SplitKit.h revision 626d6fb1903e74337b257c5e165944bcd1273e65
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. 67 /// 5. |---o---o---| Live-through with uses or defs. 68 /// 6. |-----------| Live-through without uses. Transparent. 69 /// 70 struct BlockInfo { 71 MachineBasicBlock *MBB; 72 SlotIndex FirstUse; ///< First instr using current reg. 73 SlotIndex LastUse; ///< Last instr using current reg. 74 SlotIndex Kill; ///< Interval end point inside block. 75 SlotIndex Def; ///< Interval start point inside block. 76 bool LiveThrough; ///< Live in whole block (Templ 5. or 6. above). 77 bool LiveIn; ///< Current reg is live in. 78 bool LiveOut; ///< Current reg is live out. 79 }; 80 81private: 82 // Current live interval. 83 const LiveInterval *CurLI; 84 85 /// LastSplitPoint - Last legal split point in each basic block in the current 86 /// function. The first entry is the first terminator, the second entry is the 87 /// last valid split point for a variable that is live in to a landing pad 88 /// successor. 89 SmallVector<std::pair<SlotIndex, SlotIndex>, 8> LastSplitPoint; 90 91 /// UseBlocks - Blocks where CurLI has uses. 92 SmallVector<BlockInfo, 8> UseBlocks; 93 94 /// ThroughBlocks - Block numbers where CurLI is live through without uses. 95 BitVector ThroughBlocks; 96 97 /// NumThroughBlocks - Number of live-through blocks. 98 unsigned NumThroughBlocks; 99 100 /// DidRepairRange - analyze was forced to shrinkToUses(). 101 bool DidRepairRange; 102 103 SlotIndex computeLastSplitPoint(unsigned Num); 104 105 // Sumarize statistics by counting instructions using CurLI. 106 void analyzeUses(); 107 108 /// calcLiveBlockInfo - Compute per-block information about CurLI. 109 bool calcLiveBlockInfo(); 110 111public: 112 SplitAnalysis(const VirtRegMap &vrm, const LiveIntervals &lis, 113 const MachineLoopInfo &mli); 114 115 /// analyze - set CurLI to the specified interval, and analyze how it may be 116 /// split. 117 void analyze(const LiveInterval *li); 118 119 /// didRepairRange() - Returns true if CurLI was invalid and has been repaired 120 /// by analyze(). This really shouldn't happen, but sometimes the coalescer 121 /// can create live ranges that end in mid-air. 122 bool didRepairRange() const { return DidRepairRange; } 123 124 /// clear - clear all data structures so SplitAnalysis is ready to analyze a 125 /// new interval. 126 void clear(); 127 128 /// getParent - Return the last analyzed interval. 129 const LiveInterval &getParent() const { return *CurLI; } 130 131 /// getLastSplitPoint - Return that base index of the last valid split point 132 /// in the basic block numbered Num. 133 SlotIndex getLastSplitPoint(unsigned Num) { 134 // Inline the common simple case. 135 if (LastSplitPoint[Num].first.isValid() && 136 !LastSplitPoint[Num].second.isValid()) 137 return LastSplitPoint[Num].first; 138 return computeLastSplitPoint(Num); 139 } 140 141 /// isOriginalEndpoint - Return true if the original live range was killed or 142 /// (re-)defined at Idx. Idx should be the 'def' slot for a normal kill/def, 143 /// and 'use' for an early-clobber def. 144 /// This can be used to recognize code inserted by earlier live range 145 /// splitting. 146 bool isOriginalEndpoint(SlotIndex Idx) const; 147 148 /// getUseBlocks - Return an array of BlockInfo objects for the basic blocks 149 /// where CurLI has uses. 150 ArrayRef<BlockInfo> getUseBlocks() const { return UseBlocks; } 151 152 /// getNumThroughBlocks - Return the number of through blocks. 