SplitKit.h revision 8dd070edc2209ecfdae49780ec1596b349e2cbd1
1//===-------- SplitKit.h - Toolkit for splitting live ranges ----*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file contains the SplitAnalysis class as well as mutator functions for 11// live range splitting. 12// 13//===----------------------------------------------------------------------===// 14 15#include "llvm/ADT/DenseMap.h" 16#include "llvm/ADT/SmallPtrSet.h" 17#include "llvm/CodeGen/SlotIndexes.h" 18 19namespace llvm { 20 21class LiveInterval; 22class LiveIntervals; 23class LiveRangeEdit; 24class MachineInstr; 25class MachineLoop; 26class MachineLoopInfo; 27class MachineRegisterInfo; 28class TargetInstrInfo; 29class TargetRegisterInfo; 30class VirtRegMap; 31class VNInfo; 32class raw_ostream; 33 34/// At some point we should just include MachineDominators.h: 35class MachineDominatorTree; 36template <class NodeT> class DomTreeNodeBase; 37typedef DomTreeNodeBase<MachineBasicBlock> MachineDomTreeNode; 38 39 40/// SplitAnalysis - Analyze a LiveInterval, looking for live range splitting 41/// opportunities. 42class SplitAnalysis { 43public: 44 const MachineFunction &mf_; 45 const LiveIntervals &lis_; 46 const MachineLoopInfo &loops_; 47 const TargetInstrInfo &tii_; 48 49 // Instructions using the the current register. 50 typedef SmallPtrSet<const MachineInstr*, 16> InstrPtrSet; 51 InstrPtrSet usingInstrs_; 52 53 // The number of instructions using curli in each basic block. 54 typedef DenseMap<const MachineBasicBlock*, unsigned> BlockCountMap; 55 BlockCountMap usingBlocks_; 56 57 // The number of basic block using curli in each loop. 58 typedef DenseMap<const MachineLoop*, unsigned> LoopCountMap; 59 LoopCountMap usingLoops_; 60 61private: 62 // Current live interval. 63 const LiveInterval *curli_; 64 65 // Sumarize statistics by counting instructions using curli_. 66 void analyzeUses(); 67 68 /// canAnalyzeBranch - Return true if MBB ends in a branch that can be 69 /// analyzed. 70 bool canAnalyzeBranch(const MachineBasicBlock *MBB); 71 72public: 73 SplitAnalysis(const MachineFunction &mf, const LiveIntervals &lis, 74 const MachineLoopInfo &mli); 75 76 /// analyze - set curli to the specified interval, and analyze how it may be 77 /// split. 78 void analyze(const LiveInterval *li); 79 80 /// clear - clear all data structures so SplitAnalysis is ready to analyze a 81 /// new interval. 82 void clear(); 83 84 typedef SmallPtrSet<const MachineBasicBlock*, 16> BlockPtrSet; 85 typedef SmallPtrSet<const MachineLoop*, 16> LoopPtrSet; 86 87 // Print a set of blocks with use counts. 88 void print(const BlockPtrSet&, raw_ostream&) const; 89 90 // Sets of basic blocks surrounding a machine loop. 91 struct LoopBlocks { 92 BlockPtrSet Loop; // Blocks in the loop. 93 BlockPtrSet Preds; // Loop predecessor blocks. 94 BlockPtrSet Exits; // Loop exit blocks. 95 96 void clear() { 97 Loop.clear(); 98 Preds.clear(); 99 Exits.clear(); 100 } 101 }; 102 103 // Print loop blocks with use counts. 104 void print(const LoopBlocks&, raw_ostream&) const; 105 106 // Calculate the block sets surrounding the loop. 107 void getLoopBlocks(const MachineLoop *Loop, LoopBlocks &Blocks); 108 109 /// LoopPeripheralUse - how is a variable used in and around a loop? 110 /// Peripheral blocks are the loop predecessors and exit blocks. 111 enum LoopPeripheralUse { 112 ContainedInLoop, // All uses are inside the loop. 113 SinglePeripheral, // At most one instruction per peripheral block. 114 MultiPeripheral, // Multiple instructions in some peripheral blocks. 115 OutsideLoop // Uses outside loop periphery. 