LiveIntervalAnalysis.cpp revision ae339babb2a2445e7bb009912a39994718f10d54
1//===-- LiveIntervalAnalysis.cpp - Live Interval Analysis -----------------===// 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 implements the LiveInterval analysis pass which is used 11// by the Linear Scan Register allocator. This pass linearizes the 12// basic blocks of the function in DFS order and uses the 13// LiveVariables pass to conservatively compute live intervals for 14// each virtual and physical register. 15// 16//===----------------------------------------------------------------------===// 17 18#define DEBUG_TYPE "liveintervals" 19#include "llvm/CodeGen/LiveIntervalAnalysis.h" 20#include "VirtRegMap.h" 21#include "llvm/Value.h" 22#include "llvm/Analysis/AliasAnalysis.h" 23#include "llvm/CodeGen/LiveVariables.h" 24#include "llvm/CodeGen/MachineFrameInfo.h" 25#include "llvm/CodeGen/MachineInstr.h" 26#include "llvm/CodeGen/MachineLoopInfo.h" 27#include "llvm/CodeGen/MachineRegisterInfo.h" 28#include "llvm/CodeGen/Passes.h" 29#include "llvm/CodeGen/PseudoSourceValue.h" 30#include "llvm/Target/TargetRegisterInfo.h" 31#include "llvm/Target/TargetInstrInfo.h" 32#include "llvm/Target/TargetMachine.h" 33#include "llvm/Support/CommandLine.h" 34#include "llvm/Support/Debug.h" 35#include "llvm/ADT/Statistic.h" 36#include "llvm/ADT/STLExtras.h" 37#include <algorithm> 38#include <cmath> 39using namespace llvm; 40 41// Hidden options for help debugging. 42static cl::opt<bool> DisableReMat("disable-rematerialization", 43 cl::init(false), cl::Hidden); 44 45static cl::opt<bool> SplitAtBB("split-intervals-at-bb", 46 cl::init(true), cl::Hidden); 47static cl::opt<int> SplitLimit("split-limit", 48 cl::init(-1), cl::Hidden); 49 50static cl::opt<bool> EnableAggressiveRemat("aggressive-remat", cl::Hidden); 51 52static cl::opt<bool> EnableFastSpilling("fast-spill", 53 cl::init(false), cl::Hidden); 54 55STATISTIC(numIntervals, "Number of original intervals"); 56STATISTIC(numIntervalsAfter, "Number of intervals after coalescing"); 57STATISTIC(numFolds , "Number of loads/stores folded into instructions"); 58STATISTIC(numSplits , "Number of intervals split"); 59 60char LiveIntervals::ID = 0; 61static RegisterPass<LiveIntervals> X("liveintervals", "Live Interval Analysis"); 62 63void LiveIntervals::getAnalysisUsage(AnalysisUsage &AU) const { 64 AU.addRequired<AliasAnalysis>(); 65 AU.addPreserved<AliasAnalysis>(); 66 AU.addPreserved<LiveVariables>(); 67 AU.addRequired<LiveVariables>(); 68 AU.addPreservedID(MachineLoopInfoID); 69 AU.addPreservedID(MachineDominatorsID); 70 AU.addPreservedID(PHIEliminationID); 71 AU.addRequiredID(PHIEliminationID); 72 AU.addRequiredID(TwoAddressInstructionPassID); 73 MachineFunctionPass::getAnalysisUsage(AU); 74} 75 76void LiveIntervals::releaseMemory() { 77 // Free the live intervals themselves. 78 for (DenseMap<unsigned, LiveInterval*>::iterator I = r2iMap_.begin(), 79 E = r2iMap_.end(); I != E; ++I) 80 delete I->second; 81 82 MBB2IdxMap.clear(); 83 Idx2MBBMap.clear(); 84 mi2iMap_.clear(); 85 i2miMap_.clear(); 86 r2iMap_.clear(); 87 // Release VNInfo memroy regions after all VNInfo objects are dtor'd. 88 VNInfoAllocator.Reset(); 89 while (!ClonedMIs.empty()) { 90 MachineInstr *MI = ClonedMIs.back(); 91 ClonedMIs.pop_back(); 92 mf_->DeleteMachineInstr(MI); 93 } 94} 95 96void LiveIntervals::computeNumbering() { 97 Index2MiMap OldI2MI = i2miMap_; 98 std::vector<IdxMBBPair> OldI2MBB = Idx2MBBMap; 99 100 Idx2MBBMap.clear(); 101 MBB2IdxMap.clear(); 102 mi2iMap_.clear(); 103 i2miMap_.clear(); 104 105 FunctionSize = 0; 106 107 // Number MachineInstrs and MachineBasicBlocks. 108 // Initialize MBB indexes to a sentinal. 109 MBB2IdxMap.resize(mf_->getNumBlockIDs(), std::make_pair(~0U,~0U)); 110 111 unsigned MIIndex = 0; 112 for (MachineFunction::iterator MBB = mf_->begin(), E = mf_->end(); 113 MBB != E; ++MBB) { 114 unsigned StartIdx = MIIndex; 115 116 // Insert an empty slot at the beginning of each block. 117 MIIndex += InstrSlots::NUM; 118 i2miMap_.push_back(0); 119 120 for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end(); 121 I != E; ++I) { 122 bool inserted = mi2iMap_.insert(std::make_pair(I, MIIndex)).second; 123 assert(inserted && "multiple MachineInstr -> index mappings"); 124 i2miMap_.push_back(I); 125 MIIndex += InstrSlots::NUM; 126 FunctionSize++; 127 128 // Insert an empty slot after every instruction. 129 MIIndex += InstrSlots::NUM; 130 i2miMap_.push_back(0); 131 } 132 133 // Set the MBB2IdxMap entry for this MBB. 134 MBB2IdxMap[MBB->getNumber()] = std::make_pair(StartIdx, MIIndex - 1); 135 Idx2MBBMap.push_back(std::make_pair(StartIdx, MBB)); 136 } 137 std::sort(Idx2MBBMap.begin(), Idx2MBBMap.end(), Idx2MBBCompare()); 138 139 if (!OldI2MI.empty()) 140 for (iterator OI = begin(), OE = end(); OI != OE; ++OI) { 141 for (LiveInterval::iterator LI = OI->second->begin(), 142 LE = OI->second->end(); LI != LE; ++LI) { 143 144 // Remap the start index of the live range to the corresponding new 145 // number, or our best guess at what it _should_ correspond to if the 146 // original instruction has been erased. This is either the following 147 // instruction or its predecessor. 148 unsigned index = LI->start / InstrSlots::NUM; 149 unsigned offset = LI->start % InstrSlots::NUM; 150 if (offset == InstrSlots::LOAD) { 151 std::vector<IdxMBBPair>::const_iterator I = 152 std::lower_bound(OldI2MBB.begin(), OldI2MBB.end(), LI->start); 153 // Take the pair containing the index 154 std::vector<IdxMBBPair>::const_iterator J = 155 (I == OldI2MBB.end() && OldI2MBB.size()>0) ? (I-1): I; 156 157 LI->start = getMBBStartIdx(J->second); 158 } else { 159 LI->start = mi2iMap_[OldI2MI[index]] + offset; 160 } 161 162 // Remap the ending index in the same way that we remapped the start, 163 // except for the final step where we always map to the immediately 164 // following instruction. 165 index = (LI->end - 1) / InstrSlots::NUM; 166 offset = LI->end % InstrSlots::NUM; 167 if (offset == InstrSlots::LOAD) { 168 // VReg dies at end of block. 169 std::vector<IdxMBBPair>::const_iterator I = 170 std::lower_bound(OldI2MBB.begin(), OldI2MBB.end(), LI->end); 171 --I; 172 173 LI->end = getMBBEndIdx(I->second) + 1; 174 } else { 175 unsigned idx = index; 176 while (index < OldI2MI.size() && !OldI2MI[index]) ++index; 177 178 if (index != OldI2MI.size()) 179 LI->end = mi2iMap_[OldI2MI[index]] + (idx == index ? offset : 0); 180 else 181 LI->end = InstrSlots::NUM * i2miMap_.size(); 182 } 183 } 184 185 for (LiveInterval::vni_iterator VNI = OI->second->vni_begin(), 186 VNE = OI->second->vni_end(); VNI != VNE; ++VNI) { 187 VNInfo* vni = *VNI; 188 189 // Remap the VNInfo def index, which works the same as the 190 // start indices above. VN's with special sentinel defs 191 // don't need to be remapped. 192 if (vni->def != ~0U && vni->def != ~1U) { 193 unsigned index = vni->def / InstrSlots::NUM; 194 unsigned offset = vni->def % InstrSlots::NUM; 195 if (offset == InstrSlots::LOAD) { 196 std::vector<IdxMBBPair>::const_iterator I = 197 std::lower_bound(OldI2MBB.begin(), OldI2MBB.end(), vni->def); 198 // Take the pair containing the index 199 std::vector<IdxMBBPair>::const_iterator J = 200 (I == OldI2MBB.end() && OldI2MBB.size()>0) ? (I-1): I; 201 202 vni->def = getMBBStartIdx(J->second); 203 } else { 204 vni->def = mi2iMap_[OldI2MI[index]] + offset; 205 } 206 } 207 208 // Remap the VNInfo kill indices, which works the same as 209 // the end indices above. 210 for (size_t i = 0; i < vni->kills.size(); ++i) { 211 // PHI kills don't need to be remapped. 212 if (!vni->kills[i]) continue; 213 214 unsigned index = (vni->kills[i]-1) / InstrSlots::NUM; 215 unsigned offset = vni->kills[i] % InstrSlots::NUM; 216 if (offset == InstrSlots::STORE) { 217 std::vector<IdxMBBPair>::const_iterator I = 218 std::lower_bound(OldI2MBB.begin(), OldI2MBB.end(), vni->kills[i]); 219 --I; 220 221 vni->kills[i] = getMBBEndIdx(I->second); 222 } else { 223 unsigned idx = index; 224 while (index < OldI2MI.size() && !OldI2MI[index]) ++index; 225 226 if (index != OldI2MI.size()) 227 vni->kills[i] = mi2iMap_[OldI2MI[index]] + 228 (idx == index ? offset : 0); 229 else 230 vni->kills[i] = InstrSlots::NUM * i2miMap_.size(); 231 } 232 } 233 } 234 } 235} 236 237/// runOnMachineFunction - Register allocate the whole function 238/// 239bool LiveIntervals::runOnMachineFunction(MachineFunction &fn) { 240 mf_ = &fn; 241 mri_ = &mf_->getRegInfo(); 242 tm_ = &fn.getTarget(); 243 tri_ = tm_->getRegisterInfo(); 244 tii_ = tm_->getInstrInfo(); 245 aa_ = &getAnalysis<AliasAnalysis>(); 246 lv_ = &getAnalysis<LiveVariables>(); 247 allocatableRegs_ = tri_->getAllocatableSet(fn); 248 249 computeNumbering(); 250 computeIntervals(); 251 252 numIntervals += getNumIntervals(); 253 254 DOUT << "********** INTERVALS **********\n"; 255 for (iterator I = begin(), E = end(); I != E; ++I) { 256 I->second->print(DOUT, tri_); 257 DOUT << "\n"; 258 } 259 260 numIntervalsAfter += getNumIntervals(); 261 DEBUG(dump()); 262 return true; 263} 264 265/// print - Implement the dump method. 266void LiveIntervals::print(std::ostream &O, const Module* ) const { 267 O << "********** INTERVALS **********\n"; 268 for (const_iterator I = begin(), E = end(); I != E; ++I) { 269 I->second->print(O, tri_); 270 O << "\n"; 271 } 272 273 O << "********** MACHINEINSTRS **********\n"; 274 for (MachineFunction::iterator mbbi = mf_->begin(), mbbe = mf_->end(); 275 mbbi != mbbe; ++mbbi) { 276 O << ((Value*)mbbi->getBasicBlock())->getName() << ":\n"; 277 for (MachineBasicBlock::iterator mii = mbbi->begin(), 278 mie = mbbi->end(); mii != mie; ++mii) { 279 O << getInstructionIndex(mii) << '\t' << *mii; 280 } 281 } 282} 283 284/// conflictsWithPhysRegDef - Returns true if the specified register 285/// is defined during the duration of the specified interval. 