1 //===- LoopInfo.cpp - Natural Loop Calculator -----------------------------===//
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 // This file defines the LoopInfo class that is used to identify natural loops
11 // and determine the loop depth of various nodes of the CFG. Note that the
12 // loops identified may actually be several natural loops that share the same
13 // header node... not just a single natural loop.
15 //===----------------------------------------------------------------------===//
17 #include "llvm/Analysis/LoopInfo.h"
18 #include "llvm/ADT/DepthFirstIterator.h"
19 #include "llvm/ADT/SmallPtrSet.h"
20 #include "llvm/Analysis/LoopInfoImpl.h"
21 #include "llvm/Analysis/LoopIterator.h"
22 #include "llvm/Analysis/ValueTracking.h"
23 #include "llvm/IR/CFG.h"
24 #include "llvm/IR/Constants.h"
25 #include "llvm/IR/Dominators.h"
26 #include "llvm/IR/Instructions.h"
27 #include "llvm/IR/LLVMContext.h"
28 #include "llvm/IR/Metadata.h"
29 #include "llvm/IR/PassManager.h"
30 #include "llvm/Support/CommandLine.h"
31 #include "llvm/Support/Debug.h"
32 #include "llvm/Support/raw_ostream.h"
36 // Explicitly instantiate methods in LoopInfoImpl.h for IR-level Loops.
37 template class llvm::LoopBase<BasicBlock, Loop>;
38 template class llvm::LoopInfoBase<BasicBlock, Loop>;
40 // Always verify loopinfo if expensive checking is enabled.
42 static bool VerifyLoopInfo = true;
44 static bool VerifyLoopInfo = false;
46 static cl::opt<bool,true>
47 VerifyLoopInfoX("verify-loop-info", cl::location(VerifyLoopInfo),
48 cl::desc("Verify loop info (time consuming)"));
50 // Loop identifier metadata name.
51 static const char *const LoopMDName = "llvm.loop";
53 //===----------------------------------------------------------------------===//
54 // Loop implementation
57 /// isLoopInvariant - Return true if the specified value is loop invariant
59 bool Loop::isLoopInvariant(const Value *V) const {
60 if (const Instruction *I = dyn_cast<Instruction>(V))
62 return true; // All non-instructions are loop invariant
65 /// hasLoopInvariantOperands - Return true if all the operands of the
66 /// specified instruction are loop invariant.
67 bool Loop::hasLoopInvariantOperands(const Instruction *I) const {
68 return all_of(I->operands(), [this](Value *V) { return isLoopInvariant(V); });
71 /// makeLoopInvariant - If the given value is an instruciton inside of the
72 /// loop and it can be hoisted, do so to make it trivially loop-invariant.
73 /// Return true if the value after any hoisting is loop invariant. This
74 /// function can be used as a slightly more aggressive replacement for
77 /// If InsertPt is specified, it is the point to hoist instructions to.
78 /// If null, the terminator of the loop preheader is used.
80 bool Loop::makeLoopInvariant(Value *V, bool &Changed,
81 Instruction *InsertPt) const {
82 if (Instruction *I = dyn_cast<Instruction>(V))
83 return makeLoopInvariant(I, Changed, InsertPt);
84 return true; // All non-instructions are loop-invariant.
87 /// makeLoopInvariant - If the given instruction is inside of the
88 /// loop and it can be hoisted, do so to make it trivially loop-invariant.
89 /// Return true if the instruction after any hoisting is loop invariant. This
90 /// function can be used as a slightly more aggressive replacement for
93 /// If InsertPt is specified, it is the point to hoist instructions to.
94 /// If null, the terminator of the loop preheader is used.
96 bool Loop::makeLoopInvariant(Instruction *I, bool &Changed,
97 Instruction *InsertPt) const {
98 // Test if the value is already loop-invariant.