116 }; 117 118 /// analyzeLoopPeripheralUse - Return an enum describing how curli_ is used in 119 /// and around the Loop. 120 LoopPeripheralUse analyzeLoopPeripheralUse(const LoopBlocks&); 121 122 /// getCriticalExits - It may be necessary to partially break critical edges 123 /// leaving the loop if an exit block has phi uses of curli. Collect the exit 124 /// blocks that need special treatment into CriticalExits. 125 void getCriticalExits(const LoopBlocks &Blocks, BlockPtrSet &CriticalExits); 126 127 /// canSplitCriticalExits - Return true if it is possible to insert new exit 128 /// blocks before the blocks in CriticalExits. 129 bool canSplitCriticalExits(const LoopBlocks &Blocks, 130 BlockPtrSet &CriticalExits); 131 132 /// getCriticalPreds - Get the set of loop predecessors with critical edges to 133 /// blocks outside the loop that have curli live in. We don't have to break 134 /// these edges, but they do require special treatment. 135 void getCriticalPreds(const LoopBlocks &Blocks, BlockPtrSet &CriticalPreds); 136 137 /// getSplitLoops - Get the set of loops that have curli uses and would be 138 /// profitable to split. 139 void getSplitLoops(LoopPtrSet&); 140 141 /// getBestSplitLoop - Return the loop where curli may best be split to a 142 /// separate register, or NULL. 143 const MachineLoop *getBestSplitLoop(); 144 145 /// isBypassLoop - Return true if curli is live through Loop and has no uses 146 /// inside the loop. Bypass loops are candidates for splitting because it can 147 /// prevent interference inside the loop. 148 bool isBypassLoop(const MachineLoop *Loop); 149 150 /// getBypassLoops - Get all the maximal bypass loops. These are the bypass 151 /// loops whose parent is not a bypass loop. 152 void getBypassLoops(LoopPtrSet&); 153 154 /// getMultiUseBlocks - Add basic blocks to Blocks that may benefit from 155 /// having curli split to a new live interval. Return true if Blocks can be 156 /// passed to SplitEditor::splitSingleBlocks. 157 bool getMultiUseBlocks(BlockPtrSet &Blocks); 158 159 /// getBlockForInsideSplit - If curli is contained inside a single basic block, 160 /// and it wou pay to subdivide the interval inside that block, return it. 161 /// Otherwise return NULL. The returned block can be passed to 162 /// SplitEditor::splitInsideBlock. 163 const MachineBasicBlock *getBlockForInsideSplit(); 164}; 165 166 167/// LiveIntervalMap - Map values from a large LiveInterval into a small 168/// interval that is a subset. Insert phi-def values as needed. This class is 169/// used by SplitEditor to create new smaller LiveIntervals. 170/// 171/// parentli_ is the larger interval, li_ is the subset interval. Every value 172/// in li_ corresponds to exactly one value in parentli_, and the live range 173/// of the value is contained within the live range of the parentli_ value. 174/// Values in parentli_ may map to any number of openli_ values, including 0. 175class LiveIntervalMap { 176 LiveIntervals &lis_; 177 MachineDominatorTree &mdt_; 178 179 // The parent interval is never changed. 180 const LiveInterval &parentli_; 181 182 // The child interval's values are fully contained inside parentli_ values. 183 LiveInterval *li_; 184 185 typedef DenseMap<const VNInfo*, VNInfo*> ValueMap; 186 187 // Map parentli_ values to simple values in li_ that are defined at the same 188 // SlotIndex, or NULL for parentli_ values that have complex li_ defs. 189 // Note there is a difference between values mapping to NULL (complex), and 190 // values not present (unknown/unmapped). 