286bool LiveIntervals::conflictsWithPhysRegDef(const LiveInterval &li, 287 VirtRegMap &vrm, unsigned reg) { 288 for (LiveInterval::Ranges::const_iterator 289 I = li.ranges.begin(), E = li.ranges.end(); I != E; ++I) { 290 for (unsigned index = getBaseIndex(I->start), 291 end = getBaseIndex(I->end-1) + InstrSlots::NUM; index != end; 292 index += InstrSlots::NUM) { 293 // skip deleted instructions 294 while (index != end && !getInstructionFromIndex(index)) 295 index += InstrSlots::NUM; 296 if (index == end) break; 297 298 MachineInstr *MI = getInstructionFromIndex(index); 299 unsigned SrcReg, DstReg; 300 if (tii_->isMoveInstr(*MI, SrcReg, DstReg)) 301 if (SrcReg == li.reg || DstReg == li.reg) 302 continue; 303 for (unsigned i = 0; i != MI->getNumOperands(); ++i) { 304 MachineOperand& mop = MI->getOperand(i); 305 if (!mop.isRegister()) 306 continue; 307 unsigned PhysReg = mop.getReg(); 308 if (PhysReg == 0 || PhysReg == li.reg) 309 continue; 310 if (TargetRegisterInfo::isVirtualRegister(PhysReg)) { 311 if (!vrm.hasPhys(PhysReg)) 312 continue; 313 PhysReg = vrm.getPhys(PhysReg); 314 } 315 if (PhysReg && tri_->regsOverlap(PhysReg, reg)) 316 return true; 317 } 318 } 319 } 320 321 return false; 322} 323 324void LiveIntervals::printRegName(unsigned reg) const { 325 if (TargetRegisterInfo::isPhysicalRegister(reg)) 326 cerr << tri_->getName(reg); 327 else 328 cerr << "%reg" << reg; 329} 330 331void LiveIntervals::handleVirtualRegisterDef(MachineBasicBlock *mbb, 332 MachineBasicBlock::iterator mi, 333 unsigned MIIdx, MachineOperand& MO, 334 unsigned MOIdx, 335 LiveInterval &interval) { 336 DOUT << "\t\tregister: "; DEBUG(printRegName(interval.reg)); 337 LiveVariables::VarInfo& vi = lv_->getVarInfo(interval.reg); 338 339 if (mi->getOpcode() == TargetInstrInfo::IMPLICIT_DEF) { 340 DOUT << "is a implicit_def\n"; 341 return; 342 } 343 344 // Virtual registers may be defined multiple times (due to phi 345 // elimination and 2-addr elimination). Much of what we do only has to be 346 // done once for the vreg. We use an empty interval to detect the first 347 // time we see a vreg. 348 if (interval.empty()) { 349 // Get the Idx of the defining instructions. 350 unsigned defIndex = getDefIndex(MIIdx); 351 VNInfo *ValNo; 352 MachineInstr *CopyMI = NULL; 353 unsigned SrcReg, DstReg; 354 if (mi->getOpcode() == TargetInstrInfo::EXTRACT_SUBREG || 355 mi->getOpcode() == TargetInstrInfo::INSERT_SUBREG || 356 tii_->isMoveInstr(*mi, SrcReg, DstReg)) 357 CopyMI = mi; 358 ValNo = interval.getNextValue(defIndex, CopyMI, VNInfoAllocator); 359 360 assert(ValNo->id == 0 && "First value in interval is not 0?"); 361 362 // Loop over all of the blocks that the vreg is defined in. There are 363 // two cases we have to handle here. The most common case is a vreg 364 // whose lifetime is contained within a basic block. In this case there 365 // will be a single kill, in MBB, which comes after the definition. 366 if (vi.Kills.size() == 1 && vi.Kills[0]->getParent() == mbb) { 367 // FIXME: what about dead vars? 368 unsigned killIdx; 369 if (vi.Kills[0] != mi) 370 killIdx = getUseIndex(getInstructionIndex(vi.Kills[0]))+1; 371 else 372 killIdx = defIndex+1; 373 374 // If the kill happens after the definition, we have an intra-block 375 // live range. 376 if (killIdx > defIndex) { 377 assert(vi.AliveBlocks.none() && 378 "Shouldn't be alive across any blocks!"); 379 LiveRange LR(defIndex, killIdx, ValNo); 380 interval.addRange(LR); 381 DOUT << " +" << LR << "\n"; 382 interval.addKill(ValNo, killIdx); 383 return; 384 } 385 } 386 387 // The other case we handle is when a virtual register lives to the end 388 // of the defining block, potentially live across some blocks, then is 389 // live into some number of blocks, but gets killed. Start by adding a 390 // range that goes from this definition to the end of the defining block. 391 LiveRange NewLR(defIndex, getMBBEndIdx(mbb)+1, ValNo); 392 DOUT << " +" << NewLR; 393 interval.addRange(NewLR); 394 395 // Iterate over all of the blocks that the variable is completely 396 // live in, adding [insrtIndex(begin), instrIndex(end)+4) to the 397 // live interval. 398 for (unsigned i = 0, e = vi.AliveBlocks.size(); i != e; ++i) { 399 if (vi.AliveBlocks[i]) { 400 LiveRange LR(getMBBStartIdx(i), 401 getMBBEndIdx(i)+1, // MBB ends at -1. 402 ValNo); 403 interval.addRange(LR); 404 DOUT << " +" << LR; 405 } 406 } 407 408 // Finally, this virtual register is live from the start of any killing 409 // block to the 'use' slot of the killing instruction. 410 for (unsigned i = 0, e = vi.Kills.size(); i != e; ++i) { 411 MachineInstr *Kill = vi.Kills[i]; 412 unsigned killIdx = getUseIndex(getInstructionIndex(Kill))+1; 413 LiveRange LR(getMBBStartIdx(Kill->getParent()), 414 killIdx, ValNo); 415 interval.addRange(LR); 416 interval.addKill(ValNo, killIdx); 417 DOUT << " +" << LR; 418 } 419 420 } else { 421 // If this is the second time we see a virtual register definition, it 422 // must be due to phi elimination or two addr elimination. If this is 423 // the result of two address elimination, then the vreg is one of the 424 // def-and-use register operand. 425 if (mi->isRegReDefinedByTwoAddr(interval.reg, MOIdx)) { 426 // If this is a two-address definition, then we have already processed 427 // the live range. The only problem is that we didn't realize there 428 // are actually two values in the live interval. Because of this we 429 // need to take the LiveRegion that defines this register and split it 430 // into two values. 431 assert(interval.containsOneValue()); 432 unsigned DefIndex = getDefIndex(interval.getValNumInfo(0)->def); 433 unsigned RedefIndex = getDefIndex(MIIdx); 434 435 const LiveRange *OldLR = interval.getLiveRangeContaining(RedefIndex-1); 436 VNInfo *OldValNo = OldLR->valno; 437 438 // Delete the initial value, which should be short and continuous, 439 // because the 2-addr copy must be in the same MBB as the redef. 440 interval.removeRange(DefIndex, RedefIndex); 441 442 // Two-address vregs should always only be redefined once. This means 443 // that at this point, there should be exactly one value number in it. 444 assert(interval.containsOneValue() && "Unexpected 2-addr liveint!"); 445 446 // The new value number (#1) is defined by the instruction we claimed 447 // defined value #0. 448 VNInfo *ValNo = interval.getNextValue(OldValNo->def, OldValNo->copy, 449 VNInfoAllocator); 450 451 // Value#0 is now defined by the 2-addr instruction. 452 OldValNo->def = RedefIndex; 453 OldValNo->copy = 0; 454 455 // Add the new live interval which replaces the range for the input copy. 456 LiveRange LR(DefIndex, RedefIndex, ValNo); 457 DOUT << " replace range with " << LR; 458 interval.addRange(LR); 459 interval.addKill(ValNo, RedefIndex); 460 461 // If this redefinition is dead, we need to add a dummy unit live 462 // range covering the def slot. 463 if (MO.isDead()) 464 interval.addRange(LiveRange(RedefIndex, RedefIndex+1, OldValNo)); 465 466 DOUT << " RESULT: "; 467 interval.print(DOUT, tri_); 468 469 } else { 470 // Otherwise, this must be because of phi elimination. If this is the 471 // first redefinition of the vreg that we have seen, go back and change 472 // the live range in the PHI block to be a different value number. 473 if (interval.containsOneValue()) { 474 assert(vi.Kills.size() == 1 && 475 "PHI elimination vreg should have one kill, the PHI itself!"); 476 477 // Remove the old range that we now know has an incorrect number. 478 VNInfo *VNI = interval.getValNumInfo(0); 479 MachineInstr *Killer = vi.Kills[0]; 480 unsigned Start = getMBBStartIdx(Killer->getParent()); 481 unsigned End = getUseIndex(getInstructionIndex(Killer))+1; 482 DOUT << " Removing [" << Start << "," << End << "] from: "; 483 interval.print(DOUT, tri_); DOUT << "\n"; 484 interval.removeRange(Start, End); 485 VNI->hasPHIKill = true; 486 DOUT << " RESULT: "; interval.print(DOUT, tri_); 487 488 // Replace the interval with one of a NEW value number. Note that this 489 // value number isn't actually defined by an instruction, weird huh? :) 490 LiveRange LR(Start, End, interval.getNextValue(~0, 0, VNInfoAllocator)); 491 DOUT << " replace range with " << LR; 492 interval.addRange(LR); 493 interval.addKill(LR.valno, End); 494 DOUT << " RESULT: "; interval.print(DOUT, tri_); 495 } 496 497 // In the case of PHI elimination, each variable definition is only 498 // live until the end of the block. We've already taken care of the 499 // rest of the live range. 500 unsigned defIndex = getDefIndex(MIIdx); 501 502 VNInfo *ValNo; 503 MachineInstr *CopyMI = NULL; 504 unsigned SrcReg, DstReg; 505 if (mi->getOpcode() == TargetInstrInfo::EXTRACT_SUBREG || 506 mi->getOpcode() == TargetInstrInfo::INSERT_SUBREG || 507 tii_->isMoveInstr(*mi, SrcReg, DstReg)) 508 CopyMI = mi; 509 ValNo = interval.getNextValue(defIndex, CopyMI, VNInfoAllocator); 510 511 unsigned killIndex = getMBBEndIdx(mbb) + 1; 512 LiveRange LR(defIndex, killIndex, ValNo); 513 interval.addRange(LR); 514 interval.addKill(ValNo, killIndex); 515 ValNo->hasPHIKill = true; 516 DOUT << " +" << LR; 517 } 518 } 519 520 DOUT << '\n'; 521} 522 523void LiveIntervals::handlePhysicalRegisterDef(MachineBasicBlock *MBB, 524 MachineBasicBlock::iterator mi, 525 unsigned MIIdx, 526 MachineOperand& MO, 527 LiveInterval &interval, 528 MachineInstr *CopyMI) { 529 // A physical register cannot be live across basic block, so its 530 // lifetime must end somewhere in its defining basic block. 