MachineBasicBlock.cpp revision ddfd1377d2e4154d44dc3ad217735adc15af2e3f
1//===-- llvm/CodeGen/MachineBasicBlock.cpp ----------------------*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// Collect the sequence of machine instructions for a basic block. 11// 12//===----------------------------------------------------------------------===// 13 14#include "llvm/CodeGen/MachineBasicBlock.h" 15#include "llvm/BasicBlock.h" 16#include "llvm/CodeGen/LiveVariables.h" 17#include "llvm/CodeGen/MachineDominators.h" 18#include "llvm/CodeGen/MachineFunction.h" 19#include "llvm/CodeGen/MachineLoopInfo.h" 20#include "llvm/CodeGen/SlotIndexes.h" 21#include "llvm/MC/MCAsmInfo.h" 22#include "llvm/MC/MCContext.h" 23#include "llvm/Target/TargetRegisterInfo.h" 24#include "llvm/Target/TargetData.h" 25#include "llvm/Target/TargetInstrInfo.h" 26#include "llvm/Target/TargetMachine.h" 27#include "llvm/Assembly/Writer.h" 28#include "llvm/ADT/SmallString.h" 29#include "llvm/ADT/SmallPtrSet.h" 30#include "llvm/Support/Debug.h" 31#include "llvm/Support/LeakDetector.h" 32#include "llvm/Support/raw_ostream.h" 33#include <algorithm> 34using namespace llvm; 35 36MachineBasicBlock::MachineBasicBlock(MachineFunction &mf, const BasicBlock *bb) 37 : BB(bb), Number(-1), xParent(&mf), Alignment(0), IsLandingPad(false), 38 AddressTaken(false) { 39 Insts.Parent = this; 40} 41 42MachineBasicBlock::~MachineBasicBlock() { 43 LeakDetector::removeGarbageObject(this); 44} 45 46/// getSymbol - Return the MCSymbol for this basic block. 47/// 48MCSymbol *MachineBasicBlock::getSymbol() const { 49 const MachineFunction *MF = getParent(); 50 MCContext &Ctx = MF->getContext(); 51 const char *Prefix = Ctx.getAsmInfo().getPrivateGlobalPrefix(); 52 return Ctx.GetOrCreateSymbol(Twine(Prefix) + "BB" + 53 Twine(MF->getFunctionNumber()) + "_" + 54 Twine(getNumber())); 55} 56 57 58raw_ostream &llvm::operator<<(raw_ostream &OS, const MachineBasicBlock &MBB) { 59 MBB.print(OS); 60 return OS; 61} 62 63/// addNodeToList (MBB) - When an MBB is added to an MF, we need to update the 64/// parent pointer of the MBB, the MBB numbering, and any instructions in the 65/// MBB to be on the right operand list for registers. 66/// 67/// MBBs start out as #-1. When a MBB is added to a MachineFunction, it 68/// gets the next available unique MBB number. If it is removed from a 69/// MachineFunction, it goes back to being #-1. 70void ilist_traits<MachineBasicBlock>::addNodeToList(MachineBasicBlock *N) { 71 MachineFunction &MF = *N->getParent(); 72 N->Number = MF.addToMBBNumbering(N); 73 74 // Make sure the instructions have their operands in the reginfo lists. 75 MachineRegisterInfo &RegInfo = MF.getRegInfo(); 76 for (MachineBasicBlock::instr_iterator 77 I = N->instr_begin(), E = N->instr_end(); I != E; ++I) 78 I->AddRegOperandsToUseLists(RegInfo); 79 80 LeakDetector::removeGarbageObject(N); 81} 82 83void ilist_traits<MachineBasicBlock>::removeNodeFromList(MachineBasicBlock *N) { 84 N->getParent()->removeFromMBBNumbering(N->Number); 85 N->Number = -1; 86 LeakDetector::addGarbageObject(N); 87} 88 89 90/// addNodeToList (MI) - When we add an instruction to a basic block 91/// list, we update its parent pointer and add its operands from reg use/def 92/// lists if appropriate. 93void ilist_traits<MachineInstr>::addNodeToList(MachineInstr *N) { 94 assert(N->getParent() == 0 && "machine instruction already in a basic block"); 95 N->setParent(Parent); 96 97 // Add the instruction's register operands to their corresponding 98 // use/def lists. 99 MachineFunction *MF = Parent->getParent(); 100 N->AddRegOperandsToUseLists(MF->getRegInfo()); 101 102 LeakDetector::removeGarbageObject(N); 103} 104 105/// removeNodeFromList (MI) - When we remove an instruction from a basic block 106/// list, we update its parent pointer and remove its operands from reg use/def 107/// lists if appropriate. 