SplitKit.cpp revision b5fa9333431673aac2ced8dea80152349a85cf6f
1//===---------- SplitKit.cpp - Toolkit for splitting live ranges ----------===// 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#define DEBUG_TYPE "regalloc" 16#include "SplitKit.h" 17#include "LiveRangeEdit.h" 18#include "VirtRegMap.h" 19#include "llvm/CodeGen/CalcSpillWeights.h" 20#include "llvm/CodeGen/LiveIntervalAnalysis.h" 21#include "llvm/CodeGen/MachineDominators.h" 22#include "llvm/CodeGen/MachineInstrBuilder.h" 23#include "llvm/CodeGen/MachineLoopInfo.h" 24#include "llvm/CodeGen/MachineRegisterInfo.h" 25#include "llvm/Support/CommandLine.h" 26#include "llvm/Support/Debug.h" 27#include "llvm/Support/raw_ostream.h" 28#include "llvm/Target/TargetInstrInfo.h" 29#include "llvm/Target/TargetMachine.h" 30 31using namespace llvm; 32 33static cl::opt<bool> 34AllowSplit("spiller-splits-edges", 35 cl::desc("Allow critical edge splitting during spilling")); 36 37//===----------------------------------------------------------------------===// 38// Split Analysis 39//===----------------------------------------------------------------------===// 40 41SplitAnalysis::SplitAnalysis(const MachineFunction &mf, 42 const LiveIntervals &lis, 43 const MachineLoopInfo &mli) 44 : mf_(mf), 45 lis_(lis), 46 loops_(mli), 47 tii_(*mf.getTarget().getInstrInfo()), 48 curli_(0) {} 49 50void SplitAnalysis::clear() { 51 UseSlots.clear(); 52 usingInstrs_.clear(); 53 usingBlocks_.clear(); 54 usingLoops_.clear(); 55 curli_ = 0; 56} 57 58bool SplitAnalysis::canAnalyzeBranch(const MachineBasicBlock *MBB) { 59 MachineBasicBlock *T, *F; 60 SmallVector<MachineOperand, 4> Cond; 61 return !tii_.AnalyzeBranch(const_cast<MachineBasicBlock&>(*MBB), T, F, Cond); 62} 63 64/// analyzeUses - Count instructions, basic blocks, and loops using curli. 65void SplitAnalysis::analyzeUses() { 66 const MachineRegisterInfo &MRI = mf_.getRegInfo(); 67 for (MachineRegisterInfo::reg_iterator I = MRI.reg_begin(curli_->reg); 68 MachineInstr *MI = I.skipInstruction();) { 69 if (MI->isDebugValue() || !usingInstrs_.insert(MI)) 70 continue; 71 UseSlots.push_back(lis_.getInstructionIndex(MI).getDefIndex()); 72 MachineBasicBlock *MBB = MI->getParent(); 73 if (usingBlocks_[MBB]++) 74 continue; 75 for (MachineLoop *Loop = loops_.getLoopFor(MBB); Loop; 76 Loop = Loop->getParentLoop()) 77 usingLoops_[Loop]++; 78 } 79 array_pod_sort(UseSlots.begin(), UseSlots.end()); 80 DEBUG(dbgs() << " counted " 81 << usingInstrs_.size() << " instrs, " 82 << usingBlocks_.size() << " blocks, " 83 << usingLoops_.size() << " loops.\n"); 84} 85 86void SplitAnalysis::print(const BlockPtrSet &B, raw_ostream &OS) const { 87 for (BlockPtrSet::const_iterator I = B.begin(), E = B.end(); I != E; ++I) { 88 unsigned count = usingBlocks_.lookup(*I); 89 OS << " BB#" << (*I)->getNumber(); 90 if (count) 91 OS << '(' << count << ')'; 92 } 93} 94 95// Get three sets of basic blocks surrounding a loop: Blocks inside the loop, 96// predecessor blocks, and exit blocks. 97void SplitAnalysis::getLoopBlocks(const MachineLoop *Loop, LoopBlocks &Blocks) { 98 Blocks.clear(); 99 100 // Blocks in the loop. 101 Blocks.Loop.insert(Loop->block_begin(), Loop->block_end()); 102 103 // Predecessor blocks. 104 const MachineBasicBlock *Header = Loop->getHeader(); 105 for (MachineBasicBlock::const_pred_iterator I = Header->pred_begin(), 106 E = Header->pred_end(); I != E; ++I) 107 if (!Blocks.Loop.count(*I)) 108 Blocks.Preds.insert(*I); 109 110 // Exit blocks. 111 for (MachineLoop::block_iterator I = Loop->block_begin(), 112 E = Loop->block_end(); I != E; ++I) { 113 const MachineBasicBlock *MBB = *I; 114 for (MachineBasicBlock::const_succ_iterator SI = MBB->succ_begin(), 115 SE = MBB->succ_end(); SI != SE; ++SI) 116 if (!Blocks.Loop.count(*SI)) 117 Blocks.Exits.insert(*SI); 118 } 119} 120 121void SplitAnalysis::print(const LoopBlocks &B, raw_ostream &OS) const { 122 OS << "Loop:"; 123 print(B.Loop, OS); 124 OS << ", preds:"; 125 print(B.Preds, OS); 126 OS << ", exits:"; 127 print(B.Exits, OS); 128} 129 130/// analyzeLoopPeripheralUse - Return an enum describing how curli_ is used in 131/// and around the Loop. 132SplitAnalysis::LoopPeripheralUse SplitAnalysis:: 133analyzeLoopPeripheralUse(const SplitAnalysis::LoopBlocks &Blocks) { 134 LoopPeripheralUse use = ContainedInLoop; 135 for (BlockCountMap::iterator I = usingBlocks_.begin(), E = usingBlocks_.end(); 136 I != E; ++I) { 137 const MachineBasicBlock *MBB = I->first; 138 // Is this a peripheral block? 139 if (use < MultiPeripheral && 140 (Blocks.Preds.count(MBB) || Blocks.Exits.count(MBB))) { 141 if (I->second > 1) use = MultiPeripheral; 142 else use = SinglePeripheral; 143 continue; 144 } 145 // Is it a loop block? 146 if (Blocks.Loop.count(MBB)) 147 continue; 148 // It must be an unrelated block. 149 DEBUG(dbgs() << ", outside: BB#" << MBB->getNumber()); 150 return OutsideLoop; 151 } 152 return use; 153} 154 155/// getCriticalExits - It may be necessary to partially break critical edges 156/// leaving the loop if an exit block has predecessors from outside the loop 157/// periphery. 158void SplitAnalysis::getCriticalExits(const SplitAnalysis::LoopBlocks &Blocks, 159 BlockPtrSet &CriticalExits) { 160 CriticalExits.clear(); 161 162 // A critical exit block has curli live-in, and has a predecessor that is not 163 // in the loop nor a loop predecessor. For such an exit block, the edges 164 // carrying the new variable must be moved to a new pre-exit block. 165 for (BlockPtrSet::iterator I = Blocks.Exits.begin(), E = Blocks.Exits.end(); 166 I != E; ++I) { 167 const MachineBasicBlock *Exit = *I; 168 // A single-predecessor exit block is definitely not a critical edge. 169 if (Exit->pred_size() == 1) 170 continue; 171 // This exit may not have curli live in at all. No need to split. 