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::iterator I = N->begin(), E = N->end(); I != E; ++I)
77 I->AddRegOperandsToUseLists(RegInfo);
79 LeakDetector::removeGarbageObject(N);
82 void ilist_traits<MachineBasicBlock>::removeNodeFromList(MachineBasicBlock *N) {
83 N->getParent()->removeFromMBBNumbering(N->Number);
85 LeakDetector::addGarbageObject(N);
89 /// addNodeToList (MI) - When we add an instruction to a basic block
90 /// list, we update its parent pointer and add its operands from reg use/def
91 /// lists if appropriate.
92 void ilist_traits<MachineInstr>::addNodeToList(MachineInstr *N) {
93 assert(N->getParent() == 0 && "machine instruction already in a basic block");
96 // Add the instruction's register operands to their corresponding
98 MachineFunction *MF = Parent->getParent();
99 N->AddRegOperandsToUseLists(MF->getRegInfo());
101 LeakDetector::removeGarbageObject(N);
104 /// removeNodeFromList (MI) - When we remove an instruction from a basic block
105 /// list, we update its parent pointer and remove its operands from reg use/def
106 /// lists if appropriate.
107 void ilist_traits<MachineInstr>::removeNodeFromList(MachineInstr *N) {
108 assert(N->getParent() != 0 && "machine instruction not in a basic block");
110 // Remove from the use/def lists.
111 N->RemoveRegOperandsFromUseLists();
115 LeakDetector::addGarbageObject(N);
118 /// transferNodesFromList (MI) - When moving a range of instructions from one
119 /// MBB list to another, we need to update the parent pointers and the use/def
121 void ilist_traits<MachineInstr>::
122 transferNodesFromList(ilist_traits<MachineInstr> &fromList,
123 MachineBasicBlock::iterator first,
124 MachineBasicBlock::iterator last) {
125 assert(Parent->getParent() == fromList.Parent->getParent() &&
126 "MachineInstr parent mismatch!");
128 // Splice within the same MBB -> no change.
129 if (Parent == fromList.Parent) return;
131 // If splicing between two blocks within the same function, just update the
133 for (; first != last; ++first)
134 first->setParent(Parent);
137 void ilist_traits<MachineInstr>::deleteNode(MachineInstr* MI) {
138 assert(!MI->getParent() && "MI is still in a block!");
139 Parent->getParent()->DeleteMachineInstr(MI);
142 MachineBasicBlock::iterator MachineBasicBlock::getFirstNonPHI() {
143 iterator I = begin();
144 while (I != end() && I->isPHI())
149 MachineBasicBlock::iterator
150 MachineBasicBlock::SkipPHIsAndLabels(MachineBasicBlock::iterator I) {
151 while (I != end() && (I->isPHI() || I->isLabel() || I->isDebugValue()))
156 MachineBasicBlock::iterator MachineBasicBlock::getFirstTerminator() {
158 while (I != begin() && ((--I)->getDesc().isTerminator() || I->isDebugValue()))
160 while (I != end() && !I->getDesc().isTerminator())
165 MachineBasicBlock::iterator MachineBasicBlock::getLastNonDebugInstr() {
166 iterator B = begin(), I = end();
169 if (I->isDebugValue())
173 // The block is all debug values.
177 const MachineBasicBlock *MachineBasicBlock::getLandingPadSuccessor() const {
178 // A block with a landing pad successor only has one other successor.
181 for (const_succ_iterator I = succ_begin(), E = succ_end(); I != E; ++I)
182 if ((*I)->isLandingPad())
187 void MachineBasicBlock::dump() const {
191 StringRef MachineBasicBlock::getName() const {
192 if (const BasicBlock *LBB = getBasicBlock())
193 return LBB->getName();
198 void MachineBasicBlock::print(raw_ostream &OS, SlotIndexes *Indexes) const {
199 const MachineFunction *MF = getParent();
201 OS << "Can't print out MachineBasicBlock because parent MachineFunction"
206 if (Alignment) { OS << "Alignment " << Alignment << "\n"; }
209 OS << Indexes->getMBBStartIdx(this) << '\t';
211 OS << "BB#" << getNumber() << ": ";
213 const char *Comma = "";
214 if (const BasicBlock *LBB = getBasicBlock()) {
215 OS << Comma << "derived from LLVM BB ";
216 WriteAsOperand(OS, LBB, /*PrintType=*/false);
219 if (isLandingPad()) { OS << Comma << "EH LANDING PAD"; Comma = ", "; }
220 if (hasAddressTaken()) { OS << Comma << "ADDRESS TAKEN"; Comma = ", "; }
223 const TargetRegisterInfo *TRI = MF->getTarget().getRegisterInfo();
224 if (!livein_empty()) {
225 if (Indexes) OS << '\t';
227 for (livein_iterator I = livein_begin(),E = livein_end(); I != E; ++I)
228 OS << ' ' << PrintReg(*I, TRI);
231 // Print the preds of this block according to the CFG.
