SplitKit.cpp revision c64379da075a59bd5178c62c970c8d2b84457ab2
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/GraphWriter.h" 28#include "llvm/Support/raw_ostream.h" 29#include "llvm/Target/TargetInstrInfo.h" 30#include "llvm/Target/TargetMachine.h" 31 32using namespace llvm; 33 34static cl::opt<bool> 35AllowSplit("spiller-splits-edges", 36 cl::desc("Allow critical edge splitting during spilling")); 37 38//===----------------------------------------------------------------------===// 39// Edge Bundles 40//===----------------------------------------------------------------------===// 41 42/// compute - Compute the edge bundles for MF. Bundles depend only on the CFG. 43void EdgeBundles::compute(const MachineFunction *mf) { 44 MF = mf; 45 EC.clear(); 46 EC.grow(2 * MF->size()); 47 48 for (MachineFunction::const_iterator I = MF->begin(), E = MF->end(); I != E; 49 ++I) { 50 const MachineBasicBlock &MBB = *I; 51 unsigned OutE = 2 * MBB.getNumber() + 1; 52 // Join the outgoing bundle with the ingoing bundles of all successors. 53 for (MachineBasicBlock::const_succ_iterator SI = MBB.succ_begin(), 54 SE = MBB.succ_end(); SI != SE; ++SI) 55 EC.join(OutE, 2 * (*SI)->getNumber()); 56 } 57 EC.compress(); 58} 59 60/// view - Visualize the annotated bipartite CFG with Graphviz. 61void EdgeBundles::view() const { 62 ViewGraph(*this, "EdgeBundles"); 63} 64 65/// Specialize WriteGraph, the standard implementation won't work. 66raw_ostream &llvm::WriteGraph(raw_ostream &O, const EdgeBundles &G, 67 bool ShortNames, 68 const std::string &Title) { 69 const MachineFunction *MF = G.getMachineFunction(); 70 71 O << "digraph {\n"; 72 for (MachineFunction::const_iterator I = MF->begin(), E = MF->end(); 73 I != E; ++I) { 74 unsigned BB = I->getNumber(); 75 O << "\t\"BB#" << BB << "\" [ shape=box ]\n" 76 << '\t' << G.getBundle(BB, false) << " -> \"BB#" << BB << "\"\n" 77 << "\t\"BB#" << BB << "\" -> " << G.getBundle(BB, true) << '\n'; 78 for (MachineBasicBlock::const_succ_iterator SI = I->succ_begin(), 79 SE = I->succ_end(); SI != SE; ++SI) 80 O << "\t\"BB#" << BB << "\" -> \"BB#" << (*SI)->getNumber() 81 << "\" [ color=lightgray ]\n"; 82 } 83 O << "}\n"; 84 return O; 85} 86 87 88//===----------------------------------------------------------------------===// 89// Split Analysis 90//===----------------------------------------------------------------------===// 91 92SplitAnalysis::SplitAnalysis(const MachineFunction &mf, 93 const LiveIntervals &lis, 94 const MachineLoopInfo &mli) 95 : mf_(mf), 96 lis_(lis), 97 loops_(mli), 98 tii_(*mf.getTarget().getInstrInfo()), 99 curli_(0) {} 100 101void SplitAnalysis::clear() { 102 usingInstrs_.clear(); 103 usingBlocks_.clear(); 104 usingLoops_.clear(); 105 curli_ = 0; 106} 107 108bool SplitAnalysis::canAnalyzeBranch(const MachineBasicBlock *MBB) { 109 MachineBasicBlock *T, *F; 110 SmallVector<MachineOperand, 4> Cond; 111 return !tii_.AnalyzeBranch(const_cast<MachineBasicBlock&>(*MBB), T, F, Cond); 112} 113 114/// analyzeUses - Count instructions, basic blocks, and loops using curli. 115void SplitAnalysis::analyzeUses() { 116 const MachineRegisterInfo &MRI = mf_.getRegInfo(); 117 for (MachineRegisterInfo::reg_iterator I = MRI.reg_begin(curli_->reg); 118 MachineInstr *MI = I.skipInstruction();) { 119 if (MI->isDebugValue() || !usingInstrs_.insert(MI)) 120 continue; 121 MachineBasicBlock *MBB = MI->getParent(); 122 if (usingBlocks_[MBB]++) 123 continue; 124 for (MachineLoop *Loop = loops_.getLoopFor(MBB); Loop; 125 Loop = Loop->getParentLoop()) 126 usingLoops_[Loop]++; 127 } 128 DEBUG(dbgs() << " counted " 129 << usingInstrs_.size() << " instrs, " 130 << usingBlocks_.size() << " blocks, " 131 << usingLoops_.size() << " loops.\n"); 132} 133 134void SplitAnalysis::print(const BlockPtrSet &B, raw_ostream &OS) const { 135 for (BlockPtrSet::const_iterator I = B.begin(), E = B.end(); I != E; ++I) { 136 unsigned count = usingBlocks_.lookup(*I); 137 OS << " BB#" << (*I)->getNumber(); 138 if (count) 139 OS << '(' << count << ')'; 140 } 141} 142 143// Get three sets of basic blocks surrounding a loop: Blocks inside the loop, 144// predecessor blocks, and exit blocks. 145void SplitAnalysis::getLoopBlocks(const MachineLoop *Loop, LoopBlocks &Blocks) { 146 Blocks.clear(); 147 148 // Blocks in the loop. 149 Blocks.Loop.insert(Loop->block_begin(), Loop->block_end()); 150 151 // Predecessor blocks. 152 const MachineBasicBlock *Header = Loop->getHeader(); 153 for (MachineBasicBlock::const_pred_iterator I = Header->pred_begin(), 154 E = Header->pred_end(); I != E; ++I) 155 if (!Blocks.Loop.count(*I)) 156 Blocks.Preds.insert(*I); 157 158 // Exit blocks. 159 for (MachineLoop::block_iterator I = Loop->block_begin(), 160 E = Loop->block_end(); I != E; ++I) { 161 const MachineBasicBlock *MBB = *I; 162 for (MachineBasicBlock::const_succ_iterator SI = MBB->succ_begin(), 163 SE = MBB->succ_end(); SI != SE; ++SI) 164 if (!Blocks.Loop.count(*SI)) 165 Blocks.Exits.insert(*SI); 166 } 167} 168 169void SplitAnalysis::print(const LoopBlocks &B, raw_ostream &OS) const { 170 OS << "Loop:"; 171 print(B.Loop, OS); 172 OS << ", preds:"; 173 print(B.Preds, OS); 174 OS << ", exits:"; 175 print(B.Exits, OS); 176} 177 178/// analyzeLoopPeripheralUse - Return an enum describing how curli_ is used in 179/// and around the Loop. 180SplitAnalysis::LoopPeripheralUse SplitAnalysis:: 181analyzeLoopPeripheralUse(const SplitAnalysis::LoopBlocks &Blocks) { 182 LoopPeripheralUse use = ContainedInLoop; 183 for (BlockCountMap::iterator I = usingBlocks_.begin(), E = usingBlocks_.end(); 184 I != E; ++I) { 185 const MachineBasicBlock *MBB = I->first; 186 // Is this a peripheral block? 187 if (use < MultiPeripheral && 188 (Blocks.Preds.count(MBB) || Blocks.Exits.count(MBB))) { 189 if (I->second > 1) use = MultiPeripheral; 190 else use = SinglePeripheral; 191 continue; 192 } 193 // Is it a loop block? 194 if (Blocks.Loop.count(MBB)) 195 continue; 196 // It must be an unrelated block. 