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 if (MachineFunction *MF = N->getParent()->getParent()) 113 N->RemoveRegOperandsFromUseLists(MF->getRegInfo()); 114 115 N->setParent(0); 116 117 LeakDetector::addGarbageObject(N); 118} 119 120/// transferNodesFromList (MI) - When moving a range of instructions from one 121/// MBB list to another, we need to update the parent pointers and the use/def 122/// lists. 123void ilist_traits<MachineInstr>:: 124transferNodesFromList(ilist_traits<MachineInstr> &fromList, 125 ilist_iterator<MachineInstr> first, 126 ilist_iterator<MachineInstr> last) { 127 assert(Parent->getParent() == fromList.Parent->getParent() && 128 "MachineInstr parent mismatch!"); 129 130 // Splice within the same MBB -> no change. 131 if (Parent == fromList.Parent) return; 132 133 // If splicing between two blocks within the same function, just update the 134 // parent pointers. 135 for (; first != last; ++first) 136 first->setParent(Parent); 137} 138 139void ilist_traits<MachineInstr>::deleteNode(MachineInstr* MI) { 140 assert(!MI->getParent() && "MI is still in a block!"); 141 Parent->getParent()->DeleteMachineInstr(MI); 142} 143 144MachineBasicBlock::iterator MachineBasicBlock::getFirstNonPHI() { 145 instr_iterator I = instr_begin(), E = instr_end(); 146 while (I != E && I->isPHI()) 147 ++I; 148 assert(!I->isInsideBundle() && "First non-phi MI cannot be inside a bundle!"); 149 return I; 150} 151 152MachineBasicBlock::iterator 153MachineBasicBlock::SkipPHIsAndLabels(MachineBasicBlock::iterator I) { 154 iterator E = end(); 155 while (I != E && (I->isPHI() || I->isLabel() || I->isDebugValue())) 156 ++I; 157 // FIXME: This needs to change if we wish to bundle labels / dbg_values 158 // inside the bundle. 159 assert(!I->isInsideBundle() && 160 "First non-phi / non-label instruction is inside a bundle!"); 161 return I; 162} 163 164MachineBasicBlock::iterator MachineBasicBlock::getFirstTerminator() { 165 iterator B = begin(), E = end(), I = E; 166 while (I != B && ((--I)->isTerminator() || I->isDebugValue())) 167 ; /*noop */ 168 while (I != E && !I->isTerminator()) 169 ++I; 170 return I; 171} 172 173MachineBasicBlock::const_iterator 174MachineBasicBlock::getFirstTerminator() const { 175 const_iterator B = begin(), E = end(), I = E; 176 while (I != B && ((--I)->isTerminator() || I->isDebugValue())) 177 ; /*noop */ 178 while (I != E && !I->isTerminator()) 179 ++I; 180 return I; 181} 182 183MachineBasicBlock::instr_iterator MachineBasicBlock::getFirstInstrTerminator() { 184 instr_iterator B = instr_begin(), E = instr_end(), I = E; 185 while (I != B && ((--I)->isTerminator() || I->isDebugValue())) 186 ; /*noop */ 187 while (I != E && !I->isTerminator()) 188 ++I; 189 return I; 190} 191 192MachineBasicBlock::iterator MachineBasicBlock::getLastNonDebugInstr() { 193 // Skip over end-of-block dbg_value instructions. 194 instr_iterator B = instr_begin(), I = instr_end(); 195 while (I != B) { 196 --I; 197 // Return instruction that starts a bundle. 198 if (I->isDebugValue() || I->isInsideBundle()) 199 continue; 200 return I; 201 } 202 // The block is all debug values. 203 return end(); 204} 205 206MachineBasicBlock::const_iterator 207MachineBasicBlock::getLastNonDebugInstr() const { 208 // Skip over end-of-block dbg_value instructions. 209 const_instr_iterator B = instr_begin(), I = instr_end(); 210 while (I != B) { 211 --I; 212 // Return instruction that starts a bundle. 213 if (I->isDebugValue() || I->isInsideBundle()) 214 continue; 215 return I; 216 } 217 // The block is all debug values. 218 return end(); 219} 220 221const MachineBasicBlock *MachineBasicBlock::getLandingPadSuccessor() const { 222 // A block with a landing pad successor only has one other successor. 223 if (succ_size() > 2) 224 return 0; 225 for (const_succ_iterator I = succ_begin(), E = succ_end(); I != E; ++I) 226 if ((*I)->isLandingPad()) 227 return *I; 228 return 0; 229} 230 231#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) 232void MachineBasicBlock::dump() const { 233 print(dbgs()); 234} 235#endif 236 237StringRef MachineBasicBlock::getName() const { 238 if (const BasicBlock *LBB = getBasicBlock()) 239 return LBB->getName(); 240 else 241 return "(null)"; 242} 243 244/// Return a hopefully unique identifier for this block. 