MachineBasicBlock.cpp revision e008384508342a2dec110eafaa87d93614976990
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/MC/MCAsmInfo.h" 21#include "llvm/MC/MCContext.h" 22#include "llvm/Target/TargetRegisterInfo.h" 23#include "llvm/Target/TargetData.h" 24#include "llvm/Target/TargetInstrDesc.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::iterator I = N->begin(), E = N->end(); I != E; ++I) 77 I->AddRegOperandsToUseLists(RegInfo); 78 79 LeakDetector::removeGarbageObject(N); 80} 81 82void ilist_traits<MachineBasicBlock>::removeNodeFromList(MachineBasicBlock *N) { 83 N->getParent()->removeFromMBBNumbering(N->Number); 84 N->Number = -1; 85 LeakDetector::addGarbageObject(N); 86} 87 88 89/// addNodeToList (MI) - When we add an instruction to a basic block 90/// list, we update its parent pointer and add its operands from reg use/def 91/// lists if appropriate. 92void ilist_traits<MachineInstr>::addNodeToList(MachineInstr *N) { 93 assert(N->getParent() == 0 && "machine instruction already in a basic block"); 94 N->setParent(Parent); 95 96 // Add the instruction's register operands to their corresponding 97 // use/def lists. 98 MachineFunction *MF = Parent->getParent(); 99 N->AddRegOperandsToUseLists(MF->getRegInfo()); 100 101 LeakDetector::removeGarbageObject(N); 102} 103 104/// removeNodeFromList (MI) - When we remove an instruction from a basic block 105/// list, we update its parent pointer and remove its operands from reg use/def 106/// lists if appropriate. 107void ilist_traits<MachineInstr>::removeNodeFromList(MachineInstr *N) { 108 assert(N->getParent() != 0 && "machine instruction not in a basic block"); 109 110 // Remove from the use/def lists. 111 N->RemoveRegOperandsFromUseLists(); 112 113 N->setParent(0); 114 115 LeakDetector::addGarbageObject(N); 116} 117 118/// transferNodesFromList (MI) - When moving a range of instructions from one 119/// MBB list to another, we need to update the parent pointers and the use/def 120/// lists. 121void ilist_traits<MachineInstr>:: 122transferNodesFromList(ilist_traits<MachineInstr> &fromList, 123 MachineBasicBlock::iterator first, 124 MachineBasicBlock::iterator last) { 125 assert(Parent->getParent() == fromList.Parent->getParent() && 126 "MachineInstr parent mismatch!"); 127 128 // Splice within the same MBB -> no change. 129 if (Parent == fromList.Parent) return; 130 131 // If splicing between two blocks within the same function, just update the 132 // parent pointers. 133 for (; first != last; ++first) 134 first->setParent(Parent); 135} 136 137void ilist_traits<MachineInstr>::deleteNode(MachineInstr* MI) { 138 assert(!MI->getParent() && "MI is still in a block!"); 139 Parent->getParent()->DeleteMachineInstr(MI); 140} 141 142MachineBasicBlock::iterator MachineBasicBlock::getFirstNonPHI() { 143 iterator I = begin(); 144 while (I != end() && I->isPHI()) 145 ++I; 146 return I; 147} 148 149MachineBasicBlock::iterator MachineBasicBlock::getFirstTerminator() { 150 iterator I = end(); 151 while (I != begin() && (--I)->getDesc().isTerminator()) 152 ; /*noop */ 153 if (I != end() && !I->getDesc().isTerminator()) ++I; 154 return I; 155} 156 157void MachineBasicBlock::dump() const { 158 print(dbgs()); 159} 160 161static inline void OutputReg(raw_ostream &os, unsigned RegNo, 162 const TargetRegisterInfo *TRI = 0) { 163 if (RegNo != 0 && TargetRegisterInfo::isPhysicalRegister(RegNo)) { 