108void ilist_traits<MachineInstr>::removeNodeFromList(MachineInstr *N) { 109 assert(N->getParent() != 0 && "machine instruction not in a basic block"); 110 111 // Remove from the use/def lists. 112 N->RemoveRegOperandsFromUseLists(); 113 114 N->setParent(0); 115 116 LeakDetector::addGarbageObject(N); 117} 118 119/// transferNodesFromList (MI) - When moving a range of instructions from one 120/// MBB list to another, we need to update the parent pointers and the use/def 121/// lists. 122void ilist_traits<MachineInstr>:: 123transferNodesFromList(ilist_traits<MachineInstr> &fromList, 124 ilist_iterator<MachineInstr> first, 125 ilist_iterator<MachineInstr> last) { 126 assert(Parent->getParent() == fromList.Parent->getParent() && 127 "MachineInstr parent mismatch!"); 128 129 // Splice within the same MBB -> no change. 130 if (Parent == fromList.Parent) return; 131 132 // If splicing between two blocks within the same function, just update the 133 // parent pointers. 134 for (; first != last; ++first) 135 first->setParent(Parent); 136} 137 138void ilist_traits<MachineInstr>::deleteNode(MachineInstr* MI) { 139 assert(!MI->getParent() && "MI is still in a block!"); 140 Parent->getParent()->DeleteMachineInstr(MI); 141} 142 143MachineBasicBlock::iterator MachineBasicBlock::getFirstNonPHI() { 144 instr_iterator I = instr_begin(); 145 while (I != end() && I->isPHI()) 146 ++I; 147 assert(!I->isInsideBundle() && "First non-phi MI cannot be inside a bundle!"); 148 return I; 149} 150 151MachineBasicBlock::iterator 152MachineBasicBlock::SkipPHIsAndLabels(MachineBasicBlock::iterator I) { 153 while (I != end() && (I->isPHI() || I->isLabel() || I->isDebugValue())) 154 ++I; 155 // FIXME: This needs to change if we wish to bundle labels / dbg_values 156 // inside the bundle. 157 assert(!I->isInsideBundle() && 158 "First non-phi / non-label instruction is inside a bundle!"); 159 return I; 160} 161 162MachineBasicBlock::iterator MachineBasicBlock::getFirstTerminator() { 163 iterator I = end(); 164 while (I != begin() && ((--I)->isTerminator() || I->isDebugValue())) 165 ; /*noop */ 166 while (I != end() && !I->isTerminator()) 167 ++I; 168 return I; 169} 170 171MachineBasicBlock::const_iterator 172MachineBasicBlock::getFirstTerminator() const { 173 const_iterator I = end(); 174 while (I != begin() && ((--I)->isTerminator() || I->isDebugValue())) 175 ; /*noop */ 176 while (I != end() && !I->isTerminator()) 177 ++I; 178 return I; 179} 180 181MachineBasicBlock::instr_iterator MachineBasicBlock::getFirstInstrTerminator() { 182 instr_iterator I = instr_end(); 183 while (I != instr_begin() && ((--I)->isTerminator() || I->isDebugValue())) 184 ; /*noop */ 185 while (I != instr_end() && !I->isTerminator()) 186 ++I; 187 return I; 188} 189 190MachineBasicBlock::iterator MachineBasicBlock::getLastNonDebugInstr() { 191 // Skip over end-of-block dbg_value instructions. 192 instr_iterator B = instr_begin(), I = instr_end(); 193 while (I != B) { 194 --I; 195 // Return instruction that starts a bundle. 196 if (I->isDebugValue() || I->isInsideBundle()) 197 continue; 198 return I; 199 } 200 // The block is all debug values. 201 return end(); 202} 203 204MachineBasicBlock::const_iterator 205MachineBasicBlock::getLastNonDebugInstr() const { 206 // Skip over end-of-block dbg_value instructions. 207 const_instr_iterator B = instr_begin(), I = instr_end(); 208 while (I != B) { 209 --I; 210 // Return instruction that starts a bundle. 211 if (I->isDebugValue() || I->isInsideBundle()) 212 continue; 213 return I; 214 } 215 // The block is all debug values. 216 return end(); 217} 218 219const MachineBasicBlock *MachineBasicBlock::getLandingPadSuccessor() const { 220 // A block with a landing pad successor only has one other successor. 