197 DEBUG(dbgs() << ", outside: BB#" << MBB->getNumber()); 198 return OutsideLoop; 199 } 200 return use; 201} 202 203/// getCriticalExits - It may be necessary to partially break critical edges 204/// leaving the loop if an exit block has predecessors from outside the loop 205/// periphery. 206void SplitAnalysis::getCriticalExits(const SplitAnalysis::LoopBlocks &Blocks, 207 BlockPtrSet &CriticalExits) { 208 CriticalExits.clear(); 209 210 // A critical exit block has curli live-in, and has a predecessor that is not 211 // in the loop nor a loop predecessor. For such an exit block, the edges 212 // carrying the new variable must be moved to a new pre-exit block. 213 for (BlockPtrSet::iterator I = Blocks.Exits.begin(), E = Blocks.Exits.end(); 214 I != E; ++I) { 215 const MachineBasicBlock *Exit = *I; 216 // A single-predecessor exit block is definitely not a critical edge. 217 if (Exit->pred_size() == 1) 218 continue; 219 // This exit may not have curli live in at all. No need to split. 220 if (!lis_.isLiveInToMBB(*curli_, Exit)) 221 continue; 222 // Does this exit block have a predecessor that is not a loop block or loop 223 // predecessor? 224 for (MachineBasicBlock::const_pred_iterator PI = Exit->pred_begin(), 225 PE = Exit->pred_end(); PI != PE; ++PI) { 226 const MachineBasicBlock *Pred = *PI; 227 if (Blocks.Loop.count(Pred) || Blocks.Preds.count(Pred)) 228 continue; 229 // This is a critical exit block, and we need to split the exit edge. 230 CriticalExits.insert(Exit); 231 break; 232 } 233 } 234} 235 236void SplitAnalysis::getCriticalPreds(const SplitAnalysis::LoopBlocks &Blocks, 237 BlockPtrSet &CriticalPreds) { 238 CriticalPreds.clear(); 239 240 // A critical predecessor block has curli live-out, and has a successor that 241 // has curli live-in and is not in the loop nor a loop exit block. For such a 242 // predecessor block, we must carry the value in both the 'inside' and 243 // 'outside' registers. 244 for (BlockPtrSet::iterator I = Blocks.Preds.begin(), E = Blocks.Preds.end(); 245 I != E; ++I) { 246 const MachineBasicBlock *Pred = *I; 247 // Definitely not a critical edge. 248 if (Pred->succ_size() == 1) 249 continue; 250 // This block may not have curli live out at all if there is a PHI. 251 if (!lis_.isLiveOutOfMBB(*curli_, Pred)) 252 continue; 253 // Does this block have a successor outside the loop? 254 for (MachineBasicBlock::const_pred_iterator SI = Pred->succ_begin(), 255 SE = Pred->succ_end(); SI != SE; ++SI) { 256 const MachineBasicBlock *Succ = *SI; 257 if (Blocks.Loop.count(Succ) || Blocks.Exits.count(Succ)) 258 continue; 259 if (!lis_.isLiveInToMBB(*curli_, Succ)) 260 continue; 261 // This is a critical predecessor block. 262 CriticalPreds.insert(Pred); 263 break; 264 } 265 } 266} 267 268/// canSplitCriticalExits - Return true if it is possible to insert new exit 269/// blocks before the blocks in CriticalExits. 270bool 271SplitAnalysis::canSplitCriticalExits(const SplitAnalysis::LoopBlocks &Blocks, 272 BlockPtrSet &CriticalExits) { 273 // If we don't allow critical edge splitting, require no critical exits. 274 if (!AllowSplit) 275 return CriticalExits.empty(); 276 277 for (BlockPtrSet::iterator I = CriticalExits.begin(), E = CriticalExits.end(); 278 I != E; ++I) { 279 const MachineBasicBlock *Succ = *I; 280 // We want to insert a new pre-exit MBB before Succ, and change all the 281 // in-loop blocks to branch to the pre-exit instead of Succ. 282 // Check that all the in-loop predecessors can be changed. 283 for (MachineBasicBlock::const_pred_iterator PI = Succ->pred_begin(), 284 PE = Succ->pred_end(); PI != PE; ++PI) { 285 const MachineBasicBlock *Pred = *PI; 286 // The external predecessors won't be altered. 287 if (!Blocks.Loop.count(Pred) && !Blocks.Preds.count(Pred)) 288 continue; 289 if (!canAnalyzeBranch(Pred)) 290 return false; 291 } 292 293 // If Succ's layout predecessor falls through, that too must be analyzable. 294 // We need to insert the pre-exit block in the gap. 295 MachineFunction::const_iterator MFI = Succ; 296 if (MFI == mf_.begin()) 297 continue; 298 if (!canAnalyzeBranch(--MFI)) 299 return false; 300 } 301 // No problems found. 302 return true; 303} 304 305void SplitAnalysis::analyze(const LiveInterval *li) { 306 clear(); 307 curli_ = li; 308 analyzeUses(); 309} 310 311void SplitAnalysis::getSplitLoops(LoopPtrSet &Loops) { 312 assert(curli_ && "Call analyze() before getSplitLoops"); 313 if (usingLoops_.empty()) 314 return; 315 316 LoopBlocks Blocks; 317 BlockPtrSet CriticalExits; 318 319 // We split around loops where curli is used outside the periphery. 320 for (LoopCountMap::const_iterator I = usingLoops_.begin(), 321 E = usingLoops_.end(); I != E; ++I) { 322 const MachineLoop *Loop = I->first; 323 getLoopBlocks(Loop, Blocks); 324 DEBUG({ dbgs() << " "; print(Blocks, dbgs()); }); 325 326 switch(analyzeLoopPeripheralUse(Blocks)) { 327 case OutsideLoop: 328 break; 329 case MultiPeripheral: 330 // FIXME: We could split a live range with multiple uses in a peripheral 331 // block and still make progress. However, it is possible that splitting 332 // another live range will insert copies into a peripheral block, and 333 // there is a small chance we can enter an infinite loop, inserting copies 334 // forever. 335 // For safety, stick to splitting live ranges with uses outside the 336 // periphery. 337 DEBUG(dbgs() << ": multiple peripheral uses"); 338 break; 339 case ContainedInLoop: 340 DEBUG(dbgs() << ": fully contained\n"); 341 continue; 342 case SinglePeripheral: 343 DEBUG(dbgs() << ": single peripheral use\n"); 344 continue; 345 } 346 // Will it be possible to split around this loop? 347 getCriticalExits(Blocks, CriticalExits); 348 DEBUG(dbgs() << ": " << CriticalExits.size() << " critical exits\n"); 349 if (!canSplitCriticalExits(Blocks, CriticalExits)) 350 continue; 351 // This is a possible split. 352 Loops.insert(Loop); 353 } 354 355 DEBUG(dbgs() << " getSplitLoops found " << Loops.size() 356 << " candidate loops.