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()->getFunction()->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();
320 void MachineBasicBlock::removeLiveIn(unsigned Reg) {
321 std::vector<unsigned>::iterator I =
322 std::find(LiveIns.begin(), LiveIns.end(), Reg);
323 if (I != LiveIns.end())
327 bool MachineBasicBlock::isLiveIn(unsigned Reg) const {
328 livein_iterator I = std::find(livein_begin(), livein_end(), Reg);
329 return I != livein_end();
332 void MachineBasicBlock::moveBefore(MachineBasicBlock *NewAfter) {
333 getParent()->splice(NewAfter, this);
336 void MachineBasicBlock::moveAfter(MachineBasicBlock *NewBefore) {
337 MachineFunction::iterator BBI = NewBefore;
338 getParent()->splice(++BBI, this);
341 void MachineBasicBlock::updateTerminator() {
342 const TargetInstrInfo *TII = getParent()->getTarget().getInstrInfo();
343 // A block with no successors has no concerns with fall-through edges.
344 if (this->succ_empty()) return;
346 MachineBasicBlock *TBB = 0, *FBB = 0;
347 SmallVector<MachineOperand, 4> Cond;
348 DebugLoc dl; // FIXME: this is nowhere
349 bool B = TII->AnalyzeBranch(*this, TBB, FBB, Cond);
351 assert(!B && "UpdateTerminators requires analyzable predecessors!");
354 // The block has an unconditional branch. If its successor is now
355 // its layout successor, delete the branch.
356 if (isLayoutSuccessor(TBB))
357 TII->RemoveBranch(*this);
359 // The block has an unconditional fallthrough. If its successor is not
360 // its layout successor, insert a branch. First we have to locate the
361 // only non-landing-pad successor, as that is the fallthrough block.
362 for (succ_iterator SI = succ_begin(), SE = succ_end(); SI != SE; ++SI) {
363 if ((*SI)->isLandingPad())
365 assert(!TBB && "Found more than one non-landing-pad successor!");
369 // If there is no non-landing-pad successor, the block has no
370 // fall-through edges to be concerned with.
374 // Finally update the unconditional successor to be reached via a branch
375 // if it would not be reached by fallthrough.
376 if (!isLayoutSuccessor(TBB))
377 TII->InsertBranch(*this, TBB, 0, Cond, dl);
381 // The block has a non-fallthrough conditional branch. If one of its
382 // successors is its layout successor, rewrite it to a fallthrough
383 // conditional branch.
384 if (isLayoutSuccessor(TBB)) {
385 if (TII->ReverseBranchCondition(Cond))
387 TII->RemoveBranch(*this);
388 TII->InsertBranch(*this, FBB, 0, Cond, dl);
389 } else if (isLayoutSuccessor(FBB)) {
390 TII->RemoveBranch(*this);
391 TII->InsertBranch(*this, TBB, 0, Cond, dl);
394 // Walk through the successors and find the successor which is not
395 // a landing pad and is not the conditional branch destination (in TBB)
396 // as the fallthrough successor.
397 MachineBasicBlock *FallthroughBB = 0;
398 for (succ_iterator SI = succ_begin(), SE = succ_end(); SI != SE; ++SI) {
399 if ((*SI)->isLandingPad() || *SI == TBB)
401 assert(!FallthroughBB && "Found more than one fallthrough successor.");
404 if (!FallthroughBB && canFallThrough()) {
405 // We fallthrough to the same basic block as the conditional jump
406 // targets. Remove the conditional jump, leaving unconditional
408 // FIXME: This does not seem like a reasonable pattern to support, but it
409 // has been seen in the wild coming out of degenerate ARM test cases.
410 TII->RemoveBranch(*this);
412 // Finally update the unconditional successor to be reached via a branch
413 // if it would not be reached by fallthrough.
414 if (!isLayoutSuccessor(TBB))
415 TII->InsertBranch(*this, TBB, 0, Cond, dl);
419 // The block has a fallthrough conditional branch.