99 if (isLoopInvariant(I))
101 if (!isSafeToSpeculativelyExecute(I))
103 if (I->mayReadFromMemory())
105 // EH block instructions are immobile.
108 // Determine the insertion point, unless one was given.
110 BasicBlock *Preheader = getLoopPreheader();
111 // Without a preheader, hoisting is not feasible.
114 InsertPt = Preheader->getTerminator();
116 // Don't hoist instructions with loop-variant operands.
117 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
118 if (!makeLoopInvariant(I->getOperand(i), Changed, InsertPt))
122 I->moveBefore(InsertPt);
124 // There is possibility of hoisting this instruction above some arbitrary
125 // condition. Any metadata defined on it can be control dependent on this
126 // condition. Conservatively strip it here so that we don't give any wrong
127 // information to the optimizer.
128 I->dropUnknownNonDebugMetadata();
134 /// getCanonicalInductionVariable - Check to see if the loop has a canonical
135 /// induction variable: an integer recurrence that starts at 0 and increments
136 /// by one each time through the loop. If so, return the phi node that
137 /// corresponds to it.
139 /// The IndVarSimplify pass transforms loops to have a canonical induction
142 PHINode *Loop::getCanonicalInductionVariable() const {
143 BasicBlock *H = getHeader();
145 BasicBlock *Incoming = nullptr, *Backedge = nullptr;
146 pred_iterator PI = pred_begin(H);
147 assert(PI != pred_end(H) &&
148 "Loop must have at least one backedge!");
150 if (PI == pred_end(H)) return nullptr; // dead loop
152 if (PI != pred_end(H)) return nullptr; // multiple backedges?
154 if (contains(Incoming)) {
155 if (contains(Backedge))
157 std::swap(Incoming, Backedge);
158 } else if (!contains(Backedge))
161 // Loop over all of the PHI nodes, looking for a canonical indvar.
162 for (BasicBlock::iterator I = H->begin(); isa<PHINode>(I); ++I) {
163 PHINode *PN = cast<PHINode>(I);
164 if (ConstantInt *CI =
165 dyn_cast<ConstantInt>(PN->getIncomingValueForBlock(Incoming)))
166 if (CI->isNullValue())
167 if (Instruction *Inc =
168 dyn_cast<Instruction>(PN->getIncomingValueForBlock(Backedge)))
169 if (Inc->getOpcode() == Instruction::Add &&
170 Inc->getOperand(0) == PN)
171 if (ConstantInt *CI = dyn_cast<ConstantInt>(Inc->getOperand(1)))
172 if (CI->equalsInt(1))
178 /// isLCSSAForm - Return true if the Loop is in LCSSA form
179 bool Loop::isLCSSAForm(DominatorTree &DT) const {
180 for (block_iterator BI = block_begin(), E = block_end(); BI != E; ++BI) {
181 BasicBlock *BB = *BI;
182 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E;++I)
183 for (Use &U : I->uses()) {
184 Instruction *UI = cast<Instruction>(U.getUser());
185 BasicBlock *UserBB = UI->getParent();
186 if (PHINode *P = dyn_cast<PHINode>(UI))
187 UserBB = P->getIncomingBlock(U);
189 // Check the current block, as a fast-path, before checking whether
190 // the use is anywhere in the loop. Most values are used in the same
191 // block they are defined in. Also, blocks not reachable from the
192 // entry are special; uses in them don't need to go through PHIs.
195 DT.isReachableFromEntry(UserBB))
203 bool Loop::isRecursivelyLCSSAForm(DominatorTree &DT) const {
204 if (!isLCSSAForm(DT))
207 return std::all_of(begin(), end(), [&](const Loop *L) {
208 return L->isRecursivelyLCSSAForm(DT);
212 /// isLoopSimplifyForm - Return true if the Loop is in the form that
213 /// the LoopSimplify form transforms loops to, which is sometimes called
215 bool Loop::isLoopSimplifyForm() const {
216 // Normal-form loops have a preheader, a single backedge, and all of their
217 // exits have all their predecessors inside the loop.