221 if (succ_size() > 2) 222 return 0; 223 for (const_succ_iterator I = succ_begin(), E = succ_end(); I != E; ++I) 224 if ((*I)->isLandingPad()) 225 return *I; 226 return 0; 227} 228 229void MachineBasicBlock::dump() const { 230 print(dbgs()); 231} 232 233StringRef MachineBasicBlock::getName() const { 234 if (const BasicBlock *LBB = getBasicBlock()) 235 return LBB->getName(); 236 else 237 return "(null)"; 238} 239 240void MachineBasicBlock::print(raw_ostream &OS, SlotIndexes *Indexes) const { 241 const MachineFunction *MF = getParent(); 242 if (!MF) { 243 OS << "Can't print out MachineBasicBlock because parent MachineFunction" 244 << " is null\n"; 245 return; 246 } 247 248 if (Indexes) 249 OS << Indexes->getMBBStartIdx(this) << '\t'; 250 251 OS << "BB#" << getNumber() << ": "; 252 253 const char *Comma = ""; 254 if (const BasicBlock *LBB = getBasicBlock()) { 255 OS << Comma << "derived from LLVM BB "; 256 WriteAsOperand(OS, LBB, /*PrintType=*/false); 257 Comma = ", "; 258 } 259 if (isLandingPad()) { OS << Comma << "EH LANDING PAD"; Comma = ", "; } 260 if (hasAddressTaken()) { OS << Comma << "ADDRESS TAKEN"; Comma = ", "; } 261 if (Alignment) { 262 OS << Comma << "Align " << Alignment << " (" << (1u << Alignment) 263 << " bytes)"; 264 Comma = ", "; 265 } 266 267 OS << '\n'; 268 269 const TargetRegisterInfo *TRI = MF->getTarget().getRegisterInfo(); 270 if (!livein_empty()) { 271 if (Indexes) OS << '\t'; 272 OS << " Live Ins:"; 273 for (livein_iterator I = livein_begin(),E = livein_end(); I != E; ++I) 274 OS << ' ' << PrintReg(*I, TRI); 275 OS << '\n'; 276 } 277 // Print the preds of this block according to the CFG. 278 if (!pred_empty()) { 279 if (Indexes) OS << '\t'; 280 OS << " Predecessors according to CFG:"; 281 for (const_pred_iterator PI = pred_begin(), E = pred_end(); PI != E; ++PI) 282 OS << " BB#" << (*PI)->getNumber(); 283 OS << '\n'; 284 } 285 286 for (const_instr_iterator I = instr_begin(); I != instr_end(); ++I) { 287 if (Indexes) { 288 if (Indexes->hasIndex(I)) 289 OS << Indexes->getInstructionIndex(I); 290 OS << '\t'; 291 } 292 OS << '\t'; 293 if (I->isInsideBundle()) 294 OS << " * "; 295 I->print(OS, &getParent()->getTarget()); 296 } 297 298 // Print the successors of this block according to the CFG. 299 if (!succ_empty()) { 300 if (Indexes) OS << '\t'; 301 OS << " Successors according to CFG:"; 302 for (const_succ_iterator SI = succ_begin(), E = succ_end(); SI != E; ++SI) 303 OS << " BB#" << (*SI)->getNumber(); 304 OS << '\n'; 305 } 306} 307 308void MachineBasicBlock::removeLiveIn(unsigned Reg) { 309 std::vector<unsigned>::iterator I = 310 std::find(LiveIns.begin(), LiveIns.end(), Reg); 311 assert(I != LiveIns.end() && "Not a live in!"); 312 LiveIns.erase(I); 313} 314 315bool MachineBasicBlock::isLiveIn(unsigned Reg) const { 316 livein_iterator I = std::find(livein_begin(), livein_end(), Reg); 317 return I != livein_end(); 318} 319 320void MachineBasicBlock::moveBefore(MachineBasicBlock *NewAfter) { 321 getParent()->splice(NewAfter, this); 322} 323 324void MachineBasicBlock::moveAfter(MachineBasicBlock *NewBefore) { 325 MachineFunction::iterator BBI = NewBefore; 326 getParent()->splice(++BBI, this); 327} 328 329void MachineBasicBlock::updateTerminator() { 330 const TargetInstrInfo *TII = getParent()->getTarget().getInstrInfo(); 331 // A block with no successors has no concerns with fall-through edges. 332 if (this->succ_empty()) return; 333 334 MachineBasicBlock *TBB = 0, *FBB = 0; 335 SmallVector<MachineOperand, 4> Cond; 336 DebugLoc dl; // FIXME: this is nowhere 337 bool B = TII->AnalyzeBranch(*this, TBB, FBB, Cond); 338 (void) B; 339 assert(!B && "UpdateTerminators requires analyzable predecessors!"); 340 if (Cond.empty()) { 341 if (TBB) { 342 // The block has an unconditional branch. If its successor is now 343 // its layout successor, delete the branch. 344 if (isLayoutSuccessor(TBB)) 345 TII->RemoveBranch(*this); 346 } else { 347 // The block has an unconditional fallthrough. If its successor is not 348 // its layout successor, insert a branch. First we have to locate the 349 // only non-landing-pad successor, as that is the fallthrough block. 