Nicolas Geoffray | 804d093 | 2014-05-02 08:46:00 +0100 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2014 The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | #ifndef ART_COMPILER_OPTIMIZING_SSA_LIVENESS_ANALYSIS_H_ |
| 18 | #define ART_COMPILER_OPTIMIZING_SSA_LIVENESS_ANALYSIS_H_ |
| 19 | |
| 20 | #include "nodes.h" |
| 21 | |
| 22 | namespace art { |
| 23 | |
| 24 | class BlockInfo : public ArenaObject { |
| 25 | public: |
| 26 | BlockInfo(ArenaAllocator* allocator, const HBasicBlock& block, size_t number_of_ssa_values) |
| 27 | : block_(block), |
| 28 | live_in_(allocator, number_of_ssa_values, false), |
| 29 | live_out_(allocator, number_of_ssa_values, false), |
| 30 | kill_(allocator, number_of_ssa_values, false) { |
| 31 | live_in_.ClearAllBits(); |
| 32 | live_out_.ClearAllBits(); |
| 33 | kill_.ClearAllBits(); |
| 34 | } |
| 35 | |
| 36 | private: |
| 37 | const HBasicBlock& block_; |
| 38 | ArenaBitVector live_in_; |
| 39 | ArenaBitVector live_out_; |
| 40 | ArenaBitVector kill_; |
| 41 | |
| 42 | friend class SsaLivenessAnalysis; |
| 43 | |
| 44 | DISALLOW_COPY_AND_ASSIGN(BlockInfo); |
| 45 | }; |
| 46 | |
Nicolas Geoffray | ddb311f | 2014-05-16 09:28:54 +0100 | [diff] [blame] | 47 | /** |
| 48 | * A live range contains the start and end of a range where an instruction |
| 49 | * is live. |
| 50 | */ |
| 51 | class LiveRange : public ValueObject { |
| 52 | public: |
| 53 | LiveRange(size_t start, size_t end) : start_(start), end_(end) { |
| 54 | DCHECK_LT(start, end); |
| 55 | } |
| 56 | |
| 57 | size_t GetStart() const { return start_; } |
| 58 | size_t GetEnd() const { return end_; } |
| 59 | |
| 60 | private: |
| 61 | size_t start_; |
| 62 | size_t end_; |
| 63 | }; |
| 64 | |
| 65 | static constexpr int kDefaultNumberOfRanges = 3; |
| 66 | |
| 67 | /** |
| 68 | * An interval is a list of disjoint live ranges where an instruction is live. |
| 69 | * Each instruction that has uses gets an interval. |
| 70 | */ |
| 71 | class LiveInterval : public ArenaObject { |
| 72 | public: |
| 73 | explicit LiveInterval(ArenaAllocator* allocator) : ranges_(allocator, kDefaultNumberOfRanges) {} |
| 74 | |
| 75 | void AddUse(HInstruction* instruction) { |
| 76 | size_t position = instruction->GetLifetimePosition(); |
| 77 | size_t start_block_position = instruction->GetBlock()->GetLifetimeStart(); |
| 78 | size_t end_block_position = instruction->GetBlock()->GetLifetimeEnd(); |
| 79 | if (ranges_.IsEmpty()) { |
| 80 | // First time we see a use of that interval. |
| 81 | ranges_.Add(LiveRange(start_block_position, position)); |
| 82 | } else if (ranges_.Peek().GetStart() == start_block_position) { |
| 83 | // There is a use later in the same block. |
| 84 | DCHECK_LE(position, ranges_.Peek().GetEnd()); |
| 85 | } else if (ranges_.Peek().GetStart() == end_block_position + 1) { |
| 86 | // Last use is in a following block. |
| 87 | LiveRange existing = ranges_.Pop(); |
| 88 | ranges_.Add(LiveRange(start_block_position, existing.GetEnd())); |
| 89 | } else { |
| 90 | // There is a hole in the interval. Create a new range. |
