SplitKit.h revision 2c0cbce763a258ac58590a8ca3c28ff722093fef
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 FirstUse; ///< First instr using current reg. 80 SlotIndex LastUse; ///< Last instr using current reg. 81 bool LiveThrough; ///< Live in whole block (Templ 5. above). 82 bool LiveIn; ///< Current reg is live in. 83 bool LiveOut; ///< Current reg is live out. 84 }; 85 86private: 87 // Current live interval. 88 const LiveInterval *CurLI; 89 90 /// LastSplitPoint - Last legal split point in each basic block in the current 91 /// function. The first entry is the first terminator, the second entry is the 92 /// last valid split point for a variable that is live in to a landing pad 93 /// successor. 94 SmallVector<std::pair<SlotIndex, SlotIndex>, 8> LastSplitPoint; 95 96 /// UseBlocks - Blocks where CurLI has uses. 97 SmallVector<BlockInfo, 8> UseBlocks; 98 99 /// NumGapBlocks - Number of duplicate entries in UseBlocks for blocks where 100 /// the live range has a gap. 101 unsigned NumGapBlocks; 102 103 /// ThroughBlocks - Block numbers where CurLI is live through without uses. 104 BitVector ThroughBlocks; 105 106 /// NumThroughBlocks - Number of live-through blocks. 107 unsigned NumThroughBlocks; 108 109 /// DidRepairRange - analyze was forced to shrinkToUses(). 110 bool DidRepairRange; 111 112 SlotIndex computeLastSplitPoint(unsigned Num); 113 114 // Sumarize statistics by counting instructions using CurLI. 115 void analyzeUses(); 116 117 /// calcLiveBlockInfo - Compute per-block information about CurLI. 118 bool calcLiveBlockInfo(); 119 120public: 121 SplitAnalysis(const VirtRegMap &vrm, const LiveIntervals &lis, 122 const MachineLoopInfo &mli); 123 124 /// analyze - set CurLI to the specified interval, and analyze how it may be 125 /// split. 126 void analyze(const LiveInterval *li); 127 128 /// didRepairRange() - Returns true if CurLI was invalid and has been repaired 129 /// by analyze(). This really shouldn't happen, but sometimes the coalescer 130 /// can create live ranges that end in mid-air. 131 bool didRepairRange() const { return DidRepairRange; } 132 133 /// clear - clear all data structures so SplitAnalysis is ready to analyze a 134 /// new interval. 135 void clear(); 136 137 /// getParent - Return the last analyzed interval. 138 const LiveInterval &getParent() const { return *CurLI; } 139 140 /// getLastSplitPoint - Return that base index of the last valid split point 141 /// in the basic block numbered Num. 142 SlotIndex getLastSplitPoint(unsigned Num) { 143 // Inline the common simple case. 144 if (LastSplitPoint[Num].first.isValid() && 145 !LastSplitPoint[Num].second.isValid()) 146 return LastSplitPoint[Num].first; 147 return computeLastSplitPoint(Num); 148 } 149 150 /// isOriginalEndpoint - Return true if the original live range was killed or 151 /// (re-)defined at Idx. Idx should be the 'def' slot for a normal kill/def, 152 /// and 'use' for an early-clobber def. 153 /// This can be used to recognize code inserted by earlier live range 154 /// splitting. 155 bool isOriginalEndpoint(SlotIndex Idx) const; 156 157 /// getUseBlocks - Return an array of BlockInfo objects for the basic blocks 158 /// where CurLI has uses. 159 ArrayRef<BlockInfo> getUseBlocks() const { return UseBlocks; } 160 161 /// getNumThroughBlocks - Return the number of through blocks. 162 unsigned getNumThroughBlocks() const { return NumThroughBlocks; } 163 164 /// isThroughBlock - Return true if CurLI is live through MBB without uses. 165 bool isThroughBlock(unsigned MBB) const { return ThroughBlocks.test(MBB); } 166 167 /// getThroughBlocks - Return the set of through blocks. 