245std::string MachineBasicBlock::getFullName() const { 246 std::string Name; 247 if (getParent()) 248 Name = (getParent()->getName() + ":").str(); 249 if (getBasicBlock()) 250 Name += getBasicBlock()->getName(); 251 else 252 Name += (Twine("BB") + Twine(getNumber())).str(); 253 return Name; 254} 255 256void MachineBasicBlock::print(raw_ostream &OS, SlotIndexes *Indexes) const { 257 const MachineFunction *MF = getParent(); 258 if (!MF) { 259 OS << "Can't print out MachineBasicBlock because parent MachineFunction" 260 << " is null\n"; 261 return; 262 } 263 264 if (Indexes) 265 OS << Indexes->getMBBStartIdx(this) << '\t'; 266 267 OS << "BB#" << getNumber() << ": "; 268 269 const char *Comma = ""; 270 if (const BasicBlock *LBB = getBasicBlock()) { 271 OS << Comma << "derived from LLVM BB "; 272 WriteAsOperand(OS, LBB, /*PrintType=*/false); 273 Comma = ", "; 274 } 275 if (isLandingPad()) { OS << Comma << "EH LANDING PAD"; Comma = ", "; } 276 if (hasAddressTaken()) { OS << Comma << "ADDRESS TAKEN"; Comma = ", "; } 277 if (Alignment) 278 OS << Comma << "Align " << Alignment << " (" << (1u << Alignment) 279 << " bytes)"; 280 281 OS << '\n'; 282 283 const TargetRegisterInfo *TRI = MF->getTarget().getRegisterInfo(); 284 if (!livein_empty()) { 285 if (Indexes) OS << '\t'; 286 OS << " Live Ins:"; 287 for (livein_iterator I = livein_begin(),E = livein_end(); I != E; ++I) 288 OS << ' ' << PrintReg(*I, TRI); 289 OS << '\n'; 290 } 291 // Print the preds of this block according to the CFG. 292 if (!pred_empty()) { 293 if (Indexes) OS << '\t'; 294 OS << " Predecessors according to CFG:"; 295 for (const_pred_iterator PI = pred_begin(), E = pred_end(); PI != E; ++PI) 296 OS << " BB#" << (*PI)->getNumber(); 297 OS << '\n'; 298 } 299 300 for (const_instr_iterator I = instr_begin(); I != instr_end(); ++I) { 301 if (Indexes) { 302 if (Indexes->hasIndex(I)) 303 OS << Indexes->getInstructionIndex(I); 304 OS << '\t'; 305 } 306 OS << '\t'; 307 if (I->isInsideBundle()) 308 OS << " * "; 309 I->print(OS, &getParent()->getTarget()); 310 } 311 312 // Print the successors of this block according to the CFG. 313 if (!succ_empty()) { 314 if (Indexes) OS << '\t'; 315 OS << " Successors according to CFG:"; 316 for (const_succ_iterator SI = succ_begin(), E = succ_end(); SI != E; ++SI) { 317 OS << " BB#" << (*SI)->getNumber(); 318 if (!Weights.empty()) 319 OS << '(' << *getWeightIterator(SI) << ')'; 320 } 321 OS << '\n'; 322 } 323} 324 325void MachineBasicBlock::removeLiveIn(unsigned Reg) { 326 std::vector<unsigned>::iterator I = 327 std::find(LiveIns.begin(), LiveIns.end(), Reg); 328 if (I != LiveIns.end()) 329 LiveIns.erase(I); 330} 331 332bool MachineBasicBlock::isLiveIn(unsigned Reg) const { 333 livein_iterator I = std::find(livein_begin(), livein_end(), Reg); 334 return I != livein_end(); 335} 336 337void MachineBasicBlock::moveBefore(MachineBasicBlock *NewAfter) { 338 getParent()->splice(NewAfter, this); 339} 340 341void MachineBasicBlock::moveAfter(MachineBasicBlock *NewBefore) { 342 MachineFunction::iterator BBI = NewBefore; 343 getParent()->splice(++BBI, this); 344} 345 346void MachineBasicBlock::updateTerminator() { 347 const TargetInstrInfo *TII = getParent()->getTarget().getInstrInfo(); 348 // A block with no successors has no concerns with fall-through edges. 349 if (this->succ_empty()) return; 350 351 MachineBasicBlock *TBB = 0, *FBB = 0; 352 SmallVector<MachineOperand, 4> Cond; 353 DebugLoc dl; // FIXME: this is nowhere 354 bool B = TII->AnalyzeBranch(*this, TBB, FBB, Cond); 355 (void) B; 356 assert(!B && "UpdateTerminators requires analyzable predecessors!"); 357 if (Cond.empty()) { 358 if (TBB) { 359 // The block has an unconditional branch. If its successor is now 360 // its layout successor, delete the branch. 