SplitKit.h revision db529a8a5d071610f3a8b467693bc40b073e68ef
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 SmallVector<unsigned, 8> ThroughBlocks; 93 94 SlotIndex computeLastSplitPoint(unsigned Num); 95 96 // Sumarize statistics by counting instructions using CurLI. 97 void analyzeUses(); 98 99 /// calcLiveBlockInfo - Compute per-block information about CurLI. 100 bool calcLiveBlockInfo(); 101 102public: 103 SplitAnalysis(const VirtRegMap &vrm, const LiveIntervals &lis, 104 const MachineLoopInfo &mli); 105 106 /// analyze - set CurLI to the specified interval, and analyze how it may be 107 /// split. 108 void analyze(const LiveInterval *li); 109 110 /// clear - clear all data structures so SplitAnalysis is ready to analyze a 111 /// new interval. 112 void clear(); 113 114 /// getParent - Return the last analyzed interval. 115 const LiveInterval &getParent() const { return *CurLI; } 116 117 /// getLastSplitPoint - Return that base index of the last valid split point 118 /// in the basic block numbered Num. 119 SlotIndex getLastSplitPoint(unsigned Num) { 120 // Inline the common simple case. 121 if (LastSplitPoint[Num].first.isValid() && 122 !LastSplitPoint[Num].second.isValid()) 123 return LastSplitPoint[Num].first; 124 return computeLastSplitPoint(Num); 125 } 126 127 /// isOriginalEndpoint - Return true if the original live range was killed or 128 /// (re-)defined at Idx. Idx should be the 'def' slot for a normal kill/def, 129 /// and 'use' for an early-clobber def. 130 /// This can be used to recognize code inserted by earlier live range 131 /// splitting. 132 bool isOriginalEndpoint(SlotIndex Idx) const; 133 134 /// getUseBlocks - Return an array of BlockInfo objects for the basic blocks 135 /// where CurLI has uses. 136 ArrayRef<BlockInfo> getUseBlocks() { return UseBlocks; } 137 138 /// getThroughBlocks - Return an array of block numbers where CurLI is live 139 /// through without uses. 140 ArrayRef<unsigned> getThroughBlocks() { return ThroughBlocks; } 141 142 typedef SmallPtrSet<const MachineBasicBlock*, 16> BlockPtrSet; 143 144 /// getMultiUseBlocks - Add basic blocks to Blocks that may benefit from 145 /// having CurLI split to a new live interval. Return true if Blocks can be 146 /// passed to SplitEditor::splitSingleBlocks. 147 bool getMultiUseBlocks(BlockPtrSet &Blocks); 148}; 149 150 151/// SplitEditor - Edit machine code and LiveIntervals for live range 152/// splitting. 153/// 154/// - Create a SplitEditor from a SplitAnalysis. 155/// - Start a new live interval with openIntv. 156/// - Mark the places where the new interval is entered using enterIntv* 157/// - Mark the ranges where the new interval is used with useIntv* 158/// - Mark the places where the interval is exited with exitIntv*. 159/// - Finish the current interval with closeIntv and repeat from 2. 160/// - Rewrite instructions with finish(). 161/// 162class SplitEditor { 163 SplitAnalysis &SA; 164 LiveIntervals &LIS; 165 VirtRegMap &VRM; 166 MachineRegisterInfo &MRI; 167 MachineDominatorTree &MDT; 168 const TargetInstrInfo &TII; 169 const TargetRegisterInfo &TRI; 170 171 /// Edit - The current parent register and new intervals created. 172 LiveRangeEdit *Edit; 173 174 /// Index into Edit of the currently open interval. 175 /// The index 0 is used for the complement, so the first interval started by 176 /// openIntv will be 1. 177 unsigned OpenIdx; 178 179 typedef IntervalMap<SlotIndex, unsigned> RegAssignMap; 180 181 /// Allocator for the interval map. This will eventually be shared with 182 /// SlotIndexes and LiveIntervals. 183 RegAssignMap::Allocator Allocator; 184 185 /// RegAssign - Map of the assigned register indexes. 186 /// Edit.get(RegAssign.lookup(Idx)) is the register that should be live at 187 /// Idx. 188 RegAssignMap RegAssign; 189 190 typedef DenseMap<std::pair<unsigned, unsigned>, VNInfo*> ValueMap; 191 192 /// Values - keep track of the mapping from parent values to values in the new 193 /// intervals. Given a pair (RegIdx, ParentVNI->id), Values contains: 194 /// 195 /// 1. No entry - the value is not mapped to Edit.get(RegIdx). 196 /// 2. Null - the value is mapped to multiple values in Edit.get(RegIdx). 197 /// Each value is represented by a minimal live range at its def. 198 /// 3. A non-null VNInfo - the value is mapped to a single new value. 199 /// The new value has no live ranges anywhere. 200 ValueMap Values; 201 202 typedef std::pair<VNInfo*, MachineDomTreeNode*> LiveOutPair; 203 typedef IndexedMap<LiveOutPair, MBB2NumberFunctor> LiveOutMap; 204 205 // LiveOutCache - Map each basic block where a new register is live out to the 206 // live-out value and its defining block. 207 // One of these conditions shall be true: 208 // 209 // 1. !LiveOutCache.count(MBB) 210 // 2. LiveOutCache[MBB].second.getNode() == MBB 211 // 3. forall P in preds(MBB): LiveOutCache[P] == LiveOutCache[MBB] 212 // 213 // This is only a cache, the values can be computed as: 214 // 215 // VNI = Edit.get(RegIdx)->getVNInfoAt(LIS.getMBBEndIdx(MBB)) 216 // Node = mbt_[LIS.getMBBFromIndex(VNI->def)] 217 // 218 // The cache is also used as a visited set by extendRange(). It can be shared 219 // by all the new registers because at most one is live out of each block. 