SplitKit.h revision 6796e4fc889d99c4ad97ec5ad86e4c8cf75e52a4
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 SlotIndex computeLastSplitPoint(unsigned Num); 101 102 // Sumarize statistics by counting instructions using CurLI. 103 void analyzeUses(); 104 105 /// calcLiveBlockInfo - Compute per-block information about CurLI. 106 bool calcLiveBlockInfo(); 107 108public: 109 SplitAnalysis(const VirtRegMap &vrm, const LiveIntervals &lis, 110 const MachineLoopInfo &mli); 111 112 /// analyze - set CurLI to the specified interval, and analyze how it may be 113 /// split. 114 void analyze(const LiveInterval *li); 115 116 /// clear - clear all data structures so SplitAnalysis is ready to analyze a 117 /// new interval. 118 void clear(); 119 120 /// getParent - Return the last analyzed interval. 121 const LiveInterval &getParent() const { return *CurLI; } 122 123 /// getLastSplitPoint - Return that base index of the last valid split point 124 /// in the basic block numbered Num. 125 SlotIndex getLastSplitPoint(unsigned Num) { 126 // Inline the common simple case. 127 if (LastSplitPoint[Num].first.isValid() && 128 !LastSplitPoint[Num].second.isValid()) 129 return LastSplitPoint[Num].first; 130 return computeLastSplitPoint(Num); 131 } 132 133 /// isOriginalEndpoint - Return true if the original live range was killed or 134 /// (re-)defined at Idx. Idx should be the 'def' slot for a normal kill/def, 135 /// and 'use' for an early-clobber def. 136 /// This can be used to recognize code inserted by earlier live range 137 /// splitting. 138 bool isOriginalEndpoint(SlotIndex Idx) const; 139 140 /// getUseBlocks - Return an array of BlockInfo objects for the basic blocks 141 /// where CurLI has uses. 142 ArrayRef<BlockInfo> getUseBlocks() { return UseBlocks; } 143 144 /// getNumThroughBlocks - Return the number of through blocks. 145 unsigned getNumThroughBlocks() const { return NumThroughBlocks; } 146 147 /// isThroughBlock - Return true if CurLI is live through MBB without uses. 148 bool isThroughBlock(unsigned MBB) const { return ThroughBlocks.test(MBB); } 149 150 /// getThroughBlocks - Return the set of through blocks. 151 const BitVector &getThroughBlocks() const { return ThroughBlocks; } 152 153 typedef SmallPtrSet<const MachineBasicBlock*, 16> BlockPtrSet; 154 155 /// getMultiUseBlocks - Add basic blocks to Blocks that may benefit from 156 /// having CurLI split to a new live interval. Return true if Blocks can be 157 /// passed to SplitEditor::splitSingleBlocks. 158 bool getMultiUseBlocks(BlockPtrSet &Blocks); 159}; 160 161 162/// SplitEditor - Edit machine code and LiveIntervals for live range 163/// splitting. 164/// 165/// - Create a SplitEditor from a SplitAnalysis. 166/// - Start a new live interval with openIntv. 167/// - Mark the places where the new interval is entered using enterIntv* 168/// - Mark the ranges where the new interval is used with useIntv* 169/// - Mark the places where the interval is exited with exitIntv*. 170/// - Finish the current interval with closeIntv and repeat from 2. 171/// - Rewrite instructions with finish(). 172/// 173class SplitEditor { 174 SplitAnalysis &SA; 175 LiveIntervals &LIS; 176 VirtRegMap &VRM; 177 MachineRegisterInfo &MRI; 178 MachineDominatorTree &MDT; 179 const TargetInstrInfo &TII; 180 const TargetRegisterInfo &TRI; 181 182 /// Edit - The current parent register and new intervals created. 183 LiveRangeEdit *Edit; 184 185 /// Index into Edit of the currently open interval. 186 /// The index 0 is used for the complement, so the first interval started by 187 /// openIntv will be 1. 188 unsigned OpenIdx; 189 190 typedef IntervalMap<SlotIndex, unsigned> RegAssignMap; 191 192 /// Allocator for the interval map. This will eventually be shared with 193 /// SlotIndexes and LiveIntervals. 194 RegAssignMap::Allocator Allocator; 195 196 /// RegAssign - Map of the assigned register indexes. 197 /// Edit.get(RegAssign.lookup(Idx)) is the register that should be live at 198 /// Idx. 199 RegAssignMap RegAssign; 200 201 typedef DenseMap<std::pair<unsigned, unsigned>, VNInfo*> ValueMap; 202 203 /// Values - keep track of the mapping from parent values to values in the new 204 /// intervals. Given a pair (RegIdx, ParentVNI->id), Values contains: 205 /// 206 /// 1. No entry - the value is not mapped to Edit.get(RegIdx). 