531 DOUT << "\t\tregister: "; DEBUG(printRegName(interval.reg)); 532 533 unsigned baseIndex = MIIdx; 534 unsigned start = getDefIndex(baseIndex); 535 unsigned end = start; 536 537 // If it is not used after definition, it is considered dead at 538 // the instruction defining it. Hence its interval is: 539 // [defSlot(def), defSlot(def)+1) 540 if (MO.isDead()) { 541 DOUT << " dead"; 542 end = getDefIndex(start) + 1; 543 goto exit; 544 } 545 546 // If it is not dead on definition, it must be killed by a 547 // subsequent instruction. Hence its interval is: 548 // [defSlot(def), useSlot(kill)+1) 549 baseIndex += InstrSlots::NUM; 550 while (++mi != MBB->end()) { 551 while (baseIndex / InstrSlots::NUM < i2miMap_.size() && 552 getInstructionFromIndex(baseIndex) == 0) 553 baseIndex += InstrSlots::NUM; 554 if (mi->killsRegister(interval.reg, tri_)) { 555 DOUT << " killed"; 556 end = getUseIndex(baseIndex) + 1; 557 goto exit; 558 } else if (mi->modifiesRegister(interval.reg, tri_)) { 559 // Another instruction redefines the register before it is ever read. 560 // Then the register is essentially dead at the instruction that defines 561 // it. Hence its interval is: 562 // [defSlot(def), defSlot(def)+1) 563 DOUT << " dead"; 564 end = getDefIndex(start) + 1; 565 goto exit; 566 } 567 568 baseIndex += InstrSlots::NUM; 569 } 570 571 // The only case we should have a dead physreg here without a killing or 572 // instruction where we know it's dead is if it is live-in to the function 573 // and never used. 574 assert(!CopyMI && "physreg was not killed in defining block!"); 575 end = getDefIndex(start) + 1; // It's dead. 576 577exit: 578 assert(start < end && "did not find end of interval?"); 579 580 // Already exists? Extend old live interval. 581 LiveInterval::iterator OldLR = interval.FindLiveRangeContaining(start); 582 VNInfo *ValNo = (OldLR != interval.end()) 583 ? OldLR->valno : interval.getNextValue(start, CopyMI, VNInfoAllocator); 584 LiveRange LR(start, end, ValNo); 585 interval.addRange(LR); 586 interval.addKill(LR.valno, end); 587 DOUT << " +" << LR << '\n'; 588} 589 590void LiveIntervals::handleRegisterDef(MachineBasicBlock *MBB, 591 MachineBasicBlock::iterator MI, 592 unsigned MIIdx, 593 MachineOperand& MO, 594 unsigned MOIdx) { 595 if (TargetRegisterInfo::isVirtualRegister(MO.getReg())) 596 handleVirtualRegisterDef(MBB, MI, MIIdx, MO, MOIdx, 597 getOrCreateInterval(MO.getReg())); 598 else if (allocatableRegs_[MO.getReg()]) { 599 MachineInstr *CopyMI = NULL; 600 unsigned SrcReg, DstReg; 601 if (MI->getOpcode() == TargetInstrInfo::EXTRACT_SUBREG || 602 MI->getOpcode() == TargetInstrInfo::INSERT_SUBREG || 603 tii_->isMoveInstr(*MI, SrcReg, DstReg)) 604 CopyMI = MI; 605 handlePhysicalRegisterDef(MBB, MI, MIIdx, MO, 606 getOrCreateInterval(MO.getReg()), CopyMI); 607 // Def of a register also defines its sub-registers. 608 for (const unsigned* AS = tri_->getSubRegisters(MO.getReg()); *AS; ++AS) 609 // If MI also modifies the sub-register explicitly, avoid processing it 610 // more than once. Do not pass in TRI here so it checks for exact match. 611 if (!MI->modifiesRegister(*AS)) 612 handlePhysicalRegisterDef(MBB, MI, MIIdx, MO, 613 getOrCreateInterval(*AS), 0); 614 } 615} 616 617void LiveIntervals::handleLiveInRegister(MachineBasicBlock *MBB, 618 unsigned MIIdx, 619 LiveInterval &interval, bool isAlias) { 620 DOUT << "\t\tlivein register: "; DEBUG(printRegName(interval.reg)); 621 622 // Look for kills, if it reaches a def before it's killed, then it shouldn't 623 // be considered a livein. 624 MachineBasicBlock::iterator mi = MBB->begin(); 625 unsigned baseIndex = MIIdx; 626 unsigned start = baseIndex; 627 unsigned end = start; 628 while (mi != MBB->end()) { 629 if (mi->killsRegister(interval.reg, tri_)) { 630 DOUT << " killed"; 631 end = getUseIndex(baseIndex) + 1; 632 goto exit; 633 } else if (mi->modifiesRegister(interval.reg, tri_)) { 634 // Another instruction redefines the register before it is ever read. 635 // Then the register is essentially dead at the instruction that defines 636 // it. Hence its interval is: 637 // [defSlot(def), defSlot(def)+1) 638 DOUT << " dead"; 639 end = getDefIndex(start) + 1; 640 goto exit; 641 } 642 643 baseIndex += InstrSlots::NUM; 644 while (baseIndex / InstrSlots::NUM < i2miMap_.size() && 645 getInstructionFromIndex(baseIndex) == 0) 646 baseIndex += InstrSlots::NUM; 647 ++mi; 648 } 649 650exit: 651 // Live-in register might not be used at all. 652 if (end == MIIdx) { 653 if (isAlias) { 654 DOUT << " dead"; 655 end = getDefIndex(MIIdx) + 1; 656 } else { 657 DOUT << " live through"; 658 end = baseIndex; 659 } 660 } 661 662 LiveRange LR(start, end, interval.getNextValue(start, 0, VNInfoAllocator)); 663 interval.addRange(LR); 664 interval.addKill(LR.valno, end); 665 DOUT << " +" << LR << '\n'; 666} 667 668/// computeIntervals - computes the live intervals for virtual 669/// registers. for some ordering of the machine instructions [1,N] a 670/// live interval is an interval [i, j) where 1 <= i <= j < N for 671/// which a variable is live 672void LiveIntervals::computeIntervals() { 673 DOUT << "********** COMPUTING LIVE INTERVALS **********\n" 674 << "********** Function: " 675 << ((Value*)mf_->getFunction())->getName() << '\n'; 676 // Track the index of the current machine instr. 677 unsigned MIIndex = 0; 678 679 // Skip over empty initial indices. 680 while (MIIndex / InstrSlots::NUM < i2miMap_.size() && 681 getInstructionFromIndex(MIIndex) == 0) 682 MIIndex += InstrSlots::NUM; 683 684 for (MachineFunction::iterator MBBI = mf_->begin(), E = mf_->end(); 685 MBBI != E; ++MBBI) { 686 MachineBasicBlock *MBB = MBBI; 687 DOUT << ((Value*)MBB->getBasicBlock())->getName() << ":\n"; 688 689 MachineBasicBlock::iterator MI = MBB->begin(), miEnd = MBB->end(); 690 691 // Create intervals for live-ins to this BB first. 692 for (MachineBasicBlock::const_livein_iterator LI = MBB->livein_begin(), 693 LE = MBB->livein_end(); LI != LE; ++LI) { 694 handleLiveInRegister(MBB, MIIndex, getOrCreateInterval(*LI)); 695 // Multiple live-ins can alias the same register. 696 for (const unsigned* AS = tri_->getSubRegisters(*LI); *AS; ++AS) 697 if (!hasInterval(*AS)) 698 handleLiveInRegister(MBB, MIIndex, getOrCreateInterval(*AS), 699 true); 700 } 701 702 for (; MI != miEnd; ++MI) { 703 DOUT << MIIndex << "\t" << *MI; 704 705 // Handle defs. 706 for (int i = MI->getNumOperands() - 1; i >= 0; --i) { 707 MachineOperand &MO = MI->getOperand(i); 708 // handle register defs - build intervals 709 if (MO.isRegister() && MO.getReg() && MO.isDef()) 710 handleRegisterDef(MBB, MI, MIIndex, MO, i); 711 } 712 713 MIIndex += InstrSlots::NUM; 714 715 // Skip over empty indices. 716 while (MIIndex / InstrSlots::NUM < i2miMap_.size() && 717 getInstructionFromIndex(MIIndex) == 0) 718 MIIndex += InstrSlots::NUM; 719 } 720 } 721} 722 723bool LiveIntervals::findLiveInMBBs(const LiveRange &LR, 724 SmallVectorImpl<MachineBasicBlock*> &MBBs) const { 725 std::vector<IdxMBBPair>::const_iterator I = 726 std::lower_bound(Idx2MBBMap.begin(), Idx2MBBMap.end(), LR.start); 727 728 bool ResVal = false; 729 while (I != Idx2MBBMap.end()) { 730 if (LR.end <= I->first) 731 break; 732 MBBs.push_back(I->second); 733 ResVal = true; 734 ++I; 735 } 736 return ResVal; 737} 738 739 740LiveInterval* LiveIntervals::createInterval(unsigned reg) { 741 float Weight = TargetRegisterInfo::isPhysicalRegister(reg) ? 742 HUGE_VALF : 0.0F; 743 return new LiveInterval(reg, Weight); 744} 745 746/// getVNInfoSourceReg - Helper function that parses the specified VNInfo 747/// copy field and returns the source register that defines it. 748unsigned LiveIntervals::getVNInfoSourceReg(const VNInfo *VNI) const { 749 if (!VNI->copy) 750 return 0; 751 752 if (VNI->copy->getOpcode() == TargetInstrInfo::EXTRACT_SUBREG) 753 return VNI->copy->getOperand(1).getReg(); 754 if (VNI->copy->getOpcode() == TargetInstrInfo::INSERT_SUBREG) 755 return VNI->copy->getOperand(2).getReg(); 756 unsigned SrcReg, DstReg; 757 if (tii_->isMoveInstr(*VNI->copy, SrcReg, DstReg)) 758 return SrcReg; 759 assert(0 && "Unrecognized copy instruction!"); 760 return 0; 761} 762 763//===----------------------------------------------------------------------===// 764// Register allocator hooks. 765// 766 767/// getReMatImplicitUse - If the remat definition MI has one (for now, we only 768/// allow one) virtual register operand, then its uses are implicitly using 769/// the register. Returns the virtual register. 770unsigned LiveIntervals::getReMatImplicitUse(const LiveInterval &li, 771 MachineInstr *MI) const { 772 unsigned RegOp = 0; 773 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { 774 MachineOperand &MO = MI->getOperand(i); 775 if (!MO.isRegister() || !MO.isUse()) 776 continue; 777 unsigned Reg = MO.getReg(); 778 if (Reg == 0 || Reg == li.reg) 779 continue; 780 // FIXME: For now, only remat MI with at most one register operand. 781 assert(!RegOp && 782 "Can't rematerialize instruction with multiple register operand!"); 783 RegOp = MO.getReg(); 784#ifndef NDEBUG 785 break; 786#endif 787 } 788 return RegOp; 789} 790 791/// isValNoAvailableAt - Return true if the val# of the specified interval 792/// which reaches the given instruction also reaches the specified use index. 