LiveIntervalAnalysis.cpp revision 69244300b8a0112efb44b6273ecea4ca6264b8cf
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/CodeGen/LiveVariables.h" 23#include "llvm/CodeGen/MachineFrameInfo.h" 24#include "llvm/CodeGen/MachineInstr.h" 25#include "llvm/CodeGen/MachineLoopInfo.h" 26#include "llvm/CodeGen/MachineRegisterInfo.h" 27#include "llvm/CodeGen/Passes.h" 28#include "llvm/Target/MRegisterInfo.h" 29#include "llvm/Target/TargetInstrInfo.h" 30#include "llvm/Target/TargetMachine.h" 31#include "llvm/Support/CommandLine.h" 32#include "llvm/Support/Debug.h" 33#include "llvm/ADT/Statistic.h" 34#include "llvm/ADT/STLExtras.h" 35#include <algorithm> 36#include <cmath> 37using namespace llvm; 38 39namespace { 40 // Hidden options for help debugging. 41 cl::opt<bool> DisableReMat("disable-rematerialization", 42 cl::init(false), cl::Hidden); 43 44 cl::opt<bool> SplitAtBB("split-intervals-at-bb", 45 cl::init(true), cl::Hidden); 46 cl::opt<int> SplitLimit("split-limit", 47 cl::init(-1), cl::Hidden); 48} 49 50STATISTIC(numIntervals, "Number of original intervals"); 51STATISTIC(numIntervalsAfter, "Number of intervals after coalescing"); 52STATISTIC(numFolds , "Number of loads/stores folded into instructions"); 53STATISTIC(numSplits , "Number of intervals split"); 54 55char LiveIntervals::ID = 0; 56namespace { 57 RegisterPass<LiveIntervals> X("liveintervals", "Live Interval Analysis"); 58} 59 60void LiveIntervals::getAnalysisUsage(AnalysisUsage &AU) const { 61 AU.addPreserved<LiveVariables>(); 62 AU.addRequired<LiveVariables>(); 63 AU.addPreservedID(MachineLoopInfoID); 64 AU.addPreservedID(MachineDominatorsID); 65 AU.addPreservedID(PHIEliminationID); 66 AU.addRequiredID(PHIEliminationID); 67 AU.addRequiredID(TwoAddressInstructionPassID); 68 MachineFunctionPass::getAnalysisUsage(AU); 69} 70 71void LiveIntervals::releaseMemory() { 72 Idx2MBBMap.clear(); 73 mi2iMap_.clear(); 74 i2miMap_.clear(); 75 r2iMap_.clear(); 76 // Release VNInfo memroy regions after all VNInfo objects are dtor'd. 77 VNInfoAllocator.Reset(); 78 for (unsigned i = 0, e = ClonedMIs.size(); i != e; ++i) 79 delete ClonedMIs[i]; 80} 81 82namespace llvm { 83 inline bool operator<(unsigned V, const IdxMBBPair &IM) { 84 return V < IM.first; 85 } 86 87 inline bool operator<(const IdxMBBPair &IM, unsigned V) { 88 return IM.first < V; 89 } 90 91 struct Idx2MBBCompare { 92 bool operator()(const IdxMBBPair &LHS, const IdxMBBPair &RHS) const { 93 return LHS.first < RHS.first; 94 } 95 }; 96} 97 98/// runOnMachineFunction - Register allocate the whole function 99/// 100bool LiveIntervals::runOnMachineFunction(MachineFunction &fn) { 101 mf_ = &fn; 102 tm_ = &fn.getTarget(); 103 mri_ = tm_->getRegisterInfo(); 104 tii_ = tm_->getInstrInfo(); 105 lv_ = &getAnalysis<LiveVariables>(); 106 allocatableRegs_ = mri_->getAllocatableSet(fn); 107 108 // Number MachineInstrs and MachineBasicBlocks. 109 // Initialize MBB indexes to a sentinal. 110 MBB2IdxMap.resize(mf_->getNumBlockIDs(), std::make_pair(~0U,~0U)); 111 112 unsigned MIIndex = 0; 113 for (MachineFunction::iterator MBB = mf_->begin(), E = mf_->end(); 114 MBB != E; ++MBB) { 115 unsigned StartIdx = MIIndex; 116 117 for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end(); 118 I != E; ++I) { 119 bool inserted = mi2iMap_.insert(std::make_pair(I, MIIndex)).second; 120 assert(inserted && "multiple MachineInstr -> index mappings"); 121 i2miMap_.push_back(I); 122 MIIndex += InstrSlots::NUM; 123 } 124 125 // Set the MBB2IdxMap entry for this MBB. 126 MBB2IdxMap[MBB->getNumber()] = std::make_pair(StartIdx, MIIndex - 1); 127 Idx2MBBMap.push_back(std::make_pair(StartIdx, MBB)); 128 } 129 std::sort(Idx2MBBMap.begin(), Idx2MBBMap.end(), Idx2MBBCompare()); 130 131 computeIntervals(); 132 133 numIntervals += getNumIntervals(); 134 135 DOUT << "********** INTERVALS **********\n"; 136 for (iterator I = begin(), E = end(); I != E; ++I) { 137 I->second.print(DOUT, mri_); 138 DOUT << "\n"; 139 } 140 141 numIntervalsAfter += getNumIntervals(); 142 DEBUG(dump()); 143 return true; 144} 145 146/// print - Implement the dump method. 147void LiveIntervals::print(std::ostream &O, const Module* ) const { 148 O << "********** INTERVALS **********\n"; 149 for (const_iterator I = begin(), E = end(); I != E; ++I) { 150 I->second.print(DOUT, mri_); 151 DOUT << "\n"; 152 } 153 154 O << "********** MACHINEINSTRS **********\n"; 155 for (MachineFunction::iterator mbbi = mf_->begin(), mbbe = mf_->end(); 156 mbbi != mbbe; ++mbbi) { 157 O << ((Value*)mbbi->getBasicBlock())->getName() << ":\n"; 158 for (MachineBasicBlock::iterator mii = mbbi->begin(), 159 mie = mbbi->end(); mii != mie; ++mii) { 160 O << getInstructionIndex(mii) << '\t' << *mii; 161 } 162 } 163} 164 165/// conflictsWithPhysRegDef - Returns true if the specified register 166/// is defined during the duration of the specified interval. 167bool LiveIntervals::conflictsWithPhysRegDef(const LiveInterval &li, 168 VirtRegMap &vrm, unsigned reg) { 169 for (LiveInterval::Ranges::const_iterator 170 I = li.ranges.begin(), E = li.ranges.end(); I != E; ++I) { 171 for (unsigned index = getBaseIndex(I->start), 172 end = getBaseIndex(I->end-1) + InstrSlots::NUM; index != end; 173 index += InstrSlots::NUM) { 174 // skip deleted instructions 175 while (index != end && !getInstructionFromIndex(index)) 176 index += InstrSlots::NUM; 177 if (index == end) break; 178 179 MachineInstr *MI = getInstructionFromIndex(index); 180 unsigned SrcReg, DstReg; 181 if (tii_->isMoveInstr(*MI, SrcReg, DstReg)) 182 if (SrcReg == li.reg || DstReg == li.reg) 183 continue; 184 for (unsigned i = 0; i != MI->getNumOperands(); ++i) { 185 MachineOperand& mop = MI->getOperand(i); 186 if (!mop.isRegister()) 187 continue; 188 unsigned PhysReg = mop.getReg(); 189 if (PhysReg == 0 || PhysReg == li.reg) 190 continue; 191 if (MRegisterInfo::isVirtualRegister(PhysReg)) { 192 if (!vrm.hasPhys(PhysReg)) 193 continue; 194 PhysReg = vrm.getPhys(PhysReg); 195 } 196 if (PhysReg && mri_->regsOverlap(PhysReg, reg)) 197 return true; 198 } 199 } 200 } 201 202 return false; 203} 204 205void LiveIntervals::printRegName(unsigned reg) const { 206 if (MRegisterInfo::isPhysicalRegister(reg)) 207 cerr << mri_->getName(reg); 208 else 209 cerr << "%reg" << reg; 210} 211 212void LiveIntervals::handleVirtualRegisterDef(MachineBasicBlock *mbb, 213 MachineBasicBlock::iterator mi, 214 unsigned MIIdx, 215 LiveInterval &interval) { 216 DOUT << "\t\tregister: "; DEBUG(printRegName(interval.reg)); 217 LiveVariables::VarInfo& vi = lv_->getVarInfo(interval.reg); 218 219 // Virtual registers may be defined multiple times (due to phi 220 // elimination and 2-addr elimination). Much of what we do only has to be 221 // done once for the vreg. We use an empty interval to detect the first 222 // time we see a vreg. 223 if (interval.empty()) { 224 // Get the Idx of the defining instructions. 