SplitKit.h revision 708d06f7fb5dfd9c8559aea07b042a88c65645f8
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#ifndef LLVM_CODEGEN_SPLITKIT_H 16#define LLVM_CODEGEN_SPLITKIT_H 17 18#include "llvm/ADT/ArrayRef.h" 19#include "llvm/ADT/BitVector.h" 20#include "llvm/ADT/DenseMap.h" 21#include "llvm/ADT/IndexedMap.h" 22#include "llvm/ADT/IntervalMap.h" 23#include "llvm/ADT/SmallPtrSet.h" 24#include "llvm/CodeGen/SlotIndexes.h" 25 26namespace llvm { 27 28class ConnectedVNInfoEqClasses; 29class LiveInterval; 30class LiveIntervals; 31class LiveRangeEdit; 32class MachineInstr; 33class MachineLoopInfo; 34class MachineRegisterInfo; 35class TargetInstrInfo; 36class TargetRegisterInfo; 37class VirtRegMap; 38class VNInfo; 39class raw_ostream; 40 41/// At some point we should just include MachineDominators.h: 42class MachineDominatorTree; 43template <class NodeT> class DomTreeNodeBase; 44typedef DomTreeNodeBase<MachineBasicBlock> MachineDomTreeNode; 45 46 47/// SplitAnalysis - Analyze a LiveInterval, looking for live range splitting 48/// opportunities. 49class SplitAnalysis { 50public: 51 const MachineFunction &MF; 52 const VirtRegMap &VRM; 53 const LiveIntervals &LIS; 54 const MachineLoopInfo &Loops; 55 const TargetInstrInfo &TII; 56 57 // Sorted slot indexes of using instructions. 58 SmallVector<SlotIndex, 8> UseSlots; 59 60 /// Additional information about basic blocks where the current variable is 61 /// live. Such a block will look like one of these templates: 62 /// 63 /// 1. | o---x | Internal to block. Variable is only live in this block. 64 /// 2. |---x | Live-in, kill. 65 /// 3. | o---| Def, live-out. 66 /// 4. |---x o---| Live-in, kill, def, live-out. Counted by NumGapBlocks. 67 /// 5. |---o---o---| Live-through with uses or defs. 68 /// 6. |-----------| Live-through without uses. Counted by NumThroughBlocks. 69 /// 70 /// Two BlockInfo entries are created for template 4. One for the live-in 71 /// segment, and one for the live-out segment. These entries look as if the 72 /// block were split in the middle where the live range isn't live. 73 /// 74 /// Live-through blocks without any uses don't get BlockInfo entries. They 75 /// are simply listed in ThroughBlocks instead. 76 /// 77 struct BlockInfo { 78 MachineBasicBlock *MBB; 79 SlotIndex FirstInstr; ///< First instr accessing current reg. 80 SlotIndex LastInstr; ///< Last instr accessing current reg. 81 SlotIndex FirstDef; ///< First non-phi valno->def, or SlotIndex(). 82 bool LiveIn; ///< Current reg is live in. 83 bool LiveOut; ///< Current reg is live out. 84 85 /// isOneInstr - Returns true when this BlockInfo describes a single 86 /// instruction. 87 bool isOneInstr() const { 88 return SlotIndex::isSameInstr(FirstInstr, LastInstr); 89 } 90 }; 91 92private: 93 // Current live interval. 94 const LiveInterval *CurLI; 95 96 /// LastSplitPoint - Last legal split point in each basic block in the current 97 /// function. The first entry is the first terminator, the second entry is the 98 /// last valid split point for a variable that is live in to a landing pad 99 /// successor. 100 SmallVector<std::pair<SlotIndex, SlotIndex>, 8> LastSplitPoint; 101 102 /// UseBlocks - Blocks where CurLI has uses. 103 SmallVector<BlockInfo, 8> UseBlocks; 104 105 /// NumGapBlocks - Number of duplicate entries in UseBlocks for blocks where 106 /// the live range has a gap. 107 unsigned NumGapBlocks; 108 109 /// ThroughBlocks - Block numbers where CurLI is live through without uses. 110 BitVector ThroughBlocks; 111 112 /// NumThroughBlocks - Number of live-through blocks. 113 unsigned NumThroughBlocks; 114 115 /// DidRepairRange - analyze was forced to shrinkToUses(). 116 bool DidRepairRange; 117 118 SlotIndex computeLastSplitPoint(unsigned Num); 119 120 // Sumarize statistics by counting instructions using CurLI. 121 void analyzeUses(); 122 123 /// calcLiveBlockInfo - Compute per-block information about CurLI. 124 bool calcLiveBlockInfo(); 125 126public: 127 SplitAnalysis(const VirtRegMap &vrm, const LiveIntervals &lis, 128 const MachineLoopInfo &mli); 129 130 /// analyze - set CurLI to the specified interval, and analyze how it may be 131 /// split. 