350 for (succ_iterator SI = succ_begin(), SE = succ_end(); SI != SE; ++SI) { 351 if ((*SI)->isLandingPad()) 352 continue; 353 assert(!TBB && "Found more than one non-landing-pad successor!"); 354 TBB = *SI; 355 } 356 357 // If there is no non-landing-pad successor, the block has no 358 // fall-through edges to be concerned with. 359 if (!TBB) 360 return; 361 362 // Finally update the unconditional successor to be reached via a branch 363 // if it would not be reached by fallthrough. 364 if (!isLayoutSuccessor(TBB)) 365 TII->InsertBranch(*this, TBB, 0, Cond, dl); 366 } 367 } else { 368 if (FBB) { 369 // The block has a non-fallthrough conditional branch. If one of its 370 // successors is its layout successor, rewrite it to a fallthrough 371 // conditional branch. 372 if (isLayoutSuccessor(TBB)) { 373 if (TII->ReverseBranchCondition(Cond)) 374 return; 375 TII->RemoveBranch(*this); 376 TII->InsertBranch(*this, FBB, 0, Cond, dl); 377 } else if (isLayoutSuccessor(FBB)) { 378 TII->RemoveBranch(*this); 379 TII->InsertBranch(*this, TBB, 0, Cond, dl); 380 } 381 } else { 382 // The block has a fallthrough conditional branch. 383 MachineBasicBlock *MBBA = *succ_begin(); 384 MachineBasicBlock *MBBB = *llvm::next(succ_begin()); 385 if (MBBA == TBB) std::swap(MBBB, MBBA); 386 if (isLayoutSuccessor(TBB)) { 387 if (TII->ReverseBranchCondition(Cond)) { 388 // We can't reverse the condition, add an unconditional branch. 389 Cond.clear(); 390 TII->InsertBranch(*this, MBBA, 0, Cond, dl); 391 return; 392 } 393 TII->RemoveBranch(*this); 394 TII->InsertBranch(*this, MBBA, 0, Cond, dl); 395 } else if (!isLayoutSuccessor(MBBA)) { 396 TII->RemoveBranch(*this); 397 TII->InsertBranch(*this, TBB, MBBA, Cond, dl); 398 } 399 } 400 } 401} 402 403void MachineBasicBlock::addSuccessor(MachineBasicBlock *succ, uint32_t weight) { 404 405 // If we see non-zero value for the first time it means we actually use Weight 406 // list, so we fill all Weights with 0's. 407 if (weight != 0 && Weights.empty()) 408 Weights.resize(Successors.size()); 409 410 if (weight != 0 || !Weights.empty()) 411 Weights.push_back(weight); 412 413 Successors.push_back(succ); 414 succ->addPredecessor(this); 415 } 416 417void MachineBasicBlock::removeSuccessor(MachineBasicBlock *succ) { 418 succ->removePredecessor(this); 419 succ_iterator I = std::find(Successors.begin(), Successors.end(), succ); 420 assert(I != Successors.end() && "Not a current successor!"); 421 422 // If Weight list is empty it means we don't use it (disabled optimization). 423 if (!Weights.empty()) { 424 weight_iterator WI = getWeightIterator(I); 425 Weights.erase(WI); 426 } 427 428 Successors.erase(I); 429} 430 431MachineBasicBlock::succ_iterator 432MachineBasicBlock::removeSuccessor(succ_iterator I) { 433 assert(I != Successors.end() && "Not a current successor!"); 434 435 // If Weight list is empty it means we don't use it (disabled optimization). 436 if (!Weights.empty()) { 437 weight_iterator WI = getWeightIterator(I); 438 Weights.erase(WI); 439 } 440 441 (*I)->removePredecessor(this); 442 return Successors.erase(I); 443} 444 445void MachineBasicBlock::replaceSuccessor(MachineBasicBlock *Old, 446 MachineBasicBlock *New) { 447 uint32_t weight = 0; 448 succ_iterator SI = std::find(Successors.begin(), Successors.end(), Old); 449 450 // If Weight list is empty it means we don't use it (disabled optimization). 451 if (!Weights.empty()) { 452 weight_iterator WI = getWeightIterator(SI); 453 weight = *WI; 454 } 455 456 // Update the successor information. 457 removeSuccessor(SI); 458 addSuccessor(New, weight); 459} 460 461void MachineBasicBlock::addPredecessor(MachineBasicBlock *pred) { 462 Predecessors.push_back(pred); 463} 464 465void MachineBasicBlock::removePredecessor(MachineBasicBlock *pred) { 466 pred_iterator I = std::find(Predecessors.begin(), Predecessors.end(), pred); 467 assert(I != Predecessors.end() && "Pred is not a predecessor of this block!"); 468 Predecessors.erase(I); 469} 470 471void MachineBasicBlock::transferSuccessors(MachineBasicBlock *fromMBB) { 472 if (this == fromMBB) 473 return; 474 475 while (!fromMBB->succ_empty()) { 476 MachineBasicBlock *Succ = *fromMBB->succ_begin(); 477 uint32_t weight = 0; 478 479 480 // If Weight list is empty it means we don't use it (disabled optimization). 