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::insn_iterator I = N->insn_begin(), E = N->insn_end();
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 N->RemoveRegOperandsFromUseLists();
116 LeakDetector::addGarbageObject(N);
119 /// transferNodesFromList (MI) - When moving a range of instructions from one
120 /// MBB list to another, we need to update the parent pointers and the use/def
122 void ilist_traits<MachineInstr>::
123 transferNodesFromList(ilist_traits<MachineInstr> &fromList,
124 ilist_iterator<MachineInstr> first,
125 ilist_iterator<MachineInstr> last) {
126 assert(Parent->getParent() == fromList.Parent->getParent() &&
127 "MachineInstr parent mismatch!");
129 // Splice within the same MBB -> no change.
130 if (Parent == fromList.Parent) return;
132 // If splicing between two blocks within the same function, just update the
134 for (; first != last; ++first)
135 first->setParent(Parent);
138 void ilist_traits<MachineInstr>::deleteNode(MachineInstr* MI) {
139 assert(!MI->getParent() && "MI is still in a block!");
140 Parent->getParent()->DeleteMachineInstr(MI);
143 MachineBasicBlock::iterator MachineBasicBlock::getFirstNonPHI() {
144 insn_iterator I = insn_begin();
145 while (I != end() && I->isPHI())
147 assert(!I->isInsideBundle() && "First non-phi MI cannot be inside a bundle!");
151 MachineBasicBlock::iterator
152 MachineBasicBlock::SkipPHIsAndLabels(MachineBasicBlock::iterator I) {
153 while (I != end() && (I->isPHI() || I->isLabel() || I->isDebugValue()))
155 // FIXME: This needs to change if we wish to bundle labels / dbg_values
156 // inside the bundle.
157 assert(!I->isInsideBundle() &&
158 "First non-phi / non-label instruction is inside a bundle!");
162 MachineBasicBlock::iterator MachineBasicBlock::getFirstTerminator() {
164 while (I != begin() && ((--I)->isTerminator() || I->isDebugValue()))
166 while (I != end() && !I->isTerminator())
171 MachineBasicBlock::const_iterator
172 MachineBasicBlock::getFirstTerminator() const {
173 const_iterator I = end();
174 while (I != begin() && ((--I)->isTerminator() || I->isDebugValue()))
176 while (I != end() && !I->isTerminator())
181 MachineBasicBlock::insn_iterator MachineBasicBlock::getFirstInsnTerminator() {
182 insn_iterator I = insn_end();
183 while (I != insn_begin() && ((--I)->isTerminator() || I->isDebugValue()))
185 while (I != insn_end() && !I->isTerminator())
190 MachineBasicBlock::iterator MachineBasicBlock::getLastNonDebugInstr() {
191 // Skip over end-of-block dbg_value instructions.
192 insn_iterator B = insn_begin(), I = insn_end();
195 // Return instruction that starts a bundle.
196 if (I->isDebugValue() || I->isInsideBundle())
200 // The block is all debug values.
204 MachineBasicBlock::const_iterator
205 MachineBasicBlock::getLastNonDebugInstr() const {
206 // Skip over end-of-block dbg_value instructions.
207 const_insn_iterator B = insn_begin(), I = insn_end();
210 // Return instruction that starts a bundle.
211 if (I->isDebugValue() || I->isInsideBundle())
215 // The block is all debug values.
219 const MachineBasicBlock *MachineBasicBlock::getLandingPadSuccessor() const {
220 // A block with a landing pad successor only has one other successor.
223 for (const_succ_iterator I = succ_begin(), E = succ_end(); I != E; ++I)
224 if ((*I)->isLandingPad())
229 void MachineBasicBlock::dump() const {
233 StringRef MachineBasicBlock::getName() const {
234 if (const BasicBlock *LBB = getBasicBlock())
235 return LBB->getName();
240 void MachineBasicBlock::print(raw_ostream &OS, SlotIndexes *Indexes) const {
241 const MachineFunction *MF = getParent();
243 OS << "Can't print out MachineBasicBlock because parent MachineFunction"
249 OS << Indexes->getMBBStartIdx(this) << '\t';
251 OS << "BB#" << getNumber() << ": ";
253 const char *Comma = "";
254 if (const BasicBlock *LBB = getBasicBlock()) {
255 OS << Comma << "derived from LLVM BB ";
256 WriteAsOperand(OS, LBB, /*PrintType=*/false);
259 if (isLandingPad()) { OS << Comma << "EH LANDING PAD"; Comma = ", "; }
260 if (hasAddressTaken()) { OS << Comma << "ADDRESS TAKEN"; Comma = ", "; }
262 OS << Comma << "Align " << Alignment << " (" << (1u << Alignment)
269 const TargetRegisterInfo *TRI = MF->getTarget().getRegisterInfo();
270 if (!livein_empty()) {
271 if (Indexes) OS << '\t';
273 for (livein_iterator I = livein_begin(),E = livein_end(); I != E; ++I)
274 OS << ' ' << PrintReg(*I, TRI);
277 // Print the preds of this block according to the CFG.