207 /// 2. Null - the value is mapped to multiple values in Edit.get(RegIdx). 208 /// Each value is represented by a minimal live range at its def. 209 /// 3. A non-null VNInfo - the value is mapped to a single new value. 210 /// The new value has no live ranges anywhere. 211 ValueMap Values; 212 213 typedef std::pair<VNInfo*, MachineDomTreeNode*> LiveOutPair; 214 typedef IndexedMap<LiveOutPair, MBB2NumberFunctor> LiveOutMap; 215 216 // LiveOutCache - Map each basic block where a new register is live out to the 217 // live-out value and its defining block. 218 // One of these conditions shall be true: 219 // 220 // 1. !LiveOutCache.count(MBB) 221 // 2. LiveOutCache[MBB].second.getNode() == MBB 222 // 3. forall P in preds(MBB): LiveOutCache[P] == LiveOutCache[MBB] 223 // 224 // This is only a cache, the values can be computed as: 225 // 226 // VNI = Edit.get(RegIdx)->getVNInfoAt(LIS.getMBBEndIdx(MBB)) 227 // Node = mbt_[LIS.getMBBFromIndex(VNI->def)] 228 // 229 // The cache is also used as a visited set by extendRange(). It can be shared 230 // by all the new registers because at most one is live out of each block. 231 LiveOutMap LiveOutCache; 232 233 // LiveOutSeen - Indexed by MBB->getNumber(), a bit is set for each valid 234 // entry in LiveOutCache. 235 BitVector LiveOutSeen; 236 237 /// LiveInBlock - Info for updateSSA() about a block where a register is 238 /// live-in. 239 /// The updateSSA caller provides DomNode and Kill inside MBB, updateSSA() 240 /// adds the computed live-in value. 241 struct LiveInBlock { 242 // Dominator tree node for the block. 243 // Cleared by updateSSA when the final value has been determined. 244 MachineDomTreeNode *DomNode; 245 246 // Live-in value filled in by updateSSA once it is known. 247 VNInfo *Value; 248 249 // Position in block where the live-in range ends, or SlotIndex() if the 250 // range passes through the block. 251 SlotIndex Kill; 252 253 LiveInBlock(MachineDomTreeNode *node) : DomNode(node), Value(0) {} 254 }; 255 256 /// LiveInBlocks - List of live-in blocks used by findReachingDefs() and 257 /// updateSSA(). This list is usually empty, it exists here to avoid frequent 258 /// reallocations. 259 SmallVector<LiveInBlock, 16> LiveInBlocks; 260 261 /// defValue - define a value in RegIdx from ParentVNI at Idx. 262 /// Idx does not have to be ParentVNI->def, but it must be contained within 263 /// ParentVNI's live range in ParentLI. The new value is added to the value 264 /// map. 265 /// Return the new LI value. 266 VNInfo *defValue(unsigned RegIdx, const VNInfo *ParentVNI, SlotIndex Idx); 267 268 /// markComplexMapped - Mark ParentVNI as complex mapped in RegIdx regardless 269 /// of the number of defs. 270 void markComplexMapped(unsigned RegIdx, const VNInfo *ParentVNI); 271 272 /// defFromParent - Define Reg from ParentVNI at UseIdx using either 273 /// rematerialization or a COPY from parent. Return the new value. 274 VNInfo *defFromParent(unsigned RegIdx, 275 VNInfo *ParentVNI, 276 SlotIndex UseIdx, 277 MachineBasicBlock &MBB, 278 MachineBasicBlock::iterator I); 279 280 /// extendRange - Extend the live range of Edit.get(RegIdx) so it reaches Idx. 281 /// Insert PHIDefs as needed to preserve SSA form. 282 void extendRange(unsigned RegIdx, SlotIndex Idx); 283 284 /// findReachingDefs - Starting from MBB, add blocks to LiveInBlocks until all 285 /// reaching defs for LI are found. 286 /// @param LI Live interval whose value is needed. 287 /// @param MBB Block where LI should be live-in. 288 /// @param Kill Kill point in MBB. 289 /// @return Unique value seen, or NULL. 290 VNInfo *findReachingDefs(LiveInterval *LI, MachineBasicBlock *MBB, 291 SlotIndex Kill); 292 293 /// updateSSA - Compute and insert PHIDefs such that all blocks in 294 // LiveInBlocks get a known live-in value. Add live ranges to the blocks. 295 void updateSSA(); 296 297 /// transferValues - Transfer values to the new ranges. 