MachineBasicBlock.cpp revision 5a96b3dad2f634c9081c8b2b6c2575441dc5a2bd
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::insn_iterator I = N->insn_begin(), E = N->insn_end(); 77 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 insn_iterator I = insn_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::insn_iterator MachineBasicBlock::getFirstInsnTerminator() { 182 insn_iterator I = insn_end(); 183 while (I != insn_begin() && ((--I)->isTerminator() || I->isDebugValue())) 184 ; /*noop */ 185 while (I != insn_end() && !I->isTerminator()) 186 ++I; 187 return I; 188} 189 190MachineBasicBlock::iterator MachineBasicBlock::getLastNonDebugInstr() { 191 // Skip over end-of-block dbg_value instructions. 192 insn_iterator B = insn_begin(), I = insn_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_insn_iterator B = insn_begin(), I = insn_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_iterator I = begin(); I != end(); ++I) { 287 if (Indexes) { 288 if (Indexes->hasIndex(I)) 289 OS << Indexes->getInstructionIndex(I); 290 OS << '\t'; 291 } 292 OS << '\t'; 293 I->print(OS, &getParent()->getTarget()); 294 } 295 296 // Print the successors of this block according to the CFG. 297 if (!succ_empty()) { 298 if (Indexes) OS << '\t'; 299 OS << " Successors according to CFG:"; 300 for (const_succ_iterator SI = succ_begin(), E = succ_end(); SI != E; ++SI) 301 OS << " BB#" << (*SI)->getNumber(); 302 OS << '\n'; 303 } 304} 305 306void MachineBasicBlock::removeLiveIn(unsigned Reg) { 307 std::vector<unsigned>::iterator I = 308 std::find(LiveIns.begin(), LiveIns.end(), Reg); 309 assert(I != LiveIns.end() && "Not a live in!"); 310 LiveIns.erase(I); 311} 312 313bool MachineBasicBlock::isLiveIn(unsigned Reg) const { 314 livein_iterator I = std::find(livein_begin(), livein_end(), Reg); 315 return I != livein_end(); 316} 317 318void MachineBasicBlock::moveBefore(MachineBasicBlock *NewAfter) { 319 getParent()->splice(NewAfter, this); 320} 321 322void MachineBasicBlock::moveAfter(MachineBasicBlock *NewBefore) { 323 MachineFunction::iterator BBI = NewBefore; 324 getParent()->splice(++BBI, this); 325} 326 327void MachineBasicBlock::updateTerminator() { 328 const TargetInstrInfo *TII = getParent()->getTarget().getInstrInfo(); 329 // A block with no successors has no concerns with fall-through edges. 330 if (this->succ_empty()) return; 331 332 MachineBasicBlock *TBB = 0, *FBB = 0; 333 SmallVector<MachineOperand, 4> Cond; 334 DebugLoc dl; // FIXME: this is nowhere 335 bool B = TII->AnalyzeBranch(*this, TBB, FBB, Cond); 336 (void) B; 337 assert(!B && "UpdateTerminators requires analyzable predecessors!"); 338 if (Cond.empty()) { 339 if (TBB) { 340 // The block has an unconditional branch. If its successor is now 341 // its layout successor, delete the branch. 342 if (isLayoutSuccessor(TBB)) 343 TII->RemoveBranch(*this); 344 } else { 345 // The block has an unconditional fallthrough. If its successor is not 346 // its layout successor, insert a branch. First we have to locate the 347 // only non-landing-pad successor, as that is the fallthrough block. 348 for (succ_iterator SI = succ_begin(), SE = succ_end(); SI != SE; ++SI) { 349 if ((*SI)->isLandingPad()) 350 continue; 351 assert(!TBB && "Found more than one non-landing-pad successor!"); 352 TBB = *SI; 353 } 354 355 // If there is no non-landing-pad successor, the block has no 356 // fall-through edges to be concerned with. 357 if (!TBB) 358 return; 359 360 // Finally update the unconditional successor to be reached via a branch 361 // if it would not be reached by fallthrough. 