172 if (!lis_.isLiveInToMBB(*curli_, Exit)) 173 continue; 174 // Does this exit block have a predecessor that is not a loop block or loop 175 // predecessor? 176 for (MachineBasicBlock::const_pred_iterator PI = Exit->pred_begin(), 177 PE = Exit->pred_end(); PI != PE; ++PI) { 178 const MachineBasicBlock *Pred = *PI; 179 if (Blocks.Loop.count(Pred) || Blocks.Preds.count(Pred)) 180 continue; 181 // This is a critical exit block, and we need to split the exit edge. 182 CriticalExits.insert(Exit); 183 break; 184 } 185 } 186} 187 188void SplitAnalysis::getCriticalPreds(const SplitAnalysis::LoopBlocks &Blocks, 189 BlockPtrSet &CriticalPreds) { 190 CriticalPreds.clear(); 191 192 // A critical predecessor block has curli live-out, and has a successor that 193 // has curli live-in and is not in the loop nor a loop exit block. For such a 194 // predecessor block, we must carry the value in both the 'inside' and 195 // 'outside' registers. 196 for (BlockPtrSet::iterator I = Blocks.Preds.begin(), E = Blocks.Preds.end(); 197 I != E; ++I) { 198 const MachineBasicBlock *Pred = *I; 199 // Definitely not a critical edge. 200 if (Pred->succ_size() == 1) 201 continue; 202 // This block may not have curli live out at all if there is a PHI. 203 if (!lis_.isLiveOutOfMBB(*curli_, Pred)) 204 continue; 205 // Does this block have a successor outside the loop? 206 for (MachineBasicBlock::const_pred_iterator SI = Pred->succ_begin(), 207 SE = Pred->succ_end(); SI != SE; ++SI) { 208 const MachineBasicBlock *Succ = *SI; 209 if (Blocks.Loop.count(Succ) || Blocks.Exits.count(Succ)) 210 continue; 211 if (!lis_.isLiveInToMBB(*curli_, Succ)) 212 continue; 213 // This is a critical predecessor block. 214 CriticalPreds.insert(Pred); 215 break; 216 } 217 } 218} 219 220/// canSplitCriticalExits - Return true if it is possible to insert new exit 221/// blocks before the blocks in CriticalExits. 222bool 223SplitAnalysis::canSplitCriticalExits(const SplitAnalysis::LoopBlocks &Blocks, 224 BlockPtrSet &CriticalExits) { 225 // If we don't allow critical edge splitting, require no critical exits. 226 if (!AllowSplit) 227 return CriticalExits.empty(); 228 229 for (BlockPtrSet::iterator I = CriticalExits.begin(), E = CriticalExits.end(); 230 I != E; ++I) { 231 const MachineBasicBlock *Succ = *I; 232 // We want to insert a new pre-exit MBB before Succ, and change all the 233 // in-loop blocks to branch to the pre-exit instead of Succ. 234 // Check that all the in-loop predecessors can be changed. 235 for (MachineBasicBlock::const_pred_iterator PI = Succ->pred_begin(), 236 PE = Succ->pred_end(); PI != PE; ++PI) { 237 const MachineBasicBlock *Pred = *PI; 238 // The external predecessors won't be altered. 239 if (!Blocks.Loop.count(Pred) && !Blocks.Preds.count(Pred)) 240 continue; 241 if (!canAnalyzeBranch(Pred)) 242 return false; 243 } 244 245 // If Succ's layout predecessor falls through, that too must be analyzable. 246 // We need to insert the pre-exit block in the gap. 247 MachineFunction::const_iterator MFI = Succ; 248 if (MFI == mf_.begin()) 249 continue; 250 if (!canAnalyzeBranch(--MFI)) 251 return false; 252 } 253 // No problems found. 254 return true; 255} 256 257void SplitAnalysis::analyze(const LiveInterval *li) { 258 clear(); 259 curli_ = li; 260 analyzeUses(); 261} 262 263void SplitAnalysis::getSplitLoops(LoopPtrSet &Loops) { 264 assert(curli_ && "Call analyze() before getSplitLoops"); 265 if (usingLoops_.empty()) 266 return; 267 268 LoopBlocks Blocks; 269 BlockPtrSet CriticalExits; 270 271 // We split around loops where curli is used outside the periphery. 272 for (LoopCountMap::const_iterator I = usingLoops_.begin(), 273 E = usingLoops_.end(); I != E; ++I) { 274 const MachineLoop *Loop = I->first; 275 getLoopBlocks(Loop, Blocks); 276 DEBUG({ dbgs() << " "; print(Blocks, dbgs()); }); 277 278 switch(analyzeLoopPeripheralUse(Blocks)) { 279 case OutsideLoop: 280 break; 281 case MultiPeripheral: 282 // FIXME: We could split a live range with multiple uses in a peripheral 283 // block and still make progress. However, it is possible that splitting 284 // another live range will insert copies into a peripheral block, and 285 // there is a small chance we can enter an infinite loop, inserting copies 286 // forever. 287 // For safety, stick to splitting live ranges with uses outside the 288 // periphery. 289 DEBUG(dbgs() << ": multiple peripheral uses"); 290 break; 291 case ContainedInLoop: 292 DEBUG(dbgs() << ": fully contained\n"); 293 continue; 294 case SinglePeripheral: 295 DEBUG(dbgs() << ": single peripheral use\n"); 296 continue; 297 } 298 // Will it be possible to split around this loop? 299 getCriticalExits(Blocks, CriticalExits); 300 DEBUG(dbgs() << ": " << CriticalExits.size() << " critical exits\n"); 301 if (!canSplitCriticalExits(Blocks, CriticalExits)) 302 continue; 303 // This is a possible split. 304 Loops.insert(Loop); 305 } 306 307 DEBUG(dbgs() << " getSplitLoops found " << Loops.size() 308 << " candidate loops.\n"); 309} 310 311const MachineLoop *SplitAnalysis::getBestSplitLoop() { 312 LoopPtrSet Loops; 313 getSplitLoops(Loops); 314 if (Loops.empty()) 315 return 0; 316 317 // Pick the earliest loop. 318 // FIXME: Are there other heuristics to consider? 