Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2016 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 | #include "register_allocator_graph_color.h" |
| 18 | |
| 19 | #include "code_generator.h" |
Aart Bik | 9620230 | 2016-10-04 17:33:56 -0700 | [diff] [blame] | 20 | #include "linear_order.h" |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 21 | #include "register_allocation_resolver.h" |
| 22 | #include "ssa_liveness_analysis.h" |
| 23 | #include "thread-inl.h" |
| 24 | |
| 25 | namespace art { |
| 26 | |
| 27 | // Highest number of registers that we support for any platform. This can be used for std::bitset, |
| 28 | // for example, which needs to know its size at compile time. |
| 29 | static constexpr size_t kMaxNumRegs = 32; |
| 30 | |
| 31 | // The maximum number of graph coloring attempts before triggering a DCHECK. |
| 32 | // This is meant to catch changes to the graph coloring algorithm that undermine its forward |
| 33 | // progress guarantees. Forward progress for the algorithm means splitting live intervals on |
| 34 | // every graph coloring attempt so that eventually the interference graph will be sparse enough |
| 35 | // to color. The main threat to forward progress is trying to split short intervals which cannot be |
| 36 | // split further; this could cause infinite looping because the interference graph would never |
| 37 | // change. This is avoided by prioritizing short intervals before long ones, so that long |
| 38 | // intervals are split when coloring fails. |
| 39 | static constexpr size_t kMaxGraphColoringAttemptsDebug = 100; |
| 40 | |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 41 | // We always want to avoid spilling inside loops. |
| 42 | static constexpr size_t kLoopSpillWeightMultiplier = 10; |
| 43 | |
| 44 | // If we avoid moves in single jump blocks, we can avoid jumps to jumps. |
| 45 | static constexpr size_t kSingleJumpBlockWeightMultiplier = 2; |
| 46 | |
| 47 | // We avoid moves in blocks that dominate the exit block, since these blocks will |
| 48 | // be executed on every path through the method. |
| 49 | static constexpr size_t kDominatesExitBlockWeightMultiplier = 2; |
| 50 | |
| 51 | enum class CoalesceKind { |
| 52 | kAdjacentSibling, // Prevents moves at interval split points. |
| 53 | kFixedOutputSibling, // Prevents moves from a fixed output location. |
| 54 | kFixedInput, // Prevents moves into a fixed input location. |
| 55 | kNonlinearControlFlow, // Prevents moves between blocks. |
| 56 | kPhi, // Prevents phi resolution moves. |
| 57 | kFirstInput, // Prevents a single input move. |
| 58 | kAnyInput, // May lead to better instruction selection / smaller encodings. |
| 59 | }; |
| 60 | |
| 61 | std::ostream& operator<<(std::ostream& os, const CoalesceKind& kind) { |
| 62 | return os << static_cast<typename std::underlying_type<CoalesceKind>::type>(kind); |
| 63 | } |
| 64 | |
| 65 | static size_t LoopDepthAt(HBasicBlock* block) { |
| 66 | HLoopInformation* loop_info = block->GetLoopInformation(); |
| 67 | size_t depth = 0; |
| 68 | while (loop_info != nullptr) { |
| 69 | ++depth; |
| 70 | loop_info = loop_info->GetPreHeader()->GetLoopInformation(); |
| 71 | } |
| 72 | return depth; |
| 73 | } |
| 74 | |
| 75 | // Return the runtime cost of inserting a move instruction at the specified location. |
| 76 | static size_t CostForMoveAt(size_t position, const SsaLivenessAnalysis& liveness) { |
| 77 | HBasicBlock* block = liveness.GetBlockFromPosition(position / 2); |
| 78 | DCHECK(block != nullptr); |
| 79 | size_t cost = 1; |
| 80 | if (block->IsSingleJump()) { |
| 81 | cost *= kSingleJumpBlockWeightMultiplier; |
| 82 | } |
| 83 | if (block->Dominates(block->GetGraph()->GetExitBlock())) { |
| 84 | cost *= kDominatesExitBlockWeightMultiplier; |
| 85 | } |
| 86 | for (size_t loop_depth = LoopDepthAt(block); loop_depth > 0; --loop_depth) { |
| 87 | cost *= kLoopSpillWeightMultiplier; |
| 88 | } |
| 89 | return cost; |
| 90 | } |
| 91 | |
| 92 | // In general, we estimate coalesce priority by whether it will definitely avoid a move, |
| 93 | // and by how likely it is to create an interference graph that's harder to color. |
| 94 | static size_t ComputeCoalescePriority(CoalesceKind kind, |
| 95 | size_t position, |
| 96 | const SsaLivenessAnalysis& liveness) { |
| 97 | if (kind == CoalesceKind::kAnyInput) { |
| 98 | // This type of coalescing can affect instruction selection, but not moves, so we |
| 99 | // give it the lowest priority. |
| 100 | return 0; |
| 101 | } else { |
| 102 | return CostForMoveAt(position, liveness); |
| 103 | } |
| 104 | } |
| 105 | |
| 106 | enum class CoalesceStage { |
| 107 | kWorklist, // Currently in the iterative coalescing worklist. |
| 108 | kActive, // Not in a worklist, but could be considered again during iterative coalescing. |
| 109 | kInactive, // No longer considered until last-chance coalescing. |
| 110 | kDefunct, // Either the two nodes interfere, or have already been coalesced. |
| 111 | }; |
| 112 | |
| 113 | std::ostream& operator<<(std::ostream& os, const CoalesceStage& stage) { |
| 114 | return os << static_cast<typename std::underlying_type<CoalesceStage>::type>(stage); |
| 115 | } |
| 116 | |
| 117 | // Represents a coalesce opportunity between two nodes. |
| 118 | struct CoalesceOpportunity : public ArenaObject<kArenaAllocRegisterAllocator> { |
| 119 | CoalesceOpportunity(InterferenceNode* a, |
| 120 | InterferenceNode* b, |
| 121 | CoalesceKind kind, |
| 122 | size_t position, |
| 123 | const SsaLivenessAnalysis& liveness) |
| 124 | : node_a(a), |
| 125 | node_b(b), |
| 126 | stage(CoalesceStage::kWorklist), |
| 127 | priority(ComputeCoalescePriority(kind, position, liveness)) {} |
| 128 | |
| 129 | // Compare two coalesce opportunities based on their priority. |
| 130 | // Return true if lhs has a lower priority than that of rhs. |
| 131 | static bool CmpPriority(const CoalesceOpportunity* lhs, |
| 132 | const CoalesceOpportunity* rhs) { |
| 133 | return lhs->priority < rhs->priority; |
| 134 | } |
| 135 | |
| 136 | InterferenceNode* const node_a; |
| 137 | InterferenceNode* const node_b; |
| 138 | |
| 139 | // The current stage of this coalesce opportunity, indicating whether it is in a worklist, |
| 140 | // and whether it should still be considered. |
| 141 | CoalesceStage stage; |
| 142 | |
| 143 | // The priority of this coalesce opportunity, based on heuristics. |
| 144 | const size_t priority; |
| 145 | }; |
| 146 | |
| 147 | enum class NodeStage { |
| 148 | kInitial, // Uninitialized. |
| 149 | kPrecolored, // Marks fixed nodes. |
| 150 | kSafepoint, // Marks safepoint nodes. |
| 151 | kPrunable, // Marks uncolored nodes in the interference graph. |
| 152 | kSimplifyWorklist, // Marks non-move-related nodes with degree less than the number of registers. |
| 153 | kFreezeWorklist, // Marks move-related nodes with degree less than the number of registers. |
| 154 | kSpillWorklist, // Marks nodes with degree greater or equal to the number of registers. |
| 155 | kPruned // Marks nodes already pruned from the interference graph. |
| 156 | }; |
| 157 | |
| 158 | std::ostream& operator<<(std::ostream& os, const NodeStage& stage) { |
| 159 | return os << static_cast<typename std::underlying_type<NodeStage>::type>(stage); |
| 160 | } |
| 161 | |
| 162 | // Returns the estimated cost of spilling a particular live interval. |
| 163 | static float ComputeSpillWeight(LiveInterval* interval, const SsaLivenessAnalysis& liveness) { |
| 164 | if (interval->HasRegister()) { |
| 165 | // Intervals with a fixed register cannot be spilled. |
| 166 | return std::numeric_limits<float>::min(); |
| 167 | } |
| 168 | |
| 169 | size_t length = interval->GetLength(); |
| 170 | if (length == 1) { |
| 171 | // Tiny intervals should have maximum priority, since they cannot be split any further. |
| 172 | return std::numeric_limits<float>::max(); |
| 173 | } |
| 174 | |
| 175 | size_t use_weight = 0; |
| 176 | if (interval->GetDefinedBy() != nullptr && interval->DefinitionRequiresRegister()) { |
| 177 | // Cost for spilling at a register definition point. |
| 178 | use_weight += CostForMoveAt(interval->GetStart() + 1, liveness); |
| 179 | } |
| 180 | |
| 181 | UsePosition* use = interval->GetFirstUse(); |
| 182 | while (use != nullptr && use->GetPosition() <= interval->GetStart()) { |
| 183 | // Skip uses before the start of this live interval. |
| 184 | use = use->GetNext(); |
| 185 | } |
| 186 | |
| 187 | while (use != nullptr && use->GetPosition() <= interval->GetEnd()) { |
| 188 | if (use->GetUser() != nullptr && use->RequiresRegister()) { |
| 189 | // Cost for spilling at a register use point. |
| 190 | use_weight += CostForMoveAt(use->GetUser()->GetLifetimePosition() - 1, liveness); |
| 191 | } |
| 192 | use = use->GetNext(); |
| 193 | } |
| 194 | |
| 195 | // We divide by the length of the interval because we want to prioritize |
| 196 | // short intervals; we do not benefit much if we split them further. |
| 197 | return static_cast<float>(use_weight) / static_cast<float>(length); |
| 198 | } |
| 199 | |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 200 | // Interference nodes make up the interference graph, which is the primary data structure in |
| 201 | // graph coloring register allocation. Each node represents a single live interval, and contains |
| 202 | // a set of adjacent nodes corresponding to intervals overlapping with its own. To save memory, |
| 203 | // pre-colored nodes never contain outgoing edges (only incoming ones). |
| 204 | // |
| 205 | // As nodes are pruned from the interference graph, incoming edges of the pruned node are removed, |
| 206 | // but outgoing edges remain in order to later color the node based on the colors of its neighbors. |
| 207 | // |
| 208 | // Note that a pair interval is represented by a single node in the interference graph, which |
| 209 | // essentially requires two colors. One consequence of this is that the degree of a node is not |
| 210 | // necessarily equal to the number of adjacent nodes--instead, the degree reflects the maximum |
| 211 | // number of colors with which a node could interfere. We model this by giving edges different |
| 212 | // weights (1 or 2) to control how much it increases the degree of adjacent nodes. |
| 213 | // For example, the edge between two single nodes will have weight 1. On the other hand, |
| 214 | // the edge between a single node and a pair node will have weight 2. This is because the pair |
| 215 | // node could block up to two colors for the single node, and because the single node could |
| 216 | // block an entire two-register aligned slot for the pair node. |
| 217 | // The degree is defined this way because we use it to decide whether a node is guaranteed a color, |
| 218 | // and thus whether it is safe to prune it from the interference graph early on. |
| 219 | class InterferenceNode : public ArenaObject<kArenaAllocRegisterAllocator> { |
| 220 | public: |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 221 | InterferenceNode(ArenaAllocator* allocator, |
| 222 | LiveInterval* interval, |
| 223 | const SsaLivenessAnalysis& liveness) |
| 224 | : stage(NodeStage::kInitial), |
| 225 | interval_(interval), |
| 226 | adjacent_nodes_(allocator->Adapter(kArenaAllocRegisterAllocator)), |
| 227 | coalesce_opportunities_(allocator->Adapter(kArenaAllocRegisterAllocator)), |
| 228 | out_degree_(interval->HasRegister() ? std::numeric_limits<size_t>::max() : 0), |
| 229 | alias_(this), |
| 230 | spill_weight_(ComputeSpillWeight(interval, liveness)), |
Matthew Gharrity | b6722ff | 2016-08-12 19:07:11 -0700 | [diff] [blame] | 231 | requires_color_(interval->RequiresRegister()), |
| 232 | needs_spill_slot_(false) { |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 233 | DCHECK(!interval->IsHighInterval()) << "Pair nodes should be represented by the low interval"; |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 234 | } |
| 235 | |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 236 | void AddInterference(InterferenceNode* other, bool guaranteed_not_interfering_yet) { |
| 237 | DCHECK(!IsPrecolored()) << "To save memory, fixed nodes should not have outgoing interferences"; |
| 238 | DCHECK_NE(this, other) << "Should not create self loops in the interference graph"; |
| 239 | DCHECK_EQ(this, alias_) << "Should not add interferences to a node that aliases another"; |
| 240 | DCHECK_NE(stage, NodeStage::kPruned); |
| 241 | DCHECK_NE(other->stage, NodeStage::kPruned); |
| 242 | if (guaranteed_not_interfering_yet) { |
| 243 | DCHECK(std::find(adjacent_nodes_.begin(), adjacent_nodes_.end(), other) |
| 244 | == adjacent_nodes_.end()); |
| 245 | adjacent_nodes_.push_back(other); |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 246 | out_degree_ += EdgeWeightWith(other); |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 247 | } else { |
| 248 | auto it = std::find(adjacent_nodes_.begin(), adjacent_nodes_.end(), other); |
| 249 | if (it == adjacent_nodes_.end()) { |
| 250 | adjacent_nodes_.push_back(other); |
| 251 | out_degree_ += EdgeWeightWith(other); |
| 252 | } |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 253 | } |
| 254 | } |
| 255 | |
| 256 | void RemoveInterference(InterferenceNode* other) { |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 257 | DCHECK_EQ(this, alias_) << "Should not remove interferences from a coalesced node"; |
| 258 | DCHECK_EQ(other->stage, NodeStage::kPruned) << "Should only remove interferences when pruning"; |
| 259 | auto it = std::find(adjacent_nodes_.begin(), adjacent_nodes_.end(), other); |