362 if (!isLayoutSuccessor(TBB)) 363 TII->InsertBranch(*this, TBB, 0, Cond, dl); 364 } 365 } else { 366 if (FBB) { 367 // The block has a non-fallthrough conditional branch. If one of its 368 // successors is its layout successor, rewrite it to a fallthrough 369 // conditional branch. 370 if (isLayoutSuccessor(TBB)) { 371 if (TII->ReverseBranchCondition(Cond)) 372 return; 373 TII->RemoveBranch(*this); 374 TII->InsertBranch(*this, FBB, 0, Cond, dl); 375 } else if (isLayoutSuccessor(FBB)) { 376 TII->RemoveBranch(*this); 377 TII->InsertBranch(*this, TBB, 0, Cond, dl); 378 } 379 } else { 380 // The block has a fallthrough conditional branch. 381 MachineBasicBlock *MBBA = *succ_begin(); 382 MachineBasicBlock *MBBB = *llvm::next(succ_begin()); 383 if (MBBA == TBB) std::swap(MBBB, MBBA); 384 if (isLayoutSuccessor(TBB)) { 385 if (TII->ReverseBranchCondition(Cond)) { 386 // We can't reverse the condition, add an unconditional branch. 387 Cond.clear(); 388 TII->InsertBranch(*this, MBBA, 0, Cond, dl); 389 return; 390 } 391 TII->RemoveBranch(*this); 392 TII->InsertBranch(*this, MBBA, 0, Cond, dl); 393 } else if (!isLayoutSuccessor(MBBA)) { 394 TII->RemoveBranch(*this); 395 TII->InsertBranch(*this, TBB, MBBA, Cond, dl); 396 } 397 } 398 } 399} 400 401void MachineBasicBlock::addSuccessor(MachineBasicBlock *succ, uint32_t weight) { 402 403 // If we see non-zero value for the first time it means we actually use Weight 404 // list, so we fill all Weights with 0's. 405 if (weight != 0 && Weights.empty()) 406 Weights.resize(Successors.size()); 407 408 if (weight != 0 || !Weights.empty()) 409 Weights.push_back(weight); 410 411 Successors.push_back(succ); 412 succ->addPredecessor(this); 413 } 414 415void MachineBasicBlock::removeSuccessor(MachineBasicBlock *succ) { 416 succ->removePredecessor(this); 417 succ_iterator I = std::find(Successors.begin(), Successors.end(), succ); 418 assert(I != Successors.end() && "Not a current successor!"); 419 420 // If Weight list is empty it means we don't use it (disabled optimization). 421 if (!Weights.empty()) { 422 weight_iterator WI = getWeightIterator(I); 423 Weights.erase(WI); 424 } 425 426 Successors.erase(I); 427} 428 429MachineBasicBlock::succ_iterator 430MachineBasicBlock::removeSuccessor(succ_iterator I) { 431 assert(I != Successors.end() && "Not a current successor!"); 432 433 // If Weight list is empty it means we don't use it (disabled optimization). 434 if (!Weights.empty()) { 435 weight_iterator WI = getWeightIterator(I); 436 Weights.erase(WI); 437 } 438 439 (*I)->removePredecessor(this); 440 return Successors.erase(I); 441} 442 443void MachineBasicBlock::replaceSuccessor(MachineBasicBlock *Old, 444 MachineBasicBlock *New) { 445 uint32_t weight = 0; 446 succ_iterator SI = std::find(Successors.begin(), Successors.end(), Old); 447 448 // If Weight list is empty it means we don't use it (disabled optimization). 449 if (!Weights.empty()) { 450 weight_iterator WI = getWeightIterator(SI); 451 weight = *WI; 452 } 453 454 // Update the successor information. 455 removeSuccessor(SI); 456 addSuccessor(New, weight); 457} 458 459void MachineBasicBlock::addPredecessor(MachineBasicBlock *pred) { 460 Predecessors.push_back(pred); 461} 462 463void MachineBasicBlock::removePredecessor(MachineBasicBlock *pred) { 464 pred_iterator I = std::find(Predecessors.begin(), Predecessors.end(), pred); 465 assert(I != Predecessors.end() && "Pred is not a predecessor of this block!"); 466 Predecessors.erase(I); 467} 468 469void MachineBasicBlock::transferSuccessors(MachineBasicBlock *fromMBB) { 470 if (this == fromMBB) 471 return; 472 473 while (!fromMBB->succ_empty()) { 474 MachineBasicBlock *Succ = *fromMBB->succ_begin(); 475 uint32_t weight = 0; 476 477 478 // If Weight list is empty it means we don't use it (disabled optimization). 