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 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 instr_iterator I = instr_begin(), E = instr_end();
145 while (I != E && I->isPHI())
147 assert(!I->isInsideBundle() && "First non-phi MI cannot be inside a bundle!");
151 MachineBasicBlock::iterator
152 MachineBasicBlock::SkipPHIsAndLabels(MachineBasicBlock::iterator I) {
154 while (I != E && (I->isPHI() || I->isLabel() || I->isDebugValue()))
156 // FIXME: This needs to change if we wish to bundle labels / dbg_values
157 // inside the bundle.
158 assert(!I->isInsideBundle() &&
159 "First non-phi / non-label instruction is inside a bundle!");
163 MachineBasicBlock::iterator MachineBasicBlock::getFirstTerminator() {
164 iterator B = begin(), E = end(), I = E;
165 while (I != B && ((--I)->isTerminator() || I->isDebugValue()))
167 while (I != E && !I->isTerminator())
172 MachineBasicBlock::const_iterator
173 MachineBasicBlock::getFirstTerminator() const {
174 const_iterator B = begin(), E = end(), I = E;
175 while (I != B && ((--I)->isTerminator() || I->isDebugValue()))
177 while (I != E && !I->isTerminator())
182 MachineBasicBlock::instr_iterator MachineBasicBlock::getFirstInstrTerminator() {
183 instr_iterator B = instr_begin(), E = instr_end(), I = E;
184 while (I != B && ((--I)->isTerminator() || I->isDebugValue()))
186 while (I != E && !I->isTerminator())
191 MachineBasicBlock::iterator MachineBasicBlock::getLastNonDebugInstr() {
192 // Skip over end-of-block dbg_value instructions.
193 instr_iterator B = instr_begin(), I = instr_end();
196 // Return instruction that starts a bundle.
197 if (I->isDebugValue() || I->isInsideBundle())
201 // The block is all debug values.
205 MachineBasicBlock::const_iterator
206 MachineBasicBlock::getLastNonDebugInstr() const {
207 // Skip over end-of-block dbg_value instructions.
208 const_instr_iterator B = instr_begin(), I = instr_end();
211 // Return instruction that starts a bundle.
212 if (I->isDebugValue() || I->isInsideBundle())
216 // The block is all debug values.
220 const MachineBasicBlock *MachineBasicBlock::getLandingPadSuccessor() const {
221 // A block with a landing pad successor only has one other successor.
224 for (const_succ_iterator I = succ_begin(), E = succ_end(); I != E; ++I)
225 if ((*I)->isLandingPad())
230 void MachineBasicBlock::dump() const {
234 StringRef MachineBasicBlock::getName() const {
235 if (const BasicBlock *LBB = getBasicBlock())
236 return LBB->getName();
241 /// Return a hopefully unique identifier for this block.
242 std::string MachineBasicBlock::getFullName() const {
245 Name = (getParent()->getFunction()->getName() + ":").str();
247 Name += getBasicBlock()->getName();
249 Name += (Twine("BB") + Twine(getNumber())).str();
253 void MachineBasicBlock::print(raw_ostream &OS, SlotIndexes *Indexes) const {
254 const MachineFunction *MF = getParent();
256 OS << "Can't print out MachineBasicBlock because parent MachineFunction"
262 OS << Indexes->getMBBStartIdx(this) << '\t';
264 OS << "BB#" << getNumber() << ": ";
266 const char *Comma = "";
267 if (const BasicBlock *LBB = getBasicBlock()) {
268 OS << Comma << "derived from LLVM BB ";
269 WriteAsOperand(OS, LBB, /*PrintType=*/false);
272 if (isLandingPad()) { OS << Comma << "EH LANDING PAD"; Comma = ", "; }
273 if (hasAddressTaken()) { OS << Comma << "ADDRESS TAKEN"; Comma = ", "; }
275 OS << Comma << "Align " << Alignment << " (" << (1u << Alignment)
280 const TargetRegisterInfo *TRI = MF->getTarget().getRegisterInfo();
281 if (!livein_empty()) {
282 if (Indexes) OS << '\t';
284 for (livein_iterator I = livein_begin(),E = livein_end(); I != E; ++I)
285 OS << ' ' << PrintReg(*I, TRI);
288 // Print the preds of this block according to the CFG.