\n"); 357} 358 359const MachineLoop *SplitAnalysis::getBestSplitLoop() { 360 LoopPtrSet Loops; 361 getSplitLoops(Loops); 362 if (Loops.empty()) 363 return 0; 364 365 // Pick the earliest loop. 366 // FIXME: Are there other heuristics to consider? 367 const MachineLoop *Best = 0; 368 SlotIndex BestIdx; 369 for (LoopPtrSet::const_iterator I = Loops.begin(), E = Loops.end(); I != E; 370 ++I) { 371 SlotIndex Idx = lis_.getMBBStartIdx((*I)->getHeader()); 372 if (!Best || Idx < BestIdx) 373 Best = *I, BestIdx = Idx; 374 } 375 DEBUG(dbgs() << " getBestSplitLoop found " << *Best); 376 return Best; 377} 378 379/// isBypassLoop - Return true if curli is live through Loop and has no uses 380/// inside the loop. Bypass loops are candidates for splitting because it can 381/// prevent interference inside the loop. 382bool SplitAnalysis::isBypassLoop(const MachineLoop *Loop) { 383 // If curli is live into the loop header and there are no uses in the loop, it 384 // must be live in the entire loop and live on at least one exiting edge. 385 return !usingLoops_.count(Loop) && 386 lis_.isLiveInToMBB(*curli_, Loop->getHeader()); 387} 388 389/// getBypassLoops - Get all the maximal bypass loops. These are the bypass 390/// loops whose parent is not a bypass loop. 391void SplitAnalysis::getBypassLoops(LoopPtrSet &BypassLoops) { 392 SmallVector<MachineLoop*, 8> Todo(loops_.begin(), loops_.end()); 393 while (!Todo.empty()) { 394 MachineLoop *Loop = Todo.pop_back_val(); 395 if (!usingLoops_.count(Loop)) { 396 // This is either a bypass loop or completely irrelevant. 397 if (lis_.isLiveInToMBB(*curli_, Loop->getHeader())) 398 BypassLoops.insert(Loop); 399 // Either way, skip the child loops. 400 continue; 401 } 402 403 // The child loops may be bypass loops. 404 Todo.append(Loop->begin(), Loop->end()); 405 } 406} 407 408 409//===----------------------------------------------------------------------===// 410// LiveIntervalMap 411//===----------------------------------------------------------------------===// 412 413// Work around the fact that the std::pair constructors are broken for pointer 414// pairs in some implementations. makeVV(x, 0) works. 415static inline std::pair<const VNInfo*, VNInfo*> 416makeVV(const VNInfo *a, VNInfo *b) { 417 return std::make_pair(a, b); 418} 419 420void LiveIntervalMap::reset(LiveInterval *li) { 421 li_ = li; 422 valueMap_.clear(); 423 liveOutCache_.clear(); 424} 425 426bool LiveIntervalMap::isComplexMapped(const VNInfo *ParentVNI) const { 427 ValueMap::const_iterator i = valueMap_.find(ParentVNI); 428 return i != valueMap_.end() && i->second == 0; 429} 430 431// defValue - Introduce a li_ def for ParentVNI that could be later than 432// ParentVNI->def. 433VNInfo *LiveIntervalMap::defValue(const VNInfo *ParentVNI, SlotIndex Idx) { 434 assert(li_ && "call reset first"); 435 assert(ParentVNI && "Mapping NULL value"); 436 assert(Idx.isValid() && "Invalid SlotIndex"); 437 assert(parentli_.getVNInfoAt(Idx) == ParentVNI && "Bad ParentVNI"); 438 439 // Create a new value. 440 VNInfo *VNI = li_->getNextValue(Idx, 0, lis_.getVNInfoAllocator()); 441 442 // Preserve the PHIDef bit. 443 if (ParentVNI->isPHIDef() && Idx == ParentVNI->def) 444 VNI->setIsPHIDef(true); 445 446 // Use insert for lookup, so we can add missing values with a second lookup. 447 std::pair<ValueMap::iterator,bool> InsP = 448 valueMap_.insert(makeVV(ParentVNI, Idx == ParentVNI->def ? VNI : 0)); 449 450 // This is now a complex def. Mark with a NULL in valueMap. 451 if (!InsP.second) 452 InsP.first->second = 0; 453 454 return VNI; 455} 456 457 458// mapValue - Find the mapped value for ParentVNI at Idx. 459// Potentially create phi-def values. 460VNInfo *LiveIntervalMap::mapValue(const VNInfo *ParentVNI, SlotIndex Idx, 461 bool *simple) { 462 assert(li_ && "call reset first"); 463 assert(ParentVNI && "Mapping NULL value"); 464 assert(Idx.isValid() && "Invalid SlotIndex"); 465 assert(parentli_.getVNInfoAt(Idx) == ParentVNI && "Bad ParentVNI"); 466 467 // Use insert for lookup, so we can add missing values with a second lookup. 468 std::pair<ValueMap::iterator,bool> InsP = 469 valueMap_.insert(makeVV(ParentVNI, 0)); 470 471 // This was an unknown value. Create a simple mapping. 472 if (InsP.second) { 473 if (simple) *simple = true; 474 return InsP.first->second = li_->createValueCopy(ParentVNI, 475 lis_.getVNInfoAllocator()); 476 } 477 478 // This was a simple mapped value. 479 if (InsP.first->second) { 480 if (simple) *simple = true; 481 return InsP.first->second; 482 } 483 484 // This is a complex mapped value. There may be multiple defs, and we may need 485 // to create phi-defs. 486 if (simple) *simple = false; 487 MachineBasicBlock *IdxMBB = lis_.getMBBFromIndex(Idx); 488 assert(IdxMBB && "No MBB at Idx"); 489 490 // Is there a def in the same MBB we can extend? 491 if (VNInfo *VNI = extendTo(IdxMBB, Idx)) 492 return VNI; 493 494 // Now for the fun part. We know that ParentVNI potentially has multiple defs, 495 // and we may need to create even more phi-defs to preserve VNInfo SSA form. 496 // Perform a search for all predecessor blocks where we know the dominating 497 // VNInfo. Insert phi-def VNInfos along the path back to IdxMBB. 498 DEBUG(dbgs() << "\n Reaching defs for BB#" << IdxMBB->getNumber() 499 << " at " << Idx << " in " << *li_ << '\n'); 500 501 // Blocks where li_ should be live-in. 502 SmallVector<MachineDomTreeNode*, 16> LiveIn; 503 LiveIn.push_back(mdt_[IdxMBB]); 504 505 // Using liveOutCache_ as a visited set, perform a BFS for all reaching defs. 506 for (unsigned i = 0; i != LiveIn.size(); ++i) { 507 MachineBasicBlock *MBB = LiveIn[i]->getBlock(); 508 for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(), 509 PE = MBB->pred_end(); PI != PE; ++PI) { 510 MachineBasicBlock *Pred = *PI; 511 // Is this a known live-out block? 512 std::pair<LiveOutMap::iterator,bool> LOIP = 513 liveOutCache_.insert(std::make_pair(Pred, LiveOutPair())); 514 // Yes, we have been here before. 