| 260 | if (it != adjacent_nodes_.end()) { |
| 261 | adjacent_nodes_.erase(it); |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 262 | out_degree_ -= EdgeWeightWith(other); |
| 263 | } |
| 264 | } |
| 265 | |
| 266 | bool ContainsInterference(InterferenceNode* other) const { |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 267 | DCHECK(!IsPrecolored()) << "Should not query fixed nodes for interferences"; |
| 268 | DCHECK_EQ(this, alias_) << "Should not query a coalesced node for interferences"; |
| 269 | auto it = std::find(adjacent_nodes_.begin(), adjacent_nodes_.end(), other); |
| 270 | return it != adjacent_nodes_.end(); |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 271 | } |
| 272 | |
| 273 | LiveInterval* GetInterval() const { |
| 274 | return interval_; |
| 275 | } |
| 276 | |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 277 | const ArenaVector<InterferenceNode*>& GetAdjacentNodes() const { |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 278 | return adjacent_nodes_; |
| 279 | } |
| 280 | |
| 281 | size_t GetOutDegree() const { |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 282 | // Pre-colored nodes have infinite degree. |
| 283 | DCHECK(!IsPrecolored() || out_degree_ == std::numeric_limits<size_t>::max()); |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 284 | return out_degree_; |
| 285 | } |
| 286 | |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 287 | void AddCoalesceOpportunity(CoalesceOpportunity* opportunity) { |
| 288 | coalesce_opportunities_.push_back(opportunity); |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 289 | } |
| 290 | |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 291 | void ClearCoalesceOpportunities() { |
| 292 | coalesce_opportunities_.clear(); |
| 293 | } |
| 294 | |
| 295 | bool IsMoveRelated() const { |
| 296 | for (CoalesceOpportunity* opportunity : coalesce_opportunities_) { |
| 297 | if (opportunity->stage == CoalesceStage::kWorklist || |
| 298 | opportunity->stage == CoalesceStage::kActive) { |
| 299 | return true; |
| 300 | } |
| 301 | } |
| 302 | return false; |
| 303 | } |
| 304 | |
| 305 | // Return whether this node already has a color. |
| 306 | // Used to find fixed nodes in the interference graph before coloring. |
| 307 | bool IsPrecolored() const { |
| 308 | return interval_->HasRegister(); |
| 309 | } |
| 310 | |
| 311 | bool IsPair() const { |
| 312 | return interval_->HasHighInterval(); |
| 313 | } |
| 314 | |
| 315 | void SetAlias(InterferenceNode* rep) { |
| 316 | DCHECK_NE(rep->stage, NodeStage::kPruned); |
| 317 | DCHECK_EQ(this, alias_) << "Should only set a node's alias once"; |
| 318 | alias_ = rep; |
| 319 | } |
| 320 | |
| 321 | InterferenceNode* GetAlias() { |
| 322 | if (alias_ != this) { |
| 323 | // Recurse in order to flatten tree of alias pointers. |
| 324 | alias_ = alias_->GetAlias(); |
| 325 | } |
| 326 | return alias_; |
| 327 | } |
| 328 | |
| 329 | const ArenaVector<CoalesceOpportunity*>& GetCoalesceOpportunities() const { |
| 330 | return coalesce_opportunities_; |
| 331 | } |
| 332 | |
| 333 | float GetSpillWeight() const { |
| 334 | return spill_weight_; |
| 335 | } |
| 336 | |
| 337 | bool RequiresColor() const { |
| 338 | return requires_color_; |
| 339 | } |
| 340 | |
Matthew Gharrity | 465ed69 | 2016-07-22 08:52:13 -0700 | [diff] [blame] | 341 | // We give extra weight to edges adjacent to pair nodes. See the general comment on the |
| 342 | // interference graph above. |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 343 | size_t EdgeWeightWith(const InterferenceNode* other) const { |
| 344 | return (IsPair() || other->IsPair()) ? 2 : 1; |
Matthew Gharrity | 465ed69 | 2016-07-22 08:52:13 -0700 | [diff] [blame] | 345 | } |
| 346 | |
Matthew Gharrity | b6722ff | 2016-08-12 19:07:11 -0700 | [diff] [blame] | 347 | bool NeedsSpillSlot() const { |
| 348 | return needs_spill_slot_; |
| 349 | } |
| 350 | |
| 351 | void SetNeedsSpillSlot() { |
| 352 | needs_spill_slot_ = true; |
| 353 | } |
| 354 | |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 355 | // The current stage of this node, indicating which worklist it belongs to. |
| 356 | NodeStage stage; |
| 357 | |
| 358 | private: |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 359 | // The live interval that this node represents. |
| 360 | LiveInterval* const interval_; |
| 361 | |
| 362 | // All nodes interfering with this one. |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 363 | // We use an unsorted vector as a set, since a tree or hash set is too heavy for the |
| 364 | // set sizes that we encounter. Using a vector leads to much better performance. |
| 365 | ArenaVector<InterferenceNode*> adjacent_nodes_; |
| 366 | |
| 367 | // Interference nodes that this node should be coalesced with to reduce moves. |
| 368 | ArenaVector<CoalesceOpportunity*> coalesce_opportunities_; |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 369 | |
| 370 | // The maximum number of colors with which this node could interfere. This could be more than |
| 371 | // the number of adjacent nodes if this is a pair node, or if some adjacent nodes are pair nodes. |
| 372 | // We use "out" degree because incoming edges come from nodes already pruned from the graph, |
| 373 | // and do not affect the coloring of this node. |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 374 | // Pre-colored nodes are treated as having infinite degree. |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 375 | size_t out_degree_; |
| 376 | |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 377 | // The node representing this node in the interference graph. |
| 378 | // Initially set to `this`, and only changed if this node is coalesced into another. |
| 379 | InterferenceNode* alias_; |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 380 | |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 381 | // The cost of splitting and spilling this interval to the stack. |
| 382 | // Nodes with a higher spill weight should be prioritized when assigning registers. |
| 383 | // This is essentially based on use density and location; short intervals with many uses inside |
| 384 | // deeply nested loops have a high spill weight. |
| 385 | const float spill_weight_; |
| 386 | |
| 387 | const bool requires_color_; |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 388 | |
Matthew Gharrity | b6722ff | 2016-08-12 19:07:11 -0700 | [diff] [blame] | 389 | bool needs_spill_slot_; |
| 390 | |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 391 | DISALLOW_COPY_AND_ASSIGN(InterferenceNode); |
| 392 | }; |
| 393 | |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 394 | // The order in which we color nodes is important. To guarantee forward progress, |
| 395 | // we prioritize intervals that require registers, and after that we prioritize |
| 396 | // short intervals. That way, if we fail to color a node, it either won't require a |
| 397 | // register, or it will be a long interval that can be split in order to make the |
| 398 | // interference graph sparser. |
| 399 | // To improve code quality, we prioritize intervals used frequently in deeply nested loops. |
| 400 | // (This metric is secondary to the forward progress requirements above.) |
| 401 | // TODO: May also want to consider: |
| 402 | // - Constants (since they can be rematerialized) |
| 403 | // - Allocated spill slots |
| 404 | static bool HasGreaterNodePriority(const InterferenceNode* lhs, |
| 405 | const InterferenceNode* rhs) { |
| 406 | // (1) Prioritize the node that requires a color. |
| 407 | if (lhs->RequiresColor() != rhs->RequiresColor()) { |
| 408 | return lhs->RequiresColor(); |
| 409 | } |
| 410 | |
| 411 | // (2) Prioritize the interval that has a higher spill weight. |
| 412 | return lhs->GetSpillWeight() > rhs->GetSpillWeight(); |
| 413 | } |
| 414 | |
| 415 | // A ColoringIteration holds the many data structures needed for a single graph coloring attempt, |
| 416 | // and provides methods for each phase of the attempt. |
| 417 | class ColoringIteration { |
| 418 | public: |
| 419 | ColoringIteration(RegisterAllocatorGraphColor* register_allocator, |
| 420 | ArenaAllocator* allocator, |
| 421 | bool processing_core_regs, |
| 422 | size_t num_regs) |
| 423 | : register_allocator_(register_allocator), |
| 424 | allocator_(allocator), |
| 425 | processing_core_regs_(processing_core_regs), |
| 426 | num_regs_(num_regs), |
| 427 | interval_node_map_(allocator->Adapter(kArenaAllocRegisterAllocator)), |
| 428 | prunable_nodes_(allocator->Adapter(kArenaAllocRegisterAllocator)), |
| 429 | pruned_nodes_(allocator->Adapter(kArenaAllocRegisterAllocator)), |
| 430 | simplify_worklist_(allocator->Adapter(kArenaAllocRegisterAllocator)), |
| 431 | freeze_worklist_(allocator->Adapter(kArenaAllocRegisterAllocator)), |
| 432 | spill_worklist_(HasGreaterNodePriority, allocator->Adapter(kArenaAllocRegisterAllocator)), |
| 433 | coalesce_worklist_(CoalesceOpportunity::CmpPriority, |
| 434 | allocator->Adapter(kArenaAllocRegisterAllocator)) {} |
| 435 | |
| 436 | // Use the intervals collected from instructions to construct an |
| 437 | // interference graph mapping intervals to adjacency lists. |
| 438 | // Also, collect synthesized safepoint nodes, used to keep |
| 439 | // track of live intervals across safepoints. |
| 440 | // TODO: Should build safepoints elsewhere. |
| 441 | void BuildInterferenceGraph(const ArenaVector<LiveInterval*>& intervals, |
Vladimir Marko | 70e9746 | 2016-08-09 11:04:26 +0100 | [diff] [blame] | 442 | const ArenaVector<InterferenceNode*>& physical_nodes); |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 443 | |
| 444 | // Add coalesce opportunities to interference nodes. |
| 445 | void FindCoalesceOpportunities(); |
| 446 | |
| 447 | // Prune nodes from the interference graph to be colored later. Build |
| 448 | // a stack (pruned_nodes) containing these intervals in an order determined |
| 449 | // by various heuristics. |
| 450 | void PruneInterferenceGraph(); |
| 451 | |
| 452 | // Process pruned_intervals_ to color the interference graph, spilling when |
| 453 | // necessary. Returns true if successful. Else, some intervals have been |
| 454 | // split, and the interference graph should be rebuilt for another attempt. |
| 455 | bool ColorInterferenceGraph(); |
| 456 | |
| 457 | // Return prunable nodes. |
| 458 | // The register allocator will need to access prunable nodes after coloring |
| 459 | // in order to tell the code generator which registers have been assigned. |
| 460 | const ArenaVector<InterferenceNode*>& GetPrunableNodes() const { |
| 461 | return prunable_nodes_; |
| 462 | } |
| 463 | |
| 464 | private: |
| 465 | // Create a coalesce opportunity between two nodes. |
| 466 | void CreateCoalesceOpportunity(InterferenceNode* a, |
| 467 | InterferenceNode* b, |
| 468 | CoalesceKind kind, |
| 469 | size_t position); |
| 470 | |
| 471 | // Add an edge in the interference graph, if valid. |
| 472 | // Note that `guaranteed_not_interfering_yet` is used to optimize adjacency set insertion |
| 473 | // when possible. |
| 474 | void AddPotentialInterference(InterferenceNode* from, |
| 475 | InterferenceNode* to, |
| 476 | bool guaranteed_not_interfering_yet, |
| 477 | bool both_directions = true); |
| 478 | |
| 479 | // Invalidate all coalesce opportunities this node has, so that it (and possibly its neighbors) |
| 480 | // may be pruned from the interference graph. |
| 481 | void FreezeMoves(InterferenceNode* node); |
| 482 | |
| 483 | // Prune a node from the interference graph, updating worklists if necessary. |
| 484 | void PruneNode(InterferenceNode* node); |
| 485 | |
| 486 | // Add coalesce opportunities associated with this node to the coalesce worklist. |
| 487 | void EnableCoalesceOpportunities(InterferenceNode* node); |
| 488 | |
| 489 | // If needed, from `node` from the freeze worklist to the simplify worklist. |
| 490 | void CheckTransitionFromFreezeWorklist(InterferenceNode* node); |
| 491 | |
| 492 | // Return true if `into` is colored, and `from` can be coalesced with `into` conservatively. |
| 493 | bool PrecoloredHeuristic(InterferenceNode* from, InterferenceNode* into); |
| 494 | |
| 495 | // Return true if `from` and `into` are uncolored, and can be coalesced conservatively. |
| 496 | bool UncoloredHeuristic(InterferenceNode* from, InterferenceNode* into); |
| 497 | |
| 498 | void Coalesce(CoalesceOpportunity* opportunity); |
| 499 | |
| 500 | // Merge `from` into `into` in the interference graph. |
| 501 | void Combine(InterferenceNode* from, InterferenceNode* into); |
| 502 | |
| 503 | // A reference to the register allocator instance, |
| 504 | // needed to split intervals and assign spill slots. |
| 505 | RegisterAllocatorGraphColor* register_allocator_; |
| 506 | |
| 507 | // An arena allocator used for a single graph coloring attempt. |
| 508 | ArenaAllocator* allocator_; |
| 509 | |
| 510 | const bool processing_core_regs_; |
| 511 | |
| 512 | const size_t num_regs_; |
| 513 | |
| 514 | // A map from live intervals to interference nodes. |
| 515 | ArenaHashMap<LiveInterval*, InterferenceNode*> interval_node_map_; |
| 516 | |
| 517 | // Uncolored nodes that should be pruned from the interference graph. |
| 518 | ArenaVector<InterferenceNode*> prunable_nodes_; |
| 519 | |
| 520 | // A stack of nodes pruned from the interference graph, waiting to be pruned. |
| 521 | ArenaStdStack<InterferenceNode*> pruned_nodes_; |
| 522 | |
| 523 | // A queue containing low degree, non-move-related nodes that can pruned immediately. |
| 524 | ArenaDeque<InterferenceNode*> simplify_worklist_; |
