SplitKit.h revision fd1cced726469e83915f428877a521ba737d35f3
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/ArrayRef.h" 16#include "llvm/ADT/BitVector.h" 17#include "llvm/ADT/DenseMap.h" 18#include "llvm/ADT/IndexedMap.h" 19#include "llvm/ADT/IntervalMap.h" 20#include "llvm/ADT/SmallPtrSet.h" 21#include "llvm/CodeGen/SlotIndexes.h" 22 23namespace llvm { 24 25class ConnectedVNInfoEqClasses; 26class LiveInterval; 27class LiveIntervals; 28class LiveRangeEdit; 29class MachineInstr; 30class MachineLoopInfo; 31class MachineRegisterInfo; 32class TargetInstrInfo; 33class TargetRegisterInfo; 34class VirtRegMap; 35class VNInfo; 36class raw_ostream; 37 38/// At some point we should just include MachineDominators.h: 39class MachineDominatorTree; 40template <class NodeT> class DomTreeNodeBase; 41typedef DomTreeNodeBase<MachineBasicBlock> MachineDomTreeNode; 42 43 44/// SplitAnalysis - Analyze a LiveInterval, looking for live range splitting 45/// opportunities. 46class SplitAnalysis { 47public: 48 const MachineFunction &MF; 49 const VirtRegMap &VRM; 50 const LiveIntervals &LIS; 51 const MachineLoopInfo &Loops; 52 const TargetInstrInfo &TII; 53 54 // Sorted slot indexes of using instructions. 55 SmallVector<SlotIndex, 8> UseSlots; 56 57 /// Additional information about basic blocks where the current variable is 58 /// live. Such a block will look like one of these templates: 59 /// 60 /// 1. | o---x | Internal to block. Variable is only live in this block. 61 /// 2. |---x | Live-in, kill. 62 /// 3. | o---| Def, live-out. 63 /// 4. |---x o---| Live-in, kill, def, live-out. 64 /// 5. |---o---o---| Live-through with uses or defs. 65 /// 6. |-----------| Live-through without uses. Transparent. 66 /// 67 struct BlockInfo { 68 MachineBasicBlock *MBB; 69 SlotIndex FirstUse; ///< First instr using current reg. 70 SlotIndex LastUse; ///< Last instr using current reg. 71 SlotIndex Kill; ///< Interval end point inside block. 72 SlotIndex Def; ///< Interval start point inside block. 73 bool LiveThrough; ///< Live in whole block (Templ 5. or 6. above). 74 bool LiveIn; ///< Current reg is live in. 75 bool LiveOut; ///< Current reg is live out. 76 }; 77 78private: 79 // Current live interval. 80 const LiveInterval *CurLI; 81 82 /// LastSplitPoint - Last legal split point in each basic block in the current 83 /// function. The first entry is the first terminator, the second entry is the 84 /// last valid split point for a variable that is live in to a landing pad 85 /// successor. 86 SmallVector<std::pair<SlotIndex, SlotIndex>, 8> LastSplitPoint; 87 88 /// UseBlocks - Blocks where CurLI has uses. 89 SmallVector<BlockInfo, 8> UseBlocks; 90 91 /// ThroughBlocks - Block numbers where CurLI is live through without uses. 92 BitVector ThroughBlocks; 93 94 /// NumThroughBlocks - Number of live-through blocks. 95 unsigned NumThroughBlocks; 96 97 SlotIndex computeLastSplitPoint(unsigned Num); 98 99 // Sumarize statistics by counting instructions using CurLI. 100 void analyzeUses(); 101 102 /// calcLiveBlockInfo - Compute per-block information about CurLI. 103 bool calcLiveBlockInfo(); 104 105public: 106 SplitAnalysis(const VirtRegMap &vrm, const LiveIntervals &lis, 107 const MachineLoopInfo &mli); 108 109 /// analyze - set CurLI to the specified interval, and analyze how it may be 110 /// split. 111 void analyze(const LiveInterval *li); 112 113 /// clear - clear all data structures so SplitAnalysis is ready to analyze a 114 /// new interval. 115 void clear(); 116 117 /// getParent - Return the last analyzed interval. 118 const LiveInterval &getParent() const { return *CurLI; } 119 120 /// getLastSplitPoint - Return that base index of the last valid split point 121 /// in the basic block numbered Num. 122 SlotIndex getLastSplitPoint(unsigned Num) { 123 // Inline the common simple case. 124 if (LastSplitPoint[Num].first.isValid() && 125 !LastSplitPoint[Num].second.isValid()) 126 return LastSplitPoint[Num].first; 127 return computeLastSplitPoint(Num); 128 } 129 130 /// isOriginalEndpoint - Return true if the original live range was killed or 131 /// (re-)defined at Idx. Idx should be the 'def' slot for a normal kill/def, 132 /// and 'use' for an early-clobber def. 133 /// This can be used to recognize code inserted by earlier live range 134 /// splitting. 135 bool isOriginalEndpoint(SlotIndex Idx) const; 136 137 /// getUseBlocks - Return an array of BlockInfo objects for the basic blocks 138 /// where CurLI has uses. 139 ArrayRef<BlockInfo> getUseBlocks() { return UseBlocks; } 140 141 /// getNumThroughBlocks - Return the number of through blocks. 