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/ScopeExit.h"
20 #include "llvm/ADT/SmallPtrSet.h"
21 #include "llvm/Analysis/LoopInfoImpl.h"
22 #include "llvm/Analysis/LoopIterator.h"
23 #include "llvm/Analysis/ValueTracking.h"
24 #include "llvm/Config/llvm-config.h"
25 #include "llvm/IR/CFG.h"
26 #include "llvm/IR/Constants.h"
27 #include "llvm/IR/DebugLoc.h"
28 #include "llvm/IR/Dominators.h"
29 #include "llvm/IR/Instructions.h"
30 #include "llvm/IR/LLVMContext.h"
31 #include "llvm/IR/Metadata.h"
32 #include "llvm/IR/PassManager.h"
33 #include "llvm/Support/CommandLine.h"
34 #include "llvm/Support/Debug.h"
35 #include "llvm/Support/raw_ostream.h"
39 // Explicitly instantiate methods in LoopInfoImpl.h for IR-level Loops.
40 template class llvm::LoopBase<BasicBlock, Loop>;
41 template class llvm::LoopInfoBase<BasicBlock, Loop>;
43 // Always verify loopinfo if expensive checking is enabled.
44 #ifdef EXPENSIVE_CHECKS
45 bool llvm::VerifyLoopInfo = true;
47 bool llvm::VerifyLoopInfo = false;
49 static cl::opt<bool, true>
50 VerifyLoopInfoX("verify-loop-info", cl::location(VerifyLoopInfo),
51 cl::Hidden, cl::desc("Verify loop info (time consuming)"));
53 //===----------------------------------------------------------------------===//
54 // Loop implementation
57 bool Loop::isLoopInvariant(const Value *V) const {
58 if (const Instruction *I = dyn_cast<Instruction>(V))
60 return true; // All non-instructions are loop invariant
63 bool Loop::hasLoopInvariantOperands(const Instruction *I) const {
64 return all_of(I->operands(), [this](Value *V) { return isLoopInvariant(V); });
67 bool Loop::makeLoopInvariant(Value *V, bool &Changed,
68 Instruction *InsertPt) const {
69 if (Instruction *I = dyn_cast<Instruction>(V))
70 return makeLoopInvariant(I, Changed, InsertPt);
71 return true; // All non-instructions are loop-invariant.
74 bool Loop::makeLoopInvariant(Instruction *I, bool &Changed,
75 Instruction *InsertPt) const {
76 // Test if the value is already loop-invariant.
77 if (isLoopInvariant(I))
79 if (!isSafeToSpeculativelyExecute(I))
81 if (I->mayReadFromMemory())
83 // EH block instructions are immobile.
86 // Determine the insertion point, unless one was given.
88 BasicBlock *Preheader = getLoopPreheader();
89 // Without a preheader, hoisting is not feasible.
92 InsertPt = Preheader->getTerminator();
94 // Don't hoist instructions with loop-variant operands.
95 for (Value *Operand : I->operands())
96 if (!makeLoopInvariant(Operand, Changed, InsertPt))
100 I->moveBefore(InsertPt);
102 // There is possibility of hoisting this instruction above some arbitrary
103 // condition. Any metadata defined on it can be control dependent on this
104 // condition. Conservatively strip it here so that we don't give any wrong
105 // information to the optimizer.
106 I->dropUnknownNonDebugMetadata();
112 PHINode *Loop::getCanonicalInductionVariable() const {
113 BasicBlock *H = getHeader();
115 BasicBlock *Incoming = nullptr, *Backedge = nullptr;
116 pred_iterator PI = pred_begin(H);
117 assert(PI != pred_end(H) && "Loop must have at least one backedge!");
119 if (PI == pred_end(H))
120 return nullptr; // dead loop
122 if (PI != pred_end(H))
123 return nullptr; // multiple backedges?
125 if (contains(Incoming)) {
126 if (contains(Backedge))
128 std::swap(Incoming, Backedge);
129 } else if (!contains(Backedge))
132 // Loop over all of the PHI nodes, looking for a canonical indvar.