793bool LiveIntervals::isValNoAvailableAt(const LiveInterval &li, MachineInstr *MI, 794 unsigned UseIdx) const { 795 unsigned Index = getInstructionIndex(MI); 796 VNInfo *ValNo = li.FindLiveRangeContaining(Index)->valno; 797 LiveInterval::const_iterator UI = li.FindLiveRangeContaining(UseIdx); 798 return UI != li.end() && UI->valno == ValNo; 799} 800 801/// isReMaterializable - Returns true if the definition MI of the specified 802/// val# of the specified interval is re-materializable. 803bool LiveIntervals::isReMaterializable(const LiveInterval &li, 804 const VNInfo *ValNo, MachineInstr *MI, 805 bool &isLoad) { 806 if (DisableReMat) 807 return false; 808 809 if (MI->getOpcode() == TargetInstrInfo::IMPLICIT_DEF) 810 return true; 811 812 int FrameIdx = 0; 813 if (tii_->isLoadFromStackSlot(MI, FrameIdx) && 814 mf_->getFrameInfo()->isImmutableObjectIndex(FrameIdx)) 815 // FIXME: Let target specific isReallyTriviallyReMaterializable determines 816 // this but remember this is not safe to fold into a two-address 817 // instruction. 818 // This is a load from fixed stack slot. It can be rematerialized. 819 return true; 820 821 // If the target-specific rules don't identify an instruction as 822 // being trivially rematerializable, use some target-independent 823 // rules. 824 if (!MI->getDesc().isRematerializable() || 825 !tii_->isTriviallyReMaterializable(MI)) { 826 if (!EnableAggressiveRemat) 827 return false; 828 829 // If the instruction accesses memory but the memoperands have been lost, 830 // we can't analyze it. 831 const TargetInstrDesc &TID = MI->getDesc(); 832 if ((TID.mayLoad() || TID.mayStore()) && MI->memoperands_empty()) 833 return false; 834 835 // Avoid instructions obviously unsafe for remat. 836 if (TID.hasUnmodeledSideEffects() || TID.isNotDuplicable()) 837 return false; 838 839 // If the instruction accesses memory and the memory could be non-constant, 840 // assume the instruction is not rematerializable. 841 for (std::list<MachineMemOperand>::const_iterator I = MI->memoperands_begin(), 842 E = MI->memoperands_end(); I != E; ++I) { 843 const MachineMemOperand &MMO = *I; 844 if (MMO.isVolatile() || MMO.isStore()) 845 return false; 846 const Value *V = MMO.getValue(); 847 if (!V) 848 return false; 849 if (const PseudoSourceValue *PSV = dyn_cast<PseudoSourceValue>(V)) { 850 if (!PSV->isConstant(mf_->getFrameInfo())) 851 return false; 852 } else if (!aa_->pointsToConstantMemory(V)) 853 return false; 854 } 855 856 // If any of the registers accessed are non-constant, conservatively assume 857 // the instruction is not rematerializable. 858 unsigned ImpUse = 0; 859 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { 860 const MachineOperand &MO = MI->getOperand(i); 861 if (MO.isReg()) { 862 unsigned Reg = MO.getReg(); 863 if (Reg == 0) 864 continue; 865 if (TargetRegisterInfo::isPhysicalRegister(Reg)) 866 return false; 867 868 // Only allow one def, and that in the first operand. 869 if (MO.isDef() != (i == 0)) 870 return false; 871 872 // Only allow constant-valued registers. 873 bool IsLiveIn = mri_->isLiveIn(Reg); 874 MachineRegisterInfo::def_iterator I = mri_->def_begin(Reg), 875 E = mri_->def_end(); 876 877 // For the def, it should be the only def. 878 if (MO.isDef() && (next(I) != E || IsLiveIn)) 879 return false; 880 881 if (MO.isUse()) { 882 // Only allow one use other register use, as that's all the 883 // remat mechanisms support currently. 884 if (Reg != li.reg) { 885 if (ImpUse == 0) 886 ImpUse = Reg; 887 else if (Reg != ImpUse) 888 return false; 889 } 890 // For uses, there should be only one associate def. 891 if (I != E && (next(I) != E || IsLiveIn)) 892 return false; 893 } 894 } 895 } 896 } 897 898 unsigned ImpUse = getReMatImplicitUse(li, MI); 899 if (ImpUse) { 900 const LiveInterval &ImpLi = getInterval(ImpUse); 901 for (MachineRegisterInfo::use_iterator ri = mri_->use_begin(li.reg), 902 re = mri_->use_end(); ri != re; ++ri) { 903 MachineInstr *UseMI = &*ri; 904 unsigned UseIdx = getInstructionIndex(UseMI); 905 if (li.FindLiveRangeContaining(UseIdx)->valno != ValNo) 906 continue; 907 if (!isValNoAvailableAt(ImpLi, MI, UseIdx)) 908 return false; 909 } 910 } 911 return true; 912} 913 914/// isReMaterializable - Returns true if every definition of MI of every 915/// val# of the specified interval is re-materializable. 916bool LiveIntervals::isReMaterializable(const LiveInterval &li, bool &isLoad) { 917 isLoad = false; 918 for (LiveInterval::const_vni_iterator i = li.vni_begin(), e = li.vni_end(); 919 i != e; ++i) { 920 const VNInfo *VNI = *i; 921 unsigned DefIdx = VNI->def; 922 if (DefIdx == ~1U) 923 continue; // Dead val#. 924 // Is the def for the val# rematerializable? 925 if (DefIdx == ~0u) 926 return false; 927 MachineInstr *ReMatDefMI = getInstructionFromIndex(DefIdx); 928 bool DefIsLoad = false; 929 if (!ReMatDefMI || 930 !isReMaterializable(li, VNI, ReMatDefMI, DefIsLoad)) 931 return false; 932 isLoad |= DefIsLoad; 933 } 934 return true; 935} 936 937/// FilterFoldedOps - Filter out two-address use operands. Return 938/// true if it finds any issue with the operands that ought to prevent 939/// folding. 940static bool FilterFoldedOps(MachineInstr *MI, 941 SmallVector<unsigned, 2> &Ops, 942 unsigned &MRInfo, 943 SmallVector<unsigned, 2> &FoldOps) { 944 const TargetInstrDesc &TID = MI->getDesc(); 945 946 MRInfo = 0; 947 for (unsigned i = 0, e = Ops.size(); i != e; ++i) { 948 unsigned OpIdx = Ops[i]; 949 MachineOperand &MO = MI->getOperand(OpIdx); 950 // FIXME: fold subreg use. 951 if (MO.getSubReg()) 952 return true; 953 if (MO.isDef()) 954 MRInfo |= (unsigned)VirtRegMap::isMod; 955 else { 956 // Filter out two-address use operand(s). 957 if (!MO.isImplicit() && 958 TID.getOperandConstraint(OpIdx, TOI::TIED_TO) != -1) { 959 MRInfo = VirtRegMap::isModRef; 960 continue; 961 } 962 MRInfo |= (unsigned)VirtRegMap::isRef; 963 } 964 FoldOps.push_back(OpIdx); 965 } 966 return false; 967} 968 969 970/// tryFoldMemoryOperand - Attempts to fold either a spill / restore from 971/// slot / to reg or any rematerialized load into ith operand of specified 972/// MI. If it is successul, MI is updated with the newly created MI and 973/// returns true. 974bool LiveIntervals::tryFoldMemoryOperand(MachineInstr* &MI, 975 VirtRegMap &vrm, MachineInstr *DefMI, 976 unsigned InstrIdx, 977 SmallVector<unsigned, 2> &Ops, 978 bool isSS, int Slot, unsigned Reg) { 979 // If it is an implicit def instruction, just delete it. 980 if (MI->getOpcode() == TargetInstrInfo::IMPLICIT_DEF) { 981 RemoveMachineInstrFromMaps(MI); 982 vrm.RemoveMachineInstrFromMaps(MI); 983 MI->eraseFromParent(); 984 ++numFolds; 985 return true; 986 } 987 988 // Filter the list of operand indexes that are to be folded. Abort if 989 // any operand will prevent folding. 990 unsigned MRInfo = 0; 991 SmallVector<unsigned, 2> FoldOps; 992 if (FilterFoldedOps(MI, Ops, MRInfo, FoldOps)) 993 return false; 994 995 // The only time it's safe to fold into a two address instruction is when 996 // it's folding reload and spill from / into a spill stack slot. 997 if (DefMI && (MRInfo & VirtRegMap::isMod)) 998 return false; 999 1000 MachineInstr *fmi = isSS ? tii_->foldMemoryOperand(*mf_, MI, FoldOps, Slot) 1001 : tii_->foldMemoryOperand(*mf_, MI, FoldOps, DefMI); 1002 if (fmi) { 1003 // Remember this instruction uses the spill slot. 1004 if (isSS) vrm.addSpillSlotUse(Slot, fmi); 1005 1006 // Attempt to fold the memory reference into the instruction. If 1007 // we can do this, we don't need to insert spill code. 1008 MachineBasicBlock &MBB = *MI->getParent(); 1009 if (isSS && !mf_->getFrameInfo()->isImmutableObjectIndex(Slot)) 1010 vrm.virtFolded(Reg, MI, fmi, (VirtRegMap::ModRef)MRInfo); 1011 vrm.transferSpillPts(MI, fmi); 1012 vrm.transferRestorePts(MI, fmi); 1013 vrm.transferEmergencySpills(MI, fmi); 1014 mi2iMap_.erase(MI); 1015 i2miMap_[InstrIdx /InstrSlots::NUM] = fmi; 1016 mi2iMap_[fmi] = InstrIdx; 1017 MI = MBB.insert(MBB.erase(MI), fmi); 1018 ++numFolds; 1019 return true; 1020 } 1021 return false; 1022} 1023 1024/// canFoldMemoryOperand - Returns true if the specified load / store 1025/// folding is possible. 1026bool LiveIntervals::canFoldMemoryOperand(MachineInstr *MI, 1027 SmallVector<unsigned, 2> &Ops, 1028 bool ReMat) const { 1029 // Filter the list of operand indexes that are to be folded. Abort if 1030 // any operand will prevent folding. 1031 unsigned MRInfo = 0; 1032 SmallVector<unsigned, 2> FoldOps; 1033 if (FilterFoldedOps(MI, Ops, MRInfo, FoldOps)) 1034 return false; 1035 1036 // It's only legal to remat for a use, not a def. 1037 if (ReMat && (MRInfo & VirtRegMap::isMod)) 1038 return false; 1039 1040 return tii_->canFoldMemoryOperand(MI, FoldOps); 1041} 1042 1043bool LiveIntervals::intervalIsInOneMBB(const LiveInterval &li) const { 1044 SmallPtrSet<MachineBasicBlock*, 4> MBBs; 1045 for (LiveInterval::Ranges::const_iterator 1046 I = li.ranges.begin(), E = li.ranges.end(); I != E; ++I) { 1047 std::vector<IdxMBBPair>::const_iterator II = 1048 std::lower_bound(Idx2MBBMap.begin(), Idx2MBBMap.end(), I->start); 1049 if (II == Idx2MBBMap.end()) 1050 continue; 1051 if (I->end > II->first) // crossing a MBB. 1052 return false; 1053 MBBs.insert(II->second); 1054 if (MBBs.size() > 1) 1055 return false; 1056 } 1057 return true; 1058} 1059 1060/// rewriteImplicitOps - Rewrite implicit use operands of MI (i.e. uses of 1061/// interval on to-be re-materialized operands of MI) with new register. 