479 if (!fromMBB->Weights.empty()) 480 weight = *fromMBB->Weights.begin(); 481 482 addSuccessor(Succ, weight); 483 fromMBB->removeSuccessor(Succ); 484 } 485} 486 487void 488MachineBasicBlock::transferSuccessorsAndUpdatePHIs(MachineBasicBlock *fromMBB) { 489 if (this == fromMBB) 490 return; 491 492 while (!fromMBB->succ_empty()) { 493 MachineBasicBlock *Succ = *fromMBB->succ_begin(); 494 addSuccessor(Succ); 495 fromMBB->removeSuccessor(Succ); 496 497 // Fix up any PHI nodes in the successor. 498 for (MachineBasicBlock::insn_iterator MI = Succ->insn_begin(), 499 ME = Succ->insn_end(); MI != ME && MI->isPHI(); ++MI) 500 for (unsigned i = 2, e = MI->getNumOperands()+1; i != e; i += 2) { 501 MachineOperand &MO = MI->getOperand(i); 502 if (MO.getMBB() == fromMBB) 503 MO.setMBB(this); 504 } 505 } 506} 507 508bool MachineBasicBlock::isSuccessor(const MachineBasicBlock *MBB) const { 509 const_succ_iterator I = std::find(Successors.begin(), Successors.end(), MBB); 510 return I != Successors.end(); 511} 512 513bool MachineBasicBlock::isLayoutSuccessor(const MachineBasicBlock *MBB) const { 514 MachineFunction::const_iterator I(this); 515 return llvm::next(I) == MachineFunction::const_iterator(MBB); 516} 517 518bool MachineBasicBlock::canFallThrough() { 519 MachineFunction::iterator Fallthrough = this; 520 ++Fallthrough; 521 // If FallthroughBlock is off the end of the function, it can't fall through. 522 if (Fallthrough == getParent()->end()) 523 return false; 524 525 // If FallthroughBlock isn't a successor, no fallthrough is possible. 526 if (!isSuccessor(Fallthrough)) 527 return false; 528 529 // Analyze the branches, if any, at the end of the block. 530 MachineBasicBlock *TBB = 0, *FBB = 0; 531 SmallVector<MachineOperand, 4> Cond; 532 const TargetInstrInfo *TII = getParent()->getTarget().getInstrInfo(); 533 if (TII->AnalyzeBranch(*this, TBB, FBB, Cond)) { 534 // If we couldn't analyze the branch, examine the last instruction. 535 // If the block doesn't end in a known control barrier, assume fallthrough 536 // is possible. The isPredicable check is needed because this code can be 537 // called during IfConversion, where an instruction which is normally a 538 // Barrier is predicated and thus no longer an actual control barrier. This 539 // is over-conservative though, because if an instruction isn't actually 540 // predicated we could still treat it like a barrier. 541 return empty() || !back().isBarrier() || 542 back().isPredicable(); 543 } 544 545 // If there is no branch, control always falls through. 546 if (TBB == 0) return true; 547 548 // If there is some explicit branch to the fallthrough block, it can obviously 549 // reach, even though the branch should get folded to fall through implicitly. 550 if (MachineFunction::iterator(TBB) == Fallthrough || 551 MachineFunction::iterator(FBB) == Fallthrough) 552 return true; 553 554 // If it's an unconditional branch to some block not the fall through, it 555 // doesn't fall through. 556 if (Cond.empty()) return false; 557 558 // Otherwise, if it is conditional and has no explicit false block, it falls 559 // through. 