SplitKit.h revision 06c0f25499fd502668ca720b0fea4a4dfe6eb44a
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/IntervalMap.h" 17#include "llvm/ADT/SmallPtrSet.h" 18#include "llvm/CodeGen/SlotIndexes.h" 19 20namespace llvm { 21 22class ConnectedVNInfoEqClasses; 23class LiveInterval; 24class LiveIntervals; 25class LiveRangeEdit; 26class MachineInstr; 27class MachineLoopInfo; 28class MachineRegisterInfo; 29class TargetInstrInfo; 30class TargetRegisterInfo; 31class VirtRegMap; 32class VNInfo; 33class raw_ostream; 34 35/// At some point we should just include MachineDominators.h: 36class MachineDominatorTree; 37template <class NodeT> class DomTreeNodeBase; 38typedef DomTreeNodeBase<MachineBasicBlock> MachineDomTreeNode; 39 40 41/// SplitAnalysis - Analyze a LiveInterval, looking for live range splitting 42/// opportunities. 43class SplitAnalysis { 44public: 45 const MachineFunction &MF; 46 const VirtRegMap &VRM; 47 const LiveIntervals &LIS; 48 const MachineLoopInfo &Loops; 49 const TargetInstrInfo &TII; 50 51 // Instructions using the the current register. 52 typedef SmallPtrSet<const MachineInstr*, 16> InstrPtrSet; 53 InstrPtrSet UsingInstrs; 54 55 // Sorted slot indexes of using instructions. 56 SmallVector<SlotIndex, 8> UseSlots; 57 58 // The number of instructions using CurLI in each basic block. 59 typedef DenseMap<const MachineBasicBlock*, unsigned> BlockCountMap; 60 BlockCountMap UsingBlocks; 61 62 /// Additional information about basic blocks where the current variable is 63 /// live. Such a block will look like one of these templates: 64 /// 65 /// 1. | o---x | Internal to block. Variable is only live in this block. 66 /// 2. |---x | Live-in, kill. 67 /// 3. | o---| Def, live-out. 68 /// 4. |---x o---| Live-in, kill, def, live-out. 69 /// 5. |---o---o---| Live-through with uses or defs. 70 /// 6. |-----------| Live-through without uses. Transparent. 71 /// 72 struct BlockInfo { 73 MachineBasicBlock *MBB; 74 SlotIndex FirstUse; ///< First instr using current reg. 75 SlotIndex LastUse; ///< Last instr using current reg. 76 SlotIndex Kill; ///< Interval end point inside block. 77 SlotIndex Def; ///< Interval start point inside block. 78 /// Last possible point for splitting live ranges. 79 SlotIndex LastSplitPoint; 80 bool Uses; ///< Current reg has uses or defs in block. 81 bool LiveThrough; ///< Live in whole block (Templ 5. or 6. above). 82 bool LiveIn; ///< Current reg is live in. 83 bool LiveOut; ///< Current reg is live out. 84 85 // Per-interference pattern scratch data. 86 bool OverlapEntry; ///< Interference overlaps entering interval. 87 bool OverlapExit; ///< Interference overlaps exiting interval. 88 }; 89 90 /// Basic blocks where var is live. This array is parallel to 91 /// SpillConstraints. 92 SmallVector<BlockInfo, 8> LiveBlocks; 93 94private: 95 // Current live interval. 96 const LiveInterval *CurLI; 97 98 // Sumarize statistics by counting instructions using CurLI. 99 void analyzeUses(); 100 101 /// calcLiveBlockInfo - Compute per-block information about CurLI. 102 void calcLiveBlockInfo(); 103 104 /// canAnalyzeBranch - Return true if MBB ends in a branch that can be 105 /// analyzed. 106 bool canAnalyzeBranch(const MachineBasicBlock *MBB); 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 /// hasUses - Return true if MBB has any uses of CurLI. 124 bool hasUses(const MachineBasicBlock *MBB) const { 125 return UsingBlocks.lookup(MBB); 126 } 127 128 /// isOriginalEndpoint - Return true if the original live range was killed or 129 /// (re-)defined at Idx. Idx should be the 'def' slot for a normal kill/def, 130 /// and 'use' for an early-clobber def. 131 /// This can be used to recognize code inserted by earlier live range 132 /// splitting. 133 bool isOriginalEndpoint(SlotIndex Idx) const; 134 135 typedef SmallPtrSet<const MachineBasicBlock*, 16> BlockPtrSet; 136 137 // Print a set of blocks with use counts. 138 void print(const BlockPtrSet&, raw_ostream&) const; 139 140 /// getMultiUseBlocks - Add basic blocks to Blocks that may benefit from 141 /// having CurLI split to a new live interval. Return true if Blocks can be 142 /// passed to SplitEditor::splitSingleBlocks. 