218 return getLoopPreheader() && getLoopLatch() && hasDedicatedExits();
221 /// isSafeToClone - Return true if the loop body is safe to clone in practice.
222 /// Routines that reform the loop CFG and split edges often fail on indirectbr.
223 bool Loop::isSafeToClone() const {
224 // Return false if any loop blocks contain indirectbrs, or there are any calls
225 // to noduplicate functions.
226 for (Loop::block_iterator I = block_begin(), E = block_end(); I != E; ++I) {
227 if (isa<IndirectBrInst>((*I)->getTerminator()))
230 if (const InvokeInst *II = dyn_cast<InvokeInst>((*I)->getTerminator())) {
231 if (II->cannotDuplicate())
233 // Return false if any loop blocks contain invokes to EH-pads other than
234 // landingpads; we don't know how to split those edges yet.
235 auto *FirstNonPHI = II->getUnwindDest()->getFirstNonPHI();
236 if (FirstNonPHI->isEHPad() && !isa<LandingPadInst>(FirstNonPHI))
240 for (BasicBlock::iterator BI = (*I)->begin(), BE = (*I)->end(); BI != BE; ++BI) {
241 if (const CallInst *CI = dyn_cast<CallInst>(BI)) {
242 if (CI->cannotDuplicate())
245 if (BI->getType()->isTokenTy() && BI->isUsedOutsideOfBlock(*I))
252 MDNode *Loop::getLoopID() const {
253 MDNode *LoopID = nullptr;
254 if (isLoopSimplifyForm()) {
255 LoopID = getLoopLatch()->getTerminator()->getMetadata(LoopMDName);
257 // Go through each predecessor of the loop header and check the
258 // terminator for the metadata.
259 BasicBlock *H = getHeader();
260 for (block_iterator I = block_begin(), IE = block_end(); I != IE; ++I) {
261 TerminatorInst *TI = (*I)->getTerminator();
262 MDNode *MD = nullptr;
264 // Check if this terminator branches to the loop header.
265 for (unsigned i = 0, ie = TI->getNumSuccessors(); i != ie; ++i) {
266 if (TI->getSuccessor(i) == H) {
267 MD = TI->getMetadata(LoopMDName);
276 else if (MD != LoopID)
280 if (!LoopID || LoopID->getNumOperands() == 0 ||
281 LoopID->getOperand(0) != LoopID)
286 void Loop::setLoopID(MDNode *LoopID) const {
287 assert(LoopID && "Loop ID should not be null");
288 assert(LoopID->getNumOperands() > 0 && "Loop ID needs at least one operand");
289 assert(LoopID->getOperand(0) == LoopID && "Loop ID should refer to itself");
291 if (isLoopSimplifyForm()) {
292 getLoopLatch()->getTerminator()->setMetadata(LoopMDName, LoopID);
296 BasicBlock *H = getHeader();
297 for (block_iterator I = block_begin(), IE = block_end(); I != IE; ++I) {
298 TerminatorInst *TI = (*I)->getTerminator();
299 for (unsigned i = 0, ie = TI->getNumSuccessors(); i != ie; ++i) {
300 if (TI->getSuccessor(i) == H)
301 TI->setMetadata(LoopMDName, LoopID);
306 bool Loop::isAnnotatedParallel() const {
307 MDNode *desiredLoopIdMetadata = getLoopID();
309 if (!desiredLoopIdMetadata)
312 // The loop branch contains the parallel loop metadata. In order to ensure
313 // that any parallel-loop-unaware optimization pass hasn't added loop-carried
314 // dependencies (thus converted the loop back to a sequential loop), check
315 // that all the memory instructions in the loop contain parallelism metadata
316 // that point to the same unique "loop id metadata" the loop branch does.