132 void analyze(const LiveInterval *li); 133 134 /// didRepairRange() - Returns true if CurLI was invalid and has been repaired 135 /// by analyze(). This really shouldn't happen, but sometimes the coalescer 136 /// can create live ranges that end in mid-air. 137 bool didRepairRange() const { return DidRepairRange; } 138 139 /// clear - clear all data structures so SplitAnalysis is ready to analyze a 140 /// new interval. 141 void clear(); 142 143 /// getParent - Return the last analyzed interval. 144 const LiveInterval &getParent() const { return *CurLI; } 145 146 /// getLastSplitPoint - Return that base index of the last valid split point 147 /// in the basic block numbered Num. 148 SlotIndex getLastSplitPoint(unsigned Num) { 149 // Inline the common simple case. 150 if (LastSplitPoint[Num].first.isValid() && 151 !LastSplitPoint[Num].second.isValid()) 152 return LastSplitPoint[Num].first; 153 return computeLastSplitPoint(Num); 154 } 155 156 /// isOriginalEndpoint - Return true if the original live range was killed or 157 /// (re-)defined at Idx. Idx should be the 'def' slot for a normal kill/def, 158 /// and 'use' for an early-clobber def. 159 /// This can be used to recognize code inserted by earlier live range 160 /// splitting. 161 bool isOriginalEndpoint(SlotIndex Idx) const; 162 163 /// getUseBlocks - Return an array of BlockInfo objects for the basic blocks 164 /// where CurLI has uses. 165 ArrayRef<BlockInfo> getUseBlocks() const { return UseBlocks; } 166 167 /// getNumThroughBlocks - Return the number of through blocks. 168 unsigned getNumThroughBlocks() const { return NumThroughBlocks; } 169 170 /// isThroughBlock - Return true if CurLI is live through MBB without uses. 171 bool isThroughBlock(unsigned MBB) const { return ThroughBlocks.test(MBB); } 172 173 /// getThroughBlocks - Return the set of through blocks. 174 const BitVector &getThroughBlocks() const { return ThroughBlocks; } 175 176 /// getNumLiveBlocks - Return the number of blocks where CurLI is live. 177 unsigned getNumLiveBlocks() const { 178 return getUseBlocks().size() - NumGapBlocks + getNumThroughBlocks(); 179 } 180 181 /// countLiveBlocks - Return the number of blocks where li is live. This is 182 /// guaranteed to return the same number as getNumLiveBlocks() after calling 183 /// analyze(li). 184 unsigned countLiveBlocks(const LiveInterval *li) const; 185 186 typedef SmallPtrSet<const MachineBasicBlock*, 16> BlockPtrSet; 187 188 /// shouldSplitSingleBlock - Returns true if it would help to create a local 189 /// live range for the instructions in BI. There is normally no benefit to 190 /// creating a live range for a single instruction, but it does enable 191 /// register class inflation if the instruction has a restricted register 192 /// class. 193 /// 194 /// @param BI The block to be isolated. 195 /// @param SingleInstrs True when single instructions should be isolated. 196 bool shouldSplitSingleBlock(const BlockInfo &BI, bool SingleInstrs) const; 197}; 198 199 200/// SplitEditor - Edit machine code and LiveIntervals for live range 201/// splitting. 202/// 203/// - Create a SplitEditor from a SplitAnalysis. 204/// - Start a new live interval with openIntv. 205/// - Mark the places where the new interval is entered using enterIntv* 206/// - Mark the ranges where the new interval is used with useIntv* 207/// - Mark the places where the interval is exited with exitIntv*. 208/// - Finish the current interval with closeIntv and repeat from 2. 209/// - Rewrite instructions with finish(). 