191 ValueMap valueMap_; 192 193 typedef std::pair<VNInfo*, MachineDomTreeNode*> LiveOutPair; 194 typedef DenseMap<MachineBasicBlock*,LiveOutPair> LiveOutMap; 195 196 // liveOutCache_ - Map each basic block where li_ is live out to the live-out 197 // value and its defining block. One of these conditions shall be true: 198 // 199 // 1. !liveOutCache_.count(MBB) 200 // 2. liveOutCache_[MBB].second.getNode() == MBB 201 // 3. forall P in preds(MBB): liveOutCache_[P] == liveOutCache_[MBB] 202 // 203 // This is only a cache, the values can be computed as: 204 // 205 // VNI = li_->getVNInfoAt(lis_.getMBBEndIdx(MBB)) 206 // Node = mbt_[lis_.getMBBFromIndex(VNI->def)] 207 // 208 // The cache is also used as a visiteed set by mapValue(). 209 LiveOutMap liveOutCache_; 210 211public: 212 LiveIntervalMap(LiveIntervals &lis, 213 MachineDominatorTree &mdt, 214 const LiveInterval &parentli) 215 : lis_(lis), mdt_(mdt), parentli_(parentli), li_(0) {} 216 217 /// reset - clear all data structures and start a new live interval. 218 void reset(LiveInterval *); 219 220 /// getLI - return the current live interval. 221 LiveInterval *getLI() const { return li_; } 222 223 /// defValue - define a value in li_ from the parentli_ value VNI and Idx. 224 /// Idx does not have to be ParentVNI->def, but it must be contained within 225 /// ParentVNI's live range in parentli_. 226 /// Return the new li_ value. 227 VNInfo *defValue(const VNInfo *ParentVNI, SlotIndex Idx); 228 229 /// mapValue - map ParentVNI to the corresponding li_ value at Idx. It is 230 /// assumed that ParentVNI is live at Idx. 231 /// If ParentVNI has not been defined by defValue, it is assumed that 232 /// ParentVNI->def dominates Idx. 233 /// If ParentVNI has been defined by defValue one or more times, a value that 234 /// dominates Idx will be returned. This may require creating extra phi-def 235 /// values and adding live ranges to li_. 236 /// If simple is not NULL, *simple will indicate if ParentVNI is a simply 237 /// mapped value. 238 VNInfo *mapValue(const VNInfo *ParentVNI, SlotIndex Idx, bool *simple = 0); 239 240 // extendTo - Find the last li_ value defined in MBB at or before Idx. The 241 // parentli is assumed to be live at Idx. Extend the live range to include 242 // Idx. Return the found VNInfo, or NULL. 243 VNInfo *extendTo(const MachineBasicBlock *MBB, SlotIndex Idx); 244 245 /// isMapped - Return true is ParentVNI is a known mapped value. It may be a 246 /// simple 1-1 mapping or a complex mapping to later defs. 247 bool isMapped(const VNInfo *ParentVNI) const { 248 return valueMap_.count(ParentVNI); 249 } 250 251 /// isComplexMapped - Return true if ParentVNI has received new definitions 252 /// with defValue. 253 bool isComplexMapped(const VNInfo *ParentVNI) const; 254 255 // addSimpleRange - Add a simple range from parentli_ to li_. 256 // ParentVNI must be live in the [Start;End) interval. 257 void addSimpleRange(SlotIndex Start, SlotIndex End, const VNInfo *ParentVNI); 258 259 /// addRange - Add live ranges to li_ where [Start;End) intersects parentli_. 260 /// All needed values whose def is not inside [Start;End) must be defined 261 /// beforehand so mapValue will work. 262 void addRange(SlotIndex Start, SlotIndex End); 263}; 264 265 266/// SplitEditor - Edit machine code and LiveIntervals for live range 267/// splitting. 268/// 269/// - Create a SplitEditor from a SplitAnalysis. 270/// - Start a new live interval with openIntv. 271/// - Mark the places where the new interval is entered using enterIntv* 272/// - Mark the ranges where the new interval is used with useIntv* 273/// - Mark the places where the interval is exited with exitIntv*. 274/// - Finish the current interval with closeIntv and repeat from 2. 275/// - Rewrite instructions with finish(). 276/// 277class SplitEditor { 278 SplitAnalysis &sa_; 279 LiveIntervals &lis_; 280 VirtRegMap &vrm_; 281 MachineRegisterInfo &mri_; 282 const TargetInstrInfo &tii_; 283 const TargetRegisterInfo &tri_; 284 285 /// edit_ - The current parent register and new intervals created. 