515 if (!LOIP.second) { 516 DEBUG(if (VNInfo *VNI = LOIP.first->second.first) 517 dbgs() << " known valno #" << VNI->id 518 << " at BB#" << Pred->getNumber() << '\n'); 519 continue; 520 } 521 522 // Does Pred provide a live-out value? 523 SlotIndex Last = lis_.getMBBEndIdx(Pred).getPrevSlot(); 524 if (VNInfo *VNI = extendTo(Pred, Last)) { 525 MachineBasicBlock *DefMBB = lis_.getMBBFromIndex(VNI->def); 526 DEBUG(dbgs() << " found valno #" << VNI->id 527 << " from BB#" << DefMBB->getNumber() 528 << " at BB#" << Pred->getNumber() << '\n'); 529 LiveOutPair &LOP = LOIP.first->second; 530 LOP.first = VNI; 531 LOP.second = mdt_[DefMBB]; 532 continue; 533 } 534 // No, we need a live-in value for Pred as well 535 if (Pred != IdxMBB) 536 LiveIn.push_back(mdt_[Pred]); 537 } 538 } 539 540 // We may need to add phi-def values to preserve the SSA form. 541 // This is essentially the same iterative algorithm that SSAUpdater uses, 542 // except we already have a dominator tree, so we don't have to recompute it. 543 VNInfo *IdxVNI = 0; 544 unsigned Changes; 545 do { 546 Changes = 0; 547 DEBUG(dbgs() << " Iterating over " << LiveIn.size() << " blocks.\n"); 548 // Propagate live-out values down the dominator tree, inserting phi-defs when 549 // necessary. Since LiveIn was created by a BFS, going backwards makes it more 550 // likely for us to visit immediate dominators before their children. 551 for (unsigned i = LiveIn.size(); i; --i) { 552 MachineDomTreeNode *Node = LiveIn[i-1]; 553 MachineBasicBlock *MBB = Node->getBlock(); 554 MachineDomTreeNode *IDom = Node->getIDom(); 555 LiveOutPair IDomValue; 556 // We need a live-in value to a block with no immediate dominator? 557 // This is probably an unreachable block that has survived somehow. 558 bool needPHI = !IDom; 559 560 // Get the IDom live-out value. 561 if (!needPHI) { 562 LiveOutMap::iterator I = liveOutCache_.find(IDom->getBlock()); 563 if (I != liveOutCache_.end()) 564 IDomValue = I->second; 565 else 566 // If IDom is outside our set of live-out blocks, there must be new 567 // defs, and we need a phi-def here. 568 needPHI = true; 569 } 570 571 // IDom dominates all of our predecessors, but it may not be the immediate 572 // dominator. Check if any of them have live-out values that are properly 573 // dominated by IDom. If so, we need a phi-def here. 574 if (!needPHI) { 575 for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(), 576 PE = MBB->pred_end(); PI != PE; ++PI) { 577 LiveOutPair Value = liveOutCache_[*PI]; 578 if (!Value.first || Value.first == IDomValue.first) 579 continue; 580 // This predecessor is carrying something other than IDomValue. 581 // It could be because IDomValue hasn't propagated yet, or it could be 582 // because MBB is in the dominance frontier of that value. 583 if (mdt_.dominates(IDom, Value.second)) { 584 needPHI = true; 585 break; 586 } 587 } 588 } 589 590 // Create a phi-def if required. 591 if (needPHI) { 592 ++Changes; 593 SlotIndex Start = lis_.getMBBStartIdx(MBB); 594 VNInfo *VNI = li_->getNextValue(Start, 0, lis_.getVNInfoAllocator()); 595 VNI->setIsPHIDef(true); 596 DEBUG(dbgs() << " - BB#" << MBB->getNumber() 597 << " phi-def #" << VNI->id << " at " << Start << '\n'); 598 // We no longer need li_ to be live-in. 599 LiveIn.erase(LiveIn.begin()+(i-1)); 600 // Blocks in LiveIn are either IdxMBB, or have a value live-through. 601 if (MBB == IdxMBB) 602 IdxVNI = VNI; 603 // Check if we need to update live-out info. 604 LiveOutMap::iterator I = liveOutCache_.find(MBB); 605 if (I == liveOutCache_.end() || I->second.second == Node) { 606 // We already have a live-out defined in MBB, so this must be IdxMBB. 607 assert(MBB == IdxMBB && "Adding phi-def to known live-out"); 608 li_->addRange(LiveRange(Start, Idx.getNextSlot(), VNI)); 609 } else { 610 // This phi-def is also live-out, so color the whole block. 611 li_->addRange(LiveRange(Start, lis_.getMBBEndIdx(MBB), VNI)); 612 I->second = LiveOutPair(VNI, Node); 613 } 614 } else if (IDomValue.first) { 615 // No phi-def here. Remember incoming value for IdxMBB. 616 if (MBB == IdxMBB) 617 IdxVNI = IDomValue.first; 618 // Propagate IDomValue if needed: 619 // MBB is live-out and doesn't define its own value. 620 LiveOutMap::iterator I = liveOutCache_.find(MBB); 621 if (I != liveOutCache_.end() && I->second.second != Node && 622 I->second.first != IDomValue.first) { 623 ++Changes; 624 I->second = IDomValue; 625 DEBUG(dbgs() << " - BB#" << MBB->getNumber() 626 << " idom valno #" << IDomValue.first->id 627 << " from BB#" << IDom->getBlock()->getNumber() << '\n'); 628 } 629 } 630 } 631 DEBUG(dbgs() << " - made " << Changes << " changes.\n"); 632 } while (Changes); 633 634 assert(IdxVNI && "Didn't find value for Idx"); 635 636#ifndef NDEBUG 637 // Check the liveOutCache_ invariants. 638 for (LiveOutMap::iterator I = liveOutCache_.begin(), E = liveOutCache_.end(); 639 I != E; ++I) { 640 assert(I->first && "Null MBB entry in cache"); 641 assert(I->second.first && "Null VNInfo in cache"); 642 assert(I->second.second && "Null DomTreeNode in cache"); 643 if (I->second.second->getBlock() == I->first) 644 continue; 645 for (MachineBasicBlock::pred_iterator PI = I->first->pred_begin(), 646 PE = I->first->pred_end(); PI != PE; ++PI) 647 assert(liveOutCache_.lookup(*PI) == I->second && "Bad invariant"); 648 } 649#endif 650 651 // Since we went through the trouble of a full BFS visiting all reaching defs, 652 // the values in LiveIn are now accurate. No more phi-defs are needed 653 // for these blocks, so we can color the live ranges. 654 // This makes the next mapValue call much faster. 655 for (unsigned i = 0, e = LiveIn.size(); i != e; ++i) { 656 MachineBasicBlock *MBB = LiveIn[i]->getBlock(); 657 SlotIndex Start = lis_.getMBBStartIdx(MBB); 658 if (MBB == IdxMBB) { 659 li_->addRange(LiveRange(Start, Idx.getNextSlot(), IdxVNI)); 660 continue; 661 } 662 // Anything in LiveIn other than IdxMBB is live-through. 