225 unsigned defIndex = getDefIndex(MIIdx); 226 VNInfo *ValNo; 227 unsigned SrcReg, DstReg; 228 if (tii_->isMoveInstr(*mi, SrcReg, DstReg)) 229 ValNo = interval.getNextValue(defIndex, SrcReg, VNInfoAllocator); 230 else if (mi->getOpcode() == TargetInstrInfo::EXTRACT_SUBREG) 231 ValNo = interval.getNextValue(defIndex, mi->getOperand(1).getReg(), 232 VNInfoAllocator); 233 else 234 ValNo = interval.getNextValue(defIndex, 0, VNInfoAllocator); 235 236 assert(ValNo->id == 0 && "First value in interval is not 0?"); 237 238 // Loop over all of the blocks that the vreg is defined in. There are 239 // two cases we have to handle here. The most common case is a vreg 240 // whose lifetime is contained within a basic block. In this case there 241 // will be a single kill, in MBB, which comes after the definition. 242 if (vi.Kills.size() == 1 && vi.Kills[0]->getParent() == mbb) { 243 // FIXME: what about dead vars? 244 unsigned killIdx; 245 if (vi.Kills[0] != mi) 246 killIdx = getUseIndex(getInstructionIndex(vi.Kills[0]))+1; 247 else 248 killIdx = defIndex+1; 249 250 // If the kill happens after the definition, we have an intra-block 251 // live range. 252 if (killIdx > defIndex) { 253 assert(vi.AliveBlocks.none() && 254 "Shouldn't be alive across any blocks!"); 255 LiveRange LR(defIndex, killIdx, ValNo); 256 interval.addRange(LR); 257 DOUT << " +" << LR << "\n"; 258 interval.addKill(ValNo, killIdx); 259 return; 260 } 261 } 262 263 // The other case we handle is when a virtual register lives to the end 264 // of the defining block, potentially live across some blocks, then is 265 // live into some number of blocks, but gets killed. Start by adding a 266 // range that goes from this definition to the end of the defining block. 267 LiveRange NewLR(defIndex, 268 getInstructionIndex(&mbb->back()) + InstrSlots::NUM, 269 ValNo); 270 DOUT << " +" << NewLR; 271 interval.addRange(NewLR); 272 273 // Iterate over all of the blocks that the variable is completely 274 // live in, adding [insrtIndex(begin), instrIndex(end)+4) to the 275 // live interval. 276 for (unsigned i = 0, e = vi.AliveBlocks.size(); i != e; ++i) { 277 if (vi.AliveBlocks[i]) { 278 MachineBasicBlock *MBB = mf_->getBlockNumbered(i); 279 if (!MBB->empty()) { 280 LiveRange LR(getMBBStartIdx(i), 281 getInstructionIndex(&MBB->back()) + InstrSlots::NUM, 282 ValNo); 283 interval.addRange(LR); 284 DOUT << " +" << LR; 285 } 286 } 287 } 288 289 // Finally, this virtual register is live from the start of any killing 290 // block to the 'use' slot of the killing instruction. 291 for (unsigned i = 0, e = vi.Kills.size(); i != e; ++i) { 292 MachineInstr *Kill = vi.Kills[i]; 293 unsigned killIdx = getUseIndex(getInstructionIndex(Kill))+1; 294 LiveRange LR(getMBBStartIdx(Kill->getParent()), 295 killIdx, ValNo); 296 interval.addRange(LR); 297 interval.addKill(ValNo, killIdx); 298 DOUT << " +" << LR; 299 } 300 301 } else { 302 // If this is the second time we see a virtual register definition, it 303 // must be due to phi elimination or two addr elimination. If this is 304 // the result of two address elimination, then the vreg is one of the 305 // def-and-use register operand. 306 if (mi->isRegReDefinedByTwoAddr(interval.reg)) { 307 // If this is a two-address definition, then we have already processed 308 // the live range. The only problem is that we didn't realize there 309 // are actually two values in the live interval. Because of this we 310 // need to take the LiveRegion that defines this register and split it 311 // into two values. 312 unsigned DefIndex = getDefIndex(getInstructionIndex(vi.DefInst)); 313 unsigned RedefIndex = getDefIndex(MIIdx); 314 315 const LiveRange *OldLR = interval.getLiveRangeContaining(RedefIndex-1); 316 VNInfo *OldValNo = OldLR->valno; 317 unsigned OldEnd = OldLR->end; 318 319 // Delete the initial value, which should be short and continuous, 320 // because the 2-addr copy must be in the same MBB as the redef. 321 interval.removeRange(DefIndex, RedefIndex); 322 323 // Two-address vregs should always only be redefined once. This means 324 // that at this point, there should be exactly one value number in it. 325 assert(interval.containsOneValue() && "Unexpected 2-addr liveint!"); 326 327 // The new value number (#1) is defined by the instruction we claimed 328 // defined value #0. 329 VNInfo *ValNo = interval.getNextValue(0, 0, VNInfoAllocator); 330 interval.copyValNumInfo(ValNo, OldValNo); 331 332 // Value#0 is now defined by the 2-addr instruction. 333 OldValNo->def = RedefIndex; 334 OldValNo->reg = 0; 335 336 // Add the new live interval which replaces the range for the input copy. 337 LiveRange LR(DefIndex, RedefIndex, ValNo); 338 DOUT << " replace range with " << LR; 339 interval.addRange(LR); 340 interval.addKill(ValNo, RedefIndex); 341 interval.removeKills(ValNo, RedefIndex, OldEnd); 342 343 // If this redefinition is dead, we need to add a dummy unit live 344 // range covering the def slot. 345 if (lv_->RegisterDefIsDead(mi, interval.reg)) 346 interval.addRange(LiveRange(RedefIndex, RedefIndex+1, OldValNo)); 347 348 DOUT << " RESULT: "; 349 interval.print(DOUT, mri_); 350 351 } else { 352 // Otherwise, this must be because of phi elimination. If this is the 353 // first redefinition of the vreg that we have seen, go back and change 354 // the live range in the PHI block to be a different value number. 355 if (interval.containsOneValue()) { 356 assert(vi.Kills.size() == 1 && 357 "PHI elimination vreg should have one kill, the PHI itself!"); 358 359 // Remove the old range that we now know has an incorrect number. 