133 for (BasicBlock::iterator I = H->begin(); isa<PHINode>(I); ++I) {
134 PHINode *PN = cast<PHINode>(I);
135 if (ConstantInt *CI =
136 dyn_cast<ConstantInt>(PN->getIncomingValueForBlock(Incoming)))
138 if (Instruction *Inc =
139 dyn_cast<Instruction>(PN->getIncomingValueForBlock(Backedge)))
140 if (Inc->getOpcode() == Instruction::Add && Inc->getOperand(0) == PN)
141 if (ConstantInt *CI = dyn_cast<ConstantInt>(Inc->getOperand(1)))
148 // Check that 'BB' doesn't have any uses outside of the 'L'
149 static bool isBlockInLCSSAForm(const Loop &L, const BasicBlock &BB,
151 for (const Instruction &I : BB) {
152 // Tokens can't be used in PHI nodes and live-out tokens prevent loop
153 // optimizations, so for the purposes of considered LCSSA form, we
155 if (I.getType()->isTokenTy())
158 for (const Use &U : I.uses()) {
159 const Instruction *UI = cast<Instruction>(U.getUser());
160 const BasicBlock *UserBB = UI->getParent();
161 if (const PHINode *P = dyn_cast<PHINode>(UI))
162 UserBB = P->getIncomingBlock(U);
164 // Check the current block, as a fast-path, before checking whether
165 // the use is anywhere in the loop. Most values are used in the same
166 // block they are defined in. Also, blocks not reachable from the
167 // entry are special; uses in them don't need to go through PHIs.
168 if (UserBB != &BB && !L.contains(UserBB) &&
169 DT.isReachableFromEntry(UserBB))
176 bool Loop::isLCSSAForm(DominatorTree &DT) const {
177 // For each block we check that it doesn't have any uses outside of this loop.
178 return all_of(this->blocks(), [&](const BasicBlock *BB) {
179 return isBlockInLCSSAForm(*this, *BB, DT);
183 bool Loop::isRecursivelyLCSSAForm(DominatorTree &DT, const LoopInfo &LI) const {
184 // For each block we check that it doesn't have any uses outside of its
185 // innermost loop. This process will transitively guarantee that the current
186 // loop and all of the nested loops are in LCSSA form.
187 return all_of(this->blocks(), [&](const BasicBlock *BB) {
188 return isBlockInLCSSAForm(*LI.getLoopFor(BB), *BB, DT);
192 bool Loop::isLoopSimplifyForm() const {
193 // Normal-form loops have a preheader, a single backedge, and all of their
194 // exits have all their predecessors inside the loop.
195 return getLoopPreheader() && getLoopLatch() && hasDedicatedExits();
198 // Routines that reform the loop CFG and split edges often fail on indirectbr.
199 bool Loop::isSafeToClone() const {
200 // Return false if any loop blocks contain indirectbrs, or there are any calls
201 // to noduplicate functions.
202 for (BasicBlock *BB : this->blocks()) {
203 if (isa<IndirectBrInst>(BB->getTerminator()))
206 for (Instruction &I : *BB)
207 if (auto CS = CallSite(&I))
208 if (CS.cannotDuplicate())
214 MDNode *Loop::getLoopID() const {
215 MDNode *LoopID = nullptr;
216 if (BasicBlock *Latch = getLoopLatch()) {
217 LoopID = Latch->getTerminator()->getMetadata(LLVMContext::MD_loop);
219 assert(!getLoopLatch() &&
220 "The loop should have no single latch at this point");
221 // Go through each predecessor of the loop header and check the
222 // terminator for the metadata.
223 BasicBlock *H = getHeader();
224 for (BasicBlock *BB : this->blocks()) {
225 TerminatorInst *TI = BB->getTerminator();
226 MDNode *MD = nullptr;
228 // Check if this terminator branches to the loop header.
229 for (BasicBlock *Successor : TI->successors()) {
230 if (Successor == H) {
231 MD = TI->getMetadata(LLVMContext::MD_loop);
240 else if (MD != LoopID)
244 if (!LoopID || LoopID->getNumOperands() == 0 ||
245 LoopID->getOperand(0) != LoopID)
250 void Loop::setLoopID(MDNode *LoopID) const {
251 assert(LoopID && "Loop ID should not be null");
252 assert(LoopID->getNumOperands() > 0 && "Loop ID needs at least one operand");
253 assert(LoopID->getOperand(0) == LoopID && "Loop ID should refer to itself");
255 if (BasicBlock *Latch = getLoopLatch()) {
256 Latch->getTerminator()->setMetadata(LLVMContext::MD_loop, LoopID);
260 assert(!getLoopLatch() &&
261 "The loop should have no single latch at this point");
262 BasicBlock *H = getHeader();
263 for (BasicBlock *BB : this->blocks()) {
264 TerminatorInst *TI = BB->getTerminator();
265 for (BasicBlock *Successor : TI->successors()) {
267 TI->setMetadata(LLVMContext::MD_loop, LoopID);
272 void Loop::setLoopAlreadyUnrolled() {
273 MDNode *LoopID = getLoopID();
274 // First remove any existing loop unrolling metadata.