420 if (isLayoutSuccessor(TBB)) {
421 if (TII->ReverseBranchCondition(Cond)) {
422 // We can't reverse the condition, add an unconditional branch.
424 TII->InsertBranch(*this, FallthroughBB, 0, Cond, dl);
427 TII->RemoveBranch(*this);
428 TII->InsertBranch(*this, FallthroughBB, 0, Cond, dl);
429 } else if (!isLayoutSuccessor(FallthroughBB)) {
430 TII->RemoveBranch(*this);
431 TII->InsertBranch(*this, TBB, FallthroughBB, Cond, dl);
437 void MachineBasicBlock::addSuccessor(MachineBasicBlock *succ, uint32_t weight) {
439 // If we see non-zero value for the first time it means we actually use Weight
440 // list, so we fill all Weights with 0's.
441 if (weight != 0 && Weights.empty())
442 Weights.resize(Successors.size());
444 if (weight != 0 || !Weights.empty())
445 Weights.push_back(weight);
447 Successors.push_back(succ);
448 succ->addPredecessor(this);
451 void MachineBasicBlock::removeSuccessor(MachineBasicBlock *succ) {
452 succ->removePredecessor(this);
453 succ_iterator I = std::find(Successors.begin(), Successors.end(), succ);
454 assert(I != Successors.end() && "Not a current successor!");
456 // If Weight list is empty it means we don't use it (disabled optimization).
457 if (!Weights.empty()) {
458 weight_iterator WI = getWeightIterator(I);
465 MachineBasicBlock::succ_iterator
466 MachineBasicBlock::removeSuccessor(succ_iterator I) {
467 assert(I != Successors.end() && "Not a current successor!");
469 // If Weight list is empty it means we don't use it (disabled optimization).
470 if (!Weights.empty()) {
471 weight_iterator WI = getWeightIterator(I);
475 (*I)->removePredecessor(this);
476 return Successors.erase(I);
479 void MachineBasicBlock::replaceSuccessor(MachineBasicBlock *Old,
480 MachineBasicBlock *New) {
482 succ_iterator SI = std::find(Successors.begin(), Successors.end(), Old);
484 // If Weight list is empty it means we don't use it (disabled optimization).
485 if (!Weights.empty()) {
486 weight_iterator WI = getWeightIterator(SI);
490 // Update the successor information.
492 addSuccessor(New, weight);
495 void MachineBasicBlock::addPredecessor(MachineBasicBlock *pred) {
496 Predecessors.push_back(pred);
499 void MachineBasicBlock::removePredecessor(MachineBasicBlock *pred) {
500 pred_iterator I = std::find(Predecessors.begin(), Predecessors.end(), pred);
501 assert(I != Predecessors.end() && "Pred is not a predecessor of this block!");
502 Predecessors.erase(I);
505 void MachineBasicBlock::transferSuccessors(MachineBasicBlock *fromMBB) {
509 while (!fromMBB->succ_empty()) {
510 MachineBasicBlock *Succ = *fromMBB->succ_begin();
514 // If Weight list is empty it means we don't use it (disabled optimization).
515 if (!fromMBB->Weights.empty())
516 weight = *fromMBB->Weights.begin();
518 addSuccessor(Succ, weight);
519 fromMBB->removeSuccessor(Succ);
524 MachineBasicBlock::transferSuccessorsAndUpdatePHIs(MachineBasicBlock *fromMBB) {
528 while (!fromMBB->succ_empty()) {
529 MachineBasicBlock *Succ = *fromMBB->succ_begin();
531 fromMBB->removeSuccessor(Succ);
533 // Fix up any PHI nodes in the successor.