317 for (block_iterator BB = block_begin(), BE = block_end(); BB != BE; ++BB) {
318 for (BasicBlock::iterator II = (*BB)->begin(), EE = (*BB)->end();
321 if (!II->mayReadOrWriteMemory())
324 // The memory instruction can refer to the loop identifier metadata
325 // directly or indirectly through another list metadata (in case of
326 // nested parallel loops). The loop identifier metadata refers to
327 // itself so we can check both cases with the same routine.
329 II->getMetadata(LLVMContext::MD_mem_parallel_loop_access);
334 bool loopIdMDFound = false;
335 for (unsigned i = 0, e = loopIdMD->getNumOperands(); i < e; ++i) {
336 if (loopIdMD->getOperand(i) == desiredLoopIdMetadata) {
337 loopIdMDFound = true;
350 /// hasDedicatedExits - Return true if no exit block for the loop
351 /// has a predecessor that is outside the loop.
352 bool Loop::hasDedicatedExits() const {
353 // Each predecessor of each exit block of a normal loop is contained
355 SmallVector<BasicBlock *, 4> ExitBlocks;
356 getExitBlocks(ExitBlocks);
357 for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i)
358 for (pred_iterator PI = pred_begin(ExitBlocks[i]),
359 PE = pred_end(ExitBlocks[i]); PI != PE; ++PI)
362 // All the requirements are met.
366 /// getUniqueExitBlocks - Return all unique successor blocks of this loop.
367 /// These are the blocks _outside of the current loop_ which are branched to.
368 /// This assumes that loop exits are in canonical form.
371 Loop::getUniqueExitBlocks(SmallVectorImpl<BasicBlock *> &ExitBlocks) const {
372 assert(hasDedicatedExits() &&
373 "getUniqueExitBlocks assumes the loop has canonical form exits!");
375 SmallVector<BasicBlock *, 32> switchExitBlocks;
377 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) {
379 BasicBlock *current = *BI;
380 switchExitBlocks.clear();
382 for (succ_iterator I = succ_begin(*BI), E = succ_end(*BI); I != E; ++I) {
383 // If block is inside the loop then it is not a exit block.
387 pred_iterator PI = pred_begin(*I);
388 BasicBlock *firstPred = *PI;
390 // If current basic block is this exit block's first predecessor
391 // then only insert exit block in to the output ExitBlocks vector.
392 // This ensures that same exit block is not inserted twice into
393 // ExitBlocks vector.
394 if (current != firstPred)
397 // If a terminator has more then two successors, for example SwitchInst,
398 // then it is possible that there are multiple edges from current block
399 // to one exit block.
400 if (std::distance(succ_begin(current), succ_end(current)) <= 2) {
401 ExitBlocks.push_back(*I);
405 // In case of multiple edges from current block to exit block, collect
406 // only one edge in ExitBlocks. Use switchExitBlocks to keep track of
408 if (std::find(switchExitBlocks.begin(), switchExitBlocks.end(), *I)
409 == switchExitBlocks.end()) {
410 switchExitBlocks.push_back(*I);
411 ExitBlocks.push_back(*I);
417 /// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one
418 /// block, return that block. Otherwise return null.
419 BasicBlock *Loop::getUniqueExitBlock() const {
420 SmallVector<BasicBlock *, 8> UniqueExitBlocks;
421 getUniqueExitBlocks(UniqueExitBlocks);
422 if (UniqueExitBlocks.size() == 1)
423 return UniqueExitBlocks[0];
427 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
428 void Loop::dump() const {
433 //===----------------------------------------------------------------------===//
434 // UnloopUpdater implementation
438 /// Find the new parent loop for all blocks within the "unloop" whose last
439 /// backedges has just been removed.
440 class UnloopUpdater {
446 // Map unloop's immediate subloops to their nearest reachable parents. Nested
447 // loops within these subloops will not change parents. However, an immediate
448 // subloop's new parent will be the nearest loop reachable from either its own
449 // exits *or* any of its nested loop's exits.
