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/IR/CFG.h"
25 #include "llvm/IR/Constants.h"
26 #include "llvm/IR/DebugLoc.h"
27 #include "llvm/IR/Dominators.h"
28 #include "llvm/IR/Instructions.h"
29 #include "llvm/IR/LLVMContext.h"
30 #include "llvm/IR/Metadata.h"
31 #include "llvm/IR/PassManager.h"
32 #include "llvm/Support/CommandLine.h"
33 #include "llvm/Support/Debug.h"
34 #include "llvm/Support/raw_ostream.h"
38 // Explicitly instantiate methods in LoopInfoImpl.h for IR-level Loops.
39 template class llvm::LoopBase<BasicBlock, Loop>;
40 template class llvm::LoopInfoBase<BasicBlock, Loop>;
42 // Always verify loopinfo if expensive checking is enabled.
43 #ifdef EXPENSIVE_CHECKS
44 bool llvm::VerifyLoopInfo = true;
46 bool llvm::VerifyLoopInfo = false;
48 static cl::opt<bool, true>
49 VerifyLoopInfoX("verify-loop-info", cl::location(VerifyLoopInfo),
50 cl::Hidden, cl::desc("Verify loop info (time consuming)"));
52 //===----------------------------------------------------------------------===//
53 // Loop implementation
56 bool Loop::isLoopInvariant(const Value *V) const {
57 if (const Instruction *I = dyn_cast<Instruction>(V))
59 return true; // All non-instructions are loop invariant
62 bool Loop::hasLoopInvariantOperands(const Instruction *I) const {
63 return all_of(I->operands(), [this](Value *V) { return isLoopInvariant(V); });
66 bool Loop::makeLoopInvariant(Value *V, bool &Changed,
67 Instruction *InsertPt) const {
68 if (Instruction *I = dyn_cast<Instruction>(V))
69 return makeLoopInvariant(I, Changed, InsertPt);
70 return true; // All non-instructions are loop-invariant.
73 bool Loop::makeLoopInvariant(Instruction *I, bool &Changed,
74 Instruction *InsertPt) const {
75 // Test if the value is already loop-invariant.
76 if (isLoopInvariant(I))
78 if (!isSafeToSpeculativelyExecute(I))
80 if (I->mayReadFromMemory())
82 // EH block instructions are immobile.
85 // Determine the insertion point, unless one was given.
87 BasicBlock *Preheader = getLoopPreheader();
88 // Without a preheader, hoisting is not feasible.
91 InsertPt = Preheader->getTerminator();
93 // Don't hoist instructions with loop-variant operands.
94 for (Value *Operand : I->operands())
95 if (!makeLoopInvariant(Operand, Changed, InsertPt))
99 I->moveBefore(InsertPt);
101 // There is possibility of hoisting this instruction above some arbitrary
102 // condition. Any metadata defined on it can be control dependent on this
103 // condition. Conservatively strip it here so that we don't give any wrong
104 // information to the optimizer.
105 I->dropUnknownNonDebugMetadata();
111 PHINode *Loop::getCanonicalInductionVariable() const {
112 BasicBlock *H = getHeader();
114 BasicBlock *Incoming = nullptr, *Backedge = nullptr;
115 pred_iterator PI = pred_begin(H);
116 assert(PI != pred_end(H) && "Loop must have at least one backedge!");
118 if (PI == pred_end(H))
119 return nullptr; // dead loop
121 if (PI != pred_end(H))
122 return nullptr; // multiple backedges?
124 if (contains(Incoming)) {
125 if (contains(Backedge))
127 std::swap(Incoming, Backedge);
128 } else if (!contains(Backedge))
131 // Loop over all of the PHI nodes, looking for a canonical indvar.
