1 //===-- llvm/CodeGen/MachineBasicBlock.cpp ----------------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // Collect the sequence of machine instructions for a basic block.
12 //===----------------------------------------------------------------------===//
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"
36 MachineBasicBlock::MachineBasicBlock(MachineFunction &mf, const BasicBlock *bb)
37 : BB(bb), Number(-1), xParent(&mf), Alignment(0), IsLandingPad(false),
42 MachineBasicBlock::~MachineBasicBlock() {
43 LeakDetector::removeGarbageObject(this);
46 /// getSymbol - Return the MCSymbol for this basic block.
48 MCSymbol *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()) + "_" +
58 raw_ostream &llvm::operator<<(raw_ostream &OS, const MachineBasicBlock &MBB) {
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.
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.
70 void ilist_traits<MachineBasicBlock>::addNodeToList(MachineBasicBlock *N) {
71 MachineFunction &MF = *N->getParent();
72 N->Number = MF.addToMBBNumbering(N);
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);
80 LeakDetector::removeGarbageObject(N);
83 void ilist_traits<MachineBasicBlock>::removeNodeFromList(MachineBasicBlock *N) {
84 N->getParent()->removeFromMBBNumbering(N->Number);
86 LeakDetector::addGarbageObject(N);
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.
93 void ilist_traits<MachineInstr>::addNodeToList(MachineInstr *N) {
94 assert(N->getParent() == 0 && "machine instruction already in a basic block");
97 // Add the instruction's register operands to their corresponding
99 MachineFunction *MF = Parent->getParent();
100 N->AddRegOperandsToUseLists(MF->getRegInfo());
102 LeakDetector::removeGarbageObject(N);
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.
108 void ilist_traits<MachineInstr>::removeNodeFromList(MachineInstr *N) {
109 assert(N->getParent() != 0 && "machine instruction not in a basic block");
111 // Remove from the use/def lists.
112 if (MachineFunction *MF = N->getParent()->getParent())
113 N->RemoveRegOperandsFromUseLists(MF->getRegInfo());
117 LeakDetector::addGarbageObject(N);
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
123 void ilist_traits<MachineInstr>::
124 transferNodesFromList(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!");
130 // Splice within the same MBB -> no change.
131 if (Parent == fromList.Parent) return;
133 // If splicing between two blocks within the same function, just update the
135 for (; first != last; ++first)
136 first->setParent(Parent);
139 void ilist_traits<MachineInstr>::deleteNode(MachineInstr* MI) {
140 assert(!MI->getParent() && "MI is still in a block!");
141 Parent->getParent()->DeleteMachineInstr(MI);
144 MachineBasicBlock::iterator MachineBasicBlock::getFirstNonPHI() {
145 instr_iterator I = instr_begin(), E = instr_end();
146 while (I != E && I->isPHI())
148 assert(!I->isInsideBundle() && "First non-phi MI cannot be inside a bundle!");
152 MachineBasicBlock::iterator
153 MachineBasicBlock::SkipPHIsAndLabels(MachineBasicBlock::iterator I) {
155 while (I != E && (I->isPHI() || I->isLabel() || I->isDebugValue()))
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!");
164 MachineBasicBlock::iterator MachineBasicBlock::getFirstTerminator() {
165 iterator B = begin(), E = end(), I = E;
166 while (I != B && ((--I)->isTerminator() || I->isDebugValue()))
168 while (I != E && !I->isTerminator())
173 MachineBasicBlock::const_iterator
174 MachineBasicBlock::getFirstTerminator() const {
175 const_iterator B = begin(), E = end(), I = E;
176 while (I != B && ((--I)->isTerminator() || I->isDebugValue()))
178 while (I != E && !I->isTerminator())
183 MachineBasicBlock::instr_iterator MachineBasicBlock::getFirstInstrTerminator() {
184 instr_iterator B = instr_begin(), E = instr_end(), I = E;
185 while (I != B && ((--I)->isTerminator() || I->isDebugValue()))
187 while (I != E && !I->isTerminator())
192 MachineBasicBlock::iterator MachineBasicBlock::getLastNonDebugInstr() {
193 // Skip over end-of-block dbg_value instructions.