534 for (MachineBasicBlock::instr_iterator MI = Succ->instr_begin(),
535 ME = Succ->instr_end(); MI != ME && MI->isPHI(); ++MI)
536 for (unsigned i = 2, e = MI->getNumOperands()+1; i != e; i += 2) {
537 MachineOperand &MO = MI->getOperand(i);
538 if (MO.getMBB() == fromMBB)
544 bool MachineBasicBlock::isPredecessor(const MachineBasicBlock *MBB) const {
545 return std::find(pred_begin(), pred_end(), MBB) != pred_end();
548 bool MachineBasicBlock::isSuccessor(const MachineBasicBlock *MBB) const {
549 return std::find(succ_begin(), succ_end(), MBB) != succ_end();
552 bool MachineBasicBlock::isLayoutSuccessor(const MachineBasicBlock *MBB) const {
553 MachineFunction::const_iterator I(this);
554 return llvm::next(I) == MachineFunction::const_iterator(MBB);
557 bool MachineBasicBlock::canFallThrough() {
558 MachineFunction::iterator Fallthrough = this;
560 // If FallthroughBlock is off the end of the function, it can't fall through.
561 if (Fallthrough == getParent()->end())
564 // If FallthroughBlock isn't a successor, no fallthrough is possible.
565 if (!isSuccessor(Fallthrough))
568 // Analyze the branches, if any, at the end of the block.
569 MachineBasicBlock *TBB = 0, *FBB = 0;
570 SmallVector<MachineOperand, 4> Cond;
571 const TargetInstrInfo *TII = getParent()->getTarget().getInstrInfo();
572 if (TII->AnalyzeBranch(*this, TBB, FBB, Cond)) {
573 // If we couldn't analyze the branch, examine the last instruction.
574 // If the block doesn't end in a known control barrier, assume fallthrough
575 // is possible. The isPredicated check is needed because this code can be
576 // called during IfConversion, where an instruction which is normally a
577 // Barrier is predicated and thus no longer an actual control barrier.
578 return empty() || !back().isBarrier() || TII->isPredicated(&back());
581 // If there is no branch, control always falls through.
582 if (TBB == 0) return true;
584 // If there is some explicit branch to the fallthrough block, it can obviously
585 // reach, even though the branch should get folded to fall through implicitly.
586 if (MachineFunction::iterator(TBB) == Fallthrough ||
587 MachineFunction::iterator(FBB) == Fallthrough)
590 // If it's an unconditional branch to some block not the fall through, it
591 // doesn't fall through.
592 if (Cond.empty()) return false;
594 // Otherwise, if it is conditional and has no explicit false block, it falls
600 MachineBasicBlock::SplitCriticalEdge(MachineBasicBlock *Succ, Pass *P) {
601 // Splitting the critical edge to a landing pad block is non-trivial. Don't do
602 // it in this generic function.
603 if (Succ->isLandingPad())
606 MachineFunction *MF = getParent();
607 DebugLoc dl; // FIXME: this is nowhere
609 // We may need to update this's terminator, but we can't do that if
610 // AnalyzeBranch fails. If this uses a jump table, we won't touch it.
611 const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
612 MachineBasicBlock *TBB = 0, *FBB = 0;
613 SmallVector<MachineOperand, 4> Cond;
614 if (TII->AnalyzeBranch(*this, TBB, FBB, Cond))
617 // Avoid bugpoint weirdness: A block may end with a conditional branch but
618 // jumps to the same MBB is either case. We have duplicate CFG edges in that
619 // case that we can't handle. Since this never happens in properly optimized
620 // code, just skip those edges.
621 if (TBB && TBB == FBB) {
622 DEBUG(dbgs() << "Won't split critical edge after degenerate BB#"
623 << getNumber() << '\n');
627 MachineBasicBlock *NMBB = MF->CreateMachineBasicBlock();
628 MF->insert(llvm::next(MachineFunction::iterator(this)), NMBB);
629 DEBUG(dbgs() << "Splitting critical edge:"
630 " BB#" << getNumber()
631 << " -- BB#" << NMBB->getNumber()
632 << " -- BB#" << Succ->getNumber() << '\n');
634 // On some targets like Mips, branches may kill virtual registers. Make sure
635 // that LiveVariables is properly updated after updateTerminator replaces the
637 LiveVariables *LV = P->getAnalysisIfAvailable<LiveVariables>();
639 // Collect a list of virtual registers killed by the terminators.