360 VNInfo *VNI = interval.getValNumInfo(0); 361 MachineInstr *Killer = vi.Kills[0]; 362 unsigned Start = getMBBStartIdx(Killer->getParent()); 363 unsigned End = getUseIndex(getInstructionIndex(Killer))+1; 364 DOUT << " Removing [" << Start << "," << End << "] from: "; 365 interval.print(DOUT, mri_); DOUT << "\n"; 366 interval.removeRange(Start, End); 367 interval.addKill(VNI, Start); 368 VNI->hasPHIKill = true; 369 DOUT << " RESULT: "; interval.print(DOUT, mri_); 370 371 // Replace the interval with one of a NEW value number. Note that this 372 // value number isn't actually defined by an instruction, weird huh? :) 373 LiveRange LR(Start, End, interval.getNextValue(~0, 0, VNInfoAllocator)); 374 DOUT << " replace range with " << LR; 375 interval.addRange(LR); 376 interval.addKill(LR.valno, End); 377 DOUT << " RESULT: "; interval.print(DOUT, mri_); 378 } 379 380 // In the case of PHI elimination, each variable definition is only 381 // live until the end of the block. We've already taken care of the 382 // rest of the live range. 383 unsigned defIndex = getDefIndex(MIIdx); 384 385 VNInfo *ValNo; 386 unsigned SrcReg, DstReg; 387 if (tii_->isMoveInstr(*mi, SrcReg, DstReg)) 388 ValNo = interval.getNextValue(defIndex, SrcReg, VNInfoAllocator); 389 else if (mi->getOpcode() == TargetInstrInfo::EXTRACT_SUBREG) 390 ValNo = interval.getNextValue(defIndex, mi->getOperand(1).getReg(), 391 VNInfoAllocator); 392 else 393 ValNo = interval.getNextValue(defIndex, 0, VNInfoAllocator); 394 395 unsigned killIndex = getInstructionIndex(&mbb->back()) + InstrSlots::NUM; 396 LiveRange LR(defIndex, killIndex, ValNo); 397 interval.addRange(LR); 398 interval.addKill(ValNo, killIndex); 399 ValNo->hasPHIKill = true; 400 DOUT << " +" << LR; 401 } 402 } 403 404 DOUT << '\n'; 405} 406 407void LiveIntervals::handlePhysicalRegisterDef(MachineBasicBlock *MBB, 408 MachineBasicBlock::iterator mi, 409 unsigned MIIdx, 410 LiveInterval &interval, 411 unsigned SrcReg) { 412 // A physical register cannot be live across basic block, so its 413 // lifetime must end somewhere in its defining basic block. 414 DOUT << "\t\tregister: "; DEBUG(printRegName(interval.reg)); 415 416 unsigned baseIndex = MIIdx; 417 unsigned start = getDefIndex(baseIndex); 418 unsigned end = start; 419 420 // If it is not used after definition, it is considered dead at 421 // the instruction defining it. Hence its interval is: 422 // [defSlot(def), defSlot(def)+1) 423 if (lv_->RegisterDefIsDead(mi, interval.reg)) { 424 DOUT << " dead"; 425 end = getDefIndex(start) + 1; 426 goto exit; 427 } 428 429 // If it is not dead on definition, it must be killed by a 430 // subsequent instruction. Hence its interval is: 431 // [defSlot(def), useSlot(kill)+1) 432 while (++mi != MBB->end()) { 433 baseIndex += InstrSlots::NUM; 434 if (lv_->KillsRegister(mi, interval.reg)) { 435 DOUT << " killed"; 436 end = getUseIndex(baseIndex) + 1; 437 goto exit; 438 } else if (lv_->ModifiesRegister(mi, interval.reg)) { 439 // Another instruction redefines the register before it is ever read. 440 // Then the register is essentially dead at the instruction that defines 441 // it. Hence its interval is: 442 // [defSlot(def), defSlot(def)+1) 443 DOUT << " dead"; 444 end = getDefIndex(start) + 1; 445 goto exit; 446 } 447 } 448 449 // The only case we should have a dead physreg here without a killing or 450 // instruction where we know it's dead is if it is live-in to the function 451 // and never used. 452 assert(!SrcReg && "physreg was not killed in defining block!"); 453 end = getDefIndex(start) + 1; // It's dead. 454 455exit: 456 assert(start < end && "did not find end of interval?"); 457 458 // Already exists? Extend old live interval. 459 LiveInterval::iterator OldLR = interval.FindLiveRangeContaining(start); 460 VNInfo *ValNo = (OldLR != interval.end()) 461 ? OldLR->valno : interval.getNextValue(start, SrcReg, VNInfoAllocator); 462 LiveRange LR(start, end, ValNo); 463 interval.addRange(LR); 464 interval.addKill(LR.valno, end); 465 DOUT << " +" << LR << '\n'; 466} 467 468void LiveIntervals::handleRegisterDef(MachineBasicBlock *MBB, 469 MachineBasicBlock::iterator MI, 470 unsigned MIIdx, 471 unsigned reg) { 472 if (MRegisterInfo::isVirtualRegister(reg)) 473 handleVirtualRegisterDef(MBB, MI, MIIdx, getOrCreateInterval(reg)); 474 else if (allocatableRegs_[reg]) { 475 unsigned SrcReg, DstReg; 476 if (MI->getOpcode() == TargetInstrInfo::EXTRACT_SUBREG) 477 SrcReg = MI->getOperand(1).getReg(); 478 else if (!tii_->isMoveInstr(*MI, SrcReg, DstReg)) 479 SrcReg = 0; 480 handlePhysicalRegisterDef(MBB, MI, MIIdx, getOrCreateInterval(reg), SrcReg); 481 // Def of a register also defines its sub-registers. 482 for (const unsigned* AS = mri_->getSubRegisters(reg); *AS; ++AS) 483 // Avoid processing some defs more than once. 484 if (!MI->findRegisterDefOperand(*AS)) 485 handlePhysicalRegisterDef(MBB, MI, MIIdx, getOrCreateInterval(*AS), 0); 486 } 487} 488 489void LiveIntervals::handleLiveInRegister(MachineBasicBlock *MBB, 490 unsigned MIIdx, 491 LiveInterval &interval, bool isAlias) { 492 DOUT << "\t\tlivein register: "; DEBUG(printRegName(interval.reg)); 493 494 // Look for kills, if it reaches a def before it's killed, then it shouldn't 495 // be considered a livein. 496 MachineBasicBlock::iterator mi = MBB->begin(); 497 unsigned baseIndex = MIIdx; 498 unsigned start = baseIndex; 499 unsigned end = start; 500 while (mi != MBB->end()) { 501 if (lv_->KillsRegister(mi, interval.reg)) { 502 DOUT << " killed"; 503 end = getUseIndex(baseIndex) + 1; 504 goto exit; 505 } else if (lv_->ModifiesRegister(mi, interval.reg)) { 506 // Another instruction redefines the register before it is ever read. 507 // Then the register is essentially dead at the instruction that defines 508 // it. Hence its interval is: 509 // [defSlot(def), defSlot(def)+1) 510 DOUT << " dead"; 511 end = getDefIndex(start) + 1; 512 goto exit; 513 } 514 515 baseIndex += InstrSlots::NUM; 516 ++mi; 517 } 518 519exit: 520 // Live-in register might not be used at all. 521 if (end == MIIdx) { 522 if (isAlias) { 523 DOUT << " dead"; 524 end = getDefIndex(MIIdx) + 1; 525 } else { 526 DOUT << " live through"; 527 end = baseIndex; 528 } 529 } 530 531 LiveRange LR(start, end, interval.getNextValue(start, 0, VNInfoAllocator)); 532 interval.addRange(LR); 533 interval.addKill(LR.valno, end); 534 DOUT << " +" << LR << '\n'; 535} 536 537/// computeIntervals - computes the live intervals for virtual 538/// registers. for some ordering of the machine instructions [1,N] a 539/// live interval is an interval [i, j) where 1 <= i <= j < N for 540/// which a variable is live 541void LiveIntervals::computeIntervals() { 542 DOUT << "********** COMPUTING LIVE INTERVALS **********\n" 543 << "********** Function: " 544 << ((Value*)mf_->getFunction())->getName() << '\n'; 545 // Track the index of the current machine instr. 