560 return FBB == 0; 561} 562 563MachineBasicBlock * 564MachineBasicBlock::SplitCriticalEdge(MachineBasicBlock *Succ, Pass *P) { 565 MachineFunction *MF = getParent(); 566 DebugLoc dl; // FIXME: this is nowhere 567 568 // We may need to update this's terminator, but we can't do that if 569 // AnalyzeBranch fails. If this uses a jump table, we won't touch it. 570 const TargetInstrInfo *TII = MF->getTarget().getInstrInfo(); 571 MachineBasicBlock *TBB = 0, *FBB = 0; 572 SmallVector<MachineOperand, 4> Cond; 573 if (TII->AnalyzeBranch(*this, TBB, FBB, Cond)) 574 return NULL; 575 576 // Avoid bugpoint weirdness: A block may end with a conditional branch but 577 // jumps to the same MBB is either case. We have duplicate CFG edges in that 578 // case that we can't handle. Since this never happens in properly optimized 579 // code, just skip those edges. 580 if (TBB && TBB == FBB) { 581 DEBUG(dbgs() << "Won't split critical edge after degenerate BB#" 582 << getNumber() << '\n'); 583 return NULL; 584 } 585 586 MachineBasicBlock *NMBB = MF->CreateMachineBasicBlock(); 587 MF->insert(llvm::next(MachineFunction::iterator(this)), NMBB); 588 DEBUG(dbgs() << "Splitting critical edge:" 589 " BB#" << getNumber() 590 << " -- BB#" << NMBB->getNumber() 591 << " -- BB#" << Succ->getNumber() << '\n'); 592 593 // On some targets like Mips, branches may kill virtual registers. Make sure 594 // that LiveVariables is properly updated after updateTerminator replaces the 595 // terminators. 596 LiveVariables *LV = P->getAnalysisIfAvailable<LiveVariables>(); 597 598 // Collect a list of virtual registers killed by the terminators. 599 SmallVector<unsigned, 4> KilledRegs; 600 if (LV) 601 for (insn_iterator I = getFirstInsnTerminator(), E = insn_end(); 602 I != E; ++I) { 603 MachineInstr *MI = I; 604 for (MachineInstr::mop_iterator OI = MI->operands_begin(), 605 OE = MI->operands_end(); OI != OE; ++OI) { 606 if (!OI->isReg() || !OI->isUse() || !OI->isKill() || OI->isUndef()) 607 continue; 608 unsigned Reg = OI->getReg(); 609 if (TargetRegisterInfo::isVirtualRegister(Reg) && 610 LV->getVarInfo(Reg).removeKill(MI)) { 611 KilledRegs.push_back(Reg); 612 DEBUG(dbgs() << "Removing terminator kill: " << *MI); 613 OI->setIsKill(false); 614 } 615 } 616 } 617 618 ReplaceUsesOfBlockWith(Succ, NMBB); 619 updateTerminator(); 620 621 // Insert unconditional "jump Succ" instruction in NMBB if necessary. 622 NMBB->addSuccessor(Succ); 623 if (!NMBB->isLayoutSuccessor(Succ)) { 624 Cond.clear(); 625 MF->getTarget().getInstrInfo()->InsertBranch(*NMBB, Succ, NULL, Cond, dl); 626 } 627 628 // Fix PHI nodes in Succ so they refer to NMBB instead of this 629 for (MachineBasicBlock::insn_iterator 630 i = Succ->insn_begin(),e = Succ->insn_end(); i != e && i->isPHI(); ++i) 631 for (unsigned ni = 1, ne = i->getNumOperands(); ni != ne; ni += 2) 632 if (i->getOperand(ni+1).getMBB() == this) 633 i->getOperand(ni+1).setMBB(NMBB); 634 635 // Inherit live-ins from the successor 636 for (MachineBasicBlock::livein_iterator I = Succ->livein_begin(), 637 E = Succ->livein_end(); I != E; ++I) 638 NMBB->addLiveIn(*I); 639 640 // Update LiveVariables. 641 if (LV) { 642 // Restore kills of virtual registers that were killed by the terminators. 643 while (!KilledRegs.empty()) { 644 unsigned Reg = KilledRegs.pop_back_val(); 645 for (insn_iterator I = insn_end(), E = insn_begin(); I != E;) { 646 if (!(--I)->addRegisterKilled(Reg, NULL, /* addIfNotFound= */ false)) 647 continue; 648 LV->getVarInfo(Reg).Kills.push_back(I); 649 DEBUG(dbgs() << "Restored terminator kill: " << *I); 650 break; 651 } 652 } 653 // Update relevant live-through information. 654 LV->addNewBlock(NMBB, this, Succ); 655 } 656 657 if (MachineDominatorTree *MDT = 658 P->getAnalysisIfAvailable<MachineDominatorTree>()) { 659 // Update dominator information. 