481 if (!fromMBB->Weights.empty()) 482 weight = *fromMBB->Weights.begin(); 483 484 addSuccessor(Succ, weight); 485 fromMBB->removeSuccessor(Succ); 486 } 487} 488 489void 490MachineBasicBlock::transferSuccessorsAndUpdatePHIs(MachineBasicBlock *fromMBB) { 491 if (this == fromMBB) 492 return; 493 494 while (!fromMBB->succ_empty()) { 495 MachineBasicBlock *Succ = *fromMBB->succ_begin(); 496 addSuccessor(Succ); 497 fromMBB->removeSuccessor(Succ); 498 499 // Fix up any PHI nodes in the successor. 500 for (MachineBasicBlock::instr_iterator MI = Succ->instr_begin(), 501 ME = Succ->instr_end(); MI != ME && MI->isPHI(); ++MI) 502 for (unsigned i = 2, e = MI->getNumOperands()+1; i != e; i += 2) { 503 MachineOperand &MO = MI->getOperand(i); 504 if (MO.getMBB() == fromMBB) 505 MO.setMBB(this); 506 } 507 } 508} 509 510bool MachineBasicBlock::isSuccessor(const MachineBasicBlock *MBB) const { 511 const_succ_iterator I = std::find(Successors.begin(), Successors.end(), MBB); 512 return I != Successors.end(); 513} 514 515bool MachineBasicBlock::isLayoutSuccessor(const MachineBasicBlock *MBB) const { 516 MachineFunction::const_iterator I(this); 517 return llvm::next(I) == MachineFunction::const_iterator(MBB); 518} 519 520bool MachineBasicBlock::canFallThrough() { 521 MachineFunction::iterator Fallthrough = this; 522 ++Fallthrough; 523 // If FallthroughBlock is off the end of the function, it can't fall through. 524 if (Fallthrough == getParent()->end()) 525 return false; 526 527 // If FallthroughBlock isn't a successor, no fallthrough is possible. 528 if (!isSuccessor(Fallthrough)) 529 return false; 530 531 // Analyze the branches, if any, at the end of the block. 532 MachineBasicBlock *TBB = 0, *FBB = 0; 533 SmallVector<MachineOperand, 4> Cond; 534 const TargetInstrInfo *TII = getParent()->getTarget().getInstrInfo(); 535 if (TII->AnalyzeBranch(*this, TBB, FBB, Cond)) { 536 // If we couldn't analyze the branch, examine the last instruction. 537 // If the block doesn't end in a known control barrier, assume fallthrough 538 // is possible. The isPredicable check is needed because this code can be 539 // called during IfConversion, where an instruction which is normally a 540 // Barrier is predicated and thus no longer an actual control barrier. This 541 // is over-conservative though, because if an instruction isn't actually 542 // predicated we could still treat it like a barrier. 543 return empty() || !back().isBarrier() || 544 back().isPredicable(); 545 } 546 547 // If there is no branch, control always falls through. 548 if (TBB == 0) return true; 549 550 // If there is some explicit branch to the fallthrough block, it can obviously 551 // reach, even though the branch should get folded to fall through implicitly. 552 if (MachineFunction::iterator(TBB) == Fallthrough || 553 MachineFunction::iterator(FBB) == Fallthrough) 554 return true; 555 556 // If it's an unconditional branch to some block not the fall through, it 557 // doesn't fall through. 558 if (Cond.empty()) return false; 559 560 // Otherwise, if it is conditional and has no explicit false block, it falls 561 // through. 562 return FBB == 0; 563} 564 565MachineBasicBlock * 566MachineBasicBlock::SplitCriticalEdge(MachineBasicBlock *Succ, Pass *P) { 567 MachineFunction *MF = getParent(); 568 DebugLoc dl; // FIXME: this is nowhere 569 570 // We may need to update this's terminator, but we can't do that if 571 // AnalyzeBranch fails. If this uses a jump table, we won't touch it. 572 const TargetInstrInfo *TII = MF->getTarget().getInstrInfo(); 573 MachineBasicBlock *TBB = 0, *FBB = 0; 574 SmallVector<MachineOperand, 4> Cond; 575 if (TII->AnalyzeBranch(*this, TBB, FBB, Cond)) 576 return NULL; 577 578 // Avoid bugpoint weirdness: A block may end with a conditional branch but 579 // jumps to the same MBB is either case. We have duplicate CFG edges in that 580 // case that we can't handle. Since this never happens in properly optimized 581 // code, just skip those edges. 