319 const MachineLoop *Best = 0; 320 SlotIndex BestIdx; 321 for (LoopPtrSet::const_iterator I = Loops.begin(), E = Loops.end(); I != E; 322 ++I) { 323 SlotIndex Idx = lis_.getMBBStartIdx((*I)->getHeader()); 324 if (!Best || Idx < BestIdx) 325 Best = *I, BestIdx = Idx; 326 } 327 DEBUG(dbgs() << " getBestSplitLoop found " << *Best); 328 return Best; 329} 330 331/// isBypassLoop - Return true if curli is live through Loop and has no uses 332/// inside the loop. Bypass loops are candidates for splitting because it can 333/// prevent interference inside the loop. 334bool SplitAnalysis::isBypassLoop(const MachineLoop *Loop) { 335 // If curli is live into the loop header and there are no uses in the loop, it 336 // must be live in the entire loop and live on at least one exiting edge. 337 return !usingLoops_.count(Loop) && 338 lis_.isLiveInToMBB(*curli_, Loop->getHeader()); 339} 340 341/// getBypassLoops - Get all the maximal bypass loops. These are the bypass 342/// loops whose parent is not a bypass loop. 343void SplitAnalysis::getBypassLoops(LoopPtrSet &BypassLoops) { 344 SmallVector<MachineLoop*, 8> Todo(loops_.begin(), loops_.end()); 345 while (!Todo.empty()) { 346 MachineLoop *Loop = Todo.pop_back_val(); 347 if (!usingLoops_.count(Loop)) { 348 // This is either a bypass loop or completely irrelevant. 349 if (lis_.isLiveInToMBB(*curli_, Loop->getHeader())) 350 BypassLoops.insert(Loop); 351 // Either way, skip the child loops. 352 continue; 353 } 354 355 // The child loops may be bypass loops. 356 Todo.append(Loop->begin(), Loop->end()); 357 } 358} 359 360 361//===----------------------------------------------------------------------===// 362// LiveIntervalMap 363//===----------------------------------------------------------------------===// 364 365// Work around the fact that the std::pair constructors are broken for pointer 366// pairs in some implementations. makeVV(x, 0) works. 367static inline std::pair<const VNInfo*, VNInfo*> 368makeVV(const VNInfo *a, VNInfo *b) { 369 return std::make_pair(a, b); 370} 371 372void LiveIntervalMap::reset(LiveInterval *li) { 373 li_ = li; 374 valueMap_.clear(); 375 liveOutCache_.clear(); 376} 377 378bool LiveIntervalMap::isComplexMapped(const VNInfo *ParentVNI) const { 379 ValueMap::const_iterator i = valueMap_.find(ParentVNI); 380 return i != valueMap_.end() && i->second == 0; 381} 382 383// defValue - Introduce a li_ def for ParentVNI that could be later than 384// ParentVNI->def. 385VNInfo *LiveIntervalMap::defValue(const VNInfo *ParentVNI, SlotIndex Idx) { 386 assert(li_ && "call reset first"); 387 assert(ParentVNI && "Mapping NULL value"); 388 assert(Idx.isValid() && "Invalid SlotIndex"); 389 assert(parentli_.getVNInfoAt(Idx) == ParentVNI && "Bad ParentVNI"); 390 391 // Create a new value. 392 VNInfo *VNI = li_->getNextValue(Idx, 0, lis_.getVNInfoAllocator()); 393 394 // Preserve the PHIDef bit. 395 if (ParentVNI->isPHIDef() && Idx == ParentVNI->def) 396 VNI->setIsPHIDef(true); 397 398 // Use insert for lookup, so we can add missing values with a second lookup. 399 std::pair<ValueMap::iterator,bool> InsP = 400 valueMap_.insert(makeVV(ParentVNI, Idx == ParentVNI->def ? VNI : 0)); 401 402 // This is now a complex def. Mark with a NULL in valueMap. 403 if (!InsP.second) 404 InsP.first->second = 0; 405 406 return VNI; 407} 408 409 410// mapValue - Find the mapped value for ParentVNI at Idx. 411// Potentially create phi-def values. 412VNInfo *LiveIntervalMap::mapValue(const VNInfo *ParentVNI, SlotIndex Idx, 413 bool *simple) { 414 assert(li_ && "call reset first"); 415 assert(ParentVNI && "Mapping NULL value"); 416 assert(Idx.isValid() && "Invalid SlotIndex"); 417 assert(parentli_.getVNInfoAt(Idx) == ParentVNI && "Bad ParentVNI"); 418 419 // Use insert for lookup, so we can add missing values with a second lookup. 420 std::pair<ValueMap::iterator,bool> InsP = 421 valueMap_.insert(makeVV(ParentVNI, 0)); 422 423 // This was an unknown value. Create a simple mapping. 424 if (InsP.second) { 425 if (simple) *simple = true; 426 return InsP.first->second = li_->createValueCopy(ParentVNI, 427 lis_.getVNInfoAllocator()); 428 } 429 430 // This was a simple mapped value. 431 if (InsP.first->second) { 432 if (simple) *simple = true; 433 return InsP.first->second; 434 } 435 436 // This is a complex mapped value. There may be multiple defs, and we may need 437 // to create phi-defs. 438 if (simple) *simple = false; 439 MachineBasicBlock *IdxMBB = lis_.getMBBFromIndex(Idx); 440 assert(IdxMBB && "No MBB at Idx"); 441 442 // Is there a def in the same MBB we can extend? 443 if (VNInfo *VNI = extendTo(IdxMBB, Idx)) 444 return VNI; 445 446 // Now for the fun part. We know that ParentVNI potentially has multiple defs, 447 // and we may need to create even more phi-defs to preserve VNInfo SSA form. 448 // Perform a search for all predecessor blocks where we know the dominating 449 // VNInfo. Insert phi-def VNInfos along the path back to IdxMBB. 450 DEBUG(dbgs() << "\n Reaching defs for BB#" << IdxMBB->getNumber() 451 << " at " << Idx << " in " << *li_ << '\n'); 452 453 // Blocks where li_ should be live-in. 454 SmallVector<MachineDomTreeNode*, 16> LiveIn; 455 LiveIn.push_back(mdt_[IdxMBB]); 456 457 // Using liveOutCache_ as a visited set, perform a BFS for all reaching defs. 458 for (unsigned i = 0; i != LiveIn.size(); ++i) { 459 MachineBasicBlock *MBB = LiveIn[i]->getBlock(); 460 for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(), 461 PE = MBB->pred_end(); PI != PE; ++PI) { 462 MachineBasicBlock *Pred = *PI; 463 // Is this a known live-out block? 464 std::pair<LiveOutMap::iterator,bool> LOIP = 465 liveOutCache_.insert(std::make_pair(Pred, LiveOutPair())); 466 // Yes, we have been here before. 467 if (!LOIP.second) { 468 DEBUG(if (VNInfo *VNI = LOIP.first->second.first) 469 dbgs() << " known valno #" << VNI->id 470 << " at BB#" << Pred->getNumber() << '\n'); 471 continue; 472 } 473 474 // Does Pred provide a live-out value? 