MachineBasicBlock.cpp revision 913ff09a9acf563ae9719ff223bc117dd66ad6b0
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(), E = instr_end(); 145 while (I != E && 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 iterator E = end(); 154 while (I != E && (I->isPHI() || I->isLabel() || I->isDebugValue())) 155 ++I; 156 // FIXME: This needs to change if we wish to bundle labels / dbg_values 157 // inside the bundle. 158 assert(!I->isInsideBundle() && 159 "First non-phi / non-label instruction is inside a bundle!"); 160 return I; 161} 162 163MachineBasicBlock::iterator MachineBasicBlock::getFirstTerminator() { 164 iterator B = begin(), E = end(), I = E; 165 while (I != B && ((--I)->isTerminator() || I->isDebugValue())) 166 ; /*noop */ 167 while (I != E && !I->isTerminator()) 168 ++I; 169 return I; 170} 171 172MachineBasicBlock::const_iterator 173MachineBasicBlock::getFirstTerminator() const { 174 const_iterator B = begin(), E = end(), I = E; 175 while (I != B && ((--I)->isTerminator() || I->isDebugValue())) 176 ; /*noop */ 177 while (I != E && !I->isTerminator()) 178 ++I; 179 return I; 180} 181 182MachineBasicBlock::instr_iterator MachineBasicBlock::getFirstInstrTerminator() { 183 instr_iterator B = instr_begin(), E = instr_end(), I = E; 184 while (I != B && ((--I)->isTerminator() || I->isDebugValue())) 185 ; /*noop */ 186 while (I != E && !I->isTerminator()) 187 ++I; 188 return I; 189} 190 191MachineBasicBlock::iterator MachineBasicBlock::getLastNonDebugInstr() { 192 // Skip over end-of-block dbg_value instructions. 193 instr_iterator B = instr_begin(), I = instr_end(); 194 while (I != B) { 195 --I; 196 // Return instruction that starts a bundle. 197 if (I->isDebugValue() || I->isInsideBundle()) 198 continue; 199 return I; 200 } 201 // The block is all debug values. 202 return end(); 203} 204 205MachineBasicBlock::const_iterator 206MachineBasicBlock::getLastNonDebugInstr() const { 207 // Skip over end-of-block dbg_value instructions. 208 const_instr_iterator B = instr_begin(), I = instr_end(); 209 while (I != B) { 210 --I; 211 // Return instruction that starts a bundle. 212 if (I->isDebugValue() || I->isInsideBundle()) 213 continue; 214 return I; 215 } 216 // The block is all debug values. 217 return end(); 218} 219 220const MachineBasicBlock *MachineBasicBlock::getLandingPadSuccessor() const { 221 // A block with a landing pad successor only has one other successor. 222 if (succ_size() > 2) 223 return 0; 224 for (const_succ_iterator I = succ_begin(), E = succ_end(); I != E; ++I) 225 if ((*I)->isLandingPad()) 226 return *I; 227 return 0; 228} 229 230void MachineBasicBlock::dump() const { 231 print(dbgs()); 232} 233 234StringRef MachineBasicBlock::getName() const { 235 if (const BasicBlock *LBB = getBasicBlock()) 236 return LBB->getName(); 237 else 238 return "(null)"; 239} 240 241/// Return a hopefully unique identifier for this block. 242std::string MachineBasicBlock::getFullName() const { 243 std::string Name; 244 if (getParent()) 245 Name = (getParent()->getFunction()->getName() + ":").str(); 246 if (getBasicBlock()) 247 Name += getBasicBlock()->getName(); 248 else 249 Name += (Twine("BB") + Twine(getNumber())).str(); 250 return Name; 251} 252 253void MachineBasicBlock::print(raw_ostream &OS, SlotIndexes *Indexes) const { 254 const MachineFunction *MF = getParent(); 255 if (!MF) { 256 OS << "Can't print out MachineBasicBlock because parent MachineFunction" 257 << " is null\n"; 258 return; 259 } 260 261 if (Indexes) 262 OS << Indexes->getMBBStartIdx(this) << '\t'; 263 264 