233 if (Indexes) OS << '\t';
234 OS << " Predecessors according to CFG:";
235 for (const_pred_iterator PI = pred_begin(), E = pred_end(); PI != E; ++PI)
236 OS << " BB#" << (*PI)->getNumber();
240 for (const_iterator I = begin(); I != end(); ++I) {
242 if (Indexes->hasIndex(I))
243 OS << Indexes->getInstructionIndex(I);
247 I->print(OS, &getParent()->getTarget());
250 // Print the successors of this block according to the CFG.
252 if (Indexes) OS << '\t';
253 OS << " Successors according to CFG:";
254 for (const_succ_iterator SI = succ_begin(), E = succ_end(); SI != E; ++SI)
255 OS << " BB#" << (*SI)->getNumber();
260 void MachineBasicBlock::removeLiveIn(unsigned Reg) {
261 std::vector<unsigned>::iterator I =
262 std::find(LiveIns.begin(), LiveIns.end(), Reg);
263 assert(I != LiveIns.end() && "Not a live in!");
267 bool MachineBasicBlock::isLiveIn(unsigned Reg) const {
268 livein_iterator I = std::find(livein_begin(), livein_end(), Reg);
269 return I != livein_end();
272 void MachineBasicBlock::moveBefore(MachineBasicBlock *NewAfter) {
273 getParent()->splice(NewAfter, this);
276 void MachineBasicBlock::moveAfter(MachineBasicBlock *NewBefore) {
277 MachineFunction::iterator BBI = NewBefore;
278 getParent()->splice(++BBI, this);
281 void MachineBasicBlock::updateTerminator() {
282 const TargetInstrInfo *TII = getParent()->getTarget().getInstrInfo();
283 // A block with no successors has no concerns with fall-through edges.
284 if (this->succ_empty()) return;
286 MachineBasicBlock *TBB = 0, *FBB = 0;
287 SmallVector<MachineOperand, 4> Cond;
288 DebugLoc dl; // FIXME: this is nowhere
289 bool B = TII->AnalyzeBranch(*this, TBB, FBB, Cond);
291 assert(!B && "UpdateTerminators requires analyzable predecessors!");
294 // The block has an unconditional branch. If its successor is now
295 // its layout successor, delete the branch.
296 if (isLayoutSuccessor(TBB))
297 TII->RemoveBranch(*this);
299 // The block has an unconditional fallthrough. If its successor is not
300 // its layout successor, insert a branch. First we have to locate the
301 // only non-landing-pad successor, as that is the fallthrough block.
302 for (succ_iterator SI = succ_begin(), SE = succ_end(); SI != SE; ++SI) {
303 if ((*SI)->isLandingPad())
305 assert(!TBB && "Found more than one non-landing-pad successor!");
308 if (!isLayoutSuccessor(TBB))
309 TII->InsertBranch(*this, TBB, 0, Cond, dl);
313 // The block has a non-fallthrough conditional branch. If one of its
314 // successors is its layout successor, rewrite it to a fallthrough
315 // conditional branch.
316 if (isLayoutSuccessor(TBB)) {
317 if (TII->ReverseBranchCondition(Cond))
319 TII->RemoveBranch(*this);
320 TII->InsertBranch(*this, FBB, 0, Cond, dl);
321 } else if (isLayoutSuccessor(FBB)) {
322 TII->RemoveBranch(*this);
323 TII->InsertBranch(*this, TBB, 0, Cond, dl);
326 // The block has a fallthrough conditional branch.
327 MachineBasicBlock *MBBA = *succ_begin();
328 MachineBasicBlock *MBBB = *llvm::next(succ_begin());
329 if (MBBA == TBB) std::swap(MBBB, MBBA);
330 if (isLayoutSuccessor(TBB)) {
331 if (TII->ReverseBranchCondition(Cond)) {
332 // We can't reverse the condition, add an unconditional branch.