475 SlotIndex Last = lis_.getMBBEndIdx(Pred).getPrevSlot(); 476 if (VNInfo *VNI = extendTo(Pred, Last)) { 477 MachineBasicBlock *DefMBB = lis_.getMBBFromIndex(VNI->def); 478 DEBUG(dbgs() << " found valno #" << VNI->id 479 << " from BB#" << DefMBB->getNumber() 480 << " at BB#" << Pred->getNumber() << '\n'); 481 LiveOutPair &LOP = LOIP.first->second; 482 LOP.first = VNI; 483 LOP.second = mdt_[DefMBB]; 484 continue; 485 } 486 // No, we need a live-in value for Pred as well 487 if (Pred != IdxMBB) 488 LiveIn.push_back(mdt_[Pred]); 489 } 490 } 491 492 // We may need to add phi-def values to preserve the SSA form. 493 // This is essentially the same iterative algorithm that SSAUpdater uses, 494 // except we already have a dominator tree, so we don't have to recompute it. 495 VNInfo *IdxVNI = 0; 496 unsigned Changes; 497 do { 498 Changes = 0; 499 DEBUG(dbgs() << " Iterating over " << LiveIn.size() << " blocks.\n"); 500 // Propagate live-out values down the dominator tree, inserting phi-defs when 501 // necessary. Since LiveIn was created by a BFS, going backwards makes it more 502 // likely for us to visit immediate dominators before their children. 503 for (unsigned i = LiveIn.size(); i; --i) { 504 MachineDomTreeNode *Node = LiveIn[i-1]; 505 MachineBasicBlock *MBB = Node->getBlock(); 506 MachineDomTreeNode *IDom = Node->getIDom(); 507 LiveOutPair IDomValue; 508 // We need a live-in value to a block with no immediate dominator? 509 // This is probably an unreachable block that has survived somehow. 510 bool needPHI = !IDom; 511 512 // Get the IDom live-out value. 513 if (!needPHI) { 514 LiveOutMap::iterator I = liveOutCache_.find(IDom->getBlock()); 515 if (I != liveOutCache_.end()) 516 IDomValue = I->second; 517 else 518 // If IDom is outside our set of live-out blocks, there must be new 519 // defs, and we need a phi-def here. 520 needPHI = true; 521 } 522 523 // IDom dominates all of our predecessors, but it may not be the immediate 524 // dominator. Check if any of them have live-out values that are properly 525 // dominated by IDom. If so, we need a phi-def here. 526 if (!needPHI) { 527 for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(), 528 PE = MBB->pred_end(); PI != PE; ++PI) { 529 LiveOutPair Value = liveOutCache_[*PI]; 530 if (!Value.first || Value.first == IDomValue.first) 531 continue; 532 // This predecessor is carrying something other than IDomValue. 533 // It could be because IDomValue hasn't propagated yet, or it could be 534 // because MBB is in the dominance frontier of that value. 535 if (mdt_.dominates(IDom, Value.second)) { 536 needPHI = true; 537 break; 538 } 539 } 540 } 541 542 // Create a phi-def if required. 543 if (needPHI) { 544 ++Changes; 545 SlotIndex Start = lis_.getMBBStartIdx(MBB); 546 VNInfo *VNI = li_->getNextValue(Start, 0, lis_.getVNInfoAllocator()); 547 VNI->setIsPHIDef(true); 548 DEBUG(dbgs() << " - BB#" << MBB->getNumber() 549 << " phi-def #" << VNI->id << " at " << Start << '\n'); 550 // We no longer need li_ to be live-in. 551 LiveIn.erase(LiveIn.begin()+(i-1)); 552 // Blocks in LiveIn are either IdxMBB, or have a value live-through. 553 if (MBB == IdxMBB) 554 IdxVNI = VNI; 555 // Check if we need to update live-out info. 556 LiveOutMap::iterator I = liveOutCache_.find(MBB); 557 if (I == liveOutCache_.end() || I->second.second == Node) { 558 // We already have a live-out defined in MBB, so this must be IdxMBB. 559 assert(MBB == IdxMBB && "Adding phi-def to known live-out"); 560 li_->addRange(LiveRange(Start, Idx.getNextSlot(), VNI)); 561 } else { 562 // This phi-def is also live-out, so color the whole block. 563 li_->addRange(LiveRange(Start, lis_.getMBBEndIdx(MBB), VNI)); 564 I->second = LiveOutPair(VNI, Node); 565 } 566 } else if (IDomValue.first) { 567 // No phi-def here. Remember incoming value for IdxMBB. 568 if (MBB == IdxMBB) 569 IdxVNI = IDomValue.first; 570 // Propagate IDomValue if needed: 571 // MBB is live-out and doesn't define its own value. 572 LiveOutMap::iterator I = liveOutCache_.find(MBB); 573 if (I != liveOutCache_.end() && I->second.second != Node && 574 I->second.first != IDomValue.first) { 575 ++Changes; 576 I->second = IDomValue; 577 DEBUG(dbgs() << " - BB#" << MBB->getNumber() 578 << " idom valno #" << IDomValue.first->id 579 << " from BB#" << IDom->getBlock()->getNumber() << '\n'); 580 } 581 } 582 } 583 DEBUG(dbgs() << " - made " << Changes << " changes.\n"); 584 } while (Changes); 585 586 assert(IdxVNI && "Didn't find value for Idx"); 587 588#ifndef NDEBUG 589 // Check the liveOutCache_ invariants. 590 for (LiveOutMap::iterator I = liveOutCache_.begin(), E = liveOutCache_.end(); 591 I != E; ++I) { 592 assert(I->first && "Null MBB entry in cache"); 593 assert(I->second.first && "Null VNInfo in cache"); 594 assert(I->second.second && "Null DomTreeNode in cache"); 595 if (I->second.second->getBlock() == I->first) 596 continue; 597 for (MachineBasicBlock::pred_iterator PI = I->first->pred_begin(), 598 PE = I->first->pred_end(); PI != PE; ++PI) 599 assert(liveOutCache_.lookup(*PI) == I->second && "Bad invariant"); 600 } 601#endif 602 603 // Since we went through the trouble of a full BFS visiting all reaching defs, 604 // the values in LiveIn are now accurate. No more phi-defs are needed 605 // for these blocks, so we can color the live ranges. 606 // This makes the next mapValue call much faster. 607 for (unsigned i = 0, e = LiveIn.size(); i != e; ++i) { 608 MachineBasicBlock *MBB = LiveIn[i]->getBlock(); 609 SlotIndex Start = lis_.getMBBStartIdx(MBB); 610 if (MBB == IdxMBB) { 611 li_->addRange(LiveRange(Start, Idx.getNextSlot(), IdxVNI)); 612 continue; 613 } 614 // Anything in LiveIn other than IdxMBB is live-through. 615 VNInfo *VNI = liveOutCache_.lookup(MBB).first; 616 assert(VNI && "Missing block value"); 617 li_->addRange(LiveRange(Start, lis_.getMBBEndIdx(MBB), VNI)); 618 } 619 620 return IdxVNI; 621} 622 623// extendTo - Find the last li_ value defined in MBB at or before Idx. The 624// parentli_ is assumed to be live at Idx. Extend the live range to Idx. 625// Return the found VNInfo, or NULL. 626VNInfo *LiveIntervalMap::extendTo(const MachineBasicBlock *MBB, SlotIndex Idx) { 627 assert(li_ && "call reset first"); 628 LiveInterval::iterator I = std::upper_bound(li_->begin(), li_->end(), Idx); 629 if (I == li_->begin()) 630 return 0; 631 --I; 632 if (I->end <= lis_.getMBBStartIdx(MBB)) 633 return 0; 634 if (I->end <= Idx) 635 I->end = Idx.getNextSlot(); 636 return I->valno; 637} 638 639// addSimpleRange - Add a simple range from parentli_ to li_. 