546 unsigned MIIndex = 0; 547 for (MachineFunction::iterator MBBI = mf_->begin(), E = mf_->end(); 548 MBBI != E; ++MBBI) { 549 MachineBasicBlock *MBB = MBBI; 550 DOUT << ((Value*)MBB->getBasicBlock())->getName() << ":\n"; 551 552 MachineBasicBlock::iterator MI = MBB->begin(), miEnd = MBB->end(); 553 554 // Create intervals for live-ins to this BB first. 555 for (MachineBasicBlock::const_livein_iterator LI = MBB->livein_begin(), 556 LE = MBB->livein_end(); LI != LE; ++LI) { 557 handleLiveInRegister(MBB, MIIndex, getOrCreateInterval(*LI)); 558 // Multiple live-ins can alias the same register. 559 for (const unsigned* AS = mri_->getSubRegisters(*LI); *AS; ++AS) 560 if (!hasInterval(*AS)) 561 handleLiveInRegister(MBB, MIIndex, getOrCreateInterval(*AS), 562 true); 563 } 564 565 for (; MI != miEnd; ++MI) { 566 DOUT << MIIndex << "\t" << *MI; 567 568 // Handle defs. 569 for (int i = MI->getNumOperands() - 1; i >= 0; --i) { 570 MachineOperand &MO = MI->getOperand(i); 571 // handle register defs - build intervals 572 if (MO.isRegister() && MO.getReg() && MO.isDef()) 573 handleRegisterDef(MBB, MI, MIIndex, MO.getReg()); 574 } 575 576 MIIndex += InstrSlots::NUM; 577 } 578 } 579} 580 581bool LiveIntervals::findLiveInMBBs(const LiveRange &LR, 582 SmallVectorImpl<MachineBasicBlock*> &MBBs) const { 583 std::vector<IdxMBBPair>::const_iterator I = 584 std::lower_bound(Idx2MBBMap.begin(), Idx2MBBMap.end(), LR.start); 585 586 bool ResVal = false; 587 while (I != Idx2MBBMap.end()) { 588 if (LR.end <= I->first) 589 break; 590 MBBs.push_back(I->second); 591 ResVal = true; 592 ++I; 593 } 594 return ResVal; 595} 596 597 598LiveInterval LiveIntervals::createInterval(unsigned reg) { 599 float Weight = MRegisterInfo::isPhysicalRegister(reg) ? 600 HUGE_VALF : 0.0F; 601 return LiveInterval(reg, Weight); 602} 603 604 605//===----------------------------------------------------------------------===// 606// Register allocator hooks. 607// 608 609/// isReMaterializable - Returns true if the definition MI of the specified 610/// val# of the specified interval is re-materializable. 611bool LiveIntervals::isReMaterializable(const LiveInterval &li, 612 const VNInfo *ValNo, MachineInstr *MI, 613 bool &isLoad) { 614 if (DisableReMat) 615 return false; 616 617 isLoad = false; 618 const TargetInstrDescriptor *TID = MI->getDesc(); 619 if ((TID->Flags & M_IMPLICIT_DEF_FLAG) || 620 tii_->isTriviallyReMaterializable(MI)) { 621 isLoad = TID->isSimpleLoad(); 622 return true; 623 } 624 625 int FrameIdx = 0; 626 if (!tii_->isLoadFromStackSlot(MI, FrameIdx) || 627 !mf_->getFrameInfo()->isFixedObjectIndex(FrameIdx)) 628 return false; 629 630 // This is a load from fixed stack slot. It can be rematerialized unless it's 631 // re-defined by a two-address instruction. 632 isLoad = true; 633 for (LiveInterval::const_vni_iterator i = li.vni_begin(), e = li.vni_end(); 634 i != e; ++i) { 635 const VNInfo *VNI = *i; 636 if (VNI == ValNo) 637 continue; 638 unsigned DefIdx = VNI->def; 639 if (DefIdx == ~1U) 640 continue; // Dead val#. 641 MachineInstr *DefMI = (DefIdx == ~0u) 642 ? NULL : getInstructionFromIndex(DefIdx); 643 if (DefMI && DefMI->isRegReDefinedByTwoAddr(li.reg)) { 644 isLoad = false; 645 return false; 646 } 647 } 648 return true; 649} 650 651/// isReMaterializable - Returns true if every definition of MI of every 652/// val# of the specified interval is re-materializable. 653bool LiveIntervals::isReMaterializable(const LiveInterval &li, bool &isLoad) { 654 isLoad = false; 655 for (LiveInterval::const_vni_iterator i = li.vni_begin(), e = li.vni_end(); 656 i != e; ++i) { 657 const VNInfo *VNI = *i; 658 unsigned DefIdx = VNI->def; 659 if (DefIdx == ~1U) 660 continue; // Dead val#. 661 // Is the def for the val# rematerializable? 662 if (DefIdx == ~0u) 663 return false; 664 MachineInstr *ReMatDefMI = getInstructionFromIndex(DefIdx); 665 bool DefIsLoad = false; 666 if (!ReMatDefMI || !isReMaterializable(li, VNI, ReMatDefMI, DefIsLoad)) 667 return false; 668 isLoad |= DefIsLoad; 669 } 670 return true; 671} 672 673/// tryFoldMemoryOperand - Attempts to fold either a spill / restore from 674/// slot / to reg or any rematerialized load into ith operand of specified 675/// MI. If it is successul, MI is updated with the newly created MI and 676/// returns true. 677bool LiveIntervals::tryFoldMemoryOperand(MachineInstr* &MI, 678 VirtRegMap &vrm, MachineInstr *DefMI, 679 unsigned InstrIdx, 680 SmallVector<unsigned, 2> &Ops, 681 bool isSS, int Slot, unsigned Reg) { 682 unsigned MRInfo = 0; 683 const TargetInstrDescriptor *TID = MI->getDesc(); 684 // If it is an implicit def instruction, just delete it. 685 if (TID->Flags & M_IMPLICIT_DEF_FLAG) { 686 RemoveMachineInstrFromMaps(MI); 687 vrm.RemoveMachineInstrFromMaps(MI); 688 MI->eraseFromParent(); 689 ++numFolds; 690 return true; 691 } 692 693 SmallVector<unsigned, 2> FoldOps; 694 for (unsigned i = 0, e = Ops.size(); i != e; ++i) { 695 unsigned OpIdx = Ops[i]; 696 // FIXME: fold subreg use. 697 if (MI->getOperand(OpIdx).getSubReg()) 698 return false; 699 if (MI->getOperand(OpIdx).isDef()) 700 MRInfo |= (unsigned)VirtRegMap::isMod; 701 else { 702 // Filter out two-address use operand(s). 703 if (TID->getOperandConstraint(OpIdx, TOI::TIED_TO) != -1) { 704 MRInfo = VirtRegMap::isModRef; 705 continue; 706 } 707 MRInfo |= (unsigned)VirtRegMap::isRef; 708 } 709 FoldOps.push_back(OpIdx); 710 } 711 712 MachineInstr *fmi = isSS ? tii_->foldMemoryOperand(MI, FoldOps, Slot) 713 : tii_->foldMemoryOperand(MI, FoldOps, DefMI); 714 if (fmi) { 715 // Attempt to fold the memory reference into the instruction. If 716 // we can do this, we don't need to insert spill code. 717 if (lv_) 718 lv_->instructionChanged(MI, fmi); 719 else 720 LiveVariables::transferKillDeadInfo(MI, fmi, mri_); 721 MachineBasicBlock &MBB = *MI->getParent(); 722 if (isSS && !mf_->getFrameInfo()->isFixedObjectIndex(Slot)) 723 vrm.virtFolded(Reg, MI, fmi, (VirtRegMap::ModRef)MRInfo); 724 vrm.transferSpillPts(MI, fmi); 725 vrm.transferRestorePts(MI, fmi); 726 mi2iMap_.erase(MI); 727 i2miMap_[InstrIdx /InstrSlots::NUM] = fmi; 728 mi2iMap_[fmi] = InstrIdx; 729 MI = MBB.insert(MBB.erase(MI), fmi); 730 ++numFolds; 731 return true; 732 } 733 return false; 734} 735 736/// canFoldMemoryOperand - Returns true if the specified load / store 737/// folding is possible. 