132 for (BasicBlock::iterator I = H->begin(); isa<PHINode>(I); ++I) {
133 PHINode *PN = cast<PHINode>(I);
134 if (ConstantInt *CI =
135 dyn_cast<ConstantInt>(PN->getIncomingValueForBlock(Incoming)))
137 if (Instruction *Inc =
138 dyn_cast<Instruction>(PN->getIncomingValueForBlock(Backedge)))
139 if (Inc->getOpcode() == Instruction::Add && Inc->getOperand(0) == PN)
140 if (ConstantInt *CI = dyn_cast<ConstantInt>(Inc->getOperand(1)))
147 // Check that 'BB' doesn't have any uses outside of the 'L'
148 static bool isBlockInLCSSAForm(const Loop &L, const BasicBlock &BB,
150 for (const Instruction &I : BB) {
151 // Tokens can't be used in PHI nodes and live-out tokens prevent loop
152 // optimizations, so for the purposes of considered LCSSA form, we
154 if (I.getType()->isTokenTy())
157 for (const Use &U : I.uses()) {
158 const Instruction *UI = cast<Instruction>(U.getUser());
159 const BasicBlock *UserBB = UI->getParent();
160 if (const PHINode *P = dyn_cast<PHINode>(UI))
161 UserBB = P->getIncomingBlock(U);
163 // Check the current block, as a fast-path, before checking whether
164 // the use is anywhere in the loop. Most values are used in the same
165 // block they are defined in. Also, blocks not reachable from the
166 // entry are special; uses in them don't need to go through PHIs.
167 if (UserBB != &BB && !L.contains(UserBB) &&
168 DT.isReachableFromEntry(UserBB))
175 bool Loop::isLCSSAForm(DominatorTree &DT) const {
176 // For each block we check that it doesn't have any uses outside of this loop.
177 return all_of(this->blocks(), [&](const BasicBlock *BB) {
178 return isBlockInLCSSAForm(*this, *BB, DT);
182 bool Loop::isRecursivelyLCSSAForm(DominatorTree &DT, const LoopInfo &LI) const {
183 // For each block we check that it doesn't have any uses outside of its
184 // innermost loop. This process will transitively guarantee that the current
185 // loop and all of the nested loops are in LCSSA form.
186 return all_of(this->blocks(), [&](const BasicBlock *BB) {
187 return isBlockInLCSSAForm(*LI.getLoopFor(BB), *BB, DT);
191 bool Loop::isLoopSimplifyForm() const {
192 // Normal-form loops have a preheader, a single backedge, and all of their
193 // exits have all their predecessors inside the loop.
194 return getLoopPreheader() && getLoopLatch() && hasDedicatedExits();
197 // Routines that reform the loop CFG and split edges often fail on indirectbr.
198 bool Loop::isSafeToClone() const {
199 // Return false if any loop blocks contain indirectbrs, or there are any calls
200 // to noduplicate functions.
201 for (BasicBlock *BB : this->blocks()) {
202 if (isa<IndirectBrInst>(BB->getTerminator()))
205 for (Instruction &I : *BB)
206 if (auto CS = CallSite(&I))
207 if (CS.cannotDuplicate())
213 MDNode *Loop::getLoopID() const {
214 MDNode *LoopID = nullptr;
215 if (BasicBlock *Latch = getLoopLatch()) {
216 LoopID = Latch->getTerminator()->getMetadata(LLVMContext::MD_loop);
218 assert(!getLoopLatch() &&
219 "The loop should have no single latch at this point");
220 // Go through each predecessor of the loop header and check the
221 // terminator for the metadata.
222 BasicBlock *H = getHeader();
223 for (BasicBlock *BB : this->blocks()) {
224 TerminatorInst *TI = BB->getTerminator();
225 MDNode *MD = nullptr;
227 // Check if this terminator branches to the loop header.
228 for (BasicBlock *Successor : TI->successors()) {
229 if (Successor == H) {
230 MD = TI->getMetadata(LLVMContext::MD_loop);
239 else if (MD != LoopID)
243 if (!LoopID || LoopID->getNumOperands() == 0 ||
244 LoopID->getOperand(0) != LoopID)
249 void Loop::setLoopID(MDNode *LoopID) const {
250 assert(LoopID && "Loop ID should not be null");
251 assert(LoopID->getNumOperands() > 0 && "Loop ID needs at least one operand");
252 assert(LoopID->getOperand(0) == LoopID && "Loop ID should refer to itself");
254 if (BasicBlock *Latch = getLoopLatch()) {
255 Latch->getTerminator()->setMetadata(LLVMContext::MD_loop, LoopID);
259 assert(!getLoopLatch() &&
260 "The loop should have no single latch at this point");
261 BasicBlock *H = getHeader();
262 for (BasicBlock *BB : this->blocks()) {
263 TerminatorInst *TI = BB->getTerminator();
264 for (BasicBlock *Successor : TI->successors()) {
266 TI->setMetadata(LLVMContext::MD_loop, LoopID);
271 void Loop::setLoopAlreadyUnrolled() {
272 MDNode *LoopID = getLoopID();
273 // First remove any existing loop unrolling metadata.