361 if (isLayoutSuccessor(TBB)) 362 TII->RemoveBranch(*this); 363 } else { 364 // The block has an unconditional fallthrough. If its successor is not 365 // its layout successor, insert a branch. First we have to locate the 366 // only non-landing-pad successor, as that is the fallthrough block. 367 for (succ_iterator SI = succ_begin(), SE = succ_end(); SI != SE; ++SI) { 368 if ((*SI)->isLandingPad()) 369 continue; 370 assert(!TBB && "Found more than one non-landing-pad successor!"); 371 TBB = *SI; 372 } 373 374 // If there is no non-landing-pad successor, the block has no 375 // fall-through edges to be concerned with. 376 if (!TBB) 377 return; 378 379 // Finally update the unconditional successor to be reached via a branch 380 // if it would not be reached by fallthrough. 381 if (!isLayoutSuccessor(TBB)) 382 TII->InsertBranch(*this, TBB, 0, Cond, dl); 383 } 384 } else { 385 if (FBB) { 386 // The block has a non-fallthrough conditional branch. If one of its 387 // successors is its layout successor, rewrite it to a fallthrough 388 // conditional branch. 389 if (isLayoutSuccessor(TBB)) { 390 if (TII->ReverseBranchCondition(Cond)) 391 return; 392 TII->RemoveBranch(*this); 393 TII->InsertBranch(*this, FBB, 0, Cond, dl); 394 } else if (isLayoutSuccessor(FBB)) { 395 TII->RemoveBranch(*this); 396 TII->InsertBranch(*this, TBB, 0, Cond, dl); 397 } 398 } else { 399 // Walk through the successors and find the successor which is not 400 // a landing pad and is not the conditional branch destination (in TBB) 401 // as the fallthrough successor. 402 MachineBasicBlock *FallthroughBB = 0; 403 for (succ_iterator SI = succ_begin(), SE = succ_end(); SI != SE; ++SI) { 404 if ((*SI)->isLandingPad() || *SI == TBB) 405 continue; 406 assert(!FallthroughBB && "Found more than one fallthrough successor."); 407 FallthroughBB = *SI; 408 } 409 if (!FallthroughBB && canFallThrough()) { 410 // We fallthrough to the same basic block as the conditional jump 411 // targets. Remove the conditional jump, leaving unconditional 412 // fallthrough. 413 // FIXME: This does not seem like a reasonable pattern to support, but it 414 // has been seen in the wild coming out of degenerate ARM test cases. 415 TII->RemoveBranch(*this); 416 417 // Finally update the unconditional successor to be reached via a branch 418 // if it would not be reached by fallthrough. 419 if (!isLayoutSuccessor(TBB)) 420 TII->InsertBranch(*this, TBB, 0, Cond, dl); 421 return; 422 } 423 424 // The block has a fallthrough conditional branch. 425 if (isLayoutSuccessor(TBB)) { 426 if (TII->ReverseBranchCondition(Cond)) { 427 // We can't reverse the condition, add an unconditional branch. 428 Cond.clear(); 429 TII->InsertBranch(*this, FallthroughBB, 0, Cond, dl); 430 return; 431 } 432 TII->RemoveBranch(*this); 433 TII->InsertBranch(*this, FallthroughBB, 0, Cond, dl); 434 } else if (!isLayoutSuccessor(FallthroughBB)) { 435 TII->RemoveBranch(*this); 436 TII->InsertBranch(*this, TBB, FallthroughBB, Cond, dl); 437 } 438 } 439 } 440} 441 442void MachineBasicBlock::addSuccessor(MachineBasicBlock *succ, uint32_t weight) { 443 444 // If we see non-zero value for the first time it means we actually use Weight 445 // list, so we fill all Weights with 0's. 446 if (weight != 0 && Weights.empty()) 447 Weights.resize(Successors.size()); 448 449 if (weight != 0 || !Weights.empty()) 450 Weights.push_back(weight); 451 452 Successors.push_back(succ); 453 succ->addPredecessor(this); 454 } 455 456void MachineBasicBlock::removeSuccessor(MachineBasicBlock *succ) { 457 succ->removePredecessor(this); 458 succ_iterator I = std::find(Successors.begin(), Successors.end(), succ); 459 assert(I != Successors.end() && "Not a current successor!"); 460 461 // If Weight list is empty it means we don't use it (disabled optimization). 462 if (!Weights.empty()) { 463 weight_iterator WI = getWeightIterator(I); 464 Weights.erase(WI); 465 } 466 467 Successors.erase(I); 468} 469 470MachineBasicBlock::succ_iterator 471MachineBasicBlock::removeSuccessor(succ_iterator I) { 472 assert(I != Successors.end() && "Not a current successor!"); 473 474 // If Weight list is empty it means we don't use it (disabled optimization). 