142 unsigned getNumThroughBlocks() const { return NumThroughBlocks; } 143 144 /// isThroughBlock - Return true if CurLI is live through MBB without uses. 145 bool isThroughBlock(unsigned MBB) const { return ThroughBlocks.test(MBB); } 146 147 /// getThroughBlocks - Return the set of through blocks. 148 const BitVector &getThroughBlocks() const { return ThroughBlocks; } 149 150 typedef SmallPtrSet<const MachineBasicBlock*, 16> BlockPtrSet; 151 152 /// getMultiUseBlocks - Add basic blocks to Blocks that may benefit from 153 /// having CurLI split to a new live interval. Return true if Blocks can be 154 /// passed to SplitEditor::splitSingleBlocks. 155 bool getMultiUseBlocks(BlockPtrSet &Blocks); 156}; 157 158 159/// SplitEditor - Edit machine code and LiveIntervals for live range 160/// splitting. 161/// 162/// - Create a SplitEditor from a SplitAnalysis. 163/// - Start a new live interval with openIntv. 164/// - Mark the places where the new interval is entered using enterIntv* 165/// - Mark the ranges where the new interval is used with useIntv* 166/// - Mark the places where the interval is exited with exitIntv*. 167/// - Finish the current interval with closeIntv and repeat from 2. 168/// - Rewrite instructions with finish(). 169/// 170class SplitEditor { 171 SplitAnalysis &SA; 172 LiveIntervals &LIS; 173 VirtRegMap &VRM; 174 MachineRegisterInfo &MRI; 175 MachineDominatorTree &MDT; 176 const TargetInstrInfo &TII; 177 const TargetRegisterInfo &TRI; 178 179 /// Edit - The current parent register and new intervals created. 180 LiveRangeEdit *Edit; 181 182 /// Index into Edit of the currently open interval. 183 /// The index 0 is used for the complement, so the first interval started by 184 /// openIntv will be 1. 185 unsigned OpenIdx; 186 187 typedef IntervalMap<SlotIndex, unsigned> RegAssignMap; 188 189 /// Allocator for the interval map. This will eventually be shared with 190 /// SlotIndexes and LiveIntervals. 191 RegAssignMap::Allocator Allocator; 192 193 /// RegAssign - Map of the assigned register indexes. 194 /// Edit.get(RegAssign.lookup(Idx)) is the register that should be live at 195 /// Idx. 196 RegAssignMap RegAssign; 197 198 typedef DenseMap<std::pair<unsigned, unsigned>, VNInfo*> ValueMap; 199 200 /// Values - keep track of the mapping from parent values to values in the new 201 /// intervals. Given a pair (RegIdx, ParentVNI->id), Values contains: 202 /// 203 /// 1. No entry - the value is not mapped to Edit.get(RegIdx). 204 /// 2. Null - the value is mapped to multiple values in Edit.get(RegIdx). 205 /// Each value is represented by a minimal live range at its def. 206 /// 3. A non-null VNInfo - the value is mapped to a single new value. 207 /// The new value has no live ranges anywhere. 208 ValueMap Values; 209 210 typedef std::pair<VNInfo*, MachineDomTreeNode*> LiveOutPair; 211 typedef IndexedMap<LiveOutPair, MBB2NumberFunctor> LiveOutMap; 212 213 // LiveOutCache - Map each basic block where a new register is live out to the 214 // live-out value and its defining block. 215 // One of these conditions shall be true: 216 // 217 // 1. !LiveOutCache.count(MBB) 218 // 2. LiveOutCache[MBB].second.getNode() == MBB 219 // 3. forall P in preds(MBB): LiveOutCache[P] == LiveOutCache[MBB] 220 // 221 // This is only a cache, the values can be computed as: 222 // 223 // VNI = Edit.get(RegIdx)->getVNInfoAt(LIS.getMBBEndIdx(MBB)) 224 // Node = mbt_[LIS.getMBBFromIndex(VNI->def)] 225 // 226 // The cache is also used as a visited set by extendRange(). It can be shared 227 // by all the new registers because at most one is live out of each block. 228 LiveOutMap LiveOutCache; 229 230 // LiveOutSeen - Indexed by MBB->getNumber(), a bit is set for each valid 231 // entry in LiveOutCache. 232 BitVector LiveOutSeen; 233 234 /// defValue - define a value in RegIdx from ParentVNI at Idx. 235 /// Idx does not have to be ParentVNI->def, but it must be contained within 236 /// ParentVNI's live range in ParentLI. The new value is added to the value 237 /// map. 238 /// Return the new LI value. 239 VNInfo *defValue(unsigned RegIdx, const VNInfo *ParentVNI, SlotIndex Idx); 240 241 /// markComplexMapped - Mark ParentVNI as complex mapped in RegIdx regardless 242 /// of the number of defs. 243 void markComplexMapped(unsigned RegIdx, const VNInfo *ParentVNI); 244 245 /// defFromParent - Define Reg from ParentVNI at UseIdx using either 246 /// rematerialization or a COPY from parent. Return the new value. 