OS << "BB#" << getNumber() << ": "; 265 266 const char *Comma = ""; 267 if (const BasicBlock *LBB = getBasicBlock()) { 268 OS << Comma << "derived from LLVM BB "; 269 WriteAsOperand(OS, LBB, /*PrintType=*/false); 270 Comma = ", "; 271 } 272 if (isLandingPad()) { OS << Comma << "EH LANDING PAD"; Comma = ", "; } 273 if (hasAddressTaken()) { OS << Comma << "ADDRESS TAKEN"; Comma = ", "; } 274 if (Alignment) 275 OS << Comma << "Align " << Alignment << " (" << (1u << Alignment) 276 << " bytes)"; 277 278 OS << '\n'; 279 280 const TargetRegisterInfo *TRI = MF->getTarget().getRegisterInfo(); 281 if (!livein_empty()) { 282 if (Indexes) OS << '\t'; 283 OS << " Live Ins:"; 284 for (livein_iterator I = livein_begin(),E = livein_end(); I != E; ++I) 285 OS << ' ' << PrintReg(*I, TRI); 286 OS << '\n'; 287 } 288 // Print the preds of this block according to the CFG. 289 if (!pred_empty()) { 290 if (Indexes) OS << '\t'; 291 OS << " Predecessors according to CFG:"; 292 for (const_pred_iterator PI = pred_begin(), E = pred_end(); PI != E; ++PI) 293 OS << " BB#" << (*PI)->getNumber(); 294 OS << '\n'; 295 } 296 297 for (const_instr_iterator I = instr_begin(); I != instr_end(); ++I) { 298 if (Indexes) { 299 if (Indexes->hasIndex(I)) 300 OS << Indexes->getInstructionIndex(I); 301 OS << '\t'; 302 } 303 OS << '\t'; 304 if (I->isInsideBundle()) 305 OS << " * "; 306 I->print(OS, &getParent()->getTarget()); 307 } 308 309 // Print the successors of this block according to the CFG. 310 if (!succ_empty()) { 311 if (Indexes) OS << '\t'; 312 OS << " Successors according to CFG:"; 313 for (const_succ_iterator SI = succ_begin(), E = succ_end(); SI != E; ++SI) 314 OS << " BB#" << (*SI)->getNumber(); 315 OS << '\n'; 316 } 317} 318 319void MachineBasicBlock::removeLiveIn(unsigned Reg) { 320 std::vector<unsigned>::iterator I = 321 std::find(LiveIns.begin(), LiveIns.end(), Reg); 322 if (I != LiveIns.end()) 323 LiveIns.erase(I); 324} 325 326bool MachineBasicBlock::isLiveIn(unsigned Reg) const { 327 livein_iterator I = std::find(livein_begin(), livein_end(), Reg); 328 return I != livein_end(); 329} 330 331void MachineBasicBlock::moveBefore(MachineBasicBlock *NewAfter) { 332 getParent()->splice(NewAfter, this); 333} 334 335void MachineBasicBlock::moveAfter(MachineBasicBlock *NewBefore) { 336 MachineFunction::iterator BBI = NewBefore; 337 getParent()->splice(++BBI, this); 338} 339 340void MachineBasicBlock::updateTerminator() { 341 const TargetInstrInfo *TII = getParent()->getTarget().getInstrInfo(); 342 // A block with no successors has no concerns with fall-through edges. 343 if (this->succ_empty()) return; 344 345 MachineBasicBlock *TBB = 0, *FBB = 0; 346 SmallVector<MachineOperand, 4> Cond; 347 DebugLoc dl; // FIXME: this is nowhere 348 bool B = TII->AnalyzeBranch(*this, TBB, FBB, Cond); 349 (void) B; 350 assert(!B && "UpdateTerminators requires analyzable predecessors!"); 351 if (Cond.empty()) { 352 if (TBB) { 353 // The block has an unconditional branch. If its successor is now 354 // its layout successor, delete the branch. 355 if (isLayoutSuccessor(TBB)) 356 TII->RemoveBranch(*this); 357 } else { 358 // The block has an unconditional fallthrough. If its successor is not 359 // its layout successor, insert a branch. First we have to locate the 360 // only non-landing-pad successor, as that is the fallthrough block. 