| 525 | |
| 526 | // A queue containing low degree, move-related nodes. |
| 527 | ArenaDeque<InterferenceNode*> freeze_worklist_; |
| 528 | |
| 529 | // A queue containing high degree nodes. |
| 530 | // If we have to prune from the spill worklist, we cannot guarantee |
| 531 | // the pruned node a color, so we order the worklist by priority. |
| 532 | ArenaPriorityQueue<InterferenceNode*, decltype(&HasGreaterNodePriority)> spill_worklist_; |
| 533 | |
| 534 | // A queue containing coalesce opportunities. |
| 535 | // We order the coalesce worklist by priority, since some coalesce opportunities (e.g., those |
| 536 | // inside of loops) are more important than others. |
| 537 | ArenaPriorityQueue<CoalesceOpportunity*, |
| 538 | decltype(&CoalesceOpportunity::CmpPriority)> coalesce_worklist_; |
| 539 | |
| 540 | DISALLOW_COPY_AND_ASSIGN(ColoringIteration); |
| 541 | }; |
| 542 | |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 543 | static bool IsCoreInterval(LiveInterval* interval) { |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 544 | return !Primitive::IsFloatingPointType(interval->GetType()); |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 545 | } |
| 546 | |
| 547 | static size_t ComputeReservedArtMethodSlots(const CodeGenerator& codegen) { |
| 548 | return static_cast<size_t>(InstructionSetPointerSize(codegen.GetInstructionSet())) / kVRegSize; |
| 549 | } |
| 550 | |
| 551 | RegisterAllocatorGraphColor::RegisterAllocatorGraphColor(ArenaAllocator* allocator, |
| 552 | CodeGenerator* codegen, |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 553 | const SsaLivenessAnalysis& liveness, |
| 554 | bool iterative_move_coalescing) |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 555 | : RegisterAllocator(allocator, codegen, liveness), |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 556 | iterative_move_coalescing_(iterative_move_coalescing), |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 557 | core_intervals_(allocator->Adapter(kArenaAllocRegisterAllocator)), |
| 558 | fp_intervals_(allocator->Adapter(kArenaAllocRegisterAllocator)), |
| 559 | temp_intervals_(allocator->Adapter(kArenaAllocRegisterAllocator)), |
| 560 | safepoints_(allocator->Adapter(kArenaAllocRegisterAllocator)), |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 561 | physical_core_nodes_(allocator->Adapter(kArenaAllocRegisterAllocator)), |
| 562 | physical_fp_nodes_(allocator->Adapter(kArenaAllocRegisterAllocator)), |
Matthew Gharrity | b6722ff | 2016-08-12 19:07:11 -0700 | [diff] [blame] | 563 | num_int_spill_slots_(0), |
| 564 | num_double_spill_slots_(0), |
| 565 | num_float_spill_slots_(0), |
| 566 | num_long_spill_slots_(0), |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 567 | catch_phi_spill_slot_counter_(0), |
| 568 | reserved_art_method_slots_(ComputeReservedArtMethodSlots(*codegen)), |
Vladimir Marko | 70e9746 | 2016-08-09 11:04:26 +0100 | [diff] [blame] | 569 | reserved_out_slots_(codegen->GetGraph()->GetMaximumNumberOfOutVRegs()) { |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 570 | // Before we ask for blocked registers, set them up in the code generator. |
| 571 | codegen->SetupBlockedRegisters(); |
| 572 | |
| 573 | // Initialize physical core register live intervals and blocked registers. |
| 574 | // This includes globally blocked registers, such as the stack pointer. |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 575 | physical_core_nodes_.resize(codegen_->GetNumberOfCoreRegisters(), nullptr); |
| 576 | for (size_t i = 0; i < codegen_->GetNumberOfCoreRegisters(); ++i) { |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 577 | LiveInterval* interval = LiveInterval::MakeFixedInterval(allocator_, i, Primitive::kPrimInt); |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 578 | physical_core_nodes_[i] = |
| 579 | new (allocator_) InterferenceNode(allocator_, interval, liveness); |
| 580 | physical_core_nodes_[i]->stage = NodeStage::kPrecolored; |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 581 | core_intervals_.push_back(interval); |
| 582 | if (codegen_->IsBlockedCoreRegister(i)) { |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 583 | interval->AddRange(0, liveness.GetMaxLifetimePosition()); |
| 584 | } |
| 585 | } |
| 586 | // Initialize physical floating point register live intervals and blocked registers. |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 587 | physical_fp_nodes_.resize(codegen_->GetNumberOfFloatingPointRegisters(), nullptr); |
| 588 | for (size_t i = 0; i < codegen_->GetNumberOfFloatingPointRegisters(); ++i) { |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 589 | LiveInterval* interval = LiveInterval::MakeFixedInterval(allocator_, i, Primitive::kPrimFloat); |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 590 | physical_fp_nodes_[i] = |
| 591 | new (allocator_) InterferenceNode(allocator_, interval, liveness); |
| 592 | physical_fp_nodes_[i]->stage = NodeStage::kPrecolored; |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 593 | fp_intervals_.push_back(interval); |
| 594 | if (codegen_->IsBlockedFloatingPointRegister(i)) { |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 595 | interval->AddRange(0, liveness.GetMaxLifetimePosition()); |
| 596 | } |
| 597 | } |
| 598 | } |
| 599 | |
| 600 | void RegisterAllocatorGraphColor::AllocateRegisters() { |
| 601 | // (1) Collect and prepare live intervals. |
| 602 | ProcessInstructions(); |
| 603 | |
| 604 | for (bool processing_core_regs : {true, false}) { |
| 605 | ArenaVector<LiveInterval*>& intervals = processing_core_regs |
| 606 | ? core_intervals_ |
| 607 | : fp_intervals_; |
| 608 | size_t num_registers = processing_core_regs |
| 609 | ? codegen_->GetNumberOfCoreRegisters() |
| 610 | : codegen_->GetNumberOfFloatingPointRegisters(); |
| 611 | |
| 612 | size_t attempt = 0; |
| 613 | while (true) { |
| 614 | ++attempt; |
| 615 | DCHECK(attempt <= kMaxGraphColoringAttemptsDebug) |
| 616 | << "Exceeded debug max graph coloring register allocation attempts. " |
| 617 | << "This could indicate that the register allocator is not making forward progress, " |
| 618 | << "which could be caused by prioritizing the wrong live intervals. (Short intervals " |
| 619 | << "should be prioritized over long ones, because they cannot be split further.)"; |
| 620 | |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 621 | // Many data structures are cleared between graph coloring attempts, so we reduce |
| 622 | // total memory usage by using a new arena allocator for each attempt. |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 623 | ArenaAllocator coloring_attempt_allocator(allocator_->GetArenaPool()); |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 624 | ColoringIteration iteration(this, |
| 625 | &coloring_attempt_allocator, |
| 626 | processing_core_regs, |
| 627 | num_registers); |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 628 | |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 629 | // (2) Build the interference graph. Also gather safepoints. |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 630 | ArenaVector<InterferenceNode*> safepoints( |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 631 | coloring_attempt_allocator.Adapter(kArenaAllocRegisterAllocator)); |
| 632 | ArenaVector<InterferenceNode*>& physical_nodes = processing_core_regs |
| 633 | ? physical_core_nodes_ |
| 634 | : physical_fp_nodes_; |
Vladimir Marko | 70e9746 | 2016-08-09 11:04:26 +0100 | [diff] [blame] | 635 | iteration.BuildInterferenceGraph(intervals, physical_nodes); |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 636 | |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 637 | // (3) Add coalesce opportunities. |
| 638 | // If we have tried coloring the graph a suspiciously high number of times, give |
| 639 | // up on move coalescing, just in case the coalescing heuristics are not conservative. |
| 640 | // (This situation will be caught if DCHECKs are turned on.) |
| 641 | if (iterative_move_coalescing_ && attempt <= kMaxGraphColoringAttemptsDebug) { |
| 642 | iteration.FindCoalesceOpportunities(); |
| 643 | } |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 644 | |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 645 | // (4) Prune all uncolored nodes from interference graph. |
| 646 | iteration.PruneInterferenceGraph(); |
| 647 | |
| 648 | // (5) Color pruned nodes based on interferences. |
| 649 | bool successful = iteration.ColorInterferenceGraph(); |
| 650 | |
| 651 | // We manually clear coalesce opportunities for physical nodes, |
| 652 | // since they persist across coloring attempts. |
| 653 | for (InterferenceNode* node : physical_core_nodes_) { |
| 654 | node->ClearCoalesceOpportunities(); |
| 655 | } |
| 656 | for (InterferenceNode* node : physical_fp_nodes_) { |
| 657 | node->ClearCoalesceOpportunities(); |
| 658 | } |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 659 | |
| 660 | if (successful) { |
Matthew Gharrity | b6722ff | 2016-08-12 19:07:11 -0700 | [diff] [blame] | 661 | // Assign spill slots. |
| 662 | AllocateSpillSlots(iteration.GetPrunableNodes()); |
| 663 | |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 664 | // Tell the code generator which registers were allocated. |
| 665 | // We only look at prunable_nodes because we already told the code generator about |
| 666 | // fixed intervals while processing instructions. We also ignore the fixed intervals |
| 667 | // placed at the top of catch blocks. |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 668 | for (InterferenceNode* node : iteration.GetPrunableNodes()) { |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 669 | LiveInterval* interval = node->GetInterval(); |
| 670 | if (interval->HasRegister()) { |
| 671 | Location low_reg = processing_core_regs |
| 672 | ? Location::RegisterLocation(interval->GetRegister()) |
| 673 | : Location::FpuRegisterLocation(interval->GetRegister()); |
| 674 | codegen_->AddAllocatedRegister(low_reg); |
| 675 | if (interval->HasHighInterval()) { |
| 676 | LiveInterval* high = interval->GetHighInterval(); |
| 677 | DCHECK(high->HasRegister()); |
| 678 | Location high_reg = processing_core_regs |
| 679 | ? Location::RegisterLocation(high->GetRegister()) |
| 680 | : Location::FpuRegisterLocation(high->GetRegister()); |
| 681 | codegen_->AddAllocatedRegister(high_reg); |
| 682 | } |
| 683 | } else { |
| 684 | DCHECK(!interval->HasHighInterval() || !interval->GetHighInterval()->HasRegister()); |
| 685 | } |
| 686 | } |
| 687 | |
| 688 | break; |
| 689 | } |
| 690 | } // while unsuccessful |
| 691 | } // for processing_core_instructions |
| 692 | |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 693 | // (6) Resolve locations and deconstruct SSA form. |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 694 | RegisterAllocationResolver(allocator_, codegen_, liveness_) |
Vladimir Marko | 70e9746 | 2016-08-09 11:04:26 +0100 | [diff] [blame] | 695 | .Resolve(ArrayRef<HInstruction* const>(safepoints_), |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 696 | reserved_art_method_slots_ + reserved_out_slots_, |
Matthew Gharrity | b6722ff | 2016-08-12 19:07:11 -0700 | [diff] [blame] | 697 | num_int_spill_slots_, |
| 698 | num_long_spill_slots_, |
| 699 | num_float_spill_slots_, |
| 700 | num_double_spill_slots_, |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 701 | catch_phi_spill_slot_counter_, |
| 702 | temp_intervals_); |
| 703 | |
| 704 | if (kIsDebugBuild) { |
| 705 | Validate(/*log_fatal_on_failure*/ true); |
| 706 | } |
| 707 | } |
| 708 | |
| 709 | bool RegisterAllocatorGraphColor::Validate(bool log_fatal_on_failure) { |
| 710 | for (bool processing_core_regs : {true, false}) { |
| 711 | ArenaVector<LiveInterval*> intervals( |
| 712 | allocator_->Adapter(kArenaAllocRegisterAllocatorValidate)); |
| 713 | for (size_t i = 0; i < liveness_.GetNumberOfSsaValues(); ++i) { |
| 714 | HInstruction* instruction = liveness_.GetInstructionFromSsaIndex(i); |
| 715 | LiveInterval* interval = instruction->GetLiveInterval(); |
| 716 | if (interval != nullptr && IsCoreInterval(interval) == processing_core_regs) { |
| 717 | intervals.push_back(instruction->GetLiveInterval()); |
| 718 | } |
| 719 | } |
| 720 | |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 721 | ArenaVector<InterferenceNode*>& physical_nodes = processing_core_regs |
| 722 | ? physical_core_nodes_ |
| 723 | : physical_fp_nodes_; |
| 724 | for (InterferenceNode* fixed : physical_nodes) { |
| 725 | LiveInterval* interval = fixed->GetInterval(); |
| 726 | if (interval->GetFirstRange() != nullptr) { |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 727 | // Ideally we would check fixed ranges as well, but currently there are times when |
| 728 | // two fixed intervals for the same register will overlap. For example, a fixed input |
| 729 | // and a fixed output may sometimes share the same register, in which there will be two |
| 730 | // fixed intervals for the same place. |
| 731 | } |
| 732 | } |
| 733 | |
| 734 | for (LiveInterval* temp : temp_intervals_) { |
| 735 | if (IsCoreInterval(temp) == processing_core_regs) { |
| 736 | intervals.push_back(temp); |
| 737 | } |
| 738 | } |
| 739 | |
Matthew Gharrity | b6722ff | 2016-08-12 19:07:11 -0700 | [diff] [blame] | 740 | size_t spill_slots = num_int_spill_slots_ |
| 741 | + num_long_spill_slots_ |
| 742 | + num_float_spill_slots_ |
| 743 | + num_double_spill_slots_ |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 744 | + catch_phi_spill_slot_counter_; |
| 745 | bool ok = ValidateIntervals(intervals, |
