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 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
232 void MachineBasicBlock::dump() const {
237 StringRef MachineBasicBlock::getName() const {
238 if (const BasicBlock *LBB = getBasicBlock())
239 return LBB->getName();
244 /// Return a hopefully unique identifier for this block.
245 std::string MachineBasicBlock::getFullName() const {
248 Name = (getParent()->getName() + ":").str();
250 Name += getBasicBlock()->getName();
252 Name += (Twine("BB") + Twine(getNumber())).str();
256 void MachineBasicBlock::print(raw_ostream &OS, SlotIndexes *Indexes) const {
257 const MachineFunction *MF = getParent();
259 OS << "Can't print out MachineBasicBlock because parent MachineFunction"
265 OS << Indexes->getMBBStartIdx(this) << '\t';
267 OS << "BB#" << getNumber() << ": ";
269 const char *Comma = "";
270 if (const BasicBlock *LBB = getBasicBlock()) {
271 OS << Comma << "derived from LLVM BB ";
272 WriteAsOperand(OS, LBB, /*PrintType=*/false);
275 if (isLandingPad()) { OS << Comma << "EH LANDING PAD"; Comma = ", "; }
276 if (hasAddressTaken()) { OS << Comma << "ADDRESS TAKEN"; Comma = ", "; }
278 OS << Comma << "Align " << Alignment << " (" << (1u << Alignment)
283 const TargetRegisterInfo *TRI = MF->getTarget().getRegisterInfo();
284 if (!livein_empty()) {
285 if (Indexes) OS << '\t';
287 for (livein_iterator I = livein_begin(),E = livein_end(); I != E; ++I)
288 OS << ' ' << PrintReg(*I, TRI);
291 // Print the preds of this block according to the CFG.
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();
300 for (const_instr_iterator I = instr_begin(); I != instr_end(); ++I) {
302 if (Indexes->hasIndex(I))
303 OS << Indexes->getInstructionIndex(I);
307 if (I->isInsideBundle())
309 I->print(OS, &getParent()->getTarget());
312 // Print the successors of this block according to the CFG.
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) << ')';
325 void MachineBasicBlock::removeLiveIn(unsigned Reg) {
326 std::vector<unsigned>::iterator I =
327 std::find(LiveIns.begin(), LiveIns.end(), Reg);
328 if (I != LiveIns.end())
332 bool MachineBasicBlock::isLiveIn(unsigned Reg) const {
333 livein_iterator I = std::find(livein_begin(), livein_end(), Reg);
334 return I != livein_end();
337 void MachineBasicBlock::moveBefore(MachineBasicBlock *NewAfter) {
338 getParent()->splice(NewAfter, this);
341 void MachineBasicBlock::moveAfter(MachineBasicBlock *NewBefore) {
342 MachineFunction::iterator BBI = NewBefore;
343 getParent()->splice(++BBI, this);
346 void 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;
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);
356 assert(!B && "UpdateTerminators requires analyzable predecessors!");
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);
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())
370 assert(!TBB && "Found more than one non-landing-pad successor!");
374 // If there is no non-landing-pad successor, the block has no
375 // fall-through edges to be concerned with.
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);
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))
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);
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)
406 assert(!FallthroughBB && "Found more than one fallthrough successor.");
409 if (!FallthroughBB && canFallThrough()) {
410 // We fallthrough to the same basic block as the conditional jump
411 // targets. Remove the conditional jump, leaving unconditional
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);
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);
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.
429 TII->InsertBranch(*this, FallthroughBB, 0, Cond, dl);
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);
442 void MachineBasicBlock::addSuccessor(MachineBasicBlock *succ, uint32_t weight) {
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());
449 if (weight != 0 || !Weights.empty())
450 Weights.push_back(weight);
452 Successors.push_back(succ);
453 succ->addPredecessor(this);
456 void 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!");
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);
470 MachineBasicBlock::succ_iterator
471 MachineBasicBlock::removeSuccessor(succ_iterator I) {
472 assert(I != Successors.end() && "Not a current successor!");
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);
480 (*I)->removePredecessor(this);
481 return Successors.erase(I);
484 void MachineBasicBlock::replaceSuccessor(MachineBasicBlock *Old,
485 MachineBasicBlock *New) {
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) {
504 assert(OldI != E && "Old is not a successor of this block");
505 Old->removePredecessor(this);
507 // If New isn't already a successor, let it take Old's place.