164 if (TRI) 165 os << " %" << TRI->get(RegNo).Name; 166 else 167 os << " %physreg" << RegNo; 168 } else 169 os << " %reg" << RegNo; 170} 171 172StringRef MachineBasicBlock::getName() const { 173 if (const BasicBlock *LBB = getBasicBlock()) 174 return LBB->getName(); 175 else 176 return "(null)"; 177} 178 179void MachineBasicBlock::print(raw_ostream &OS) const { 180 const MachineFunction *MF = getParent(); 181 if (!MF) { 182 OS << "Can't print out MachineBasicBlock because parent MachineFunction" 183 << " is null\n"; 184 return; 185 } 186 187 if (Alignment) { OS << "Alignment " << Alignment << "\n"; } 188 189 OS << "BB#" << getNumber() << ": "; 190 191 const char *Comma = ""; 192 if (const BasicBlock *LBB = getBasicBlock()) { 193 OS << Comma << "derived from LLVM BB "; 194 WriteAsOperand(OS, LBB, /*PrintType=*/false); 195 Comma = ", "; 196 } 197 if (isLandingPad()) { OS << Comma << "EH LANDING PAD"; Comma = ", "; } 198 if (hasAddressTaken()) { OS << Comma << "ADDRESS TAKEN"; Comma = ", "; } 199 OS << '\n'; 200 201 const TargetRegisterInfo *TRI = MF->getTarget().getRegisterInfo(); 202 if (!livein_empty()) { 203 OS << " Live Ins:"; 204 for (livein_iterator I = livein_begin(),E = livein_end(); I != E; ++I) 205 OutputReg(OS, *I, TRI); 206 OS << '\n'; 207 } 208 // Print the preds of this block according to the CFG. 209 if (!pred_empty()) { 210 OS << " Predecessors according to CFG:"; 211 for (const_pred_iterator PI = pred_begin(), E = pred_end(); PI != E; ++PI) 212 OS << " BB#" << (*PI)->getNumber(); 213 OS << '\n'; 214 } 215 216 for (const_iterator I = begin(); I != end(); ++I) { 217 OS << '\t'; 218 I->print(OS, &getParent()->getTarget()); 219 } 220 221 // Print the successors of this block according to the CFG. 222 if (!succ_empty()) { 223 OS << " Successors according to CFG:"; 224 for (const_succ_iterator SI = succ_begin(), E = succ_end(); SI != E; ++SI) 225 OS << " BB#" << (*SI)->getNumber(); 226 OS << '\n'; 227 } 228} 229 230void MachineBasicBlock::removeLiveIn(unsigned Reg) { 231 std::vector<unsigned>::iterator I = 232 std::find(LiveIns.begin(), LiveIns.end(), Reg); 233 assert(I != LiveIns.end() && "Not a live in!"); 234 LiveIns.erase(I); 235} 236 237bool MachineBasicBlock::isLiveIn(unsigned Reg) const { 238 livein_iterator I = std::find(livein_begin(), livein_end(), Reg); 239 return I != livein_end(); 240} 241 242void MachineBasicBlock::moveBefore(MachineBasicBlock *NewAfter) { 243 getParent()->splice(NewAfter, this); 244} 245 246void MachineBasicBlock::moveAfter(MachineBasicBlock *NewBefore) { 247 MachineFunction::iterator BBI = NewBefore; 248 getParent()->splice(++BBI, this); 249} 250 251void MachineBasicBlock::updateTerminator() { 252 const TargetInstrInfo *TII = getParent()->getTarget().getInstrInfo(); 253 // A block with no successors has no concerns with fall-through edges. 254 if (this->succ_empty()) return; 255 256 MachineBasicBlock *TBB = 0, *FBB = 0; 257 SmallVector<MachineOperand, 4> Cond; 258 DebugLoc dl; // FIXME: this is nowhere 259 bool B = TII->AnalyzeBranch(*this, TBB, FBB, Cond); 260 (void) B; 261 assert(!B && "UpdateTerminators requires analyzable predecessors!"); 262 if (Cond.empty()) { 263 if (TBB) { 264 // The block has an unconditional branch. If its successor is now 265 // its layout successor, delete the branch. 