290 if (Indexes) OS << '\t';
291 OS << " Predecessors according to CFG:";
292 for (const_pred_iterator PI = pred_begin(), E = pred_end(); PI != E; ++PI)
293 OS << " BB#" << (*PI)->getNumber();
297 for (const_instr_iterator I = instr_begin(); I != instr_end(); ++I) {
299 if (Indexes->hasIndex(I))
300 OS << Indexes->getInstructionIndex(I);
304 if (I->isInsideBundle())
306 I->print(OS, &getParent()->getTarget());
309 // Print the successors of this block according to the CFG.
311 if (Indexes) OS << '\t';
312 OS << " Successors according to CFG:";
313 for (const_succ_iterator SI = succ_begin(), E = succ_end(); SI != E; ++SI)
314 OS << " BB#" << (*SI)->getNumber();
319 void MachineBasicBlock::removeLiveIn(unsigned Reg) {
320 std::vector<unsigned>::iterator I =
321 std::find(LiveIns.begin(), LiveIns.end(), Reg);
322 if (I != LiveIns.end())
326 bool MachineBasicBlock::isLiveIn(unsigned Reg) const {
327 livein_iterator I = std::find(livein_begin(), livein_end(), Reg);
328 return I != livein_end();
331 void MachineBasicBlock::moveBefore(MachineBasicBlock *NewAfter) {
332 getParent()->splice(NewAfter, this);
335 void MachineBasicBlock::moveAfter(MachineBasicBlock *NewBefore) {
336 MachineFunction::iterator BBI = NewBefore;
337 getParent()->splice(++BBI, this);
340 void MachineBasicBlock::updateTerminator() {
341 const TargetInstrInfo *TII = getParent()->getTarget().getInstrInfo();
342 // A block with no successors has no concerns with fall-through edges.
343 if (this->succ_empty()) return;
345 MachineBasicBlock *TBB = 0, *FBB = 0;
346 SmallVector<MachineOperand, 4> Cond;
347 DebugLoc dl; // FIXME: this is nowhere
348 bool B = TII->AnalyzeBranch(*this, TBB, FBB, Cond);
350 assert(!B && "UpdateTerminators requires analyzable predecessors!");
353 // The block has an unconditional branch. If its successor is now
354 // its layout successor, delete the branch.
355 if (isLayoutSuccessor(TBB))
356 TII->RemoveBranch(*this);
358 // The block has an unconditional fallthrough. If its successor is not
359 // its layout successor, insert a branch. First we have to locate the
360 // only non-landing-pad successor, as that is the fallthrough block.
361 for (succ_iterator SI = succ_begin(), SE = succ_end(); SI != SE; ++SI) {
362 if ((*SI)->isLandingPad())
364 assert(!TBB && "Found more than one non-landing-pad successor!");
368 // If there is no non-landing-pad successor, the block has no
369 // fall-through edges to be concerned with.
373 // Finally update the unconditional successor to be reached via a branch
374 // if it would not be reached by fallthrough.
375 if (!isLayoutSuccessor(TBB))
376 TII->InsertBranch(*this, TBB, 0, Cond, dl);
380 // The block has a non-fallthrough conditional branch. If one of its
381 // successors is its layout successor, rewrite it to a fallthrough
382 // conditional branch.
383 if (isLayoutSuccessor(TBB)) {
384 if (TII->ReverseBranchCondition(Cond))
386 TII->RemoveBranch(*this);
387 TII->InsertBranch(*this, FBB, 0, Cond, dl);
388 } else if (isLayoutSuccessor(FBB)) {
389 TII->RemoveBranch(*this);
390 TII->InsertBranch(*this, TBB, 0, Cond, dl);
393 // Walk through the successors and find the successor which is not
394 // a landing pad and is not the conditional branch destination (in TBB)
395 // as the fallthrough successor.