194 instr_iterator B = instr_begin(), I = instr_end();
197 // Return instruction that starts a bundle.
198 if (I->isDebugValue() || I->isInsideBundle())
202 // The block is all debug values.
206 MachineBasicBlock::const_iterator
207 MachineBasicBlock::getLastNonDebugInstr() const {
208 // Skip over end-of-block dbg_value instructions.
209 const_instr_iterator B = instr_begin(), I = instr_end();
212 // Return instruction that starts a bundle.
213 if (I->isDebugValue() || I->isInsideBundle())
217 // The block is all debug values.
221 const MachineBasicBlock *MachineBasicBlock::getLandingPadSuccessor() const {
222 // A block with a landing pad successor only has one other successor.
225 for (const_succ_iterator I = succ_begin(), E = succ_end(); I != E; ++I)
226 if ((*I)->isLandingPad())
231 void MachineBasicBlock::dump() const {
235 StringRef MachineBasicBlock::getName() const {
236 if (const BasicBlock *LBB = getBasicBlock())
237 return LBB->getName();
242 /// Return a hopefully unique identifier for this block.
243 std::string MachineBasicBlock::getFullName() const {
246 Name = (getParent()->getName() + ":").str();
248 Name += getBasicBlock()->getName();
250 Name += (Twine("BB") + Twine(getNumber())).str();
254 void MachineBasicBlock::print(raw_ostream &OS, SlotIndexes *Indexes) const {
255 const MachineFunction *MF = getParent();
257 OS << "Can't print out MachineBasicBlock because parent MachineFunction"
263 OS << Indexes->getMBBStartIdx(this) << '\t';
265 OS << "BB#" << getNumber() << ": ";
267 const char *Comma = "";
268 if (const BasicBlock *LBB = getBasicBlock()) {
269 OS << Comma << "derived from LLVM BB ";
270 WriteAsOperand(OS, LBB, /*PrintType=*/false);
273 if (isLandingPad()) { OS << Comma << "EH LANDING PAD"; Comma = ", "; }
274 if (hasAddressTaken()) { OS << Comma << "ADDRESS TAKEN"; Comma = ", "; }
276 OS << Comma << "Align " << Alignment << " (" << (1u << Alignment)
281 const TargetRegisterInfo *TRI = MF->getTarget().getRegisterInfo();
282 if (!livein_empty()) {
283 if (Indexes) OS << '\t';
285 for (livein_iterator I = livein_begin(),E = livein_end(); I != E; ++I)
286 OS << ' ' << PrintReg(*I, TRI);
289 // Print the preds of this block according to the CFG.
291 if (Indexes) OS << '\t';
292 OS << " Predecessors according to CFG:";
293 for (const_pred_iterator PI = pred_begin(), E = pred_end(); PI != E; ++PI)
294 OS << " BB#" << (*PI)->getNumber();
298 for (const_instr_iterator I = instr_begin(); I != instr_end(); ++I) {
300 if (Indexes->hasIndex(I))
301 OS << Indexes->getInstructionIndex(I);
305 if (I->isInsideBundle())
307 I->print(OS, &getParent()->getTarget());
310 // Print the successors of this block according to the CFG.