| 746 | spill_slots, |
| 747 | reserved_art_method_slots_ + reserved_out_slots_, |
| 748 | *codegen_, |
| 749 | allocator_, |
| 750 | processing_core_regs, |
| 751 | log_fatal_on_failure); |
| 752 | if (!ok) { |
| 753 | return false; |
| 754 | } |
| 755 | } // for processing_core_regs |
| 756 | |
| 757 | return true; |
| 758 | } |
| 759 | |
| 760 | void RegisterAllocatorGraphColor::ProcessInstructions() { |
Vladimir Marko | 2c45bc9 | 2016-10-25 16:54:12 +0100 | [diff] [blame] | 761 | for (HBasicBlock* block : codegen_->GetGraph()->GetLinearPostOrder()) { |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 762 | // Note that we currently depend on this ordering, since some helper |
| 763 | // code is designed for linear scan register allocation. |
| 764 | for (HBackwardInstructionIterator instr_it(block->GetInstructions()); |
| 765 | !instr_it.Done(); |
| 766 | instr_it.Advance()) { |
| 767 | ProcessInstruction(instr_it.Current()); |
| 768 | } |
| 769 | |
| 770 | for (HInstructionIterator phi_it(block->GetPhis()); !phi_it.Done(); phi_it.Advance()) { |
| 771 | ProcessInstruction(phi_it.Current()); |
| 772 | } |
| 773 | |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 774 | if (block->IsCatchBlock() |
| 775 | || (block->IsLoopHeader() && block->GetLoopInformation()->IsIrreducible())) { |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 776 | // By blocking all registers at the top of each catch block or irreducible loop, we force |
| 777 | // intervals belonging to the live-in set of the catch/header block to be spilled. |
| 778 | // TODO(ngeoffray): Phis in this block could be allocated in register. |
| 779 | size_t position = block->GetLifetimeStart(); |
| 780 | BlockRegisters(position, position + 1); |
| 781 | } |
| 782 | } |
| 783 | } |
| 784 | |
| 785 | void RegisterAllocatorGraphColor::ProcessInstruction(HInstruction* instruction) { |
| 786 | LocationSummary* locations = instruction->GetLocations(); |
| 787 | if (locations == nullptr) { |
| 788 | return; |
| 789 | } |
| 790 | if (locations->NeedsSafepoint() && codegen_->IsLeafMethod()) { |
| 791 | // We do this here because we do not want the suspend check to artificially |
| 792 | // create live registers. |
| 793 | DCHECK(instruction->IsSuspendCheckEntry()); |
| 794 | DCHECK_EQ(locations->GetTempCount(), 0u); |
| 795 | instruction->GetBlock()->RemoveInstruction(instruction); |
| 796 | return; |
| 797 | } |
| 798 | |
| 799 | CheckForTempLiveIntervals(instruction); |
| 800 | CheckForSafepoint(instruction); |
| 801 | if (instruction->GetLocations()->WillCall()) { |
| 802 | // If a call will happen, create fixed intervals for caller-save registers. |
| 803 | // TODO: Note that it may be beneficial to later split intervals at this point, |
| 804 | // so that we allow last-minute moves from a caller-save register |
| 805 | // to a callee-save register. |
| 806 | BlockRegisters(instruction->GetLifetimePosition(), |
| 807 | instruction->GetLifetimePosition() + 1, |
| 808 | /*caller_save_only*/ true); |
| 809 | } |
| 810 | CheckForFixedInputs(instruction); |
| 811 | |
| 812 | LiveInterval* interval = instruction->GetLiveInterval(); |
| 813 | if (interval == nullptr) { |
| 814 | // Instructions lacking a valid output location do not have a live interval. |
| 815 | DCHECK(!locations->Out().IsValid()); |
| 816 | return; |
| 817 | } |
| 818 | |
| 819 | // Low intervals act as representatives for their corresponding high interval. |
| 820 | DCHECK(!interval->IsHighInterval()); |
| 821 | if (codegen_->NeedsTwoRegisters(interval->GetType())) { |
| 822 | interval->AddHighInterval(); |
| 823 | } |
| 824 | AddSafepointsFor(instruction); |
| 825 | CheckForFixedOutput(instruction); |
| 826 | AllocateSpillSlotForCatchPhi(instruction); |
| 827 | |
| 828 | ArenaVector<LiveInterval*>& intervals = IsCoreInterval(interval) |
| 829 | ? core_intervals_ |
| 830 | : fp_intervals_; |
| 831 | if (interval->HasSpillSlot() || instruction->IsConstant()) { |
| 832 | // Note that if an interval already has a spill slot, then its value currently resides |
| 833 | // in the stack (e.g., parameters). Thus we do not have to allocate a register until its first |
| 834 | // register use. This is also true for constants, which can be materialized at any point. |
| 835 | size_t first_register_use = interval->FirstRegisterUse(); |
| 836 | if (first_register_use != kNoLifetime) { |
| 837 | LiveInterval* split = SplitBetween(interval, interval->GetStart(), first_register_use - 1); |
| 838 | intervals.push_back(split); |
| 839 | } else { |
| 840 | // We won't allocate a register for this value. |
| 841 | } |
| 842 | } else { |
| 843 | intervals.push_back(interval); |
| 844 | } |
| 845 | } |
| 846 | |
| 847 | void RegisterAllocatorGraphColor::CheckForFixedInputs(HInstruction* instruction) { |
| 848 | // We simply block physical registers where necessary. |
| 849 | // TODO: Ideally we would coalesce the physical register with the register |
| 850 | // allocated to the input value, but this can be tricky if, e.g., there |
| 851 | // could be multiple physical register uses of the same value at the |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 852 | // same instruction. Furthermore, there's currently no distinction between |
| 853 | // fixed inputs to a call (which will be clobbered) and other fixed inputs (which |
| 854 | // may not be clobbered). |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 855 | LocationSummary* locations = instruction->GetLocations(); |
| 856 | size_t position = instruction->GetLifetimePosition(); |
| 857 | for (size_t i = 0; i < locations->GetInputCount(); ++i) { |
| 858 | Location input = locations->InAt(i); |
| 859 | if (input.IsRegister() || input.IsFpuRegister()) { |
| 860 | BlockRegister(input, position, position + 1); |
| 861 | codegen_->AddAllocatedRegister(input); |
| 862 | } else if (input.IsPair()) { |
| 863 | BlockRegister(input.ToLow(), position, position + 1); |
| 864 | BlockRegister(input.ToHigh(), position, position + 1); |
| 865 | codegen_->AddAllocatedRegister(input.ToLow()); |
| 866 | codegen_->AddAllocatedRegister(input.ToHigh()); |
| 867 | } |
| 868 | } |
| 869 | } |
| 870 | |
| 871 | void RegisterAllocatorGraphColor::CheckForFixedOutput(HInstruction* instruction) { |
| 872 | // If an instruction has a fixed output location, we give the live interval a register and then |
| 873 | // proactively split it just after the definition point to avoid creating too many interferences |
| 874 | // with a fixed node. |
| 875 | LiveInterval* interval = instruction->GetLiveInterval(); |
| 876 | Location out = interval->GetDefinedBy()->GetLocations()->Out(); |
| 877 | size_t position = instruction->GetLifetimePosition(); |
| 878 | DCHECK_GE(interval->GetEnd() - position, 2u); |
| 879 | |
| 880 | if (out.IsUnallocated() && out.GetPolicy() == Location::kSameAsFirstInput) { |
| 881 | out = instruction->GetLocations()->InAt(0); |
| 882 | } |
| 883 | |
| 884 | if (out.IsRegister() || out.IsFpuRegister()) { |
| 885 | interval->SetRegister(out.reg()); |
| 886 | codegen_->AddAllocatedRegister(out); |
| 887 | Split(interval, position + 1); |
| 888 | } else if (out.IsPair()) { |
| 889 | interval->SetRegister(out.low()); |
| 890 | interval->GetHighInterval()->SetRegister(out.high()); |
| 891 | codegen_->AddAllocatedRegister(out.ToLow()); |
| 892 | codegen_->AddAllocatedRegister(out.ToHigh()); |
| 893 | Split(interval, position + 1); |
| 894 | } else if (out.IsStackSlot() || out.IsDoubleStackSlot()) { |
| 895 | interval->SetSpillSlot(out.GetStackIndex()); |
| 896 | } else { |
| 897 | DCHECK(out.IsUnallocated() || out.IsConstant()); |
| 898 | } |
| 899 | } |
| 900 | |
| 901 | void RegisterAllocatorGraphColor::AddSafepointsFor(HInstruction* instruction) { |
| 902 | LiveInterval* interval = instruction->GetLiveInterval(); |
| 903 | for (size_t safepoint_index = safepoints_.size(); safepoint_index > 0; --safepoint_index) { |
| 904 | HInstruction* safepoint = safepoints_[safepoint_index - 1u]; |
| 905 | size_t safepoint_position = safepoint->GetLifetimePosition(); |
| 906 | |
| 907 | // Test that safepoints_ are ordered in the optimal way. |
| 908 | DCHECK(safepoint_index == safepoints_.size() || |
| 909 | safepoints_[safepoint_index]->GetLifetimePosition() < safepoint_position); |
| 910 | |
| 911 | if (safepoint_position == interval->GetStart()) { |
| 912 | // The safepoint is for this instruction, so the location of the instruction |
| 913 | // does not need to be saved. |
| 914 | DCHECK_EQ(safepoint_index, safepoints_.size()); |
| 915 | DCHECK_EQ(safepoint, instruction); |
| 916 | continue; |
| 917 | } else if (interval->IsDeadAt(safepoint_position)) { |
| 918 | break; |
| 919 | } else if (!interval->Covers(safepoint_position)) { |
| 920 | // Hole in the interval. |
| 921 | continue; |
| 922 | } |
| 923 | interval->AddSafepoint(safepoint); |
| 924 | } |
| 925 | } |
| 926 | |
| 927 | void RegisterAllocatorGraphColor::CheckForTempLiveIntervals(HInstruction* instruction) { |
| 928 | LocationSummary* locations = instruction->GetLocations(); |
| 929 | size_t position = instruction->GetLifetimePosition(); |
| 930 | for (size_t i = 0; i < locations->GetTempCount(); ++i) { |
| 931 | Location temp = locations->GetTemp(i); |
| 932 | if (temp.IsRegister() || temp.IsFpuRegister()) { |
| 933 | BlockRegister(temp, position, position + 1); |
| 934 | codegen_->AddAllocatedRegister(temp); |
| 935 | } else { |
| 936 | DCHECK(temp.IsUnallocated()); |
| 937 | switch (temp.GetPolicy()) { |
| 938 | case Location::kRequiresRegister: { |
| 939 | LiveInterval* interval = |
| 940 | LiveInterval::MakeTempInterval(allocator_, Primitive::kPrimInt); |
| 941 | interval->AddTempUse(instruction, i); |
| 942 | core_intervals_.push_back(interval); |
| 943 | temp_intervals_.push_back(interval); |
| 944 | break; |
| 945 | } |
| 946 | |
| 947 | case Location::kRequiresFpuRegister: { |
| 948 | LiveInterval* interval = |
| 949 | LiveInterval::MakeTempInterval(allocator_, Primitive::kPrimDouble); |
| 950 | interval->AddTempUse(instruction, i); |
| 951 | fp_intervals_.push_back(interval); |
| 952 | temp_intervals_.push_back(interval); |
| 953 | if (codegen_->NeedsTwoRegisters(Primitive::kPrimDouble)) { |
| 954 | interval->AddHighInterval(/*is_temp*/ true); |
| 955 | temp_intervals_.push_back(interval->GetHighInterval()); |
| 956 | } |
| 957 | break; |
| 958 | } |
| 959 | |
| 960 | default: |
| 961 | LOG(FATAL) << "Unexpected policy for temporary location " |
| 962 | << temp.GetPolicy(); |
| 963 | } |
| 964 | } |
| 965 | } |
| 966 | } |
| 967 | |
| 968 | void RegisterAllocatorGraphColor::CheckForSafepoint(HInstruction* instruction) { |
| 969 | LocationSummary* locations = instruction->GetLocations(); |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 970 | |
| 971 | if (locations->NeedsSafepoint()) { |
| 972 | safepoints_.push_back(instruction); |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 973 | } |
| 974 | } |
| 975 | |
| 976 | LiveInterval* RegisterAllocatorGraphColor::TrySplit(LiveInterval* interval, size_t position) { |
| 977 | if (interval->GetStart() < position && position < interval->GetEnd()) { |
| 978 | return Split(interval, position); |
| 979 | } else { |
| 980 | return interval; |
| 981 | } |
| 982 | } |
| 983 | |
| 984 | void RegisterAllocatorGraphColor::SplitAtRegisterUses(LiveInterval* interval) { |
| 985 | DCHECK(!interval->IsHighInterval()); |
| 986 | |
| 987 | // Split just after a register definition. |
| 988 | if (interval->IsParent() && interval->DefinitionRequiresRegister()) { |
| 989 | interval = TrySplit(interval, interval->GetStart() + 1); |
| 990 | } |
| 991 | |
| 992 | UsePosition* use = interval->GetFirstUse(); |
| 993 | while (use != nullptr && use->GetPosition() < interval->GetStart()) { |
| 994 | use = use->GetNext(); |
| 995 | } |
| 996 | |
| 997 | // Split around register uses. |
| 998 | size_t end = interval->GetEnd(); |
| 999 | while (use != nullptr && use->GetPosition() <= end) { |
| 1000 | if (use->RequiresRegister()) { |
| 1001 | size_t position = use->GetPosition(); |
| 1002 | interval = TrySplit(interval, position - 1); |
| 1003 | if (liveness_.GetInstructionFromPosition(position / 2)->IsControlFlow()) { |
| 1004 | // If we are at the very end of a basic block, we cannot split right |
| 1005 | // at the use. Split just after instead. |
| 1006 | interval = TrySplit(interval, position + 1); |
| 1007 | } else { |
| 1008 | interval = TrySplit(interval, position); |
| 1009 | } |
| 1010 | } |
| 1011 | use = use->GetNext(); |
| 1012 | } |
| 1013 | } |
| 1014 | |
| 1015 | void RegisterAllocatorGraphColor::AllocateSpillSlotForCatchPhi(HInstruction* instruction) { |
| 1016 | if (instruction->IsPhi() && instruction->AsPhi()->IsCatchPhi()) { |
| 1017 | HPhi* phi = instruction->AsPhi(); |
| 1018 | LiveInterval* interval = phi->GetLiveInterval(); |
| 1019 | |
| 1020 | HInstruction* previous_phi = phi->GetPrevious(); |
| 1021 | DCHECK(previous_phi == nullptr || |
| 1022 | previous_phi->AsPhi()->GetRegNumber() <= phi->GetRegNumber()) |
| 1023 | << "Phis expected to be sorted by vreg number, " |
| 1024 | << "so that equivalent phis are adjacent."; |
| 1025 | |
| 1026 | if (phi->IsVRegEquivalentOf(previous_phi)) { |
| 1027 | // Assign the same spill slot. |
| 1028 | DCHECK(previous_phi->GetLiveInterval()->HasSpillSlot()); |
| 1029 | interval->SetSpillSlot(previous_phi->GetLiveInterval()->GetSpillSlot()); |
| 1030 | } else { |
| 1031 | interval->SetSpillSlot(catch_phi_spill_slot_counter_); |
Aart Bik | cc89525 | 2017-03-21 10:55:15 -0700 | [diff] [blame] | 1032 | catch_phi_spill_slot_counter_ += interval->NumberOfSpillSlotsNeeded(); |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 1033 | } |