361 for (succ_iterator SI = succ_begin(), SE = succ_end(); SI != SE; ++SI) { 362 if ((*SI)->isLandingPad()) 363 continue; 364 assert(!TBB && "Found more than one non-landing-pad successor!"); 365 TBB = *SI; 366 } 367 368 // If there is no non-landing-pad successor, the block has no 369 // fall-through edges to be concerned with. 370 if (!TBB) 371 return; 372 373 // Finally update the unconditional successor to be reached via a branch 374 // if it would not be reached by fallthrough. 375 if (!isLayoutSuccessor(TBB)) 376 TII->InsertBranch(*this, TBB, 0, Cond, dl); 377 } 378 } else { 379 if (FBB) { 380 // The block has a non-fallthrough conditional branch. If one of its 381 // successors is its layout successor, rewrite it to a fallthrough 382 // conditional branch. 383 if (isLayoutSuccessor(TBB)) { 384 if (TII->ReverseBranchCondition(Cond)) 385 return; 386 TII->RemoveBranch(*this); 387 TII->InsertBranch(*this, FBB, 0, Cond, dl); 388 } else if (isLayoutSuccessor(FBB)) { 389 TII->RemoveBranch(*this); 390 TII->InsertBranch(*this, TBB, 0, Cond, dl); 391 } 392 } else { 393 // Walk through the successors and find the successor which is not 394 // a landing pad and is not the conditional branch destination (in TBB) 395 // as the fallthrough successor. 396 MachineBasicBlock *FallthroughBB = 0; 397 for (succ_iterator SI = succ_begin(), SE = succ_end(); SI != SE; ++SI) { 398 if ((*SI)->isLandingPad() || *SI == TBB) 399 continue; 400 assert(!FallthroughBB && "Found more than one fallthrough successor."); 401 FallthroughBB = *SI; 402 } 403 if (!FallthroughBB && canFallThrough()) { 404 // We fallthrough to the same basic block as the conditional jump 405 // targets. Remove the conditional jump, leaving unconditional 406 // fallthrough. 407 // FIXME: This does not seem like a reasonable pattern to support, but it 408 // has been seen in the wild coming out of degenerate ARM test cases. 409 TII->RemoveBranch(*this); 410 411 // Finally update the unconditional successor to be reached via a branch 412 // if it would not be reached by fallthrough. 413 if (!isLayoutSuccessor(TBB)) 414 TII->InsertBranch(*this, TBB, 0, Cond, dl); 415 return; 416 } 417 418 // The block has a fallthrough conditional branch. 419 if (isLayoutSuccessor(TBB)) { 420 if (TII->ReverseBranchCondition(Cond)) { 421 // We can't reverse the condition, add an unconditional branch. 422 Cond.clear(); 423 TII->InsertBranch(*this, FallthroughBB, 0, Cond, dl); 424 return; 425 } 426 TII->RemoveBranch(*this); 427 TII->InsertBranch(*this, FallthroughBB, 0, Cond, dl); 428 } else if (!isLayoutSuccessor(FallthroughBB)) { 429 TII->RemoveBranch(*this); 430 TII->InsertBranch(*this, TBB, FallthroughBB, Cond, dl); 431 } 432 } 433 } 434} 435 436void MachineBasicBlock::addSuccessor(MachineBasicBlock *succ, uint32_t weight) { 437 438 // If we see non-zero value for the first time it means we actually use Weight 439 // list, so we fill all Weights with 0's. 440 if (weight != 0 && Weights.empty()) 441 Weights.resize(Successors.size()); 442 443 if (weight != 0 || !Weights.empty()) 444 Weights.push_back(weight); 445 446 Successors.push_back(succ); 447 succ->addPredecessor(this); 448 } 449 450void MachineBasicBlock::removeSuccessor(MachineBasicBlock *succ) { 451 succ->removePredecessor(this); 452 succ_iterator I = std::find(Successors.begin(), Successors.end(), succ); 453 assert(I != Successors.end() && "Not a current successor!"); 454 455 // If Weight list is empty it means we don't use it (disabled optimization). 456 if (!Weights.empty()) { 457 weight_iterator WI = getWeightIterator(I); 458 Weights.erase(WI); 459 } 460 461 Successors.erase(I); 462} 463 464MachineBasicBlock::succ_iterator 465MachineBasicBlock::removeSuccessor(succ_iterator I) { 466 assert(I != Successors.end() && "Not a current successor!"); 467 468 // If Weight list is empty it means we don't use it (disabled optimization). 