279 if (Indexes) OS << '\t';
280 OS << " Predecessors according to CFG:";
281 for (const_pred_iterator PI = pred_begin(), E = pred_end(); PI != E; ++PI)
282 OS << " BB#" << (*PI)->getNumber();
286 for (const_iterator I = begin(); I != end(); ++I) {
288 if (Indexes->hasIndex(I))
289 OS << Indexes->getInstructionIndex(I);
293 I->print(OS, &getParent()->getTarget());
296 // Print the successors of this block according to the CFG.
298 if (Indexes) OS << '\t';
299 OS << " Successors according to CFG:";
300 for (const_succ_iterator SI = succ_begin(), E = succ_end(); SI != E; ++SI)
301 OS << " BB#" << (*SI)->getNumber();
306 void MachineBasicBlock::removeLiveIn(unsigned Reg) {
307 std::vector<unsigned>::iterator I =
308 std::find(LiveIns.begin(), LiveIns.end(), Reg);
309 assert(I != LiveIns.end() && "Not a live in!");
313 bool MachineBasicBlock::isLiveIn(unsigned Reg) const {
314 livein_iterator I = std::find(livein_begin(), livein_end(), Reg);
315 return I != livein_end();
318 void MachineBasicBlock::moveBefore(MachineBasicBlock *NewAfter) {
319 getParent()->splice(NewAfter, this);
322 void MachineBasicBlock::moveAfter(MachineBasicBlock *NewBefore) {
323 MachineFunction::iterator BBI = NewBefore;
324 getParent()->splice(++BBI, this);
327 void MachineBasicBlock::updateTerminator() {
328 const TargetInstrInfo *TII = getParent()->getTarget().getInstrInfo();
329 // A block with no successors has no concerns with fall-through edges.
330 if (this->succ_empty()) return;
332 MachineBasicBlock *TBB = 0, *FBB = 0;
333 SmallVector<MachineOperand, 4> Cond;
334 DebugLoc dl; // FIXME: this is nowhere
335 bool B = TII->AnalyzeBranch(*this, TBB, FBB, Cond);
337 assert(!B && "UpdateTerminators requires analyzable predecessors!");
340 // The block has an unconditional branch. If its successor is now
341 // its layout successor, delete the branch.
342 if (isLayoutSuccessor(TBB))
343 TII->RemoveBranch(*this);
345 // The block has an unconditional fallthrough. If its successor is not
346 // its layout successor, insert a branch. First we have to locate the
347 // only non-landing-pad successor, as that is the fallthrough block.
348 for (succ_iterator SI = succ_begin(), SE = succ_end(); SI != SE; ++SI) {
349 if ((*SI)->isLandingPad())
351 assert(!TBB && "Found more than one non-landing-pad successor!");
355 // If there is no non-landing-pad successor, the block has no
356 // fall-through edges to be concerned with.
360 // Finally update the unconditional successor to be reached via a branch
361 // if it would not be reached by fallthrough.
362 if (!isLayoutSuccessor(TBB))
363 TII->InsertBranch(*this, TBB, 0, Cond, dl);
367 // The block has a non-fallthrough conditional branch. If one of its
368 // successors is its layout successor, rewrite it to a fallthrough
369 // conditional branch.
370 if (isLayoutSuccessor(TBB)) {
371 if (TII->ReverseBranchCondition(Cond))
373 TII->RemoveBranch(*this);
374 TII->InsertBranch(*this, FBB, 0, Cond, dl);
375 } else if (isLayoutSuccessor(FBB)) {
376 TII->RemoveBranch(*this);
377 TII->InsertBranch(*this, TBB, 0, Cond, dl);
380 // The block has a fallthrough conditional branch.