640 SmallVector<unsigned, 4> KilledRegs;
642 for (instr_iterator I = getFirstInstrTerminator(), E = instr_end();
644 MachineInstr *MI = I;
645 for (MachineInstr::mop_iterator OI = MI->operands_begin(),
646 OE = MI->operands_end(); OI != OE; ++OI) {
647 if (!OI->isReg() || OI->getReg() == 0 ||
648 !OI->isUse() || !OI->isKill() || OI->isUndef())
650 unsigned Reg = OI->getReg();
651 if (TargetRegisterInfo::isPhysicalRegister(Reg) ||
652 LV->getVarInfo(Reg).removeKill(MI)) {
653 KilledRegs.push_back(Reg);
654 DEBUG(dbgs() << "Removing terminator kill: " << *MI);
655 OI->setIsKill(false);
660 ReplaceUsesOfBlockWith(Succ, NMBB);
663 // Insert unconditional "jump Succ" instruction in NMBB if necessary.
664 NMBB->addSuccessor(Succ);
665 if (!NMBB->isLayoutSuccessor(Succ)) {
667 MF->getTarget().getInstrInfo()->InsertBranch(*NMBB, Succ, NULL, Cond, dl);
670 // Fix PHI nodes in Succ so they refer to NMBB instead of this
671 for (MachineBasicBlock::instr_iterator
672 i = Succ->instr_begin(),e = Succ->instr_end();
673 i != e && i->isPHI(); ++i)
674 for (unsigned ni = 1, ne = i->getNumOperands(); ni != ne; ni += 2)
675 if (i->getOperand(ni+1).getMBB() == this)
676 i->getOperand(ni+1).setMBB(NMBB);
678 // Inherit live-ins from the successor
679 for (MachineBasicBlock::livein_iterator I = Succ->livein_begin(),
680 E = Succ->livein_end(); I != E; ++I)
683 // Update LiveVariables.
684 const TargetRegisterInfo *TRI = MF->getTarget().getRegisterInfo();
686 // Restore kills of virtual registers that were killed by the terminators.
687 while (!KilledRegs.empty()) {
688 unsigned Reg = KilledRegs.pop_back_val();
689 for (instr_iterator I = instr_end(), E = instr_begin(); I != E;) {
690 if (!(--I)->addRegisterKilled(Reg, TRI, /* addIfNotFound= */ false))
692 if (TargetRegisterInfo::isVirtualRegister(Reg))
693 LV->getVarInfo(Reg).Kills.push_back(I);
694 DEBUG(dbgs() << "Restored terminator kill: " << *I);
698 // Update relevant live-through information.
699 LV->addNewBlock(NMBB, this, Succ);
702 if (MachineDominatorTree *MDT =
703 P->getAnalysisIfAvailable<MachineDominatorTree>()) {
704 // Update dominator information.
705 MachineDomTreeNode *SucccDTNode = MDT->getNode(Succ);
707 bool IsNewIDom = true;
708 for (const_pred_iterator PI = Succ->pred_begin(), E = Succ->pred_end();
710 MachineBasicBlock *PredBB = *PI;
713 if (!MDT->dominates(SucccDTNode, MDT->getNode(PredBB))) {
719 // We know "this" dominates the newly created basic block.
720 MachineDomTreeNode *NewDTNode = MDT->addNewBlock(NMBB, this);
722 // If all the other predecessors of "Succ" are dominated by "Succ" itself
723 // then the new block is the new immediate dominator of "Succ". Otherwise,
724 // the new block doesn't dominate anything.
726 MDT->changeImmediateDominator(SucccDTNode, NewDTNode);
729 if (MachineLoopInfo *MLI = P->getAnalysisIfAvailable<MachineLoopInfo>())
730 if (MachineLoop *TIL = MLI->getLoopFor(this)) {
731 // If one or the other blocks were not in a loop, the new block is not
732 // either, and thus LI doesn't need to be updated.