396 MachineBasicBlock *FallthroughBB = 0;
397 for (succ_iterator SI = succ_begin(), SE = succ_end(); SI != SE; ++SI) {
398 if ((*SI)->isLandingPad() || *SI == TBB)
400 assert(!FallthroughBB && "Found more than one fallthrough successor.");
403 if (!FallthroughBB && canFallThrough()) {
404 // We fallthrough to the same basic block as the conditional jump
405 // targets. Remove the conditional jump, leaving unconditional
407 // FIXME: This does not seem like a reasonable pattern to support, but it
408 // has been seen in the wild coming out of degenerate ARM test cases.
409 TII->RemoveBranch(*this);
411 // Finally update the unconditional successor to be reached via a branch
412 // if it would not be reached by fallthrough.
413 if (!isLayoutSuccessor(TBB))
414 TII->InsertBranch(*this, TBB, 0, Cond, dl);
418 // The block has a fallthrough conditional branch.
419 if (isLayoutSuccessor(TBB)) {
420 if (TII->ReverseBranchCondition(Cond)) {
421 // We can't reverse the condition, add an unconditional branch.
423 TII->InsertBranch(*this, FallthroughBB, 0, Cond, dl);
426 TII->RemoveBranch(*this);
427 TII->InsertBranch(*this, FallthroughBB, 0, Cond, dl);
428 } else if (!isLayoutSuccessor(FallthroughBB)) {
429 TII->RemoveBranch(*this);
430 TII->InsertBranch(*this, TBB, FallthroughBB, Cond, dl);
436 void MachineBasicBlock::addSuccessor(MachineBasicBlock *succ, uint32_t weight) {
438 // If we see non-zero value for the first time it means we actually use Weight
439 // list, so we fill all Weights with 0's.
440 if (weight != 0 && Weights.empty())
441 Weights.resize(Successors.size());
443 if (weight != 0 || !Weights.empty())
444 Weights.push_back(weight);
446 Successors.push_back(succ);
447 succ->addPredecessor(this);
450 void MachineBasicBlock::removeSuccessor(MachineBasicBlock *succ) {
451 succ->removePredecessor(this);
452 succ_iterator I = std::find(Successors.begin(), Successors.end(), succ);
453 assert(I != Successors.end() && "Not a current successor!");
455 // If Weight list is empty it means we don't use it (disabled optimization).
456 if (!Weights.empty()) {
457 weight_iterator WI = getWeightIterator(I);
464 MachineBasicBlock::succ_iterator
465 MachineBasicBlock::removeSuccessor(succ_iterator I) {
466 assert(I != Successors.end() && "Not a current successor!");
468 // If Weight list is empty it means we don't use it (disabled optimization).
469 if (!Weights.empty()) {
470 weight_iterator WI = getWeightIterator(I);
474 (*I)->removePredecessor(this);
475 return Successors.erase(I);
478 void MachineBasicBlock::replaceSuccessor(MachineBasicBlock *Old,
479 MachineBasicBlock *New) {
481 succ_iterator SI = std::find(Successors.begin(), Successors.end(), Old);
483 // If Weight list is empty it means we don't use it (disabled optimization).
484 if (!Weights.empty()) {
485 weight_iterator WI = getWeightIterator(SI);
489 // Update the successor information.
491 addSuccessor(New, weight);
494 void MachineBasicBlock::addPredecessor(MachineBasicBlock *pred) {
495 Predecessors.push_back(pred);
498 void MachineBasicBlock::removePredecessor(MachineBasicBlock *pred) {
499 pred_iterator I = std::find(Predecessors.begin(), Predecessors.end(), pred);
500 assert(I != Predecessors.end() && "Pred is not a predecessor of this block!");
501 Predecessors.erase(I);
504 void MachineBasicBlock::transferSuccessors(MachineBasicBlock *fromMBB) {
508 while (!fromMBB->succ_empty()) {
509 MachineBasicBlock *Succ = *fromMBB->succ_begin();
513 // If Weight list is empty it means we don't use it (disabled optimization).