450 DenseMap<Loop*, Loop*> SubloopParents;
452 // Flag the presence of an irreducible backedge whose destination is a block
453 // directly contained by the original unloop.
457 UnloopUpdater(Loop *UL, LoopInfo *LInfo) :
458 Unloop(UL), LI(LInfo), DFS(UL), FoundIB(false) {}
460 void updateBlockParents();
462 void removeBlocksFromAncestors();
464 void updateSubloopParents();
467 Loop *getNearestLoop(BasicBlock *BB, Loop *BBLoop);
469 } // end anonymous namespace
471 /// updateBlockParents - Update the parent loop for all blocks that are directly
472 /// contained within the original "unloop".
473 void UnloopUpdater::updateBlockParents() {
474 if (Unloop->getNumBlocks()) {
475 // Perform a post order CFG traversal of all blocks within this loop,
476 // propagating the nearest loop from sucessors to predecessors.
477 LoopBlocksTraversal Traversal(DFS, LI);
478 for (LoopBlocksTraversal::POTIterator POI = Traversal.begin(),
479 POE = Traversal.end(); POI != POE; ++POI) {
481 Loop *L = LI->getLoopFor(*POI);
482 Loop *NL = getNearestLoop(*POI, L);
485 // For reducible loops, NL is now an ancestor of Unloop.
486 assert((NL != Unloop && (!NL || NL->contains(Unloop))) &&
487 "uninitialized successor");
488 LI->changeLoopFor(*POI, NL);
491 // Or the current block is part of a subloop, in which case its parent
493 assert((FoundIB || Unloop->contains(L)) && "uninitialized successor");
497 // Each irreducible loop within the unloop induces a round of iteration using
498 // the DFS result cached by Traversal.
499 bool Changed = FoundIB;
500 for (unsigned NIters = 0; Changed; ++NIters) {
501 assert(NIters < Unloop->getNumBlocks() && "runaway iterative algorithm");
503 // Iterate over the postorder list of blocks, propagating the nearest loop
504 // from successors to predecessors as before.
506 for (LoopBlocksDFS::POIterator POI = DFS.beginPostorder(),
507 POE = DFS.endPostorder(); POI != POE; ++POI) {
509 Loop *L = LI->getLoopFor(*POI);
510 Loop *NL = getNearestLoop(*POI, L);
512 assert(NL != Unloop && (!NL || NL->contains(Unloop)) &&
513 "uninitialized successor");
514 LI->changeLoopFor(*POI, NL);
521 /// removeBlocksFromAncestors - Remove unloop's blocks from all ancestors below
522 /// their new parents.
523 void UnloopUpdater::removeBlocksFromAncestors() {
524 // Remove all unloop's blocks (including those in nested subloops) from
525 // ancestors below the new parent loop.
526 for (Loop::block_iterator BI = Unloop->block_begin(),
527 BE = Unloop->block_end(); BI != BE; ++BI) {
528 Loop *OuterParent = LI->getLoopFor(*BI);
529 if (Unloop->contains(OuterParent)) {
530 while (OuterParent->getParentLoop() != Unloop)
531 OuterParent = OuterParent->getParentLoop();
532 OuterParent = SubloopParents[OuterParent];
534 // Remove blocks from former Ancestors except Unloop itself which will be
536 for (Loop *OldParent = Unloop->getParentLoop(); OldParent != OuterParent;
537 OldParent = OldParent->getParentLoop()) {
538 assert(OldParent && "new loop is not an ancestor of the original");
539 OldParent->removeBlockFromLoop(*BI);
544 /// updateSubloopParents - Update the parent loop for all subloops directly
545 /// nested within unloop.