1062void LiveIntervals::rewriteImplicitOps(const LiveInterval &li, 1063 MachineInstr *MI, unsigned NewVReg, 1064 VirtRegMap &vrm) { 1065 // There is an implicit use. That means one of the other operand is 1066 // being remat'ed and the remat'ed instruction has li.reg as an 1067 // use operand. Make sure we rewrite that as well. 1068 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { 1069 MachineOperand &MO = MI->getOperand(i); 1070 if (!MO.isRegister()) 1071 continue; 1072 unsigned Reg = MO.getReg(); 1073 if (Reg == 0 || TargetRegisterInfo::isPhysicalRegister(Reg)) 1074 continue; 1075 if (!vrm.isReMaterialized(Reg)) 1076 continue; 1077 MachineInstr *ReMatMI = vrm.getReMaterializedMI(Reg); 1078 MachineOperand *UseMO = ReMatMI->findRegisterUseOperand(li.reg); 1079 if (UseMO) 1080 UseMO->setReg(NewVReg); 1081 } 1082} 1083 1084/// rewriteInstructionForSpills, rewriteInstructionsForSpills - Helper functions 1085/// for addIntervalsForSpills to rewrite uses / defs for the given live range. 1086bool LiveIntervals:: 1087rewriteInstructionForSpills(const LiveInterval &li, const VNInfo *VNI, 1088 bool TrySplit, unsigned index, unsigned end, MachineInstr *MI, 1089 MachineInstr *ReMatOrigDefMI, MachineInstr *ReMatDefMI, 1090 unsigned Slot, int LdSlot, 1091 bool isLoad, bool isLoadSS, bool DefIsReMat, bool CanDelete, 1092 VirtRegMap &vrm, 1093 const TargetRegisterClass* rc, 1094 SmallVector<int, 4> &ReMatIds, 1095 const MachineLoopInfo *loopInfo, 1096 unsigned &NewVReg, unsigned ImpUse, bool &HasDef, bool &HasUse, 1097 DenseMap<unsigned,unsigned> &MBBVRegsMap, 1098 std::vector<LiveInterval*> &NewLIs, float &SSWeight) { 1099 MachineBasicBlock *MBB = MI->getParent(); 1100 unsigned loopDepth = loopInfo->getLoopDepth(MBB); 1101 bool CanFold = false; 1102 RestartInstruction: 1103 for (unsigned i = 0; i != MI->getNumOperands(); ++i) { 1104 MachineOperand& mop = MI->getOperand(i); 1105 if (!mop.isRegister()) 1106 continue; 1107 unsigned Reg = mop.getReg(); 1108 unsigned RegI = Reg; 1109 if (Reg == 0 || TargetRegisterInfo::isPhysicalRegister(Reg)) 1110 continue; 1111 if (Reg != li.reg) 1112 continue; 1113 1114 bool TryFold = !DefIsReMat; 1115 bool FoldSS = true; // Default behavior unless it's a remat. 1116 int FoldSlot = Slot; 1117 if (DefIsReMat) { 1118 // If this is the rematerializable definition MI itself and 1119 // all of its uses are rematerialized, simply delete it. 1120 if (MI == ReMatOrigDefMI && CanDelete) { 1121 DOUT << "\t\t\t\tErasing re-materlizable def: "; 1122 DOUT << MI << '\n'; 1123 RemoveMachineInstrFromMaps(MI); 1124 vrm.RemoveMachineInstrFromMaps(MI); 1125 MI->eraseFromParent(); 1126 break; 1127 } 1128 1129 // If def for this use can't be rematerialized, then try folding. 1130 // If def is rematerializable and it's a load, also try folding. 1131 TryFold = !ReMatDefMI || (ReMatDefMI && (MI == ReMatOrigDefMI || isLoad)); 1132 if (isLoad) { 1133 // Try fold loads (from stack slot, constant pool, etc.) into uses. 1134 FoldSS = isLoadSS; 1135 FoldSlot = LdSlot; 1136 } 1137 } 1138 1139 // Scan all of the operands of this instruction rewriting operands 1140 // to use NewVReg instead of li.reg as appropriate. We do this for 1141 // two reasons: 1142 // 1143 // 1. If the instr reads the same spilled vreg multiple times, we 1144 // want to reuse the NewVReg. 1145 // 2. If the instr is a two-addr instruction, we are required to 1146 // keep the src/dst regs pinned. 1147 // 1148 // Keep track of whether we replace a use and/or def so that we can 1149 // create the spill interval with the appropriate range. 1150 1151 HasUse = mop.isUse(); 1152 HasDef = mop.isDef(); 1153 SmallVector<unsigned, 2> Ops; 1154 Ops.push_back(i); 1155 for (unsigned j = i+1, e = MI->getNumOperands(); j != e; ++j) { 1156 const MachineOperand &MOj = MI->getOperand(j); 1157 if (!MOj.isRegister()) 1158 continue; 1159 unsigned RegJ = MOj.getReg(); 1160 if (RegJ == 0 || TargetRegisterInfo::isPhysicalRegister(RegJ)) 1161 continue; 1162 if (RegJ == RegI) { 1163 Ops.push_back(j); 1164 HasUse |= MOj.isUse(); 1165 HasDef |= MOj.isDef(); 1166 } 1167 } 1168 1169 if (HasUse && !li.liveAt(getUseIndex(index))) 1170 // Must be defined by an implicit def. It should not be spilled. Note, 1171 // this is for correctness reason. e.g. 1172 // 8 %reg1024<def> = IMPLICIT_DEF 1173 // 12 %reg1024<def> = INSERT_SUBREG %reg1024<kill>, %reg1025, 2 1174 // The live range [12, 14) are not part of the r1024 live interval since 1175 // it's defined by an implicit def. It will not conflicts with live 1176 // interval of r1025. Now suppose both registers are spilled, you can 1177 // easily see a situation where both registers are reloaded before 1178 // the INSERT_SUBREG and both target registers that would overlap. 1179 HasUse = false; 1180 1181 // Update stack slot spill weight if we are splitting. 1182 float Weight = getSpillWeight(HasDef, HasUse, loopDepth); 1183 if (!TrySplit) 1184 SSWeight += Weight; 1185 1186 if (!TryFold) 1187 CanFold = false; 1188 else { 1189 // Do not fold load / store here if we are splitting. We'll find an 1190 // optimal point to insert a load / store later. 1191 if (!TrySplit) { 1192 if (tryFoldMemoryOperand(MI, vrm, ReMatDefMI, index, 1193 Ops, FoldSS, FoldSlot, Reg)) { 1194 // Folding the load/store can completely change the instruction in 1195 // unpredictable ways, rescan it from the beginning. 1196 HasUse = false; 1197 HasDef = false; 1198 CanFold = false; 1199 if (isRemoved(MI)) { 1200 SSWeight -= Weight; 1201 break; 1202 } 1203 goto RestartInstruction; 1204 } 1205 } else { 1206 // We'll try to fold it later if it's profitable. 1207 CanFold = canFoldMemoryOperand(MI, Ops, DefIsReMat); 1208 } 1209 } 1210 1211 // Create a new virtual register for the spill interval. 1212 bool CreatedNewVReg = false; 1213 if (NewVReg == 0) { 1214 NewVReg = mri_->createVirtualRegister(rc); 1215 vrm.grow(); 1216 CreatedNewVReg = true; 1217 } 1218 mop.setReg(NewVReg); 1219 if (mop.isImplicit()) 1220 rewriteImplicitOps(li, MI, NewVReg, vrm); 1221 1222 // Reuse NewVReg for other reads. 1223 for (unsigned j = 0, e = Ops.size(); j != e; ++j) { 1224 MachineOperand &mopj = MI->getOperand(Ops[j]); 1225 mopj.setReg(NewVReg); 1226 if (mopj.isImplicit()) 1227 rewriteImplicitOps(li, MI, NewVReg, vrm); 1228 } 1229 1230 if (CreatedNewVReg) { 1231 if (DefIsReMat) { 1232 vrm.setVirtIsReMaterialized(NewVReg, ReMatDefMI/*, CanDelete*/); 1233 if (ReMatIds[VNI->id] == VirtRegMap::MAX_STACK_SLOT) { 1234 // Each valnum may have its own remat id. 1235 ReMatIds[VNI->id] = vrm.assignVirtReMatId(NewVReg); 1236 } else { 1237 vrm.assignVirtReMatId(NewVReg, ReMatIds[VNI->id]); 1238 } 1239 if (!CanDelete || (HasUse && HasDef)) { 1240 // If this is a two-addr instruction then its use operands are 1241 // rematerializable but its def is not. It should be assigned a 1242 // stack slot. 1243 vrm.assignVirt2StackSlot(NewVReg, Slot); 1244 } 1245 } else { 1246 vrm.assignVirt2StackSlot(NewVReg, Slot); 1247 } 1248 } else if (HasUse && HasDef && 1249 vrm.getStackSlot(NewVReg) == VirtRegMap::NO_STACK_SLOT) { 1250 // If this interval hasn't been assigned a stack slot (because earlier 1251 // def is a deleted remat def), do it now. 1252 assert(Slot != VirtRegMap::NO_STACK_SLOT); 1253 vrm.assignVirt2StackSlot(NewVReg, Slot); 1254 } 1255 1256 // Re-matting an instruction with virtual register use. Add the 1257 // register as an implicit use on the use MI. 1258 if (DefIsReMat && ImpUse) 1259 MI->addOperand(MachineOperand::CreateReg(ImpUse, false, true)); 1260 1261 // create a new register interval for this spill / remat. 1262 LiveInterval &nI = getOrCreateInterval(NewVReg); 1263 if (CreatedNewVReg) { 1264 NewLIs.push_back(&nI); 1265 MBBVRegsMap.insert(std::make_pair(MI->getParent()->getNumber(), NewVReg)); 1266 if (TrySplit) 1267 vrm.setIsSplitFromReg(NewVReg, li.reg); 1268 } 1269 1270 if (HasUse) { 1271 if (CreatedNewVReg) { 1272 LiveRange LR(getLoadIndex(index), getUseIndex(index)+1, 1273 nI.getNextValue(~0U, 0, VNInfoAllocator)); 1274 DOUT << " +" << LR; 1275 nI.addRange(LR); 1276 } else { 1277 // Extend the split live interval to this def / use. 1278 unsigned End = getUseIndex(index)+1; 1279 LiveRange LR(nI.ranges[nI.ranges.size()-1].end, End, 1280 nI.getValNumInfo(nI.getNumValNums()-1)); 1281 DOUT << " +" << LR; 1282 nI.addRange(LR); 1283 } 1284 } 1285 if (HasDef) { 1286 LiveRange LR(getDefIndex(index), getStoreIndex(index), 1287 nI.getNextValue(~0U, 0, VNInfoAllocator)); 1288 DOUT << " +" << LR; 1289 nI.addRange(LR); 1290 } 1291 1292 DOUT << "\t\t\t\tAdded new interval: "; 1293 nI.print(DOUT, tri_); 1294 DOUT << '\n'; 1295 } 1296 return CanFold; 1297} 1298bool LiveIntervals::anyKillInMBBAfterIdx(const LiveInterval &li, 1299 const VNInfo *VNI, 1300 MachineBasicBlock *MBB, unsigned Idx) const { 1301 unsigned End = getMBBEndIdx(MBB); 1302 for (unsigned j = 0, ee = VNI->kills.size(); j != ee; ++j) { 1303 unsigned KillIdx = VNI->kills[j]; 1304 if (KillIdx > Idx && KillIdx < End) 1305 return true; 1306 } 1307 return false; 1308} 1309 1310/// RewriteInfo - Keep track of machine instrs that will be rewritten 1311/// during spilling. 