168 const BitVector &getThroughBlocks() const { return ThroughBlocks; } 169 170 /// getNumLiveBlocks - Return the number of blocks where CurLI is live. 171 unsigned getNumLiveBlocks() const { 172 return getUseBlocks().size() - NumGapBlocks + getNumThroughBlocks(); 173 } 174 175 /// countLiveBlocks - Return the number of blocks where li is live. This is 176 /// guaranteed to return the same number as getNumLiveBlocks() after calling 177 /// analyze(li). 178 unsigned countLiveBlocks(const LiveInterval *li) const; 179 180 typedef SmallPtrSet<const MachineBasicBlock*, 16> BlockPtrSet; 181 182 /// getMultiUseBlocks - Add basic blocks to Blocks that may benefit from 183 /// having CurLI split to a new live interval. Return true if Blocks can be 184 /// passed to SplitEditor::splitSingleBlocks. 185 bool getMultiUseBlocks(BlockPtrSet &Blocks); 186}; 187 188 189/// SplitEditor - Edit machine code and LiveIntervals for live range 190/// splitting. 191/// 192/// - Create a SplitEditor from a SplitAnalysis. 193/// - Start a new live interval with openIntv. 194/// - Mark the places where the new interval is entered using enterIntv* 195/// - Mark the ranges where the new interval is used with useIntv* 196/// - Mark the places where the interval is exited with exitIntv*. 197/// - Finish the current interval with closeIntv and repeat from 2. 198/// - Rewrite instructions with finish(). 199/// 200class SplitEditor { 201 SplitAnalysis &SA; 202 LiveIntervals &LIS; 203 VirtRegMap &VRM; 204 MachineRegisterInfo &MRI; 205 MachineDominatorTree &MDT; 206 const TargetInstrInfo &TII; 207 const TargetRegisterInfo &TRI; 208 209 /// Edit - The current parent register and new intervals created. 210 LiveRangeEdit *Edit; 211 212 /// Index into Edit of the currently open interval. 213 /// The index 0 is used for the complement, so the first interval started by 214 /// openIntv will be 1. 215 unsigned OpenIdx; 216 217 typedef IntervalMap<SlotIndex, unsigned> RegAssignMap; 218 219 /// Allocator for the interval map. This will eventually be shared with 220 /// SlotIndexes and LiveIntervals. 221 RegAssignMap::Allocator Allocator; 222 223 /// RegAssign - Map of the assigned register indexes. 224 /// Edit.get(RegAssign.lookup(Idx)) is the register that should be live at 225 /// Idx. 226 RegAssignMap RegAssign; 227 228 typedef DenseMap<std::pair<unsigned, unsigned>, VNInfo*> ValueMap; 229 230 /// Values - keep track of the mapping from parent values to values in the new 231 /// intervals. Given a pair (RegIdx, ParentVNI->id), Values contains: 232 /// 233 /// 1. No entry - the value is not mapped to Edit.get(RegIdx). 234 /// 2. Null - the value is mapped to multiple values in Edit.get(RegIdx). 235 /// Each value is represented by a minimal live range at its def. 236 /// 3. A non-null VNInfo - the value is mapped to a single new value. 237 /// The new value has no live ranges anywhere. 238 ValueMap Values; 239 240 typedef std::pair<VNInfo*, MachineDomTreeNode*> LiveOutPair; 241 typedef IndexedMap<LiveOutPair, MBB2NumberFunctor> LiveOutMap; 242 243 // LiveOutCache - Map each basic block where a new register is live out to the 244 // live-out value and its defining block. 245 // One of these conditions shall be true: 246 // 247 // 1. !LiveOutCache.count(MBB) 248 // 2. LiveOutCache[MBB].second.getNode() == MBB 249 // 3. forall P in preds(MBB): LiveOutCache[P] == LiveOutCache[MBB] 250 // 251 // This is only a cache, the values can be computed as: 252 // 253 // VNI = Edit.get(RegIdx)->getVNInfoAt(LIS.getMBBEndIdx(MBB)) 254 // Node = mbt_[LIS.getMBBFromIndex(VNI->def)] 255 // 256 // The cache is also used as a visited set by extendRange(). It can be shared 257 // by all the new registers because at most one is live out of each block. 