| 1034 | } |
| 1035 | } |
| 1036 | |
| 1037 | void RegisterAllocatorGraphColor::BlockRegister(Location location, |
| 1038 | size_t start, |
| 1039 | size_t end) { |
| 1040 | DCHECK(location.IsRegister() || location.IsFpuRegister()); |
| 1041 | int reg = location.reg(); |
| 1042 | LiveInterval* interval = location.IsRegister() |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1043 | ? physical_core_nodes_[reg]->GetInterval() |
| 1044 | : physical_fp_nodes_[reg]->GetInterval(); |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 1045 | DCHECK(interval->GetRegister() == reg); |
| 1046 | bool blocked_by_codegen = location.IsRegister() |
| 1047 | ? codegen_->IsBlockedCoreRegister(reg) |
| 1048 | : codegen_->IsBlockedFloatingPointRegister(reg); |
| 1049 | if (blocked_by_codegen) { |
| 1050 | // We've already blocked this register for the entire method. (And adding a |
| 1051 | // range inside another range violates the preconditions of AddRange). |
| 1052 | } else { |
| 1053 | interval->AddRange(start, end); |
| 1054 | } |
| 1055 | } |
| 1056 | |
| 1057 | void RegisterAllocatorGraphColor::BlockRegisters(size_t start, size_t end, bool caller_save_only) { |
| 1058 | for (size_t i = 0; i < codegen_->GetNumberOfCoreRegisters(); ++i) { |
| 1059 | if (!caller_save_only || !codegen_->IsCoreCalleeSaveRegister(i)) { |
| 1060 | BlockRegister(Location::RegisterLocation(i), start, end); |
| 1061 | } |
| 1062 | } |
| 1063 | for (size_t i = 0; i < codegen_->GetNumberOfFloatingPointRegisters(); ++i) { |
| 1064 | if (!caller_save_only || !codegen_->IsFloatingPointCalleeSaveRegister(i)) { |
| 1065 | BlockRegister(Location::FpuRegisterLocation(i), start, end); |
| 1066 | } |
| 1067 | } |
| 1068 | } |
| 1069 | |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1070 | void ColoringIteration::AddPotentialInterference(InterferenceNode* from, |
| 1071 | InterferenceNode* to, |
| 1072 | bool guaranteed_not_interfering_yet, |
| 1073 | bool both_directions) { |
| 1074 | if (from->IsPrecolored()) { |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 1075 | // We save space by ignoring outgoing edges from fixed nodes. |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1076 | } else if (to->IsPrecolored()) { |
| 1077 | // It is important that only a single node represents a given fixed register in the |
| 1078 | // interference graph. We retrieve that node here. |
| 1079 | const ArenaVector<InterferenceNode*>& physical_nodes = to->GetInterval()->IsFloatingPoint() |
| 1080 | ? register_allocator_->physical_fp_nodes_ |
| 1081 | : register_allocator_->physical_core_nodes_; |
| 1082 | InterferenceNode* physical_node = physical_nodes[to->GetInterval()->GetRegister()]; |
| 1083 | from->AddInterference(physical_node, /*guaranteed_not_interfering_yet*/ false); |
| 1084 | DCHECK_EQ(to->GetInterval()->GetRegister(), physical_node->GetInterval()->GetRegister()); |
| 1085 | DCHECK_EQ(to->GetAlias(), physical_node) << "Fixed nodes should alias the canonical fixed node"; |
| 1086 | |
| 1087 | // If a node interferes with a fixed pair node, the weight of the edge may |
| 1088 | // be inaccurate after using the alias of the pair node, because the alias of the pair node |
| 1089 | // is a singular node. |
| 1090 | // We could make special pair fixed nodes, but that ends up being too conservative because |
| 1091 | // a node could then interfere with both {r1} and {r1,r2}, leading to a degree of |
| 1092 | // three rather than two. |
| 1093 | // Instead, we explicitly add an interference with the high node of the fixed pair node. |
| 1094 | // TODO: This is too conservative at time for pair nodes, but the fact that fixed pair intervals |
| 1095 | // can be unaligned on x86 complicates things. |
| 1096 | if (to->IsPair()) { |
| 1097 | InterferenceNode* high_node = |
| 1098 | physical_nodes[to->GetInterval()->GetHighInterval()->GetRegister()]; |
| 1099 | DCHECK_EQ(to->GetInterval()->GetHighInterval()->GetRegister(), |
| 1100 | high_node->GetInterval()->GetRegister()); |
| 1101 | from->AddInterference(high_node, /*guaranteed_not_interfering_yet*/ false); |
| 1102 | } |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 1103 | } else { |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1104 | // Standard interference between two uncolored nodes. |
| 1105 | from->AddInterference(to, guaranteed_not_interfering_yet); |
| 1106 | } |
| 1107 | |
| 1108 | if (both_directions) { |
| 1109 | AddPotentialInterference(to, from, guaranteed_not_interfering_yet, /*both_directions*/ false); |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 1110 | } |
| 1111 | } |
| 1112 | |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1113 | // Returns true if `in_node` represents an input interval of `out_node`, and the output interval |
| 1114 | // is allowed to have the same register as the input interval. |
| 1115 | // TODO: Ideally we should just produce correct intervals in liveness analysis. |
| 1116 | // We would need to refactor the current live interval layout to do so, which is |
| 1117 | // no small task. |
| 1118 | static bool CheckInputOutputCanOverlap(InterferenceNode* in_node, InterferenceNode* out_node) { |
| 1119 | LiveInterval* output_interval = out_node->GetInterval(); |
| 1120 | HInstruction* defined_by = output_interval->GetDefinedBy(); |
| 1121 | if (defined_by == nullptr) { |
| 1122 | // This must not be a definition point. |
| 1123 | return false; |
| 1124 | } |
Andreas Gampe | 6f61ee5 | 2016-08-12 06:33:15 +0000 | [diff] [blame] | 1125 | |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1126 | LocationSummary* locations = defined_by->GetLocations(); |
| 1127 | if (locations->OutputCanOverlapWithInputs()) { |
| 1128 | // This instruction does not allow the output to reuse a register from an input. |
| 1129 | return false; |
| 1130 | } |
| 1131 | |
| 1132 | LiveInterval* input_interval = in_node->GetInterval(); |
| 1133 | LiveInterval* next_sibling = input_interval->GetNextSibling(); |
| 1134 | size_t def_position = defined_by->GetLifetimePosition(); |
| 1135 | size_t use_position = def_position + 1; |
| 1136 | if (next_sibling != nullptr && next_sibling->GetStart() == use_position) { |
| 1137 | // The next sibling starts at the use position, so reusing the input register in the output |
| 1138 | // would clobber the input before it's moved into the sibling interval location. |
| 1139 | return false; |
| 1140 | } |
| 1141 | |
| 1142 | if (!input_interval->IsDeadAt(use_position) && input_interval->CoversSlow(use_position)) { |
| 1143 | // The input interval is live after the use position. |
| 1144 | return false; |
| 1145 | } |
| 1146 | |
| 1147 | HInputsRef inputs = defined_by->GetInputs(); |
| 1148 | for (size_t i = 0; i < inputs.size(); ++i) { |
| 1149 | if (inputs[i]->GetLiveInterval()->GetSiblingAt(def_position) == input_interval) { |
| 1150 | DCHECK(input_interval->SameRegisterKind(*output_interval)); |
| 1151 | return true; |
| 1152 | } |
| 1153 | } |
| 1154 | |
| 1155 | // The input interval was not an input for this instruction. |
| 1156 | return false; |
| 1157 | } |
| 1158 | |
| 1159 | void ColoringIteration::BuildInterferenceGraph( |
| 1160 | const ArenaVector<LiveInterval*>& intervals, |
Vladimir Marko | 70e9746 | 2016-08-09 11:04:26 +0100 | [diff] [blame] | 1161 | const ArenaVector<InterferenceNode*>& physical_nodes) { |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1162 | DCHECK(interval_node_map_.Empty() && prunable_nodes_.empty()); |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 1163 | // Build the interference graph efficiently by ordering range endpoints |
| 1164 | // by position and doing a linear sweep to find interferences. (That is, we |
| 1165 | // jump from endpoint to endpoint, maintaining a set of intervals live at each |
| 1166 | // point. If two nodes are ever in the live set at the same time, then they |
| 1167 | // interfere with each other.) |
| 1168 | // |
| 1169 | // We order by both position and (secondarily) by whether the endpoint |
| 1170 | // begins or ends a range; we want to process range endings before range |
| 1171 | // beginnings at the same position because they should not conflict. |
| 1172 | // |
| 1173 | // For simplicity, we create a tuple for each endpoint, and then sort the tuples. |
| 1174 | // Tuple contents: (position, is_range_beginning, node). |
| 1175 | ArenaVector<std::tuple<size_t, bool, InterferenceNode*>> range_endpoints( |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1176 | allocator_->Adapter(kArenaAllocRegisterAllocator)); |
| 1177 | |
| 1178 | // We reserve plenty of space to avoid excessive copying. |
| 1179 | range_endpoints.reserve(4 * prunable_nodes_.size()); |
| 1180 | |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 1181 | for (LiveInterval* parent : intervals) { |
| 1182 | for (LiveInterval* sibling = parent; sibling != nullptr; sibling = sibling->GetNextSibling()) { |
| 1183 | LiveRange* range = sibling->GetFirstRange(); |
| 1184 | if (range != nullptr) { |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1185 | InterferenceNode* node = new (allocator_) InterferenceNode( |
| 1186 | allocator_, sibling, register_allocator_->liveness_); |
| 1187 | interval_node_map_.Insert(std::make_pair(sibling, node)); |
| 1188 | |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 1189 | if (sibling->HasRegister()) { |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1190 | // Fixed nodes should alias the canonical node for the corresponding register. |
| 1191 | node->stage = NodeStage::kPrecolored; |
| 1192 | InterferenceNode* physical_node = physical_nodes[sibling->GetRegister()]; |
| 1193 | node->SetAlias(physical_node); |
| 1194 | DCHECK_EQ(node->GetInterval()->GetRegister(), |
| 1195 | physical_node->GetInterval()->GetRegister()); |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 1196 | } else { |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1197 | node->stage = NodeStage::kPrunable; |
| 1198 | prunable_nodes_.push_back(node); |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 1199 | } |
| 1200 | |
| 1201 | while (range != nullptr) { |
| 1202 | range_endpoints.push_back(std::make_tuple(range->GetStart(), true, node)); |
| 1203 | range_endpoints.push_back(std::make_tuple(range->GetEnd(), false, node)); |
| 1204 | range = range->GetNext(); |
| 1205 | } |
| 1206 | } |
| 1207 | } |
| 1208 | } |
| 1209 | |
| 1210 | // Sort the endpoints. |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1211 | // We explicitly ignore the third entry of each tuple (the node pointer) in order |
| 1212 | // to maintain determinism. |
| 1213 | std::sort(range_endpoints.begin(), range_endpoints.end(), |
| 1214 | [] (const std::tuple<size_t, bool, InterferenceNode*>& lhs, |
| 1215 | const std::tuple<size_t, bool, InterferenceNode*>& rhs) { |
| 1216 | return std::tie(std::get<0>(lhs), std::get<1>(lhs)) |
| 1217 | < std::tie(std::get<0>(rhs), std::get<1>(rhs)); |
| 1218 | }); |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 1219 | |
| 1220 | // Nodes live at the current position in the linear sweep. |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1221 | ArenaVector<InterferenceNode*> live( |
| 1222 | allocator_->Adapter(kArenaAllocRegisterAllocator)); |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 1223 | |
| 1224 | // Linear sweep. When we encounter the beginning of a range, we add the corresponding node to the |
| 1225 | // live set. When we encounter the end of a range, we remove the corresponding node |
| 1226 | // from the live set. Nodes interfere if they are in the live set at the same time. |
| 1227 | for (auto it = range_endpoints.begin(); it != range_endpoints.end(); ++it) { |
| 1228 | bool is_range_beginning; |
| 1229 | InterferenceNode* node; |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1230 | size_t position; |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 1231 | // Extract information from the tuple, including the node this tuple represents. |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1232 | std::tie(position, is_range_beginning, node) = *it; |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 1233 | |
| 1234 | if (is_range_beginning) { |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1235 | bool guaranteed_not_interfering_yet = position == node->GetInterval()->GetStart(); |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 1236 | for (InterferenceNode* conflicting : live) { |
| 1237 | DCHECK_NE(node, conflicting); |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1238 | if (CheckInputOutputCanOverlap(conflicting, node)) { |
| 1239 | // We do not add an interference, because the instruction represented by `node` allows |
| 1240 | // its output to share a register with an input, represented here by `conflicting`. |
| 1241 | } else { |
| 1242 | AddPotentialInterference(node, conflicting, guaranteed_not_interfering_yet); |
| 1243 | } |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 1244 | } |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1245 | DCHECK(std::find(live.begin(), live.end(), node) == live.end()); |
| 1246 | live.push_back(node); |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 1247 | } else { |
| 1248 | // End of range. |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1249 | auto live_it = std::find(live.begin(), live.end(), node); |
| 1250 | DCHECK(live_it != live.end()); |
| 1251 | live.erase(live_it); |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 1252 | } |
| 1253 | } |
| 1254 | DCHECK(live.empty()); |