210/// 211class SplitEditor { 212 SplitAnalysis &SA; 213 LiveIntervals &LIS; 214 VirtRegMap &VRM; 215 MachineRegisterInfo &MRI; 216 MachineDominatorTree &MDT; 217 const TargetInstrInfo &TII; 218 const TargetRegisterInfo &TRI; 219 220public: 221 222 /// ComplementSpillMode - Select how the complement live range should be 223 /// created. SplitEditor automatically creates interval 0 to contain 224 /// anything that isn't added to another interval. This complement interval 225 /// can get quite complicated, and it can sometimes be an advantage to allow 226 /// it to overlap the other intervals. If it is going to spill anyway, no 227 /// registers are wasted by keeping a value in two places at the same time. 228 enum ComplementSpillMode { 229 /// SM_Partition(Default) - Try to create the complement interval so it 230 /// doesn't overlap any other intervals, and the original interval is 231 /// partitioned. This may require a large number of back copies and extra 232 /// PHI-defs. Only segments marked with overlapIntv will be overlapping. 233 SM_Partition, 234 235 /// SM_Size - Overlap intervals to minimize the number of inserted COPY 236 /// instructions. Copies to the complement interval are hoisted to their 237 /// common dominator, so only one COPY is required per value in the 238 /// complement interval. This also means that no extra PHI-defs need to be 239 /// inserted in the complement interval. 240 SM_Size, 241 242 /// SM_Speed - Overlap intervals to minimize the expected execution 243 /// frequency of the inserted copies. This is very similar to SM_Size, but 244 /// the complement interval may get some extra PHI-defs. 245 SM_Speed 246 }; 247 248private: 249 250 /// Edit - The current parent register and new intervals created. 251 LiveRangeEdit *Edit; 252 253 /// Index into Edit of the currently open interval. 254 /// The index 0 is used for the complement, so the first interval started by 255 /// openIntv will be 1. 256 unsigned OpenIdx; 257 258 /// The current spill mode, selected by reset(). 259 ComplementSpillMode SpillMode; 260 261 typedef IntervalMap<SlotIndex, unsigned> RegAssignMap; 262 263 /// Allocator for the interval map. This will eventually be shared with 264 /// SlotIndexes and LiveIntervals. 265 RegAssignMap::Allocator Allocator; 266 267 /// RegAssign - Map of the assigned register indexes. 268 /// Edit.get(RegAssign.lookup(Idx)) is the register that should be live at 269 /// Idx. 270 RegAssignMap RegAssign; 271 272 typedef DenseMap<std::pair<unsigned, unsigned>, VNInfo*> ValueMap; 273 274 /// Values - keep track of the mapping from parent values to values in the new 275 /// intervals. Given a pair (RegIdx, ParentVNI->id), Values contains: 276 /// 277 /// 1. No entry - the value is not mapped to Edit.get(RegIdx). 278 /// 2. Null - the value is mapped to multiple values in Edit.get(RegIdx). 279 /// Each value is represented by a minimal live range at its def. 280 /// 3. A non-null VNInfo - the value is mapped to a single new value. 281 /// The new value has no live ranges anywhere. 282 ValueMap Values; 283 284 typedef std::pair<VNInfo*, MachineDomTreeNode*> LiveOutPair; 285 typedef IndexedMap<LiveOutPair, MBB2NumberFunctor> LiveOutMap; 286 287 // LiveOutCache - Map each basic block where a new register is live out to the 288 // live-out value and its defining block. 289 // One of these conditions shall be true: 290 // 291 // 1. !LiveOutSeen.count(MBB->getNumber()) 292 // 2. LiveOutCache[MBB].second.getNode() == MBB 293 // 3. forall P in preds(MBB): LiveOutCache[P] == LiveOutCache[MBB] 294 // 295 // This is only a cache, the values can be computed as: 296 // 297 // VNI = Edit.get(RegIdx)->getVNInfoAt(LIS.getMBBEndIdx(MBB)) 298 // Node = mbt_[LIS.getMBBFromIndex(VNI->def)] 299 // 300 // The cache can be shared by all the new registers because at most one is 301 // live out of each block. 302 LiveOutMap LiveOutCache; 303 304 // LiveOutSeen - Indexed by MBB->getNumber(), a bit is set for each valid 305 // entry in LiveOutCache. This is also used as a visited set for 306 // findReachingDefs(). 307 BitVector LiveOutSeen; 308 309 /// LiveInBlock - Info for updateSSA() about a block where a register is 310 /// live-in. 311 /// The updateSSA caller provides DomNode and Kill inside MBB, updateSSA() 312 /// adds the computed live-in value. 313 struct LiveInBlock { 314 // Dominator tree node for the block. 315 // Cleared by updateSSA when the final value has been determined. 316 MachineDomTreeNode *DomNode; 317 318 // Live-in value filled in by updateSSA once it is known. 