334 TII->InsertBranch(*this, MBBA, 0, Cond, dl);
337 TII->RemoveBranch(*this);
338 TII->InsertBranch(*this, MBBA, 0, Cond, dl);
339 } else if (!isLayoutSuccessor(MBBA)) {
340 TII->RemoveBranch(*this);
341 TII->InsertBranch(*this, TBB, MBBA, Cond, dl);
347 void MachineBasicBlock::addSuccessor(MachineBasicBlock *succ, uint32_t weight) {
349 // If we see non-zero value for the first time it means we actually use Weight
350 // list, so we fill all Weights with 0's.
351 if (weight != 0 && Weights.empty())
352 Weights.resize(Successors.size());
354 if (weight != 0 || !Weights.empty())
355 Weights.push_back(weight);
357 Successors.push_back(succ);
358 succ->addPredecessor(this);
361 void MachineBasicBlock::removeSuccessor(MachineBasicBlock *succ) {
362 succ->removePredecessor(this);
363 succ_iterator I = std::find(Successors.begin(), Successors.end(), succ);
364 assert(I != Successors.end() && "Not a current successor!");
366 // If Weight list is empty it means we don't use it (disabled optimization).
367 if (!Weights.empty()) {
368 weight_iterator WI = getWeightIterator(I);
375 MachineBasicBlock::succ_iterator
376 MachineBasicBlock::removeSuccessor(succ_iterator I) {
377 assert(I != Successors.end() && "Not a current successor!");
379 // If Weight list is empty it means we don't use it (disabled optimization).
380 if (!Weights.empty()) {
381 weight_iterator WI = getWeightIterator(I);
385 (*I)->removePredecessor(this);
386 return Successors.erase(I);
389 void MachineBasicBlock::replaceSuccessor(MachineBasicBlock *Old,
390 MachineBasicBlock *New) {
392 succ_iterator SI = std::find(Successors.begin(), Successors.end(), Old);
394 // If Weight list is empty it means we don't use it (disabled optimization).
395 if (!Weights.empty()) {
396 weight_iterator WI = getWeightIterator(SI);
400 // Update the successor information.
402 addSuccessor(New, weight);
405 void MachineBasicBlock::addPredecessor(MachineBasicBlock *pred) {
406 Predecessors.push_back(pred);
409 void MachineBasicBlock::removePredecessor(MachineBasicBlock *pred) {
410 pred_iterator I = std::find(Predecessors.begin(), Predecessors.end(), pred);
411 assert(I != Predecessors.end() && "Pred is not a predecessor of this block!");
412 Predecessors.erase(I);
415 void MachineBasicBlock::transferSuccessors(MachineBasicBlock *fromMBB) {
419 while (!fromMBB->succ_empty()) {
420 MachineBasicBlock *Succ = *fromMBB->succ_begin();
424 // If Weight list is empty it means we don't use it (disabled optimization).
425 if (!fromMBB->Weights.empty())
426 weight = *fromMBB->Weights.begin();
428 addSuccessor(Succ, weight);
429 fromMBB->removeSuccessor(Succ);
434 MachineBasicBlock::transferSuccessorsAndUpdatePHIs(MachineBasicBlock *fromMBB) {
438 while (!fromMBB->succ_empty()) {
439 MachineBasicBlock *Succ = *fromMBB->succ_begin();
441 fromMBB->removeSuccessor(Succ);
443 // Fix up any PHI nodes in the successor.
444 for (MachineBasicBlock::iterator MI = Succ->begin(), ME = Succ->end();
445 MI != ME && MI->isPHI(); ++MI)
446 for (unsigned i = 2, e = MI->getNumOperands()+1; i != e; i += 2) {
447 MachineOperand &MO = MI->getOperand(i);
448 if (MO.getMBB() == fromMBB)
454 bool MachineBasicBlock::isSuccessor(const MachineBasicBlock *MBB) const {
455 const_succ_iterator I = std::find(Successors.begin(), Successors.end(), MBB);
456 return I != Successors.end();
459 bool MachineBasicBlock::isLayoutSuccessor(const MachineBasicBlock *MBB) const {
460 MachineFunction::const_iterator I(this);
461 return llvm::next(I) == MachineFunction::const_iterator(MBB);
464 bool MachineBasicBlock::canFallThrough() {
465 MachineFunction::iterator Fallthrough = this;
467 // If FallthroughBlock is off the end of the function, it can't fall through.