733 if (MachineLoop *DestLoop = MLI->getLoopFor(Succ)) {
734 if (TIL == DestLoop) {
735 // Both in the same loop, the NMBB joins loop.
736 DestLoop->addBasicBlockToLoop(NMBB, MLI->getBase());
737 } else if (TIL->contains(DestLoop)) {
738 // Edge from an outer loop to an inner loop. Add to the outer loop.
739 TIL->addBasicBlockToLoop(NMBB, MLI->getBase());
740 } else if (DestLoop->contains(TIL)) {
741 // Edge from an inner loop to an outer loop. Add to the outer loop.
742 DestLoop->addBasicBlockToLoop(NMBB, MLI->getBase());
744 // Edge from two loops with no containment relation. Because these
745 // are natural loops, we know that the destination block must be the
746 // header of its loop (adding a branch into a loop elsewhere would
747 // create an irreducible loop).
748 assert(DestLoop->getHeader() == Succ &&
749 "Should not create irreducible loops!");
750 if (MachineLoop *P = DestLoop->getParentLoop())
751 P->addBasicBlockToLoop(NMBB, MLI->getBase());
759 MachineBasicBlock::iterator
760 MachineBasicBlock::erase(MachineBasicBlock::iterator I) {
762 MachineBasicBlock::iterator E = llvm::next(I);
763 return Insts.erase(I.getInstrIterator(), E.getInstrIterator());
766 return Insts.erase(I.getInstrIterator());
769 MachineInstr *MachineBasicBlock::remove(MachineInstr *I) {
771 instr_iterator MII = llvm::next(I);
773 while (MII != E && MII->isInsideBundle()) {
774 MachineInstr *MI = &*MII++;
779 return Insts.remove(I);
782 void MachineBasicBlock::splice(MachineBasicBlock::iterator where,
783 MachineBasicBlock *Other,
784 MachineBasicBlock::iterator From) {
785 if (From->isBundle()) {
786 MachineBasicBlock::iterator To = llvm::next(From);
787 Insts.splice(where.getInstrIterator(), Other->Insts,
788 From.getInstrIterator(), To.getInstrIterator());
792 Insts.splice(where.getInstrIterator(), Other->Insts, From.getInstrIterator());
795 /// removeFromParent - This method unlinks 'this' from the containing function,
796 /// and returns it, but does not delete it.
797 MachineBasicBlock *MachineBasicBlock::removeFromParent() {
798 assert(getParent() && "Not embedded in a function!");
799 getParent()->remove(this);
804 /// eraseFromParent - This method unlinks 'this' from the containing function,
806 void MachineBasicBlock::eraseFromParent() {
807 assert(getParent() && "Not embedded in a function!");
808 getParent()->erase(this);
812 /// ReplaceUsesOfBlockWith - Given a machine basic block that branched to
813 /// 'Old', change the code and CFG so that it branches to 'New' instead.
814 void MachineBasicBlock::ReplaceUsesOfBlockWith(MachineBasicBlock *Old,
815 MachineBasicBlock *New) {
816 assert(Old != New && "Cannot replace self with self!");
818 MachineBasicBlock::instr_iterator I = instr_end();
819 while (I != instr_begin()) {
821 if (!I->isTerminator()) break;
823 // Scan the operands of this machine instruction, replacing any uses of Old
825 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
826 if (I->getOperand(i).isMBB() &&
827 I->getOperand(i).getMBB() == Old)
828 I->getOperand(i).setMBB(New);
831 // Update the successor information.
832 replaceSuccessor(Old, New);
835 /// CorrectExtraCFGEdges - Various pieces of code can cause excess edges in the
836 /// CFG to be inserted. If we have proven that MBB can only branch to DestA and
837 /// DestB, remove any other MBB successors from the CFG. DestA and DestB can be
840 /// Besides DestA and DestB, retain other edges leading to LandingPads
841 /// (currently there can be only one; we don't check or require that here).