153 unsigned getNumThroughBlocks() const { return NumThroughBlocks; } 154 155 /// isThroughBlock - Return true if CurLI is live through MBB without uses. 156 bool isThroughBlock(unsigned MBB) const { return ThroughBlocks.test(MBB); } 157 158 /// getThroughBlocks - Return the set of through blocks. 159 const BitVector &getThroughBlocks() const { return ThroughBlocks; } 160 161 /// getNumLiveBlocks - Return the number of blocks where CurLI is live. 162 unsigned getNumLiveBlocks() const { 163 return getUseBlocks().size() + getNumThroughBlocks(); 164 } 165 166 /// countLiveBlocks - Return the number of blocks where li is live. This is 167 /// guaranteed to return the same number as getNumLiveBlocks() after calling 168 /// analyze(li). 169 unsigned countLiveBlocks(const LiveInterval *li) const; 170 171 typedef SmallPtrSet<const MachineBasicBlock*, 16> BlockPtrSet; 172 173 /// getMultiUseBlocks - Add basic blocks to Blocks that may benefit from 174 /// having CurLI split to a new live interval. Return true if Blocks can be 175 /// passed to SplitEditor::splitSingleBlocks. 176 bool getMultiUseBlocks(BlockPtrSet &Blocks); 177}; 178 179 180/// SplitEditor - Edit machine code and LiveIntervals for live range 181/// splitting. 182/// 183/// - Create a SplitEditor from a SplitAnalysis. 184/// - Start a new live interval with openIntv. 185/// - Mark the places where the new interval is entered using enterIntv* 186/// - Mark the ranges where the new interval is used with useIntv* 187/// - Mark the places where the interval is exited with exitIntv*. 188/// - Finish the current interval with closeIntv and repeat from 2. 189/// - Rewrite instructions with finish(). 190/// 191class SplitEditor { 192 SplitAnalysis &SA; 193 LiveIntervals &LIS; 194 VirtRegMap &VRM; 195 MachineRegisterInfo &MRI; 196 MachineDominatorTree &MDT; 197 const TargetInstrInfo &TII; 198 const TargetRegisterInfo &TRI; 199 200 /// Edit - The current parent register and new intervals created. 201 LiveRangeEdit *Edit; 202 203 /// Index into Edit of the currently open interval. 204 /// The index 0 is used for the complement, so the first interval started by 205 /// openIntv will be 1. 206 unsigned OpenIdx; 207 208 typedef IntervalMap<SlotIndex, unsigned> RegAssignMap; 209 210 /// Allocator for the interval map. This will eventually be shared with 211 /// SlotIndexes and LiveIntervals. 212 RegAssignMap::Allocator Allocator; 213 214 /// RegAssign - Map of the assigned register indexes. 215 /// Edit.get(RegAssign.lookup(Idx)) is the register that should be live at 216 /// Idx. 217 RegAssignMap RegAssign; 218 219 typedef DenseMap<std::pair<unsigned, unsigned>, VNInfo*> ValueMap; 220 221 /// Values - keep track of the mapping from parent values to values in the new 222 /// intervals. Given a pair (RegIdx, ParentVNI->id), Values contains: 223 /// 224 /// 1. No entry - the value is not mapped to Edit.get(RegIdx). 225 /// 2. Null - the value is mapped to multiple values in Edit.get(RegIdx). 226 /// Each value is represented by a minimal live range at its def. 227 /// 3. A non-null VNInfo - the value is mapped to a single new value. 228 /// The new value has no live ranges anywhere. 229 ValueMap Values; 230 231 typedef std::pair<VNInfo*, MachineDomTreeNode*> LiveOutPair; 232 typedef IndexedMap<LiveOutPair, MBB2NumberFunctor> LiveOutMap; 233 234 // LiveOutCache - Map each basic block where a new register is live out to the 235 // live-out value and its defining block. 