514 if (!fromMBB->Weights.empty())
515 weight = *fromMBB->Weights.begin();
517 addSuccessor(Succ, weight);
518 fromMBB->removeSuccessor(Succ);
523 MachineBasicBlock::transferSuccessorsAndUpdatePHIs(MachineBasicBlock *fromMBB) {
527 while (!fromMBB->succ_empty()) {
528 MachineBasicBlock *Succ = *fromMBB->succ_begin();
530 fromMBB->removeSuccessor(Succ);
532 // Fix up any PHI nodes in the successor.
533 for (MachineBasicBlock::instr_iterator MI = Succ->instr_begin(),
534 ME = Succ->instr_end(); MI != ME && MI->isPHI(); ++MI)
535 for (unsigned i = 2, e = MI->getNumOperands()+1; i != e; i += 2) {
536 MachineOperand &MO = MI->getOperand(i);
537 if (MO.getMBB() == fromMBB)
543 bool MachineBasicBlock::isSuccessor(const MachineBasicBlock *MBB) const {
544 const_succ_iterator I = std::find(Successors.begin(), Successors.end(), MBB);
545 return I != Successors.end();
548 bool MachineBasicBlock::isLayoutSuccessor(const MachineBasicBlock *MBB) const {
549 MachineFunction::const_iterator I(this);
550 return llvm::next(I) == MachineFunction::const_iterator(MBB);
553 bool MachineBasicBlock::canFallThrough() {
554 MachineFunction::iterator Fallthrough = this;
556 // If FallthroughBlock is off the end of the function, it can't fall through.
557 if (Fallthrough == getParent()->end())
560 // If FallthroughBlock isn't a successor, no fallthrough is possible.
561 if (!isSuccessor(Fallthrough))
564 // Analyze the branches, if any, at the end of the block.
565 MachineBasicBlock *TBB = 0, *FBB = 0;
566 SmallVector<MachineOperand, 4> Cond;
567 const TargetInstrInfo *TII = getParent()->getTarget().getInstrInfo();
568 if (TII->AnalyzeBranch(*this, TBB, FBB, Cond)) {
569 // If we couldn't analyze the branch, examine the last instruction.
570 // If the block doesn't end in a known control barrier, assume fallthrough
571 // is possible. The isPredicated check is needed because this code can be
572 // called during IfConversion, where an instruction which is normally a
573 // Barrier is predicated and thus no longer an actual control barrier.
574 return empty() || !back().isBarrier() || TII->isPredicated(&back());
577 // If there is no branch, control always falls through.
578 if (TBB == 0) return true;
580 // If there is some explicit branch to the fallthrough block, it can obviously
581 // reach, even though the branch should get folded to fall through implicitly.
582 if (MachineFunction::iterator(TBB) == Fallthrough ||
583 MachineFunction::iterator(FBB) == Fallthrough)
586 // If it's an unconditional branch to some block not the fall through, it
587 // doesn't fall through.
588 if (Cond.empty()) return false;
590 // Otherwise, if it is conditional and has no explicit false block, it falls
596 MachineBasicBlock::SplitCriticalEdge(MachineBasicBlock *Succ, Pass *P) {
597 // Splitting the critical edge to a landing pad block is non-trivial. Don't do
598 // it in this generic function.
599 if (Succ->isLandingPad())
602 MachineFunction *MF = getParent();
603 DebugLoc dl; // FIXME: this is nowhere
605 // We may need to update this's terminator, but we can't do that if
606 // AnalyzeBranch fails. If this uses a jump table, we won't touch it.
607 const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
608 MachineBasicBlock *TBB = 0, *FBB = 0;
609 SmallVector<MachineOperand, 4> Cond;
610 if (TII->AnalyzeBranch(*this, TBB, FBB, Cond))
613 // Avoid bugpoint weirdness: A block may end with a conditional branch but
614 // jumps to the same MBB is either case. We have duplicate CFG edges in that
615 // case that we can't handle. Since this never happens in properly optimized
616 // code, just skip those edges.