| 91 | ranges_.Add(LiveRange(start_block_position, position)); |
| 92 | } |
| 93 | } |
| 94 | |
| 95 | void AddRange(size_t start, size_t end) { |
| 96 | if (ranges_.IsEmpty()) { |
| 97 | ranges_.Add(LiveRange(start, end)); |
| 98 | } else if (ranges_.Peek().GetStart() == end + 1) { |
| 99 | // There is a use in the following block. |
| 100 | LiveRange existing = ranges_.Pop(); |
| 101 | ranges_.Add(LiveRange(start, existing.GetEnd())); |
| 102 | } else { |
| 103 | // There is a hole in the interval. Create a new range. |
| 104 | ranges_.Add(LiveRange(start, end)); |
| 105 | } |
| 106 | } |
| 107 | |
| 108 | void AddLoopRange(size_t start, size_t end) { |
| 109 | DCHECK(!ranges_.IsEmpty()); |
| 110 | while (!ranges_.IsEmpty() && ranges_.Peek().GetEnd() < end) { |
| 111 | DCHECK_LE(start, ranges_.Peek().GetStart()); |
| 112 | ranges_.Pop(); |
| 113 | } |
| 114 | if (ranges_.IsEmpty()) { |
| 115 | // Uses are only in the loop. |
| 116 | ranges_.Add(LiveRange(start, end)); |
| 117 | } else { |
| 118 | // There are uses after the loop. |
| 119 | LiveRange range = ranges_.Pop(); |
| 120 | ranges_.Add(LiveRange(start, range.GetEnd())); |
| 121 | } |
| 122 | } |
| 123 | |
| 124 | void SetFrom(size_t from) { |
| 125 | DCHECK(!ranges_.IsEmpty()); |
| 126 | LiveRange existing = ranges_.Pop(); |
| 127 | ranges_.Add(LiveRange(from, existing.GetEnd())); |
| 128 | } |
| 129 | |
| 130 | const GrowableArray<LiveRange>& GetRanges() const { return ranges_; } |
| 131 | |
| 132 | private: |
| 133 | GrowableArray<LiveRange> ranges_; |
| 134 | |
| 135 | DISALLOW_COPY_AND_ASSIGN(LiveInterval); |
| 136 | }; |
| 137 | |
Nicolas Geoffray | 804d093 | 2014-05-02 08:46:00 +0100 | [diff] [blame] | 138 | class SsaLivenessAnalysis : public ValueObject { |
| 139 | public: |
| 140 | explicit SsaLivenessAnalysis(const HGraph& graph) |
| 141 | : graph_(graph), |
Nicolas Geoffray | 0d3f578 | 2014-05-14 09:43:38 +0100 | [diff] [blame] | 142 | linear_post_order_(graph.GetArena(), graph.GetBlocks().Size()), |
Nicolas Geoffray | 804d093 | 2014-05-02 08:46:00 +0100 | [diff] [blame] | 143 | block_infos_(graph.GetArena(), graph.GetBlocks().Size()), |
Nicolas Geoffray | ddb311f | 2014-05-16 09:28:54 +0100 | [diff] [blame] | 144 | instructions_from_ssa_index_(graph.GetArena(), 0), |
Nicolas Geoffray | 804d093 | 2014-05-02 08:46:00 +0100 | [diff] [blame] | 145 | number_of_ssa_values_(0) { |
| 146 | block_infos_.SetSize(graph.GetBlocks().Size()); |
| 147 | } |
| 148 | |
| 149 | void Analyze(); |
| 150 | |
| 151 | BitVector* GetLiveInSet(const HBasicBlock& block) const { |
| 152 | return &block_infos_.Get(block.GetBlockId())->live_in_; |
| 153 | } |
| 154 | |
| 155 | BitVector* GetLiveOutSet(const HBasicBlock& block) const { |
| 156 | return &block_infos_.Get(block.GetBlockId())->live_out_; |
| 157 | } |
| 158 | |
| 159 | BitVector* GetKillSet(const HBasicBlock& block) const { |
| 160 | return &block_infos_.Get(block.GetBlockId())->kill_; |
| 161 | } |
| 162 | |
Nicolas Geoffray | 0d3f578 | 2014-05-14 09:43:38 +0100 | [diff] [blame] | 163 | const GrowableArray<HBasicBlock*>& GetLinearPostOrder() const { |