468 if (Fallthrough == getParent()->end())
471 // If FallthroughBlock isn't a successor, no fallthrough is possible.
472 if (!isSuccessor(Fallthrough))
475 // Analyze the branches, if any, at the end of the block.
476 MachineBasicBlock *TBB = 0, *FBB = 0;
477 SmallVector<MachineOperand, 4> Cond;
478 const TargetInstrInfo *TII = getParent()->getTarget().getInstrInfo();
479 if (TII->AnalyzeBranch(*this, TBB, FBB, Cond)) {
480 // If we couldn't analyze the branch, examine the last instruction.
481 // If the block doesn't end in a known control barrier, assume fallthrough
482 // is possible. The isPredicable check is needed because this code can be
483 // called during IfConversion, where an instruction which is normally a
484 // Barrier is predicated and thus no longer an actual control barrier. This
485 // is over-conservative though, because if an instruction isn't actually
486 // predicated we could still treat it like a barrier.
487 return empty() || !back().getDesc().isBarrier() ||
488 back().getDesc().isPredicable();
491 // If there is no branch, control always falls through.
492 if (TBB == 0) return true;
494 // If there is some explicit branch to the fallthrough block, it can obviously
495 // reach, even though the branch should get folded to fall through implicitly.
496 if (MachineFunction::iterator(TBB) == Fallthrough ||
497 MachineFunction::iterator(FBB) == Fallthrough)
500 // If it's an unconditional branch to some block not the fall through, it
501 // doesn't fall through.
502 if (Cond.empty()) return false;
504 // Otherwise, if it is conditional and has no explicit false block, it falls
510 MachineBasicBlock::SplitCriticalEdge(MachineBasicBlock *Succ, Pass *P) {
511 MachineFunction *MF = getParent();
512 DebugLoc dl; // FIXME: this is nowhere
514 // We may need to update this's terminator, but we can't do that if
515 // AnalyzeBranch fails. If this uses a jump table, we won't touch it.
516 const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
517 MachineBasicBlock *TBB = 0, *FBB = 0;
518 SmallVector<MachineOperand, 4> Cond;
519 if (TII->AnalyzeBranch(*this, TBB, FBB, Cond))
522 // Avoid bugpoint weirdness: A block may end with a conditional branch but
523 // jumps to the same MBB is either case. We have duplicate CFG edges in that
524 // case that we can't handle. Since this never happens in properly optimized
525 // code, just skip those edges.
526 if (TBB && TBB == FBB) {
527 DEBUG(dbgs() << "Won't split critical edge after degenerate BB#"
528 << getNumber() << '\n');
532 MachineBasicBlock *NMBB = MF->CreateMachineBasicBlock();
533 MF->insert(llvm::next(MachineFunction::iterator(this)), NMBB);
534 DEBUG(dbgs() << "Splitting critical edge:"
535 " BB#" << getNumber()
536 << " -- BB#" << NMBB->getNumber()
537 << " -- BB#" << Succ->getNumber() << '\n');
539 // On some targets like Mips, branches may kill virtual registers. Make sure
540 // that LiveVariables is properly updated after updateTerminator replaces the
542 LiveVariables *LV = P->getAnalysisIfAvailable<LiveVariables>();
544 // Collect a list of virtual registers killed by the terminators.
545 SmallVector<unsigned, 4> KilledRegs;
547 for (iterator I = getFirstTerminator(), E = end(); I != E; ++I) {
548 MachineInstr *MI = I;
549 for (MachineInstr::mop_iterator OI = MI->operands_begin(),
550 OE = MI->operands_end(); OI != OE; ++OI) {
551 if (!OI->isReg() || !OI->isUse() || !OI->isKill() || OI->isUndef())
553 unsigned Reg = OI->getReg();
554 if (TargetRegisterInfo::isVirtualRegister(Reg) &&
555 LV->getVarInfo(Reg).removeKill(MI)) {
556 KilledRegs.push_back(Reg);
557 DEBUG(dbgs() << "Removing terminator kill: " << *MI);
558 OI->setIsKill(false);
563 ReplaceUsesOfBlockWith(Succ, NMBB);
566 // Insert unconditional "jump Succ" instruction in NMBB if necessary.