663 VNInfo *VNI = liveOutCache_.lookup(MBB).first; 664 assert(VNI && "Missing block value"); 665 li_->addRange(LiveRange(Start, lis_.getMBBEndIdx(MBB), VNI)); 666 } 667 668 return IdxVNI; 669} 670 671// extendTo - Find the last li_ value defined in MBB at or before Idx. The 672// parentli_ is assumed to be live at Idx. Extend the live range to Idx. 673// Return the found VNInfo, or NULL. 674VNInfo *LiveIntervalMap::extendTo(const MachineBasicBlock *MBB, SlotIndex Idx) { 675 assert(li_ && "call reset first"); 676 LiveInterval::iterator I = std::upper_bound(li_->begin(), li_->end(), Idx); 677 if (I == li_->begin()) 678 return 0; 679 --I; 680 if (I->end <= lis_.getMBBStartIdx(MBB)) 681 return 0; 682 if (I->end <= Idx) 683 I->end = Idx.getNextSlot(); 684 return I->valno; 685} 686 687// addSimpleRange - Add a simple range from parentli_ to li_. 688// ParentVNI must be live in the [Start;End) interval. 689void LiveIntervalMap::addSimpleRange(SlotIndex Start, SlotIndex End, 690 const VNInfo *ParentVNI) { 691 assert(li_ && "call reset first"); 692 bool simple; 693 VNInfo *VNI = mapValue(ParentVNI, Start, &simple); 694 // A simple mapping is easy. 695 if (simple) { 696 li_->addRange(LiveRange(Start, End, VNI)); 697 return; 698 } 699 700 // ParentVNI is a complex value. We must map per MBB. 701 MachineFunction::iterator MBB = lis_.getMBBFromIndex(Start); 702 MachineFunction::iterator MBBE = lis_.getMBBFromIndex(End.getPrevSlot()); 703 704 if (MBB == MBBE) { 705 li_->addRange(LiveRange(Start, End, VNI)); 706 return; 707 } 708 709 // First block. 710 li_->addRange(LiveRange(Start, lis_.getMBBEndIdx(MBB), VNI)); 711 712 // Run sequence of full blocks. 713 for (++MBB; MBB != MBBE; ++MBB) { 714 Start = lis_.getMBBStartIdx(MBB); 715 li_->addRange(LiveRange(Start, lis_.getMBBEndIdx(MBB), 716 mapValue(ParentVNI, Start))); 717 } 718 719 // Final block. 720 Start = lis_.getMBBStartIdx(MBB); 721 if (Start != End) 722 li_->addRange(LiveRange(Start, End, mapValue(ParentVNI, Start))); 723} 724 725/// addRange - Add live ranges to li_ where [Start;End) intersects parentli_. 726/// All needed values whose def is not inside [Start;End) must be defined 727/// beforehand so mapValue will work. 728void LiveIntervalMap::addRange(SlotIndex Start, SlotIndex End) { 729 assert(li_ && "call reset first"); 730 LiveInterval::const_iterator B = parentli_.begin(), E = parentli_.end(); 731 LiveInterval::const_iterator I = std::lower_bound(B, E, Start); 732 733 // Check if --I begins before Start and overlaps. 734 if (I != B) { 735 --I; 736 if (I->end > Start) 737 addSimpleRange(Start, std::min(End, I->end), I->valno); 738 ++I; 739 } 740 741 // The remaining ranges begin after Start. 742 for (;I != E && I->start < End; ++I) 743 addSimpleRange(I->start, std::min(End, I->end), I->valno); 744} 745 746 747//===----------------------------------------------------------------------===// 748// Split Editor 749//===----------------------------------------------------------------------===// 750 751/// Create a new SplitEditor for editing the LiveInterval analyzed by SA. 752SplitEditor::SplitEditor(SplitAnalysis &sa, 753 LiveIntervals &lis, 754 VirtRegMap &vrm, 755 MachineDominatorTree &mdt, 756 LiveRangeEdit &edit) 757 : sa_(sa), lis_(lis), vrm_(vrm), 758 mri_(vrm.getMachineFunction().getRegInfo()), 759 tii_(*vrm.getMachineFunction().getTarget().getInstrInfo()), 760 tri_(*vrm.getMachineFunction().getTarget().getRegisterInfo()), 761 edit_(edit), 762 dupli_(lis_, mdt, edit.getParent()), 763 openli_(lis_, mdt, edit.getParent()) 764{ 765 // We don't need an AliasAnalysis since we will only be performing 766 // cheap-as-a-copy remats anyway. 767 edit_.anyRematerializable(lis_, tii_, 0); 768} 769 770bool SplitEditor::intervalsLiveAt(SlotIndex Idx) const { 771 for (LiveRangeEdit::iterator I = edit_.begin(), E = edit_.end(); I != E; ++I) 772 if (*I != dupli_.getLI() && (*I)->liveAt(Idx)) 773 return true; 774 return false; 775} 776 777VNInfo *SplitEditor::defFromParent(LiveIntervalMap &Reg, 778 VNInfo *ParentVNI, 779 SlotIndex UseIdx, 780 MachineBasicBlock &MBB, 781 MachineBasicBlock::iterator I) { 782 VNInfo *VNI = 0; 783 MachineInstr *CopyMI = 0; 784 SlotIndex Def; 785 786 // Attempt cheap-as-a-copy rematerialization. 787 LiveRangeEdit::Remat RM(ParentVNI); 788 if (edit_.canRematerializeAt(RM, UseIdx, true, lis_)) { 789 Def = edit_.rematerializeAt(MBB, I, Reg.getLI()->reg, RM, 790 lis_, tii_, tri_); 791 } else { 792 // Can't remat, just insert a copy from parent. 793 CopyMI = BuildMI(MBB, I, DebugLoc(), tii_.get(TargetOpcode::COPY), 794 Reg.getLI()->reg).addReg(edit_.getReg()); 795 Def = lis_.InsertMachineInstrInMaps(CopyMI).getDefIndex(); 796 } 797 798 // Define the value in Reg. 799 VNI = Reg.defValue(ParentVNI, Def); 800 VNI->setCopy(CopyMI); 801 802 // Add minimal liveness for the new value. 803 if (UseIdx < Def) 804 UseIdx = Def; 805 Reg.getLI()->addRange(LiveRange(Def, UseIdx.getNextSlot(), VNI)); 806 return VNI; 807} 808 809/// Create a new virtual register and live interval. 810void SplitEditor::openIntv() { 811 assert(!openli_.getLI() && "Previous LI not closed before openIntv"); 812 if (!dupli_.getLI()) 813 dupli_.reset(&edit_.create(mri_, lis_, vrm_)); 814 815 openli_.reset(&edit_.create(mri_, lis_, vrm_)); 816} 817 818/// enterIntvBefore - Enter openli before the instruction at Idx. If curli is 819/// not live before Idx, a COPY is not inserted. 