381 MachineBasicBlock *MBBA = *succ_begin();
382 MachineBasicBlock *MBBB = *llvm::next(succ_begin());
383 if (MBBA == TBB) std::swap(MBBB, MBBA);
384 if (isLayoutSuccessor(TBB)) {
385 if (TII->ReverseBranchCondition(Cond)) {
386 // We can't reverse the condition, add an unconditional branch.
388 TII->InsertBranch(*this, MBBA, 0, Cond, dl);
391 TII->RemoveBranch(*this);
392 TII->InsertBranch(*this, MBBA, 0, Cond, dl);
393 } else if (!isLayoutSuccessor(MBBA)) {
394 TII->RemoveBranch(*this);
395 TII->InsertBranch(*this, TBB, MBBA, Cond, dl);
401 void MachineBasicBlock::addSuccessor(MachineBasicBlock *succ, uint32_t weight) {
403 // If we see non-zero value for the first time it means we actually use Weight
404 // list, so we fill all Weights with 0's.
405 if (weight != 0 && Weights.empty())
406 Weights.resize(Successors.size());
408 if (weight != 0 || !Weights.empty())
409 Weights.push_back(weight);
411 Successors.push_back(succ);
412 succ->addPredecessor(this);
415 void MachineBasicBlock::removeSuccessor(MachineBasicBlock *succ) {
416 succ->removePredecessor(this);
417 succ_iterator I = std::find(Successors.begin(), Successors.end(), succ);
418 assert(I != Successors.end() && "Not a current successor!");
420 // If Weight list is empty it means we don't use it (disabled optimization).
421 if (!Weights.empty()) {
422 weight_iterator WI = getWeightIterator(I);
429 MachineBasicBlock::succ_iterator
430 MachineBasicBlock::removeSuccessor(succ_iterator I) {
431 assert(I != Successors.end() && "Not a current successor!");
433 // If Weight list is empty it means we don't use it (disabled optimization).
434 if (!Weights.empty()) {
435 weight_iterator WI = getWeightIterator(I);
439 (*I)->removePredecessor(this);
440 return Successors.erase(I);
443 void MachineBasicBlock::replaceSuccessor(MachineBasicBlock *Old,
444 MachineBasicBlock *New) {
446 succ_iterator SI = std::find(Successors.begin(), Successors.end(), Old);
448 // If Weight list is empty it means we don't use it (disabled optimization).
449 if (!Weights.empty()) {
450 weight_iterator WI = getWeightIterator(SI);
454 // Update the successor information.
456 addSuccessor(New, weight);
459 void MachineBasicBlock::addPredecessor(MachineBasicBlock *pred) {
460 Predecessors.push_back(pred);
463 void MachineBasicBlock::removePredecessor(MachineBasicBlock *pred) {
464 pred_iterator I = std::find(Predecessors.begin(), Predecessors.end(), pred);
465 assert(I != Predecessors.end() && "Pred is not a predecessor of this block!");
466 Predecessors.erase(I);
469 void MachineBasicBlock::transferSuccessors(MachineBasicBlock *fromMBB) {
473 while (!fromMBB->succ_empty()) {
474 MachineBasicBlock *Succ = *fromMBB->succ_begin();
478 // If Weight list is empty it means we don't use it (disabled optimization).
479 if (!fromMBB->Weights.empty())
480 weight = *fromMBB->Weights.begin();
482 addSuccessor(Succ, weight);
483 fromMBB->removeSuccessor(Succ);
488 MachineBasicBlock::transferSuccessorsAndUpdatePHIs(MachineBasicBlock *fromMBB) {
492 while (!fromMBB->succ_empty()) {
493 MachineBasicBlock *Succ = *fromMBB->succ_begin();
495 fromMBB->removeSuccessor(Succ);
497 // Fix up any PHI nodes in the successor.
498 for (MachineBasicBlock::insn_iterator MI = Succ->insn_begin(),
499 ME = Succ->insn_end(); MI != ME && MI->isPHI(); ++MI)
500 for (unsigned i = 2, e = MI->getNumOperands()+1; i != e; i += 2) {
501 MachineOperand &MO = MI->getOperand(i);
502 if (MO.getMBB() == fromMBB)
508 bool MachineBasicBlock::isSuccessor(const MachineBasicBlock *MBB) const {
509 const_succ_iterator I = std::find(Successors.begin(), Successors.end(), MBB);
510 return I != Successors.end();
513 bool MachineBasicBlock::isLayoutSuccessor(const MachineBasicBlock *MBB) const {
514 MachineFunction::const_iterator I(this);
515 return llvm::next(I) == MachineFunction::const_iterator(MBB);
518 bool MachineBasicBlock::canFallThrough() {
519 MachineFunction::iterator Fallthrough = this;
521 // If FallthroughBlock is off the end of the function, it can't fall through.