567 NMBB->addSuccessor(Succ);
568 if (!NMBB->isLayoutSuccessor(Succ)) {
570 MF->getTarget().getInstrInfo()->InsertBranch(*NMBB, Succ, NULL, Cond, dl);
573 // Fix PHI nodes in Succ so they refer to NMBB instead of this
574 for (MachineBasicBlock::iterator i = Succ->begin(), e = Succ->end();
575 i != e && i->isPHI(); ++i)
576 for (unsigned ni = 1, ne = i->getNumOperands(); ni != ne; ni += 2)
577 if (i->getOperand(ni+1).getMBB() == this)
578 i->getOperand(ni+1).setMBB(NMBB);
580 // Inherit live-ins from the successor
581 for (MachineBasicBlock::livein_iterator I = Succ->livein_begin(),
582 E = Succ->livein_end(); I != E; ++I)
585 // Update LiveVariables.
587 // Restore kills of virtual registers that were killed by the terminators.
588 while (!KilledRegs.empty()) {
589 unsigned Reg = KilledRegs.pop_back_val();
590 for (iterator I = end(), E = begin(); I != E;) {
591 if (!(--I)->addRegisterKilled(Reg, NULL, /* addIfNotFound= */ false))
593 LV->getVarInfo(Reg).Kills.push_back(I);
594 DEBUG(dbgs() << "Restored terminator kill: " << *I);
598 // Update relevant live-through information.
599 LV->addNewBlock(NMBB, this, Succ);
602 if (MachineDominatorTree *MDT =
603 P->getAnalysisIfAvailable<MachineDominatorTree>()) {
604 // Update dominator information.
605 MachineDomTreeNode *SucccDTNode = MDT->getNode(Succ);
607 bool IsNewIDom = true;
608 for (const_pred_iterator PI = Succ->pred_begin(), E = Succ->pred_end();
610 MachineBasicBlock *PredBB = *PI;
613 if (!MDT->dominates(SucccDTNode, MDT->getNode(PredBB))) {
619 // We know "this" dominates the newly created basic block.
620 MachineDomTreeNode *NewDTNode = MDT->addNewBlock(NMBB, this);
622 // If all the other predecessors of "Succ" are dominated by "Succ" itself
623 // then the new block is the new immediate dominator of "Succ". Otherwise,
624 // the new block doesn't dominate anything.
626 MDT->changeImmediateDominator(SucccDTNode, NewDTNode);
629 if (MachineLoopInfo *MLI = P->getAnalysisIfAvailable<MachineLoopInfo>())
630 if (MachineLoop *TIL = MLI->getLoopFor(this)) {
631 // If one or the other blocks were not in a loop, the new block is not
632 // either, and thus LI doesn't need to be updated.
633 if (MachineLoop *DestLoop = MLI->getLoopFor(Succ)) {
634 if (TIL == DestLoop) {
635 // Both in the same loop, the NMBB joins loop.
636 DestLoop->addBasicBlockToLoop(NMBB, MLI->getBase());
637 } else if (TIL->contains(DestLoop)) {
638 // Edge from an outer loop to an inner loop. Add to the outer loop.
639 TIL->addBasicBlockToLoop(NMBB, MLI->getBase());
640 } else if (DestLoop->contains(TIL)) {
641 // Edge from an inner loop to an outer loop. Add to the outer loop.
642 DestLoop->addBasicBlockToLoop(NMBB, MLI->getBase());
644 // Edge from two loops with no containment relation. Because these
645 // are natural loops, we know that the destination block must be the
646 // header of its loop (adding a branch into a loop elsewhere would
647 // create an irreducible loop).
648 assert(DestLoop->getHeader() == Succ &&
649 "Should not create irreducible loops!");
650 if (MachineLoop *P = DestLoop->getParentLoop())
651 P->addBasicBlockToLoop(NMBB, MLI->getBase());
659 /// removeFromParent - This method unlinks 'this' from the containing function,
660 /// and returns it, but does not delete it.
661 MachineBasicBlock *MachineBasicBlock::removeFromParent() {
662 assert(getParent() && "Not embedded in a function!");
663 getParent()->remove(this);
668 /// eraseFromParent - This method unlinks 'this' from the containing function,
670 void MachineBasicBlock::eraseFromParent() {
671 assert(getParent() && "Not embedded in a function!");
672 getParent()->erase(this);
676 /// ReplaceUsesOfBlockWith - Given a machine basic block that branched to
677 /// 'Old', change the code and CFG so that it branches to 'New' instead.