820void SplitEditor::enterIntvBefore(SlotIndex Idx) { 821 assert(openli_.getLI() && "openIntv not called before enterIntvBefore"); 822 Idx = Idx.getUseIndex(); 823 DEBUG(dbgs() << " enterIntvBefore " << Idx); 824 VNInfo *ParentVNI = edit_.getParent().getVNInfoAt(Idx); 825 if (!ParentVNI) { 826 DEBUG(dbgs() << ": not live\n"); 827 return; 828 } 829 DEBUG(dbgs() << ": valno " << ParentVNI->id); 830 truncatedValues.insert(ParentVNI); 831 MachineInstr *MI = lis_.getInstructionFromIndex(Idx); 832 assert(MI && "enterIntvBefore called with invalid index"); 833 834 defFromParent(openli_, ParentVNI, Idx, *MI->getParent(), MI); 835 836 DEBUG(dbgs() << ": " << *openli_.getLI() << '\n'); 837} 838 839/// enterIntvAtEnd - Enter openli at the end of MBB. 840void SplitEditor::enterIntvAtEnd(MachineBasicBlock &MBB) { 841 assert(openli_.getLI() && "openIntv not called before enterIntvAtEnd"); 842 SlotIndex End = lis_.getMBBEndIdx(&MBB).getPrevSlot(); 843 DEBUG(dbgs() << " enterIntvAtEnd BB#" << MBB.getNumber() << ", " << End); 844 VNInfo *ParentVNI = edit_.getParent().getVNInfoAt(End); 845 if (!ParentVNI) { 846 DEBUG(dbgs() << ": not live\n"); 847 return; 848 } 849 DEBUG(dbgs() << ": valno " << ParentVNI->id); 850 truncatedValues.insert(ParentVNI); 851 defFromParent(openli_, ParentVNI, End, MBB, MBB.getFirstTerminator()); 852 DEBUG(dbgs() << ": " << *openli_.getLI() << '\n'); 853} 854 855/// useIntv - indicate that all instructions in MBB should use openli. 856void SplitEditor::useIntv(const MachineBasicBlock &MBB) { 857 useIntv(lis_.getMBBStartIdx(&MBB), lis_.getMBBEndIdx(&MBB)); 858} 859 860void SplitEditor::useIntv(SlotIndex Start, SlotIndex End) { 861 assert(openli_.getLI() && "openIntv not called before useIntv"); 862 openli_.addRange(Start, End); 863 DEBUG(dbgs() << " use [" << Start << ';' << End << "): " 864 << *openli_.getLI() << '\n'); 865} 866 867/// leaveIntvAfter - Leave openli after the instruction at Idx. 868void SplitEditor::leaveIntvAfter(SlotIndex Idx) { 869 assert(openli_.getLI() && "openIntv not called before leaveIntvAfter"); 870 DEBUG(dbgs() << " leaveIntvAfter " << Idx); 871 872 // The interval must be live beyond the instruction at Idx. 873 Idx = Idx.getBoundaryIndex(); 874 VNInfo *ParentVNI = edit_.getParent().getVNInfoAt(Idx); 875 if (!ParentVNI) { 876 DEBUG(dbgs() << ": not live\n"); 877 return; 878 } 879 DEBUG(dbgs() << ": valno " << ParentVNI->id); 880 881 MachineBasicBlock::iterator MII = lis_.getInstructionFromIndex(Idx); 882 VNInfo *VNI = defFromParent(dupli_, ParentVNI, Idx, 883 *MII->getParent(), llvm::next(MII)); 884 885 // Make sure that openli is properly extended from Idx to the new copy. 886 // FIXME: This shouldn't be necessary for remats. 887 openli_.addSimpleRange(Idx, VNI->def, ParentVNI); 888 889 DEBUG(dbgs() << ": " << *openli_.getLI() << '\n'); 890} 891 892/// leaveIntvAtTop - Leave the interval at the top of MBB. 893/// Currently, only one value can leave the interval. 894void SplitEditor::leaveIntvAtTop(MachineBasicBlock &MBB) { 895 assert(openli_.getLI() && "openIntv not called before leaveIntvAtTop"); 896 SlotIndex Start = lis_.getMBBStartIdx(&MBB); 897 DEBUG(dbgs() << " leaveIntvAtTop BB#" << MBB.getNumber() << ", " << Start); 898 899 VNInfo *ParentVNI = edit_.getParent().getVNInfoAt(Start); 900 if (!ParentVNI) { 901 DEBUG(dbgs() << ": not live\n"); 902 return; 903 } 904 905 VNInfo *VNI = defFromParent(dupli_, ParentVNI, Start, MBB, 906 MBB.SkipPHIsAndLabels(MBB.begin())); 907 908 // Finally we must make sure that openli is properly extended from Start to 909 // the new copy. 910 openli_.addSimpleRange(Start, VNI->def, ParentVNI); 911 DEBUG(dbgs() << ": " << *openli_.getLI() << '\n'); 912} 913 914/// closeIntv - Indicate that we are done editing the currently open 915/// LiveInterval, and ranges can be trimmed. 916void SplitEditor::closeIntv() { 917 assert(openli_.getLI() && "openIntv not called before closeIntv"); 918 919 DEBUG(dbgs() << " closeIntv cleaning up\n"); 920 DEBUG(dbgs() << " open " << *openli_.getLI() << '\n'); 921 openli_.reset(0); 922} 923 924/// rewrite - Rewrite all uses of reg to use the new registers. 925void SplitEditor::rewrite(unsigned reg) { 926 for (MachineRegisterInfo::reg_iterator RI = mri_.reg_begin(reg), 927 RE = mri_.reg_end(); RI != RE;) { 928 MachineOperand &MO = RI.getOperand(); 929 unsigned OpNum = RI.getOperandNo(); 930 MachineInstr *MI = MO.getParent(); 931 ++RI; 932 if (MI->isDebugValue()) { 933 DEBUG(dbgs() << "Zapping " << *MI); 934 // FIXME: We can do much better with debug values. 935 MO.setReg(0); 936 continue; 937 } 938 SlotIndex Idx = lis_.getInstructionIndex(MI); 939 Idx = MO.isUse() ? Idx.getUseIndex() : Idx.getDefIndex(); 940 LiveInterval *LI = 0; 941 for (LiveRangeEdit::iterator I = edit_.begin(), E = edit_.end(); I != E; 942 ++I) { 943 LiveInterval *testli = *I; 944 if (testli->liveAt(Idx)) { 945 LI = testli; 946 break; 947 } 948 } 949 DEBUG(dbgs() << " rewr BB#" << MI->getParent()->getNumber() << '\t'<< Idx); 950 assert(LI && "No register was live at use"); 951 MO.setReg(LI->reg); 952 if (MO.isUse() && !MI->isRegTiedToDefOperand(OpNum)) 953 MO.setIsKill(LI->killedAt(Idx.getDefIndex())); 954 DEBUG(dbgs() << '\t' << *MI); 955 } 956} 957 958void 959SplitEditor::addTruncSimpleRange(SlotIndex Start, SlotIndex End, VNInfo *VNI) { 960 // Build vector of iterator pairs from the intervals. 961 typedef std::pair<LiveInterval::const_iterator, 962 LiveInterval::const_iterator> IIPair; 963 SmallVector<IIPair, 8> Iters; 964 for (LiveRangeEdit::iterator LI = edit_.begin(), LE = edit_.end(); LI != LE; 965 ++LI) { 966 if (*LI == dupli_.getLI()) 967 continue; 968 LiveInterval::const_iterator I = (*LI)->find(Start); 969 LiveInterval::const_iterator E = (*LI)->end(); 970 if (I != E) 971 Iters.push_back(std::make_pair(I, E)); 972 } 973 974 SlotIndex sidx = Start; 975 // Break [Start;End) into segments that don't overlap any intervals. 976 for (;;) { 977 SlotIndex next = sidx, eidx = End; 978 // Find overlapping intervals. 979 for (unsigned i = 0; i != Iters.size() && sidx < eidx; ++i) { 980 LiveInterval::const_iterator I = Iters[i].first; 981 // Interval I is overlapping [sidx;eidx). Trim sidx. 982 if (I->start <= sidx) { 983 sidx = I->end; 984 // Move to the next run, remove iters when all are consumed. 985 I = ++Iters[i].first; 986 if (I == Iters[i].second) { 987 Iters.erase(Iters.begin() + i); 988 --i; 989 continue; 990 } 991 } 992 // Trim eidx too if needed. 