266 if (isLayoutSuccessor(TBB)) 267 TII->RemoveBranch(*this); 268 } else { 269 // The block has an unconditional fallthrough. If its successor is not 270 // its layout successor, insert a branch. 271 TBB = *succ_begin(); 272 if (!isLayoutSuccessor(TBB)) 273 TII->InsertBranch(*this, TBB, 0, Cond, dl); 274 } 275 } else { 276 if (FBB) { 277 // The block has a non-fallthrough conditional branch. If one of its 278 // successors is its layout successor, rewrite it to a fallthrough 279 // conditional branch. 280 if (isLayoutSuccessor(TBB)) { 281 if (TII->ReverseBranchCondition(Cond)) 282 return; 283 TII->RemoveBranch(*this); 284 TII->InsertBranch(*this, FBB, 0, Cond, dl); 285 } else if (isLayoutSuccessor(FBB)) { 286 TII->RemoveBranch(*this); 287 TII->InsertBranch(*this, TBB, 0, Cond, dl); 288 } 289 } else { 290 // The block has a fallthrough conditional branch. 291 MachineBasicBlock *MBBA = *succ_begin(); 292 MachineBasicBlock *MBBB = *llvm::next(succ_begin()); 293 if (MBBA == TBB) std::swap(MBBB, MBBA); 294 if (isLayoutSuccessor(TBB)) { 295 if (TII->ReverseBranchCondition(Cond)) { 296 // We can't reverse the condition, add an unconditional branch. 297 Cond.clear(); 298 TII->InsertBranch(*this, MBBA, 0, Cond, dl); 299 return; 300 } 301 TII->RemoveBranch(*this); 302 TII->InsertBranch(*this, MBBA, 0, Cond, dl); 303 } else if (!isLayoutSuccessor(MBBA)) { 304 TII->RemoveBranch(*this); 305 TII->InsertBranch(*this, TBB, MBBA, Cond, dl); 306 } 307 } 308 } 309} 310 311void MachineBasicBlock::addSuccessor(MachineBasicBlock *succ) { 312 Successors.push_back(succ); 313 succ->addPredecessor(this); 314} 315 316void MachineBasicBlock::removeSuccessor(MachineBasicBlock *succ) { 317 succ->removePredecessor(this); 318 succ_iterator I = std::find(Successors.begin(), Successors.end(), succ); 319 assert(I != Successors.end() && "Not a current successor!"); 320 Successors.erase(I); 321} 322 323MachineBasicBlock::succ_iterator 324MachineBasicBlock::removeSuccessor(succ_iterator I) { 325 assert(I != Successors.end() && "Not a current successor!"); 326 (*I)->removePredecessor(this); 327 return Successors.erase(I); 328} 329 330void MachineBasicBlock::addPredecessor(MachineBasicBlock *pred) { 331 Predecessors.push_back(pred); 332} 333 334void MachineBasicBlock::removePredecessor(MachineBasicBlock *pred) { 335 std::vector<MachineBasicBlock *>::iterator I = 336 std::find(Predecessors.begin(), Predecessors.end(), pred); 337 assert(I != Predecessors.end() && "Pred is not a predecessor of this block!"); 338 Predecessors.erase(I); 339} 340 341void MachineBasicBlock::transferSuccessors(MachineBasicBlock *fromMBB) { 342 if (this == fromMBB) 343 return; 344 345 while (!fromMBB->succ_empty()) { 346 MachineBasicBlock *Succ = *fromMBB->succ_begin(); 347 addSuccessor(Succ); 348 fromMBB->removeSuccessor(Succ); 349 } 350} 351 352void 353MachineBasicBlock::transferSuccessorsAndUpdatePHIs(MachineBasicBlock *fromMBB) { 354 if (this == fromMBB) 355 return; 356 357 while (!fromMBB->succ_empty()) { 358 MachineBasicBlock *Succ = *fromMBB->succ_begin(); 359 addSuccessor(Succ); 360 fromMBB->removeSuccessor(Succ); 361 362 // Fix up any PHI nodes in the successor. 