469 if (!Weights.empty()) { 470 weight_iterator WI = getWeightIterator(I); 471 Weights.erase(WI); 472 } 473 474 (*I)->removePredecessor(this); 475 return Successors.erase(I); 476} 477 478void MachineBasicBlock::replaceSuccessor(MachineBasicBlock *Old, 479 MachineBasicBlock *New) { 480 uint32_t weight = 0; 481 succ_iterator SI = std::find(Successors.begin(), Successors.end(), Old); 482 483 // If Weight list is empty it means we don't use it (disabled optimization). 484 if (!Weights.empty()) { 485 weight_iterator WI = getWeightIterator(SI); 486 weight = *WI; 487 } 488 489 // Update the successor information. 490 removeSuccessor(SI); 491 addSuccessor(New, weight); 492} 493 494void MachineBasicBlock::addPredecessor(MachineBasicBlock *pred) { 495 Predecessors.push_back(pred); 496} 497 498void MachineBasicBlock::removePredecessor(MachineBasicBlock *pred) { 499 pred_iterator I = std::find(Predecessors.begin(), Predecessors.end(), pred); 500 assert(I != Predecessors.end() && "Pred is not a predecessor of this block!"); 501 Predecessors.erase(I); 502} 503 504void MachineBasicBlock::transferSuccessors(MachineBasicBlock *fromMBB) { 505 if (this == fromMBB) 506 return; 507 508 while (!fromMBB->succ_empty()) { 509 MachineBasicBlock *Succ = *fromMBB->succ_begin(); 510 uint32_t weight = 0; 511 512 513 // If Weight list is empty it means we don't use it (disabled optimization). 514 if (!fromMBB->Weights.empty()) 515 weight = *fromMBB->Weights.begin(); 516 517 addSuccessor(Succ, weight); 518 fromMBB->removeSuccessor(Succ); 519 } 520} 521 522void 523MachineBasicBlock::transferSuccessorsAndUpdatePHIs(MachineBasicBlock *fromMBB) { 524 if (this == fromMBB) 525 return; 526 527 while (!fromMBB->succ_empty()) { 528 MachineBasicBlock *Succ = *fromMBB->succ_begin(); 529 addSuccessor(Succ); 530 fromMBB->removeSuccessor(Succ); 531 532 // Fix up any PHI nodes in the successor. 533 for (MachineBasicBlock::instr_iterator MI = Succ->instr_begin(), 534 ME = Succ->instr_end(); MI != ME && MI->isPHI(); ++MI) 535 for (unsigned i = 2, e = MI->getNumOperands()+1; i != e; i += 2) { 536 MachineOperand &MO = MI->getOperand(i); 537 if (MO.getMBB() == fromMBB) 538 MO.setMBB(this); 539 } 540 } 541} 542 543bool MachineBasicBlock::isPredecessor(const MachineBasicBlock *MBB) const { 544 return std::find(pred_begin(), pred_end(), MBB) != pred_end(); 545} 546 547bool MachineBasicBlock::isSuccessor(const MachineBasicBlock *MBB) const { 548 return std::find(succ_begin(), succ_end(), MBB) != succ_end(); 549} 550 551bool MachineBasicBlock::isLayoutSuccessor(const MachineBasicBlock *MBB) const { 552 MachineFunction::const_iterator I(this); 553 return llvm::next(I) == MachineFunction::const_iterator(MBB); 554} 555 556bool MachineBasicBlock::canFallThrough() { 557 MachineFunction::iterator Fallthrough = this; 558 ++Fallthrough; 559 // If FallthroughBlock is off the end of the function, it can't fall through. 560 if (Fallthrough == getParent()->end()) 561 return false; 562 563 // If FallthroughBlock isn't a successor, no fallthrough is possible. 564 if (!isSuccessor(Fallthrough)) 565 return false; 566 567 // Analyze the branches, if any, at the end of the block. 568 MachineBasicBlock *TBB = 0, *FBB = 0; 569 SmallVector<MachineOperand, 4> Cond; 570 const TargetInstrInfo *TII = getParent()->getTarget().getInstrInfo(); 571 if (TII->AnalyzeBranch(*this, TBB, FBB, Cond)) { 572 // If we couldn't analyze the branch, examine the last instruction. 