738bool LiveIntervals::canFoldMemoryOperand(MachineInstr *MI, 739 SmallVector<unsigned, 2> &Ops) const { 740 SmallVector<unsigned, 2> FoldOps; 741 for (unsigned i = 0, e = Ops.size(); i != e; ++i) { 742 unsigned OpIdx = Ops[i]; 743 // FIXME: fold subreg use. 744 if (MI->getOperand(OpIdx).getSubReg()) 745 return false; 746 FoldOps.push_back(OpIdx); 747 } 748 749 return tii_->canFoldMemoryOperand(MI, FoldOps); 750} 751 752bool LiveIntervals::intervalIsInOneMBB(const LiveInterval &li) const { 753 SmallPtrSet<MachineBasicBlock*, 4> MBBs; 754 for (LiveInterval::Ranges::const_iterator 755 I = li.ranges.begin(), E = li.ranges.end(); I != E; ++I) { 756 std::vector<IdxMBBPair>::const_iterator II = 757 std::lower_bound(Idx2MBBMap.begin(), Idx2MBBMap.end(), I->start); 758 if (II == Idx2MBBMap.end()) 759 continue; 760 if (I->end > II->first) // crossing a MBB. 761 return false; 762 MBBs.insert(II->second); 763 if (MBBs.size() > 1) 764 return false; 765 } 766 return true; 767} 768 769/// rewriteInstructionForSpills, rewriteInstructionsForSpills - Helper functions 770/// for addIntervalsForSpills to rewrite uses / defs for the given live range. 771bool LiveIntervals:: 772rewriteInstructionForSpills(const LiveInterval &li, bool TrySplit, 773 unsigned id, unsigned index, unsigned end, MachineInstr *MI, 774 MachineInstr *ReMatOrigDefMI, MachineInstr *ReMatDefMI, 775 unsigned Slot, int LdSlot, 776 bool isLoad, bool isLoadSS, bool DefIsReMat, bool CanDelete, 777 VirtRegMap &vrm, MachineRegisterInfo &RegInfo, 778 const TargetRegisterClass* rc, 779 SmallVector<int, 4> &ReMatIds, 780 unsigned &NewVReg, bool &HasDef, bool &HasUse, 781 const MachineLoopInfo *loopInfo, 782 std::map<unsigned,unsigned> &MBBVRegsMap, 783 std::vector<LiveInterval*> &NewLIs) { 784 bool CanFold = false; 785 RestartInstruction: 786 for (unsigned i = 0; i != MI->getNumOperands(); ++i) { 787 MachineOperand& mop = MI->getOperand(i); 788 if (!mop.isRegister()) 789 continue; 790 unsigned Reg = mop.getReg(); 791 unsigned RegI = Reg; 792 if (Reg == 0 || MRegisterInfo::isPhysicalRegister(Reg)) 793 continue; 794 if (Reg != li.reg) 795 continue; 796 797 bool TryFold = !DefIsReMat; 798 bool FoldSS = true; // Default behavior unless it's a remat. 799 int FoldSlot = Slot; 800 if (DefIsReMat) { 801 // If this is the rematerializable definition MI itself and 802 // all of its uses are rematerialized, simply delete it. 803 if (MI == ReMatOrigDefMI && CanDelete) { 804 DOUT << "\t\t\t\tErasing re-materlizable def: "; 805 DOUT << MI << '\n'; 806 RemoveMachineInstrFromMaps(MI); 807 vrm.RemoveMachineInstrFromMaps(MI); 808 MI->eraseFromParent(); 809 break; 810 } 811 812 // If def for this use can't be rematerialized, then try folding. 813 // If def is rematerializable and it's a load, also try folding. 814 TryFold = !ReMatDefMI || (ReMatDefMI && (MI == ReMatOrigDefMI || isLoad)); 815 if (isLoad) { 816 // Try fold loads (from stack slot, constant pool, etc.) into uses. 817 FoldSS = isLoadSS; 818 FoldSlot = LdSlot; 819 } 820 } 821 822 // Scan all of the operands of this instruction rewriting operands 823 // to use NewVReg instead of li.reg as appropriate. We do this for 824 // two reasons: 825 // 826 // 1. If the instr reads the same spilled vreg multiple times, we 827 // want to reuse the NewVReg. 828 // 2. If the instr is a two-addr instruction, we are required to 829 // keep the src/dst regs pinned. 830 // 831 // Keep track of whether we replace a use and/or def so that we can 832 // create the spill interval with the appropriate range. 833 834 HasUse = mop.isUse(); 835 HasDef = mop.isDef(); 836 SmallVector<unsigned, 2> Ops; 837 Ops.push_back(i); 838 for (unsigned j = i+1, e = MI->getNumOperands(); j != e; ++j) { 839 const MachineOperand &MOj = MI->getOperand(j); 840 if (!MOj.isRegister()) 841 continue; 842 unsigned RegJ = MOj.getReg(); 843 if (RegJ == 0 || MRegisterInfo::isPhysicalRegister(RegJ)) 844 continue; 845 if (RegJ == RegI) { 846 Ops.push_back(j); 847 HasUse |= MOj.isUse(); 848 HasDef |= MOj.isDef(); 849 } 850 } 851 852 if (TryFold) { 853 // Do not fold load / store here if we are splitting. We'll find an 854 // optimal point to insert a load / store later. 855 if (!TrySplit) { 856 if (tryFoldMemoryOperand(MI, vrm, ReMatDefMI, index, 857 Ops, FoldSS, FoldSlot, Reg)) { 858 // Folding the load/store can completely change the instruction in 859 // unpredictable ways, rescan it from the beginning. 860 HasUse = false; 861 HasDef = false; 862 CanFold = false; 863 goto RestartInstruction; 864 } 865 } else { 866 CanFold = canFoldMemoryOperand(MI, Ops); 867 } 868 } else 869 CanFold = false; 870 871 // Create a new virtual register for the spill interval. 872 bool CreatedNewVReg = false; 873 if (NewVReg == 0) { 874 NewVReg = RegInfo.createVirtualRegister(rc); 875 vrm.grow(); 876 CreatedNewVReg = true; 877 } 878 mop.setReg(NewVReg); 879 880 // Reuse NewVReg for other reads. 881 for (unsigned j = 0, e = Ops.size(); j != e; ++j) 882 MI->getOperand(Ops[j]).setReg(NewVReg); 883 884 if (CreatedNewVReg) { 885 if (DefIsReMat) { 886 vrm.setVirtIsReMaterialized(NewVReg, ReMatDefMI/*, CanDelete*/); 887 if (ReMatIds[id] == VirtRegMap::MAX_STACK_SLOT) { 888 // Each valnum may have its own remat id. 889 ReMatIds[id] = vrm.assignVirtReMatId(NewVReg); 890 } else { 891 vrm.assignVirtReMatId(NewVReg, ReMatIds[id]); 892 } 893 if (!CanDelete || (HasUse && HasDef)) { 894 // If this is a two-addr instruction then its use operands are 895 // rematerializable but its def is not. It should be assigned a 896 // stack slot. 897 vrm.assignVirt2StackSlot(NewVReg, Slot); 898 } 899 } else { 900 vrm.assignVirt2StackSlot(NewVReg, Slot); 901 } 902 } else if (HasUse && HasDef && 903 vrm.getStackSlot(NewVReg) == VirtRegMap::NO_STACK_SLOT) { 904 // If this interval hasn't been assigned a stack slot (because earlier 905 // def is a deleted remat def), do it now. 906 assert(Slot != VirtRegMap::NO_STACK_SLOT); 907 vrm.assignVirt2StackSlot(NewVReg, Slot); 908 } 909 910 // create a new register interval for this spill / remat. 