617 if (TBB && TBB == FBB) {
618 DEBUG(dbgs() << "Won't split critical edge after degenerate BB#"
619 << getNumber() << '\n');
623 MachineBasicBlock *NMBB = MF->CreateMachineBasicBlock();
624 MF->insert(llvm::next(MachineFunction::iterator(this)), NMBB);
625 DEBUG(dbgs() << "Splitting critical edge:"
626 " BB#" << getNumber()
627 << " -- BB#" << NMBB->getNumber()
628 << " -- BB#" << Succ->getNumber() << '\n');
630 // On some targets like Mips, branches may kill virtual registers. Make sure
631 // that LiveVariables is properly updated after updateTerminator replaces the
633 LiveVariables *LV = P->getAnalysisIfAvailable<LiveVariables>();
635 // Collect a list of virtual registers killed by the terminators.
636 SmallVector<unsigned, 4> KilledRegs;
638 for (instr_iterator I = getFirstInstrTerminator(), E = instr_end();
640 MachineInstr *MI = I;
641 for (MachineInstr::mop_iterator OI = MI->operands_begin(),
642 OE = MI->operands_end(); OI != OE; ++OI) {
643 if (!OI->isReg() || OI->getReg() == 0 ||
644 !OI->isUse() || !OI->isKill() || OI->isUndef())
646 unsigned Reg = OI->getReg();
647 if (TargetRegisterInfo::isPhysicalRegister(Reg) ||
648 LV->getVarInfo(Reg).removeKill(MI)) {
649 KilledRegs.push_back(Reg);
650 DEBUG(dbgs() << "Removing terminator kill: " << *MI);
651 OI->setIsKill(false);
656 ReplaceUsesOfBlockWith(Succ, NMBB);
659 // Insert unconditional "jump Succ" instruction in NMBB if necessary.
660 NMBB->addSuccessor(Succ);
661 if (!NMBB->isLayoutSuccessor(Succ)) {
663 MF->getTarget().getInstrInfo()->InsertBranch(*NMBB, Succ, NULL, Cond, dl);
666 // Fix PHI nodes in Succ so they refer to NMBB instead of this
667 for (MachineBasicBlock::instr_iterator
668 i = Succ->instr_begin(),e = Succ->instr_end();
669 i != e && i->isPHI(); ++i)
670 for (unsigned ni = 1, ne = i->getNumOperands(); ni != ne; ni += 2)
671 if (i->getOperand(ni+1).getMBB() == this)
672 i->getOperand(ni+1).setMBB(NMBB);
674 // Inherit live-ins from the successor
675 for (MachineBasicBlock::livein_iterator I = Succ->livein_begin(),
676 E = Succ->livein_end(); I != E; ++I)
679 // Update LiveVariables.
680 const TargetRegisterInfo *TRI = MF->getTarget().getRegisterInfo();
682 // Restore kills of virtual registers that were killed by the terminators.
683 while (!KilledRegs.empty()) {
684 unsigned Reg = KilledRegs.pop_back_val();
685 for (instr_iterator I = instr_end(), E = instr_begin(); I != E;) {
686 if (!(--I)->addRegisterKilled(Reg, TRI, /* addIfNotFound= */ false))
688 if (TargetRegisterInfo::isVirtualRegister(Reg))
689 LV->getVarInfo(Reg).Kills.push_back(I);
690 DEBUG(dbgs() << "Restored terminator kill: " << *I);
694 // Update relevant live-through information.
695 LV->addNewBlock(NMBB, this, Succ);
698 if (MachineDominatorTree *MDT =
699 P->getAnalysisIfAvailable<MachineDominatorTree>()) {
700 // Update dominator information.
701 MachineDomTreeNode *SucccDTNode = MDT->getNode(Succ);
703 bool IsNewIDom = true;
704 for (const_pred_iterator PI = Succ->pred_begin(), E = Succ->pred_end();
706 MachineBasicBlock *PredBB = *PI;
709 if (!MDT->dominates(SucccDTNode, MDT->getNode(PredBB))) {
715 // We know "this" dominates the newly created basic block.
716 MachineDomTreeNode *NewDTNode = MDT->addNewBlock(NMBB, this);
718 // If all the other predecessors of "Succ" are dominated by "Succ" itself
719 // then the new block is the new immediate dominator of "Succ". Otherwise,
720 // the new block doesn't dominate anything.