475 if (!Weights.empty()) { 476 weight_iterator WI = getWeightIterator(I); 477 Weights.erase(WI); 478 } 479 480 (*I)->removePredecessor(this); 481 return Successors.erase(I); 482} 483 484void MachineBasicBlock::replaceSuccessor(MachineBasicBlock *Old, 485 MachineBasicBlock *New) { 486 if (Old == New) 487 return; 488 489 succ_iterator E = succ_end(); 490 succ_iterator NewI = E; 491 succ_iterator OldI = E; 492 for (succ_iterator I = succ_begin(); I != E; ++I) { 493 if (*I == Old) { 494 OldI = I; 495 if (NewI != E) 496 break; 497 } 498 if (*I == New) { 499 NewI = I; 500 if (OldI != E) 501 break; 502 } 503 } 504 assert(OldI != E && "Old is not a successor of this block"); 505 Old->removePredecessor(this); 506 507 // If New isn't already a successor, let it take Old's place. 508 if (NewI == E) { 509 New->addPredecessor(this); 510 *OldI = New; 511 return; 512 } 513 514 // New is already a successor. 515 // Update its weight instead of adding a duplicate edge. 516 if (!Weights.empty()) { 517 weight_iterator OldWI = getWeightIterator(OldI); 518 *getWeightIterator(NewI) += *OldWI; 519 Weights.erase(OldWI); 520 } 521 Successors.erase(OldI); 522} 523 524void MachineBasicBlock::addPredecessor(MachineBasicBlock *pred) { 525 Predecessors.push_back(pred); 526} 527 528void MachineBasicBlock::removePredecessor(MachineBasicBlock *pred) { 529 pred_iterator I = std::find(Predecessors.begin(), Predecessors.end(), pred); 530 assert(I != Predecessors.end() && "Pred is not a predecessor of this block!"); 531 Predecessors.erase(I); 532} 533 534void MachineBasicBlock::transferSuccessors(MachineBasicBlock *fromMBB) { 535 if (this == fromMBB) 536 return; 537 538 while (!fromMBB->succ_empty()) { 539 MachineBasicBlock *Succ = *fromMBB->succ_begin(); 540 uint32_t Weight = 0; 541 542 // If Weight list is empty it means we don't use it (disabled optimization). 543 if (!fromMBB->Weights.empty()) 544 Weight = *fromMBB->Weights.begin(); 545 546 addSuccessor(Succ, Weight); 547 fromMBB->removeSuccessor(Succ); 548 } 549} 550 551void 552MachineBasicBlock::transferSuccessorsAndUpdatePHIs(MachineBasicBlock *fromMBB) { 553 if (this == fromMBB) 554 return; 555 556 while (!fromMBB->succ_empty()) { 557 MachineBasicBlock *Succ = *fromMBB->succ_begin(); 558 uint32_t Weight = 0; 559 if (!fromMBB->Weights.empty()) 560 Weight = *fromMBB->Weights.begin(); 561 addSuccessor(Succ, Weight); 562 fromMBB->removeSuccessor(Succ); 563 564 // Fix up any PHI nodes in the successor. 565 for (MachineBasicBlock::instr_iterator MI = Succ->instr_begin(), 566 ME = Succ->instr_end(); MI != ME && MI->isPHI(); ++MI) 567 for (unsigned i = 2, e = MI->getNumOperands()+1; i != e; i += 2) { 568 MachineOperand &MO = MI->getOperand(i); 569 if (MO.getMBB() == fromMBB) 570 MO.setMBB(this); 571 } 572 } 573} 574 575bool MachineBasicBlock::isPredecessor(const MachineBasicBlock *MBB) const { 576 return std::find(pred_begin(), pred_end(), MBB) != pred_end(); 577} 578 579bool MachineBasicBlock::isSuccessor(const MachineBasicBlock *MBB) const { 580 return std::find(succ_begin(), succ_end(), MBB) != succ_end(); 581} 582 583bool MachineBasicBlock::isLayoutSuccessor(const MachineBasicBlock *MBB) const { 584 MachineFunction::const_iterator I(this); 585 return llvm::next(I) == MachineFunction::const_iterator(MBB); 586} 587 588bool MachineBasicBlock::canFallThrough() { 589 MachineFunction::iterator Fallthrough = this; 590 ++Fallthrough; 591 // If FallthroughBlock is off the end of the function, it can't fall through. 592 if (Fallthrough == getParent()->end()) 593 return false; 594 595 // If FallthroughBlock isn't a successor, no fallthrough is possible. 596 if (!isSuccessor(Fallthrough)) 597 return false; 598 599 // Analyze the branches, if any, at the end of the block. 600 MachineBasicBlock *TBB = 0, *FBB = 0; 601 SmallVector<MachineOperand, 4> Cond; 602 const TargetInstrInfo *TII = getParent()->getTarget().getInstrInfo(); 603 if (TII->AnalyzeBranch(*this, TBB, FBB, Cond)) { 604 // If we couldn't analyze the branch, examine the last instruction. 