640// ParentVNI must be live in the [Start;End) interval. 641void LiveIntervalMap::addSimpleRange(SlotIndex Start, SlotIndex End, 642 const VNInfo *ParentVNI) { 643 assert(li_ && "call reset first"); 644 bool simple; 645 VNInfo *VNI = mapValue(ParentVNI, Start, &simple); 646 // A simple mapping is easy. 647 if (simple) { 648 li_->addRange(LiveRange(Start, End, VNI)); 649 return; 650 } 651 652 // ParentVNI is a complex value. We must map per MBB. 653 MachineFunction::iterator MBB = lis_.getMBBFromIndex(Start); 654 MachineFunction::iterator MBBE = lis_.getMBBFromIndex(End.getPrevSlot()); 655 656 if (MBB == MBBE) { 657 li_->addRange(LiveRange(Start, End, VNI)); 658 return; 659 } 660 661 // First block. 662 li_->addRange(LiveRange(Start, lis_.getMBBEndIdx(MBB), VNI)); 663 664 // Run sequence of full blocks. 665 for (++MBB; MBB != MBBE; ++MBB) { 666 Start = lis_.getMBBStartIdx(MBB); 667 li_->addRange(LiveRange(Start, lis_.getMBBEndIdx(MBB), 668 mapValue(ParentVNI, Start))); 669 } 670 671 // Final block. 672 Start = lis_.getMBBStartIdx(MBB); 673 if (Start != End) 674 li_->addRange(LiveRange(Start, End, mapValue(ParentVNI, Start))); 675} 676 677/// addRange - Add live ranges to li_ where [Start;End) intersects parentli_. 678/// All needed values whose def is not inside [Start;End) must be defined 679/// beforehand so mapValue will work. 680void LiveIntervalMap::addRange(SlotIndex Start, SlotIndex End) { 681 assert(li_ && "call reset first"); 682 LiveInterval::const_iterator B = parentli_.begin(), E = parentli_.end(); 683 LiveInterval::const_iterator I = std::lower_bound(B, E, Start); 684 685 // Check if --I begins before Start and overlaps. 686 if (I != B) { 687 --I; 688 if (I->end > Start) 689 addSimpleRange(Start, std::min(End, I->end), I->valno); 690 ++I; 691 } 692 693 // The remaining ranges begin after Start. 694 for (;I != E && I->start < End; ++I) 695 addSimpleRange(I->start, std::min(End, I->end), I->valno); 696} 697 698 699//===----------------------------------------------------------------------===// 700// Split Editor 701//===----------------------------------------------------------------------===// 702 703/// Create a new SplitEditor for editing the LiveInterval analyzed by SA. 704SplitEditor::SplitEditor(SplitAnalysis &sa, 705 LiveIntervals &lis, 706 VirtRegMap &vrm, 707 MachineDominatorTree &mdt, 708 LiveRangeEdit &edit) 709 : sa_(sa), lis_(lis), vrm_(vrm), 710 mri_(vrm.getMachineFunction().getRegInfo()), 711 tii_(*vrm.getMachineFunction().getTarget().getInstrInfo()), 712 tri_(*vrm.getMachineFunction().getTarget().getRegisterInfo()), 713 edit_(edit), 714 dupli_(lis_, mdt, edit.getParent()), 715 openli_(lis_, mdt, edit.getParent()) 716{ 717 // We don't need an AliasAnalysis since we will only be performing 718 // cheap-as-a-copy remats anyway. 719 edit_.anyRematerializable(lis_, tii_, 0); 720} 721 722bool SplitEditor::intervalsLiveAt(SlotIndex Idx) const { 723 for (LiveRangeEdit::iterator I = edit_.begin(), E = edit_.end(); I != E; ++I) 724 if (*I != dupli_.getLI() && (*I)->liveAt(Idx)) 725 return true; 726 return false; 727} 728 729VNInfo *SplitEditor::defFromParent(LiveIntervalMap &Reg, 730 VNInfo *ParentVNI, 731 SlotIndex UseIdx, 732 MachineBasicBlock &MBB, 733 MachineBasicBlock::iterator I) { 734 VNInfo *VNI = 0; 735 MachineInstr *CopyMI = 0; 736 SlotIndex Def; 737 738 // Attempt cheap-as-a-copy rematerialization. 739 LiveRangeEdit::Remat RM(ParentVNI); 740 if (edit_.canRematerializeAt(RM, UseIdx, true, lis_)) { 741 Def = edit_.rematerializeAt(MBB, I, Reg.getLI()->reg, RM, 742 lis_, tii_, tri_); 743 } else { 744 // Can't remat, just insert a copy from parent. 745 CopyMI = BuildMI(MBB, I, DebugLoc(), tii_.get(TargetOpcode::COPY), 746 Reg.getLI()->reg).addReg(edit_.getReg()); 747 Def = lis_.InsertMachineInstrInMaps(CopyMI).getDefIndex(); 748 } 749 750 // Define the value in Reg. 751 VNI = Reg.defValue(ParentVNI, Def); 752 VNI->setCopy(CopyMI); 753 754 // Add minimal liveness for the new value. 755 if (UseIdx < Def) 756 UseIdx = Def; 757 Reg.getLI()->addRange(LiveRange(Def, UseIdx.getNextSlot(), VNI)); 758 return VNI; 759} 760 761/// Create a new virtual register and live interval. 762void SplitEditor::openIntv() { 763 assert(!openli_.getLI() && "Previous LI not closed before openIntv"); 764 if (!dupli_.getLI()) 765 dupli_.reset(&edit_.create(mri_, lis_, vrm_)); 766 767 openli_.reset(&edit_.create(mri_, lis_, vrm_)); 768} 769 770/// enterIntvBefore - Enter openli before the instruction at Idx. If curli is 771/// not live before Idx, a COPY is not inserted. 772void SplitEditor::enterIntvBefore(SlotIndex Idx) { 773 assert(openli_.getLI() && "openIntv not called before enterIntvBefore"); 774 Idx = Idx.getUseIndex(); 775 DEBUG(dbgs() << " enterIntvBefore " << Idx); 776 VNInfo *ParentVNI = edit_.getParent().getVNInfoAt(Idx); 777 if (!ParentVNI) { 778 DEBUG(dbgs() << ": not live\n"); 779 return; 780 } 781 DEBUG(dbgs() << ": valno " << ParentVNI->id); 782 truncatedValues.insert(ParentVNI); 783 MachineInstr *MI = lis_.getInstructionFromIndex(Idx); 784 assert(MI && "enterIntvBefore called with invalid index"); 785 786 defFromParent(openli_, ParentVNI, Idx, *MI->getParent(), MI); 787 788 DEBUG(dbgs() << ": " << *openli_.getLI() << '\n'); 789} 790 791/// enterIntvAtEnd - Enter openli at the end of MBB. 792void SplitEditor::enterIntvAtEnd(MachineBasicBlock &MBB) { 793 assert(openli_.getLI() && "openIntv not called before enterIntvAtEnd"); 794 SlotIndex End = lis_.getMBBEndIdx(&MBB).getPrevSlot(); 795 DEBUG(dbgs() << " enterIntvAtEnd BB#" << MBB.getNumber() << ", " << End); 796 VNInfo *ParentVNI = edit_.getParent().getVNInfoAt(End); 797 if (!ParentVNI) { 798 DEBUG(dbgs() << ": not live\n"); 799 return; 800 } 801 DEBUG(dbgs() << ": valno " << ParentVNI->id); 802 truncatedValues.insert(ParentVNI); 803 defFromParent(openli_, ParentVNI, End, MBB, MBB.getFirstTerminator()); 804 DEBUG(dbgs() << ": " << *openli_.getLI() << '\n'); 805} 806 807/// useIntv - indicate that all instructions in MBB should use openli. 