258 LiveOutMap LiveOutCache; 259 260 // LiveOutSeen - Indexed by MBB->getNumber(), a bit is set for each valid 261 // entry in LiveOutCache. 262 BitVector LiveOutSeen; 263 264 /// LiveInBlock - Info for updateSSA() about a block where a register is 265 /// live-in. 266 /// The updateSSA caller provides DomNode and Kill inside MBB, updateSSA() 267 /// adds the computed live-in value. 268 struct LiveInBlock { 269 // Dominator tree node for the block. 270 // Cleared by updateSSA when the final value has been determined. 271 MachineDomTreeNode *DomNode; 272 273 // Live-in value filled in by updateSSA once it is known. 274 VNInfo *Value; 275 276 // Position in block where the live-in range ends, or SlotIndex() if the 277 // range passes through the block. 278 SlotIndex Kill; 279 280 LiveInBlock(MachineDomTreeNode *node) : DomNode(node), Value(0) {} 281 }; 282 283 /// LiveInBlocks - List of live-in blocks used by findReachingDefs() and 284 /// updateSSA(). This list is usually empty, it exists here to avoid frequent 285 /// reallocations. 286 SmallVector<LiveInBlock, 16> LiveInBlocks; 287 288 /// defValue - define a value in RegIdx from ParentVNI at Idx. 289 /// Idx does not have to be ParentVNI->def, but it must be contained within 290 /// ParentVNI's live range in ParentLI. The new value is added to the value 291 /// map. 292 /// Return the new LI value. 293 VNInfo *defValue(unsigned RegIdx, const VNInfo *ParentVNI, SlotIndex Idx); 294 295 /// markComplexMapped - Mark ParentVNI as complex mapped in RegIdx regardless 296 /// of the number of defs. 297 void markComplexMapped(unsigned RegIdx, const VNInfo *ParentVNI); 298 299 /// defFromParent - Define Reg from ParentVNI at UseIdx using either 300 /// rematerialization or a COPY from parent. Return the new value. 301 VNInfo *defFromParent(unsigned RegIdx, 302 VNInfo *ParentVNI, 303 SlotIndex UseIdx, 304 MachineBasicBlock &MBB, 305 MachineBasicBlock::iterator I); 306 307 /// extendRange - Extend the live range of Edit.get(RegIdx) so it reaches Idx. 308 /// Insert PHIDefs as needed to preserve SSA form. 309 void extendRange(unsigned RegIdx, SlotIndex Idx); 310 311 /// findReachingDefs - Starting from MBB, add blocks to LiveInBlocks until all 312 /// reaching defs for LI are found. 313 /// @param LI Live interval whose value is needed. 314 /// @param MBB Block where LI should be live-in. 315 /// @param Kill Kill point in MBB. 316 /// @return Unique value seen, or NULL. 317 VNInfo *findReachingDefs(LiveInterval *LI, MachineBasicBlock *MBB, 318 SlotIndex Kill); 319 320 /// updateSSA - Compute and insert PHIDefs such that all blocks in 321 // LiveInBlocks get a known live-in value. Add live ranges to the blocks. 322 void updateSSA(); 323 324 /// transferValues - Transfer values to the new ranges. 325 /// Return true if any ranges were skipped. 326 bool transferValues(); 327 328 /// extendPHIKillRanges - Extend the ranges of all values killed by original 329 /// parent PHIDefs. 330 void extendPHIKillRanges(); 331 332 /// rewriteAssigned - Rewrite all uses of Edit.getReg() to assigned registers. 333 void rewriteAssigned(bool ExtendRanges); 334 335 /// deleteRematVictims - Delete defs that are dead after rematerializing. 336 void deleteRematVictims(); 337 338public: 339 /// Create a new SplitEditor for editing the LiveInterval analyzed by SA. 340 /// Newly created intervals will be appended to newIntervals. 