911 LiveInterval &nI = getOrCreateInterval(NewVReg); 912 if (CreatedNewVReg) { 913 NewLIs.push_back(&nI); 914 MBBVRegsMap.insert(std::make_pair(MI->getParent()->getNumber(), NewVReg)); 915 if (TrySplit) 916 vrm.setIsSplitFromReg(NewVReg, li.reg); 917 } 918 919 if (HasUse) { 920 if (CreatedNewVReg) { 921 LiveRange LR(getLoadIndex(index), getUseIndex(index)+1, 922 nI.getNextValue(~0U, 0, VNInfoAllocator)); 923 DOUT << " +" << LR; 924 nI.addRange(LR); 925 } else { 926 // Extend the split live interval to this def / use. 927 unsigned End = getUseIndex(index)+1; 928 LiveRange LR(nI.ranges[nI.ranges.size()-1].end, End, 929 nI.getValNumInfo(nI.getNumValNums()-1)); 930 DOUT << " +" << LR; 931 nI.addRange(LR); 932 } 933 } 934 if (HasDef) { 935 LiveRange LR(getDefIndex(index), getStoreIndex(index), 936 nI.getNextValue(~0U, 0, VNInfoAllocator)); 937 DOUT << " +" << LR; 938 nI.addRange(LR); 939 } 940 941 DOUT << "\t\t\t\tAdded new interval: "; 942 nI.print(DOUT, mri_); 943 DOUT << '\n'; 944 } 945 return CanFold; 946} 947bool LiveIntervals::anyKillInMBBAfterIdx(const LiveInterval &li, 948 const VNInfo *VNI, 949 MachineBasicBlock *MBB, unsigned Idx) const { 950 unsigned End = getMBBEndIdx(MBB); 951 for (unsigned j = 0, ee = VNI->kills.size(); j != ee; ++j) { 952 unsigned KillIdx = VNI->kills[j]; 953 if (KillIdx > Idx && KillIdx < End) 954 return true; 955 } 956 return false; 957} 958 959static const VNInfo *findDefinedVNInfo(const LiveInterval &li, unsigned DefIdx) { 960 const VNInfo *VNI = NULL; 961 for (LiveInterval::const_vni_iterator i = li.vni_begin(), 962 e = li.vni_end(); i != e; ++i) 963 if ((*i)->def == DefIdx) { 964 VNI = *i; 965 break; 966 } 967 return VNI; 968} 969 970void LiveIntervals:: 971rewriteInstructionsForSpills(const LiveInterval &li, bool TrySplit, 972 LiveInterval::Ranges::const_iterator &I, 973 MachineInstr *ReMatOrigDefMI, MachineInstr *ReMatDefMI, 974 unsigned Slot, int LdSlot, 975 bool isLoad, bool isLoadSS, bool DefIsReMat, bool CanDelete, 976 VirtRegMap &vrm, MachineRegisterInfo &RegInfo, 977 const TargetRegisterClass* rc, 978 SmallVector<int, 4> &ReMatIds, 979 const MachineLoopInfo *loopInfo, 980 BitVector &SpillMBBs, 981 std::map<unsigned, std::vector<SRInfo> > &SpillIdxes, 982 BitVector &RestoreMBBs, 983 std::map<unsigned, std::vector<SRInfo> > &RestoreIdxes, 984 std::map<unsigned,unsigned> &MBBVRegsMap, 985 std::vector<LiveInterval*> &NewLIs) { 986 bool AllCanFold = true; 987 unsigned NewVReg = 0; 988 unsigned index = getBaseIndex(I->start); 989 unsigned end = getBaseIndex(I->end-1) + InstrSlots::NUM; 990 for (; index != end; index += InstrSlots::NUM) { 991 // skip deleted instructions 992 while (index != end && !getInstructionFromIndex(index)) 993 index += InstrSlots::NUM; 994 if (index == end) break; 995 996 MachineInstr *MI = getInstructionFromIndex(index); 997 MachineBasicBlock *MBB = MI->getParent(); 998 unsigned ThisVReg = 0; 999 if (TrySplit) { 1000 std::map<unsigned,unsigned>::const_iterator NVI = 1001 MBBVRegsMap.find(MBB->getNumber()); 1002 if (NVI != MBBVRegsMap.end()) { 1003 ThisVReg = NVI->second; 1004 // One common case: 1005 // x = use 1006 // ... 1007 // ... 1008 // def = ... 1009 // = use 1010 // It's better to start a new interval to avoid artifically 1011 // extend the new interval. 1012 // FIXME: Too slow? Can we fix it after rewriteInstructionsForSpills? 1013 bool MIHasUse = false; 1014 bool MIHasDef = false; 1015 for (unsigned i = 0; i != MI->getNumOperands(); ++i) { 1016 MachineOperand& mop = MI->getOperand(i); 1017 if (!mop.isRegister() || mop.getReg() != li.reg) 1018 continue; 1019 if (mop.isUse()) 1020 MIHasUse = true; 1021 else 1022 MIHasDef = true; 1023 } 1024 if (MIHasDef && !MIHasUse) { 1025 MBBVRegsMap.erase(MBB->getNumber()); 1026 ThisVReg = 0; 1027 } 1028 } 1029 } 1030 1031 bool IsNew = ThisVReg == 0; 1032 if (IsNew) { 1033 // This ends the previous live interval. If all of its def / use 1034 // can be folded, give it a low spill weight. 1035 if (NewVReg && TrySplit && AllCanFold) { 1036 LiveInterval &nI = getOrCreateInterval(NewVReg); 1037 nI.weight /= 10.0F; 1038 } 1039 AllCanFold = true; 1040 } 1041 NewVReg = ThisVReg; 1042 1043 bool HasDef = false; 1044 bool HasUse = false; 1045 bool CanFold = rewriteInstructionForSpills(li, TrySplit, I->valno->id, 1046 index, end, MI, ReMatOrigDefMI, ReMatDefMI, 1047 Slot, LdSlot, isLoad, isLoadSS, DefIsReMat, 1048 CanDelete, vrm, RegInfo, rc, ReMatIds, NewVReg, 1049 HasDef, HasUse, loopInfo, MBBVRegsMap, NewLIs); 1050 if (!HasDef && !HasUse) 1051 continue; 1052 1053 AllCanFold &= CanFold; 1054 1055 // Update weight of spill interval. 1056 LiveInterval &nI = getOrCreateInterval(NewVReg); 1057 if (!TrySplit) { 1058 // The spill weight is now infinity as it cannot be spilled again. 1059 nI.weight = HUGE_VALF; 1060 continue; 1061 } 1062 1063 // Keep track of the last def and first use in each MBB. 1064 unsigned MBBId = MBB->getNumber(); 1065 if (HasDef) { 1066 if (MI != ReMatOrigDefMI || !CanDelete) { 1067 bool HasKill = false; 1068 if (!HasUse) 1069 HasKill = anyKillInMBBAfterIdx(li, I->valno, MBB, getDefIndex(index)); 1070 else { 1071 // If this is a two-address code, then this index starts a new VNInfo. 1072 const VNInfo *VNI = findDefinedVNInfo(li, getDefIndex(index)); 1073 if (VNI) 1074 HasKill = anyKillInMBBAfterIdx(li, VNI, MBB, getDefIndex(index)); 1075 } 1076 std::map<unsigned, std::vector<SRInfo> >::iterator SII = 1077 SpillIdxes.find(MBBId); 1078 if (!HasKill) { 1079 if (SII == SpillIdxes.end()) { 1080 std::vector<SRInfo> S; 1081 S.push_back(SRInfo(index, NewVReg, true)); 1082 SpillIdxes.insert(std::make_pair(MBBId, S)); 1083 } else if (SII->second.back().vreg != NewVReg) { 1084 SII->second.push_back(SRInfo(index, NewVReg, true)); 1085 } else if ((int)index > SII->second.back().index) { 1086 // If there is an earlier def and this is a two-address 1087 // instruction, then it's not possible to fold the store (which 1088 // would also fold the load). 1089 SRInfo &Info = SII->second.back(); 1090 Info.index = index; 1091 Info.canFold = !HasUse; 1092 } 1093 SpillMBBs.set(MBBId); 1094 } else if (SII != SpillIdxes.end() && 1095 SII->second.back().vreg == NewVReg && 1096 (int)index > SII->second.back().index) { 1097 // There is an earlier def that's not killed (must be two-address). 1098 // The spill is no longer needed. 1099 SII->second.pop_back(); 1100 if (SII->second.empty()) { 1101 SpillIdxes.erase(MBBId); 1102 SpillMBBs.reset(MBBId); 1103 } 1104 } 1105 } 1106 } 1107 1108 if (HasUse) { 1109 std::map<unsigned, std::vector<SRInfo> >::iterator SII = 1110 SpillIdxes.find(MBBId); 1111 if (SII != SpillIdxes.end() && 1112 SII->second.back().vreg == NewVReg && 1113 (int)index > SII->second.back().index) 1114 // Use(s) following the last def, it's not safe to fold the spill. 