546 void UnloopUpdater::updateSubloopParents() {
547 while (!Unloop->empty()) {
548 Loop *Subloop = *std::prev(Unloop->end());
549 Unloop->removeChildLoop(std::prev(Unloop->end()));
551 assert(SubloopParents.count(Subloop) && "DFS failed to visit subloop");
552 if (Loop *Parent = SubloopParents[Subloop])
553 Parent->addChildLoop(Subloop);
555 LI->addTopLevelLoop(Subloop);
559 /// getNearestLoop - Return the nearest parent loop among this block's
560 /// successors. If a successor is a subloop header, consider its parent to be
561 /// the nearest parent of the subloop's exits.
563 /// For subloop blocks, simply update SubloopParents and return NULL.
564 Loop *UnloopUpdater::getNearestLoop(BasicBlock *BB, Loop *BBLoop) {
566 // Initially for blocks directly contained by Unloop, NearLoop == Unloop and
567 // is considered uninitialized.
568 Loop *NearLoop = BBLoop;
570 Loop *Subloop = nullptr;
571 if (NearLoop != Unloop && Unloop->contains(NearLoop)) {
573 // Find the subloop ancestor that is directly contained within Unloop.
574 while (Subloop->getParentLoop() != Unloop) {
575 Subloop = Subloop->getParentLoop();
576 assert(Subloop && "subloop is not an ancestor of the original loop");
578 // Get the current nearest parent of the Subloop exits, initially Unloop.
580 SubloopParents.insert(std::make_pair(Subloop, Unloop)).first->second;
583 succ_iterator I = succ_begin(BB), E = succ_end(BB);
585 assert(!Subloop && "subloop blocks must have a successor");
586 NearLoop = nullptr; // unloop blocks may now exit the function.
588 for (; I != E; ++I) {
590 continue; // self loops are uninteresting
592 Loop *L = LI->getLoopFor(*I);
594 // This successor has not been processed. This path must lead to an
595 // irreducible backedge.
596 assert((FoundIB || !DFS.hasPostorder(*I)) && "should have seen IB");
599 if (L != Unloop && Unloop->contains(L)) {
600 // Successor is in a subloop.
602 continue; // Branching within subloops. Ignore it.
604 // BB branches from the original into a subloop header.
605 assert(L->getParentLoop() == Unloop && "cannot skip into nested loops");
607 // Get the current nearest parent of the Subloop's exits.
608 L = SubloopParents[L];
609 // L could be Unloop if the only exit was an irreducible backedge.
614 // Handle critical edges from Unloop into a sibling loop.
615 if (L && !L->contains(Unloop)) {
616 L = L->getParentLoop();
618 // Remember the nearest parent loop among successors or subloop exits.
619 if (NearLoop == Unloop || !NearLoop || NearLoop->contains(L))
623 SubloopParents[Subloop] = NearLoop;
629 LoopInfo::LoopInfo(const DominatorTreeBase<BasicBlock> &DomTree) {
633 /// updateUnloop - The last backedge has been removed from a loop--now the
634 /// "unloop". Find a new parent for the blocks contained within unloop and
635 /// update the loop tree. We don't necessarily have valid dominators at this
636 /// point, but LoopInfo is still valid except for the removal of this loop.
638 /// Note that Unloop may now be an empty loop. Calling Loop::getHeader without
639 /// checking first is illegal.
640 void LoopInfo::updateUnloop(Loop *Unloop) {
642 // First handle the special case of no parent loop to simplify the algorithm.
643 if (!Unloop->getParentLoop()) {
644 // Since BBLoop had no parent, Unloop blocks are no longer in a loop.
645 for (Loop::block_iterator I = Unloop->block_begin(),
646 E = Unloop->block_end();
649 // Don't reparent blocks in subloops.
650 if (getLoopFor(*I) != Unloop)
653 // Blocks no longer have a parent but are still referenced by Unloop until
654 // the Unloop object is deleted.
655 changeLoopFor(*I, nullptr);
658 // Remove the loop from the top-level LoopInfo object.