993 if (I->start >= eidx) 994 continue; 995 eidx = I->start; 996 next = I->end; 997 } 998 // Now, [sidx;eidx) doesn't overlap anything in intervals_. 999 if (sidx < eidx) 1000 dupli_.addSimpleRange(sidx, eidx, VNI); 1001 // If the interval end was truncated, we can try again from next. 1002 if (next <= sidx) 1003 break; 1004 sidx = next; 1005 } 1006} 1007 1008void SplitEditor::computeRemainder() { 1009 // First we need to fill in the live ranges in dupli. 1010 // If values were redefined, we need a full recoloring with SSA update. 1011 // If values were truncated, we only need to truncate the ranges. 1012 // If values were partially rematted, we should shrink to uses. 1013 // If values were fully rematted, they should be omitted. 1014 // FIXME: If a single value is redefined, just move the def and truncate. 1015 LiveInterval &parent = edit_.getParent(); 1016 1017 // Values that are fully contained in the split intervals. 1018 SmallPtrSet<const VNInfo*, 8> deadValues; 1019 // Map all curli values that should have live defs in dupli. 1020 for (LiveInterval::const_vni_iterator I = parent.vni_begin(), 1021 E = parent.vni_end(); I != E; ++I) { 1022 const VNInfo *VNI = *I; 1023 // Don't transfer unused values to the new intervals. 1024 if (VNI->isUnused()) 1025 continue; 1026 // Original def is contained in the split intervals. 1027 if (intervalsLiveAt(VNI->def)) { 1028 // Did this value escape? 1029 if (dupli_.isMapped(VNI)) 1030 truncatedValues.insert(VNI); 1031 else 1032 deadValues.insert(VNI); 1033 continue; 1034 } 1035 // Add minimal live range at the definition. 1036 VNInfo *DVNI = dupli_.defValue(VNI, VNI->def); 1037 dupli_.getLI()->addRange(LiveRange(VNI->def, VNI->def.getNextSlot(), DVNI)); 1038 } 1039 1040 // Add all ranges to dupli. 1041 for (LiveInterval::const_iterator I = parent.begin(), E = parent.end(); 1042 I != E; ++I) { 1043 const LiveRange &LR = *I; 1044 if (truncatedValues.count(LR.valno)) { 1045 // recolor after removing intervals_. 1046 addTruncSimpleRange(LR.start, LR.end, LR.valno); 1047 } else if (!deadValues.count(LR.valno)) { 1048 // recolor without truncation. 1049 dupli_.addSimpleRange(LR.start, LR.end, LR.valno); 1050 } 1051 } 1052 1053 // Extend dupli_ to be live out of any critical loop predecessors. 1054 // This means we have multiple registers live out of those blocks. 1055 // The alternative would be to split the critical edges. 1056 if (criticalPreds_.empty()) 1057 return; 1058 for (SplitAnalysis::BlockPtrSet::iterator I = criticalPreds_.begin(), 1059 E = criticalPreds_.end(); I != E; ++I) 1060 dupli_.extendTo(*I, lis_.getMBBEndIdx(*I).getPrevSlot()); 1061 criticalPreds_.clear(); 1062} 1063 1064void SplitEditor::finish() { 1065 assert(!openli_.getLI() && "Previous LI not closed before rewrite"); 1066 assert(dupli_.getLI() && "No dupli for rewrite. Noop spilt?"); 1067 1068 // Complete dupli liveness. 1069 computeRemainder(); 1070 1071 // Get rid of unused values and set phi-kill flags. 1072 for (LiveRangeEdit::iterator I = edit_.begin(), E = edit_.end(); I != E; ++I) 1073 (*I)->RenumberValues(lis_); 1074 1075 // Rewrite instructions. 1076 rewrite(edit_.getReg()); 1077 1078 // Now check if any registers were separated into multiple components. 1079 ConnectedVNInfoEqClasses ConEQ(lis_); 1080 for (unsigned i = 0, e = edit_.size(); i != e; ++i) { 1081 // Don't use iterators, they are invalidated by create() below. 1082 LiveInterval *li = edit_.get(i); 1083 unsigned NumComp = ConEQ.Classify(li); 1084 if (NumComp <= 1) 1085 continue; 1086 DEBUG(dbgs() << " " << NumComp << " components: " << *li << '\n'); 1087 SmallVector<LiveInterval*, 8> dups; 1088 dups.push_back(li); 1089 for (unsigned i = 1; i != NumComp; ++i) 1090 dups.push_back(&edit_.create(mri_, lis_, vrm_)); 1091 ConEQ.Distribute(&dups[0]); 1092 // Rewrite uses to the new regs. 1093 rewrite(li->reg); 1094 } 1095 1096 // Calculate spill weight and allocation hints for new intervals. 1097 VirtRegAuxInfo vrai(vrm_.getMachineFunction(), lis_, sa_.loops_); 1098 for (LiveRangeEdit::iterator I = edit_.begin(), E = edit_.end(); I != E; ++I){ 1099 LiveInterval &li = **I; 1100 vrai.CalculateRegClass(li.reg); 1101 vrai.CalculateWeightAndHint(li); 1102 DEBUG(dbgs() << " new interval " << mri_.getRegClass(li.reg)->getName() 1103 << ":" << li << '\n'); 1104 } 1105} 1106 1107 1108//===----------------------------------------------------------------------===// 1109// Loop Splitting 1110//===----------------------------------------------------------------------===// 1111 1112void SplitEditor::splitAroundLoop(const MachineLoop *Loop) { 1113 SplitAnalysis::LoopBlocks Blocks; 1114 sa_.getLoopBlocks(Loop, Blocks); 1115 1116 DEBUG({ 1117 dbgs() << " splitAround"; sa_.print(Blocks, dbgs()); dbgs() << '\n'; 1118 }); 1119 1120 // Break critical edges as needed. 1121 SplitAnalysis::BlockPtrSet CriticalExits; 1122 sa_.getCriticalExits(Blocks, CriticalExits); 1123 assert(CriticalExits.empty() && "Cannot break critical exits yet"); 1124 1125 // Get critical predecessors so computeRemainder can deal with them. 1126 sa_.getCriticalPreds(Blocks, criticalPreds_); 1127 1128 // Create new live interval for the loop. 1129 openIntv(); 1130 1131 // Insert copies in the predecessors if live-in to the header. 1132 if (lis_.isLiveInToMBB(edit_.getParent(), Loop->getHeader())) { 1133 for (SplitAnalysis::BlockPtrSet::iterator I = Blocks.Preds.begin(), 1134 E = Blocks.Preds.end(); I != E; ++I) { 1135 MachineBasicBlock &MBB = const_cast<MachineBasicBlock&>(**I); 1136 enterIntvAtEnd(MBB); 1137 } 1138 } 1139 1140 // Switch all loop blocks. 1141 for (SplitAnalysis::BlockPtrSet::iterator I = Blocks.Loop.begin(), 1142 E = Blocks.Loop.end(); I != E; ++I) 1143 useIntv(**I); 1144 1145 // Insert back copies in the exit blocks. 