363 for (MachineBasicBlock::iterator MI = Succ->begin(), ME = Succ->end(); 364 MI != ME && MI->isPHI(); ++MI) 365 for (unsigned i = 2, e = MI->getNumOperands()+1; i != e; i += 2) { 366 MachineOperand &MO = MI->getOperand(i); 367 if (MO.getMBB() == fromMBB) 368 MO.setMBB(this); 369 } 370 } 371} 372 373bool MachineBasicBlock::isSuccessor(const MachineBasicBlock *MBB) const { 374 std::vector<MachineBasicBlock *>::const_iterator I = 375 std::find(Successors.begin(), Successors.end(), MBB); 376 return I != Successors.end(); 377} 378 379bool MachineBasicBlock::isLayoutSuccessor(const MachineBasicBlock *MBB) const { 380 MachineFunction::const_iterator I(this); 381 return llvm::next(I) == MachineFunction::const_iterator(MBB); 382} 383 384bool MachineBasicBlock::canFallThrough() { 385 MachineFunction::iterator Fallthrough = this; 386 ++Fallthrough; 387 // If FallthroughBlock is off the end of the function, it can't fall through. 388 if (Fallthrough == getParent()->end()) 389 return false; 390 391 // If FallthroughBlock isn't a successor, no fallthrough is possible. 392 if (!isSuccessor(Fallthrough)) 393 return false; 394 395 // Analyze the branches, if any, at the end of the block. 396 MachineBasicBlock *TBB = 0, *FBB = 0; 397 SmallVector<MachineOperand, 4> Cond; 398 const TargetInstrInfo *TII = getParent()->getTarget().getInstrInfo(); 399 if (TII->AnalyzeBranch(*this, TBB, FBB, Cond)) { 400 // If we couldn't analyze the branch, examine the last instruction. 401 // If the block doesn't end in a known control barrier, assume fallthrough 402 // is possible. The isPredicable check is needed because this code can be 403 // called during IfConversion, where an instruction which is normally a 404 // Barrier is predicated and thus no longer an actual control barrier. This 405 // is over-conservative though, because if an instruction isn't actually 406 // predicated we could still treat it like a barrier. 407 return empty() || !back().getDesc().isBarrier() || 408 back().getDesc().isPredicable(); 409 } 410 411 // If there is no branch, control always falls through. 412 if (TBB == 0) return true; 413 414 // If there is some explicit branch to the fallthrough block, it can obviously 415 // reach, even though the branch should get folded to fall through implicitly. 416 if (MachineFunction::iterator(TBB) == Fallthrough || 417 MachineFunction::iterator(FBB) == Fallthrough) 418 return true; 419 420 // If it's an unconditional branch to some block not the fall through, it 421 // doesn't fall through. 422 if (Cond.empty()) return false; 423 424 // Otherwise, if it is conditional and has no explicit false block, it falls 425 // through. 426 return FBB == 0; 427} 428 429MachineBasicBlock * 430MachineBasicBlock::SplitCriticalEdge(MachineBasicBlock *Succ, Pass *P) { 431 MachineFunction *MF = getParent(); 432 DebugLoc dl; // FIXME: this is nowhere 433 434 // We may need to update this's terminator, but we can't do that if AnalyzeBranch 435 // fails. If this uses a jump table, we won't touch it. 436 const TargetInstrInfo *TII = MF->getTarget().getInstrInfo(); 437 MachineBasicBlock *TBB = 0, *FBB = 0; 438 SmallVector<MachineOperand, 4> Cond; 439 if (TII->AnalyzeBranch(*this, TBB, FBB, Cond)) 440 return NULL; 441 442 MachineBasicBlock *NMBB = MF->CreateMachineBasicBlock(); 443 MF->insert(llvm::next(MachineFunction::iterator(this)), NMBB); 444 DEBUG(dbgs() << "Splitting critical edge:" 445 " BB#" << getNumber() 446 << " -- BB#" << NMBB->getNumber() 447 << " -- BB#" << Succ->getNumber() << '\n'); 448 449 ReplaceUsesOfBlockWith(Succ, NMBB); 450 updateTerminator(); 451 452 // Insert unconditional "jump Succ" instruction in NMBB if necessary. 