Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 1 | // Copyright 2014 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 | #include "src/base/adapters.h" |
| 6 | #include "src/compiler/js-graph.h" |
| 7 | #include "src/compiler/liveness-analyzer.h" |
| 8 | #include "src/compiler/node.h" |
| 9 | #include "src/compiler/node-matchers.h" |
| 10 | #include "src/compiler/state-values-utils.h" |
| 11 | |
| 12 | namespace v8 { |
| 13 | namespace internal { |
| 14 | namespace compiler { |
| 15 | |
| 16 | |
| 17 | LivenessAnalyzer::LivenessAnalyzer(size_t local_count, Zone* zone) |
| 18 | : zone_(zone), blocks_(zone), local_count_(local_count), queue_(zone) {} |
| 19 | |
| 20 | |
| 21 | void LivenessAnalyzer::Print(std::ostream& os) { |
| 22 | for (auto block : blocks_) { |
| 23 | block->Print(os); |
| 24 | os << std::endl; |
| 25 | } |
| 26 | } |
| 27 | |
| 28 | |
| 29 | LivenessAnalyzerBlock* LivenessAnalyzer::NewBlock() { |
| 30 | LivenessAnalyzerBlock* result = |
| 31 | new (zone()->New(sizeof(LivenessAnalyzerBlock))) |
| 32 | LivenessAnalyzerBlock(blocks_.size(), local_count_, zone()); |
| 33 | blocks_.push_back(result); |
| 34 | return result; |
| 35 | } |
| 36 | |
| 37 | |
| 38 | LivenessAnalyzerBlock* LivenessAnalyzer::NewBlock( |
| 39 | LivenessAnalyzerBlock* predecessor) { |
| 40 | LivenessAnalyzerBlock* result = NewBlock(); |
| 41 | result->AddPredecessor(predecessor); |
| 42 | return result; |
| 43 | } |
| 44 | |
| 45 | |
| 46 | void LivenessAnalyzer::Queue(LivenessAnalyzerBlock* block) { |
| 47 | if (!block->IsQueued()) { |
| 48 | block->SetQueued(); |
| 49 | queue_.push(block); |
| 50 | } |
| 51 | } |
| 52 | |
| 53 | |
| 54 | void LivenessAnalyzer::Run(NonLiveFrameStateSlotReplacer* replacer) { |
| 55 | if (local_count_ == 0) { |
| 56 | // No local variables => nothing to do. |
| 57 | return; |
| 58 | } |
| 59 | |
| 60 | // Put all blocks into the queue. |
| 61 | DCHECK(queue_.empty()); |
| 62 | for (auto block : blocks_) { |
| 63 | Queue(block); |
| 64 | } |
| 65 | |
| 66 | // Compute the fix-point. |
| 67 | BitVector working_area(static_cast<int>(local_count_), zone_); |
| 68 | while (!queue_.empty()) { |
| 69 | LivenessAnalyzerBlock* block = queue_.front(); |
| 70 | queue_.pop(); |
| 71 | block->Process(&working_area, nullptr); |
| 72 | |
| 73 | for (auto i = block->pred_begin(); i != block->pred_end(); i++) { |
| 74 | if ((*i)->UpdateLive(&working_area)) { |
| 75 | Queue(*i); |
| 76 | } |
| 77 | } |
| 78 | } |
| 79 | |
| 80 | // Update the frame states according to the liveness. |
| 81 | for (auto block : blocks_) { |
| 82 | block->Process(&working_area, replacer); |
| 83 | } |
| 84 | } |
| 85 | |
| 86 | LivenessAnalyzerBlock::LivenessAnalyzerBlock(size_t id, size_t local_count, |
| 87 | Zone* zone) |
| 88 | : entries_(zone), |
| 89 | predecessors_(zone), |
| 90 | live_(local_count == 0 ? 1 : static_cast<int>(local_count), zone), |
| 91 | queued_(false), |
| 92 | id_(id) {} |
| 93 | |
| 94 | void LivenessAnalyzerBlock::Process(BitVector* result, |
| 95 | NonLiveFrameStateSlotReplacer* replacer) { |
| 96 | queued_ = false; |
| 97 | |
| 98 | // Copy the bitvector to the target bit vector. |
| 99 | result->CopyFrom(live_); |
| 100 | |
| 101 | for (auto entry : base::Reversed(entries_)) { |
| 102 | switch (entry.kind()) { |
| 103 | case Entry::kLookup: |
| 104 | result->Add(entry.var()); |
| 105 | break; |