236 // One of these conditions shall be true: 237 // 238 // 1. !LiveOutCache.count(MBB) 239 // 2. LiveOutCache[MBB].second.getNode() == MBB 240 // 3. forall P in preds(MBB): LiveOutCache[P] == LiveOutCache[MBB] 241 // 242 // This is only a cache, the values can be computed as: 243 // 244 // VNI = Edit.get(RegIdx)->getVNInfoAt(LIS.getMBBEndIdx(MBB)) 245 // Node = mbt_[LIS.getMBBFromIndex(VNI->def)] 246 // 247 // The cache is also used as a visited set by extendRange(). It can be shared 248 // by all the new registers because at most one is live out of each block. 249 LiveOutMap LiveOutCache; 250 251 // LiveOutSeen - Indexed by MBB->getNumber(), a bit is set for each valid 252 // entry in LiveOutCache. 253 BitVector LiveOutSeen; 254 255 /// LiveInBlock - Info for updateSSA() about a block where a register is 256 /// live-in. 257 /// The updateSSA caller provides DomNode and Kill inside MBB, updateSSA() 258 /// adds the computed live-in value. 259 struct LiveInBlock { 260 // Dominator tree node for the block. 261 // Cleared by updateSSA when the final value has been determined. 262 MachineDomTreeNode *DomNode; 263 264 // Live-in value filled in by updateSSA once it is known. 265 VNInfo *Value; 266 267 // Position in block where the live-in range ends, or SlotIndex() if the 268 // range passes through the block. 269 SlotIndex Kill; 270 271 LiveInBlock(MachineDomTreeNode *node) : DomNode(node), Value(0) {} 272 }; 273 274 /// LiveInBlocks - List of live-in blocks used by findReachingDefs() and 275 /// updateSSA(). This list is usually empty, it exists here to avoid frequent 276 /// reallocations. 277 SmallVector<LiveInBlock, 16> LiveInBlocks; 278 279 /// defValue - define a value in RegIdx from ParentVNI at Idx. 280 /// Idx does not have to be ParentVNI->def, but it must be contained within 281 /// ParentVNI's live range in ParentLI. The new value is added to the value 282 /// map. 283 /// Return the new LI value. 284 VNInfo *defValue(unsigned RegIdx, const VNInfo *ParentVNI, SlotIndex Idx); 285 286 /// markComplexMapped - Mark ParentVNI as complex mapped in RegIdx regardless 287 /// of the number of defs. 288 void markComplexMapped(unsigned RegIdx, const VNInfo *ParentVNI); 289 290 /// defFromParent - Define Reg from ParentVNI at UseIdx using either 291 /// rematerialization or a COPY from parent. Return the new value. 292 VNInfo *defFromParent(unsigned RegIdx, 293 VNInfo *ParentVNI, 294 SlotIndex UseIdx, 295 MachineBasicBlock &MBB, 296 MachineBasicBlock::iterator I); 297 298 /// extendRange - Extend the live range of Edit.get(RegIdx) so it reaches Idx. 299 /// Insert PHIDefs as needed to preserve SSA form. 300 void extendRange(unsigned RegIdx, SlotIndex Idx); 301 302 /// findReachingDefs - Starting from MBB, add blocks to LiveInBlocks until all 303 /// reaching defs for LI are found. 304 /// @param LI Live interval whose value is needed. 305 /// @param MBB Block where LI should be live-in. 306 /// @param Kill Kill point in MBB. 307 /// @return Unique value seen, or NULL. 308 VNInfo *findReachingDefs(LiveInterval *LI, MachineBasicBlock *MBB, 309 SlotIndex Kill); 310 311 /// updateSSA - Compute and insert PHIDefs such that all blocks in 312 // LiveInBlocks get a known live-in value. Add live ranges to the blocks. 313 void updateSSA(); 314 315 /// transferValues - Transfer values to the new ranges. 316 /// Return true if any ranges were skipped. 317 bool transferValues(); 318 319 /// extendPHIKillRanges - Extend the ranges of all values killed by original 320 /// parent PHIDefs. 321 void extendPHIKillRanges(); 322 323 /// rewriteAssigned - Rewrite all uses of Edit.getReg() to assigned registers. 324 void rewriteAssigned(bool ExtendRanges); 325 326 /// deleteRematVictims - Delete defs that are dead after rematerializing. 