1115 SII->second.back().canFold = false; 1116 std::map<unsigned, std::vector<SRInfo> >::iterator RII = 1117 RestoreIdxes.find(MBBId); 1118 if (RII != RestoreIdxes.end() && RII->second.back().vreg == NewVReg) 1119 // If we are splitting live intervals, only fold if it's the first 1120 // use and there isn't another use later in the MBB. 1121 RII->second.back().canFold = false; 1122 else if (IsNew) { 1123 // Only need a reload if there isn't an earlier def / use. 1124 if (RII == RestoreIdxes.end()) { 1125 std::vector<SRInfo> Infos; 1126 Infos.push_back(SRInfo(index, NewVReg, true)); 1127 RestoreIdxes.insert(std::make_pair(MBBId, Infos)); 1128 } else { 1129 RII->second.push_back(SRInfo(index, NewVReg, true)); 1130 } 1131 RestoreMBBs.set(MBBId); 1132 } 1133 } 1134 1135 // Update spill weight. 1136 unsigned loopDepth = loopInfo->getLoopDepth(MBB); 1137 nI.weight += getSpillWeight(HasDef, HasUse, loopDepth); 1138 } 1139 1140 if (NewVReg && TrySplit && AllCanFold) { 1141 // If all of its def / use can be folded, give it a low spill weight. 1142 LiveInterval &nI = getOrCreateInterval(NewVReg); 1143 nI.weight /= 10.0F; 1144 } 1145} 1146 1147bool LiveIntervals::alsoFoldARestore(int Id, int index, unsigned vr, 1148 BitVector &RestoreMBBs, 1149 std::map<unsigned,std::vector<SRInfo> > &RestoreIdxes) { 1150 if (!RestoreMBBs[Id]) 1151 return false; 1152 std::vector<SRInfo> &Restores = RestoreIdxes[Id]; 1153 for (unsigned i = 0, e = Restores.size(); i != e; ++i) 1154 if (Restores[i].index == index && 1155 Restores[i].vreg == vr && 1156 Restores[i].canFold) 1157 return true; 1158 return false; 1159} 1160 1161void LiveIntervals::eraseRestoreInfo(int Id, int index, unsigned vr, 1162 BitVector &RestoreMBBs, 1163 std::map<unsigned,std::vector<SRInfo> > &RestoreIdxes) { 1164 if (!RestoreMBBs[Id]) 1165 return; 1166 std::vector<SRInfo> &Restores = RestoreIdxes[Id]; 1167 for (unsigned i = 0, e = Restores.size(); i != e; ++i) 1168 if (Restores[i].index == index && Restores[i].vreg) 1169 Restores[i].index = -1; 1170} 1171 1172 1173std::vector<LiveInterval*> LiveIntervals:: 1174addIntervalsForSpills(const LiveInterval &li, 1175 const MachineLoopInfo *loopInfo, VirtRegMap &vrm) { 1176 // Since this is called after the analysis is done we don't know if 1177 // LiveVariables is available 1178 lv_ = getAnalysisToUpdate<LiveVariables>(); 1179 1180 assert(li.weight != HUGE_VALF && 1181 "attempt to spill already spilled interval!"); 1182 1183 DOUT << "\t\t\t\tadding intervals for spills for interval: "; 1184 li.print(DOUT, mri_); 1185 DOUT << '\n'; 1186 1187 // Each bit specify whether it a spill is required in the MBB. 1188 BitVector SpillMBBs(mf_->getNumBlockIDs()); 1189 std::map<unsigned, std::vector<SRInfo> > SpillIdxes; 1190 BitVector RestoreMBBs(mf_->getNumBlockIDs()); 1191 std::map<unsigned, std::vector<SRInfo> > RestoreIdxes; 1192 std::map<unsigned,unsigned> MBBVRegsMap; 1193 std::vector<LiveInterval*> NewLIs; 1194 MachineRegisterInfo &RegInfo = mf_->getRegInfo(); 1195 const TargetRegisterClass* rc = RegInfo.getRegClass(li.reg); 1196 1197 unsigned NumValNums = li.getNumValNums(); 1198 SmallVector<MachineInstr*, 4> ReMatDefs; 1199 ReMatDefs.resize(NumValNums, NULL); 1200 SmallVector<MachineInstr*, 4> ReMatOrigDefs; 1201 ReMatOrigDefs.resize(NumValNums, NULL); 1202 SmallVector<int, 4> ReMatIds; 1203 ReMatIds.resize(NumValNums, VirtRegMap::MAX_STACK_SLOT); 1204 BitVector ReMatDelete(NumValNums); 1205 unsigned Slot = VirtRegMap::MAX_STACK_SLOT; 1206 1207 // Spilling a split live interval. It cannot be split any further. Also, 1208 // it's also guaranteed to be a single val# / range interval. 1209 if (vrm.getPreSplitReg(li.reg)) { 1210 vrm.setIsSplitFromReg(li.reg, 0); 1211 // Unset the split kill marker on the last use. 1212 unsigned KillIdx = vrm.getKillPoint(li.reg); 1213 if (KillIdx) { 1214 MachineInstr *KillMI = getInstructionFromIndex(KillIdx); 1215 assert(KillMI && "Last use disappeared?"); 1216 int KillOp = KillMI->findRegisterUseOperandIdx(li.reg, true); 1217 assert(KillOp != -1 && "Last use disappeared?"); 1218 KillMI->getOperand(KillOp).setIsKill(false); 1219 } 1220 vrm.removeKillPoint(li.reg); 1221 bool DefIsReMat = vrm.isReMaterialized(li.reg); 1222 Slot = vrm.getStackSlot(li.reg); 1223 assert(Slot != VirtRegMap::MAX_STACK_SLOT); 1224 MachineInstr *ReMatDefMI = DefIsReMat ? 1225 vrm.getReMaterializedMI(li.reg) : NULL; 1226 int LdSlot = 0; 1227 bool isLoadSS = DefIsReMat && tii_->isLoadFromStackSlot(ReMatDefMI, LdSlot); 1228 bool isLoad = isLoadSS || 1229 (DefIsReMat && (ReMatDefMI->getDesc()->isSimpleLoad())); 1230 bool IsFirstRange = true; 1231 for (LiveInterval::Ranges::const_iterator 1232 I = li.ranges.begin(), E = li.ranges.end(); I != E; ++I) { 1233 // If this is a split live interval with multiple ranges, it means there 1234 // are two-address instructions that re-defined the value. Only the 1235 // first def can be rematerialized! 1236 if (IsFirstRange) { 1237 // Note ReMatOrigDefMI has already been deleted. 1238 rewriteInstructionsForSpills(li, false, I, NULL, ReMatDefMI, 1239 Slot, LdSlot, isLoad, isLoadSS, DefIsReMat, 1240 false, vrm, RegInfo, rc, ReMatIds, loopInfo, 1241 SpillMBBs, SpillIdxes, RestoreMBBs, RestoreIdxes, 1242 MBBVRegsMap, NewLIs); 1243 } else { 1244 rewriteInstructionsForSpills(li, false, I, NULL, 0, 1245 Slot, 0, false, false, false, 1246 false, vrm, RegInfo, rc, ReMatIds, loopInfo, 1247 SpillMBBs, SpillIdxes, RestoreMBBs, RestoreIdxes, 1248 MBBVRegsMap, NewLIs); 1249 } 1250 IsFirstRange = false; 1251 } 1252 return NewLIs; 1253 } 1254 1255 bool TrySplit = SplitAtBB && !intervalIsInOneMBB(li); 1256 if (SplitLimit != -1 && (int)numSplits >= SplitLimit) 1257 TrySplit = false; 1258 if (TrySplit) 1259 ++numSplits; 1260 bool NeedStackSlot = false; 1261 for (LiveInterval::const_vni_iterator i = li.vni_begin(), e = li.vni_end(); 1262 i != e; ++i) { 1263 const VNInfo *VNI = *i; 1264 unsigned VN = VNI->id; 1265 unsigned DefIdx = VNI->def; 1266 if (DefIdx == ~1U) 1267 continue; // Dead val#. 1268 // Is the def for the val# rematerializable? 1269 MachineInstr *ReMatDefMI = (DefIdx == ~0u) 1270 ? 0 : getInstructionFromIndex(DefIdx); 1271 bool dummy; 1272 if (ReMatDefMI && isReMaterializable(li, VNI, ReMatDefMI, dummy)) { 1273 // Remember how to remat the def of this val#. 1274 ReMatOrigDefs[VN] = ReMatDefMI; 1275 // Original def may be modified so we have to make a copy here. vrm must 1276 // delete these! 