312 if (Indexes) OS << '\t';
313 OS << " Successors according to CFG:";
314 for (const_succ_iterator SI = succ_begin(), E = succ_end(); SI != E; ++SI) {
315 OS << " BB#" << (*SI)->getNumber();
316 if (!Weights.empty())
317 OS << '(' << *getWeightIterator(SI) << ')';
323 void MachineBasicBlock::removeLiveIn(unsigned Reg) {
324 std::vector<unsigned>::iterator I =
325 std::find(LiveIns.begin(), LiveIns.end(), Reg);
326 if (I != LiveIns.end())
330 bool MachineBasicBlock::isLiveIn(unsigned Reg) const {
331 livein_iterator I = std::find(livein_begin(), livein_end(), Reg);
332 return I != livein_end();
335 void MachineBasicBlock::moveBefore(MachineBasicBlock *NewAfter) {
336 getParent()->splice(NewAfter, this);
339 void MachineBasicBlock::moveAfter(MachineBasicBlock *NewBefore) {
340 MachineFunction::iterator BBI = NewBefore;
341 getParent()->splice(++BBI, this);
344 void MachineBasicBlock::updateTerminator() {
345 const TargetInstrInfo *TII = getParent()->getTarget().getInstrInfo();
346 // A block with no successors has no concerns with fall-through edges.
347 if (this->succ_empty()) return;
349 MachineBasicBlock *TBB = 0, *FBB = 0;
350 SmallVector<MachineOperand, 4> Cond;
351 DebugLoc dl; // FIXME: this is nowhere
352 bool B = TII->AnalyzeBranch(*this, TBB, FBB, Cond);
354 assert(!B && "UpdateTerminators requires analyzable predecessors!");
357 // The block has an unconditional branch. If its successor is now
358 // its layout successor, delete the branch.
359 if (isLayoutSuccessor(TBB))
360 TII->RemoveBranch(*this);
362 // The block has an unconditional fallthrough. If its successor is not
363 // its layout successor, insert a branch. First we have to locate the
364 // only non-landing-pad successor, as that is the fallthrough block.
365 for (succ_iterator SI = succ_begin(), SE = succ_end(); SI != SE; ++SI) {
366 if ((*SI)->isLandingPad())
368 assert(!TBB && "Found more than one non-landing-pad successor!");
372 // If there is no non-landing-pad successor, the block has no
373 // fall-through edges to be concerned with.
377 // Finally update the unconditional successor to be reached via a branch
378 // if it would not be reached by fallthrough.
379 if (!isLayoutSuccessor(TBB))
380 TII->InsertBranch(*this, TBB, 0, Cond, dl);
384 // The block has a non-fallthrough conditional branch. If one of its
385 // successors is its layout successor, rewrite it to a fallthrough
386 // conditional branch.
387 if (isLayoutSuccessor(TBB)) {
388 if (TII->ReverseBranchCondition(Cond))
390 TII->RemoveBranch(*this);
391 TII->InsertBranch(*this, FBB, 0, Cond, dl);
392 } else if (isLayoutSuccessor(FBB)) {
393 TII->RemoveBranch(*this);
394 TII->InsertBranch(*this, TBB, 0, Cond, dl);
397 // Walk through the successors and find the successor which is not
398 // a landing pad and is not the conditional branch destination (in TBB)
399 // as the fallthrough successor.
400 MachineBasicBlock *FallthroughBB = 0;
401 for (succ_iterator SI = succ_begin(), SE = succ_end(); SI != SE; ++SI) {
402 if ((*SI)->isLandingPad() || *SI == TBB)
404 assert(!FallthroughBB && "Found more than one fallthrough successor.");
407 if (!FallthroughBB && canFallThrough()) {
408 // We fallthrough to the same basic block as the conditional jump
409 // targets. Remove the conditional jump, leaving unconditional
411 // FIXME: This does not seem like a reasonable pattern to support, but it
412 // has been seen in the wild coming out of degenerate ARM test cases.
413 TII->RemoveBranch(*this);
415 // Finally update the unconditional successor to be reached via a branch
416 // if it would not be reached by fallthrough.
417 if (!isLayoutSuccessor(TBB))
418 TII->InsertBranch(*this, TBB, 0, Cond, dl);
422 // The block has a fallthrough conditional branch.
423 if (isLayoutSuccessor(TBB)) {
424 if (TII->ReverseBranchCondition(Cond)) {
425 // We can't reverse the condition, add an unconditional branch.