319 VNInfo *Value; 320 321 // Position in block where the live-in range ends, or SlotIndex() if the 322 // range passes through the block. 323 SlotIndex Kill; 324 325 LiveInBlock(MachineDomTreeNode *node) : DomNode(node), Value(0) {} 326 }; 327 328 /// LiveInBlocks - List of live-in blocks used by findReachingDefs() and 329 /// updateSSA(). This list is usually empty, it exists here to avoid frequent 330 /// reallocations. 331 SmallVector<LiveInBlock, 16> LiveInBlocks; 332 333 /// defValue - define a value in RegIdx from ParentVNI at Idx. 334 /// Idx does not have to be ParentVNI->def, but it must be contained within 335 /// ParentVNI's live range in ParentLI. The new value is added to the value 336 /// map. 337 /// Return the new LI value. 338 VNInfo *defValue(unsigned RegIdx, const VNInfo *ParentVNI, SlotIndex Idx); 339 340 /// markComplexMapped - Mark ParentVNI as complex mapped in RegIdx regardless 341 /// of the number of defs. 342 void markComplexMapped(unsigned RegIdx, const VNInfo *ParentVNI); 343 344 /// defFromParent - Define Reg from ParentVNI at UseIdx using either 345 /// rematerialization or a COPY from parent. Return the new value. 346 VNInfo *defFromParent(unsigned RegIdx, 347 VNInfo *ParentVNI, 348 SlotIndex UseIdx, 349 MachineBasicBlock &MBB, 350 MachineBasicBlock::iterator I); 351 352 /// extendRange - Extend the live range of Edit.get(RegIdx) so it reaches Idx. 353 /// Insert PHIDefs as needed to preserve SSA form. 354 void extendRange(unsigned RegIdx, SlotIndex Idx); 355 356 /// findReachingDefs - Starting from MBB, add blocks to LiveInBlocks until all 357 /// reaching defs for LI are found. 358 /// @param LI Live interval whose value is needed. 359 /// @param MBB Block where LI should be live-in. 360 /// @param Kill Kill point in MBB. 361 /// @return Unique value seen, or NULL. 362 VNInfo *findReachingDefs(LiveInterval *LI, MachineBasicBlock *MBB, 363 SlotIndex Kill); 364 365 /// updateSSA - Compute and insert PHIDefs such that all blocks in 366 // LiveInBlocks get a known live-in value. Add live ranges to the blocks. 367 void updateSSA(); 368 369 /// transferValues - Transfer values to the new ranges. 370 /// Return true if any ranges were skipped. 371 bool transferValues(); 372 373 /// extendPHIKillRanges - Extend the ranges of all values killed by original 374 /// parent PHIDefs. 375 void extendPHIKillRanges(); 376 377 /// rewriteAssigned - Rewrite all uses of Edit.getReg() to assigned registers. 378 void rewriteAssigned(bool ExtendRanges); 379 380 /// deleteRematVictims - Delete defs that are dead after rematerializing. 381 void deleteRematVictims(); 382 383public: 384 /// Create a new SplitEditor for editing the LiveInterval analyzed by SA. 385 /// Newly created intervals will be appended to newIntervals. 386 SplitEditor(SplitAnalysis &SA, LiveIntervals&, VirtRegMap&, 387 MachineDominatorTree&); 388 389 /// reset - Prepare for a new split. 390 void reset(LiveRangeEdit&, ComplementSpillMode = SM_Partition); 391 392 /// Create a new virtual register and live interval. 393 /// Return the interval index, starting from 1. Interval index 0 is the 394 /// implicit complement interval. 395 unsigned openIntv(); 396 397 /// currentIntv - Return the current interval index. 398 unsigned currentIntv() const { return OpenIdx; } 399 400 /// selectIntv - Select a previously opened interval index. 401 void selectIntv(unsigned Idx); 402 403 /// enterIntvBefore - Enter the open interval before the instruction at Idx. 404 /// If the parent interval is not live before Idx, a COPY is not inserted. 405 /// Return the beginning of the new live range. 406 SlotIndex enterIntvBefore(SlotIndex Idx); 407 408 /// enterIntvAfter - Enter the open interval after the instruction at Idx. 409 /// Return the beginning of the new live range. 410 SlotIndex enterIntvAfter(SlotIndex Idx); 411 412 /// enterIntvAtEnd - Enter the open interval at the end of MBB. 413 /// Use the open interval from he inserted copy to the MBB end. 414 /// Return the beginning of the new live range. 415 SlotIndex enterIntvAtEnd(MachineBasicBlock &MBB); 416 417 /// useIntv - indicate that all instructions in MBB should use OpenLI. 