573 // If the block doesn't end in a known control barrier, assume fallthrough 574 // is possible. The isPredicated check is needed because this code can be 575 // called during IfConversion, where an instruction which is normally a 576 // Barrier is predicated and thus no longer an actual control barrier. 577 return empty() || !back().isBarrier() || TII->isPredicated(&back()); 578 } 579 580 // If there is no branch, control always falls through. 581 if (TBB == 0) return true; 582 583 // If there is some explicit branch to the fallthrough block, it can obviously 584 // reach, even though the branch should get folded to fall through implicitly. 585 if (MachineFunction::iterator(TBB) == Fallthrough || 586 MachineFunction::iterator(FBB) == Fallthrough) 587 return true; 588 589 // If it's an unconditional branch to some block not the fall through, it 590 // doesn't fall through. 591 if (Cond.empty()) return false; 592 593 // Otherwise, if it is conditional and has no explicit false block, it falls 594 // through. 595 return FBB == 0; 596} 597 598MachineBasicBlock * 599MachineBasicBlock::SplitCriticalEdge(MachineBasicBlock *Succ, Pass *P) { 600 // Splitting the critical edge to a landing pad block is non-trivial. Don't do 601 // it in this generic function. 602 if (Succ->isLandingPad()) 603 return NULL; 604 605 MachineFunction *MF = getParent(); 606 DebugLoc dl; // FIXME: this is nowhere 607 608 // We may need to update this's terminator, but we can't do that if 609 // AnalyzeBranch fails. If this uses a jump table, we won't touch it. 610 const TargetInstrInfo *TII = MF->getTarget().getInstrInfo(); 611 MachineBasicBlock *TBB = 0, *FBB = 0; 612 SmallVector<MachineOperand, 4> Cond; 613 if (TII->AnalyzeBranch(*this, TBB, FBB, Cond)) 614 return NULL; 615 616 // Avoid bugpoint weirdness: A block may end with a conditional branch but 617 // jumps to the same MBB is either case. We have duplicate CFG edges in that 618 // case that we can't handle. Since this never happens in properly optimized 619 // code, just skip those edges. 620 if (TBB && TBB == FBB) { 621 DEBUG(dbgs() << "Won't split critical edge after degenerate BB#" 622 << getNumber() << '\n'); 623 return NULL; 624 } 625 626 MachineBasicBlock *NMBB = MF->CreateMachineBasicBlock(); 627 MF->insert(llvm::next(MachineFunction::iterator(this)), NMBB); 628 DEBUG(dbgs() << "Splitting critical edge:" 629 " BB#" << getNumber() 630 << " -- BB#" << NMBB->getNumber() 631 << " -- BB#" << Succ->getNumber() << '\n'); 632 633 // On some targets like Mips, branches may kill virtual registers. Make sure 634 // that LiveVariables is properly updated after updateTerminator replaces the 635 // terminators. 636 LiveVariables *LV = P->getAnalysisIfAvailable<LiveVariables>(); 637 638 // Collect a list of virtual registers killed by the terminators. 639 SmallVector<unsigned, 4> KilledRegs; 640 if (LV) 641 for (instr_iterator I = getFirstInstrTerminator(), E = instr_end(); 642 I != E; ++I) { 643 MachineInstr *MI = I; 644 for (MachineInstr::mop_iterator OI = MI->operands_begin(), 645 OE = MI->operands_end(); OI != OE; ++OI) { 646 if (!OI->isReg() || OI->getReg() == 0 || 647 !OI->isUse() || !OI->isKill() || OI->isUndef()) 648 continue; 649 unsigned Reg = OI->getReg(); 650 if (TargetRegisterInfo::isPhysicalRegister(Reg) || 651 LV->getVarInfo(Reg).removeKill(MI)) { 652 KilledRegs.push_back(Reg); 653 DEBUG(dbgs() << "Removing terminator kill: " << *MI); 654 OI->setIsKill(false); 655 } 656 } 657 } 658 659 ReplaceUsesOfBlockWith(Succ, NMBB); 660 updateTerminator(); 661 662 // Insert unconditional "jump Succ" instruction in NMBB if necessary. 