509 New->addPredecessor(this);
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);
521 Successors.erase(OldI);
524 void MachineBasicBlock::addPredecessor(MachineBasicBlock *pred) {
525 Predecessors.push_back(pred);
528 void 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);
534 void MachineBasicBlock::transferSuccessors(MachineBasicBlock *fromMBB) {
538 while (!fromMBB->succ_empty()) {
539 MachineBasicBlock *Succ = *fromMBB->succ_begin();
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();
546 addSuccessor(Succ, Weight);
547 fromMBB->removeSuccessor(Succ);
552 MachineBasicBlock::transferSuccessorsAndUpdatePHIs(MachineBasicBlock *fromMBB) {
556 while (!fromMBB->succ_empty()) {
557 MachineBasicBlock *Succ = *fromMBB->succ_begin();
559 if (!fromMBB->Weights.empty())
560 Weight = *fromMBB->Weights.begin();
561 addSuccessor(Succ, Weight);
562 fromMBB->removeSuccessor(Succ);
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)
575 bool MachineBasicBlock::isPredecessor(const MachineBasicBlock *MBB) const {
576 return std::find(pred_begin(), pred_end(), MBB) != pred_end();
579 bool MachineBasicBlock::isSuccessor(const MachineBasicBlock *MBB) const {
580 return std::find(succ_begin(), succ_end(), MBB) != succ_end();
583 bool MachineBasicBlock::isLayoutSuccessor(const MachineBasicBlock *MBB) const {
584 MachineFunction::const_iterator I(this);
585 return llvm::next(I) == MachineFunction::const_iterator(MBB);
588 bool MachineBasicBlock::canFallThrough() {
589 MachineFunction::iterator Fallthrough = this;
591 // If FallthroughBlock is off the end of the function, it can't fall through.
592 if (Fallthrough == getParent()->end())
595 // If FallthroughBlock isn't a successor, no fallthrough is possible.
596 if (!isSuccessor(Fallthrough))
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());
612 // If there is no branch, control always falls through.
613 if (TBB == 0) return true;
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)
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;
625 // Otherwise, if it is conditional and has no explicit false block, it falls
631 MachineBasicBlock::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())
637 MachineFunction *MF = getParent();
638 DebugLoc dl; // FIXME: this is nowhere
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))
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');
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');
665 // On some targets like Mips, branches may kill virtual registers. Make sure
666 // that LiveVariables is properly updated after updateTerminator replaces the
668 LiveVariables *LV = P->getAnalysisIfAvailable<LiveVariables>();
670 // Collect a list of virtual registers killed by the terminators.
671 SmallVector<unsigned, 4> KilledRegs;
673 for (instr_iterator I = getFirstInstrTerminator(), E = instr_end();
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())
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);
691 ReplaceUsesOfBlockWith(Succ, NMBB);
694 // Insert unconditional "jump Succ" instruction in NMBB if necessary.
695 NMBB->addSuccessor(Succ);
696 if (!NMBB->isLayoutSuccessor(Succ)) {
698 MF->getTarget().getInstrInfo()->InsertBranch(*NMBB, Succ, NULL, Cond, dl);
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);
709 // Inherit live-ins from the successor
710 for (MachineBasicBlock::livein_iterator I = Succ->livein_begin(),
711 E = Succ->livein_end(); I != E; ++I)
714 // Update LiveVariables.
715 const TargetRegisterInfo *TRI = MF->getTarget().getRegisterInfo();
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))
723 if (TargetRegisterInfo::isVirtualRegister(Reg))
724 LV->getVarInfo(Reg).Kills.push_back(I);
725 DEBUG(dbgs() << "Restored terminator kill: " << *I);
729 // Update relevant live-through information.
730 LV->addNewBlock(NMBB, this, Succ);
733 if (MachineDominatorTree *MDT =
734 P->getAnalysisIfAvailable<MachineDominatorTree>()) {
735 // Update dominator information.
736 MachineDomTreeNode *SucccDTNode = MDT->getNode(Succ);
738 bool IsNewIDom = true;
739 for (const_pred_iterator PI = Succ->pred_begin(), E = Succ->pred_end();
741 MachineBasicBlock *PredBB = *PI;
744 if (!MDT->dominates(SucccDTNode, MDT->getNode(PredBB))) {
750 // We know "this" dominates the newly created basic block.
751 MachineDomTreeNode *NewDTNode = MDT->addNewBlock(NMBB, this);
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.
757 MDT->changeImmediateDominator(SucccDTNode, NewDTNode);
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());
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());
790 MachineBasicBlock::iterator
791 MachineBasicBlock::erase(MachineBasicBlock::iterator I) {
793 MachineBasicBlock::iterator E = llvm::next(I);
794 return Insts.erase(I.getInstrIterator(), E.getInstrIterator());
797 return Insts.erase(I.getInstrIterator());
800 MachineInstr *MachineBasicBlock::remove(MachineInstr *I) {
802 instr_iterator MII = llvm::next(I);
804 while (MII != E && MII->isInsideBundle()) {
805 MachineInstr *MI = &*MII++;
810 return Insts.remove(I);
813 void 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());
823 Insts.splice(where.getInstrIterator(), Other->Insts, From.getInstrIterator());
826 /// removeFromParent - This method unlinks 'this' from the containing function,
827 /// and returns it, but does not delete it.