327 void deleteRematVictims(); 328 329public: 330 /// Create a new SplitEditor for editing the LiveInterval analyzed by SA. 331 /// Newly created intervals will be appended to newIntervals. 332 SplitEditor(SplitAnalysis &SA, LiveIntervals&, VirtRegMap&, 333 MachineDominatorTree&); 334 335 /// reset - Prepare for a new split. 336 void reset(LiveRangeEdit&); 337 338 /// Create a new virtual register and live interval. 339 /// Return the interval index, starting from 1. Interval index 0 is the 340 /// implicit complement interval. 341 unsigned openIntv(); 342 343 /// currentIntv - Return the current interval index. 344 unsigned currentIntv() const { return OpenIdx; } 345 346 /// selectIntv - Select a previously opened interval index. 347 void selectIntv(unsigned Idx); 348 349 /// enterIntvBefore - Enter the open interval before the instruction at Idx. 350 /// If the parent interval is not live before Idx, a COPY is not inserted. 351 /// Return the beginning of the new live range. 352 SlotIndex enterIntvBefore(SlotIndex Idx); 353 354 /// enterIntvAtEnd - Enter the open interval at the end of MBB. 355 /// Use the open interval from he inserted copy to the MBB end. 356 /// Return the beginning of the new live range. 357 SlotIndex enterIntvAtEnd(MachineBasicBlock &MBB); 358 359 /// useIntv - indicate that all instructions in MBB should use OpenLI. 360 void useIntv(const MachineBasicBlock &MBB); 361 362 /// useIntv - indicate that all instructions in range should use OpenLI. 363 void useIntv(SlotIndex Start, SlotIndex End); 364 365 /// leaveIntvAfter - Leave the open interval after the instruction at Idx. 366 /// Return the end of the live range. 367 SlotIndex leaveIntvAfter(SlotIndex Idx); 368 369 /// leaveIntvBefore - Leave the open interval before the instruction at Idx. 370 /// Return the end of the live range. 371 SlotIndex leaveIntvBefore(SlotIndex Idx); 372 373 /// leaveIntvAtTop - Leave the interval at the top of MBB. 374 /// Add liveness from the MBB top to the copy. 375 /// Return the end of the live range. 376 SlotIndex leaveIntvAtTop(MachineBasicBlock &MBB); 377 378 /// overlapIntv - Indicate that all instructions in range should use the open 379 /// interval, but also let the complement interval be live. 380 /// 381 /// This doubles the register pressure, but is sometimes required to deal with 382 /// register uses after the last valid split point. 383 /// 384 /// The Start index should be a return value from a leaveIntv* call, and End 385 /// should be in the same basic block. The parent interval must have the same 386 /// value across the range. 387 /// 388 void overlapIntv(SlotIndex Start, SlotIndex End); 389 390 /// finish - after all the new live ranges have been created, compute the 391 /// remaining live range, and rewrite instructions to use the new registers. 392 /// @param LRMap When not null, this vector will map each live range in Edit 393 /// back to the indices returned by openIntv. 394 /// There may be extra indices created by dead code elimination. 395 void finish(SmallVectorImpl<unsigned> *LRMap = 0); 396 397 /// dump - print the current interval maping to dbgs(). 398 void dump() const; 399 400 // ===--- High level methods ---=== 401 402 /// splitSingleBlock - Split CurLI into a separate live interval around the 403 /// uses in a single block. This is intended to be used as part of a larger 404 /// split, and doesn't call finish(). 405 void splitSingleBlock(const SplitAnalysis::BlockInfo &BI); 406 407 /// splitSingleBlocks - Split CurLI into a separate live interval inside each 408 /// basic block in Blocks. 409 void splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks); 410}; 411 412} 413 414#endif 415