1277 ReMatDefs[VN] = ReMatDefMI = ReMatDefMI->clone(); 1278 1279 bool CanDelete = true; 1280 if (VNI->hasPHIKill) { 1281 // A kill is a phi node, not all of its uses can be rematerialized. 1282 // It must not be deleted. 1283 CanDelete = false; 1284 // Need a stack slot if there is any live range where uses cannot be 1285 // rematerialized. 1286 NeedStackSlot = true; 1287 } 1288 if (CanDelete) 1289 ReMatDelete.set(VN); 1290 } else { 1291 // Need a stack slot if there is any live range where uses cannot be 1292 // rematerialized. 1293 NeedStackSlot = true; 1294 } 1295 } 1296 1297 // One stack slot per live interval. 1298 if (NeedStackSlot && vrm.getPreSplitReg(li.reg) == 0) 1299 Slot = vrm.assignVirt2StackSlot(li.reg); 1300 1301 // Create new intervals and rewrite defs and uses. 1302 for (LiveInterval::Ranges::const_iterator 1303 I = li.ranges.begin(), E = li.ranges.end(); I != E; ++I) { 1304 MachineInstr *ReMatDefMI = ReMatDefs[I->valno->id]; 1305 MachineInstr *ReMatOrigDefMI = ReMatOrigDefs[I->valno->id]; 1306 bool DefIsReMat = ReMatDefMI != NULL; 1307 bool CanDelete = ReMatDelete[I->valno->id]; 1308 int LdSlot = 0; 1309 bool isLoadSS = DefIsReMat && tii_->isLoadFromStackSlot(ReMatDefMI, LdSlot); 1310 bool isLoad = isLoadSS || 1311 (DefIsReMat && ReMatDefMI->getDesc()->isSimpleLoad()); 1312 rewriteInstructionsForSpills(li, TrySplit, I, ReMatOrigDefMI, ReMatDefMI, 1313 Slot, LdSlot, isLoad, isLoadSS, DefIsReMat, 1314 CanDelete, vrm, RegInfo, rc, ReMatIds, loopInfo, 1315 SpillMBBs, SpillIdxes, RestoreMBBs, RestoreIdxes, 1316 MBBVRegsMap, NewLIs); 1317 } 1318 1319 // Insert spills / restores if we are splitting. 1320 if (!TrySplit) 1321 return NewLIs; 1322 1323 SmallPtrSet<LiveInterval*, 4> AddedKill; 1324 SmallVector<unsigned, 2> Ops; 1325 if (NeedStackSlot) { 1326 int Id = SpillMBBs.find_first(); 1327 while (Id != -1) { 1328 std::vector<SRInfo> &spills = SpillIdxes[Id]; 1329 for (unsigned i = 0, e = spills.size(); i != e; ++i) { 1330 int index = spills[i].index; 1331 unsigned VReg = spills[i].vreg; 1332 LiveInterval &nI = getOrCreateInterval(VReg); 1333 bool isReMat = vrm.isReMaterialized(VReg); 1334 MachineInstr *MI = getInstructionFromIndex(index); 1335 bool CanFold = false; 1336 bool FoundUse = false; 1337 Ops.clear(); 1338 if (spills[i].canFold) { 1339 CanFold = true; 1340 for (unsigned j = 0, ee = MI->getNumOperands(); j != ee; ++j) { 1341 MachineOperand &MO = MI->getOperand(j); 1342 if (!MO.isRegister() || MO.getReg() != VReg) 1343 continue; 1344 1345 Ops.push_back(j); 1346 if (MO.isDef()) 1347 continue; 1348 if (isReMat || 1349 (!FoundUse && !alsoFoldARestore(Id, index, VReg, 1350 RestoreMBBs, RestoreIdxes))) { 1351 // MI has two-address uses of the same register. If the use 1352 // isn't the first and only use in the BB, then we can't fold 1353 // it. FIXME: Move this to rewriteInstructionsForSpills. 1354 CanFold = false; 1355 break; 1356 } 1357 FoundUse = true; 1358 } 1359 } 1360 // Fold the store into the def if possible. 1361 bool Folded = false; 1362 if (CanFold && !Ops.empty()) { 1363 if (tryFoldMemoryOperand(MI, vrm, NULL, index, Ops, true, Slot,VReg)){ 1364 Folded = true; 1365 if (FoundUse > 0) { 1366 // Also folded uses, do not issue a load. 1367 eraseRestoreInfo(Id, index, VReg, RestoreMBBs, RestoreIdxes); 1368 nI.removeRange(getLoadIndex(index), getUseIndex(index)+1); 1369 } 1370 nI.removeRange(getDefIndex(index), getStoreIndex(index)); 1371 } 1372 } 1373 1374 // Else tell the spiller to issue a spill. 1375 if (!Folded) { 1376 LiveRange *LR = &nI.ranges[nI.ranges.size()-1]; 1377 bool isKill = LR->end == getStoreIndex(index); 1378 vrm.addSpillPoint(VReg, isKill, MI); 1379 if (isKill) 1380 AddedKill.insert(&nI); 1381 } 1382 } 1383 Id = SpillMBBs.find_next(Id); 1384 } 1385 } 1386 1387 int Id = RestoreMBBs.find_first(); 1388 while (Id != -1) { 1389 std::vector<SRInfo> &restores = RestoreIdxes[Id]; 1390 for (unsigned i = 0, e = restores.size(); i != e; ++i) { 1391 int index = restores[i].index; 1392 if (index == -1) 1393 continue; 1394 unsigned VReg = restores[i].vreg; 1395 LiveInterval &nI = getOrCreateInterval(VReg); 1396 MachineInstr *MI = getInstructionFromIndex(index); 1397 bool CanFold = false; 1398 Ops.clear(); 1399 if (restores[i].canFold) { 1400 CanFold = true; 1401 for (unsigned j = 0, ee = MI->getNumOperands(); j != ee; ++j) { 1402 MachineOperand &MO = MI->getOperand(j); 1403 if (!MO.isRegister() || MO.getReg() != VReg) 1404 continue; 1405 1406 if (MO.isDef()) { 1407 // If this restore were to be folded, it would have been folded 1408 // already. 1409 CanFold = false; 1410 break; 1411 } 1412 Ops.push_back(j); 1413 } 1414 } 1415 1416 // Fold the load into the use if possible. 1417 bool Folded = false; 1418 if (CanFold && !Ops.empty()) { 1419 if (!vrm.isReMaterialized(VReg)) 1420 Folded = tryFoldMemoryOperand(MI, vrm, NULL,index,Ops,true,Slot,VReg); 1421 else { 1422 MachineInstr *ReMatDefMI = vrm.getReMaterializedMI(VReg); 1423 int LdSlot = 0; 1424 bool isLoadSS = tii_->isLoadFromStackSlot(ReMatDefMI, LdSlot); 1425 // If the rematerializable def is a load, also try to fold it. 1426 if (isLoadSS || ReMatDefMI->getDesc()->isSimpleLoad()) 1427 Folded = tryFoldMemoryOperand(MI, vrm, ReMatDefMI, index, 1428 Ops, isLoadSS, LdSlot, VReg); 1429 } 1430 } 1431 // If folding is not possible / failed, then tell the spiller to issue a 1432 // load / rematerialization for us. 1433 if (Folded) 1434 nI.removeRange(getLoadIndex(index), getUseIndex(index)+1); 1435 else 1436 vrm.addRestorePoint(VReg, MI); 1437 } 1438 Id = RestoreMBBs.find_next(Id); 1439 } 1440 1441 // Finalize intervals: add kills, finalize spill weights, and filter out 1442 // dead intervals. 1443 std::vector<LiveInterval*> RetNewLIs; 1444 for (unsigned i = 0, e = NewLIs.size(); i != e; ++i) { 1445 LiveInterval *LI = NewLIs[i]; 1446 if (!LI->empty()) { 1447 LI->weight /= LI->getSize(); 1448 if (!AddedKill.count(LI)) { 1449 LiveRange *LR = &LI->ranges[LI->ranges.size()-1]; 1450 unsigned LastUseIdx = getBaseIndex(LR->end); 1451 MachineInstr *LastUse = getInstructionFromIndex(LastUseIdx); 1452 int UseIdx = LastUse->findRegisterUseOperandIdx(LI->reg); 1453 assert(UseIdx != -1); 1454 if (LastUse->getDesc()->getOperandConstraint(UseIdx, TOI::TIED_TO) == 1455 -1) { 1456 LastUse->getOperand(UseIdx).setIsKill(); 1457 vrm.addKillPoint(LI->reg, LastUseIdx); 1458 } 1459 } 1460 RetNewLIs.push_back(LI); 1461 } 1462 } 1463 1464 return RetNewLIs; 1465} 1466