453 NMBB->addSuccessor(Succ); 454 if (!NMBB->isLayoutSuccessor(Succ)) { 455 Cond.clear(); 456 MF->getTarget().getInstrInfo()->InsertBranch(*NMBB, Succ, NULL, Cond, dl); 457 } 458 459 // Fix PHI nodes in Succ so they refer to NMBB instead of this 460 for (MachineBasicBlock::iterator i = Succ->begin(), e = Succ->end(); 461 i != e && i->isPHI(); ++i) 462 for (unsigned ni = 1, ne = i->getNumOperands(); ni != ne; ni += 2) 463 if (i->getOperand(ni+1).getMBB() == this) 464 i->getOperand(ni+1).setMBB(NMBB); 465 466 if (LiveVariables *LV = 467 P->getAnalysisIfAvailable<LiveVariables>()) 468 LV->addNewBlock(NMBB, this, Succ); 469 470 if (MachineDominatorTree *MDT = 471 P->getAnalysisIfAvailable<MachineDominatorTree>()) 472 MDT->addNewBlock(NMBB, this); 473 474 if (MachineLoopInfo *MLI = P->getAnalysisIfAvailable<MachineLoopInfo>()) 475 if (MachineLoop *TIL = MLI->getLoopFor(this)) { 476 // If one or the other blocks were not in a loop, the new block is not 477 // either, and thus LI doesn't need to be updated. 478 if (MachineLoop *DestLoop = MLI->getLoopFor(Succ)) { 479 if (TIL == DestLoop) { 480 // Both in the same loop, the NMBB joins loop. 481 DestLoop->addBasicBlockToLoop(NMBB, MLI->getBase()); 482 } else if (TIL->contains(DestLoop)) { 483 // Edge from an outer loop to an inner loop. Add to the outer loop. 484 TIL->addBasicBlockToLoop(NMBB, MLI->getBase()); 485 } else if (DestLoop->contains(TIL)) { 486 // Edge from an inner loop to an outer loop. Add to the outer loop. 487 DestLoop->addBasicBlockToLoop(NMBB, MLI->getBase()); 488 } else { 489 // Edge from two loops with no containment relation. Because these 490 // are natural loops, we know that the destination block must be the 491 // header of its loop (adding a branch into a loop elsewhere would 492 // create an irreducible loop). 493 assert(DestLoop->getHeader() == Succ && 494 "Should not create irreducible loops!"); 495 if (MachineLoop *P = DestLoop->getParentLoop()) 496 P->addBasicBlockToLoop(NMBB, MLI->getBase()); 497 } 498 } 499 } 500 501 return NMBB; 502} 503 504/// removeFromParent - This method unlinks 'this' from the containing function, 505/// and returns it, but does not delete it. 506MachineBasicBlock *MachineBasicBlock::removeFromParent() { 507 assert(getParent() && "Not embedded in a function!"); 508 getParent()->remove(this); 509 return this; 510} 511 512 513/// eraseFromParent - This method unlinks 'this' from the containing function, 514/// and deletes it. 515void MachineBasicBlock::eraseFromParent() { 516 assert(getParent() && "Not embedded in a function!"); 517 getParent()->erase(this); 518} 519 520 521/// ReplaceUsesOfBlockWith - Given a machine basic block that branched to 522/// 'Old', change the code and CFG so that it branches to 'New' instead. 523void MachineBasicBlock::ReplaceUsesOfBlockWith(MachineBasicBlock *Old, 524 MachineBasicBlock *New) { 525 assert(Old != New && "Cannot replace self with self!"); 526 527 MachineBasicBlock::iterator I = end(); 528 while (I != begin()) { 529 --I; 530 if (!I->getDesc().isTerminator()) break; 531 532 // Scan the operands of this machine instruction, replacing any uses of Old 533 // with New. 534 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) 535 if (I->getOperand(i).isMBB() && 536 I->getOperand(i).getMBB() == Old) 537 I->getOperand(i).setMBB(New); 538 } 539 540 // Update the successor information. 