663 NMBB->addSuccessor(Succ); 664 if (!NMBB->isLayoutSuccessor(Succ)) { 665 Cond.clear(); 666 MF->getTarget().getInstrInfo()->InsertBranch(*NMBB, Succ, NULL, Cond, dl); 667 } 668 669 // Fix PHI nodes in Succ so they refer to NMBB instead of this 670 for (MachineBasicBlock::instr_iterator 671 i = Succ->instr_begin(),e = Succ->instr_end(); 672 i != e && i->isPHI(); ++i) 673 for (unsigned ni = 1, ne = i->getNumOperands(); ni != ne; ni += 2) 674 if (i->getOperand(ni+1).getMBB() == this) 675 i->getOperand(ni+1).setMBB(NMBB); 676 677 // Inherit live-ins from the successor 678 for (MachineBasicBlock::livein_iterator I = Succ->livein_begin(), 679 E = Succ->livein_end(); I != E; ++I) 680 NMBB->addLiveIn(*I); 681 682 // Update LiveVariables. 683 const TargetRegisterInfo *TRI = MF->getTarget().getRegisterInfo(); 684 if (LV) { 685 // Restore kills of virtual registers that were killed by the terminators. 686 while (!KilledRegs.empty()) { 687 unsigned Reg = KilledRegs.pop_back_val(); 688 for (instr_iterator I = instr_end(), E = instr_begin(); I != E;) { 689 if (!(--I)->addRegisterKilled(Reg, TRI, /* addIfNotFound= */ false)) 690 continue; 691 if (TargetRegisterInfo::isVirtualRegister(Reg)) 692 LV->getVarInfo(Reg).Kills.push_back(I); 693 DEBUG(dbgs() << "Restored terminator kill: " << *I); 694 break; 695 } 696 } 697 // Update relevant live-through information. 698 LV->addNewBlock(NMBB, this, Succ); 699 } 700 701 if (MachineDominatorTree *MDT = 702 P->getAnalysisIfAvailable<MachineDominatorTree>()) { 703 // Update dominator information. 704 MachineDomTreeNode *SucccDTNode = MDT->getNode(Succ); 705 706 bool IsNewIDom = true; 707 for (const_pred_iterator PI = Succ->pred_begin(), E = Succ->pred_end(); 708 PI != E; ++PI) { 709 MachineBasicBlock *PredBB = *PI; 710 if (PredBB == NMBB) 711 continue; 712 if (!MDT->dominates(SucccDTNode, MDT->getNode(PredBB))) { 713 IsNewIDom = false; 714 break; 715 } 716 } 717 718 // We know "this" dominates the newly created basic block. 719 MachineDomTreeNode *NewDTNode = MDT->addNewBlock(NMBB, this); 720 721 // If all the other predecessors of "Succ" are dominated by "Succ" itself 722 // then the new block is the new immediate dominator of "Succ". Otherwise, 723 // the new block doesn't dominate anything. 724 if (IsNewIDom) 725 MDT->changeImmediateDominator(SucccDTNode, NewDTNode); 726 } 727 728 if (MachineLoopInfo *MLI = P->getAnalysisIfAvailable<MachineLoopInfo>()) 729 if (MachineLoop *TIL = MLI->getLoopFor(this)) { 730 // If one or the other blocks were not in a loop, the new block is not 731 // either, and thus LI doesn't need to be updated. 732 if (MachineLoop *DestLoop = MLI->getLoopFor(Succ)) { 733 if (TIL == DestLoop) { 734 // Both in the same loop, the NMBB joins loop. 735 DestLoop->addBasicBlockToLoop(NMBB, MLI->getBase()); 736 } else if (TIL->contains(DestLoop)) { 737 // Edge from an outer loop to an inner loop. Add to the outer loop. 738 TIL->addBasicBlockToLoop(NMBB, MLI->getBase()); 739 } else if (DestLoop->contains(TIL)) { 740 // Edge from an inner loop to an outer loop. Add to the outer loop. 741 DestLoop->addBasicBlockToLoop(NMBB, MLI->getBase()); 742 } else { 743 // Edge from two loops with no containment relation. Because these 744 // are natural loops, we know that the destination block must be the 745 // header of its loop (adding a branch into a loop elsewhere would 746 // create an irreducible loop). 