808void SplitEditor::useIntv(const MachineBasicBlock &MBB) { 809 useIntv(lis_.getMBBStartIdx(&MBB), lis_.getMBBEndIdx(&MBB)); 810} 811 812void SplitEditor::useIntv(SlotIndex Start, SlotIndex End) { 813 assert(openli_.getLI() && "openIntv not called before useIntv"); 814 openli_.addRange(Start, End); 815 DEBUG(dbgs() << " use [" << Start << ';' << End << "): " 816 << *openli_.getLI() << '\n'); 817} 818 819/// leaveIntvAfter - Leave openli after the instruction at Idx. 820void SplitEditor::leaveIntvAfter(SlotIndex Idx) { 821 assert(openli_.getLI() && "openIntv not called before leaveIntvAfter"); 822 DEBUG(dbgs() << " leaveIntvAfter " << Idx); 823 824 // The interval must be live beyond the instruction at Idx. 825 Idx = Idx.getBoundaryIndex(); 826 VNInfo *ParentVNI = edit_.getParent().getVNInfoAt(Idx); 827 if (!ParentVNI) { 828 DEBUG(dbgs() << ": not live\n"); 829 return; 830 } 831 DEBUG(dbgs() << ": valno " << ParentVNI->id); 832 833 MachineBasicBlock::iterator MII = lis_.getInstructionFromIndex(Idx); 834 VNInfo *VNI = defFromParent(dupli_, ParentVNI, Idx, 835 *MII->getParent(), llvm::next(MII)); 836 837 // Make sure that openli is properly extended from Idx to the new copy. 838 // FIXME: This shouldn't be necessary for remats. 839 openli_.addSimpleRange(Idx, VNI->def, ParentVNI); 840 841 DEBUG(dbgs() << ": " << *openli_.getLI() << '\n'); 842} 843 844/// leaveIntvAtTop - Leave the interval at the top of MBB. 845/// Currently, only one value can leave the interval. 846void SplitEditor::leaveIntvAtTop(MachineBasicBlock &MBB) { 847 assert(openli_.getLI() && "openIntv not called before leaveIntvAtTop"); 848 SlotIndex Start = lis_.getMBBStartIdx(&MBB); 849 DEBUG(dbgs() << " leaveIntvAtTop BB#" << MBB.getNumber() << ", " << Start); 850 851 VNInfo *ParentVNI = edit_.getParent().getVNInfoAt(Start); 852 if (!ParentVNI) { 853 DEBUG(dbgs() << ": not live\n"); 854 return; 855 } 856 857 VNInfo *VNI = defFromParent(dupli_, ParentVNI, Start, MBB, 858 MBB.SkipPHIsAndLabels(MBB.begin())); 859 860 // Finally we must make sure that openli is properly extended from Start to 861 // the new copy. 862 openli_.addSimpleRange(Start, VNI->def, ParentVNI); 863 DEBUG(dbgs() << ": " << *openli_.getLI() << '\n'); 864} 865 866/// closeIntv - Indicate that we are done editing the currently open 867/// LiveInterval, and ranges can be trimmed. 868void SplitEditor::closeIntv() { 869 assert(openli_.getLI() && "openIntv not called before closeIntv"); 870 871 DEBUG(dbgs() << " closeIntv cleaning up\n"); 872 DEBUG(dbgs() << " open " << *openli_.getLI() << '\n'); 873 openli_.reset(0); 874} 875 876/// rewrite - Rewrite all uses of reg to use the new registers. 877void SplitEditor::rewrite(unsigned reg) { 878 for (MachineRegisterInfo::reg_iterator RI = mri_.reg_begin(reg), 879 RE = mri_.reg_end(); RI != RE;) { 880 MachineOperand &MO = RI.getOperand(); 881 unsigned OpNum = RI.getOperandNo(); 882 MachineInstr *MI = MO.getParent(); 883 ++RI; 884 if (MI->isDebugValue()) { 885 DEBUG(dbgs() << "Zapping " << *MI); 886 // FIXME: We can do much better with debug values. 887 MO.setReg(0); 888 continue; 889 } 890 SlotIndex Idx = lis_.getInstructionIndex(MI); 891 Idx = MO.isUse() ? Idx.getUseIndex() : Idx.getDefIndex(); 892 LiveInterval *LI = 0; 893 for (LiveRangeEdit::iterator I = edit_.begin(), E = edit_.end(); I != E; 894 ++I) { 895 LiveInterval *testli = *I; 896 if (testli->liveAt(Idx)) { 897 LI = testli; 898 break; 899 } 900 } 901 DEBUG(dbgs() << " rewr BB#" << MI->getParent()->getNumber() << '\t'<< Idx); 902 assert(LI && "No register was live at use"); 903 MO.setReg(LI->reg); 904 if (MO.isUse() && !MI->isRegTiedToDefOperand(OpNum)) 905 MO.setIsKill(LI->killedAt(Idx.getDefIndex())); 906 DEBUG(dbgs() << '\t' << *MI); 907 } 908} 909 910void 911SplitEditor::addTruncSimpleRange(SlotIndex Start, SlotIndex End, VNInfo *VNI) { 912 // Build vector of iterator pairs from the intervals. 913 typedef std::pair<LiveInterval::const_iterator, 914 LiveInterval::const_iterator> IIPair; 915 SmallVector<IIPair, 8> Iters; 916 for (LiveRangeEdit::iterator LI = edit_.begin(), LE = edit_.end(); LI != LE; 917 ++LI) { 918 if (*LI == dupli_.getLI()) 919 continue; 920 LiveInterval::const_iterator I = (*LI)->find(Start); 921 LiveInterval::const_iterator E = (*LI)->end(); 922 if (I != E) 923 Iters.push_back(std::make_pair(I, E)); 924 } 925 926 SlotIndex sidx = Start; 927 // Break [Start;End) into segments that don't overlap any intervals. 928 for (;;) { 929 SlotIndex next = sidx, eidx = End; 930 // Find overlapping intervals. 931 for (unsigned i = 0; i != Iters.size() && sidx < eidx; ++i) { 932 LiveInterval::const_iterator I = Iters[i].first; 933 // Interval I is overlapping [sidx;eidx). Trim sidx. 934 if (I->start <= sidx) { 935 sidx = I->end; 936 // Move to the next run, remove iters when all are consumed. 937 I = ++Iters[i].first; 938 if (I == Iters[i].second) { 939 Iters.erase(Iters.begin() + i); 940 --i; 941 continue; 942 } 943 } 944 // Trim eidx too if needed. 945 if (I->start >= eidx) 946 continue; 947 eidx = I->start; 948 next = I->end; 949 } 950 // Now, [sidx;eidx) doesn't overlap anything in intervals_. 