274 SmallVector<Metadata *, 4> MDs;
275 // Reserve first location for self reference to the LoopID metadata node.
276 MDs.push_back(nullptr);
279 for (unsigned i = 1, ie = LoopID->getNumOperands(); i < ie; ++i) {
280 bool IsUnrollMetadata = false;
281 MDNode *MD = dyn_cast<MDNode>(LoopID->getOperand(i));
283 const MDString *S = dyn_cast<MDString>(MD->getOperand(0));
284 IsUnrollMetadata = S && S->getString().startswith("llvm.loop.unroll.");
286 if (!IsUnrollMetadata)
287 MDs.push_back(LoopID->getOperand(i));
291 // Add unroll(disable) metadata to disable future unrolling.
292 LLVMContext &Context = getHeader()->getContext();
293 SmallVector<Metadata *, 1> DisableOperands;
294 DisableOperands.push_back(MDString::get(Context, "llvm.loop.unroll.disable"));
295 MDNode *DisableNode = MDNode::get(Context, DisableOperands);
296 MDs.push_back(DisableNode);
298 MDNode *NewLoopID = MDNode::get(Context, MDs);
299 // Set operand 0 to refer to the loop id itself.
300 NewLoopID->replaceOperandWith(0, NewLoopID);
301 setLoopID(NewLoopID);
304 bool Loop::isAnnotatedParallel() const {
305 MDNode *DesiredLoopIdMetadata = getLoopID();
307 if (!DesiredLoopIdMetadata)
310 // The loop branch contains the parallel loop metadata. In order to ensure
311 // that any parallel-loop-unaware optimization pass hasn't added loop-carried
312 // dependencies (thus converted the loop back to a sequential loop), check
313 // that all the memory instructions in the loop contain parallelism metadata
314 // that point to the same unique "loop id metadata" the loop branch does.
315 for (BasicBlock *BB : this->blocks()) {
316 for (Instruction &I : *BB) {
317 if (!I.mayReadOrWriteMemory())
320 // The memory instruction can refer to the loop identifier metadata
321 // directly or indirectly through another list metadata (in case of
322 // nested parallel loops). The loop identifier metadata refers to
323 // itself so we can check both cases with the same routine.
325 I.getMetadata(LLVMContext::MD_mem_parallel_loop_access);
330 bool LoopIdMDFound = false;
331 for (const MDOperand &MDOp : LoopIdMD->operands()) {
332 if (MDOp == DesiredLoopIdMetadata) {
333 LoopIdMDFound = true;
345 DebugLoc Loop::getStartLoc() const { return getLocRange().getStart(); }
347 Loop::LocRange Loop::getLocRange() const {
348 // If we have a debug location in the loop ID, then use it.
349 if (MDNode *LoopID = getLoopID()) {
351 // We use the first DebugLoc in the header as the start location of the loop
352 // and if there is a second DebugLoc in the header we use it as end location
354 for (unsigned i = 1, ie = LoopID->getNumOperands(); i < ie; ++i) {
355 if (DILocation *L = dyn_cast<DILocation>(LoopID->getOperand(i))) {
359 return LocRange(Start, DebugLoc(L));
364 return LocRange(Start);
367 // Try the pre-header first.
368 if (BasicBlock *PHeadBB = getLoopPreheader())
369 if (DebugLoc DL = PHeadBB->getTerminator()->getDebugLoc())
372 // If we have no pre-header or there are no instructions with debug
373 // info in it, try the header.