298 /// Return true if any ranges were skipped. 299 bool transferValues(); 300 301 /// extendPHIKillRanges - Extend the ranges of all values killed by original 302 /// parent PHIDefs. 303 void extendPHIKillRanges(); 304 305 /// rewriteAssigned - Rewrite all uses of Edit.getReg() to assigned registers. 306 void rewriteAssigned(bool ExtendRanges); 307 308 /// deleteRematVictims - Delete defs that are dead after rematerializing. 309 void deleteRematVictims(); 310 311public: 312 /// Create a new SplitEditor for editing the LiveInterval analyzed by SA. 313 /// Newly created intervals will be appended to newIntervals. 314 SplitEditor(SplitAnalysis &SA, LiveIntervals&, VirtRegMap&, 315 MachineDominatorTree&); 316 317 /// reset - Prepare for a new split. 318 void reset(LiveRangeEdit&); 319 320 /// Create a new virtual register and live interval. 321 /// Return the interval index, starting from 1. Interval index 0 is the 322 /// implicit complement interval. 323 unsigned openIntv(); 324 325 /// currentIntv - Return the current interval index. 326 unsigned currentIntv() const { return OpenIdx; } 327 328 /// selectIntv - Select a previously opened interval index. 329 void selectIntv(unsigned Idx); 330 331 /// enterIntvBefore - Enter the open interval before the instruction at Idx. 332 /// If the parent interval is not live before Idx, a COPY is not inserted. 333 /// Return the beginning of the new live range. 334 SlotIndex enterIntvBefore(SlotIndex Idx); 335 336 /// enterIntvAtEnd - Enter the open interval at the end of MBB. 337 /// Use the open interval from he inserted copy to the MBB end. 338 /// Return the beginning of the new live range. 339 SlotIndex enterIntvAtEnd(MachineBasicBlock &MBB); 340 341 /// useIntv - indicate that all instructions in MBB should use OpenLI. 342 void useIntv(const MachineBasicBlock &MBB); 343 344 /// useIntv - indicate that all instructions in range should use OpenLI. 345 void useIntv(SlotIndex Start, SlotIndex End); 346 347 /// leaveIntvAfter - Leave the open interval after the instruction at Idx. 348 /// Return the end of the live range. 349 SlotIndex leaveIntvAfter(SlotIndex Idx); 350 351 /// leaveIntvBefore - Leave the open interval before the instruction at Idx. 352 /// Return the end of the live range. 353 SlotIndex leaveIntvBefore(SlotIndex Idx); 354 355 /// leaveIntvAtTop - Leave the interval at the top of MBB. 356 /// Add liveness from the MBB top to the copy. 357 /// Return the end of the live range. 358 SlotIndex leaveIntvAtTop(MachineBasicBlock &MBB); 359 360 /// overlapIntv - Indicate that all instructions in range should use the open 361 /// interval, but also let the complement interval be live. 362 /// 363 /// This doubles the register pressure, but is sometimes required to deal with 364 /// register uses after the last valid split point. 365 /// 366 /// The Start index should be a return value from a leaveIntv* call, and End 367 /// should be in the same basic block. The parent interval must have the same 368 /// value across the range. 369 /// 370 void overlapIntv(SlotIndex Start, SlotIndex End); 371 372 /// finish - after all the new live ranges have been created, compute the 373 /// remaining live range, and rewrite instructions to use the new registers. 374 /// @param LRMap When not null, this vector will map each live range in Edit 375 /// back to the indices returned by openIntv. 376 /// There may be extra indices created by dead code elimination. 377 void finish(SmallVectorImpl<unsigned> *LRMap = 0); 378 379 /// dump - print the current interval maping to dbgs(). 380 void dump() const; 381 382 // ===--- High level methods ---=== 383 384 /// splitSingleBlock - Split CurLI into a separate live interval around the 385 /// uses in a single block. This is intended to be used as part of a larger 386 /// split, and doesn't call finish(). 387 void splitSingleBlock(const SplitAnalysis::BlockInfo &BI); 388 389 /// splitSingleBlocks - Split CurLI into a separate live interval inside each 390 /// basic block in Blocks. 391 void splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks); 392}; 393 394} 395 396#endif 397