678 void MachineBasicBlock::ReplaceUsesOfBlockWith(MachineBasicBlock *Old,
679 MachineBasicBlock *New) {
680 assert(Old != New && "Cannot replace self with self!");
682 MachineBasicBlock::iterator I = end();
683 while (I != begin()) {
685 if (!I->getDesc().isTerminator()) break;
687 // Scan the operands of this machine instruction, replacing any uses of Old
689 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
690 if (I->getOperand(i).isMBB() &&
691 I->getOperand(i).getMBB() == Old)
692 I->getOperand(i).setMBB(New);
695 // Update the successor information.
696 replaceSuccessor(Old, New);
699 /// CorrectExtraCFGEdges - Various pieces of code can cause excess edges in the
700 /// CFG to be inserted. If we have proven that MBB can only branch to DestA and
701 /// DestB, remove any other MBB successors from the CFG. DestA and DestB can be
704 /// Besides DestA and DestB, retain other edges leading to LandingPads
705 /// (currently there can be only one; we don't check or require that here).
706 /// Note it is possible that DestA and/or DestB are LandingPads.
707 bool MachineBasicBlock::CorrectExtraCFGEdges(MachineBasicBlock *DestA,
708 MachineBasicBlock *DestB,
710 // The values of DestA and DestB frequently come from a call to the
711 // 'TargetInstrInfo::AnalyzeBranch' method. We take our meaning of the initial
712 // values from there.
714 // 1. If both DestA and DestB are null, then the block ends with no branches
715 // (it falls through to its successor).
716 // 2. If DestA is set, DestB is null, and isCond is false, then the block ends
717 // with only an unconditional branch.
718 // 3. If DestA is set, DestB is null, and isCond is true, then the block ends
719 // with a conditional branch that falls through to a successor (DestB).
720 // 4. If DestA and DestB is set and isCond is true, then the block ends with a
721 // conditional branch followed by an unconditional branch. DestA is the
722 // 'true' destination and DestB is the 'false' destination.
724 bool Changed = false;
726 MachineFunction::iterator FallThru =
727 llvm::next(MachineFunction::iterator(this));
729 if (DestA == 0 && DestB == 0) {
730 // Block falls through to successor.
733 } else if (DestA != 0 && DestB == 0) {
735 // Block ends in conditional jump that falls through to successor.
738 assert(DestA && DestB && isCond &&
739 "CFG in a bad state. Cannot correct CFG edges");
742 // Remove superfluous edges. I.e., those which aren't destinations of this
743 // basic block, duplicate edges, or landing pads.
744 SmallPtrSet<const MachineBasicBlock*, 8> SeenMBBs;
745 MachineBasicBlock::succ_iterator SI = succ_begin();
746 while (SI != succ_end()) {
747 const MachineBasicBlock *MBB = *SI;
748 if (!SeenMBBs.insert(MBB) ||
749 (MBB != DestA && MBB != DestB && !MBB->isLandingPad())) {
750 // This is a superfluous edge, remove it.
751 SI = removeSuccessor(SI);
761 /// findDebugLoc - find the next valid DebugLoc starting at MBBI, skipping
762 /// any DBG_VALUE instructions. Return UnknownLoc if there is none.
764 MachineBasicBlock::findDebugLoc(MachineBasicBlock::iterator &MBBI) {
766 MachineBasicBlock::iterator E = end();
768 // Skip debug declarations, we don't want a DebugLoc from them.
769 MachineBasicBlock::iterator MBBI2 = MBBI;
770 while (MBBI2 != E && MBBI2->isDebugValue())
773 DL = MBBI2->getDebugLoc();
778 /// getSuccWeight - Return weight of the edge from this block to MBB.
780 uint32_t MachineBasicBlock::getSuccWeight(MachineBasicBlock *succ) {
784 succ_iterator I = std::find(Successors.begin(), Successors.end(), succ);
785 return *getWeightIterator(I);
788 /// getWeightIterator - Return wight iterator corresonding to the I successor
790 MachineBasicBlock::weight_iterator MachineBasicBlock::
791 getWeightIterator(MachineBasicBlock::succ_iterator I) {
792 assert(Weights.size() == Successors.size() && "Async weight list!");
793 size_t index = std::distance(Successors.begin(), I);
794 assert(index < Weights.size() && "Not a current successor!");
795 return Weights.begin() + index;
798 void llvm::WriteAsOperand(raw_ostream &OS, const MachineBasicBlock *MBB,
800 OS << "BB#" << MBB->getNumber();