374 if (BasicBlock *HeadBB = getHeader())
375 return LocRange(HeadBB->getTerminator()->getDebugLoc());
380 bool Loop::hasDedicatedExits() const {
381 // Each predecessor of each exit block of a normal loop is contained
383 SmallVector<BasicBlock *, 4> ExitBlocks;
384 getExitBlocks(ExitBlocks);
385 for (BasicBlock *BB : ExitBlocks)
386 for (BasicBlock *Predecessor : predecessors(BB))
387 if (!contains(Predecessor))
389 // All the requirements are met.
393 void Loop::getUniqueExitBlocks(
394 SmallVectorImpl<BasicBlock *> &ExitBlocks) const {
395 assert(hasDedicatedExits() &&
396 "getUniqueExitBlocks assumes the loop has canonical form exits!");
398 SmallVector<BasicBlock *, 32> SwitchExitBlocks;
399 for (BasicBlock *BB : this->blocks()) {
400 SwitchExitBlocks.clear();
401 for (BasicBlock *Successor : successors(BB)) {
402 // If block is inside the loop then it is not an exit block.
403 if (contains(Successor))
406 pred_iterator PI = pred_begin(Successor);
407 BasicBlock *FirstPred = *PI;
409 // If current basic block is this exit block's first predecessor
410 // then only insert exit block in to the output ExitBlocks vector.
411 // This ensures that same exit block is not inserted twice into
412 // ExitBlocks vector.
416 // If a terminator has more then two successors, for example SwitchInst,
417 // then it is possible that there are multiple edges from current block
418 // to one exit block.
419 if (std::distance(succ_begin(BB), succ_end(BB)) <= 2) {
420 ExitBlocks.push_back(Successor);
424 // In case of multiple edges from current block to exit block, collect
425 // only one edge in ExitBlocks. Use switchExitBlocks to keep track of
427 if (!is_contained(SwitchExitBlocks, Successor)) {
428 SwitchExitBlocks.push_back(Successor);
429 ExitBlocks.push_back(Successor);
435 BasicBlock *Loop::getUniqueExitBlock() const {
436 SmallVector<BasicBlock *, 8> UniqueExitBlocks;
437 getUniqueExitBlocks(UniqueExitBlocks);
438 if (UniqueExitBlocks.size() == 1)
439 return UniqueExitBlocks[0];
443 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
444 LLVM_DUMP_METHOD void Loop::dump() const { print(dbgs()); }
446 LLVM_DUMP_METHOD void Loop::dumpVerbose() const {
447 print(dbgs(), /*Depth=*/0, /*Verbose=*/true);
451 //===----------------------------------------------------------------------===//
452 // UnloopUpdater implementation
456 /// Find the new parent loop for all blocks within the "unloop" whose last
457 /// backedges has just been removed.
458 class UnloopUpdater {
464 // Map unloop's immediate subloops to their nearest reachable parents. Nested
465 // loops within these subloops will not change parents. However, an immediate
466 // subloop's new parent will be the nearest loop reachable from either its own
467 // exits *or* any of its nested loop's exits.
468 DenseMap<Loop *, Loop *> SubloopParents;
470 // Flag the presence of an irreducible backedge whose destination is a block
471 // directly contained by the original unloop.
475 UnloopUpdater(Loop *UL, LoopInfo *LInfo)
476 : Unloop(*UL), LI(LInfo), DFS(UL), FoundIB(false) {}
478 void updateBlockParents();
480 void removeBlocksFromAncestors();
482 void updateSubloopParents();
485 Loop *getNearestLoop(BasicBlock *BB, Loop *BBLoop);
487 } // end anonymous namespace
489 /// Update the parent loop for all blocks that are directly contained within the
490 /// original "unloop".
491 void UnloopUpdater::updateBlockParents() {
492 if (Unloop.getNumBlocks()) {
493 // Perform a post order CFG traversal of all blocks within this loop,
494 // propagating the nearest loop from successors to predecessors.
495 LoopBlocksTraversal Traversal(DFS, LI);
496 for (BasicBlock *POI : Traversal) {
498 Loop *L = LI->getLoopFor(POI);
499 Loop *NL = getNearestLoop(POI, L);
502 // For reducible loops, NL is now an ancestor of Unloop.