659 for (iterator I = begin();; ++I) {
660 assert(I != end() && "Couldn't find loop");
667 // Move all of the subloops to the top-level.
668 while (!Unloop->empty())
669 addTopLevelLoop(Unloop->removeChildLoop(std::prev(Unloop->end())));
674 // Update the parent loop for all blocks within the loop. Blocks within
675 // subloops will not change parents.
676 UnloopUpdater Updater(Unloop, this);
677 Updater.updateBlockParents();
679 // Remove blocks from former ancestor loops.
680 Updater.removeBlocksFromAncestors();
682 // Add direct subloops as children in their new parent loop.
683 Updater.updateSubloopParents();
685 // Remove unloop from its parent loop.
686 Loop *ParentLoop = Unloop->getParentLoop();
687 for (Loop::iterator I = ParentLoop->begin();; ++I) {
688 assert(I != ParentLoop->end() && "Couldn't find loop");
690 ParentLoop->removeChildLoop(I);
696 char LoopAnalysis::PassID;
698 LoopInfo LoopAnalysis::run(Function &F, AnalysisManager<Function> *AM) {
699 // FIXME: Currently we create a LoopInfo from scratch for every function.
700 // This may prove to be too wasteful due to deallocating and re-allocating
701 // memory each time for the underlying map and vector datastructures. At some
702 // point it may prove worthwhile to use a freelist and recycle LoopInfo
703 // objects. I don't want to add that kind of complexity until the scope of
704 // the problem is better understood.
706 LI.analyze(AM->getResult<DominatorTreeAnalysis>(F));
710 PreservedAnalyses LoopPrinterPass::run(Function &F,
711 AnalysisManager<Function> *AM) {
712 AM->getResult<LoopAnalysis>(F).print(OS);
713 return PreservedAnalyses::all();
716 PrintLoopPass::PrintLoopPass() : OS(dbgs()) {}
717 PrintLoopPass::PrintLoopPass(raw_ostream &OS, const std::string &Banner)
718 : OS(OS), Banner(Banner) {}
720 PreservedAnalyses PrintLoopPass::run(Loop &L) {
722 for (auto *Block : L.blocks())
726 OS << "Printing <null> block";
727 return PreservedAnalyses::all();
730 //===----------------------------------------------------------------------===//
731 // LoopInfo implementation
734 char LoopInfoWrapperPass::ID = 0;
735 INITIALIZE_PASS_BEGIN(LoopInfoWrapperPass, "loops", "Natural Loop Information",
737 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
738 INITIALIZE_PASS_END(LoopInfoWrapperPass, "loops", "Natural Loop Information",
741 bool LoopInfoWrapperPass::runOnFunction(Function &) {
743 LI.analyze(getAnalysis<DominatorTreeWrapperPass>().getDomTree());
747 void LoopInfoWrapperPass::verifyAnalysis() const {
748 // LoopInfoWrapperPass is a FunctionPass, but verifying every loop in the
749 // function each time verifyAnalysis is called is very expensive. The
750 // -verify-loop-info option can enable this. In order to perform some
751 // checking by default, LoopPass has been taught to call verifyLoop manually
752 // during loop pass sequences.
757 void LoopInfoWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
758 AU.setPreservesAll();
759 AU.addRequired<DominatorTreeWrapperPass>();
762 void LoopInfoWrapperPass::print(raw_ostream &OS, const Module *) const {
766 //===----------------------------------------------------------------------===//
767 // LoopBlocksDFS implementation
770 /// Traverse the loop blocks and store the DFS result.
771 /// Useful for clients that just want the final DFS result and don't need to
772 /// visit blocks during the initial traversal.
773 void LoopBlocksDFS::perform(LoopInfo *LI) {
774 LoopBlocksTraversal Traversal(*this, LI);
775 for (LoopBlocksTraversal::POTIterator POI = Traversal.begin(),
776 POE = Traversal.end(); POI != POE; ++POI) ;