| 106 | case Entry::kBind: |
| 107 | result->Remove(entry.var()); |
| 108 | break; |
| 109 | case Entry::kCheckpoint: |
| 110 | if (replacer != nullptr) { |
| 111 | replacer->ClearNonLiveFrameStateSlots(entry.node(), result); |
| 112 | } |
| 113 | break; |
| 114 | } |
| 115 | } |
| 116 | } |
| 117 | |
| 118 | |
| 119 | bool LivenessAnalyzerBlock::UpdateLive(BitVector* working_area) { |
| 120 | return live_.UnionIsChanged(*working_area); |
| 121 | } |
| 122 | |
| 123 | |
| 124 | void NonLiveFrameStateSlotReplacer::ClearNonLiveFrameStateSlots( |
| 125 | Node* frame_state, BitVector* liveness) { |
| 126 | DCHECK_EQ(frame_state->opcode(), IrOpcode::kFrameState); |
| 127 | Node* locals_state = frame_state->InputAt(1); |
| 128 | DCHECK_EQ(locals_state->opcode(), IrOpcode::kStateValues); |
| 129 | int count = static_cast<int>(StateValuesAccess(locals_state).size()); |
| 130 | DCHECK_EQ(count == 0 ? 1 : count, liveness->length()); |
| 131 | for (int i = 0; i < count; i++) { |
| 132 | bool live = liveness->Contains(i) || permanently_live_.Contains(i); |
| 133 | if (!live || locals_state->InputAt(i) != replacement_node_) { |
| 134 | Node* new_values = ClearNonLiveStateValues(locals_state, liveness); |
| 135 | frame_state->ReplaceInput(1, new_values); |
| 136 | break; |
| 137 | } |
| 138 | } |
| 139 | } |
| 140 | |
| 141 | |
| 142 | Node* NonLiveFrameStateSlotReplacer::ClearNonLiveStateValues( |
| 143 | Node* values, BitVector* liveness) { |
| 144 | DCHECK(inputs_buffer_.empty()); |
| 145 | for (StateValuesAccess::TypedNode node : StateValuesAccess(values)) { |
| 146 | // Index of the next variable is its furure index in the inputs buffer, |
| 147 | // i.e., the buffer's size. |
| 148 | int var = static_cast<int>(inputs_buffer_.size()); |
| 149 | bool live = liveness->Contains(var) || permanently_live_.Contains(var); |
| 150 | inputs_buffer_.push_back(live ? node.node : replacement_node_); |
| 151 | } |
| 152 | Node* result = state_values_cache()->GetNodeForValues( |
| 153 | inputs_buffer_.empty() ? nullptr : &(inputs_buffer_.front()), |
| 154 | inputs_buffer_.size()); |
| 155 | inputs_buffer_.clear(); |
| 156 | return result; |
| 157 | } |
| 158 | |
| 159 | |
| 160 | void LivenessAnalyzerBlock::Print(std::ostream& os) { |
| 161 | os << "Block " << id(); |
| 162 | bool first = true; |
| 163 | for (LivenessAnalyzerBlock* pred : predecessors_) { |
| 164 | if (!first) { |
| 165 | os << ", "; |
| 166 | } else { |
| 167 | os << "; predecessors: "; |
| 168 | first = false; |
| 169 | } |
| 170 | os << pred->id(); |
| 171 | } |
| 172 | os << std::endl; |
| 173 | |
| 174 | for (auto entry : entries_) { |
| 175 | os << " "; |
| 176 | switch (entry.kind()) { |
| 177 | case Entry::kLookup: |
| 178 | os << "- Lookup " << entry.var() << std::endl; |
| 179 | break; |
| 180 | case Entry::kBind: |
| 181 | os << "- Bind " << entry.var() << std::endl; |
| 182 | break; |
| 183 | case Entry::kCheckpoint: |
| 184 | os << "- Checkpoint " << entry.node()->id() << std::endl; |
| 185 | break; |
| 186 | } |
| 187 | } |
| 188 | |
| 189 | if (live_.length() > 0) { |
| 190 | os << " Live set: "; |
| 191 | for (int i = 0; i < live_.length(); i++) { |
| 192 | os << (live_.Contains(i) ? "L" : "."); |
| 193 | } |
| 194 | os << std::endl; |
| 195 | } |
| 196 | } |
| 197 | |
| 198 | } // namespace compiler |
| 199 | } // namespace internal |
| 200 | } // namespace v8 |