275 SmallVector<Metadata *, 4> MDs;
276 // Reserve first location for self reference to the LoopID metadata node.
277 MDs.push_back(nullptr);
280 for (unsigned i = 1, ie = LoopID->getNumOperands(); i < ie; ++i) {
281 bool IsUnrollMetadata = false;
282 MDNode *MD = dyn_cast<MDNode>(LoopID->getOperand(i));
284 const MDString *S = dyn_cast<MDString>(MD->getOperand(0));
285 IsUnrollMetadata = S && S->getString().startswith("llvm.loop.unroll.");
287 if (!IsUnrollMetadata)
288 MDs.push_back(LoopID->getOperand(i));
292 // Add unroll(disable) metadata to disable future unrolling.
293 LLVMContext &Context = getHeader()->getContext();
294 SmallVector<Metadata *, 1> DisableOperands;
295 DisableOperands.push_back(MDString::get(Context, "llvm.loop.unroll.disable"));
296 MDNode *DisableNode = MDNode::get(Context, DisableOperands);
297 MDs.push_back(DisableNode);
299 MDNode *NewLoopID = MDNode::get(Context, MDs);
300 // Set operand 0 to refer to the loop id itself.
301 NewLoopID->replaceOperandWith(0, NewLoopID);
302 setLoopID(NewLoopID);
305 bool Loop::isAnnotatedParallel() const {
306 MDNode *DesiredLoopIdMetadata = getLoopID();
308 if (!DesiredLoopIdMetadata)
311 // The loop branch contains the parallel loop metadata. In order to ensure
312 // that any parallel-loop-unaware optimization pass hasn't added loop-carried
313 // dependencies (thus converted the loop back to a sequential loop), check
314 // that all the memory instructions in the loop contain parallelism metadata
315 // that point to the same unique "loop id metadata" the loop branch does.
316 for (BasicBlock *BB : this->blocks()) {
317 for (Instruction &I : *BB) {
318 if (!I.mayReadOrWriteMemory())
321 // The memory instruction can refer to the loop identifier metadata
322 // directly or indirectly through another list metadata (in case of
323 // nested parallel loops). The loop identifier metadata refers to
324 // itself so we can check both cases with the same routine.
326 I.getMetadata(LLVMContext::MD_mem_parallel_loop_access);
331 bool LoopIdMDFound = false;
332 for (const MDOperand &MDOp : LoopIdMD->operands()) {
333 if (MDOp == DesiredLoopIdMetadata) {
334 LoopIdMDFound = true;
346 DebugLoc Loop::getStartLoc() const { return getLocRange().getStart(); }
348 Loop::LocRange Loop::getLocRange() const {
349 // If we have a debug location in the loop ID, then use it.
350 if (MDNode *LoopID = getLoopID()) {
352 // We use the first DebugLoc in the header as the start location of the loop
353 // and if there is a second DebugLoc in the header we use it as end location
355 for (unsigned i = 1, ie = LoopID->getNumOperands(); i < ie; ++i) {
356 if (DILocation *L = dyn_cast<DILocation>(LoopID->getOperand(i))) {
360 return LocRange(Start, DebugLoc(L));
365 return LocRange(Start);
368 // Try the pre-header first.
369 if (BasicBlock *PHeadBB = getLoopPreheader())
370 if (DebugLoc DL = PHeadBB->getTerminator()->getDebugLoc())
373 // If we have no pre-header or there are no instructions with debug
374 // info in it, try the header.