828 MachineBasicBlock *MachineBasicBlock::removeFromParent() {
829 assert(getParent() && "Not embedded in a function!");
830 getParent()->remove(this);
835 /// eraseFromParent - This method unlinks 'this' from the containing function,
837 void MachineBasicBlock::eraseFromParent() {
838 assert(getParent() && "Not embedded in a function!");
839 getParent()->erase(this);
843 /// ReplaceUsesOfBlockWith - Given a machine basic block that branched to
844 /// 'Old', change the code and CFG so that it branches to 'New' instead.
845 void MachineBasicBlock::ReplaceUsesOfBlockWith(MachineBasicBlock *Old,
846 MachineBasicBlock *New) {
847 assert(Old != New && "Cannot replace self with self!");
849 MachineBasicBlock::instr_iterator I = instr_end();
850 while (I != instr_begin()) {
852 if (!I->isTerminator()) break;
854 // Scan the operands of this machine instruction, replacing any uses of Old
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);
862 // Update the successor information.
863 replaceSuccessor(Old, New);
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
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.
874 bool MachineBasicBlock::CorrectExtraCFGEdges(MachineBasicBlock *DestA,
875 MachineBasicBlock *DestB,
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.
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.
891 bool Changed = false;
893 MachineFunction::iterator FallThru =
894 llvm::next(MachineFunction::iterator(this));
896 if (DestA == 0 && DestB == 0) {
897 // Block falls through to successor.
900 } else if (DestA != 0 && DestB == 0) {
902 // Block ends in conditional jump that falls through to successor.
905 assert(DestA && DestB && isCond &&
906 "CFG in a bad state. Cannot correct CFG edges");
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);
928 /// findDebugLoc - find the next valid DebugLoc starting at MBBI, skipping
929 /// any DBG_VALUE instructions. Return UnknownLoc if there is none.
931 MachineBasicBlock::findDebugLoc(instr_iterator MBBI) {
933 instr_iterator E = instr_end();
937 // Skip debug declarations, we don't want a DebugLoc from them.
938 while (MBBI != E && MBBI->isDebugValue())
941 DL = MBBI->getDebugLoc();
945 /// getSuccWeight - Return weight of the edge from this block to MBB.
947 uint32_t MachineBasicBlock::getSuccWeight(const_succ_iterator Succ) const {
951 return *getWeightIterator(Succ);
954 /// getWeightIterator - Return wight iterator corresonding to the I successor
956 MachineBasicBlock::weight_iterator MachineBasicBlock::
957 getWeightIterator(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;
964 /// getWeightIterator - Return wight iterator corresonding to the I successor
966 MachineBasicBlock::const_weight_iterator MachineBasicBlock::
967 getWeightIterator(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;
974 /// Return whether (physical) register "Reg" has been <def>ined and not <kill>ed
975 /// as of just before "MI".
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.
980 MachineBasicBlock::LivenessQueryResult
981 MachineBasicBlock::computeRegisterLiveness(const TargetRegisterInfo *TRI,
982 unsigned Reg, MachineInstr *MI,
983 unsigned Neighborhood) {
985 unsigned N = Neighborhood;
986 MachineBasicBlock *MBB = MI->getParent();
988 // Start by searching backwards from MI, looking for kills, reads or defs.
990 MachineBasicBlock::iterator I(MI);
991 // If this is the first insn in the block, don't search backwards.
992 if (I != MBB->begin()) {
996 MachineOperandIteratorBase::PhysRegInfo Analysis =
997 MIOperands(I).analyzePhysReg(Reg, TRI);
1000 // Register killed, so isn't live.
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;
1008 } while (I != MBB->begin() && --N > 0);
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;
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);
1033 if (Analysis.ReadsOverlap)
1034 // Used, therefore must have been live.
1035 return (Analysis.Reads) ?
1036 LQR_Live : LQR_OverlappingLive;
1038 else if (Analysis.DefinesOverlap)
1039 // Defined (but not read) therefore cannot have been live.
1044 // At this point we have no idea of the liveness of the register.
1048 void llvm::WriteAsOperand(raw_ostream &OS, const MachineBasicBlock *MBB,
1050 OS << "BB#" << MBB->getNumber();