247 VNInfo *defFromParent(unsigned RegIdx, 248 VNInfo *ParentVNI, 249 SlotIndex UseIdx, 250 MachineBasicBlock &MBB, 251 MachineBasicBlock::iterator I); 252 253 /// extendRange - Extend the live range of Edit.get(RegIdx) so it reaches Idx. 254 /// Insert PHIDefs as needed to preserve SSA form. 255 void extendRange(unsigned RegIdx, SlotIndex Idx); 256 257 /// updateSSA - Insert PHIDefs as necessary and update LiveOutCache such that 258 /// Edit.get(RegIdx) is live-in to all the blocks in LiveIn. 259 /// Return the value that is eventually live-in to IdxMBB. 260 VNInfo *updateSSA(unsigned RegIdx, 261 SmallVectorImpl<MachineDomTreeNode*> &LiveIn, 262 SlotIndex Idx, 263 const MachineBasicBlock *IdxMBB); 264 265 /// transferSimpleValues - Transfer simply defined values to the new ranges. 266 /// Return true if any complex ranges were skipped. 267 bool transferSimpleValues(); 268 269 /// extendPHIKillRanges - Extend the ranges of all values killed by original 270 /// parent PHIDefs. 271 void extendPHIKillRanges(); 272 273 /// rewriteAssigned - Rewrite all uses of Edit.getReg() to assigned registers. 274 void rewriteAssigned(bool ExtendRanges); 275 276 /// deleteRematVictims - Delete defs that are dead after rematerializing. 277 void deleteRematVictims(); 278 279public: 280 /// Create a new SplitEditor for editing the LiveInterval analyzed by SA. 281 /// Newly created intervals will be appended to newIntervals. 282 SplitEditor(SplitAnalysis &SA, LiveIntervals&, VirtRegMap&, 283 MachineDominatorTree&); 284 285 /// reset - Prepare for a new split. 286 void reset(LiveRangeEdit&); 287 288 /// Create a new virtual register and live interval. 289 /// Return the interval index, starting from 1. Interval index 0 is the 290 /// implicit complement interval. 291 unsigned openIntv(); 292 293 /// currentIntv - Return the current interval index. 294 unsigned currentIntv() const { return OpenIdx; } 295 296 /// selectIntv - Select a previously opened interval index. 297 void selectIntv(unsigned Idx); 298 299 /// enterIntvBefore - Enter the open interval before the instruction at Idx. 300 /// If the parent interval is not live before Idx, a COPY is not inserted. 301 /// Return the beginning of the new live range. 302 SlotIndex enterIntvBefore(SlotIndex Idx); 303 304 /// enterIntvAtEnd - Enter the open interval at the end of MBB. 305 /// Use the open interval from he inserted copy to the MBB end. 306 /// Return the beginning of the new live range. 307 SlotIndex enterIntvAtEnd(MachineBasicBlock &MBB); 308 309 /// useIntv - indicate that all instructions in MBB should use OpenLI. 310 void useIntv(const MachineBasicBlock &MBB); 311 312 /// useIntv - indicate that all instructions in range should use OpenLI. 313 void useIntv(SlotIndex Start, SlotIndex End); 314 315 /// leaveIntvAfter - Leave the open interval after the instruction at Idx. 316 /// Return the end of the live range. 317 SlotIndex leaveIntvAfter(SlotIndex Idx); 318 319 /// leaveIntvBefore - Leave the open interval before the instruction at Idx. 320 /// Return the end of the live range. 321 SlotIndex leaveIntvBefore(SlotIndex Idx); 322 323 /// leaveIntvAtTop - Leave the interval at the top of MBB. 324 /// Add liveness from the MBB top to the copy. 325 /// Return the end of the live range. 326 SlotIndex leaveIntvAtTop(MachineBasicBlock &MBB); 327 328 /// overlapIntv - Indicate that all instructions in range should use the open 329 /// interval, but also let the complement interval be live. 330 /// 331 /// This doubles the register pressure, but is sometimes required to deal with 332 /// register uses after the last valid split point. 333 /// 334 /// The Start index should be a return value from a leaveIntv* call, and End 335 /// should be in the same basic block. The parent interval must have the same 336 /// value across the range. 337 /// 338 void overlapIntv(SlotIndex Start, SlotIndex End); 339 340 /// finish - after all the new live ranges have been created, compute the 341 /// remaining live range, and rewrite instructions to use the new registers. 342 void finish(); 343 344 /// dump - print the current interval maping to dbgs(). 345 void dump() const; 346 347 // ===--- High level methods ---=== 348 349 /// splitSingleBlock - Split CurLI into a separate live interval around the 350 /// uses in a single block. This is intended to be used as part of a larger 351 /// split, and doesn't call finish(). 352 void splitSingleBlock(const SplitAnalysis::BlockInfo &BI); 353 354 /// splitSingleBlocks - Split CurLI into a separate live interval inside each 355 /// basic block in Blocks. 356 void splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks); 357}; 358 359} 360