722 MDT->changeImmediateDominator(SucccDTNode, NewDTNode);
725 if (MachineLoopInfo *MLI = P->getAnalysisIfAvailable<MachineLoopInfo>())
726 if (MachineLoop *TIL = MLI->getLoopFor(this)) {
727 // If one or the other blocks were not in a loop, the new block is not
728 // either, and thus LI doesn't need to be updated.
729 if (MachineLoop *DestLoop = MLI->getLoopFor(Succ)) {
730 if (TIL == DestLoop) {
731 // Both in the same loop, the NMBB joins loop.
732 DestLoop->addBasicBlockToLoop(NMBB, MLI->getBase());
733 } else if (TIL->contains(DestLoop)) {
734 // Edge from an outer loop to an inner loop. Add to the outer loop.
735 TIL->addBasicBlockToLoop(NMBB, MLI->getBase());
736 } else if (DestLoop->contains(TIL)) {
737 // Edge from an inner loop to an outer loop. Add to the outer loop.
738 DestLoop->addBasicBlockToLoop(NMBB, MLI->getBase());
740 // Edge from two loops with no containment relation. Because these
741 // are natural loops, we know that the destination block must be the
742 // header of its loop (adding a branch into a loop elsewhere would
743 // create an irreducible loop).
744 assert(DestLoop->getHeader() == Succ &&
745 "Should not create irreducible loops!");
746 if (MachineLoop *P = DestLoop->getParentLoop())
747 P->addBasicBlockToLoop(NMBB, MLI->getBase());
755 MachineBasicBlock::iterator
756 MachineBasicBlock::erase(MachineBasicBlock::iterator I) {
758 MachineBasicBlock::iterator E = llvm::next(I);
759 return Insts.erase(I.getInstrIterator(), E.getInstrIterator());
762 return Insts.erase(I.getInstrIterator());
765 MachineInstr *MachineBasicBlock::remove(MachineInstr *I) {
767 instr_iterator MII = llvm::next(I);
769 while (MII != E && MII->isInsideBundle()) {
770 MachineInstr *MI = &*MII++;
775 return Insts.remove(I);
778 void MachineBasicBlock::splice(MachineBasicBlock::iterator where,
779 MachineBasicBlock *Other,
780 MachineBasicBlock::iterator From) {
781 if (From->isBundle()) {
782 MachineBasicBlock::iterator To = llvm::next(From);
783 Insts.splice(where.getInstrIterator(), Other->Insts,
784 From.getInstrIterator(), To.getInstrIterator());
788 Insts.splice(where.getInstrIterator(), Other->Insts, From.getInstrIterator());
791 /// removeFromParent - This method unlinks 'this' from the containing function,
792 /// and returns it, but does not delete it.
793 MachineBasicBlock *MachineBasicBlock::removeFromParent() {
794 assert(getParent() && "Not embedded in a function!");
795 getParent()->remove(this);
800 /// eraseFromParent - This method unlinks 'this' from the containing function,
802 void MachineBasicBlock::eraseFromParent() {
803 assert(getParent() && "Not embedded in a function!");
804 getParent()->erase(this);
808 /// ReplaceUsesOfBlockWith - Given a machine basic block that branched to
809 /// 'Old', change the code and CFG so that it branches to 'New' instead.
810 void MachineBasicBlock::ReplaceUsesOfBlockWith(MachineBasicBlock *Old,
811 MachineBasicBlock *New) {
812 assert(Old != New && "Cannot replace self with self!");
814 MachineBasicBlock::instr_iterator I = instr_end();
815 while (I != instr_begin()) {
817 if (!I->isTerminator()) break;
819 // Scan the operands of this machine instruction, replacing any uses of Old
821 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
822 if (I->getOperand(i).isMBB() &&
823 I->getOperand(i).getMBB() == Old)
824 I->getOperand(i).setMBB(New);
827 // Update the successor information.
