SplitKit.h revision 13ba2dab631636e525a44bb259aaea56a860d1c7
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/BitVector.h" 16#include "llvm/ADT/DenseMap.h" 17#include "llvm/ADT/IndexedMap.h" 18#include "llvm/ADT/IntervalMap.h" 19#include "llvm/ADT/SmallPtrSet.h" 20#include "llvm/CodeGen/SlotIndexes.h" 21 22namespace llvm { 23 24class ConnectedVNInfoEqClasses; 25class LiveInterval; 26class LiveIntervals; 27class LiveRangeEdit; 28class MachineInstr; 29class MachineLoopInfo; 30class MachineRegisterInfo; 31class TargetInstrInfo; 32class TargetRegisterInfo; 33class VirtRegMap; 34class VNInfo; 35class raw_ostream; 36 37/// At some point we should just include MachineDominators.h: 38class MachineDominatorTree; 39template <class NodeT> class DomTreeNodeBase; 40typedef DomTreeNodeBase<MachineBasicBlock> MachineDomTreeNode; 41 42 43/// SplitAnalysis - Analyze a LiveInterval, looking for live range splitting 44/// opportunities. 45class SplitAnalysis { 46public: 47 const MachineFunction &MF; 48 const VirtRegMap &VRM; 49 const LiveIntervals &LIS; 50 const MachineLoopInfo &Loops; 51 const TargetInstrInfo &TII; 52 53 // Instructions using the the current register. 54 typedef SmallPtrSet<const MachineInstr*, 16> InstrPtrSet; 55 InstrPtrSet UsingInstrs; 56 57 // Sorted slot indexes of using instructions. 58 SmallVector<SlotIndex, 8> UseSlots; 59 60 // The number of instructions using CurLI in each basic block. 61 typedef DenseMap<const MachineBasicBlock*, unsigned> BlockCountMap; 62 BlockCountMap UsingBlocks; 63 64 /// Additional information about basic blocks where the current variable is 65 /// live. Such a block will look like one of these templates: 66 /// 67 /// 1. | o---x | Internal to block. Variable is only live in this block. 68 /// 2. |---x | Live-in, kill. 69 /// 3. | o---| Def, live-out. 70 /// 4. |---x o---| Live-in, kill, def, live-out. 71 /// 5. |---o---o---| Live-through with uses or defs. 72 /// 6. |-----------| Live-through without uses. Transparent. 73 /// 74 struct BlockInfo { 75 MachineBasicBlock *MBB; 76 SlotIndex Start; ///< Beginining of block. 77 SlotIndex Stop; ///< End of block. 78 SlotIndex FirstUse; ///< First instr using current reg. 79 SlotIndex LastUse; ///< Last instr using current reg. 80 SlotIndex Kill; ///< Interval end point inside block. 81 SlotIndex Def; ///< Interval start point inside block. 82 /// Last possible point for splitting live ranges. 83 SlotIndex LastSplitPoint; 84 bool Uses; ///< Current reg has uses or defs in block. 85 bool LiveThrough; ///< Live in whole block (Templ 5. or 6. above). 86 bool LiveIn; ///< Current reg is live in. 87 bool LiveOut; ///< Current reg is live out. 88 89 // Per-interference pattern scratch data. 90 bool OverlapEntry; ///< Interference overlaps entering interval. 91 bool OverlapExit; ///< Interference overlaps exiting interval. 92 }; 93 94 /// Basic blocks where var is live. This array is parallel to 95 /// SpillConstraints. 96 SmallVector<BlockInfo, 8> LiveBlocks; 97 98private: 99 // Current live interval. 100 const LiveInterval *CurLI; 101 102 // Sumarize statistics by counting instructions using CurLI. 103 void analyzeUses(); 104 105 /// calcLiveBlockInfo - Compute per-block information about CurLI. 106 void calcLiveBlockInfo(); 107 108 /// canAnalyzeBranch - Return true if MBB ends in a branch that can be 109 /// analyzed. 110 bool canAnalyzeBranch(const MachineBasicBlock *MBB); 111 112public: 113 SplitAnalysis(const VirtRegMap &vrm, const LiveIntervals &lis, 114 const MachineLoopInfo &mli); 115 116 /// analyze - set CurLI to the specified interval, and analyze how it may be 117 /// split. 118 void analyze(const LiveInterval *li); 119 120 /// clear - clear all data structures so SplitAnalysis is ready to analyze a 121 /// new interval. 122 void clear(); 123 124 /// getParent - Return the last analyzed interval. 125 const LiveInterval &getParent() const { return *CurLI; } 126 127 /// hasUses - Return true if MBB has any uses of CurLI. 