541 removeSuccessor(Old); 542 addSuccessor(New); 543} 544 545/// CorrectExtraCFGEdges - Various pieces of code can cause excess edges in the 546/// CFG to be inserted. If we have proven that MBB can only branch to DestA and 547/// DestB, remove any other MBB successors from the CFG. DestA and DestB can be 548/// null. 549/// 550/// Besides DestA and DestB, retain other edges leading to LandingPads 551/// (currently there can be only one; we don't check or require that here). 552/// Note it is possible that DestA and/or DestB are LandingPads. 553bool MachineBasicBlock::CorrectExtraCFGEdges(MachineBasicBlock *DestA, 554 MachineBasicBlock *DestB, 555 bool isCond) { 556 // The values of DestA and DestB frequently come from a call to the 557 // 'TargetInstrInfo::AnalyzeBranch' method. We take our meaning of the initial 558 // values from there. 559 // 560 // 1. If both DestA and DestB are null, then the block ends with no branches 561 // (it falls through to its successor). 562 // 2. If DestA is set, DestB is null, and isCond is false, then the block ends 563 // with only an unconditional branch. 564 // 3. If DestA is set, DestB is null, and isCond is true, then the block ends 565 // with a conditional branch that falls through to a successor (DestB). 566 // 4. If DestA and DestB is set and isCond is true, then the block ends with a 567 // conditional branch followed by an unconditional branch. DestA is the 568 // 'true' destination and DestB is the 'false' destination. 569 570 bool Changed = false; 571 572 MachineFunction::iterator FallThru = 573 llvm::next(MachineFunction::iterator(this)); 574 575 if (DestA == 0 && DestB == 0) { 576 // Block falls through to successor. 577 DestA = FallThru; 578 DestB = FallThru; 579 } else if (DestA != 0 && DestB == 0) { 580 if (isCond) 581 // Block ends in conditional jump that falls through to successor. 582 DestB = FallThru; 583 } else { 584 assert(DestA && DestB && isCond && 585 "CFG in a bad state. Cannot correct CFG edges"); 586 } 587 588 // Remove superfluous edges. I.e., those which aren't destinations of this 589 // basic block, duplicate edges, or landing pads. 590 SmallPtrSet<const MachineBasicBlock*, 8> SeenMBBs; 591 MachineBasicBlock::succ_iterator SI = succ_begin(); 592 while (SI != succ_end()) { 593 const MachineBasicBlock *MBB = *SI; 594 if (!SeenMBBs.insert(MBB) || 595 (MBB != DestA && MBB != DestB && !MBB->isLandingPad())) { 596 // This is a superfluous edge, remove it. 597 SI = removeSuccessor(SI); 598 Changed = true; 599 } else { 600 ++SI; 601 } 602 } 603 604 return Changed; 605} 606 607/// findDebugLoc - find the next valid DebugLoc starting at MBBI, skipping 608/// any DBG_VALUE instructions. Return UnknownLoc if there is none. 609DebugLoc 610MachineBasicBlock::findDebugLoc(MachineBasicBlock::iterator &MBBI) { 611 DebugLoc DL; 612 MachineBasicBlock::iterator E = end(); 613 if (MBBI != E) { 614 // Skip debug declarations, we don't want a DebugLoc from them. 615 MachineBasicBlock::iterator MBBI2 = MBBI; 616 while (MBBI2 != E && MBBI2->isDebugValue()) 617 MBBI2++; 618 if (MBBI2 != E) 619 DL = MBBI2->getDebugLoc(); 620 } 621 return DL; 622} 623 624void llvm::WriteAsOperand(raw_ostream &OS, const MachineBasicBlock *MBB, 625 bool t) { 626 OS << "BB#" << MBB->getNumber(); 627} 628 629