951 if (sidx < eidx) 952 dupli_.addSimpleRange(sidx, eidx, VNI); 953 // If the interval end was truncated, we can try again from next. 954 if (next <= sidx) 955 break; 956 sidx = next; 957 } 958} 959 960void SplitEditor::computeRemainder() { 961 // First we need to fill in the live ranges in dupli. 962 // If values were redefined, we need a full recoloring with SSA update. 963 // If values were truncated, we only need to truncate the ranges. 964 // If values were partially rematted, we should shrink to uses. 965 // If values were fully rematted, they should be omitted. 966 // FIXME: If a single value is redefined, just move the def and truncate. 967 LiveInterval &parent = edit_.getParent(); 968 969 // Values that are fully contained in the split intervals. 970 SmallPtrSet<const VNInfo*, 8> deadValues; 971 // Map all curli values that should have live defs in dupli. 972 for (LiveInterval::const_vni_iterator I = parent.vni_begin(), 973 E = parent.vni_end(); I != E; ++I) { 974 const VNInfo *VNI = *I; 975 // Don't transfer unused values to the new intervals. 976 if (VNI->isUnused()) 977 continue; 978 // Original def is contained in the split intervals. 979 if (intervalsLiveAt(VNI->def)) { 980 // Did this value escape? 981 if (dupli_.isMapped(VNI)) 982 truncatedValues.insert(VNI); 983 else 984 deadValues.insert(VNI); 985 continue; 986 } 987 // Add minimal live range at the definition. 988 VNInfo *DVNI = dupli_.defValue(VNI, VNI->def); 989 dupli_.getLI()->addRange(LiveRange(VNI->def, VNI->def.getNextSlot(), DVNI)); 990 } 991 992 // Add all ranges to dupli. 993 for (LiveInterval::const_iterator I = parent.begin(), E = parent.end(); 994 I != E; ++I) { 995 const LiveRange &LR = *I; 996 if (truncatedValues.count(LR.valno)) { 997 // recolor after removing intervals_. 998 addTruncSimpleRange(LR.start, LR.end, LR.valno); 999 } else if (!deadValues.count(LR.valno)) { 1000 // recolor without truncation. 1001 dupli_.addSimpleRange(LR.start, LR.end, LR.valno); 1002 } 1003 } 1004 1005 // Extend dupli_ to be live out of any critical loop predecessors. 1006 // This means we have multiple registers live out of those blocks. 1007 // The alternative would be to split the critical edges. 1008 if (criticalPreds_.empty()) 1009 return; 1010 for (SplitAnalysis::BlockPtrSet::iterator I = criticalPreds_.begin(), 1011 E = criticalPreds_.end(); I != E; ++I) 1012 dupli_.extendTo(*I, lis_.getMBBEndIdx(*I).getPrevSlot()); 1013 criticalPreds_.clear(); 1014} 1015 1016void SplitEditor::finish() { 1017 assert(!openli_.getLI() && "Previous LI not closed before rewrite"); 1018 assert(dupli_.getLI() && "No dupli for rewrite. Noop spilt?"); 1019 1020 // Complete dupli liveness. 1021 computeRemainder(); 1022 1023 // Get rid of unused values and set phi-kill flags. 1024 for (LiveRangeEdit::iterator I = edit_.begin(), E = edit_.end(); I != E; ++I) 1025 (*I)->RenumberValues(lis_); 1026 1027 // Rewrite instructions. 1028 rewrite(edit_.getReg()); 1029 1030 // Now check if any registers were separated into multiple components. 1031 ConnectedVNInfoEqClasses ConEQ(lis_); 1032 for (unsigned i = 0, e = edit_.size(); i != e; ++i) { 1033 // Don't use iterators, they are invalidated by create() below. 1034 LiveInterval *li = edit_.get(i); 1035 unsigned NumComp = ConEQ.Classify(li); 1036 if (NumComp <= 1) 1037 continue; 1038 DEBUG(dbgs() << " " << NumComp << " components: " << *li << '\n'); 1039 SmallVector<LiveInterval*, 8> dups; 1040 dups.push_back(li); 1041 for (unsigned i = 1; i != NumComp; ++i) 1042 dups.push_back(&edit_.create(mri_, lis_, vrm_)); 1043 ConEQ.Distribute(&dups[0]); 1044 // Rewrite uses to the new regs. 1045 rewrite(li->reg); 1046 } 1047 1048 // Calculate spill weight and allocation hints for new intervals. 1049 VirtRegAuxInfo vrai(vrm_.getMachineFunction(), lis_, sa_.loops_); 1050 for (LiveRangeEdit::iterator I = edit_.begin(), E = edit_.end(); I != E; ++I){ 1051 LiveInterval &li = **I; 1052 vrai.CalculateRegClass(li.reg); 1053 vrai.CalculateWeightAndHint(li); 1054 DEBUG(dbgs() << " new interval " << mri_.getRegClass(li.reg)->getName() 1055 << ":" << li << '\n'); 1056 } 1057} 1058 1059 1060//===----------------------------------------------------------------------===// 1061// Loop Splitting 1062//===----------------------------------------------------------------------===// 1063 1064void SplitEditor::splitAroundLoop(const MachineLoop *Loop) { 1065 SplitAnalysis::LoopBlocks Blocks; 1066 sa_.getLoopBlocks(Loop, Blocks); 1067 1068 DEBUG({ 1069 dbgs() << " splitAround"; sa_.print(Blocks, dbgs()); dbgs() << '\n'; 1070 }); 1071 1072 // Break critical edges as needed. 1073 SplitAnalysis::BlockPtrSet CriticalExits; 1074 sa_.getCriticalExits(Blocks, CriticalExits); 1075 assert(CriticalExits.empty() && "Cannot break critical exits yet"); 1076 1077 // Get critical predecessors so computeRemainder can deal with them. 1078 sa_.getCriticalPreds(Blocks, criticalPreds_); 1079 1080 // Create new live interval for the loop. 1081 openIntv(); 1082 1083 // Insert copies in the predecessors if live-in to the header. 1084 if (lis_.isLiveInToMBB(edit_.getParent(), Loop->getHeader())) { 1085 for (SplitAnalysis::BlockPtrSet::iterator I = Blocks.Preds.begin(), 1086 E = Blocks.Preds.end(); I != E; ++I) { 1087 MachineBasicBlock &MBB = const_cast<MachineBasicBlock&>(**I); 1088 enterIntvAtEnd(MBB); 1089 } 1090 } 1091 1092 // Switch all loop blocks. 1093 for (SplitAnalysis::BlockPtrSet::iterator I = Blocks.Loop.begin(), 1094 E = Blocks.Loop.end(); I != E; ++I) 1095 useIntv(**I); 1096 1097 // Insert back copies in the exit blocks. 1098 for (SplitAnalysis::BlockPtrSet::iterator I = Blocks.Exits.begin(), 1099 E = Blocks.Exits.end(); I != E; ++I) { 1100 MachineBasicBlock &MBB = const_cast<MachineBasicBlock&>(**I); 1101 leaveIntvAtTop(MBB); 1102 } 1103 1104 // Done. 1105 closeIntv(); 1106 finish(); 1107} 1108 1109 1110//===----------------------------------------------------------------------===// 1111// Single Block Splitting 1112//===----------------------------------------------------------------------===// 1113 1114/// getMultiUseBlocks - if curli has more than one use in a basic block, it 1115/// may be an advantage to split curli for the duration of the block. 