427 TII->InsertBranch(*this, FallthroughBB, 0, Cond, dl);
430 TII->RemoveBranch(*this);
431 TII->InsertBranch(*this, FallthroughBB, 0, Cond, dl);
432 } else if (!isLayoutSuccessor(FallthroughBB)) {
433 TII->RemoveBranch(*this);
434 TII->InsertBranch(*this, TBB, FallthroughBB, Cond, dl);
440 void MachineBasicBlock::addSuccessor(MachineBasicBlock *succ, uint32_t weight) {
442 // If we see non-zero value for the first time it means we actually use Weight
443 // list, so we fill all Weights with 0's.
444 if (weight != 0 && Weights.empty())
445 Weights.resize(Successors.size());
447 if (weight != 0 || !Weights.empty())
448 Weights.push_back(weight);
450 Successors.push_back(succ);
451 succ->addPredecessor(this);
454 void MachineBasicBlock::removeSuccessor(MachineBasicBlock *succ) {
455 succ->removePredecessor(this);
456 succ_iterator I = std::find(Successors.begin(), Successors.end(), succ);
457 assert(I != Successors.end() && "Not a current successor!");
459 // If Weight list is empty it means we don't use it (disabled optimization).
460 if (!Weights.empty()) {
461 weight_iterator WI = getWeightIterator(I);
468 MachineBasicBlock::succ_iterator
469 MachineBasicBlock::removeSuccessor(succ_iterator I) {
470 assert(I != Successors.end() && "Not a current successor!");
472 // If Weight list is empty it means we don't use it (disabled optimization).
473 if (!Weights.empty()) {
474 weight_iterator WI = getWeightIterator(I);
478 (*I)->removePredecessor(this);
479 return Successors.erase(I);
482 void MachineBasicBlock::replaceSuccessor(MachineBasicBlock *Old,
483 MachineBasicBlock *New) {
487 succ_iterator E = succ_end();
488 succ_iterator NewI = E;
489 succ_iterator OldI = E;
490 for (succ_iterator I = succ_begin(); I != E; ++I) {
502 assert(OldI != E && "Old is not a successor of this block");
503 Old->removePredecessor(this);
505 // If New isn't already a successor, let it take Old's place.
507 New->addPredecessor(this);
512 // New is already a successor.
513 // Update its weight instead of adding a duplicate edge.
514 if (!Weights.empty()) {
515 weight_iterator OldWI = getWeightIterator(OldI);
516 *getWeightIterator(NewI) += *OldWI;
517 Weights.erase(OldWI);
519 Successors.erase(OldI);
522 void MachineBasicBlock::addPredecessor(MachineBasicBlock *pred) {
523 Predecessors.push_back(pred);
526 void MachineBasicBlock::removePredecessor(MachineBasicBlock *pred) {
527 pred_iterator I = std::find(Predecessors.begin(), Predecessors.end(), pred);
528 assert(I != Predecessors.end() && "Pred is not a predecessor of this block!");
529 Predecessors.erase(I);
532 void MachineBasicBlock::transferSuccessors(MachineBasicBlock *fromMBB) {
536 while (!fromMBB->succ_empty()) {
537 MachineBasicBlock *Succ = *fromMBB->succ_begin();
540 // If Weight list is empty it means we don't use it (disabled optimization).
541 if (!fromMBB->Weights.empty())
542 Weight = *fromMBB->Weights.begin();
544 addSuccessor(Succ, Weight);
545 fromMBB->removeSuccessor(Succ);
550 MachineBasicBlock::transferSuccessorsAndUpdatePHIs(MachineBasicBlock *fromMBB) {
554 while (!fromMBB->succ_empty()) {
555 MachineBasicBlock *Succ = *fromMBB->succ_begin();
557 if (!fromMBB->Weights.empty())
558 Weight = *fromMBB->Weights.begin();
559 addSuccessor(Succ, Weight);
560 fromMBB->removeSuccessor(Succ);
562 // Fix up any PHI nodes in the successor.