828 replaceSuccessor(Old, New);
831 /// CorrectExtraCFGEdges - Various pieces of code can cause excess edges in the
832 /// CFG to be inserted. If we have proven that MBB can only branch to DestA and
833 /// DestB, remove any other MBB successors from the CFG. DestA and DestB can be
836 /// Besides DestA and DestB, retain other edges leading to LandingPads
837 /// (currently there can be only one; we don't check or require that here).
838 /// Note it is possible that DestA and/or DestB are LandingPads.
839 bool MachineBasicBlock::CorrectExtraCFGEdges(MachineBasicBlock *DestA,
840 MachineBasicBlock *DestB,
842 // The values of DestA and DestB frequently come from a call to the
843 // 'TargetInstrInfo::AnalyzeBranch' method. We take our meaning of the initial
844 // values from there.
846 // 1. If both DestA and DestB are null, then the block ends with no branches
847 // (it falls through to its successor).
848 // 2. If DestA is set, DestB is null, and isCond is false, then the block ends
849 // with only an unconditional branch.
850 // 3. If DestA is set, DestB is null, and isCond is true, then the block ends
851 // with a conditional branch that falls through to a successor (DestB).
852 // 4. If DestA and DestB is set and isCond is true, then the block ends with a
853 // conditional branch followed by an unconditional branch. DestA is the
854 // 'true' destination and DestB is the 'false' destination.
856 bool Changed = false;
858 MachineFunction::iterator FallThru =
859 llvm::next(MachineFunction::iterator(this));
861 if (DestA == 0 && DestB == 0) {
862 // Block falls through to successor.
865 } else if (DestA != 0 && DestB == 0) {
867 // Block ends in conditional jump that falls through to successor.
870 assert(DestA && DestB && isCond &&
871 "CFG in a bad state. Cannot correct CFG edges");
874 // Remove superfluous edges. I.e., those which aren't destinations of this
875 // basic block, duplicate edges, or landing pads.
876 SmallPtrSet<const MachineBasicBlock*, 8> SeenMBBs;
877 MachineBasicBlock::succ_iterator SI = succ_begin();
878 while (SI != succ_end()) {
879 const MachineBasicBlock *MBB = *SI;
880 if (!SeenMBBs.insert(MBB) ||
881 (MBB != DestA && MBB != DestB && !MBB->isLandingPad())) {
882 // This is a superfluous edge, remove it.
883 SI = removeSuccessor(SI);
893 /// findDebugLoc - find the next valid DebugLoc starting at MBBI, skipping
894 /// any DBG_VALUE instructions. Return UnknownLoc if there is none.
896 MachineBasicBlock::findDebugLoc(instr_iterator MBBI) {
898 instr_iterator E = instr_end();
902 // Skip debug declarations, we don't want a DebugLoc from them.
903 while (MBBI != E && MBBI->isDebugValue())
906 DL = MBBI->getDebugLoc();
910 /// getSuccWeight - Return weight of the edge from this block to MBB.
912 uint32_t MachineBasicBlock::getSuccWeight(const MachineBasicBlock *succ) const {
916 const_succ_iterator I = std::find(Successors.begin(), Successors.end(), succ);
917 return *getWeightIterator(I);
920 /// getWeightIterator - Return wight iterator corresonding to the I successor
922 MachineBasicBlock::weight_iterator MachineBasicBlock::
923 getWeightIterator(MachineBasicBlock::succ_iterator I) {
924 assert(Weights.size() == Successors.size() && "Async weight list!");
925 size_t index = std::distance(Successors.begin(), I);
926 assert(index < Weights.size() && "Not a current successor!");
927 return Weights.begin() + index;
930 /// getWeightIterator - Return wight iterator corresonding to the I successor
932 MachineBasicBlock::const_weight_iterator MachineBasicBlock::
933 getWeightIterator(MachineBasicBlock::const_succ_iterator I) const {
934 assert(Weights.size() == Successors.size() && "Async weight list!");
935 const size_t index = std::distance(Successors.begin(), I);
936 assert(index < Weights.size() && "Not a current successor!");
937 return Weights.begin() + index;
940 void llvm::WriteAsOperand(raw_ostream &OS, const MachineBasicBlock *MBB,
942 OS << "BB#" << MBB->getNumber();