286 LiveRangeEdit &edit_; 287 288 /// dupli_ - Created as a copy of curli_, ranges are carved out as new 289 /// intervals get added through openIntv / closeIntv. This is used to avoid 290 /// editing curli_. 291 LiveIntervalMap dupli_; 292 293 /// Currently open LiveInterval. 294 LiveIntervalMap openli_; 295 296 /// defFromParent - Define Reg from ParentVNI at UseIdx using either 297 /// rematerialization or a COPY from parent. Return the new value. 298 VNInfo *defFromParent(LiveIntervalMap &Reg, 299 VNInfo *ParentVNI, 300 SlotIndex UseIdx, 301 MachineBasicBlock &MBB, 302 MachineBasicBlock::iterator I); 303 304 /// intervalsLiveAt - Return true if any member of intervals_ is live at Idx. 305 bool intervalsLiveAt(SlotIndex Idx) const; 306 307 /// Values in curli whose live range has been truncated when entering an open 308 /// li. 309 SmallPtrSet<const VNInfo*, 8> truncatedValues; 310 311 /// addTruncSimpleRange - Add the given simple range to dupli_ after 312 /// truncating any overlap with intervals_. 313 void addTruncSimpleRange(SlotIndex Start, SlotIndex End, VNInfo *VNI); 314 315 /// criticalPreds_ - Set of basic blocks where both dupli and openli should be 316 /// live out because of a critical edge. 317 SplitAnalysis::BlockPtrSet criticalPreds_; 318 319 /// computeRemainder - Compute the dupli liveness as the complement of all the 320 /// new intervals. 321 void computeRemainder(); 322 323 /// rewrite - Rewrite all uses of reg to use the new registers. 324 void rewrite(unsigned reg); 325 326public: 327 /// Create a new SplitEditor for editing the LiveInterval analyzed by SA. 328 /// Newly created intervals will be appended to newIntervals. 329 SplitEditor(SplitAnalysis &SA, LiveIntervals&, VirtRegMap&, 330 MachineDominatorTree&, LiveRangeEdit&); 331 332 /// getAnalysis - Get the corresponding analysis. 333 SplitAnalysis &getAnalysis() { return sa_; } 334 335 /// Create a new virtual register and live interval. 336 void openIntv(); 337 338 /// enterIntvBefore - Enter openli before the instruction at Idx. If curli is 339 /// not live before Idx, a COPY is not inserted. 340 void enterIntvBefore(SlotIndex Idx); 341 342 /// enterIntvAtEnd - Enter openli at the end of MBB. 343 void enterIntvAtEnd(MachineBasicBlock &MBB); 344 345 /// useIntv - indicate that all instructions in MBB should use openli. 346 void useIntv(const MachineBasicBlock &MBB); 347 348 /// useIntv - indicate that all instructions in range should use openli. 349 void useIntv(SlotIndex Start, SlotIndex End); 350 351 /// leaveIntvAfter - Leave openli after the instruction at Idx. 352 void leaveIntvAfter(SlotIndex Idx); 353 354 /// leaveIntvAtTop - Leave the interval at the top of MBB. 355 /// Currently, only one value can leave the interval. 356 void leaveIntvAtTop(MachineBasicBlock &MBB); 357 358 /// closeIntv - Indicate that we are done editing the currently open 359 /// LiveInterval, and ranges can be trimmed. 360 void closeIntv(); 361 362 /// finish - after all the new live ranges have been created, compute the 363 /// remaining live range, and rewrite instructions to use the new registers. 364 void finish(); 365 366 // ===--- High level methods ---=== 367 368 /// splitAroundLoop - Split curli into a separate live interval inside 369 /// the loop. 370 void splitAroundLoop(const MachineLoop*); 371 372 /// splitSingleBlocks - Split curli into a separate live interval inside each 373 /// basic block in Blocks. 374 void splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks); 375 376 /// splitInsideBlock - Split curli into multiple intervals inside MBB. 377 void splitInsideBlock(const MachineBasicBlock *); 378}; 379 380} 381