143 bool getMultiUseBlocks(BlockPtrSet &Blocks); 144 145 /// getBlockForInsideSplit - If CurLI is contained inside a single basic 146 /// block, and it would pay to subdivide the interval inside that block, 147 /// return it. Otherwise return NULL. The returned block can be passed to 148 /// SplitEditor::splitInsideBlock. 149 const MachineBasicBlock *getBlockForInsideSplit(); 150}; 151 152 153/// LiveIntervalMap - Map values from a large LiveInterval into a small 154/// interval that is a subset. Insert phi-def values as needed. This class is 155/// used by SplitEditor to create new smaller LiveIntervals. 156/// 157/// ParentLI is the larger interval, LI is the subset interval. Every value 158/// in LI corresponds to exactly one value in ParentLI, and the live range 159/// of the value is contained within the live range of the ParentLI value. 160/// Values in ParentLI may map to any number of OpenLI values, including 0. 161class LiveIntervalMap { 162 LiveIntervals &LIS; 163 MachineDominatorTree &MDT; 164 165 // The parent interval is never changed. 166 const LiveInterval &ParentLI; 167 168 // The child interval's values are fully contained inside ParentLI values. 169 LiveInterval *LI; 170 171 typedef DenseMap<const VNInfo*, VNInfo*> ValueMap; 172 173 // Map ParentLI values to simple values in LI that are defined at the same 174 // SlotIndex, or NULL for ParentLI values that have complex LI defs. 175 // Note there is a difference between values mapping to NULL (complex), and 176 // values not present (unknown/unmapped). 177 ValueMap Values; 178 179 typedef std::pair<VNInfo*, MachineDomTreeNode*> LiveOutPair; 180 typedef DenseMap<MachineBasicBlock*,LiveOutPair> LiveOutMap; 181 182 // LiveOutCache - Map each basic block where LI is live out to the live-out 183 // value and its defining block. One of these conditions shall be true: 184 // 185 // 1. !LiveOutCache.count(MBB) 186 // 2. LiveOutCache[MBB].second.getNode() == MBB 187 // 3. forall P in preds(MBB): LiveOutCache[P] == LiveOutCache[MBB] 188 // 189 // This is only a cache, the values can be computed as: 190 // 191 // VNI = LI->getVNInfoAt(LIS.getMBBEndIdx(MBB)) 192 // Node = mbt_[LIS.getMBBFromIndex(VNI->def)] 193 // 194 // The cache is also used as a visiteed set by mapValue(). 195 LiveOutMap LiveOutCache; 196 197 // Dump the live-out cache to dbgs(). 198 void dumpCache(); 199 200public: 201 LiveIntervalMap(LiveIntervals &lis, 202 MachineDominatorTree &mdt, 203 const LiveInterval &parentli) 204 : LIS(lis), MDT(mdt), ParentLI(parentli), LI(0) {} 205 206 /// reset - clear all data structures and start a new live interval. 207 void reset(LiveInterval *); 208 209 /// getLI - return the current live interval. 210 LiveInterval *getLI() const { return LI; } 211 212 /// defValue - define a value in LI from the ParentLI value VNI and Idx. 213 /// Idx does not have to be ParentVNI->def, but it must be contained within 214 /// ParentVNI's live range in ParentLI. 215 /// Return the new LI value. 216 VNInfo *defValue(const VNInfo *ParentVNI, SlotIndex Idx); 217 218 /// mapValue - map ParentVNI to the corresponding LI value at Idx. It is 219 /// assumed that ParentVNI is live at Idx. 220 /// If ParentVNI has not been defined by defValue, it is assumed that 221 /// ParentVNI->def dominates Idx. 222 /// If ParentVNI has been defined by defValue one or more times, a value that 223 /// dominates Idx will be returned. This may require creating extra phi-def 224 /// values and adding live ranges to LI. 225 /// If simple is not NULL, *simple will indicate if ParentVNI is a simply 226 /// mapped value. 227 VNInfo *mapValue(const VNInfo *ParentVNI, SlotIndex Idx, bool *simple = 0); 228 229 // extendTo - Find the last LI value defined in MBB at or before Idx. The 230 // parentli is assumed to be live at Idx. Extend the live range to include 231 // Idx. Return the found VNInfo, or NULL. 232 VNInfo *extendTo(const MachineBasicBlock *MBB, SlotIndex Idx); 233 234 /// isMapped - Return true is ParentVNI is a known mapped value. It may be a 235 /// simple 1-1 mapping or a complex mapping to later defs. 236 bool isMapped(const VNInfo *ParentVNI) const { 237 return Values.count(ParentVNI); 238 } 239 240 /// isComplexMapped - Return true if ParentVNI has received new definitions 241 /// with defValue. 