747 assert(DestLoop->getHeader() == Succ && 748 "Should not create irreducible loops!"); 749 if (MachineLoop *P = DestLoop->getParentLoop()) 750 P->addBasicBlockToLoop(NMBB, MLI->getBase()); 751 } 752 } 753 } 754 755 return NMBB; 756} 757 758MachineBasicBlock::iterator 759MachineBasicBlock::erase(MachineBasicBlock::iterator I) { 760 if (I->isBundle()) { 761 MachineBasicBlock::iterator E = llvm::next(I); 762 return Insts.erase(I.getInstrIterator(), E.getInstrIterator()); 763 } 764 765 return Insts.erase(I.getInstrIterator()); 766} 767 768MachineInstr *MachineBasicBlock::remove(MachineInstr *I) { 769 if (I->isBundle()) { 770 instr_iterator MII = llvm::next(I); 771 iterator E = end(); 772 while (MII != E && MII->isInsideBundle()) { 773 MachineInstr *MI = &*MII++; 774 Insts.remove(MI); 775 } 776 } 777 778 return Insts.remove(I); 779} 780 781void MachineBasicBlock::splice(MachineBasicBlock::iterator where, 782 MachineBasicBlock *Other, 783 MachineBasicBlock::iterator From) { 784 if (From->isBundle()) { 785 MachineBasicBlock::iterator To = llvm::next(From); 786 Insts.splice(where.getInstrIterator(), Other->Insts, 787 From.getInstrIterator(), To.getInstrIterator()); 788 return; 789 } 790 791 Insts.splice(where.getInstrIterator(), Other->Insts, From.getInstrIterator()); 792} 793 794/// removeFromParent - This method unlinks 'this' from the containing function, 795/// and returns it, but does not delete it. 796MachineBasicBlock *MachineBasicBlock::removeFromParent() { 797 assert(getParent() && "Not embedded in a function!"); 798 getParent()->remove(this); 799 return this; 800} 801 802 803/// eraseFromParent - This method unlinks 'this' from the containing function, 804/// and deletes it. 805void MachineBasicBlock::eraseFromParent() { 806 assert(getParent() && "Not embedded in a function!"); 807 getParent()->erase(this); 808} 809 810 811/// ReplaceUsesOfBlockWith - Given a machine basic block that branched to 812/// 'Old', change the code and CFG so that it branches to 'New' instead. 813void MachineBasicBlock::ReplaceUsesOfBlockWith(MachineBasicBlock *Old, 814 MachineBasicBlock *New) { 815 assert(Old != New && "Cannot replace self with self!"); 816 817 MachineBasicBlock::instr_iterator I = instr_end(); 818 while (I != instr_begin()) { 819 --I; 820 if (!I->isTerminator()) break; 821 822 // Scan the operands of this machine instruction, replacing any uses of Old 823 // with New. 824 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) 825 if (I->getOperand(i).isMBB() && 826 I->getOperand(i).getMBB() == Old) 827 I->getOperand(i).setMBB(New); 828 } 829 830 // Update the successor information. 831 replaceSuccessor(Old, New); 832} 833 834/// CorrectExtraCFGEdges - Various pieces of code can cause excess edges in the 835/// CFG to be inserted. If we have proven that MBB can only branch to DestA and 836/// DestB, remove any other MBB successors from the CFG. DestA and DestB can be 837/// null. 838/// 839/// Besides DestA and DestB, retain other edges leading to LandingPads 840/// (currently there can be only one; we don't check or require that here). 841/// Note it is possible that DestA and/or DestB are LandingPads. 842bool MachineBasicBlock::CorrectExtraCFGEdges(MachineBasicBlock *DestA, 843 MachineBasicBlock *DestB, 844 bool isCond) { 845 // The values of DestA and DestB frequently come from a call to the 846 // 'TargetInstrInfo::AnalyzeBranch' method. We take our meaning of the initial 847 // values from there. 848 // 849 // 1. If both DestA and DestB are null, then the block ends with no branches 850 // (it falls through to its successor). 