| 1255 | } |
| 1256 | |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1257 | void ColoringIteration::CreateCoalesceOpportunity(InterferenceNode* a, |
| 1258 | InterferenceNode* b, |
| 1259 | CoalesceKind kind, |
| 1260 | size_t position) { |
| 1261 | DCHECK_EQ(a->IsPair(), b->IsPair()) |
| 1262 | << "Nodes of different memory widths should never be coalesced"; |
| 1263 | CoalesceOpportunity* opportunity = |
| 1264 | new (allocator_) CoalesceOpportunity(a, b, kind, position, register_allocator_->liveness_); |
| 1265 | a->AddCoalesceOpportunity(opportunity); |
| 1266 | b->AddCoalesceOpportunity(opportunity); |
| 1267 | coalesce_worklist_.push(opportunity); |
Matthew Gharrity | 465ed69 | 2016-07-22 08:52:13 -0700 | [diff] [blame] | 1268 | } |
| 1269 | |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1270 | // When looking for coalesce opportunities, we use the interval_node_map_ to find the node |
| 1271 | // corresponding to an interval. Note that not all intervals are in this map, notably the parents |
| 1272 | // of constants and stack arguments. (However, these interval should not be involved in coalesce |
| 1273 | // opportunities anyway, because they're not going to be in registers.) |
| 1274 | void ColoringIteration::FindCoalesceOpportunities() { |
| 1275 | DCHECK(coalesce_worklist_.empty()); |
| 1276 | |
| 1277 | for (InterferenceNode* node : prunable_nodes_) { |
| 1278 | LiveInterval* interval = node->GetInterval(); |
| 1279 | |
| 1280 | // Coalesce siblings. |
| 1281 | LiveInterval* next_sibling = interval->GetNextSibling(); |
| 1282 | if (next_sibling != nullptr && interval->GetEnd() == next_sibling->GetStart()) { |
| 1283 | auto it = interval_node_map_.Find(next_sibling); |
| 1284 | if (it != interval_node_map_.end()) { |
| 1285 | InterferenceNode* sibling_node = it->second; |
| 1286 | CreateCoalesceOpportunity(node, |
| 1287 | sibling_node, |
| 1288 | CoalesceKind::kAdjacentSibling, |
| 1289 | interval->GetEnd()); |
| 1290 | } |
| 1291 | } |
| 1292 | |
| 1293 | // Coalesce fixed outputs with this interval if this interval is an adjacent sibling. |
| 1294 | LiveInterval* parent = interval->GetParent(); |
| 1295 | if (parent->HasRegister() |
| 1296 | && parent->GetNextSibling() == interval |
| 1297 | && parent->GetEnd() == interval->GetStart()) { |
| 1298 | auto it = interval_node_map_.Find(parent); |
| 1299 | if (it != interval_node_map_.end()) { |
| 1300 | InterferenceNode* parent_node = it->second; |
| 1301 | CreateCoalesceOpportunity(node, |
| 1302 | parent_node, |
| 1303 | CoalesceKind::kFixedOutputSibling, |
| 1304 | parent->GetEnd()); |
| 1305 | } |
| 1306 | } |
| 1307 | |
| 1308 | // Try to prevent moves across blocks. |
| 1309 | // Note that this does not lead to many succeeding coalesce attempts, so could be removed |
| 1310 | // if found to add to compile time. |
| 1311 | const SsaLivenessAnalysis& liveness = register_allocator_->liveness_; |
| 1312 | if (interval->IsSplit() && liveness.IsAtBlockBoundary(interval->GetStart() / 2)) { |
| 1313 | // If the start of this interval is at a block boundary, we look at the |
| 1314 | // location of the interval in blocks preceding the block this interval |
| 1315 | // starts at. This can avoid a move between the two blocks. |
| 1316 | HBasicBlock* block = liveness.GetBlockFromPosition(interval->GetStart() / 2); |
| 1317 | for (HBasicBlock* predecessor : block->GetPredecessors()) { |
| 1318 | size_t position = predecessor->GetLifetimeEnd() - 1; |
| 1319 | LiveInterval* existing = interval->GetParent()->GetSiblingAt(position); |
| 1320 | if (existing != nullptr) { |
| 1321 | auto it = interval_node_map_.Find(existing); |
| 1322 | if (it != interval_node_map_.end()) { |
| 1323 | InterferenceNode* existing_node = it->second; |
| 1324 | CreateCoalesceOpportunity(node, |
| 1325 | existing_node, |
| 1326 | CoalesceKind::kNonlinearControlFlow, |
| 1327 | position); |
| 1328 | } |
| 1329 | } |
| 1330 | } |
| 1331 | } |
| 1332 | |
| 1333 | // Coalesce phi inputs with the corresponding output. |
| 1334 | HInstruction* defined_by = interval->GetDefinedBy(); |
| 1335 | if (defined_by != nullptr && defined_by->IsPhi()) { |
| 1336 | const ArenaVector<HBasicBlock*>& predecessors = defined_by->GetBlock()->GetPredecessors(); |
| 1337 | HInputsRef inputs = defined_by->GetInputs(); |
| 1338 | |
| 1339 | for (size_t i = 0, e = inputs.size(); i < e; ++i) { |
| 1340 | // We want the sibling at the end of the appropriate predecessor block. |
| 1341 | size_t position = predecessors[i]->GetLifetimeEnd() - 1; |
| 1342 | LiveInterval* input_interval = inputs[i]->GetLiveInterval()->GetSiblingAt(position); |
| 1343 | |
| 1344 | auto it = interval_node_map_.Find(input_interval); |
| 1345 | if (it != interval_node_map_.end()) { |
| 1346 | InterferenceNode* input_node = it->second; |
| 1347 | CreateCoalesceOpportunity(node, input_node, CoalesceKind::kPhi, position); |
| 1348 | } |
| 1349 | } |
| 1350 | } |
| 1351 | |
| 1352 | // Coalesce output with first input when policy is kSameAsFirstInput. |
| 1353 | if (defined_by != nullptr) { |
| 1354 | Location out = defined_by->GetLocations()->Out(); |
| 1355 | if (out.IsUnallocated() && out.GetPolicy() == Location::kSameAsFirstInput) { |
| 1356 | LiveInterval* input_interval |
| 1357 | = defined_by->InputAt(0)->GetLiveInterval()->GetSiblingAt(interval->GetStart() - 1); |
| 1358 | // TODO: Could we consider lifetime holes here? |
| 1359 | if (input_interval->GetEnd() == interval->GetStart()) { |
| 1360 | auto it = interval_node_map_.Find(input_interval); |
| 1361 | if (it != interval_node_map_.end()) { |
| 1362 | InterferenceNode* input_node = it->second; |
| 1363 | CreateCoalesceOpportunity(node, |
| 1364 | input_node, |
| 1365 | CoalesceKind::kFirstInput, |
| 1366 | interval->GetStart()); |
| 1367 | } |
| 1368 | } |
| 1369 | } |
| 1370 | } |
| 1371 | |
| 1372 | // An interval that starts an instruction (that is, it is not split), may |
| 1373 | // re-use the registers used by the inputs of that instruction, based on the |
| 1374 | // location summary. |
| 1375 | if (defined_by != nullptr) { |
| 1376 | DCHECK(!interval->IsSplit()); |
| 1377 | LocationSummary* locations = defined_by->GetLocations(); |
| 1378 | if (!locations->OutputCanOverlapWithInputs()) { |
| 1379 | HInputsRef inputs = defined_by->GetInputs(); |
| 1380 | for (size_t i = 0; i < inputs.size(); ++i) { |
| 1381 | size_t def_point = defined_by->GetLifetimePosition(); |
| 1382 | // TODO: Getting the sibling at the def_point might not be quite what we want |
| 1383 | // for fixed inputs, since the use will be *at* the def_point rather than after. |
| 1384 | LiveInterval* input_interval = inputs[i]->GetLiveInterval()->GetSiblingAt(def_point); |
| 1385 | if (input_interval != nullptr && |
| 1386 | input_interval->HasHighInterval() == interval->HasHighInterval()) { |
| 1387 | auto it = interval_node_map_.Find(input_interval); |
| 1388 | if (it != interval_node_map_.end()) { |
| 1389 | InterferenceNode* input_node = it->second; |
| 1390 | CreateCoalesceOpportunity(node, |
| 1391 | input_node, |
| 1392 | CoalesceKind::kAnyInput, |
| 1393 | interval->GetStart()); |
| 1394 | } |
| 1395 | } |
| 1396 | } |
| 1397 | } |
| 1398 | } |
| 1399 | |
| 1400 | // Try to prevent moves into fixed input locations. |
| 1401 | UsePosition* use = interval->GetFirstUse(); |
| 1402 | for (; use != nullptr && use->GetPosition() <= interval->GetStart(); use = use->GetNext()) { |
| 1403 | // Skip past uses before the start of this interval. |
| 1404 | } |
| 1405 | for (; use != nullptr && use->GetPosition() <= interval->GetEnd(); use = use->GetNext()) { |
| 1406 | HInstruction* user = use->GetUser(); |
| 1407 | if (user == nullptr) { |
| 1408 | // User may be null for certain intervals, such as temp intervals. |
| 1409 | continue; |
| 1410 | } |
| 1411 | LocationSummary* locations = user->GetLocations(); |
| 1412 | Location input = locations->InAt(use->GetInputIndex()); |
| 1413 | if (input.IsRegister() || input.IsFpuRegister()) { |
| 1414 | // TODO: Could try to handle pair interval too, but coalescing with fixed pair nodes |
| 1415 | // is currently not supported. |
| 1416 | InterferenceNode* fixed_node = input.IsRegister() |
| 1417 | ? register_allocator_->physical_core_nodes_[input.reg()] |
| 1418 | : register_allocator_->physical_fp_nodes_[input.reg()]; |
| 1419 | CreateCoalesceOpportunity(node, |
| 1420 | fixed_node, |
| 1421 | CoalesceKind::kFixedInput, |
| 1422 | user->GetLifetimePosition()); |
| 1423 | } |
| 1424 | } |
| 1425 | } // for node in prunable_nodes |
| 1426 | } |
| 1427 | |
| 1428 | static bool IsLowDegreeNode(InterferenceNode* node, size_t num_regs) { |
| 1429 | return node->GetOutDegree() < num_regs; |
| 1430 | } |
| 1431 | |
| 1432 | static bool IsHighDegreeNode(InterferenceNode* node, size_t num_regs) { |
| 1433 | return !IsLowDegreeNode(node, num_regs); |
| 1434 | } |
| 1435 | |
| 1436 | void ColoringIteration::PruneInterferenceGraph() { |
| 1437 | DCHECK(pruned_nodes_.empty() |
| 1438 | && simplify_worklist_.empty() |
| 1439 | && freeze_worklist_.empty() |
| 1440 | && spill_worklist_.empty()); |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 1441 | // When pruning the graph, we refer to nodes with degree less than num_regs as low degree nodes, |
| 1442 | // and all others as high degree nodes. The distinction is important: low degree nodes are |
| 1443 | // guaranteed a color, while high degree nodes are not. |
| 1444 | |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1445 | // Build worklists. Note that the coalesce worklist has already been |
| 1446 | // filled by FindCoalesceOpportunities(). |
| 1447 | for (InterferenceNode* node : prunable_nodes_) { |
| 1448 | DCHECK(!node->IsPrecolored()) << "Fixed nodes should never be pruned"; |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1449 | if (IsLowDegreeNode(node, num_regs_)) { |
| 1450 | if (node->GetCoalesceOpportunities().empty()) { |
| 1451 | // Simplify Worklist. |
| 1452 | node->stage = NodeStage::kSimplifyWorklist; |
| 1453 | simplify_worklist_.push_back(node); |
| 1454 | } else { |
| 1455 | // Freeze Worklist. |
| 1456 | node->stage = NodeStage::kFreezeWorklist; |
| 1457 | freeze_worklist_.push_back(node); |
| 1458 | } |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 1459 | } else { |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1460 | // Spill worklist. |
| 1461 | node->stage = NodeStage::kSpillWorklist; |
| 1462 | spill_worklist_.push(node); |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 1463 | } |
| 1464 | } |
| 1465 | |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1466 | // Prune graph. |
| 1467 | // Note that we do not remove a node from its current worklist if it moves to another, so it may |
| 1468 | // be in multiple worklists at once; the node's `phase` says which worklist it is really in. |
| 1469 | while (true) { |
| 1470 | if (!simplify_worklist_.empty()) { |
| 1471 | // Prune low-degree nodes. |
| 1472 | // TODO: pop_back() should work as well, but it didn't; we get a |
| 1473 | // failed check while pruning. We should look into this. |
| 1474 | InterferenceNode* node = simplify_worklist_.front(); |
| 1475 | simplify_worklist_.pop_front(); |
| 1476 | DCHECK_EQ(node->stage, NodeStage::kSimplifyWorklist) << "Cannot move from simplify list"; |
| 1477 | DCHECK_LT(node->GetOutDegree(), num_regs_) << "Nodes in simplify list should be low degree"; |
| 1478 | DCHECK(!node->IsMoveRelated()) << "Nodes in simplify list should not be move related"; |
| 1479 | PruneNode(node); |
| 1480 | } else if (!coalesce_worklist_.empty()) { |
| 1481 | // Coalesce. |
| 1482 | CoalesceOpportunity* opportunity = coalesce_worklist_.top(); |
| 1483 | coalesce_worklist_.pop(); |
| 1484 | if (opportunity->stage == CoalesceStage::kWorklist) { |
| 1485 | Coalesce(opportunity); |
| 1486 | } |
| 1487 | } else if (!freeze_worklist_.empty()) { |
| 1488 | // Freeze moves and prune a low-degree move-related node. |
| 1489 | InterferenceNode* node = freeze_worklist_.front(); |
| 1490 | freeze_worklist_.pop_front(); |
| 1491 | if (node->stage == NodeStage::kFreezeWorklist) { |
| 1492 | DCHECK_LT(node->GetOutDegree(), num_regs_) << "Nodes in freeze list should be low degree"; |
| 1493 | DCHECK(node->IsMoveRelated()) << "Nodes in freeze list should be move related"; |
| 1494 | FreezeMoves(node); |
| 1495 | PruneNode(node); |
| 1496 | } |
| 1497 | } else if (!spill_worklist_.empty()) { |
| 1498 | // We spill the lowest-priority node, because pruning a node earlier |
| 1499 | // gives it a higher chance of being spilled. |
| 1500 | InterferenceNode* node = spill_worklist_.top(); |
| 1501 | spill_worklist_.pop(); |
| 1502 | if (node->stage == NodeStage::kSpillWorklist) { |
| 1503 | DCHECK_GE(node->GetOutDegree(), num_regs_) << "Nodes in spill list should be high degree"; |
| 1504 | FreezeMoves(node); |
| 1505 | PruneNode(node); |
| 1506 | } |
| 1507 | } else { |
| 1508 | // Pruning complete. |
| 1509 | break; |
| 1510 | } |
| 1511 | } |
| 1512 | DCHECK_EQ(prunable_nodes_.size(), pruned_nodes_.size()); |
| 1513 | } |
| 1514 | |
| 1515 | void ColoringIteration::EnableCoalesceOpportunities(InterferenceNode* node) { |
| 1516 | for (CoalesceOpportunity* opportunity : node->GetCoalesceOpportunities()) { |
| 1517 | if (opportunity->stage == CoalesceStage::kActive) { |
| 1518 | opportunity->stage = CoalesceStage::kWorklist; |
| 1519 | coalesce_worklist_.push(opportunity); |
| 1520 | } |
| 1521 | } |
| 1522 | } |
| 1523 | |
| 1524 | void ColoringIteration::PruneNode(InterferenceNode* node) { |
| 1525 | DCHECK_NE(node->stage, NodeStage::kPruned); |