1116bool SplitAnalysis::getMultiUseBlocks(BlockPtrSet &Blocks) { 1117 // If curli is local to one block, there is no point to splitting it. 1118 if (usingBlocks_.size() <= 1) 1119 return false; 1120 // Add blocks with multiple uses. 1121 for (BlockCountMap::iterator I = usingBlocks_.begin(), E = usingBlocks_.end(); 1122 I != E; ++I) 1123 switch (I->second) { 1124 case 0: 1125 case 1: 1126 continue; 1127 case 2: { 1128 // When there are only two uses and curli is both live in and live out, 1129 // we don't really win anything by isolating the block since we would be 1130 // inserting two copies. 1131 // The remaing register would still have two uses in the block. (Unless it 1132 // separates into disconnected components). 1133 if (lis_.isLiveInToMBB(*curli_, I->first) && 1134 lis_.isLiveOutOfMBB(*curli_, I->first)) 1135 continue; 1136 } // Fall through. 1137 default: 1138 Blocks.insert(I->first); 1139 } 1140 return !Blocks.empty(); 1141} 1142 1143/// splitSingleBlocks - Split curli into a separate live interval inside each 1144/// basic block in Blocks. 1145void SplitEditor::splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks) { 1146 DEBUG(dbgs() << " splitSingleBlocks for " << Blocks.size() << " blocks.\n"); 1147 // Determine the first and last instruction using curli in each block. 1148 typedef std::pair<SlotIndex,SlotIndex> IndexPair; 1149 typedef DenseMap<const MachineBasicBlock*,IndexPair> IndexPairMap; 1150 IndexPairMap MBBRange; 1151 for (SplitAnalysis::InstrPtrSet::const_iterator I = sa_.usingInstrs_.begin(), 1152 E = sa_.usingInstrs_.end(); I != E; ++I) { 1153 const MachineBasicBlock *MBB = (*I)->getParent(); 1154 if (!Blocks.count(MBB)) 1155 continue; 1156 SlotIndex Idx = lis_.getInstructionIndex(*I); 1157 DEBUG(dbgs() << " BB#" << MBB->getNumber() << '\t' << Idx << '\t' << **I); 1158 IndexPair &IP = MBBRange[MBB]; 1159 if (!IP.first.isValid() || Idx < IP.first) 1160 IP.first = Idx; 1161 if (!IP.second.isValid() || Idx > IP.second) 1162 IP.second = Idx; 1163 } 1164 1165 // Create a new interval for each block. 1166 for (SplitAnalysis::BlockPtrSet::const_iterator I = Blocks.begin(), 1167 E = Blocks.end(); I != E; ++I) { 1168 IndexPair &IP = MBBRange[*I]; 1169 DEBUG(dbgs() << " splitting for BB#" << (*I)->getNumber() << ": [" 1170 << IP.first << ';' << IP.second << ")\n"); 1171 assert(IP.first.isValid() && IP.second.isValid()); 1172 1173 openIntv(); 1174 enterIntvBefore(IP.first); 1175 useIntv(IP.first.getBaseIndex(), IP.second.getBoundaryIndex()); 1176 leaveIntvAfter(IP.second); 1177 closeIntv(); 1178 } 1179 finish(); 1180} 1181 1182 1183//===----------------------------------------------------------------------===// 1184// Sub Block Splitting 1185//===----------------------------------------------------------------------===// 1186 1187/// getBlockForInsideSplit - If curli is contained inside a single basic block, 1188/// and it wou pay to subdivide the interval inside that block, return it. 1189/// Otherwise return NULL. The returned block can be passed to 1190/// SplitEditor::splitInsideBlock. 1191const MachineBasicBlock *SplitAnalysis::getBlockForInsideSplit() { 1192 // The interval must be exclusive to one block. 1193 if (usingBlocks_.size() != 1) 1194 return 0; 1195 // Don't to this for less than 4 instructions. We want to be sure that 1196 // splitting actually reduces the instruction count per interval. 1197 if (usingInstrs_.size() < 4) 1198 return 0; 1199 return usingBlocks_.begin()->first; 1200} 1201 1202/// splitInsideBlock - Split curli into multiple intervals inside MBB. 1203void SplitEditor::splitInsideBlock(const MachineBasicBlock *MBB) { 1204 SmallVector<SlotIndex, 32> Uses; 1205 Uses.reserve(sa_.usingInstrs_.size()); 1206 for (SplitAnalysis::InstrPtrSet::const_iterator I = sa_.usingInstrs_.begin(), 1207 E = sa_.usingInstrs_.end(); I != E; ++I) 1208 if ((*I)->getParent() == MBB) 1209 Uses.push_back(lis_.getInstructionIndex(*I)); 1210 DEBUG(dbgs() << " splitInsideBlock BB#" << MBB->getNumber() << " for " 1211 << Uses.size() << " instructions.\n"); 1212 assert(Uses.size() >= 3 && "Need at least 3 instructions"); 1213 array_pod_sort(Uses.begin(), Uses.end()); 1214 1215 // Simple algorithm: Find the largest gap between uses as determined by slot 1216 // indices. Create new intervals for instructions before the gap and after the 1217 // gap. 1218 unsigned bestPos = 0; 1219 int bestGap = 0; 1220 DEBUG(dbgs() << " dist (" << Uses[0]); 1221 for (unsigned i = 1, e = Uses.size(); i != e; ++i) { 1222 int g = Uses[i-1].distance(Uses[i]); 1223 DEBUG(dbgs() << ") -" << g << "- (" << Uses[i]); 1224 if (g > bestGap) 1225 bestPos = i, bestGap = g; 1226 } 1227 DEBUG(dbgs() << "), best: -" << bestGap << "-\n"); 1228 1229 // bestPos points to the first use after the best gap. 1230 assert(bestPos > 0 && "Invalid gap"); 1231 1232 // FIXME: Don't create intervals for low densities. 1233 1234 // First interval before the gap. Don't create single-instr intervals. 1235 if (bestPos > 1) { 1236 openIntv(); 1237 enterIntvBefore(Uses.front()); 1238 useIntv(Uses.front().getBaseIndex(), Uses[bestPos-1].getBoundaryIndex()); 1239 leaveIntvAfter(Uses[bestPos-1]); 1240 closeIntv(); 1241 } 1242 1243 // Second interval after the gap. 1244 if (bestPos < Uses.size()-1) { 1245 openIntv(); 1246 enterIntvBefore(Uses[bestPos]); 1247 useIntv(Uses[bestPos].getBaseIndex(), Uses.back().getBoundaryIndex()); 1248 leaveIntvAfter(Uses.back()); 1249 closeIntv(); 1250 } 1251 1252 finish(); 1253} 1254