842 /// Note it is possible that DestA and/or DestB are LandingPads.
843 bool MachineBasicBlock::CorrectExtraCFGEdges(MachineBasicBlock *DestA,
844 MachineBasicBlock *DestB,
846 // The values of DestA and DestB frequently come from a call to the
847 // 'TargetInstrInfo::AnalyzeBranch' method. We take our meaning of the initial
848 // values from there.
850 // 1. If both DestA and DestB are null, then the block ends with no branches
851 // (it falls through to its successor).
852 // 2. If DestA is set, DestB is null, and isCond is false, then the block ends
853 // with only an unconditional branch.
854 // 3. If DestA is set, DestB is null, and isCond is true, then the block ends
855 // with a conditional branch that falls through to a successor (DestB).
856 // 4. If DestA and DestB is set and isCond is true, then the block ends with a
857 // conditional branch followed by an unconditional branch. DestA is the
858 // 'true' destination and DestB is the 'false' destination.
860 bool Changed = false;
862 MachineFunction::iterator FallThru =
863 llvm::next(MachineFunction::iterator(this));
865 if (DestA == 0 && DestB == 0) {
866 // Block falls through to successor.
869 } else if (DestA != 0 && DestB == 0) {
871 // Block ends in conditional jump that falls through to successor.
874 assert(DestA && DestB && isCond &&
875 "CFG in a bad state. Cannot correct CFG edges");
878 // Remove superfluous edges. I.e., those which aren't destinations of this
879 // basic block, duplicate edges, or landing pads.
880 SmallPtrSet<const MachineBasicBlock*, 8> SeenMBBs;
881 MachineBasicBlock::succ_iterator SI = succ_begin();
882 while (SI != succ_end()) {
883 const MachineBasicBlock *MBB = *SI;
884 if (!SeenMBBs.insert(MBB) ||
885 (MBB != DestA && MBB != DestB && !MBB->isLandingPad())) {
886 // This is a superfluous edge, remove it.
887 SI = removeSuccessor(SI);
897 /// findDebugLoc - find the next valid DebugLoc starting at MBBI, skipping
898 /// any DBG_VALUE instructions. Return UnknownLoc if there is none.
900 MachineBasicBlock::findDebugLoc(instr_iterator MBBI) {
902 instr_iterator E = instr_end();
906 // Skip debug declarations, we don't want a DebugLoc from them.
907 while (MBBI != E && MBBI->isDebugValue())
910 DL = MBBI->getDebugLoc();
914 /// getSuccWeight - Return weight of the edge from this block to MBB.
916 uint32_t MachineBasicBlock::getSuccWeight(const MachineBasicBlock *succ) const {
920 const_succ_iterator I = std::find(Successors.begin(), Successors.end(), succ);
921 return *getWeightIterator(I);
924 /// getWeightIterator - Return wight iterator corresonding to the I successor
926 MachineBasicBlock::weight_iterator MachineBasicBlock::
927 getWeightIterator(MachineBasicBlock::succ_iterator I) {
928 assert(Weights.size() == Successors.size() && "Async weight list!");
929 size_t index = std::distance(Successors.begin(), I);
930 assert(index < Weights.size() && "Not a current successor!");
931 return Weights.begin() + index;
934 /// getWeightIterator - Return wight iterator corresonding to the I successor
936 MachineBasicBlock::const_weight_iterator MachineBasicBlock::
937 getWeightIterator(MachineBasicBlock::const_succ_iterator I) const {
938 assert(Weights.size() == Successors.size() && "Async weight list!");
939 const size_t index = std::distance(Successors.begin(), I);
940 assert(index < Weights.size() && "Not a current successor!");
941 return Weights.begin() + index;
944 void llvm::WriteAsOperand(raw_ostream &OS, const MachineBasicBlock *MBB,
946 OS << "BB#" << MBB->getNumber();