| 164 | return linear_post_order_; |
| 165 | } |
| 166 | |
Nicolas Geoffray | ddb311f | 2014-05-16 09:28:54 +0100 | [diff] [blame] | 167 | HInstruction* GetInstructionFromSsaIndex(size_t index) { |
| 168 | return instructions_from_ssa_index_.Get(index); |
| 169 | } |
| 170 | |
Nicolas Geoffray | 804d093 | 2014-05-02 08:46:00 +0100 | [diff] [blame] | 171 | private: |
Nicolas Geoffray | 0d3f578 | 2014-05-14 09:43:38 +0100 | [diff] [blame] | 172 | // Linearize the graph so that: |
| 173 | // (1): a block is always after its dominator, |
| 174 | // (2): blocks of loops are contiguous. |
| 175 | // This creates a natural and efficient ordering when visualizing live ranges. |
| 176 | void LinearizeGraph(); |
| 177 | |
Nicolas Geoffray | ddb311f | 2014-05-16 09:28:54 +0100 | [diff] [blame] | 178 | // Give an SSA number to each instruction that defines a value used by another instruction, |
| 179 | // and setup the lifetime information of each instruction and block. |
Nicolas Geoffray | 804d093 | 2014-05-02 08:46:00 +0100 | [diff] [blame] | 180 | void NumberInstructions(); |
| 181 | |
Nicolas Geoffray | ddb311f | 2014-05-16 09:28:54 +0100 | [diff] [blame] | 182 | // Compute live ranges of instructions, as well as live_in, live_out and kill sets. |
| 183 | void ComputeLiveness(); |
Nicolas Geoffray | 804d093 | 2014-05-02 08:46:00 +0100 | [diff] [blame] | 184 | |
Nicolas Geoffray | ddb311f | 2014-05-16 09:28:54 +0100 | [diff] [blame] | 185 | // Compute the live ranges of instructions, as well as the initial live_in, live_out and |
| 186 | // kill sets, that do not take into account backward branches. |
| 187 | void ComputeLiveRanges(); |
Nicolas Geoffray | 804d093 | 2014-05-02 08:46:00 +0100 | [diff] [blame] | 188 | |
| 189 | // After computing the initial sets, this method does a fixed point |
| 190 | // calculation over the live_in and live_out set to take into account |
| 191 | // backwards branches. |
| 192 | void ComputeLiveInAndLiveOutSets(); |
| 193 | |
| 194 | // Update the live_in set of the block and returns whether it has changed. |
| 195 | bool UpdateLiveIn(const HBasicBlock& block); |
| 196 | |
| 197 | // Update the live_out set of the block and returns whether it has changed. |
| 198 | bool UpdateLiveOut(const HBasicBlock& block); |
| 199 | |
| 200 | const HGraph& graph_; |
Nicolas Geoffray | 0d3f578 | 2014-05-14 09:43:38 +0100 | [diff] [blame] | 201 | GrowableArray<HBasicBlock*> linear_post_order_; |
Nicolas Geoffray | 804d093 | 2014-05-02 08:46:00 +0100 | [diff] [blame] | 202 | GrowableArray<BlockInfo*> block_infos_; |
Nicolas Geoffray | ddb311f | 2014-05-16 09:28:54 +0100 | [diff] [blame] | 203 | GrowableArray<HInstruction*> instructions_from_ssa_index_; |
Nicolas Geoffray | 804d093 | 2014-05-02 08:46:00 +0100 | [diff] [blame] | 204 | size_t number_of_ssa_values_; |
| 205 | |
| 206 | DISALLOW_COPY_AND_ASSIGN(SsaLivenessAnalysis); |
| 207 | }; |
| 208 | |
| 209 | } // namespace art |
| 210 | |
| 211 | #endif // ART_COMPILER_OPTIMIZING_SSA_LIVENESS_ANALYSIS_H_ |