605 // If the block doesn't end in a known control barrier, assume fallthrough 606 // is possible. The isPredicated check is needed because this code can be 607 // called during IfConversion, where an instruction which is normally a 608 // Barrier is predicated and thus no longer an actual control barrier. 609 return empty() || !back().isBarrier() || TII->isPredicated(&back()); 610 } 611 612 // If there is no branch, control always falls through. 613 if (TBB == 0) return true; 614 615 // If there is some explicit branch to the fallthrough block, it can obviously 616 // reach, even though the branch should get folded to fall through implicitly. 617 if (MachineFunction::iterator(TBB) == Fallthrough || 618 MachineFunction::iterator(FBB) == Fallthrough) 619 return true; 620 621 // If it's an unconditional branch to some block not the fall through, it 622 // doesn't fall through. 623 if (Cond.empty()) return false; 624 625 // Otherwise, if it is conditional and has no explicit false block, it falls 626 // through. 627 return FBB == 0; 628} 629 630MachineBasicBlock * 631MachineBasicBlock::SplitCriticalEdge(MachineBasicBlock *Succ, Pass *P) { 632 // Splitting the critical edge to a landing pad block is non-trivial. Don't do 633 // it in this generic function. 634 if (Succ->isLandingPad()) 635 return NULL; 636 637 MachineFunction *MF = getParent(); 638 DebugLoc dl; // FIXME: this is nowhere 639 640 // We may need to update this's terminator, but we can't do that if 641 // AnalyzeBranch fails. If this uses a jump table, we won't touch it. 642 const TargetInstrInfo *TII = MF->getTarget().getInstrInfo(); 643 MachineBasicBlock *TBB = 0, *FBB = 0; 644 SmallVector<MachineOperand, 4> Cond; 645 if (TII->AnalyzeBranch(*this, TBB, FBB, Cond)) 646 return NULL; 647 648 // Avoid bugpoint weirdness: A block may end with a conditional branch but 649 // jumps to the same MBB is either case. We have duplicate CFG edges in that 650 // case that we can't handle. Since this never happens in properly optimized 651 // code, just skip those edges. 652 if (TBB && TBB == FBB) { 653 DEBUG(dbgs() << "Won't split critical edge after degenerate BB#" 654 << getNumber() << '\n'); 655 return NULL; 656 } 657 658 MachineBasicBlock *NMBB = MF->CreateMachineBasicBlock(); 659 MF->insert(llvm::next(MachineFunction::iterator(this)), NMBB); 660 DEBUG(dbgs() << "Splitting critical edge:" 661 " BB#" << getNumber() 662 << " -- BB#" << NMBB->getNumber() 663 << " -- BB#" << Succ->getNumber() << '\n'); 664 665 // On some targets like Mips, branches may kill virtual registers. Make sure 666 // that LiveVariables is properly updated after updateTerminator replaces the 667 // terminators. 668 LiveVariables *LV = P->getAnalysisIfAvailable<LiveVariables>(); 669 670 // Collect a list of virtual registers killed by the terminators. 671 SmallVector<unsigned, 4> KilledRegs; 672 if (LV) 673 for (instr_iterator I = getFirstInstrTerminator(), E = instr_end(); 674 I != E; ++I) { 675 MachineInstr *MI = I; 676 for (MachineInstr::mop_iterator OI = MI->operands_begin(), 677 OE = MI->operands_end(); OI != OE; ++OI) { 678 if (!OI->isReg() || OI->getReg() == 0 || 679 !OI->isUse() || !OI->isKill() || OI->isUndef()) 680 continue; 681 unsigned Reg = OI->getReg(); 682 if (TargetRegisterInfo::isPhysicalRegister(Reg) || 683 LV->getVarInfo(Reg).removeKill(MI)) { 684 KilledRegs.push_back(Reg); 685 DEBUG(dbgs() << "Removing terminator kill: " << *MI); 686 OI->setIsKill(false); 687 } 688 } 689 } 690 691 ReplaceUsesOfBlockWith(Succ, NMBB); 692 updateTerminator(); 693 694 // Insert unconditional "jump Succ" instruction in NMBB if necessary. 695 NMBB->addSuccessor(Succ); 696 if (!NMBB->isLayoutSuccessor(Succ)) { 697 Cond.clear(); 698 MF->getTarget().getInstrInfo()->InsertBranch(*NMBB, Succ, NULL, Cond, dl); 699 } 700 701 // Fix PHI nodes in Succ so they refer to NMBB instead of this 702 for (MachineBasicBlock::instr_iterator 703 i = Succ->instr_begin(),e = Succ->instr_end(); 704 i != e && i->isPHI(); ++i) 705 for (unsigned ni = 1, ne = i->getNumOperands(); ni != ne; ni += 2) 706 if (i->getOperand(ni+1).getMBB() == this) 707 i->getOperand(ni+1).setMBB(NMBB); 708 709 // Inherit live-ins from the successor 710 for (MachineBasicBlock::livein_iterator I = Succ->livein_begin(), 711 E = Succ->livein_end(); I != E; ++I) 712 NMBB->addLiveIn(*I); 713 714 // Update LiveVariables. 