851 // 2. If DestA is set, DestB is null, and isCond is false, then the block ends 852 // with only an unconditional branch. 853 // 3. If DestA is set, DestB is null, and isCond is true, then the block ends 854 // with a conditional branch that falls through to a successor (DestB). 855 // 4. If DestA and DestB is set and isCond is true, then the block ends with a 856 // conditional branch followed by an unconditional branch. DestA is the 857 // 'true' destination and DestB is the 'false' destination. 858 859 bool Changed = false; 860 861 MachineFunction::iterator FallThru = 862 llvm::next(MachineFunction::iterator(this)); 863 864 if (DestA == 0 && DestB == 0) { 865 // Block falls through to successor. 866 DestA = FallThru; 867 DestB = FallThru; 868 } else if (DestA != 0 && DestB == 0) { 869 if (isCond) 870 // Block ends in conditional jump that falls through to successor. 871 DestB = FallThru; 872 } else { 873 assert(DestA && DestB && isCond && 874 "CFG in a bad state. Cannot correct CFG edges"); 875 } 876 877 // Remove superfluous edges. I.e., those which aren't destinations of this 878 // basic block, duplicate edges, or landing pads. 879 SmallPtrSet<const MachineBasicBlock*, 8> SeenMBBs; 880 MachineBasicBlock::succ_iterator SI = succ_begin(); 881 while (SI != succ_end()) { 882 const MachineBasicBlock *MBB = *SI; 883 if (!SeenMBBs.insert(MBB) || 884 (MBB != DestA && MBB != DestB && !MBB->isLandingPad())) { 885 // This is a superfluous edge, remove it. 886 SI = removeSuccessor(SI); 887 Changed = true; 888 } else { 889 ++SI; 890 } 891 } 892 893 return Changed; 894} 895 896/// findDebugLoc - find the next valid DebugLoc starting at MBBI, skipping 897/// any DBG_VALUE instructions. Return UnknownLoc if there is none. 898DebugLoc 899MachineBasicBlock::findDebugLoc(instr_iterator MBBI) { 900 DebugLoc DL; 901 instr_iterator E = instr_end(); 902 if (MBBI == E) 903 return DL; 904 905 // Skip debug declarations, we don't want a DebugLoc from them. 906 while (MBBI != E && MBBI->isDebugValue()) 907 MBBI++; 908 if (MBBI != E) 909 DL = MBBI->getDebugLoc(); 910 return DL; 911} 912 913/// getSuccWeight - Return weight of the edge from this block to MBB. 914/// 915uint32_t MachineBasicBlock::getSuccWeight(const MachineBasicBlock *succ) const { 916 if (Weights.empty()) 917 return 0; 918 919 const_succ_iterator I = std::find(Successors.begin(), Successors.end(), succ); 920 return *getWeightIterator(I); 921} 922 923/// getWeightIterator - Return wight iterator corresonding to the I successor 924/// iterator 925MachineBasicBlock::weight_iterator MachineBasicBlock:: 926getWeightIterator(MachineBasicBlock::succ_iterator I) { 927 assert(Weights.size() == Successors.size() && "Async weight list!"); 928 size_t index = std::distance(Successors.begin(), I); 929 assert(index < Weights.size() && "Not a current successor!"); 930 return Weights.begin() + index; 931} 932 933/// getWeightIterator - Return wight iterator corresonding to the I successor 934/// iterator 935MachineBasicBlock::const_weight_iterator MachineBasicBlock:: 936getWeightIterator(MachineBasicBlock::const_succ_iterator I) const { 937 assert(Weights.size() == Successors.size() && "Async weight list!"); 938 const size_t index = std::distance(Successors.begin(), I); 939 assert(index < Weights.size() && "Not a current successor!"); 940 return Weights.begin() + index; 941} 942 943void llvm::WriteAsOperand(raw_ostream &OS, const MachineBasicBlock *MBB, 944 bool t) { 945 OS << "BB#" << MBB->getNumber(); 946} 947 948