| 1526 | DCHECK(!node->IsPrecolored()); |
| 1527 | node->stage = NodeStage::kPruned; |
| 1528 | pruned_nodes_.push(node); |
| 1529 | |
| 1530 | for (InterferenceNode* adj : node->GetAdjacentNodes()) { |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1531 | DCHECK_NE(adj->stage, NodeStage::kPruned) << "Should be no interferences with pruned nodes"; |
| 1532 | |
| 1533 | if (adj->IsPrecolored()) { |
| 1534 | // No effect on pre-colored nodes; they're never pruned. |
| 1535 | } else { |
| 1536 | // Remove the interference. |
| 1537 | bool was_high_degree = IsHighDegreeNode(adj, num_regs_); |
| 1538 | DCHECK(adj->ContainsInterference(node)) |
| 1539 | << "Missing reflexive interference from non-fixed node"; |
| 1540 | adj->RemoveInterference(node); |
| 1541 | |
| 1542 | // Handle transitions from high degree to low degree. |
| 1543 | if (was_high_degree && IsLowDegreeNode(adj, num_regs_)) { |
| 1544 | EnableCoalesceOpportunities(adj); |
| 1545 | for (InterferenceNode* adj_adj : adj->GetAdjacentNodes()) { |
| 1546 | EnableCoalesceOpportunities(adj_adj); |
| 1547 | } |
| 1548 | |
| 1549 | DCHECK_EQ(adj->stage, NodeStage::kSpillWorklist); |
| 1550 | if (adj->IsMoveRelated()) { |
| 1551 | adj->stage = NodeStage::kFreezeWorklist; |
| 1552 | freeze_worklist_.push_back(adj); |
| 1553 | } else { |
| 1554 | adj->stage = NodeStage::kSimplifyWorklist; |
| 1555 | simplify_worklist_.push_back(adj); |
Andreas Gampe | 6f61ee5 | 2016-08-12 06:33:15 +0000 | [diff] [blame] | 1556 | } |
| 1557 | } |
| 1558 | } |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1559 | } |
| 1560 | } |
Andreas Gampe | 6f61ee5 | 2016-08-12 06:33:15 +0000 | [diff] [blame] | 1561 | |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1562 | void ColoringIteration::CheckTransitionFromFreezeWorklist(InterferenceNode* node) { |
| 1563 | if (IsLowDegreeNode(node, num_regs_) && !node->IsMoveRelated()) { |
| 1564 | DCHECK_EQ(node->stage, NodeStage::kFreezeWorklist); |
| 1565 | node->stage = NodeStage::kSimplifyWorklist; |
| 1566 | simplify_worklist_.push_back(node); |
| 1567 | } |
| 1568 | } |
| 1569 | |
| 1570 | void ColoringIteration::FreezeMoves(InterferenceNode* node) { |
| 1571 | for (CoalesceOpportunity* opportunity : node->GetCoalesceOpportunities()) { |
| 1572 | if (opportunity->stage == CoalesceStage::kDefunct) { |
| 1573 | // Constrained moves should remain constrained, since they will not be considered |
| 1574 | // during last-chance coalescing. |
| 1575 | } else { |
| 1576 | opportunity->stage = CoalesceStage::kInactive; |
Andreas Gampe | 6f61ee5 | 2016-08-12 06:33:15 +0000 | [diff] [blame] | 1577 | } |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1578 | InterferenceNode* other = opportunity->node_a->GetAlias() == node |
| 1579 | ? opportunity->node_b->GetAlias() |
| 1580 | : opportunity->node_a->GetAlias(); |
| 1581 | if (other != node && other->stage == NodeStage::kFreezeWorklist) { |
| 1582 | DCHECK(IsLowDegreeNode(node, num_regs_)); |
| 1583 | CheckTransitionFromFreezeWorklist(other); |
Matthew Gharrity | 465ed69 | 2016-07-22 08:52:13 -0700 | [diff] [blame] | 1584 | } |
| 1585 | } |
Matthew Gharrity | 465ed69 | 2016-07-22 08:52:13 -0700 | [diff] [blame] | 1586 | } |
| 1587 | |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1588 | bool ColoringIteration::PrecoloredHeuristic(InterferenceNode* from, |
| 1589 | InterferenceNode* into) { |
| 1590 | if (!into->IsPrecolored()) { |
| 1591 | // The uncolored heuristic will cover this case. |
| 1592 | return false; |
| 1593 | } |
| 1594 | if (from->IsPair() || into->IsPair()) { |
| 1595 | // TODO: Merging from a pair node is currently not supported, since fixed pair nodes |
| 1596 | // are currently represented as two single fixed nodes in the graph, and `into` is |
| 1597 | // only one of them. (We may lose the implicit connections to the second one in a merge.) |
| 1598 | return false; |
| 1599 | } |
| 1600 | |
| 1601 | // If all adjacent nodes of `from` are "ok", then we can conservatively merge with `into`. |
| 1602 | // Reasons an adjacent node `adj` can be "ok": |
| 1603 | // (1) If `adj` is low degree, interference with `into` will not affect its existing |
| 1604 | // colorable guarantee. (Notice that coalescing cannot increase its degree.) |
| 1605 | // (2) If `adj` is pre-colored, it already interferes with `into`. See (3). |
| 1606 | // (3) If there's already an interference with `into`, coalescing will not add interferences. |
| 1607 | for (InterferenceNode* adj : from->GetAdjacentNodes()) { |
| 1608 | if (IsLowDegreeNode(adj, num_regs_) || adj->IsPrecolored() || adj->ContainsInterference(into)) { |
| 1609 | // Ok. |
| 1610 | } else { |
| 1611 | return false; |
| 1612 | } |
| 1613 | } |
| 1614 | return true; |
| 1615 | } |
| 1616 | |
| 1617 | bool ColoringIteration::UncoloredHeuristic(InterferenceNode* from, |
| 1618 | InterferenceNode* into) { |
| 1619 | if (into->IsPrecolored()) { |
| 1620 | // The pre-colored heuristic will handle this case. |
| 1621 | return false; |
| 1622 | } |
| 1623 | |
| 1624 | // Arbitrary cap to improve compile time. Tests show that this has negligible affect |
| 1625 | // on generated code. |
| 1626 | if (from->GetOutDegree() + into->GetOutDegree() > 2 * num_regs_) { |
| 1627 | return false; |
| 1628 | } |
| 1629 | |
| 1630 | // It's safe to coalesce two nodes if the resulting node has fewer than `num_regs` neighbors |
| 1631 | // of high degree. (Low degree neighbors can be ignored, because they will eventually be |
| 1632 | // pruned from the interference graph in the simplify stage.) |
| 1633 | size_t high_degree_interferences = 0; |
| 1634 | for (InterferenceNode* adj : from->GetAdjacentNodes()) { |
| 1635 | if (IsHighDegreeNode(adj, num_regs_)) { |
| 1636 | high_degree_interferences += from->EdgeWeightWith(adj); |
| 1637 | } |
| 1638 | } |
| 1639 | for (InterferenceNode* adj : into->GetAdjacentNodes()) { |
| 1640 | if (IsHighDegreeNode(adj, num_regs_)) { |
| 1641 | if (from->ContainsInterference(adj)) { |
| 1642 | // We've already counted this adjacent node. |
| 1643 | // Furthermore, its degree will decrease if coalescing succeeds. Thus, it's possible that |
| 1644 | // we should not have counted it at all. (This extends the textbook Briggs coalescing test, |
| 1645 | // but remains conservative.) |
| 1646 | if (adj->GetOutDegree() - into->EdgeWeightWith(adj) < num_regs_) { |
| 1647 | high_degree_interferences -= from->EdgeWeightWith(adj); |
| 1648 | } |
| 1649 | } else { |
| 1650 | high_degree_interferences += into->EdgeWeightWith(adj); |
| 1651 | } |
| 1652 | } |
| 1653 | } |
| 1654 | |
| 1655 | return high_degree_interferences < num_regs_; |
| 1656 | } |
| 1657 | |
| 1658 | void ColoringIteration::Combine(InterferenceNode* from, |
| 1659 | InterferenceNode* into) { |
| 1660 | from->SetAlias(into); |
| 1661 | |
| 1662 | // Add interferences. |
| 1663 | for (InterferenceNode* adj : from->GetAdjacentNodes()) { |
| 1664 | bool was_low_degree = IsLowDegreeNode(adj, num_regs_); |
| 1665 | AddPotentialInterference(adj, into, /*guaranteed_not_interfering_yet*/ false); |
| 1666 | if (was_low_degree && IsHighDegreeNode(adj, num_regs_)) { |
| 1667 | // This is a (temporary) transition to a high degree node. Its degree will decrease again |
| 1668 | // when we prune `from`, but it's best to be consistent about the current worklist. |
| 1669 | adj->stage = NodeStage::kSpillWorklist; |
| 1670 | spill_worklist_.push(adj); |
| 1671 | } |
| 1672 | } |
| 1673 | |
| 1674 | // Add coalesce opportunities. |
| 1675 | for (CoalesceOpportunity* opportunity : from->GetCoalesceOpportunities()) { |
| 1676 | if (opportunity->stage != CoalesceStage::kDefunct) { |
| 1677 | into->AddCoalesceOpportunity(opportunity); |
| 1678 | } |
| 1679 | } |
| 1680 | EnableCoalesceOpportunities(from); |
| 1681 | |
| 1682 | // Prune and update worklists. |
| 1683 | PruneNode(from); |
| 1684 | if (IsLowDegreeNode(into, num_regs_)) { |
| 1685 | // Coalesce(...) takes care of checking for a transition to the simplify worklist. |
| 1686 | DCHECK_EQ(into->stage, NodeStage::kFreezeWorklist); |
| 1687 | } else if (into->stage == NodeStage::kFreezeWorklist) { |
| 1688 | // This is a transition to a high degree node. |
| 1689 | into->stage = NodeStage::kSpillWorklist; |
| 1690 | spill_worklist_.push(into); |
| 1691 | } else { |
| 1692 | DCHECK(into->stage == NodeStage::kSpillWorklist || into->stage == NodeStage::kPrecolored); |
| 1693 | } |
| 1694 | } |
| 1695 | |
| 1696 | void ColoringIteration::Coalesce(CoalesceOpportunity* opportunity) { |
| 1697 | InterferenceNode* from = opportunity->node_a->GetAlias(); |
| 1698 | InterferenceNode* into = opportunity->node_b->GetAlias(); |
| 1699 | DCHECK_NE(from->stage, NodeStage::kPruned); |
| 1700 | DCHECK_NE(into->stage, NodeStage::kPruned); |
| 1701 | |
| 1702 | if (from->IsPrecolored()) { |
| 1703 | // If we have one pre-colored node, make sure it's the `into` node. |
| 1704 | std::swap(from, into); |
| 1705 | } |
| 1706 | |
| 1707 | if (from == into) { |
| 1708 | // These nodes have already been coalesced. |
| 1709 | opportunity->stage = CoalesceStage::kDefunct; |
| 1710 | CheckTransitionFromFreezeWorklist(from); |
| 1711 | } else if (from->IsPrecolored() || from->ContainsInterference(into)) { |
| 1712 | // These nodes interfere. |
| 1713 | opportunity->stage = CoalesceStage::kDefunct; |
| 1714 | CheckTransitionFromFreezeWorklist(from); |
| 1715 | CheckTransitionFromFreezeWorklist(into); |
| 1716 | } else if (PrecoloredHeuristic(from, into) |
| 1717 | || UncoloredHeuristic(from, into)) { |
| 1718 | // We can coalesce these nodes. |
| 1719 | opportunity->stage = CoalesceStage::kDefunct; |
| 1720 | Combine(from, into); |
| 1721 | CheckTransitionFromFreezeWorklist(into); |
| 1722 | } else { |
| 1723 | // We cannot coalesce, but we may be able to later. |
| 1724 | opportunity->stage = CoalesceStage::kActive; |
| 1725 | } |
| 1726 | } |
| 1727 | |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 1728 | // Build a mask with a bit set for each register assigned to some |
| 1729 | // interval in `intervals`. |
| 1730 | template <typename Container> |
| 1731 | static std::bitset<kMaxNumRegs> BuildConflictMask(Container& intervals) { |
| 1732 | std::bitset<kMaxNumRegs> conflict_mask; |
| 1733 | for (InterferenceNode* adjacent : intervals) { |
| 1734 | LiveInterval* conflicting = adjacent->GetInterval(); |
| 1735 | if (conflicting->HasRegister()) { |
| 1736 | conflict_mask.set(conflicting->GetRegister()); |
| 1737 | if (conflicting->HasHighInterval()) { |
| 1738 | DCHECK(conflicting->GetHighInterval()->HasRegister()); |
| 1739 | conflict_mask.set(conflicting->GetHighInterval()->GetRegister()); |
| 1740 | } |
| 1741 | } else { |
| 1742 | DCHECK(!conflicting->HasHighInterval() |
| 1743 | || !conflicting->GetHighInterval()->HasRegister()); |
| 1744 | } |
| 1745 | } |
| 1746 | return conflict_mask; |
| 1747 | } |
| 1748 | |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1749 | bool RegisterAllocatorGraphColor::IsCallerSave(size_t reg, bool processing_core_regs) { |
| 1750 | return processing_core_regs |
| 1751 | ? !codegen_->IsCoreCalleeSaveRegister(reg) |
Matthew Gharrity | 8a4252e | 2016-08-15 07:56:41 -0700 | [diff] [blame] | 1752 | : !codegen_->IsFloatingPointCalleeSaveRegister(reg); |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1753 | } |
| 1754 | |
| 1755 | static bool RegisterIsAligned(size_t reg) { |
| 1756 | return reg % 2 == 0; |
| 1757 | } |
| 1758 | |
| 1759 | static size_t FindFirstZeroInConflictMask(std::bitset<kMaxNumRegs> conflict_mask) { |
| 1760 | // We use CTZ (count trailing zeros) to quickly find the lowest 0 bit. |
| 1761 | // Note that CTZ is undefined if all bits are 0, so we special-case it. |
| 1762 | return conflict_mask.all() ? conflict_mask.size() : CTZ(~conflict_mask.to_ulong()); |
| 1763 | } |
| 1764 | |
| 1765 | bool ColoringIteration::ColorInterferenceGraph() { |
| 1766 | DCHECK_LE(num_regs_, kMaxNumRegs) << "kMaxNumRegs is too small"; |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 1767 | ArenaVector<LiveInterval*> colored_intervals( |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1768 | allocator_->Adapter(kArenaAllocRegisterAllocator)); |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 1769 | bool successful = true; |
| 1770 | |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1771 | while (!pruned_nodes_.empty()) { |
| 1772 | InterferenceNode* node = pruned_nodes_.top(); |
| 1773 | pruned_nodes_.pop(); |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 1774 | LiveInterval* interval = node->GetInterval(); |
Andreas Gampe | 6f61ee5 | 2016-08-12 06:33:15 +0000 | [diff] [blame] | 1775 | size_t reg = 0; |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1776 | |
| 1777 | InterferenceNode* alias = node->GetAlias(); |
| 1778 | if (alias != node) { |
| 1779 | // This node was coalesced with another. |
| 1780 | LiveInterval* alias_interval = alias->GetInterval(); |
| 1781 | if (alias_interval->HasRegister()) { |
| 1782 | reg = alias_interval->GetRegister(); |
| 1783 | DCHECK(!BuildConflictMask(node->GetAdjacentNodes())[reg]) |
| 1784 | << "This node conflicts with the register it was coalesced with"; |
| 1785 | } else { |
| 1786 | DCHECK(false) << node->GetOutDegree() << " " << alias->GetOutDegree() << " " |
| 1787 | << "Move coalescing was not conservative, causing a node to be coalesced " |
| 1788 | << "with another node that could not be colored"; |
| 1789 | if (interval->RequiresRegister()) { |
| 1790 | successful = false; |
| 1791 | } |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 1792 | } |