375 if (BasicBlock *HeadBB = getHeader())
376 return LocRange(HeadBB->getTerminator()->getDebugLoc());
381 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
382 LLVM_DUMP_METHOD void Loop::dump() const { print(dbgs()); }
384 LLVM_DUMP_METHOD void Loop::dumpVerbose() const {
385 print(dbgs(), /*Depth=*/0, /*Verbose=*/true);
389 //===----------------------------------------------------------------------===//
390 // UnloopUpdater implementation
394 /// Find the new parent loop for all blocks within the "unloop" whose last
395 /// backedges has just been removed.
396 class UnloopUpdater {
402 // Map unloop's immediate subloops to their nearest reachable parents. Nested
403 // loops within these subloops will not change parents. However, an immediate
404 // subloop's new parent will be the nearest loop reachable from either its own
405 // exits *or* any of its nested loop's exits.
406 DenseMap<Loop *, Loop *> SubloopParents;
408 // Flag the presence of an irreducible backedge whose destination is a block
409 // directly contained by the original unloop.
413 UnloopUpdater(Loop *UL, LoopInfo *LInfo)
414 : Unloop(*UL), LI(LInfo), DFS(UL), FoundIB(false) {}
416 void updateBlockParents();
418 void removeBlocksFromAncestors();
420 void updateSubloopParents();
423 Loop *getNearestLoop(BasicBlock *BB, Loop *BBLoop);
425 } // end anonymous namespace
427 /// Update the parent loop for all blocks that are directly contained within the
428 /// original "unloop".
429 void UnloopUpdater::updateBlockParents() {
430 if (Unloop.getNumBlocks()) {
431 // Perform a post order CFG traversal of all blocks within this loop,
432 // propagating the nearest loop from successors to predecessors.
433 LoopBlocksTraversal Traversal(DFS, LI);
434 for (BasicBlock *POI : Traversal) {
436 Loop *L = LI->getLoopFor(POI);
437 Loop *NL = getNearestLoop(POI, L);
440 // For reducible loops, NL is now an ancestor of Unloop.
441 assert((NL != &Unloop && (!NL || NL->contains(&Unloop))) &&
442 "uninitialized successor");
443 LI->changeLoopFor(POI, NL);
445 // Or the current block is part of a subloop, in which case its parent
447 assert((FoundIB || Unloop.contains(L)) && "uninitialized successor");
451 // Each irreducible loop within the unloop induces a round of iteration using
452 // the DFS result cached by Traversal.
453 bool Changed = FoundIB;
454 for (unsigned NIters = 0; Changed; ++NIters) {
455 assert(NIters < Unloop.getNumBlocks() && "runaway iterative algorithm");
457 // Iterate over the postorder list of blocks, propagating the nearest loop
458 // from successors to predecessors as before.
460 for (LoopBlocksDFS::POIterator POI = DFS.beginPostorder(),
461 POE = DFS.endPostorder();
464 Loop *L = LI->getLoopFor(*POI);
465 Loop *NL = getNearestLoop(*POI, L);
467 assert(NL != &Unloop && (!NL || NL->contains(&Unloop)) &&
468 "uninitialized successor");
469 LI->changeLoopFor(*POI, NL);
476 /// Remove unloop's blocks from all ancestors below their new parents.
477 void UnloopUpdater::removeBlocksFromAncestors() {
478 // Remove all unloop's blocks (including those in nested subloops) from
479 // ancestors below the new parent loop.
480 for (Loop::block_iterator BI = Unloop.block_begin(), BE = Unloop.block_end();
482 Loop *OuterParent = LI->getLoopFor(*BI);
483 if (Unloop.contains(OuterParent)) {
484 while (OuterParent->getParentLoop() != &Unloop)
485 OuterParent = OuterParent->getParentLoop();
486 OuterParent = SubloopParents[OuterParent];
488 // Remove blocks from former Ancestors except Unloop itself which will be
490 for (Loop *OldParent = Unloop.getParentLoop(); OldParent != OuterParent;
491 OldParent = OldParent->getParentLoop()) {
492 assert(OldParent && "new loop is not an ancestor of the original");
493 OldParent->removeBlockFromLoop(*BI);
498 /// Update the parent loop for all subloops directly nested within unloop.