1146 for (SplitAnalysis::BlockPtrSet::iterator I = Blocks.Exits.begin(), 1147 E = Blocks.Exits.end(); I != E; ++I) { 1148 MachineBasicBlock &MBB = const_cast<MachineBasicBlock&>(**I); 1149 leaveIntvAtTop(MBB); 1150 } 1151 1152 // Done. 1153 closeIntv(); 1154 finish(); 1155} 1156 1157 1158//===----------------------------------------------------------------------===// 1159// Single Block Splitting 1160//===----------------------------------------------------------------------===// 1161 1162/// getMultiUseBlocks - if curli has more than one use in a basic block, it 1163/// may be an advantage to split curli for the duration of the block. 1164bool SplitAnalysis::getMultiUseBlocks(BlockPtrSet &Blocks) { 1165 // If curli is local to one block, there is no point to splitting it. 1166 if (usingBlocks_.size() <= 1) 1167 return false; 1168 // Add blocks with multiple uses. 1169 for (BlockCountMap::iterator I = usingBlocks_.begin(), E = usingBlocks_.end(); 1170 I != E; ++I) 1171 switch (I->second) { 1172 case 0: 1173 case 1: 1174 continue; 1175 case 2: { 1176 // When there are only two uses and curli is both live in and live out, 1177 // we don't really win anything by isolating the block since we would be 1178 // inserting two copies. 1179 // The remaing register would still have two uses in the block. (Unless it 1180 // separates into disconnected components). 1181 if (lis_.isLiveInToMBB(*curli_, I->first) && 1182 lis_.isLiveOutOfMBB(*curli_, I->first)) 1183 continue; 1184 } // Fall through. 1185 default: 1186 Blocks.insert(I->first); 1187 } 1188 return !Blocks.empty(); 1189} 1190 1191/// splitSingleBlocks - Split curli into a separate live interval inside each 1192/// basic block in Blocks. 1193void SplitEditor::splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks) { 1194 DEBUG(dbgs() << " splitSingleBlocks for " << Blocks.size() << " blocks.\n"); 1195 // Determine the first and last instruction using curli in each block. 1196 typedef std::pair<SlotIndex,SlotIndex> IndexPair; 1197 typedef DenseMap<const MachineBasicBlock*,IndexPair> IndexPairMap; 1198 IndexPairMap MBBRange; 1199 for (SplitAnalysis::InstrPtrSet::const_iterator I = sa_.usingInstrs_.begin(), 1200 E = sa_.usingInstrs_.end(); I != E; ++I) { 1201 const MachineBasicBlock *MBB = (*I)->getParent(); 1202 if (!Blocks.count(MBB)) 1203 continue; 1204 SlotIndex Idx = lis_.getInstructionIndex(*I); 1205 DEBUG(dbgs() << " BB#" << MBB->getNumber() << '\t' << Idx << '\t' << **I); 1206 IndexPair &IP = MBBRange[MBB]; 1207 if (!IP.first.isValid() || Idx < IP.first) 1208 IP.first = Idx; 1209 if (!IP.second.isValid() || Idx > IP.second) 1210 IP.second = Idx; 1211 } 1212 1213 // Create a new interval for each block. 1214 for (SplitAnalysis::BlockPtrSet::const_iterator I = Blocks.begin(), 1215 E = Blocks.end(); I != E; ++I) { 1216 IndexPair &IP = MBBRange[*I]; 1217 DEBUG(dbgs() << " splitting for BB#" << (*I)->getNumber() << ": [" 1218 << IP.first << ';' << IP.second << ")\n"); 1219 assert(IP.first.isValid() && IP.second.isValid()); 1220 1221 openIntv(); 1222 enterIntvBefore(IP.first); 1223 useIntv(IP.first.getBaseIndex(), IP.second.getBoundaryIndex()); 1224 leaveIntvAfter(IP.second); 1225 closeIntv(); 1226 } 1227 finish(); 1228} 1229 1230 1231//===----------------------------------------------------------------------===// 1232// Sub Block Splitting 1233//===----------------------------------------------------------------------===// 1234 1235/// getBlockForInsideSplit - If curli is contained inside a single basic block, 1236/// and it wou pay to subdivide the interval inside that block, return it. 1237/// Otherwise return NULL. The returned block can be passed to 1238/// SplitEditor::splitInsideBlock. 1239const MachineBasicBlock *SplitAnalysis::getBlockForInsideSplit() { 1240 // The interval must be exclusive to one block. 1241 if (usingBlocks_.size() != 1) 1242 return 0; 1243 // Don't to this for less than 4 instructions. We want to be sure that 1244 // splitting actually reduces the instruction count per interval. 1245 if (usingInstrs_.size() < 4) 1246 return 0; 1247 return usingBlocks_.begin()->first; 1248} 1249 1250/// splitInsideBlock - Split curli into multiple intervals inside MBB. 1251void SplitEditor::splitInsideBlock(const MachineBasicBlock *MBB) { 1252 SmallVector<SlotIndex, 32> Uses; 1253 Uses.reserve(sa_.usingInstrs_.size()); 1254 for (SplitAnalysis::InstrPtrSet::const_iterator I = sa_.usingInstrs_.begin(), 1255 E = sa_.usingInstrs_.end(); I != E; ++I) 1256 if ((*I)->getParent() == MBB) 1257 Uses.push_back(lis_.getInstructionIndex(*I)); 1258 DEBUG(dbgs() << " splitInsideBlock BB#" << MBB->getNumber() << " for " 1259 << Uses.size() << " instructions.\n"); 1260 assert(Uses.size() >= 3 && "Need at least 3 instructions"); 1261 array_pod_sort(Uses.begin(), Uses.end()); 1262 1263 // Simple algorithm: Find the largest gap between uses as determined by slot 1264 // indices. Create new intervals for instructions before the gap and after the 1265 // gap. 1266 unsigned bestPos = 0; 1267 int bestGap = 0; 1268 DEBUG(dbgs() << " dist (" << Uses[0]); 1269 for (unsigned i = 1, e = Uses.size(); i != e; ++i) { 1270 int g = Uses[i-1].distance(Uses[i]); 1271 DEBUG(dbgs() << ") -" << g << "- (" << Uses[i]); 1272 if (g > bestGap) 1273 bestPos = i, bestGap = g; 1274 } 1275 DEBUG(dbgs() << "), best: -" << bestGap << "-\n"); 1276 1277 // bestPos points to the first use after the best gap. 1278 assert(bestPos > 0 && "Invalid gap"); 1279 1280 // FIXME: Don't create intervals for low densities. 1281 1282 // First interval before the gap. Don't create single-instr intervals. 1283 if (bestPos > 1) { 1284 openIntv(); 1285 enterIntvBefore(Uses.front()); 1286 useIntv(Uses.front().getBaseIndex(), Uses[bestPos-1].getBoundaryIndex()); 1287 leaveIntvAfter(Uses[bestPos-1]); 1288 closeIntv(); 1289 } 1290 1291 // Second interval after the gap. 1292 if (bestPos < Uses.size()-1) { 1293 openIntv(); 1294 enterIntvBefore(Uses[bestPos]); 1295 useIntv(Uses[bestPos].getBaseIndex(), Uses.back().getBoundaryIndex()); 1296 leaveIntvAfter(Uses.back()); 1297 closeIntv(); 1298 } 1299 1300 finish(); 1301} 1302