242 bool isComplexMapped(const VNInfo *ParentVNI) const; 243 244 /// markComplexMapped - Mark ParentVNI as complex mapped regardless of the 245 /// number of definitions. 246 void markComplexMapped(const VNInfo *ParentVNI) { Values[ParentVNI] = 0; } 247 248 // addSimpleRange - Add a simple range from ParentLI to LI. 249 // ParentVNI must be live in the [Start;End) interval. 250 void addSimpleRange(SlotIndex Start, SlotIndex End, const VNInfo *ParentVNI); 251 252 /// addRange - Add live ranges to LI where [Start;End) intersects ParentLI. 253 /// All needed values whose def is not inside [Start;End) must be defined 254 /// beforehand so mapValue will work. 255 void addRange(SlotIndex Start, SlotIndex End); 256}; 257 258 259/// SplitEditor - Edit machine code and LiveIntervals for live range 260/// splitting. 261/// 262/// - Create a SplitEditor from a SplitAnalysis. 263/// - Start a new live interval with openIntv. 264/// - Mark the places where the new interval is entered using enterIntv* 265/// - Mark the ranges where the new interval is used with useIntv* 266/// - Mark the places where the interval is exited with exitIntv*. 267/// - Finish the current interval with closeIntv and repeat from 2. 268/// - Rewrite instructions with finish(). 269/// 270class SplitEditor { 271 SplitAnalysis &SA; 272 LiveIntervals &LIS; 273 VirtRegMap &VRM; 274 MachineRegisterInfo &MRI; 275 MachineDominatorTree &MDT; 276 const TargetInstrInfo &TII; 277 const TargetRegisterInfo &TRI; 278 279 /// Edit - The current parent register and new intervals created. 280 LiveRangeEdit &Edit; 281 282 /// Index into Edit of the currently open interval. 283 /// The index 0 is used for the complement, so the first interval started by 284 /// openIntv will be 1. 285 unsigned OpenIdx; 286 287 typedef IntervalMap<SlotIndex, unsigned> RegAssignMap; 288 289 /// Allocator for the interval map. This will eventually be shared with 290 /// SlotIndexes and LiveIntervals. 291 RegAssignMap::Allocator Allocator; 292 293 /// RegAssign - Map of the assigned register indexes. 294 /// Edit.get(RegAssign.lookup(Idx)) is the register that should be live at 295 /// Idx. 296 RegAssignMap RegAssign; 297 298 /// LIMappers - One LiveIntervalMap or each interval in Edit. 299 SmallVector<LiveIntervalMap, 4> LIMappers; 300 301 /// defFromParent - Define Reg from ParentVNI at UseIdx using either 302 /// rematerialization or a COPY from parent. Return the new value. 303 VNInfo *defFromParent(unsigned RegIdx, 304 VNInfo *ParentVNI, 305 SlotIndex UseIdx, 306 MachineBasicBlock &MBB, 307 MachineBasicBlock::iterator I); 308 309 /// rewriteAssigned - Rewrite all uses of Edit.getReg() to assigned registers. 310 void rewriteAssigned(); 311 312 /// rewriteComponents - Rewrite all uses of Intv[0] according to the eq 313 /// classes in ConEQ. 314 /// This must be done when Intvs[0] is styill live at all uses, before calling 315 /// ConEq.Distribute(). 316 void rewriteComponents(const SmallVectorImpl<LiveInterval*> &Intvs, 317 const ConnectedVNInfoEqClasses &ConEq); 318 319public: 320 /// Create a new SplitEditor for editing the LiveInterval analyzed by SA. 321 /// Newly created intervals will be appended to newIntervals. 322 SplitEditor(SplitAnalysis &SA, LiveIntervals&, VirtRegMap&, 323 MachineDominatorTree&, LiveRangeEdit&); 324 325 /// getAnalysis - Get the corresponding analysis. 326 SplitAnalysis &getAnalysis() { return SA; } 327 328 /// Create a new virtual register and live interval. 329 void openIntv(); 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 /// closeIntv - Indicate that we are done editing the currently open 373 /// LiveInterval, and ranges can be trimmed. 374 void closeIntv(); 375 376 /// finish - after all the new live ranges have been created, compute the 377 /// remaining live range, and rewrite instructions to use the new registers. 378 void finish(); 379 380 /// dump - print the current interval maping to dbgs(). 381 void dump() const; 382 383 // ===--- High level methods ---=== 384 385 /// splitSingleBlocks - Split CurLI into a separate live interval inside each 386 /// basic block in Blocks. 387 void splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks); 388 389 /// splitInsideBlock - Split CurLI into multiple intervals inside MBB. 390 void splitInsideBlock(const MachineBasicBlock *); 391}; 392 393} 394