499 void UnloopUpdater::updateSubloopParents() {
500 while (!Unloop.empty()) {
501 Loop *Subloop = *std::prev(Unloop.end());
502 Unloop.removeChildLoop(std::prev(Unloop.end()));
504 assert(SubloopParents.count(Subloop) && "DFS failed to visit subloop");
505 if (Loop *Parent = SubloopParents[Subloop])
506 Parent->addChildLoop(Subloop);
508 LI->addTopLevelLoop(Subloop);
512 /// Return the nearest parent loop among this block's successors. If a successor
513 /// is a subloop header, consider its parent to be the nearest parent of the
516 /// For subloop blocks, simply update SubloopParents and return NULL.
517 Loop *UnloopUpdater::getNearestLoop(BasicBlock *BB, Loop *BBLoop) {
519 // Initially for blocks directly contained by Unloop, NearLoop == Unloop and
520 // is considered uninitialized.
521 Loop *NearLoop = BBLoop;
523 Loop *Subloop = nullptr;
524 if (NearLoop != &Unloop && Unloop.contains(NearLoop)) {
526 // Find the subloop ancestor that is directly contained within Unloop.
527 while (Subloop->getParentLoop() != &Unloop) {
528 Subloop = Subloop->getParentLoop();
529 assert(Subloop && "subloop is not an ancestor of the original loop");
531 // Get the current nearest parent of the Subloop exits, initially Unloop.
532 NearLoop = SubloopParents.insert({Subloop, &Unloop}).first->second;
535 succ_iterator I = succ_begin(BB), E = succ_end(BB);
537 assert(!Subloop && "subloop blocks must have a successor");
538 NearLoop = nullptr; // unloop blocks may now exit the function.
540 for (; I != E; ++I) {
542 continue; // self loops are uninteresting
544 Loop *L = LI->getLoopFor(*I);
546 // This successor has not been processed. This path must lead to an
547 // irreducible backedge.
548 assert((FoundIB || !DFS.hasPostorder(*I)) && "should have seen IB");
551 if (L != &Unloop && Unloop.contains(L)) {
552 // Successor is in a subloop.
554 continue; // Branching within subloops. Ignore it.
556 // BB branches from the original into a subloop header.
557 assert(L->getParentLoop() == &Unloop && "cannot skip into nested loops");
559 // Get the current nearest parent of the Subloop's exits.
560 L = SubloopParents[L];
561 // L could be Unloop if the only exit was an irreducible backedge.
566 // Handle critical edges from Unloop into a sibling loop.
567 if (L && !L->contains(&Unloop)) {
568 L = L->getParentLoop();
570 // Remember the nearest parent loop among successors or subloop exits.
571 if (NearLoop == &Unloop || !NearLoop || NearLoop->contains(L))
575 SubloopParents[Subloop] = NearLoop;
581 LoopInfo::LoopInfo(const DomTreeBase<BasicBlock> &DomTree) { analyze(DomTree); }
583 bool LoopInfo::invalidate(Function &F, const PreservedAnalyses &PA,
584 FunctionAnalysisManager::Invalidator &) {
585 // Check whether the analysis, all analyses on functions, or the function's
586 // CFG have been preserved.
587 auto PAC = PA.getChecker<LoopAnalysis>();
588 return !(PAC.preserved() || PAC.preservedSet<AllAnalysesOn<Function>>() ||
589 PAC.preservedSet<CFGAnalyses>());
592 void LoopInfo::erase(Loop *Unloop) {
593 assert(!Unloop->isInvalid() && "Loop has already been erased!");
595 auto InvalidateOnExit = make_scope_exit([&]() { destroy(Unloop); });
597 // First handle the special case of no parent loop to simplify the algorithm.
598 if (!Unloop->getParentLoop()) {
599 // Since BBLoop had no parent, Unloop blocks are no longer in a loop.
600 for (Loop::block_iterator I = Unloop->block_begin(),
601 E = Unloop->block_end();
604 // Don't reparent blocks in subloops.
605 if (getLoopFor(*I) != Unloop)
608 // Blocks no longer have a parent but are still referenced by Unloop until
609 // the Unloop object is deleted.
610 changeLoopFor(*I, nullptr);
613 // Remove the loop from the top-level LoopInfo object.
614 for (iterator I = begin();; ++I) {
615 assert(I != end() && "Couldn't find loop");
622 // Move all of the subloops to the top-level.
623 while (!Unloop->empty())
624 addTopLevelLoop(Unloop->removeChildLoop(std::prev(Unloop->end())));
629 // Update the parent loop for all blocks within the loop. Blocks within
630 // subloops will not change parents.