660 MachineDomTreeNode *SucccDTNode = MDT->getNode(Succ); 661 662 bool IsNewIDom = true; 663 for (const_pred_iterator PI = Succ->pred_begin(), E = Succ->pred_end(); 664 PI != E; ++PI) { 665 MachineBasicBlock *PredBB = *PI; 666 if (PredBB == NMBB) 667 continue; 668 if (!MDT->dominates(SucccDTNode, MDT->getNode(PredBB))) { 669 IsNewIDom = false; 670 break; 671 } 672 } 673 674 // We know "this" dominates the newly created basic block. 675 MachineDomTreeNode *NewDTNode = MDT->addNewBlock(NMBB, this); 676 677 // If all the other predecessors of "Succ" are dominated by "Succ" itself 678 // then the new block is the new immediate dominator of "Succ". Otherwise, 679 // the new block doesn't dominate anything. 680 if (IsNewIDom) 681 MDT->changeImmediateDominator(SucccDTNode, NewDTNode); 682 } 683 684 if (MachineLoopInfo *MLI = P->getAnalysisIfAvailable<MachineLoopInfo>()) 685 if (MachineLoop *TIL = MLI->getLoopFor(this)) { 686 // If one or the other blocks were not in a loop, the new block is not 687 // either, and thus LI doesn't need to be updated. 688 if (MachineLoop *DestLoop = MLI->getLoopFor(Succ)) { 689 if (TIL == DestLoop) { 690 // Both in the same loop, the NMBB joins loop. 691 DestLoop->addBasicBlockToLoop(NMBB, MLI->getBase()); 692 } else if (TIL->contains(DestLoop)) { 693 // Edge from an outer loop to an inner loop. Add to the outer loop. 694 TIL->addBasicBlockToLoop(NMBB, MLI->getBase()); 695 } else if (DestLoop->contains(TIL)) { 696 // Edge from an inner loop to an outer loop. Add to the outer loop. 697 DestLoop->addBasicBlockToLoop(NMBB, MLI->getBase()); 698 } else { 699 // Edge from two loops with no containment relation. Because these 700 // are natural loops, we know that the destination block must be the 701 // header of its loop (adding a branch into a loop elsewhere would 702 // create an irreducible loop). 703 assert(DestLoop->getHeader() == Succ && 704 "Should not create irreducible loops!"); 705 if (MachineLoop *P = DestLoop->getParentLoop()) 706 P->addBasicBlockToLoop(NMBB, MLI->getBase()); 707 } 708 } 709 } 710 711 return NMBB; 712} 713 714/// removeFromParent - This method unlinks 'this' from the containing function, 715/// and returns it, but does not delete it. 716MachineBasicBlock *MachineBasicBlock::removeFromParent() { 717 assert(getParent() && "Not embedded in a function!"); 718 getParent()->remove(this); 719 return this; 720} 721 722 723/// eraseFromParent - This method unlinks 'this' from the containing function, 724/// and deletes it. 725void MachineBasicBlock::eraseFromParent() { 726 assert(getParent() && "Not embedded in a function!"); 727 getParent()->erase(this); 728} 729 730 731/// ReplaceUsesOfBlockWith - Given a machine basic block that branched to 732/// 'Old', change the code and CFG so that it branches to 'New' instead. 733void MachineBasicBlock::ReplaceUsesOfBlockWith(MachineBasicBlock *Old, 734 MachineBasicBlock *New) { 735 assert(Old != New && "Cannot replace self with self!"); 736 737 MachineBasicBlock::insn_iterator I = insn_end(); 738 while (I != insn_begin()) { 739 --I; 740 if (!I->isTerminator()) break; 741 742 // Scan the operands of this machine instruction, replacing any uses of Old 743 // with New. 744 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) 745 if (I->getOperand(i).isMBB() && 746 I->getOperand(i).getMBB() == Old) 747 I->getOperand(i).setMBB(New); 748 } 749 750 // Update the successor information. 751 replaceSuccessor(Old, New); 752} 753 754/// CorrectExtraCFGEdges - Various pieces of code can cause excess edges in the 755/// CFG to be inserted. If we have proven that MBB can only branch to DestA and 756/// DestB, remove any other MBB successors from the CFG. DestA and DestB can be 757/// null. 758/// 759/// Besides DestA and DestB, retain other edges leading to LandingPads 760/// (currently there can be only one; we don't check or require that here). 