715 const TargetRegisterInfo *TRI = MF->getTarget().getRegisterInfo(); 716 if (LV) { 717 // Restore kills of virtual registers that were killed by the terminators. 718 while (!KilledRegs.empty()) { 719 unsigned Reg = KilledRegs.pop_back_val(); 720 for (instr_iterator I = instr_end(), E = instr_begin(); I != E;) { 721 if (!(--I)->addRegisterKilled(Reg, TRI, /* addIfNotFound= */ false)) 722 continue; 723 if (TargetRegisterInfo::isVirtualRegister(Reg)) 724 LV->getVarInfo(Reg).Kills.push_back(I); 725 DEBUG(dbgs() << "Restored terminator kill: " << *I); 726 break; 727 } 728 } 729 // Update relevant live-through information. 730 LV->addNewBlock(NMBB, this, Succ); 731 } 732 733 if (MachineDominatorTree *MDT = 734 P->getAnalysisIfAvailable<MachineDominatorTree>()) { 735 // Update dominator information. 736 MachineDomTreeNode *SucccDTNode = MDT->getNode(Succ); 737 738 bool IsNewIDom = true; 739 for (const_pred_iterator PI = Succ->pred_begin(), E = Succ->pred_end(); 740 PI != E; ++PI) { 741 MachineBasicBlock *PredBB = *PI; 742 if (PredBB == NMBB) 743 continue; 744 if (!MDT->dominates(SucccDTNode, MDT->getNode(PredBB))) { 745 IsNewIDom = false; 746 break; 747 } 748 } 749 750 // We know "this" dominates the newly created basic block. 751 MachineDomTreeNode *NewDTNode = MDT->addNewBlock(NMBB, this); 752 753 // If all the other predecessors of "Succ" are dominated by "Succ" itself 754 // then the new block is the new immediate dominator of "Succ". Otherwise, 755 // the new block doesn't dominate anything. 756 if (IsNewIDom) 757 MDT->changeImmediateDominator(SucccDTNode, NewDTNode); 758 } 759 760 if (MachineLoopInfo *MLI = P->getAnalysisIfAvailable<MachineLoopInfo>()) 761 if (MachineLoop *TIL = MLI->getLoopFor(this)) { 762 // If one or the other blocks were not in a loop, the new block is not 763 // either, and thus LI doesn't need to be updated. 764 if (MachineLoop *DestLoop = MLI->getLoopFor(Succ)) { 765 if (TIL == DestLoop) { 766 // Both in the same loop, the NMBB joins loop. 767 DestLoop->addBasicBlockToLoop(NMBB, MLI->getBase()); 768 } else if (TIL->contains(DestLoop)) { 769 // Edge from an outer loop to an inner loop. Add to the outer loop. 770 TIL->addBasicBlockToLoop(NMBB, MLI->getBase()); 771 } else if (DestLoop->contains(TIL)) { 772 // Edge from an inner loop to an outer loop. Add to the outer loop. 773 DestLoop->addBasicBlockToLoop(NMBB, MLI->getBase()); 774 } else { 775 // Edge from two loops with no containment relation. Because these 776 // are natural loops, we know that the destination block must be the 777 // header of its loop (adding a branch into a loop elsewhere would 778 // create an irreducible loop). 779 assert(DestLoop->getHeader() == Succ && 780 "Should not create irreducible loops!"); 781 if (MachineLoop *P = DestLoop->getParentLoop()) 782 P->addBasicBlockToLoop(NMBB, MLI->getBase()); 783 } 784 } 785 } 786 787 return NMBB; 788} 789 790MachineBasicBlock::iterator 791MachineBasicBlock::erase(MachineBasicBlock::iterator I) { 792 if (I->isBundle()) { 793 MachineBasicBlock::iterator E = llvm::next(I); 794 return Insts.erase(I.getInstrIterator(), E.getInstrIterator()); 795 } 796 797 return Insts.erase(I.getInstrIterator()); 798} 799 800MachineInstr *MachineBasicBlock::remove(MachineInstr *I) { 801 if (I->isBundle()) { 802 instr_iterator MII = llvm::next(I); 803 iterator E = end(); 804 while (MII != E && MII->isInsideBundle()) { 805 MachineInstr *MI = &*MII++; 806 Insts.remove(MI); 807 } 808 } 809 810 return Insts.remove(I); 811} 812 813void MachineBasicBlock::splice(MachineBasicBlock::iterator where, 814 MachineBasicBlock *Other, 815 MachineBasicBlock::iterator From) { 816 if (From->isBundle()) { 817 MachineBasicBlock::iterator To = llvm::next(From); 818 Insts.splice(where.getInstrIterator(), Other->Insts, 819 From.getInstrIterator(), To.getInstrIterator()); 820 return; 821 } 822 823 Insts.splice(where.getInstrIterator(), Other->Insts, From.getInstrIterator()); 824} 825 