582 if (TBB && TBB == FBB) { 583 DEBUG(dbgs() << "Won't split critical edge after degenerate BB#" 584 << getNumber() << '\n'); 585 return NULL; 586 } 587 588 MachineBasicBlock *NMBB = MF->CreateMachineBasicBlock(); 589 MF->insert(llvm::next(MachineFunction::iterator(this)), NMBB); 590 DEBUG(dbgs() << "Splitting critical edge:" 591 " BB#" << getNumber() 592 << " -- BB#" << NMBB->getNumber() 593 << " -- BB#" << Succ->getNumber() << '\n'); 594 595 // On some targets like Mips, branches may kill virtual registers. Make sure 596 // that LiveVariables is properly updated after updateTerminator replaces the 597 // terminators. 598 LiveVariables *LV = P->getAnalysisIfAvailable<LiveVariables>(); 599 600 // Collect a list of virtual registers killed by the terminators. 601 SmallVector<unsigned, 4> KilledRegs; 602 if (LV) 603 for (instr_iterator I = getFirstInstrTerminator(), E = instr_end(); 604 I != E; ++I) { 605 MachineInstr *MI = I; 606 for (MachineInstr::mop_iterator OI = MI->operands_begin(), 607 OE = MI->operands_end(); OI != OE; ++OI) { 608 if (!OI->isReg() || !OI->isUse() || !OI->isKill() || OI->isUndef()) 609 continue; 610 unsigned Reg = OI->getReg(); 611 if (TargetRegisterInfo::isVirtualRegister(Reg) && 612 LV->getVarInfo(Reg).removeKill(MI)) { 613 KilledRegs.push_back(Reg); 614 DEBUG(dbgs() << "Removing terminator kill: " << *MI); 615 OI->setIsKill(false); 616 } 617 } 618 } 619 620 ReplaceUsesOfBlockWith(Succ, NMBB); 621 updateTerminator(); 622 623 // Insert unconditional "jump Succ" instruction in NMBB if necessary. 624 NMBB->addSuccessor(Succ); 625 if (!NMBB->isLayoutSuccessor(Succ)) { 626 Cond.clear(); 627 MF->getTarget().getInstrInfo()->InsertBranch(*NMBB, Succ, NULL, Cond, dl); 628 } 629 630 // Fix PHI nodes in Succ so they refer to NMBB instead of this 631 for (MachineBasicBlock::instr_iterator 632 i = Succ->instr_begin(),e = Succ->instr_end(); 633 i != e && i->isPHI(); ++i) 634 for (unsigned ni = 1, ne = i->getNumOperands(); ni != ne; ni += 2) 635 if (i->getOperand(ni+1).getMBB() == this) 636 i->getOperand(ni+1).setMBB(NMBB); 637 638 // Inherit live-ins from the successor 639 for (MachineBasicBlock::livein_iterator I = Succ->livein_begin(), 640 E = Succ->livein_end(); I != E; ++I) 641 NMBB->addLiveIn(*I); 642 643 // Update LiveVariables. 644 if (LV) { 645 // Restore kills of virtual registers that were killed by the terminators. 646 while (!KilledRegs.empty()) { 647 unsigned Reg = KilledRegs.pop_back_val(); 648 for (instr_iterator I = instr_end(), E = instr_begin(); I != E;) { 649 if (!(--I)->addRegisterKilled(Reg, NULL, /* addIfNotFound= */ false)) 650 continue; 651 LV->getVarInfo(Reg).Kills.push_back(I); 652 DEBUG(dbgs() << "Restored terminator kill: " << *I); 653 break; 654 } 655 } 656 // Update relevant live-through information. 657 LV->addNewBlock(NMBB, this, Succ); 658 } 659 660 if (MachineDominatorTree *MDT = 661 P->getAnalysisIfAvailable<MachineDominatorTree>()) { 662 // Update dominator information. 663 MachineDomTreeNode *SucccDTNode = MDT->getNode(Succ); 664 665 bool IsNewIDom = true; 666 for (const_pred_iterator PI = Succ->pred_begin(), E = Succ->pred_end(); 667 PI != E; ++PI) { 668 MachineBasicBlock *PredBB = *PI; 669 if (PredBB == NMBB) 670 continue; 671 if (!MDT->dominates(SucccDTNode, MDT->getNode(PredBB))) { 672 IsNewIDom = false; 673 break; 674 } 675 } 676 677 // We know "this" dominates the newly created basic block. 678 MachineDomTreeNode *NewDTNode = MDT->addNewBlock(NMBB, this); 679 680 // If all the other predecessors of "Succ" are dominated by "Succ" itself 681 // then the new block is the new immediate dominator of "Succ". Otherwise, 682 // the new block doesn't dominate anything. 