418 void useIntv(const MachineBasicBlock &MBB); 419 420 /// useIntv - indicate that all instructions in range should use OpenLI. 421 void useIntv(SlotIndex Start, SlotIndex End); 422 423 /// leaveIntvAfter - Leave the open interval after the instruction at Idx. 424 /// Return the end of the live range. 425 SlotIndex leaveIntvAfter(SlotIndex Idx); 426 427 /// leaveIntvBefore - Leave the open interval before the instruction at Idx. 428 /// Return the end of the live range. 429 SlotIndex leaveIntvBefore(SlotIndex Idx); 430 431 /// leaveIntvAtTop - Leave the interval at the top of MBB. 432 /// Add liveness from the MBB top to the copy. 433 /// Return the end of the live range. 434 SlotIndex leaveIntvAtTop(MachineBasicBlock &MBB); 435 436 /// overlapIntv - Indicate that all instructions in range should use the open 437 /// interval, but also let the complement interval be live. 438 /// 439 /// This doubles the register pressure, but is sometimes required to deal with 440 /// register uses after the last valid split point. 441 /// 442 /// The Start index should be a return value from a leaveIntv* call, and End 443 /// should be in the same basic block. The parent interval must have the same 444 /// value across the range. 445 /// 446 void overlapIntv(SlotIndex Start, SlotIndex End); 447 448 /// finish - after all the new live ranges have been created, compute the 449 /// remaining live range, and rewrite instructions to use the new registers. 450 /// @param LRMap When not null, this vector will map each live range in Edit 451 /// back to the indices returned by openIntv. 452 /// There may be extra indices created by dead code elimination. 453 void finish(SmallVectorImpl<unsigned> *LRMap = 0); 454 455 /// dump - print the current interval maping to dbgs(). 456 void dump() const; 457 458 // ===--- High level methods ---=== 459 460 /// splitSingleBlock - Split CurLI into a separate live interval around the 461 /// uses in a single block. This is intended to be used as part of a larger 462 /// split, and doesn't call finish(). 463 void splitSingleBlock(const SplitAnalysis::BlockInfo &BI); 464 465 /// splitLiveThroughBlock - Split CurLI in the given block such that it 466 /// enters the block in IntvIn and leaves it in IntvOut. There may be uses in 467 /// the block, but they will be ignored when placing split points. 468 /// 469 /// @param MBBNum Block number. 470 /// @param IntvIn Interval index entering the block. 471 /// @param LeaveBefore When set, leave IntvIn before this point. 472 /// @param IntvOut Interval index leaving the block. 473 /// @param EnterAfter When set, enter IntvOut after this point. 474 void splitLiveThroughBlock(unsigned MBBNum, 475 unsigned IntvIn, SlotIndex LeaveBefore, 476 unsigned IntvOut, SlotIndex EnterAfter); 477 478 /// splitRegInBlock - Split CurLI in the given block such that it enters the 479 /// block in IntvIn and leaves it on the stack (or not at all). Split points 480 /// are placed in a way that avoids putting uses in the stack interval. This 481 /// may require creating a local interval when there is interference. 482 /// 483 /// @param BI Block descriptor. 484 /// @param IntvIn Interval index entering the block. Not 0. 485 /// @param LeaveBefore When set, leave IntvIn before this point. 486 void splitRegInBlock(const SplitAnalysis::BlockInfo &BI, 487 unsigned IntvIn, SlotIndex LeaveBefore); 488 489 /// splitRegOutBlock - Split CurLI in the given block such that it enters the 490 /// block on the stack (or isn't live-in at all) and leaves it in IntvOut. 491 /// Split points are placed to avoid interference and such that the uses are 492 /// not in the stack interval. This may require creating a local interval 493 /// when there is interference. 494 /// 495 /// @param BI Block descriptor. 496 /// @param IntvOut Interval index leaving the block. 497 /// @param EnterAfter When set, enter IntvOut after this point. 498 void splitRegOutBlock(const SplitAnalysis::BlockInfo &BI, 499 unsigned IntvOut, SlotIndex EnterAfter); 500}; 501 502} 503 504#endif 505