826/// removeFromParent - This method unlinks 'this' from the containing function, 827/// and returns it, but does not delete it. 828MachineBasicBlock *MachineBasicBlock::removeFromParent() { 829 assert(getParent() && "Not embedded in a function!"); 830 getParent()->remove(this); 831 return this; 832} 833 834 835/// eraseFromParent - This method unlinks 'this' from the containing function, 836/// and deletes it. 837void MachineBasicBlock::eraseFromParent() { 838 assert(getParent() && "Not embedded in a function!"); 839 getParent()->erase(this); 840} 841 842 843/// ReplaceUsesOfBlockWith - Given a machine basic block that branched to 844/// 'Old', change the code and CFG so that it branches to 'New' instead. 845void MachineBasicBlock::ReplaceUsesOfBlockWith(MachineBasicBlock *Old, 846 MachineBasicBlock *New) { 847 assert(Old != New && "Cannot replace self with self!"); 848 849 MachineBasicBlock::instr_iterator I = instr_end(); 850 while (I != instr_begin()) { 851 --I; 852 if (!I->isTerminator()) break; 853 854 // Scan the operands of this machine instruction, replacing any uses of Old 855 // with New. 856 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) 857 if (I->getOperand(i).isMBB() && 858 I->getOperand(i).getMBB() == Old) 859 I->getOperand(i).setMBB(New); 860 } 861 862 // Update the successor information. 863 replaceSuccessor(Old, New); 864} 865 866/// CorrectExtraCFGEdges - Various pieces of code can cause excess edges in the 867/// CFG to be inserted. If we have proven that MBB can only branch to DestA and 868/// DestB, remove any other MBB successors from the CFG. DestA and DestB can be 869/// null. 870/// 871/// Besides DestA and DestB, retain other edges leading to LandingPads 872/// (currently there can be only one; we don't check or require that here). 873/// Note it is possible that DestA and/or DestB are LandingPads. 874bool MachineBasicBlock::CorrectExtraCFGEdges(MachineBasicBlock *DestA, 875 MachineBasicBlock *DestB, 876 bool isCond) { 877 // The values of DestA and DestB frequently come from a call to the 878 // 'TargetInstrInfo::AnalyzeBranch' method. We take our meaning of the initial 879 // values from there. 880 // 881 // 1. If both DestA and DestB are null, then the block ends with no branches 882 // (it falls through to its successor). 883 // 2. If DestA is set, DestB is null, and isCond is false, then the block ends 884 // with only an unconditional branch. 885 // 3. If DestA is set, DestB is null, and isCond is true, then the block ends 886 // with a conditional branch that falls through to a successor (DestB). 887 // 4. If DestA and DestB is set and isCond is true, then the block ends with a 888 // conditional branch followed by an unconditional branch. DestA is the 889 // 'true' destination and DestB is the 'false' destination. 890 891 bool Changed = false; 892 893 MachineFunction::iterator FallThru = 894 llvm::next(MachineFunction::iterator(this)); 895 896 if (DestA == 0 && DestB == 0) { 897 // Block falls through to successor. 898 DestA = FallThru; 899 DestB = FallThru; 900 } else if (DestA != 0 && DestB == 0) { 901 if (isCond) 902 // Block ends in conditional jump that falls through to successor. 903 DestB = FallThru; 904 } else { 905 assert(DestA && DestB && isCond && 906 "CFG in a bad state. Cannot correct CFG edges"); 907 } 908 909 // Remove superfluous edges. I.e., those which aren't destinations of this 910 // basic block, duplicate edges, or landing pads. 911 SmallPtrSet<const MachineBasicBlock*, 8> SeenMBBs; 912 MachineBasicBlock::succ_iterator SI = succ_begin(); 913 while (SI != succ_end()) { 914 const MachineBasicBlock *MBB = *SI; 915 if (!SeenMBBs.insert(MBB) || 916 (MBB != DestA && MBB != DestB && !MBB->isLandingPad())) { 917 // This is a superfluous edge, remove it. 918 SI = removeSuccessor(SI); 919 Changed = true; 920 } else { 921 ++SI; 922 } 923 } 924 925 return Changed; 926} 927 928/// findDebugLoc - find the next valid DebugLoc starting at MBBI, skipping 929/// any DBG_VALUE instructions. Return UnknownLoc if there is none. 930DebugLoc 931MachineBasicBlock::findDebugLoc(instr_iterator