220 LiveOutMap LiveOutCache; 221 222 // LiveOutSeen - Indexed by MBB->getNumber(), a bit is set for each valid 223 // entry in LiveOutCache. 224 BitVector LiveOutSeen; 225 226 /// defValue - define a value in RegIdx from ParentVNI at Idx. 227 /// Idx does not have to be ParentVNI->def, but it must be contained within 228 /// ParentVNI's live range in ParentLI. The new value is added to the value 229 /// map. 230 /// Return the new LI value. 231 VNInfo *defValue(unsigned RegIdx, const VNInfo *ParentVNI, SlotIndex Idx); 232 233 /// markComplexMapped - Mark ParentVNI as complex mapped in RegIdx regardless 234 /// of the number of defs. 235 void markComplexMapped(unsigned RegIdx, const VNInfo *ParentVNI); 236 237 /// defFromParent - Define Reg from ParentVNI at UseIdx using either 238 /// rematerialization or a COPY from parent. Return the new value. 239 VNInfo *defFromParent(unsigned RegIdx, 240 VNInfo *ParentVNI, 241 SlotIndex UseIdx, 242 MachineBasicBlock &MBB, 243 MachineBasicBlock::iterator I); 244 245 /// extendRange - Extend the live range of Edit.get(RegIdx) so it reaches Idx. 246 /// Insert PHIDefs as needed to preserve SSA form. 247 void extendRange(unsigned RegIdx, SlotIndex Idx); 248 249 /// updateSSA - Insert PHIDefs as necessary and update LiveOutCache such that 250 /// Edit.get(RegIdx) is live-in to all the blocks in LiveIn. 251 /// Return the value that is eventually live-in to IdxMBB. 252 VNInfo *updateSSA(unsigned RegIdx, 253 SmallVectorImpl<MachineDomTreeNode*> &LiveIn, 254 SlotIndex Idx, 255 const MachineBasicBlock *IdxMBB); 256 257 /// transferSimpleValues - Transfer simply defined values to the new ranges. 258 /// Return true if any complex ranges were skipped. 259 bool transferSimpleValues(); 260 261 /// extendPHIKillRanges - Extend the ranges of all values killed by original 262 /// parent PHIDefs. 263 void extendPHIKillRanges(); 264 265 /// rewriteAssigned - Rewrite all uses of Edit.getReg() to assigned registers. 266 void rewriteAssigned(bool ExtendRanges); 267 268 /// deleteRematVictims - Delete defs that are dead after rematerializing. 269 void deleteRematVictims(); 270 271public: 272 /// Create a new SplitEditor for editing the LiveInterval analyzed by SA. 273 /// Newly created intervals will be appended to newIntervals. 274 SplitEditor(SplitAnalysis &SA, LiveIntervals&, VirtRegMap&, 275 MachineDominatorTree&); 276 277 /// reset - Prepare for a new split. 278 void reset(LiveRangeEdit&); 279 280 /// Create a new virtual register and live interval. 281 void openIntv(); 282 283 /// enterIntvBefore - Enter the open interval before the instruction at Idx. 284 /// If the parent interval is not live before Idx, a COPY is not inserted. 285 /// Return the beginning of the new live range. 286 SlotIndex enterIntvBefore(SlotIndex Idx); 287 288 /// enterIntvAtEnd - Enter the open interval at the end of MBB. 289 /// Use the open interval from he inserted copy to the MBB end. 290 /// Return the beginning of the new live range. 291 SlotIndex enterIntvAtEnd(MachineBasicBlock &MBB); 292 293 /// useIntv - indicate that all instructions in MBB should use OpenLI. 294 void useIntv(const MachineBasicBlock &MBB); 295 296 /// useIntv - indicate that all instructions in range should use OpenLI. 297 void useIntv(SlotIndex Start, SlotIndex End); 298 299 /// leaveIntvAfter - Leave the open interval after the instruction at Idx. 300 /// Return the end of the live range. 301 SlotIndex leaveIntvAfter(SlotIndex Idx); 302 303 /// leaveIntvBefore - Leave the open interval before the instruction at Idx. 304 /// Return the end of the live range. 305 SlotIndex leaveIntvBefore(SlotIndex Idx); 306 307 /// leaveIntvAtTop - Leave the interval at the top of MBB. 308 /// Add liveness from the MBB top to the copy. 309 /// Return the end of the live range. 310 SlotIndex leaveIntvAtTop(MachineBasicBlock &MBB); 311 312 /// overlapIntv - Indicate that all instructions in range should use the open 313 /// interval, but also let the complement interval be live. 314 /// 315 /// This doubles the register pressure, but is sometimes required to deal with 316 /// register uses after the last valid split point. 317 /// 318 /// The Start index should be a return value from a leaveIntv* call, and End 319 /// should be in the same basic block. The parent interval must have the same 320 /// value across the range. 321 /// 322 void overlapIntv(SlotIndex Start, SlotIndex End); 323 324 /// closeIntv - Indicate that we are done editing the currently open 325 /// LiveInterval, and ranges can be trimmed. 326 void closeIntv(); 327 328 /// finish - after all the new live ranges have been created, compute the 329 /// remaining live range, and rewrite instructions to use the new registers. 330 void finish(); 331 332 /// dump - print the current interval maping to dbgs(). 333 void dump() const; 334 335 // ===--- High level methods ---=== 336 337 /// splitSingleBlocks - Split CurLI into a separate live interval inside each 338 /// basic block in Blocks. 339 void splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks); 340}; 341 342} 343