631 UnloopUpdater Updater(Unloop, this);
632 Updater.updateBlockParents();
634 // Remove blocks from former ancestor loops.
635 Updater.removeBlocksFromAncestors();
637 // Add direct subloops as children in their new parent loop.
638 Updater.updateSubloopParents();
640 // Remove unloop from its parent loop.
641 Loop *ParentLoop = Unloop->getParentLoop();
642 for (Loop::iterator I = ParentLoop->begin();; ++I) {
643 assert(I != ParentLoop->end() && "Couldn't find loop");
645 ParentLoop->removeChildLoop(I);
651 AnalysisKey LoopAnalysis::Key;
653 LoopInfo LoopAnalysis::run(Function &F, FunctionAnalysisManager &AM) {
654 // FIXME: Currently we create a LoopInfo from scratch for every function.
655 // This may prove to be too wasteful due to deallocating and re-allocating
656 // memory each time for the underlying map and vector datastructures. At some
657 // point it may prove worthwhile to use a freelist and recycle LoopInfo
658 // objects. I don't want to add that kind of complexity until the scope of
659 // the problem is better understood.
661 LI.analyze(AM.getResult<DominatorTreeAnalysis>(F));
665 PreservedAnalyses LoopPrinterPass::run(Function &F,
666 FunctionAnalysisManager &AM) {
667 AM.getResult<LoopAnalysis>(F).print(OS);
668 return PreservedAnalyses::all();
671 void llvm::printLoop(Loop &L, raw_ostream &OS, const std::string &Banner) {
673 if (forcePrintModuleIR()) {
674 // handling -print-module-scope
675 OS << Banner << " (loop: ";
676 L.getHeader()->printAsOperand(OS, false);
679 // printing whole module
680 OS << *L.getHeader()->getModule();
686 auto *PreHeader = L.getLoopPreheader();
688 OS << "\n; Preheader:";
689 PreHeader->print(OS);
693 for (auto *Block : L.blocks())
697 OS << "Printing <null> block";
699 SmallVector<BasicBlock *, 8> ExitBlocks;
700 L.getExitBlocks(ExitBlocks);
701 if (!ExitBlocks.empty()) {
702 OS << "\n; Exit blocks";
703 for (auto *Block : ExitBlocks)
707 OS << "Printing <null> block";
711 //===----------------------------------------------------------------------===//
712 // LoopInfo implementation
715 char LoopInfoWrapperPass::ID = 0;
716 INITIALIZE_PASS_BEGIN(LoopInfoWrapperPass, "loops", "Natural Loop Information",
718 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
719 INITIALIZE_PASS_END(LoopInfoWrapperPass, "loops", "Natural Loop Information",
722 bool LoopInfoWrapperPass::runOnFunction(Function &) {
724 LI.analyze(getAnalysis<DominatorTreeWrapperPass>().getDomTree());
728 void LoopInfoWrapperPass::verifyAnalysis() const {
729 // LoopInfoWrapperPass is a FunctionPass, but verifying every loop in the
730 // function each time verifyAnalysis is called is very expensive. The
731 // -verify-loop-info option can enable this. In order to perform some
732 // checking by default, LoopPass has been taught to call verifyLoop manually
733 // during loop pass sequences.
734 if (VerifyLoopInfo) {
735 auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
740 void LoopInfoWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
741 AU.setPreservesAll();
742 AU.addRequired<DominatorTreeWrapperPass>();
745 void LoopInfoWrapperPass::print(raw_ostream &OS, const Module *) const {
749 PreservedAnalyses LoopVerifierPass::run(Function &F,
750 FunctionAnalysisManager &AM) {
751 LoopInfo &LI = AM.getResult<LoopAnalysis>(F);
752 auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
754 return PreservedAnalyses::all();
757 //===----------------------------------------------------------------------===//
758 // LoopBlocksDFS implementation
761 /// Traverse the loop blocks and store the DFS result.
762 /// Useful for clients that just want the final DFS result and don't need to
763 /// visit blocks during the initial traversal.
764 void LoopBlocksDFS::perform(LoopInfo *LI) {
765 LoopBlocksTraversal Traversal(*this, LI);
766 for (LoopBlocksTraversal::POTIterator POI = Traversal.begin(),
767 POE = Traversal.end();