1312namespace { 1313 struct RewriteInfo { 1314 unsigned Index; 1315 MachineInstr *MI; 1316 bool HasUse; 1317 bool HasDef; 1318 RewriteInfo(unsigned i, MachineInstr *mi, bool u, bool d) 1319 : Index(i), MI(mi), HasUse(u), HasDef(d) {} 1320 }; 1321 1322 struct RewriteInfoCompare { 1323 bool operator()(const RewriteInfo &LHS, const RewriteInfo &RHS) const { 1324 return LHS.Index < RHS.Index; 1325 } 1326 }; 1327} 1328 1329void LiveIntervals:: 1330rewriteInstructionsForSpills(const LiveInterval &li, bool TrySplit, 1331 LiveInterval::Ranges::const_iterator &I, 1332 MachineInstr *ReMatOrigDefMI, MachineInstr *ReMatDefMI, 1333 unsigned Slot, int LdSlot, 1334 bool isLoad, bool isLoadSS, bool DefIsReMat, bool CanDelete, 1335 VirtRegMap &vrm, 1336 const TargetRegisterClass* rc, 1337 SmallVector<int, 4> &ReMatIds, 1338 const MachineLoopInfo *loopInfo, 1339 BitVector &SpillMBBs, 1340 DenseMap<unsigned, std::vector<SRInfo> > &SpillIdxes, 1341 BitVector &RestoreMBBs, 1342 DenseMap<unsigned, std::vector<SRInfo> > &RestoreIdxes, 1343 DenseMap<unsigned,unsigned> &MBBVRegsMap, 1344 std::vector<LiveInterval*> &NewLIs, float &SSWeight) { 1345 bool AllCanFold = true; 1346 unsigned NewVReg = 0; 1347 unsigned start = getBaseIndex(I->start); 1348 unsigned end = getBaseIndex(I->end-1) + InstrSlots::NUM; 1349 1350 // First collect all the def / use in this live range that will be rewritten. 1351 // Make sure they are sorted according to instruction index. 1352 std::vector<RewriteInfo> RewriteMIs; 1353 for (MachineRegisterInfo::reg_iterator ri = mri_->reg_begin(li.reg), 1354 re = mri_->reg_end(); ri != re; ) { 1355 MachineInstr *MI = &*ri; 1356 MachineOperand &O = ri.getOperand(); 1357 ++ri; 1358 assert(!O.isImplicit() && "Spilling register that's used as implicit use?"); 1359 unsigned index = getInstructionIndex(MI); 1360 if (index < start || index >= end) 1361 continue; 1362 if (O.isUse() && !li.liveAt(getUseIndex(index))) 1363 // Must be defined by an implicit def. It should not be spilled. Note, 1364 // this is for correctness reason. e.g. 1365 // 8 %reg1024<def> = IMPLICIT_DEF 1366 // 12 %reg1024<def> = INSERT_SUBREG %reg1024<kill>, %reg1025, 2 1367 // The live range [12, 14) are not part of the r1024 live interval since 1368 // it's defined by an implicit def. It will not conflicts with live 1369 // interval of r1025. Now suppose both registers are spilled, you can 1370 // easily see a situation where both registers are reloaded before 1371 // the INSERT_SUBREG and both target registers that would overlap. 1372 continue; 1373 RewriteMIs.push_back(RewriteInfo(index, MI, O.isUse(), O.isDef())); 1374 } 1375 std::sort(RewriteMIs.begin(), RewriteMIs.end(), RewriteInfoCompare()); 1376 1377 unsigned ImpUse = DefIsReMat ? getReMatImplicitUse(li, ReMatDefMI) : 0; 1378 // Now rewrite the defs and uses. 1379 for (unsigned i = 0, e = RewriteMIs.size(); i != e; ) { 1380 RewriteInfo &rwi = RewriteMIs[i]; 1381 ++i; 1382 unsigned index = rwi.Index; 1383 bool MIHasUse = rwi.HasUse; 1384 bool MIHasDef = rwi.HasDef; 1385 MachineInstr *MI = rwi.MI; 1386 // If MI def and/or use the same register multiple times, then there 1387 // are multiple entries. 1388 unsigned NumUses = MIHasUse; 1389 while (i != e && RewriteMIs[i].MI == MI) { 1390 assert(RewriteMIs[i].Index == index); 1391 bool isUse = RewriteMIs[i].HasUse; 1392 if (isUse) ++NumUses; 1393 MIHasUse |= isUse; 1394 MIHasDef |= RewriteMIs[i].HasDef; 1395 ++i; 1396 } 1397 MachineBasicBlock *MBB = MI->getParent(); 1398 1399 if (ImpUse && MI != ReMatDefMI) { 1400 // Re-matting an instruction with virtual register use. Update the 1401 // register interval's spill weight to HUGE_VALF to prevent it from 1402 // being spilled. 1403 LiveInterval &ImpLi = getInterval(ImpUse); 1404 ImpLi.weight = HUGE_VALF; 1405 } 1406 1407 unsigned MBBId = MBB->getNumber(); 1408 unsigned ThisVReg = 0; 1409 if (TrySplit) { 1410 DenseMap<unsigned,unsigned>::iterator NVI = MBBVRegsMap.find(MBBId); 1411 if (NVI != MBBVRegsMap.end()) { 1412 ThisVReg = NVI->second; 1413 // One common case: 1414 // x = use 1415 // ... 1416 // ... 1417 // def = ... 1418 // = use 1419 // It's better to start a new interval to avoid artifically 1420 // extend the new interval. 1421 if (MIHasDef && !MIHasUse) { 1422 MBBVRegsMap.erase(MBB->getNumber()); 1423 ThisVReg = 0; 1424 } 1425 } 1426 } 1427 1428 bool IsNew = ThisVReg == 0; 1429 if (IsNew) { 1430 // This ends the previous live interval. If all of its def / use 1431 // can be folded, give it a low spill weight. 1432 if (NewVReg && TrySplit && AllCanFold) { 1433 LiveInterval &nI = getOrCreateInterval(NewVReg); 1434 nI.weight /= 10.0F; 1435 } 1436 AllCanFold = true; 1437 } 1438 NewVReg = ThisVReg; 1439 1440 bool HasDef = false; 1441 bool HasUse = false; 1442 bool CanFold = rewriteInstructionForSpills(li, I->valno, TrySplit, 1443 index, end, MI, ReMatOrigDefMI, ReMatDefMI, 1444 Slot, LdSlot, isLoad, isLoadSS, DefIsReMat, 1445 CanDelete, vrm, rc, ReMatIds, loopInfo, NewVReg, 1446 ImpUse, HasDef, HasUse, MBBVRegsMap, NewLIs, SSWeight); 1447 if (!HasDef && !HasUse) 1448 continue; 1449 1450 AllCanFold &= CanFold; 1451 1452 // Update weight of spill interval. 1453 LiveInterval &nI = getOrCreateInterval(NewVReg); 1454 if (!TrySplit) { 1455 // The spill weight is now infinity as it cannot be spilled again. 1456 nI.weight = HUGE_VALF; 1457 continue; 1458 } 1459 1460 // Keep track of the last def and first use in each MBB. 1461 if (HasDef) { 1462 if (MI != ReMatOrigDefMI || !CanDelete) { 1463 bool HasKill = false; 1464 if (!HasUse) 1465 HasKill = anyKillInMBBAfterIdx(li, I->valno, MBB, getDefIndex(index)); 1466 else { 1467 // If this is a two-address code, then this index starts a new VNInfo. 1468 const VNInfo *VNI = li.findDefinedVNInfo(getDefIndex(index)); 1469 if (VNI) 1470 HasKill = anyKillInMBBAfterIdx(li, VNI, MBB, getDefIndex(index)); 1471 } 1472 DenseMap<unsigned, std::vector<SRInfo> >::iterator SII = 1473 SpillIdxes.find(MBBId); 1474 if (!HasKill) { 1475 if (SII == SpillIdxes.end()) { 1476 std::vector<SRInfo> S; 1477 S.push_back(SRInfo(index, NewVReg, true)); 1478 SpillIdxes.insert(std::make_pair(MBBId, S)); 1479 } else if (SII->second.back().vreg != NewVReg) { 1480 SII->second.push_back(SRInfo(index, NewVReg, true)); 1481 } else if ((int)index > SII->second.back().index) { 1482 // If there is an earlier def and this is a two-address 1483 // instruction, then it's not possible to fold the store (which 1484 // would also fold the load). 1485 SRInfo &Info = SII->second.back(); 1486 Info.index = index; 1487 Info.canFold = !HasUse; 1488 } 1489 SpillMBBs.set(MBBId); 1490 } else if (SII != SpillIdxes.end() && 1491 SII->second.back().vreg == NewVReg && 1492 (int)index > SII->second.back().index) { 1493 // There is an earlier def that's not killed (must be two-address). 1494 // The spill is no longer needed. 1495 SII->second.pop_back(); 1496 if (SII->second.empty()) { 1497 SpillIdxes.erase(MBBId); 1498 SpillMBBs.reset(MBBId); 1499 } 1500 } 1501 } 1502 } 1503 1504 if (HasUse) { 1505 DenseMap<unsigned, std::vector<SRInfo> >::iterator SII = 1506 SpillIdxes.find(MBBId); 1507 if (SII != SpillIdxes.end() && 1508 SII->second.back().vreg == NewVReg && 1509 (int)index > SII->second.back().index) 1510 // Use(s) following the last def, it's not safe to fold the spill. 1511 SII->second.back().canFold = false; 1512 DenseMap<unsigned, std::vector<SRInfo> >::iterator RII = 1513 RestoreIdxes.find(MBBId); 1514 if (RII != RestoreIdxes.end() && RII->second.back().vreg == NewVReg) 1515 // If we are splitting live intervals, only fold if it's the first 1516 // use and there isn't another use later in the MBB. 1517 RII->second.back().canFold = false; 1518 else if (IsNew) { 1519 // Only need a reload if there isn't an earlier def / use. 1520 if (RII == RestoreIdxes.end()) { 1521 std::vector<SRInfo> Infos; 1522 Infos.push_back(SRInfo(index, NewVReg, true)); 1523 RestoreIdxes.insert(std::make_pair(MBBId, Infos)); 1524 } else { 1525 RII->second.push_back(SRInfo(index, NewVReg, true)); 1526 } 1527 RestoreMBBs.set(MBBId); 1528 } 1529 } 1530 1531 // Update spill weight. 1532 unsigned loopDepth = loopInfo->getLoopDepth(MBB); 1533 nI.weight += getSpillWeight(HasDef, HasUse, loopDepth); 1534 } 1535 1536 if (NewVReg && TrySplit && AllCanFold) { 1537 // If all of its def / use can be folded, give it a low spill weight. 1538 LiveInterval &nI = getOrCreateInterval(NewVReg); 1539 nI.weight /= 10.0F; 1540 } 1541} 1542 1543bool LiveIntervals::alsoFoldARestore(int Id, int index, unsigned vr, 1544 BitVector &RestoreMBBs, 1545 DenseMap<unsigned,std::vector<SRInfo> > &RestoreIdxes) { 1546 if (!RestoreMBBs[Id]) 1547 return false; 1548 std::vector<SRInfo> &Restores = RestoreIdxes[Id]; 1549 for (unsigned i = 0, e = Restores.size(); i != e; ++i) 1550 if (Restores[i].index == index && 1551 Restores[i].vreg == vr && 1552 Restores[i].canFold) 1553 return true; 1554 return false; 1555} 1556 1557void LiveIntervals::eraseRestoreInfo(int Id, int index, unsigned vr, 1558 BitVector &RestoreMBBs, 1559 DenseMap<unsigned,std::vector<SRInfo> > &RestoreIdxes) { 1560 if (!RestoreMBBs[Id]) 1561 return; 1562 std::vector<SRInfo> &Restores = RestoreIdxes[Id]; 1563 for (unsigned i = 0, e = Restores.size(); i != e; ++i) 1564 if (Restores[i].index == index && Restores[i].vreg) 1565 Restores[i].index = -1; 1566} 1567 1568/// handleSpilledImpDefs - Remove IMPLICIT_DEF instructions which are being 1569/// spilled and create empty intervals for their uses. 1570void 1571LiveIntervals::handleSpilledImpDefs(const LiveInterval &li, VirtRegMap &vrm, 1572 const TargetRegisterClass* rc, 1573 std::vector<LiveInterval*> &NewLIs) { 1574 for (MachineRegisterInfo::reg_iterator ri = mri_->reg_begin(li.reg), 1575 re = mri_->reg_end(); ri != re; ) { 1576 MachineOperand &O = ri.getOperand(); 1577 MachineInstr *MI = &*ri; 1578 ++ri; 1579 if (O.isDef()) { 1580 assert(MI->getOpcode() == TargetInstrInfo::IMPLICIT_DEF && 1581 "Register def was not rewritten?"); 1582 RemoveMachineInstrFromMaps(MI); 1583 vrm.RemoveMachineInstrFromMaps(MI); 1584 MI->eraseFromParent(); 1585 } else { 1586 // This must be an use of an implicit_def so it's not part of the live 1587 // interval. Create a new empty live interval for it. 1588 // FIXME: Can we simply erase some of the instructions? e.g. Stores? 