| 1793 | } else { |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1794 | // Search for free register(s). |
| 1795 | std::bitset<kMaxNumRegs> conflict_mask = BuildConflictMask(node->GetAdjacentNodes()); |
| 1796 | if (interval->HasHighInterval()) { |
| 1797 | // Note that the graph coloring allocator assumes that pair intervals are aligned here, |
| 1798 | // excluding pre-colored pair intervals (which can currently be unaligned on x86). If we |
| 1799 | // change the alignment requirements here, we will have to update the algorithm (e.g., |
| 1800 | // be more conservative about the weight of edges adjacent to pair nodes.) |
| 1801 | while (reg < num_regs_ - 1 && (conflict_mask[reg] || conflict_mask[reg + 1])) { |
| 1802 | reg += 2; |
| 1803 | } |
| 1804 | |
| 1805 | // Try to use a caller-save register first. |
| 1806 | for (size_t i = 0; i < num_regs_ - 1; i += 2) { |
| 1807 | bool low_caller_save = register_allocator_->IsCallerSave(i, processing_core_regs_); |
| 1808 | bool high_caller_save = register_allocator_->IsCallerSave(i + 1, processing_core_regs_); |
| 1809 | if (!conflict_mask[i] && !conflict_mask[i + 1]) { |
| 1810 | if (low_caller_save && high_caller_save) { |
| 1811 | reg = i; |
| 1812 | break; |
| 1813 | } else if (low_caller_save || high_caller_save) { |
| 1814 | reg = i; |
| 1815 | // Keep looking to try to get both parts in caller-save registers. |
| 1816 | } |
| 1817 | } |
| 1818 | } |
| 1819 | } else { |
| 1820 | // Not a pair interval. |
| 1821 | reg = FindFirstZeroInConflictMask(conflict_mask); |
| 1822 | |
| 1823 | // Try to use caller-save registers first. |
| 1824 | for (size_t i = 0; i < num_regs_; ++i) { |
| 1825 | if (!conflict_mask[i] && register_allocator_->IsCallerSave(i, processing_core_regs_)) { |
| 1826 | reg = i; |
| 1827 | break; |
| 1828 | } |
| 1829 | } |
| 1830 | } |
| 1831 | |
| 1832 | // Last-chance coalescing. |
| 1833 | for (CoalesceOpportunity* opportunity : node->GetCoalesceOpportunities()) { |
| 1834 | if (opportunity->stage == CoalesceStage::kDefunct) { |
| 1835 | continue; |
| 1836 | } |
| 1837 | LiveInterval* other_interval = opportunity->node_a->GetAlias() == node |
| 1838 | ? opportunity->node_b->GetAlias()->GetInterval() |
| 1839 | : opportunity->node_a->GetAlias()->GetInterval(); |
| 1840 | if (other_interval->HasRegister()) { |
| 1841 | size_t coalesce_register = other_interval->GetRegister(); |
| 1842 | if (interval->HasHighInterval()) { |
| 1843 | if (!conflict_mask[coalesce_register] && |
| 1844 | !conflict_mask[coalesce_register + 1] && |
| 1845 | RegisterIsAligned(coalesce_register)) { |
| 1846 | reg = coalesce_register; |
| 1847 | break; |
| 1848 | } |
| 1849 | } else if (!conflict_mask[coalesce_register]) { |
| 1850 | reg = coalesce_register; |
| 1851 | break; |
| 1852 | } |
| 1853 | } |
| 1854 | } |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 1855 | } |
| 1856 | |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1857 | if (reg < (interval->HasHighInterval() ? num_regs_ - 1 : num_regs_)) { |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 1858 | // Assign register. |
| 1859 | DCHECK(!interval->HasRegister()); |
| 1860 | interval->SetRegister(reg); |
| 1861 | colored_intervals.push_back(interval); |
| 1862 | if (interval->HasHighInterval()) { |
| 1863 | DCHECK(!interval->GetHighInterval()->HasRegister()); |
| 1864 | interval->GetHighInterval()->SetRegister(reg + 1); |
| 1865 | colored_intervals.push_back(interval->GetHighInterval()); |
| 1866 | } |
| 1867 | } else if (interval->RequiresRegister()) { |
| 1868 | // The interference graph is too dense to color. Make it sparser by |
| 1869 | // splitting this live interval. |
| 1870 | successful = false; |
Matthew Gharrity | 2ccae4a | 2016-08-12 16:10:45 +0000 | [diff] [blame] | 1871 | register_allocator_->SplitAtRegisterUses(interval); |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 1872 | // We continue coloring, because there may be additional intervals that cannot |
| 1873 | // be colored, and that we should split. |
| 1874 | } else { |
| 1875 | // Spill. |
Matthew Gharrity | b6722ff | 2016-08-12 19:07:11 -0700 | [diff] [blame] | 1876 | node->SetNeedsSpillSlot(); |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 1877 | } |
| 1878 | } |
| 1879 | |
| 1880 | // If unsuccessful, reset all register assignments. |
| 1881 | if (!successful) { |
| 1882 | for (LiveInterval* interval : colored_intervals) { |
| 1883 | interval->ClearRegister(); |
| 1884 | } |
| 1885 | } |
| 1886 | |
| 1887 | return successful; |
| 1888 | } |
| 1889 | |
Matthew Gharrity | b6722ff | 2016-08-12 19:07:11 -0700 | [diff] [blame] | 1890 | void RegisterAllocatorGraphColor::AllocateSpillSlots(const ArenaVector<InterferenceNode*>& nodes) { |
| 1891 | // The register allocation resolver will organize the stack based on value type, |
| 1892 | // so we assign stack slots for each value type separately. |
| 1893 | ArenaVector<LiveInterval*> double_intervals(allocator_->Adapter(kArenaAllocRegisterAllocator)); |
| 1894 | ArenaVector<LiveInterval*> long_intervals(allocator_->Adapter(kArenaAllocRegisterAllocator)); |
| 1895 | ArenaVector<LiveInterval*> float_intervals(allocator_->Adapter(kArenaAllocRegisterAllocator)); |
| 1896 | ArenaVector<LiveInterval*> int_intervals(allocator_->Adapter(kArenaAllocRegisterAllocator)); |
| 1897 | |
| 1898 | // The set of parent intervals already handled. |
| 1899 | ArenaSet<LiveInterval*> seen(allocator_->Adapter(kArenaAllocRegisterAllocator)); |
| 1900 | |
| 1901 | // Find nodes that need spill slots. |
| 1902 | for (InterferenceNode* node : nodes) { |
| 1903 | if (!node->NeedsSpillSlot()) { |
| 1904 | continue; |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 1905 | } |
| 1906 | |
Matthew Gharrity | b6722ff | 2016-08-12 19:07:11 -0700 | [diff] [blame] | 1907 | LiveInterval* parent = node->GetInterval()->GetParent(); |
| 1908 | if (seen.find(parent) != seen.end()) { |
| 1909 | // We've already handled this interval. |
| 1910 | // This can happen if multiple siblings of the same interval request a stack slot. |
| 1911 | continue; |
| 1912 | } |
| 1913 | seen.insert(parent); |
| 1914 | |
| 1915 | HInstruction* defined_by = parent->GetDefinedBy(); |
| 1916 | if (parent->HasSpillSlot()) { |
| 1917 | // We already have a spill slot for this value that we can reuse. |
| 1918 | } else if (defined_by->IsParameterValue()) { |
| 1919 | // Parameters already have a stack slot. |
| 1920 | parent->SetSpillSlot(codegen_->GetStackSlotOfParameter(defined_by->AsParameterValue())); |
| 1921 | } else if (defined_by->IsCurrentMethod()) { |
| 1922 | // The current method is always at stack slot 0. |
| 1923 | parent->SetSpillSlot(0); |
| 1924 | } else if (defined_by->IsConstant()) { |
| 1925 | // Constants don't need a spill slot. |
| 1926 | } else { |
| 1927 | // We need to find a spill slot for this interval. Place it in the correct |
| 1928 | // worklist to be processed later. |
| 1929 | switch (node->GetInterval()->GetType()) { |
| 1930 | case Primitive::kPrimDouble: |
| 1931 | double_intervals.push_back(parent); |
| 1932 | break; |
| 1933 | case Primitive::kPrimLong: |
| 1934 | long_intervals.push_back(parent); |
| 1935 | break; |
| 1936 | case Primitive::kPrimFloat: |
| 1937 | float_intervals.push_back(parent); |
| 1938 | break; |
| 1939 | case Primitive::kPrimNot: |
| 1940 | case Primitive::kPrimInt: |
| 1941 | case Primitive::kPrimChar: |
| 1942 | case Primitive::kPrimByte: |
| 1943 | case Primitive::kPrimBoolean: |
| 1944 | case Primitive::kPrimShort: |
| 1945 | int_intervals.push_back(parent); |
| 1946 | break; |
| 1947 | case Primitive::kPrimVoid: |
| 1948 | LOG(FATAL) << "Unexpected type for interval " << node->GetInterval()->GetType(); |
| 1949 | UNREACHABLE(); |
| 1950 | } |
| 1951 | } |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 1952 | } |
Matthew Gharrity | b6722ff | 2016-08-12 19:07:11 -0700 | [diff] [blame] | 1953 | |
| 1954 | // Color spill slots for each value type. |
| 1955 | ColorSpillSlots(&double_intervals, &num_double_spill_slots_); |
| 1956 | ColorSpillSlots(&long_intervals, &num_long_spill_slots_); |
| 1957 | ColorSpillSlots(&float_intervals, &num_float_spill_slots_); |
| 1958 | ColorSpillSlots(&int_intervals, &num_int_spill_slots_); |
| 1959 | } |
| 1960 | |
| 1961 | void RegisterAllocatorGraphColor::ColorSpillSlots(ArenaVector<LiveInterval*>* intervals, |
| 1962 | size_t* num_stack_slots_used) { |
| 1963 | // We cannot use the original interference graph here because spill slots are assigned to |
| 1964 | // all of the siblings of an interval, whereas an interference node represents only a single |
| 1965 | // sibling. So, we assign spill slots linear-scan-style by sorting all the interval endpoints |
| 1966 | // by position, and assigning the lowest spill slot available when we encounter an interval |
| 1967 | // beginning. We ignore lifetime holes for simplicity. |
| 1968 | ArenaVector<std::tuple<size_t, bool, LiveInterval*>> interval_endpoints( |
| 1969 | allocator_->Adapter(kArenaAllocRegisterAllocator)); |
| 1970 | |
Vladimir Marko | 7d157fc | 2017-05-10 16:29:23 +0100 | [diff] [blame] | 1971 | for (LiveInterval* parent_interval : *intervals) { |
Matthew Gharrity | b6722ff | 2016-08-12 19:07:11 -0700 | [diff] [blame] | 1972 | DCHECK(parent_interval->IsParent()); |
| 1973 | DCHECK(!parent_interval->HasSpillSlot()); |
| 1974 | size_t start = parent_interval->GetStart(); |
| 1975 | size_t end = parent_interval->GetLastSibling()->GetEnd(); |
| 1976 | DCHECK_LT(start, end); |
| 1977 | interval_endpoints.push_back(std::make_tuple(start, true, parent_interval)); |
| 1978 | interval_endpoints.push_back(std::make_tuple(end, false, parent_interval)); |
| 1979 | } |
| 1980 | |
| 1981 | // Sort by position. |
| 1982 | // We explicitly ignore the third entry of each tuple (the interval pointer) in order |
| 1983 | // to maintain determinism. |
| 1984 | std::sort(interval_endpoints.begin(), interval_endpoints.end(), |
| 1985 | [] (const std::tuple<size_t, bool, LiveInterval*>& lhs, |
| 1986 | const std::tuple<size_t, bool, LiveInterval*>& rhs) { |
| 1987 | return std::tie(std::get<0>(lhs), std::get<1>(lhs)) |
| 1988 | < std::tie(std::get<0>(rhs), std::get<1>(rhs)); |
| 1989 | }); |
| 1990 | |
| 1991 | ArenaBitVector taken(allocator_, 0, true); |
| 1992 | for (auto it = interval_endpoints.begin(), end = interval_endpoints.end(); it != end; ++it) { |
| 1993 | // Extract information from the current tuple. |
| 1994 | LiveInterval* parent_interval; |
| 1995 | bool is_interval_beginning; |
| 1996 | size_t position; |
| 1997 | std::tie(position, is_interval_beginning, parent_interval) = *it; |
Aart Bik | cc89525 | 2017-03-21 10:55:15 -0700 | [diff] [blame] | 1998 | size_t number_of_spill_slots_needed = parent_interval->NumberOfSpillSlotsNeeded(); |
Matthew Gharrity | b6722ff | 2016-08-12 19:07:11 -0700 | [diff] [blame] | 1999 | |
| 2000 | if (is_interval_beginning) { |
| 2001 | DCHECK(!parent_interval->HasSpillSlot()); |
| 2002 | DCHECK_EQ(position, parent_interval->GetStart()); |
| 2003 | |
Aart Bik | cc89525 | 2017-03-21 10:55:15 -0700 | [diff] [blame] | 2004 | // Find first available free stack slot(s). |
Matthew Gharrity | b6722ff | 2016-08-12 19:07:11 -0700 | [diff] [blame] | 2005 | size_t slot = 0; |
Aart Bik | cc89525 | 2017-03-21 10:55:15 -0700 | [diff] [blame] | 2006 | for (; ; ++slot) { |
| 2007 | bool found = true; |
| 2008 | for (size_t s = slot, u = slot + number_of_spill_slots_needed; s < u; s++) { |
| 2009 | if (taken.IsBitSet(s)) { |
| 2010 | found = false; |
| 2011 | break; // failure |
| 2012 | } |
| 2013 | } |
| 2014 | if (found) { |
| 2015 | break; // success |
| 2016 | } |
Matthew Gharrity | b6722ff | 2016-08-12 19:07:11 -0700 | [diff] [blame] | 2017 | } |
Aart Bik | cc89525 | 2017-03-21 10:55:15 -0700 | [diff] [blame] | 2018 | |
Matthew Gharrity | b6722ff | 2016-08-12 19:07:11 -0700 | [diff] [blame] | 2019 | parent_interval->SetSpillSlot(slot); |
| 2020 | |
Aart Bik | cc89525 | 2017-03-21 10:55:15 -0700 | [diff] [blame] | 2021 | *num_stack_slots_used = std::max(*num_stack_slots_used, slot + number_of_spill_slots_needed); |
| 2022 | if (number_of_spill_slots_needed > 1 && *num_stack_slots_used % 2 != 0) { |
Matthew Gharrity | b6722ff | 2016-08-12 19:07:11 -0700 | [diff] [blame] | 2023 | // The parallel move resolver requires that there be an even number of spill slots |
| 2024 | // allocated for pair value types. |
| 2025 | ++(*num_stack_slots_used); |
| 2026 | } |
| 2027 | |
Aart Bik | cc89525 | 2017-03-21 10:55:15 -0700 | [diff] [blame] | 2028 | for (size_t s = slot, u = slot + number_of_spill_slots_needed; s < u; s++) { |
| 2029 | taken.SetBit(s); |
Matthew Gharrity | b6722ff | 2016-08-12 19:07:11 -0700 | [diff] [blame] | 2030 | } |
| 2031 | } else { |
| 2032 | DCHECK_EQ(position, parent_interval->GetLastSibling()->GetEnd()); |
| 2033 | DCHECK(parent_interval->HasSpillSlot()); |
| 2034 | |
Aart Bik | cc89525 | 2017-03-21 10:55:15 -0700 | [diff] [blame] | 2035 | // Free up the stack slot(s) used by this interval. |
Matthew Gharrity | b6722ff | 2016-08-12 19:07:11 -0700 | [diff] [blame] | 2036 | size_t slot = parent_interval->GetSpillSlot(); |
Aart Bik | cc89525 | 2017-03-21 10:55:15 -0700 | [diff] [blame] | 2037 | for (size_t s = slot, u = slot + number_of_spill_slots_needed; s < u; s++) { |
| 2038 | DCHECK(taken.IsBitSet(s)); |
| 2039 | taken.ClearBit(s); |
Matthew Gharrity | b6722ff | 2016-08-12 19:07:11 -0700 | [diff] [blame] | 2040 | } |
| 2041 | } |
| 2042 | } |
| 2043 | DCHECK_EQ(taken.NumSetBits(), 0u); |
Matthew Gharrity | d9ffd0d | 2016-06-22 10:27:55 -0700 | [diff] [blame] | 2044 | } |
| 2045 | |
| 2046 | } // namespace art |