761/// Note it is possible that DestA and/or DestB are LandingPads. 762bool MachineBasicBlock::CorrectExtraCFGEdges(MachineBasicBlock *DestA, 763 MachineBasicBlock *DestB, 764 bool isCond) { 765 // The values of DestA and DestB frequently come from a call to the 766 // 'TargetInstrInfo::AnalyzeBranch' method. We take our meaning of the initial 767 // values from there. 768 // 769 // 1. If both DestA and DestB are null, then the block ends with no branches 770 // (it falls through to its successor). 771 // 2. If DestA is set, DestB is null, and isCond is false, then the block ends 772 // with only an unconditional branch. 773 // 3. If DestA is set, DestB is null, and isCond is true, then the block ends 774 // with a conditional branch that falls through to a successor (DestB). 775 // 4. If DestA and DestB is set and isCond is true, then the block ends with a 776 // conditional branch followed by an unconditional branch. DestA is the 777 // 'true' destination and DestB is the 'false' destination. 778 779 bool Changed = false; 780 781 MachineFunction::iterator FallThru = 782 llvm::next(MachineFunction::iterator(this)); 783 784 if (DestA == 0 && DestB == 0) { 785 // Block falls through to successor. 786 DestA = FallThru; 787 DestB = FallThru; 788 } else if (DestA != 0 && DestB == 0) { 789 if (isCond) 790 // Block ends in conditional jump that falls through to successor. 791 DestB = FallThru; 792 } else { 793 assert(DestA && DestB && isCond && 794 "CFG in a bad state. Cannot correct CFG edges"); 795 } 796 797 // Remove superfluous edges. I.e., those which aren't destinations of this 798 // basic block, duplicate edges, or landing pads. 799 SmallPtrSet<const MachineBasicBlock*, 8> SeenMBBs; 800 MachineBasicBlock::succ_iterator SI = succ_begin(); 801 while (SI != succ_end()) { 802 const MachineBasicBlock *MBB = *SI; 803 if (!SeenMBBs.insert(MBB) || 804 (MBB != DestA && MBB != DestB && !MBB->isLandingPad())) { 805 // This is a superfluous edge, remove it. 806 SI = removeSuccessor(SI); 807 Changed = true; 808 } else { 809 ++SI; 810 } 811 } 812 813 return Changed; 814} 815 816/// findDebugLoc - find the next valid DebugLoc starting at MBBI, skipping 817/// any DBG_VALUE instructions. Return UnknownLoc if there is none. 818DebugLoc 819MachineBasicBlock::findDebugLoc(insn_iterator MBBI) { 820 DebugLoc DL; 821 insn_iterator E = insn_end(); 822 if (MBBI == E) 823 return DL; 824 825 // Skip debug declarations, we don't want a DebugLoc from them. 826 while (MBBI != E && MBBI->isDebugValue()) 827 MBBI++; 828 if (MBBI != E) 829 DL = MBBI->getDebugLoc(); 830 return DL; 831} 832 833/// getSuccWeight - Return weight of the edge from this block to MBB. 834/// 835uint32_t MachineBasicBlock::getSuccWeight(MachineBasicBlock *succ) { 836 if (Weights.empty()) 837 return 0; 838 839 succ_iterator I = std::find(Successors.begin(), Successors.end(), succ); 840 return *getWeightIterator(I); 841} 842 843/// getWeightIterator - Return wight iterator corresonding to the I successor 844/// iterator 845MachineBasicBlock::weight_iterator MachineBasicBlock:: 846getWeightIterator(MachineBasicBlock::succ_iterator I) { 847 assert(Weights.size() == Successors.size() && "Async weight list!"); 848 size_t index = std::distance(Successors.begin(), I); 849 assert(index < Weights.size() && "Not a current successor!"); 850 return Weights.begin() + index; 851} 852 853void llvm::WriteAsOperand(raw_ostream &OS, const MachineBasicBlock *MBB, 854 bool t) { 855 OS << "BB#" << MBB->getNumber(); 856} 857 858