683 if (IsNewIDom) 684 MDT->changeImmediateDominator(SucccDTNode, NewDTNode); 685 } 686 687 if (MachineLoopInfo *MLI = P->getAnalysisIfAvailable<MachineLoopInfo>()) 688 if (MachineLoop *TIL = MLI->getLoopFor(this)) { 689 // If one or the other blocks were not in a loop, the new block is not 690 // either, and thus LI doesn't need to be updated. 691 if (MachineLoop *DestLoop = MLI->getLoopFor(Succ)) { 692 if (TIL == DestLoop) { 693 // Both in the same loop, the NMBB joins loop. 694 DestLoop->addBasicBlockToLoop(NMBB, MLI->getBase()); 695 } else if (TIL->contains(DestLoop)) { 696 // Edge from an outer loop to an inner loop. Add to the outer loop. 697 TIL->addBasicBlockToLoop(NMBB, MLI->getBase()); 698 } else if (DestLoop->contains(TIL)) { 699 // Edge from an inner loop to an outer loop. Add to the outer loop. 700 DestLoop->addBasicBlockToLoop(NMBB, MLI->getBase()); 701 } else { 702 // Edge from two loops with no containment relation. Because these 703 // are natural loops, we know that the destination block must be the 704 // header of its loop (adding a branch into a loop elsewhere would 705 // create an irreducible loop). 706 assert(DestLoop->getHeader() == Succ && 707 "Should not create irreducible loops!"); 708 if (MachineLoop *P = DestLoop->getParentLoop()) 709 P->addBasicBlockToLoop(NMBB, MLI->getBase()); 710 } 711 } 712 } 713 714 return NMBB; 715} 716 717MachineBasicBlock::iterator 718MachineBasicBlock::erase(MachineBasicBlock::iterator I) { 719 if (I->isBundle()) { 720 MachineBasicBlock::iterator E = llvm::next(I); 721 return Insts.erase(I.getInstrIterator(), E.getInstrIterator()); 722 } 723 724 return Insts.erase(I.getInstrIterator()); 725} 726 727MachineInstr *MachineBasicBlock::remove(MachineInstr *I) { 728 if (I->isBundle()) { 729 MachineBasicBlock::instr_iterator MII = I; ++MII; 730 while (MII != end() && MII->isInsideBundle()) { 731 MachineInstr *MI = &*MII++; 732 Insts.remove(MI); 733 } 734 } 735 736 return Insts.remove(I); 737} 738 739void MachineBasicBlock::splice(MachineBasicBlock::iterator where, 740 MachineBasicBlock *Other, 741 MachineBasicBlock::iterator From) { 742 if (From->isBundle()) { 743 MachineBasicBlock::iterator To = llvm::next(From); 744 Insts.splice(where.getInstrIterator(), Other->Insts, 745 From.getInstrIterator(), To.getInstrIterator()); 746 return; 747 } 748 749 Insts.splice(where.getInstrIterator(), Other->Insts, From.getInstrIterator()); 750} 751 752/// removeFromParent - This method unlinks 'this' from the containing function, 753/// and returns it, but does not delete it. 754MachineBasicBlock *MachineBasicBlock::removeFromParent() { 755 assert(getParent() && "Not embedded in a function!"); 756 getParent()->remove(this); 757 return this; 758} 759 760 761/// eraseFromParent - This method unlinks 'this' from the containing function, 762/// and deletes it. 763void MachineBasicBlock::eraseFromParent() { 764 assert(getParent() && "Not embedded in a function!"); 765 getParent()->erase(this); 766} 767 768 769/// ReplaceUsesOfBlockWith - Given a machine basic block that branched to 770/// 'Old', change the code and CFG so that it branches to 'New' instead. 771void MachineBasicBlock::ReplaceUsesOfBlockWith(MachineBasicBlock *Old, 772 MachineBasicBlock *New) { 773 assert(Old != New && "Cannot replace self with self!"); 774 775 MachineBasicBlock::instr_iterator I = instr_end(); 776 while (I != instr_begin()) { 777 --I; 778 if (!I->isTerminator()) break; 779 780 // Scan the operands of this machine instruction, replacing any uses of Old 781 // with New. 782 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) 783 if (I->getOperand(i).isMBB() && 784 I->getOperand(i).getMBB() == Old) 785 I->getOperand(i).setMBB(New); 786 } 787 788 // Update the successor information. 