341 SplitEditor(SplitAnalysis &SA, LiveIntervals&, VirtRegMap&, 342 MachineDominatorTree&); 343 344 /// reset - Prepare for a new split. 345 void reset(LiveRangeEdit&); 346 347 /// Create a new virtual register and live interval. 348 /// Return the interval index, starting from 1. Interval index 0 is the 349 /// implicit complement interval. 350 unsigned openIntv(); 351 352 /// currentIntv - Return the current interval index. 353 unsigned currentIntv() const { return OpenIdx; } 354 355 /// selectIntv - Select a previously opened interval index. 356 void selectIntv(unsigned Idx); 357 358 /// enterIntvBefore - Enter the open interval before the instruction at Idx. 359 /// If the parent interval is not live before Idx, a COPY is not inserted. 360 /// Return the beginning of the new live range. 361 SlotIndex enterIntvBefore(SlotIndex Idx); 362 363 /// enterIntvAtEnd - Enter the open interval at the end of MBB. 364 /// Use the open interval from he inserted copy to the MBB end. 365 /// Return the beginning of the new live range. 366 SlotIndex enterIntvAtEnd(MachineBasicBlock &MBB); 367 368 /// useIntv - indicate that all instructions in MBB should use OpenLI. 369 void useIntv(const MachineBasicBlock &MBB); 370 371 /// useIntv - indicate that all instructions in range should use OpenLI. 372 void useIntv(SlotIndex Start, SlotIndex End); 373 374 /// leaveIntvAfter - Leave the open interval after the instruction at Idx. 375 /// Return the end of the live range. 376 SlotIndex leaveIntvAfter(SlotIndex Idx); 377 378 /// leaveIntvBefore - Leave the open interval before the instruction at Idx. 379 /// Return the end of the live range. 380 SlotIndex leaveIntvBefore(SlotIndex Idx); 381 382 /// leaveIntvAtTop - Leave the interval at the top of MBB. 383 /// Add liveness from the MBB top to the copy. 384 /// Return the end of the live range. 385 SlotIndex leaveIntvAtTop(MachineBasicBlock &MBB); 386 387 /// overlapIntv - Indicate that all instructions in range should use the open 388 /// interval, but also let the complement interval be live. 389 /// 390 /// This doubles the register pressure, but is sometimes required to deal with 391 /// register uses after the last valid split point. 392 /// 393 /// The Start index should be a return value from a leaveIntv* call, and End 394 /// should be in the same basic block. The parent interval must have the same 395 /// value across the range. 396 /// 397 void overlapIntv(SlotIndex Start, SlotIndex End); 398 399 /// finish - after all the new live ranges have been created, compute the 400 /// remaining live range, and rewrite instructions to use the new registers. 401 /// @param LRMap When not null, this vector will map each live range in Edit 402 /// back to the indices returned by openIntv. 403 /// There may be extra indices created by dead code elimination. 404 void finish(SmallVectorImpl<unsigned> *LRMap = 0); 405 406 /// dump - print the current interval maping to dbgs(). 407 void dump() const; 408 409 // ===--- High level methods ---=== 410 411 /// splitSingleBlock - Split CurLI into a separate live interval around the 412 /// uses in a single block. This is intended to be used as part of a larger 413 /// split, and doesn't call finish(). 414 void splitSingleBlock(const SplitAnalysis::BlockInfo &BI); 415 416 /// splitSingleBlocks - Split CurLI into a separate live interval inside each 417 /// basic block in Blocks. 418 void splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks); 419}; 420 421} 422 423#endif 424