563 for (MachineBasicBlock::instr_iterator MI = Succ->instr_begin(),
564 ME = Succ->instr_end(); MI != ME && MI->isPHI(); ++MI)
565 for (unsigned i = 2, e = MI->getNumOperands()+1; i != e; i += 2) {
566 MachineOperand &MO = MI->getOperand(i);
567 if (MO.getMBB() == fromMBB)
573 bool MachineBasicBlock::isPredecessor(const MachineBasicBlock *MBB) const {
574 return std::find(pred_begin(), pred_end(), MBB) != pred_end();
577 bool MachineBasicBlock::isSuccessor(const MachineBasicBlock *MBB) const {
578 return std::find(succ_begin(), succ_end(), MBB) != succ_end();
581 bool MachineBasicBlock::isLayoutSuccessor(const MachineBasicBlock *MBB) const {
582 MachineFunction::const_iterator I(this);
583 return llvm::next(I) == MachineFunction::const_iterator(MBB);
586 bool MachineBasicBlock::canFallThrough() {
587 MachineFunction::iterator Fallthrough = this;
589 // If FallthroughBlock is off the end of the function, it can't fall through.
590 if (Fallthrough == getParent()->end())
593 // If FallthroughBlock isn't a successor, no fallthrough is possible.
594 if (!isSuccessor(Fallthrough))
597 // Analyze the branches, if any, at the end of the block.
598 MachineBasicBlock *TBB = 0, *FBB = 0;
599 SmallVector<MachineOperand, 4> Cond;
600 const TargetInstrInfo *TII = getParent()->getTarget().getInstrInfo();
601 if (TII->AnalyzeBranch(*this, TBB, FBB, Cond)) {
602 // If we couldn't analyze the branch, examine the last instruction.
603 // If the block doesn't end in a known control barrier, assume fallthrough
604 // is possible. The isPredicated check is needed because this code can be
605 // called during IfConversion, where an instruction which is normally a
606 // Barrier is predicated and thus no longer an actual control barrier.
607 return empty() || !back().isBarrier() || TII->isPredicated(&back());
610 // If there is no branch, control always falls through.
611 if (TBB == 0) return true;
613 // If there is some explicit branch to the fallthrough block, it can obviously
614 // reach, even though the branch should get folded to fall through implicitly.
615 if (MachineFunction::iterator(TBB) == Fallthrough ||
616 MachineFunction::iterator(FBB) == Fallthrough)
619 // If it's an unconditional branch to some block not the fall through, it
620 // doesn't fall through.
621 if (Cond.empty()) return false;
623 // Otherwise, if it is conditional and has no explicit false block, it falls
629 MachineBasicBlock::SplitCriticalEdge(MachineBasicBlock *Succ, Pass *P) {
630 // Splitting the critical edge to a landing pad block is non-trivial. Don't do
631 // it in this generic function.
632 if (Succ->isLandingPad())
635 MachineFunction *MF = getParent();
636 DebugLoc dl; // FIXME: this is nowhere
638 // We may need to update this's terminator, but we can't do that if
639 // AnalyzeBranch fails. If this uses a jump table, we won't touch it.
640 const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
641 MachineBasicBlock *TBB = 0, *FBB = 0;
642 SmallVector<MachineOperand, 4> Cond;
643 if (TII->AnalyzeBranch(*this, TBB, FBB, Cond))
646 // Avoid bugpoint weirdness: A block may end with a conditional branch but
647 // jumps to the same MBB is either case. We have duplicate CFG edges in that
648 // case that we can't handle. Since this never happens in properly optimized
649 // code, just skip those edges.
650 if (TBB && TBB == FBB) {
651 DEBUG(dbgs() << "Won't split critical edge after degenerate BB#"
652 << getNumber() << '\n');
656 MachineBasicBlock *NMBB = MF->CreateMachineBasicBlock();
657 MF->insert(llvm::next(MachineFunction::iterator(this)), NMBB);
658 DEBUG(dbgs() << "Splitting critical edge:"
659 " BB#" << getNumber()
660 << " -- BB#" << NMBB->getNumber()
661 << " -- BB#" << Succ->getNumber() << '\n');
663 // On some targets like Mips, branches may kill virtual registers. Make sure
664 // that LiveVariables is properly updated after updateTerminator replaces the
666 LiveVariables *LV = P->getAnalysisIfAvailable<LiveVariables>();
668 // Collect a list of virtual registers killed by the terminators.