789 replaceSuccessor(Old, New); 790} 791 792/// CorrectExtraCFGEdges - Various pieces of code can cause excess edges in the 793/// CFG to be inserted. If we have proven that MBB can only branch to DestA and 794/// DestB, remove any other MBB successors from the CFG. DestA and DestB can be 795/// null. 796/// 797/// Besides DestA and DestB, retain other edges leading to LandingPads 798/// (currently there can be only one; we don't check or require that here). 799/// Note it is possible that DestA and/or DestB are LandingPads. 800bool MachineBasicBlock::CorrectExtraCFGEdges(MachineBasicBlock *DestA, 801 MachineBasicBlock *DestB, 802 bool isCond) { 803 // The values of DestA and DestB frequently come from a call to the 804 // 'TargetInstrInfo::AnalyzeBranch' method. We take our meaning of the initial 805 // values from there. 806 // 807 // 1. If both DestA and DestB are null, then the block ends with no branches 808 // (it falls through to its successor). 809 // 2. If DestA is set, DestB is null, and isCond is false, then the block ends 810 // with only an unconditional branch. 811 // 3. If DestA is set, DestB is null, and isCond is true, then the block ends 812 // with a conditional branch that falls through to a successor (DestB). 813 // 4. If DestA and DestB is set and isCond is true, then the block ends with a 814 // conditional branch followed by an unconditional branch. DestA is the 815 // 'true' destination and DestB is the 'false' destination. 816 817 bool Changed = false; 818 819 MachineFunction::iterator FallThru = 820 llvm::next(MachineFunction::iterator(this)); 821 822 if (DestA == 0 && DestB == 0) { 823 // Block falls through to successor. 824 DestA = FallThru; 825 DestB = FallThru; 826 } else if (DestA != 0 && DestB == 0) { 827 if (isCond) 828 // Block ends in conditional jump that falls through to successor. 829 DestB = FallThru; 830 } else { 831 assert(DestA && DestB && isCond && 832 "CFG in a bad state. Cannot correct CFG edges"); 833 } 834 835 // Remove superfluous edges. I.e., those which aren't destinations of this 836 // basic block, duplicate edges, or landing pads. 837 SmallPtrSet<const MachineBasicBlock*, 8> SeenMBBs; 838 MachineBasicBlock::succ_iterator SI = succ_begin(); 839 while (SI != succ_end()) { 840 const MachineBasicBlock *MBB = *SI; 841 if (!SeenMBBs.insert(MBB) || 842 (MBB != DestA && MBB != DestB && !MBB->isLandingPad())) { 843 // This is a superfluous edge, remove it. 844 SI = removeSuccessor(SI); 845 Changed = true; 846 } else { 847 ++SI; 848 } 849 } 850 851 return Changed; 852} 853 854/// findDebugLoc - find the next valid DebugLoc starting at MBBI, skipping 855/// any DBG_VALUE instructions. Return UnknownLoc if there is none. 856DebugLoc 857MachineBasicBlock::findDebugLoc(instr_iterator MBBI) { 858 DebugLoc DL; 859 instr_iterator E = instr_end(); 860 if (MBBI == E) 861 return DL; 862 863 // Skip debug declarations, we don't want a DebugLoc from them. 864 while (MBBI != E && MBBI->isDebugValue()) 865 MBBI++; 866 if (MBBI != E) 867 DL = MBBI->getDebugLoc(); 868 return DL; 869} 870 871/// getSuccWeight - Return weight of the edge from this block to MBB. 872/// 873uint32_t MachineBasicBlock::getSuccWeight(MachineBasicBlock *succ) { 874 if (Weights.empty()) 875 return 0; 876 877 succ_iterator I = std::find(Successors.begin(), Successors.end(), succ); 878 return *getWeightIterator(I); 879} 880 881/// getWeightIterator - Return wight iterator corresonding to the I successor 882/// iterator 883MachineBasicBlock::weight_iterator MachineBasicBlock:: 884getWeightIterator(MachineBasicBlock::succ_iterator I) { 885 assert(Weights.size() == Successors.size() && "Async weight list!"); 886 size_t index = std::distance(Successors.begin(), I); 887 assert(index < Weights.size() && "Not a current successor!"); 888 return Weights.begin() + index; 889} 890 891void llvm::WriteAsOperand(raw_ostream &OS, const MachineBasicBlock *MBB, 892 bool t) { 893 OS << "BB#" << MBB->getNumber(); 894} 895 896