1589 unsigned NewVReg = mri_->createVirtualRegister(rc); 1590 vrm.grow(); 1591 vrm.setIsImplicitlyDefined(NewVReg); 1592 NewLIs.push_back(&getOrCreateInterval(NewVReg)); 1593 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { 1594 MachineOperand &MO = MI->getOperand(i); 1595 if (MO.isReg() && MO.getReg() == li.reg) 1596 MO.setReg(NewVReg); 1597 } 1598 } 1599 } 1600} 1601 1602namespace { 1603 struct LISorter { 1604 bool operator()(LiveInterval* A, LiveInterval* B) { 1605 return A->beginNumber() < B->beginNumber(); 1606 } 1607 }; 1608} 1609 1610std::vector<LiveInterval*> LiveIntervals:: 1611addIntervalsForSpillsFast(const LiveInterval &li, 1612 const MachineLoopInfo *loopInfo, 1613 VirtRegMap &vrm, float& SSWeight) { 1614 unsigned slot = vrm.assignVirt2StackSlot(li.reg); 1615 1616 std::vector<LiveInterval*> added; 1617 1618 assert(li.weight != HUGE_VALF && 1619 "attempt to spill already spilled interval!"); 1620 1621 DOUT << "\t\t\t\tadding intervals for spills for interval: "; 1622 DEBUG(li.dump()); 1623 DOUT << '\n'; 1624 1625 const TargetRegisterClass* rc = mri_->getRegClass(li.reg); 1626 1627 DenseMap<MachineInstr*, unsigned> VRegMap; 1628 DenseMap<MachineInstr*, VNInfo*> VNMap; 1629 1630 SSWeight = 0.0f; 1631 1632 for (MachineRegisterInfo::reg_iterator RI = mri_->reg_begin(li.reg), 1633 RE = mri_->reg_end(); RI != RE; ) { 1634 // Create a new virtual register for the spill interval. 1635 MachineOperand& MO = RI.getOperand(); 1636 unsigned NewVReg = 0; 1637 bool newInt = false; 1638 if (!VRegMap.count(MO.getParent())) { 1639 VRegMap[MO.getParent()] = NewVReg = mri_->createVirtualRegister(rc); 1640 vrm.grow(); 1641 vrm.assignVirt2StackSlot(NewVReg, slot); 1642 1643 newInt = true; 1644 } else 1645 NewVReg = VRegMap[MO.getParent()]; 1646 1647 // Increment iterator to avoid invalidation. 1648 ++RI; 1649 1650 MO.setReg(NewVReg); 1651 1652 // create a new register for this spill 1653 LiveInterval &nI = getOrCreateInterval(NewVReg); 1654 1655 // the spill weight is now infinity as it 1656 // cannot be spilled again 1657 nI.weight = HUGE_VALF; 1658 1659 unsigned index = getInstructionIndex(MO.getParent()); 1660 bool HasUse = MO.isUse(); 1661 bool HasDef = MO.isDef(); 1662 if (!VNMap.count(MO.getParent())) 1663 VNMap[MO.getParent()] = nI.getNextValue(~0U, 0, getVNInfoAllocator()); 1664 if (HasUse) { 1665 LiveRange LR(getLoadIndex(index), getUseIndex(index), 1666 VNMap[MO.getParent()]); 1667 DOUT << " +" << LR; 1668 nI.addRange(LR); 1669 } 1670 if (HasDef) { 1671 LiveRange LR(getDefIndex(index), getStoreIndex(index), 1672 VNMap[MO.getParent()]); 1673 DOUT << " +" << LR; 1674 nI.addRange(LR); 1675 } 1676 1677 if (newInt) 1678 added.push_back(&nI); 1679 1680 DOUT << "\t\t\t\tadded new interval: "; 1681 DEBUG(nI.dump()); 1682 DOUT << '\n'; 1683 1684 unsigned loopDepth = loopInfo->getLoopDepth(MO.getParent()->getParent()); 1685 if (HasUse) { 1686 if (HasDef) 1687 SSWeight += getSpillWeight(true, true, loopDepth); 1688 else 1689 SSWeight += getSpillWeight(false, true, loopDepth); 1690 } else 1691 SSWeight += getSpillWeight(true, false, loopDepth); 1692 1693 } 1694 1695 std::sort(added.begin(), added.end(), LISorter()); 1696 1697 return added; 1698} 1699 1700std::vector<LiveInterval*> LiveIntervals:: 1701addIntervalsForSpills(const LiveInterval &li, 1702 const MachineLoopInfo *loopInfo, VirtRegMap &vrm, 1703 float &SSWeight) { 1704 1705 if (EnableFastSpilling) 1706 return addIntervalsForSpillsFast(li, loopInfo, vrm, SSWeight); 1707 1708 assert(li.weight != HUGE_VALF && 1709 "attempt to spill already spilled interval!"); 1710 1711 DOUT << "\t\t\t\tadding intervals for spills for interval: "; 1712 li.print(DOUT, tri_); 1713 DOUT << '\n'; 1714 1715 // Spill slot weight. 1716 SSWeight = 0.0f; 1717 1718 // Each bit specify whether it a spill is required in the MBB. 1719 BitVector SpillMBBs(mf_->getNumBlockIDs()); 1720 DenseMap<unsigned, std::vector<SRInfo> > SpillIdxes; 1721 BitVector RestoreMBBs(mf_->getNumBlockIDs()); 1722 DenseMap<unsigned, std::vector<SRInfo> > RestoreIdxes; 1723 DenseMap<unsigned,unsigned> MBBVRegsMap; 1724 std::vector<LiveInterval*> NewLIs; 1725 const TargetRegisterClass* rc = mri_->getRegClass(li.reg); 1726 1727 unsigned NumValNums = li.getNumValNums(); 1728 SmallVector<MachineInstr*, 4> ReMatDefs; 1729 ReMatDefs.resize(NumValNums, NULL); 1730 SmallVector<MachineInstr*, 4> ReMatOrigDefs; 1731 ReMatOrigDefs.resize(NumValNums, NULL); 1732 SmallVector<int, 4> ReMatIds; 1733 ReMatIds.resize(NumValNums, VirtRegMap::MAX_STACK_SLOT); 1734 BitVector ReMatDelete(NumValNums); 1735 unsigned Slot = VirtRegMap::MAX_STACK_SLOT; 1736 1737 // Spilling a split live interval. It cannot be split any further. Also, 1738 // it's also guaranteed to be a single val# / range interval. 1739 if (vrm.getPreSplitReg(li.reg)) { 1740 vrm.setIsSplitFromReg(li.reg, 0); 1741 // Unset the split kill marker on the last use. 1742 unsigned KillIdx = vrm.getKillPoint(li.reg); 1743 if (KillIdx) { 1744 MachineInstr *KillMI = getInstructionFromIndex(KillIdx); 1745 assert(KillMI && "Last use disappeared?"); 1746 int KillOp = KillMI->findRegisterUseOperandIdx(li.reg, true); 1747 assert(KillOp != -1 && "Last use disappeared?"); 1748 KillMI->getOperand(KillOp).setIsKill(false); 1749 } 1750 vrm.removeKillPoint(li.reg); 1751 bool DefIsReMat = vrm.isReMaterialized(li.reg); 1752 Slot = vrm.getStackSlot(li.reg); 1753 assert(Slot != VirtRegMap::MAX_STACK_SLOT); 1754 MachineInstr *ReMatDefMI = DefIsReMat ? 1755 vrm.getReMaterializedMI(li.reg) : NULL; 1756 int LdSlot = 0; 1757 bool isLoadSS = DefIsReMat && tii_->isLoadFromStackSlot(ReMatDefMI, LdSlot); 1758 bool isLoad = isLoadSS || 1759 (DefIsReMat && (ReMatDefMI->getDesc().isSimpleLoad())); 1760 bool IsFirstRange = true; 1761 for (LiveInterval::Ranges::const_iterator 1762 I = li.ranges.begin(), E = li.ranges.end(); I != E; ++I) { 1763 // If this is a split live interval with multiple ranges, it means there 1764 // are two-address instructions that re-defined the value. Only the 1765 // first def can be rematerialized! 1766 if (IsFirstRange) { 1767 // Note ReMatOrigDefMI has already been deleted. 1768 rewriteInstructionsForSpills(li, false, I, NULL, ReMatDefMI, 1769 Slot, LdSlot, isLoad, isLoadSS, DefIsReMat, 1770 false, vrm, rc, ReMatIds, loopInfo, 1771 SpillMBBs, SpillIdxes, RestoreMBBs, RestoreIdxes, 1772 MBBVRegsMap, NewLIs, SSWeight); 1773 } else { 1774 rewriteInstructionsForSpills(li, false, I, NULL, 0, 1775 Slot, 0, false, false, false, 1776 false, vrm, rc, ReMatIds, loopInfo, 1777 SpillMBBs, SpillIdxes, RestoreMBBs, RestoreIdxes, 1778 MBBVRegsMap, NewLIs, SSWeight); 1779 } 1780 IsFirstRange = false; 1781 } 1782 1783 SSWeight = 0.0f; // Already accounted for when split. 1784 handleSpilledImpDefs(li, vrm, rc, NewLIs); 1785 return NewLIs; 1786 } 1787 1788 bool TrySplit = SplitAtBB && !intervalIsInOneMBB(li); 1789 if (SplitLimit != -1 && (int)numSplits >= SplitLimit) 1790 TrySplit = false; 1791 if (TrySplit) 1792 ++numSplits; 1793 bool NeedStackSlot = false; 1794 for (LiveInterval::const_vni_iterator i = li.vni_begin(), e = li.vni_end(); 1795 i != e; ++i) { 1796 const VNInfo *VNI = *i; 1797 unsigned VN = VNI->id; 1798 unsigned DefIdx = VNI->def; 1799 if (DefIdx == ~1U) 1800 continue; // Dead val#. 1801 // Is the def for the val# rematerializable? 1802 MachineInstr *ReMatDefMI = (DefIdx == ~0u) 1803 ? 0 : getInstructionFromIndex(DefIdx); 1804 bool dummy; 1805 if (ReMatDefMI && isReMaterializable(li, VNI, ReMatDefMI, dummy)) { 1806 // Remember how to remat the def of this val#. 1807 ReMatOrigDefs[VN] = ReMatDefMI; 1808 // Original def may be modified so we have to make a copy here. 1809 MachineInstr *Clone = mf_->CloneMachineInstr(ReMatDefMI); 1810 ClonedMIs.push_back(Clone); 1811 ReMatDefs[VN] = Clone; 1812 1813 bool CanDelete = true; 1814 if (VNI->hasPHIKill) { 1815 // A kill is a phi node, not all of its uses can be rematerialized. 1816 // It must not be deleted. 1817 CanDelete = false; 1818 // Need a stack slot if there is any live range where uses cannot be 1819 // rematerialized. 1820 NeedStackSlot = true; 1821 } 1822 if (CanDelete) 1823 ReMatDelete.set(VN); 1824 } else { 1825 // Need a stack slot if there is any live range where uses cannot be 1826 // rematerialized. 1827 NeedStackSlot = true; 1828 } 1829 } 1830 1831 // One stack slot per live interval. 1832 if (NeedStackSlot && vrm.getPreSplitReg(li.reg) == 0) 1833 Slot = vrm.assignVirt2StackSlot(li.reg); 1834 1835 // Create new intervals and rewrite defs and uses. 1836 for (LiveInterval::Ranges::const_iterator 1837 I = li.ranges.begin(), E = li.ranges.end(); I != E; ++I) { 1838 MachineInstr *ReMatDefMI = ReMatDefs[I->valno->id]; 1839 MachineInstr *ReMatOrigDefMI = ReMatOrigDefs[I->valno->id]; 1840 bool DefIsReMat = ReMatDefMI != NULL; 1841 bool CanDelete = ReMatDelete[I->valno->id]; 1842 int LdSlot = 0; 1843 bool isLoadSS = DefIsReMat && tii_->isLoadFromStackSlot(ReMatDefMI, LdSlot); 1844 bool isLoad = isLoadSS || 1845 (DefIsReMat && ReMatDefMI->getDesc().isSimpleLoad()); 1846 rewriteInstructionsForSpills(li, TrySplit, I, ReMatOrigDefMI, ReMatDefMI, 1847 Slot, LdSlot, isLoad, isLoadSS, DefIsReMat, 1848 CanDelete, vrm, rc, ReMatIds, loopInfo, 1849 SpillMBBs, SpillIdxes, RestoreMBBs, RestoreIdxes, 1850 MBBVRegsMap, NewLIs, SSWeight); 1851 } 1852 1853 // Insert spills / restores if we are splitting. 