effects, |
| // which can be used to represent side effects that cannot be expressed using |
| // the GVNFlags of an HInstruction. These special side effects are tracked by a |
| // SideEffectsTracker (see below). |
| class SideEffects V8_FINAL { |
| public: |
| static const int kNumberOfSpecials = 64 - kNumberOfFlags; |
| |
| SideEffects() : bits_(0) { |
| ASSERT(kNumberOfFlags + kNumberOfSpecials == sizeof(bits_) * CHAR_BIT); |
| } |
| explicit SideEffects(GVNFlagSet flags) : bits_(flags.ToIntegral()) {} |
| bool IsEmpty() const { return bits_ == 0; } |
| bool ContainsFlag(GVNFlag flag) const { |
| return (bits_ & MaskFlag(flag)) != 0; |
| } |
| bool ContainsSpecial(int special) const { |
| return (bits_ & MaskSpecial(special)) != 0; |
| } |
| bool ContainsAnyOf(SideEffects set) const { return (bits_ & set.bits_) != 0; } |
| void Add(SideEffects set) { bits_ |= set.bits_; } |
| void AddSpecial(int special) { bits_ |= MaskSpecial(special); } |
| void RemoveFlag(GVNFlag flag) { bits_ &= ~MaskFlag(flag); } |
| void RemoveAll() { bits_ = 0; } |
| uint64_t ToIntegral() const { return bits_; } |
| void PrintTo(StringStream* stream) const; |
| |
| private: |
| uint64_t MaskFlag(GVNFlag flag) const { |
| return static_cast<uint64_t>(1) << static_cast<unsigned>(flag); |
| } |
| uint64_t MaskSpecial(int special) const { |
| ASSERT(special >= 0); |
| ASSERT(special < kNumberOfSpecials); |
| return static_cast<uint64_t>(1) << static_cast<unsigned>( |
| special + kNumberOfFlags); |
| } |
| |
| uint64_t bits_; |
| }; |
| |
| |
| // Tracks global variable and inobject field loads/stores in a fine grained |
| // fashion, and represents them using the "special" dynamic side effects of the |
| // SideEffects class (see above). This way unrelated global variable/inobject |
| // field stores don't prevent hoisting and merging of global variable/inobject |
| // field loads. |
| class SideEffectsTracker V8_FINAL BASE_EMBEDDED { |
| public: |
| SideEffectsTracker() : num_global_vars_(0), num_inobject_fields_(0) {} |
| SideEffects ComputeChanges(HInstruction* instr); |
| SideEffects ComputeDependsOn(HInstruction* instr); |
| void PrintSideEffectsTo(StringStream* stream, SideEffects side_effects) const; |
| |
| private: |
| bool ComputeGlobalVar(Unique<Cell> cell, int* index); |
| bool ComputeInobjectField(HObjectAccess access, int* index); |
| |
| static int GlobalVar(int index) { |
| ASSERT(index >= 0); |
| ASSERT(index < kNumberOfGlobalVars); |
| return index; |
| } |
| static int InobjectField(int index) { |
| ASSERT(index >= 0); |
| ASSERT(index < kNumberOfInobjectFields); |
| return index + kNumberOfGlobalVars; |
| } |
| |
| // Track up to four global vars. |
| static const int kNumberOfGlobalVars = 4; |
| Unique<Cell> global_vars_[kNumberOfGlobalVars]; |
| int num_global_vars_; |
| |
| // Track up to n inobject fields. |
| static const int kNumberOfInobjectFields = |
| SideEffects::kNumberOfSpecials - kNumberOfGlobalVars; |
| HObjectAccess inobject_fields_[kNumberOfInobjectFields]; |
| int num_inobject_fields_; |
| }; |
| |
| |
| // Perform common subexpression elimination and loop-invariant code motion. |
| class HGlobalValueNumberingPhase V8_FINAL : public HPhase { |
| public: |
| explicit HGlobalValueNumberingPhase(HGraph* graph); |
| |
| void Run(); |
| |
| private: |
| SideEffects CollectSideEffectsOnPathsToDominatedBlock( |
| HBasicBlock* dominator, |
| HBasicBlock* dominated); |
| void AnalyzeGraph(); |
| void ComputeBlockSideEffects(); |
| void LoopInvariantCodeMotion(); |
| void ProcessLoopBlock(HBasicBlock* block, |
| HBasicBlock* before_loop, |
| SideEffects loop_kills); |
| bool AllowCodeMotion(); |
| bool ShouldMove(HInstruction* instr, HBasicBlock* loop_header); |
| |
| SideEffectsTracker side_effects_tracker_; |
| bool removed_side_effects_; |
| |
| // A map of block IDs to their side effects. |
| ZoneList<SideEffects> block_side_effects_; |
| |
| // A map of loop header block IDs to their loop's side effects. |
| ZoneList<SideEffects> 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_ |