522 if (Fallthrough == getParent()->end())
525 // If FallthroughBlock isn't a successor, no fallthrough is possible.
526 if (!isSuccessor(Fallthrough))
529 // Analyze the branches, if any, at the end of the block.
530 MachineBasicBlock *TBB = 0, *FBB = 0;
531 SmallVector<MachineOperand, 4> Cond;
532 const TargetInstrInfo *TII = getParent()->getTarget().getInstrInfo();
533 if (TII->AnalyzeBranch(*this, TBB, FBB, Cond)) {
534 // If we couldn't analyze the branch, examine the last instruction.
535 // If the block doesn't end in a known control barrier, assume fallthrough
536 // is possible. The isPredicable check is needed because this code can be
537 // called during IfConversion, where an instruction which is normally a
538 // Barrier is predicated and thus no longer an actual control barrier. This
539 // is over-conservative though, because if an instruction isn't actually
540 // predicated we could still treat it like a barrier.
541 return empty() || !back().isBarrier() ||
542 back().isPredicable();
545 // If there is no branch, control always falls through.
546 if (TBB == 0) return true;
548 // If there is some explicit branch to the fallthrough block, it can obviously
549 // reach, even though the branch should get folded to fall through implicitly.
550 if (MachineFunction::iterator(TBB) == Fallthrough ||
551 MachineFunction::iterator(FBB) == Fallthrough)
554 // If it's an unconditional branch to some block not the fall through, it
555 // doesn't fall through.
556 if (Cond.empty()) return false;
558 // Otherwise, if it is conditional and has no explicit false block, it falls
564 MachineBasicBlock::SplitCriticalEdge(MachineBasicBlock *Succ, Pass *P) {
565 MachineFunction *MF = getParent();
566 DebugLoc dl; // FIXME: this is nowhere
568 // We may need to update this's terminator, but we can't do that if
569 // AnalyzeBranch fails. If this uses a jump table, we won't touch it.
570 const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
571 MachineBasicBlock *TBB = 0, *FBB = 0;
572 SmallVector<MachineOperand, 4> Cond;
573 if (TII->AnalyzeBranch(*this, TBB, FBB, Cond))
576 // Avoid bugpoint weirdness: A block may end with a conditional branch but
577 // jumps to the same MBB is either case. We have duplicate CFG edges in that
578 // case that we can't handle. Since this never happens in properly optimized
579 // code, just skip those edges.
580 if (TBB && TBB == FBB) {
581 DEBUG(dbgs() << "Won't split critical edge after degenerate BB#"
582 << getNumber() << '\n');
586 MachineBasicBlock *NMBB = MF->CreateMachineBasicBlock();
587 MF->insert(llvm::next(MachineFunction::iterator(this)), NMBB);
588 DEBUG(dbgs() << "Splitting critical edge:"
589 " BB#" << getNumber()
590 << " -- BB#" << NMBB->getNumber()
591 << " -- BB#" << Succ->getNumber() << '\n');
593 // On some targets like Mips, branches may kill virtual registers. Make sure
594 // that LiveVariables is properly updated after updateTerminator replaces the
596 LiveVariables *LV = P->getAnalysisIfAvailable<LiveVariables>();
598 // Collect a list of virtual registers killed by the terminators.
599 SmallVector<unsigned, 4> KilledRegs;
601 for (insn_iterator I = getFirstInsnTerminator(), E = insn_end();
603 MachineInstr *MI = I;
604 for (MachineInstr::mop_iterator OI = MI->operands_begin(),
605 OE = MI->operands_end(); OI != OE; ++OI) {
606 if (!OI->isReg() || !OI->isUse() || !OI->isKill() || OI->isUndef())
608 unsigned Reg = OI->getReg();
609 if (TargetRegisterInfo::isVirtualRegister(Reg) &&
610 LV->getVarInfo(Reg).removeKill(MI)) {
611 KilledRegs.push_back(Reg);
612 DEBUG(dbgs() << "Removing terminator kill: " << *MI);
613 OI->setIsKill(false);
618 ReplaceUsesOfBlockWith(Succ, NMBB);
621 // Insert unconditional "jump Succ" instruction in NMBB if necessary.