669 SmallVector<unsigned, 4> KilledRegs;
671 for (instr_iterator I = getFirstInstrTerminator(), E = instr_end();
673 MachineInstr *MI = I;
674 for (MachineInstr::mop_iterator OI = MI->operands_begin(),
675 OE = MI->operands_end(); OI != OE; ++OI) {
676 if (!OI->isReg() || OI->getReg() == 0 ||
677 !OI->isUse() || !OI->isKill() || OI->isUndef())
679 unsigned Reg = OI->getReg();
680 if (TargetRegisterInfo::isPhysicalRegister(Reg) ||
681 LV->getVarInfo(Reg).removeKill(MI)) {
682 KilledRegs.push_back(Reg);
683 DEBUG(dbgs() << "Removing terminator kill: " << *MI);
684 OI->setIsKill(false);
689 ReplaceUsesOfBlockWith(Succ, NMBB);
692 // Insert unconditional "jump Succ" instruction in NMBB if necessary.
693 NMBB->addSuccessor(Succ);
694 if (!NMBB->isLayoutSuccessor(Succ)) {
696 MF->getTarget().getInstrInfo()->InsertBranch(*NMBB, Succ, NULL, Cond, dl);
699 // Fix PHI nodes in Succ so they refer to NMBB instead of this
700 for (MachineBasicBlock::instr_iterator
701 i = Succ->instr_begin(),e = Succ->instr_end();
702 i != e && i->isPHI(); ++i)
703 for (unsigned ni = 1, ne = i->getNumOperands(); ni != ne; ni += 2)
704 if (i->getOperand(ni+1).getMBB() == this)
705 i->getOperand(ni+1).setMBB(NMBB);
707 // Inherit live-ins from the successor
708 for (MachineBasicBlock::livein_iterator I = Succ->livein_begin(),
709 E = Succ->livein_end(); I != E; ++I)
712 // Update LiveVariables.
713 const TargetRegisterInfo *TRI = MF->getTarget().getRegisterInfo();
715 // Restore kills of virtual registers that were killed by the terminators.
716 while (!KilledRegs.empty()) {
717 unsigned Reg = KilledRegs.pop_back_val();
718 for (instr_iterator I = instr_end(), E = instr_begin(); I != E;) {
719 if (!(--I)->addRegisterKilled(Reg, TRI, /* addIfNotFound= */ false))
721 if (TargetRegisterInfo::isVirtualRegister(Reg))
722 LV->getVarInfo(Reg).Kills.push_back(I);
723 DEBUG(dbgs() << "Restored terminator kill: " << *I);
727 // Update relevant live-through information.
728 LV->addNewBlock(NMBB, this, Succ);
731 if (MachineDominatorTree *MDT =
732 P->getAnalysisIfAvailable<MachineDominatorTree>()) {
733 // Update dominator information.
734 MachineDomTreeNode *SucccDTNode = MDT->getNode(Succ);
736 bool IsNewIDom = true;
737 for (const_pred_iterator PI = Succ->pred_begin(), E = Succ->pred_end();
739 MachineBasicBlock *PredBB = *PI;
742 if (!MDT->dominates(SucccDTNode, MDT->getNode(PredBB))) {
748 // We know "this" dominates the newly created basic block.
749 MachineDomTreeNode *NewDTNode = MDT->addNewBlock(NMBB, this);
751 // If all the other predecessors of "Succ" are dominated by "Succ" itself
752 // then the new block is the new immediate dominator of "Succ". Otherwise,
753 // the new block doesn't dominate anything.