1854 if (!TrySplit) { 1855 handleSpilledImpDefs(li, vrm, rc, NewLIs); 1856 return NewLIs; 1857 } 1858 1859 SmallPtrSet<LiveInterval*, 4> AddedKill; 1860 SmallVector<unsigned, 2> Ops; 1861 if (NeedStackSlot) { 1862 int Id = SpillMBBs.find_first(); 1863 while (Id != -1) { 1864 MachineBasicBlock *MBB = mf_->getBlockNumbered(Id); 1865 unsigned loopDepth = loopInfo->getLoopDepth(MBB); 1866 std::vector<SRInfo> &spills = SpillIdxes[Id]; 1867 for (unsigned i = 0, e = spills.size(); i != e; ++i) { 1868 int index = spills[i].index; 1869 unsigned VReg = spills[i].vreg; 1870 LiveInterval &nI = getOrCreateInterval(VReg); 1871 bool isReMat = vrm.isReMaterialized(VReg); 1872 MachineInstr *MI = getInstructionFromIndex(index); 1873 bool CanFold = false; 1874 bool FoundUse = false; 1875 Ops.clear(); 1876 if (spills[i].canFold) { 1877 CanFold = true; 1878 for (unsigned j = 0, ee = MI->getNumOperands(); j != ee; ++j) { 1879 MachineOperand &MO = MI->getOperand(j); 1880 if (!MO.isRegister() || MO.getReg() != VReg) 1881 continue; 1882 1883 Ops.push_back(j); 1884 if (MO.isDef()) 1885 continue; 1886 if (isReMat || 1887 (!FoundUse && !alsoFoldARestore(Id, index, VReg, 1888 RestoreMBBs, RestoreIdxes))) { 1889 // MI has two-address uses of the same register. If the use 1890 // isn't the first and only use in the BB, then we can't fold 1891 // it. FIXME: Move this to rewriteInstructionsForSpills. 1892 CanFold = false; 1893 break; 1894 } 1895 FoundUse = true; 1896 } 1897 } 1898 // Fold the store into the def if possible. 1899 bool Folded = false; 1900 if (CanFold && !Ops.empty()) { 1901 if (tryFoldMemoryOperand(MI, vrm, NULL, index, Ops, true, Slot,VReg)){ 1902 Folded = true; 1903 if (FoundUse > 0) { 1904 // Also folded uses, do not issue a load. 1905 eraseRestoreInfo(Id, index, VReg, RestoreMBBs, RestoreIdxes); 1906 nI.removeRange(getLoadIndex(index), getUseIndex(index)+1); 1907 } 1908 nI.removeRange(getDefIndex(index), getStoreIndex(index)); 1909 } 1910 } 1911 1912 // Otherwise tell the spiller to issue a spill. 1913 if (!Folded) { 1914 LiveRange *LR = &nI.ranges[nI.ranges.size()-1]; 1915 bool isKill = LR->end == getStoreIndex(index); 1916 if (!MI->registerDefIsDead(nI.reg)) 1917 // No need to spill a dead def. 1918 vrm.addSpillPoint(VReg, isKill, MI); 1919 if (isKill) 1920 AddedKill.insert(&nI); 1921 } 1922 1923 // Update spill slot weight. 1924 if (!isReMat) 1925 SSWeight += getSpillWeight(true, false, loopDepth); 1926 } 1927 Id = SpillMBBs.find_next(Id); 1928 } 1929 } 1930 1931 int Id = RestoreMBBs.find_first(); 1932 while (Id != -1) { 1933 MachineBasicBlock *MBB = mf_->getBlockNumbered(Id); 1934 unsigned loopDepth = loopInfo->getLoopDepth(MBB); 1935 1936 std::vector<SRInfo> &restores = RestoreIdxes[Id]; 1937 for (unsigned i = 0, e = restores.size(); i != e; ++i) { 1938 int index = restores[i].index; 1939 if (index == -1) 1940 continue; 1941 unsigned VReg = restores[i].vreg; 1942 LiveInterval &nI = getOrCreateInterval(VReg); 1943 bool isReMat = vrm.isReMaterialized(VReg); 1944 MachineInstr *MI = getInstructionFromIndex(index); 1945 bool CanFold = false; 1946 Ops.clear(); 1947 if (restores[i].canFold) { 1948 CanFold = true; 1949 for (unsigned j = 0, ee = MI->getNumOperands(); j != ee; ++j) { 1950 MachineOperand &MO = MI->getOperand(j); 1951 if (!MO.isRegister() || MO.getReg() != VReg) 1952 continue; 1953 1954 if (MO.isDef()) { 1955 // If this restore were to be folded, it would have been folded 1956 // already. 1957 CanFold = false; 1958 break; 1959 } 1960 Ops.push_back(j); 1961 } 1962 } 1963 1964 // Fold the load into the use if possible. 1965 bool Folded = false; 1966 if (CanFold && !Ops.empty()) { 1967 if (!isReMat) 1968 Folded = tryFoldMemoryOperand(MI, vrm, NULL,index,Ops,true,Slot,VReg); 1969 else { 1970 MachineInstr *ReMatDefMI = vrm.getReMaterializedMI(VReg); 1971 int LdSlot = 0; 1972 bool isLoadSS = tii_->isLoadFromStackSlot(ReMatDefMI, LdSlot); 1973 // If the rematerializable def is a load, also try to fold it. 1974 if (isLoadSS || ReMatDefMI->getDesc().isSimpleLoad()) 1975 Folded = tryFoldMemoryOperand(MI, vrm, ReMatDefMI, index, 1976 Ops, isLoadSS, LdSlot, VReg); 1977 unsigned ImpUse = getReMatImplicitUse(li, ReMatDefMI); 1978 if (ImpUse) { 1979 // Re-matting an instruction with virtual register use. Add the 1980 // register as an implicit use on the use MI and update the register 1981 // interval's spill weight to HUGE_VALF to prevent it from being 1982 // spilled. 1983 LiveInterval &ImpLi = getInterval(ImpUse); 1984 ImpLi.weight = HUGE_VALF; 1985 MI->addOperand(MachineOperand::CreateReg(ImpUse, false, true)); 1986 } 1987 } 1988 } 1989 // If folding is not possible / failed, then tell the spiller to issue a 1990 // load / rematerialization for us. 1991 if (Folded) 1992 nI.removeRange(getLoadIndex(index), getUseIndex(index)+1); 1993 else 1994 vrm.addRestorePoint(VReg, MI); 1995 1996 // Update spill slot weight. 1997 if (!isReMat) 1998 SSWeight += getSpillWeight(false, true, loopDepth); 1999 } 2000 Id = RestoreMBBs.find_next(Id); 2001 } 2002 2003 // Finalize intervals: add kills, finalize spill weights, and filter out 2004 // dead intervals. 2005 std::vector<LiveInterval*> RetNewLIs; 2006 for (unsigned i = 0, e = NewLIs.size(); i != e; ++i) { 2007 LiveInterval *LI = NewLIs[i]; 2008 if (!LI->empty()) { 2009 LI->weight /= InstrSlots::NUM * getApproximateInstructionCount(*LI); 2010 if (!AddedKill.count(LI)) { 2011 LiveRange *LR = &LI->ranges[LI->ranges.size()-1]; 2012 unsigned LastUseIdx = getBaseIndex(LR->end); 2013 MachineInstr *LastUse = getInstructionFromIndex(LastUseIdx); 2014 int UseIdx = LastUse->findRegisterUseOperandIdx(LI->reg, false); 2015 assert(UseIdx != -1); 2016 if (LastUse->getOperand(UseIdx).isImplicit() || 2017 LastUse->getDesc().getOperandConstraint(UseIdx,TOI::TIED_TO) == -1){ 2018 LastUse->getOperand(UseIdx).setIsKill(); 2019 vrm.addKillPoint(LI->reg, LastUseIdx); 2020 } 2021 } 2022 RetNewLIs.push_back(LI); 2023 } 2024 } 2025 2026 handleSpilledImpDefs(li, vrm, rc, RetNewLIs); 2027 return RetNewLIs; 2028} 2029 2030/// hasAllocatableSuperReg - Return true if the specified physical register has 2031/// any super register that's allocatable. 2032bool LiveIntervals::hasAllocatableSuperReg(unsigned Reg) const { 2033 for (const unsigned* AS = tri_->getSuperRegisters(Reg); *AS; ++AS) 2034 if (allocatableRegs_[*AS] && hasInterval(*AS)) 2035 return true; 2036 return false; 2037} 2038 2039/// getRepresentativeReg - Find the largest super register of the specified 2040/// physical register. 2041unsigned LiveIntervals::getRepresentativeReg(unsigned Reg) const { 2042 // Find the largest super-register that is allocatable. 2043 unsigned BestReg = Reg; 2044 for (const unsigned* AS = tri_->getSuperRegisters(Reg); *AS; ++AS) { 2045 unsigned SuperReg = *AS; 2046 if (!hasAllocatableSuperReg(SuperReg) && hasInterval(SuperReg)) { 2047 BestReg = SuperReg; 2048 break; 2049 } 2050 } 2051 return BestReg; 2052} 2053 2054/// getNumConflictsWithPhysReg - Return the number of uses and defs of the 2055/// specified interval that conflicts with the specified physical register. 2056unsigned LiveIntervals::getNumConflictsWithPhysReg(const LiveInterval &li, 2057 unsigned PhysReg) const { 2058 unsigned NumConflicts = 0; 2059 const LiveInterval &pli = getInterval(getRepresentativeReg(PhysReg)); 2060 for (MachineRegisterInfo::reg_iterator I = mri_->reg_begin(li.reg), 2061 E = mri_->reg_end(); I != E; ++I) { 2062 MachineOperand &O = I.getOperand(); 2063 MachineInstr *MI = O.getParent(); 2064 unsigned Index = getInstructionIndex(MI); 2065 if (pli.liveAt(Index)) 2066 ++NumConflicts; 2067 } 2068 return NumConflicts; 2069} 2070 2071/// spillPhysRegAroundRegDefsUses - Spill the specified physical register 2072/// around all defs and uses of the specified interval. 2073void LiveIntervals::spillPhysRegAroundRegDefsUses(const LiveInterval &li, 2074 unsigned PhysReg, VirtRegMap &vrm) { 2075 unsigned SpillReg = getRepresentativeReg(PhysReg); 2076 2077 for (const unsigned *AS = tri_->getAliasSet(PhysReg); *AS; ++AS) 2078 // If there are registers which alias PhysReg, but which are not a 2079 // sub-register of the chosen representative super register. Assert 2080 // since we can't handle it yet. 2081 assert(*AS == SpillReg || !allocatableRegs_[*AS] || 2082 tri_->isSuperRegister(*AS, SpillReg)); 2083 2084 LiveInterval &pli = getInterval(SpillReg); 2085 SmallPtrSet<MachineInstr*, 8> SeenMIs; 2086 for (MachineRegisterInfo::reg_iterator I = mri_->reg_begin(li.reg), 2087 E = mri_->reg_end(); I != E; ++I) { 2088 MachineOperand &O = I.getOperand(); 2089 MachineInstr *MI = O.getParent(); 2090 if (SeenMIs.count(MI)) 2091 continue; 2092 SeenMIs.insert(MI); 2093 unsigned Index = getInstructionIndex(MI); 2094 if (pli.liveAt(Index)) { 2095 vrm.addEmergencySpill(SpillReg, MI); 2096 pli.removeRange(getLoadIndex(Index), getStoreIndex(Index)+1); 2097 for (const unsigned* AS = tri_->getSubRegisters(SpillReg); *AS; ++AS) { 2098 if (!hasInterval(*AS)) 2099 continue; 2100 LiveInterval &spli = getInterval(*AS); 2101 if (spli.liveAt(Index)) 2102 spli.removeRange(getLoadIndex(Index), getStoreIndex(Index)+1); 2103 } 2104 } 2105 } 2106} 2107 2108LiveRange LiveIntervals::addLiveRangeToEndOfBlock(unsigned reg, 2109 MachineInstr* startInst) { 2110 LiveInterval& Interval = getOrCreateInterval(reg); 2111 VNInfo* VN = Interval.getNextValue( 2112 getInstructionIndex(startInst) + InstrSlots::DEF, 2113 startInst, getVNInfoAllocator()); 2114 VN->hasPHIKill = true; 2115 VN->kills.push_back(getMBBEndIdx(startInst->getParent())); 2116 LiveRange LR(getInstructionIndex(startInst) + InstrSlots::DEF, 2117 getMBBEndIdx(startInst->getParent()) + 1, VN); 2118 Interval.addRange(LR); 2119 2120 return LR; 2121} 2122