622 NMBB->addSuccessor(Succ);
623 if (!NMBB->isLayoutSuccessor(Succ)) {
625 MF->getTarget().getInstrInfo()->InsertBranch(*NMBB, Succ, NULL, Cond, dl);
628 // Fix PHI nodes in Succ so they refer to NMBB instead of this
629 for (MachineBasicBlock::insn_iterator
630 i = Succ->insn_begin(),e = Succ->insn_end(); i != e && i->isPHI(); ++i)
631 for (unsigned ni = 1, ne = i->getNumOperands(); ni != ne; ni += 2)
632 if (i->getOperand(ni+1).getMBB() == this)
633 i->getOperand(ni+1).setMBB(NMBB);
635 // Inherit live-ins from the successor
636 for (MachineBasicBlock::livein_iterator I = Succ->livein_begin(),
637 E = Succ->livein_end(); I != E; ++I)
640 // Update LiveVariables.
642 // Restore kills of virtual registers that were killed by the terminators.
643 while (!KilledRegs.empty()) {
644 unsigned Reg = KilledRegs.pop_back_val();
645 for (insn_iterator I = insn_end(), E = insn_begin(); I != E;) {
646 if (!(--I)->addRegisterKilled(Reg, NULL, /* addIfNotFound= */ false))
648 LV->getVarInfo(Reg).Kills.push_back(I);
649 DEBUG(dbgs() << "Restored terminator kill: " << *I);
653 // Update relevant live-through information.
654 LV->addNewBlock(NMBB, this, Succ);
657 if (MachineDominatorTree *MDT =
658 P->getAnalysisIfAvailable<MachineDominatorTree>()) {
659 // Update dominator information.
660 MachineDomTreeNode *SucccDTNode = MDT->getNode(Succ);
662 bool IsNewIDom = true;
663 for (const_pred_iterator PI = Succ->pred_begin(), E = Succ->pred_end();
665 MachineBasicBlock *PredBB = *PI;
668 if (!MDT->dominates(SucccDTNode, MDT->getNode(PredBB))) {
674 // We know "this" dominates the newly created basic block.
675 MachineDomTreeNode *NewDTNode = MDT->addNewBlock(NMBB, this);
677 // If all the other predecessors of "Succ" are dominated by "Succ" itself
678 // then the new block is the new immediate dominator of "Succ". Otherwise,
679 // the new block doesn't dominate anything.
681 MDT->changeImmediateDominator(SucccDTNode, NewDTNode);
684 if (MachineLoopInfo *MLI = P->getAnalysisIfAvailable<MachineLoopInfo>())
685 if (MachineLoop *TIL = MLI->getLoopFor(this)) {
686 // If one or the other blocks were not in a loop, the new block is not
687 // either, and thus LI doesn't need to be updated.
688 if (MachineLoop *DestLoop = MLI->getLoopFor(Succ)) {
689 if (TIL == DestLoop) {
690 // Both in the same loop, the NMBB joins loop.
691 DestLoop->addBasicBlockToLoop(NMBB, MLI->getBase());
692 } else if (TIL->contains(DestLoop)) {
693 // Edge from an outer loop to an inner loop. Add to the outer loop.
694 TIL->addBasicBlockToLoop(NMBB, MLI->getBase());
695 } else if (DestLoop->contains(TIL)) {
696 // Edge from an inner loop to an outer loop. Add to the outer loop.
697 DestLoop->addBasicBlockToLoop(NMBB, MLI->getBase());
699 // Edge from two loops with no containment relation. Because these
700 // are natural loops, we know that the destination block must be the
701 // header of its loop (adding a branch into a loop elsewhere would
702 // create an irreducible loop).
703 assert(DestLoop->getHeader() == Succ &&
704 "Should not create irreducible loops!");
705 if (MachineLoop *P = DestLoop->getParentLoop())
706 P->addBasicBlockToLoop(NMBB, MLI->getBase());
714 /// removeFromParent - This method unlinks 'this' from the containing function,
715 /// and returns it, but does not delete it.
716 MachineBasicBlock *MachineBasicBlock::removeFromParent() {
717 assert(getParent() && "Not embedded in a function!");
718 getParent()->remove(this);
723 /// eraseFromParent - This method unlinks 'this' from the containing function,
725 void MachineBasicBlock::eraseFromParent() {
726 assert(getParent() && "Not embedded in a function!");
727 getParent()->erase(this);
731 /// ReplaceUsesOfBlockWith - Given a machine basic block that branched to
732 /// 'Old', change the code and CFG so that it branches to 'New' instead.