755 MDT->changeImmediateDominator(SucccDTNode, NewDTNode);
758 if (MachineLoopInfo *MLI = P->getAnalysisIfAvailable<MachineLoopInfo>())
759 if (MachineLoop *TIL = MLI->getLoopFor(this)) {
760 // If one or the other blocks were not in a loop, the new block is not
761 // either, and thus LI doesn't need to be updated.
762 if (MachineLoop *DestLoop = MLI->getLoopFor(Succ)) {
763 if (TIL == DestLoop) {
764 // Both in the same loop, the NMBB joins loop.
765 DestLoop->addBasicBlockToLoop(NMBB, MLI->getBase());
766 } else if (TIL->contains(DestLoop)) {
767 // Edge from an outer loop to an inner loop. Add to the outer loop.
768 TIL->addBasicBlockToLoop(NMBB, MLI->getBase());
769 } else if (DestLoop->contains(TIL)) {
770 // Edge from an inner loop to an outer loop. Add to the outer loop.
771 DestLoop->addBasicBlockToLoop(NMBB, MLI->getBase());
773 // Edge from two loops with no containment relation. Because these
774 // are natural loops, we know that the destination block must be the
775 // header of its loop (adding a branch into a loop elsewhere would
776 // create an irreducible loop).
777 assert(DestLoop->getHeader() == Succ &&
778 "Should not create irreducible loops!");
779 if (MachineLoop *P = DestLoop->getParentLoop())
780 P->addBasicBlockToLoop(NMBB, MLI->getBase());
788 MachineBasicBlock::iterator
789 MachineBasicBlock::erase(MachineBasicBlock::iterator I) {
791 MachineBasicBlock::iterator E = llvm::next(I);
792 return Insts.erase(I.getInstrIterator(), E.getInstrIterator());
795 return Insts.erase(I.getInstrIterator());
798 MachineInstr *MachineBasicBlock::remove(MachineInstr *I) {
800 instr_iterator MII = llvm::next(I);
802 while (MII != E && MII->isInsideBundle()) {
803 MachineInstr *MI = &*MII++;
808 return Insts.remove(I);
811 void MachineBasicBlock::splice(MachineBasicBlock::iterator where,
812 MachineBasicBlock *Other,
813 MachineBasicBlock::iterator From) {
814 if (From->isBundle()) {
815 MachineBasicBlock::iterator To = llvm::next(From);
816 Insts.splice(where.getInstrIterator(), Other->Insts,
817 From.getInstrIterator(), To.getInstrIterator());
821 Insts.splice(where.getInstrIterator(), Other->Insts, From.getInstrIterator());
824 /// removeFromParent - This method unlinks 'this' from the containing function,
825 /// and returns it, but does not delete it.
826 MachineBasicBlock *MachineBasicBlock::removeFromParent() {
827 assert(getParent() && "Not embedded in a function!");
828 getParent()->remove(this);
833 /// eraseFromParent - This method unlinks 'this' from the containing function,
835 void MachineBasicBlock::eraseFromParent() {
836 assert(getParent() && "Not embedded in a function!");
837 getParent()->erase(this);
841 /// ReplaceUsesOfBlockWith - Given a machine basic block that branched to
842 /// 'Old', change the code and CFG so that it branches to 'New' instead.
843 void MachineBasicBlock::ReplaceUsesOfBlockWith(MachineBasicBlock *Old,
844 MachineBasicBlock *New) {
845 assert(Old != New && "Cannot replace self with self!");
847 MachineBasicBlock::instr_iterator I = instr_end();
848 while (I != instr_begin()) {
850 if (!I->isTerminator()) break;
852 // Scan the operands of this machine instruction, replacing any uses of Old
854 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
855 if (I->getOperand(i).isMBB() &&
856 I->getOperand(i).getMBB() == Old)
857 I->getOperand(i).setMBB(New);
860 // Update the successor information.