MBBI) { 932 DebugLoc DL; 933 instr_iterator E = instr_end(); 934 if (MBBI == E) 935 return DL; 936 937 // Skip debug declarations, we don't want a DebugLoc from them. 938 while (MBBI != E && MBBI->isDebugValue()) 939 MBBI++; 940 if (MBBI != E) 941 DL = MBBI->getDebugLoc(); 942 return DL; 943} 944 945/// getSuccWeight - Return weight of the edge from this block to MBB. 946/// 947uint32_t MachineBasicBlock::getSuccWeight(const_succ_iterator Succ) const { 948 if (Weights.empty()) 949 return 0; 950 951 return *getWeightIterator(Succ); 952} 953 954/// getWeightIterator - Return wight iterator corresonding to the I successor 955/// iterator 956MachineBasicBlock::weight_iterator MachineBasicBlock:: 957getWeightIterator(MachineBasicBlock::succ_iterator I) { 958 assert(Weights.size() == Successors.size() && "Async weight list!"); 959 size_t index = std::distance(Successors.begin(), I); 960 assert(index < Weights.size() && "Not a current successor!"); 961 return Weights.begin() + index; 962} 963 964/// getWeightIterator - Return wight iterator corresonding to the I successor 965/// iterator 966MachineBasicBlock::const_weight_iterator MachineBasicBlock:: 967getWeightIterator(MachineBasicBlock::const_succ_iterator I) const { 968 assert(Weights.size() == Successors.size() && "Async weight list!"); 969 const size_t index = std::distance(Successors.begin(), I); 970 assert(index < Weights.size() && "Not a current successor!"); 971 return Weights.begin() + index; 972} 973 974/// Return whether (physical) register "Reg" has been <def>ined and not <kill>ed 975/// as of just before "MI". 976/// 977/// Search is localised to a neighborhood of 978/// Neighborhood instructions before (searching for defs or kills) and N 979/// instructions after (searching just for defs) MI. 980MachineBasicBlock::LivenessQueryResult 981MachineBasicBlock::computeRegisterLiveness(const TargetRegisterInfo *TRI, 982 unsigned Reg, MachineInstr *MI, 983 unsigned Neighborhood) { 984 985 unsigned N = Neighborhood; 986 MachineBasicBlock *MBB = MI->getParent(); 987 988 // Start by searching backwards from MI, looking for kills, reads or defs. 989 990 MachineBasicBlock::iterator I(MI); 991 // If this is the first insn in the block, don't search backwards. 992 if (I != MBB->begin()) { 993 do { 994 --I; 995 996 MachineOperandIteratorBase::PhysRegInfo Analysis = 997 MIOperands(I).analyzePhysReg(Reg, TRI); 998 999 if (Analysis.Kills) 1000 // Register killed, so isn't live. 1001 return LQR_Dead; 1002 1003 else if (Analysis.DefinesOverlap || Analysis.ReadsOverlap) 1004 // Defined or read without a previous kill - live. 1005 return (Analysis.Defines || Analysis.Reads) ? 1006 LQR_Live : LQR_OverlappingLive; 1007 1008 } while (I != MBB->begin() && --N > 0); 1009 } 1010 1011 // Did we get to the start of the block? 1012 if (I == MBB->begin()) { 1013 // If so, the register's state is definitely defined by the live-in state. 1014 for (MCRegAliasIterator RAI(Reg, TRI, /*IncludeSelf=*/true); 1015 RAI.isValid(); ++RAI) { 1016 if (MBB->isLiveIn(*RAI)) 1017 return (*RAI == Reg) ? LQR_Live : LQR_OverlappingLive; 1018 } 1019 1020 return LQR_Dead; 1021 } 1022 1023 N = Neighborhood; 1024 1025 // Try searching forwards from MI, looking for reads or defs. 1026 I = MachineBasicBlock::iterator(MI); 1027 // If this is the last insn in the block, don't search forwards. 1028 if (I != MBB->end()) { 1029 for (++I; I != MBB->end() && N > 0; ++I, --N) { 1030 MachineOperandIteratorBase::PhysRegInfo Analysis = 1031 MIOperands(I).analyzePhysReg(Reg, TRI); 1032 1033 if (Analysis.ReadsOverlap) 1034 // Used, therefore must have been live. 1035 return (Analysis.Reads) ? 1036 LQR_Live : LQR_OverlappingLive; 1037 1038 else if (Analysis.DefinesOverlap) 1039 // Defined (but not read) therefore cannot have been live. 1040 return LQR_Dead; 1041 } 1042 } 1043 1044 // At this point we have no idea of the liveness of the register. 1045 return LQR_Unknown; 1046} 1047 1048void llvm::WriteAsOperand(raw_ostream &OS, const MachineBasicBlock *MBB, 1049 bool t) { 1050 OS << "BB#" << MBB->getNumber(); 1051} 1052 1053