128 bool hasUses(const MachineBasicBlock *MBB) const { 129 return UsingBlocks.lookup(MBB); 130 } 131 132 /// isOriginalEndpoint - Return true if the original live range was killed or 133 /// (re-)defined at Idx. Idx should be the 'def' slot for a normal kill/def, 134 /// and 'use' for an early-clobber def. 135 /// This can be used to recognize code inserted by earlier live range 136 /// splitting. 137 bool isOriginalEndpoint(SlotIndex Idx) const; 138 139 typedef SmallPtrSet<const MachineBasicBlock*, 16> BlockPtrSet; 140 141 // Print a set of blocks with use counts. 142 void print(const BlockPtrSet&, raw_ostream&) const; 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 /// rewriteComponents - Rewrite all uses of Intv[0] according to the eq 269 /// classes in ConEQ. 270 /// This must be done when Intvs[0] is styill live at all uses, before calling 271 /// ConEq.Distribute(). 272 void rewriteComponents(const SmallVectorImpl<LiveInterval*> &Intvs, 273 const ConnectedVNInfoEqClasses &ConEq); 274 275public: 276 /// Create a new SplitEditor for editing the LiveInterval analyzed by SA. 277 /// Newly created intervals will be appended to newIntervals. 278 SplitEditor(SplitAnalysis &SA, LiveIntervals&, VirtRegMap&, 279 MachineDominatorTree&); 280 281 /// reset - Prepare for a new split. 282 void reset(LiveRangeEdit&); 283 284 /// Create a new virtual register and live interval. 285 void openIntv(); 286 287 /// enterIntvBefore - Enter the open interval before the instruction at Idx. 288 /// If the parent interval is not live before Idx, a COPY is not inserted. 289 /// Return the beginning of the new live range. 290 SlotIndex enterIntvBefore(SlotIndex Idx); 291 292 /// enterIntvAtEnd - Enter the open interval at the end of MBB. 293 /// Use the open interval from he inserted copy to the MBB end. 294 /// Return the beginning of the new live range. 295 SlotIndex enterIntvAtEnd(MachineBasicBlock &MBB); 296 297 /// useIntv - indicate that all instructions in MBB should use OpenLI. 298 void useIntv(const MachineBasicBlock &MBB); 299 300 /// useIntv - indicate that all instructions in range should use OpenLI. 301 void useIntv(SlotIndex Start, SlotIndex End); 302 303 /// leaveIntvAfter - Leave the open interval after the instruction at Idx. 304 /// Return the end of the live range. 305 SlotIndex leaveIntvAfter(SlotIndex Idx); 306 307 /// leaveIntvBefore - Leave the open interval before the instruction at Idx. 308 /// Return the end of the live range. 309 SlotIndex leaveIntvBefore(SlotIndex Idx); 310 311 /// leaveIntvAtTop - Leave the interval at the top of MBB. 312 /// Add liveness from the MBB top to the copy. 313 /// Return the end of the live range. 314 SlotIndex leaveIntvAtTop(MachineBasicBlock &MBB); 315 316 /// overlapIntv - Indicate that all instructions in range should use the open 317 /// interval, but also let the complement interval be live. 318 /// 319 /// This doubles the register pressure, but is sometimes required to deal with 320 /// register uses after the last valid split point. 321 /// 322 /// The Start index should be a return value from a leaveIntv* call, and End 323 /// should be in the same basic block. The parent interval must have the same 324 /// value across the range. 325 /// 326 void overlapIntv(SlotIndex Start, SlotIndex End); 327 328 /// closeIntv - Indicate that we are done editing the currently open 329 /// LiveInterval, and ranges can be trimmed. 330 void closeIntv(); 331 332 /// finish - after all the new live ranges have been created, compute the 333 /// remaining live range, and rewrite instructions to use the new registers. 334 void finish(); 335 336 /// dump - print the current interval maping to dbgs(). 337 void dump() const; 338 339 // ===--- High level methods ---=== 340 341 /// splitSingleBlocks - Split CurLI into a separate live interval inside each 342 /// basic block in Blocks. 343 void splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks); 344}; 345 346} 347