861 replaceSuccessor(Old, New);
864 /// CorrectExtraCFGEdges - Various pieces of code can cause excess edges in the
865 /// CFG to be inserted. If we have proven that MBB can only branch to DestA and
866 /// DestB, remove any other MBB successors from the CFG. DestA and DestB can be
869 /// Besides DestA and DestB, retain other edges leading to LandingPads
870 /// (currently there can be only one; we don't check or require that here).
871 /// Note it is possible that DestA and/or DestB are LandingPads.
872 bool MachineBasicBlock::CorrectExtraCFGEdges(MachineBasicBlock *DestA,
873 MachineBasicBlock *DestB,
875 // The values of DestA and DestB frequently come from a call to the
876 // 'TargetInstrInfo::AnalyzeBranch' method. We take our meaning of the initial
877 // values from there.
879 // 1. If both DestA and DestB are null, then the block ends with no branches
880 // (it falls through to its successor).
881 // 2. If DestA is set, DestB is null, and isCond is false, then the block ends
882 // with only an unconditional branch.
883 // 3. If DestA is set, DestB is null, and isCond is true, then the block ends
884 // with a conditional branch that falls through to a successor (DestB).
885 // 4. If DestA and DestB is set and isCond is true, then the block ends with a
886 // conditional branch followed by an unconditional branch. DestA is the
887 // 'true' destination and DestB is the 'false' destination.
889 bool Changed = false;
891 MachineFunction::iterator FallThru =
892 llvm::next(MachineFunction::iterator(this));
894 if (DestA == 0 && DestB == 0) {
895 // Block falls through to successor.
898 } else if (DestA != 0 && DestB == 0) {
900 // Block ends in conditional jump that falls through to successor.
903 assert(DestA && DestB && isCond &&
904 "CFG in a bad state. Cannot correct CFG edges");
907 // Remove superfluous edges. I.e., those which aren't destinations of this
908 // basic block, duplicate edges, or landing pads.
909 SmallPtrSet<const MachineBasicBlock*, 8> SeenMBBs;
910 MachineBasicBlock::succ_iterator SI = succ_begin();
911 while (SI != succ_end()) {
912 const MachineBasicBlock *MBB = *SI;
913 if (!SeenMBBs.insert(MBB) ||
914 (MBB != DestA && MBB != DestB && !MBB->isLandingPad())) {
915 // This is a superfluous edge, remove it.
916 SI = removeSuccessor(SI);
926 /// findDebugLoc - find the next valid DebugLoc starting at MBBI, skipping
927 /// any DBG_VALUE instructions. Return UnknownLoc if there is none.
929 MachineBasicBlock::findDebugLoc(instr_iterator MBBI) {
931 instr_iterator E = instr_end();
935 // Skip debug declarations, we don't want a DebugLoc from them.
936 while (MBBI != E && MBBI->isDebugValue())
939 DL = MBBI->getDebugLoc();
943 /// getSuccWeight - Return weight of the edge from this block to MBB.
945 uint32_t MachineBasicBlock::getSuccWeight(const_succ_iterator Succ) const {
949 return *getWeightIterator(Succ);
952 /// getWeightIterator - Return wight iterator corresonding to the I successor
954 MachineBasicBlock::weight_iterator MachineBasicBlock::
955 getWeightIterator(MachineBasicBlock::succ_iterator I) {
956 assert(Weights.size() == Successors.size() && "Async weight list!");
957 size_t index = std::distance(Successors.begin(), I);
958 assert(index < Weights.size() && "Not a current successor!");
959 return Weights.begin() + index;
962 /// getWeightIterator - Return wight iterator corresonding to the I successor
964 MachineBasicBlock::const_weight_iterator MachineBasicBlock::
965 getWeightIterator(MachineBasicBlock::const_succ_iterator I) const {
966 assert(Weights.size() == Successors.size() && "Async weight list!");
967 const size_t index = std::distance(Successors.begin(), I);
968 assert(index < Weights.size() && "Not a current successor!");
969 return Weights.begin() + index;
972 void llvm::WriteAsOperand(raw_ostream &OS, const MachineBasicBlock *MBB,
974 OS << "BB#" << MBB->getNumber();