733 void MachineBasicBlock::ReplaceUsesOfBlockWith(MachineBasicBlock *Old,
734 MachineBasicBlock *New) {
735 assert(Old != New && "Cannot replace self with self!");
737 MachineBasicBlock::insn_iterator I = insn_end();
738 while (I != insn_begin()) {
740 if (!I->isTerminator()) break;
742 // Scan the operands of this machine instruction, replacing any uses of Old
744 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
745 if (I->getOperand(i).isMBB() &&
746 I->getOperand(i).getMBB() == Old)
747 I->getOperand(i).setMBB(New);
750 // Update the successor information.
751 replaceSuccessor(Old, New);
754 /// CorrectExtraCFGEdges - Various pieces of code can cause excess edges in the
755 /// CFG to be inserted. If we have proven that MBB can only branch to DestA and
756 /// DestB, remove any other MBB successors from the CFG. DestA and DestB can be
759 /// Besides DestA and DestB, retain other edges leading to LandingPads
760 /// (currently there can be only one; we don't check or require that here).
761 /// Note it is possible that DestA and/or DestB are LandingPads.
762 bool MachineBasicBlock::CorrectExtraCFGEdges(MachineBasicBlock *DestA,
763 MachineBasicBlock *DestB,
765 // The values of DestA and DestB frequently come from a call to the
766 // 'TargetInstrInfo::AnalyzeBranch' method. We take our meaning of the initial
767 // values from there.
769 // 1. If both DestA and DestB are null, then the block ends with no branches
770 // (it falls through to its successor).
771 // 2. If DestA is set, DestB is null, and isCond is false, then the block ends
772 // with only an unconditional branch.
773 // 3. If DestA is set, DestB is null, and isCond is true, then the block ends
774 // with a conditional branch that falls through to a successor (DestB).
775 // 4. If DestA and DestB is set and isCond is true, then the block ends with a
776 // conditional branch followed by an unconditional branch. DestA is the
777 // 'true' destination and DestB is the 'false' destination.
779 bool Changed = false;
781 MachineFunction::iterator FallThru =
782 llvm::next(MachineFunction::iterator(this));
784 if (DestA == 0 && DestB == 0) {
785 // Block falls through to successor.
788 } else if (DestA != 0 && DestB == 0) {
790 // Block ends in conditional jump that falls through to successor.
793 assert(DestA && DestB && isCond &&
794 "CFG in a bad state. Cannot correct CFG edges");
797 // Remove superfluous edges. I.e., those which aren't destinations of this
798 // basic block, duplicate edges, or landing pads.
799 SmallPtrSet<const MachineBasicBlock*, 8> SeenMBBs;
800 MachineBasicBlock::succ_iterator SI = succ_begin();
801 while (SI != succ_end()) {
802 const MachineBasicBlock *MBB = *SI;
803 if (!SeenMBBs.insert(MBB) ||
804 (MBB != DestA && MBB != DestB && !MBB->isLandingPad())) {
805 // This is a superfluous edge, remove it.
806 SI = removeSuccessor(SI);
816 /// findDebugLoc - find the next valid DebugLoc starting at MBBI, skipping
817 /// any DBG_VALUE instructions. Return UnknownLoc if there is none.
819 MachineBasicBlock::findDebugLoc(insn_iterator MBBI) {
821 insn_iterator E = insn_end();
825 // Skip debug declarations, we don't want a DebugLoc from them.
826 while (MBBI != E && MBBI->isDebugValue())
829 DL = MBBI->getDebugLoc();
833 /// getSuccWeight - Return weight of the edge from this block to MBB.
835 uint32_t MachineBasicBlock::getSuccWeight(MachineBasicBlock *succ) {
839 succ_iterator I = std::find(Successors.begin(), Successors.end(), succ);
840 return *getWeightIterator(I);
843 /// getWeightIterator - Return wight iterator corresonding to the I successor
845 MachineBasicBlock::weight_iterator MachineBasicBlock::
846 getWeightIterator(MachineBasicBlock::succ_iterator I) {
847 assert(Weights.size() == Successors.size() && "Async weight list!");
848 size_t index = std::distance(Successors.begin(), I);
849 assert(index < Weights.size() && "Not a current successor!");
850 return Weights.begin() + index;
853 void llvm::WriteAsOperand(raw_ostream &OS, const MachineBasicBlock *MBB,
855 OS << "BB#" << MBB->getNumber();