503 assert((NL != &Unloop && (!NL || NL->contains(&Unloop))) &&
504 "uninitialized successor");
505 LI->changeLoopFor(POI, NL);
507 // Or the current block is part of a subloop, in which case its parent
509 assert((FoundIB || Unloop.contains(L)) && "uninitialized successor");
513 // Each irreducible loop within the unloop induces a round of iteration using
514 // the DFS result cached by Traversal.
515 bool Changed = FoundIB;
516 for (unsigned NIters = 0; Changed; ++NIters) {
517 assert(NIters < Unloop.getNumBlocks() && "runaway iterative algorithm");
519 // Iterate over the postorder list of blocks, propagating the nearest loop
520 // from successors to predecessors as before.
522 for (LoopBlocksDFS::POIterator POI = DFS.beginPostorder(),
523 POE = DFS.endPostorder();
526 Loop *L = LI->getLoopFor(*POI);
527 Loop *NL = getNearestLoop(*POI, L);
529 assert(NL != &Unloop && (!NL || NL->contains(&Unloop)) &&
530 "uninitialized successor");
531 LI->changeLoopFor(*POI, NL);
538 /// Remove unloop's blocks from all ancestors below their new parents.
539 void UnloopUpdater::removeBlocksFromAncestors() {
540 // Remove all unloop's blocks (including those in nested subloops) from
541 // ancestors below the new parent loop.
542 for (Loop::block_iterator BI = Unloop.block_begin(), BE = Unloop.block_end();
544 Loop *OuterParent = LI->getLoopFor(*BI);
545 if (Unloop.contains(OuterParent)) {
546 while (OuterParent->getParentLoop() != &Unloop)
547 OuterParent = OuterParent->getParentLoop();
548 OuterParent = SubloopParents[OuterParent];
550 // Remove blocks from former Ancestors except Unloop itself which will be
552 for (Loop *OldParent = Unloop.getParentLoop(); OldParent != OuterParent;
553 OldParent = OldParent->getParentLoop()) {
554 assert(OldParent && "new loop is not an ancestor of the original");
555 OldParent->removeBlockFromLoop(*BI);
560 /// Update the parent loop for all subloops directly nested within unloop.
561 void UnloopUpdater::updateSubloopParents() {
562 while (!Unloop.empty()) {
563 Loop *Subloop = *std::prev(Unloop.end());
564 Unloop.removeChildLoop(std::prev(Unloop.end()));
566 assert(SubloopParents.count(Subloop) && "DFS failed to visit subloop");
567 if (Loop *Parent = SubloopParents[Subloop])
568 Parent->addChildLoop(Subloop);
570 LI->addTopLevelLoop(Subloop);
574 /// Return the nearest parent loop among this block's successors. If a successor
575 /// is a subloop header, consider its parent to be the nearest parent of the
578 /// For subloop blocks, simply update SubloopParents and return NULL.
579 Loop *UnloopUpdater::getNearestLoop(BasicBlock *BB, Loop *BBLoop) {
581 // Initially for blocks directly contained by Unloop, NearLoop == Unloop and
582 // is considered uninitialized.
583 Loop *NearLoop = BBLoop;
585 Loop *Subloop = nullptr;
586 if (NearLoop != &Unloop && Unloop.contains(NearLoop)) {
588 // Find the subloop ancestor that is directly contained within Unloop.
589 while (Subloop->getParentLoop() != &Unloop) {
590 Subloop = Subloop->getParentLoop();
591 assert(Subloop && "subloop is not an ancestor of the original loop");
593 // Get the current nearest parent of the Subloop exits, initially Unloop.
594 NearLoop = SubloopParents.insert({Subloop, &Unloop}).first->second;
597 succ_iterator I = succ_begin(BB), E = succ_end(BB);
599 assert(!Subloop && "subloop blocks must have a successor");
600 NearLoop = nullptr; // unloop blocks may now exit the function.
602 for (; I != E; ++I) {
604 continue; // self loops are uninteresting
606 Loop *L = LI->getLoopFor(*I);
608 // This successor has not been processed. This path must lead to an
609 // irreducible backedge.
610 assert((FoundIB || !DFS.hasPostorder(*I)) && "should have seen IB");
613 if (L != &Unloop && Unloop.contains(L)) {
614 // Successor is in a subloop.
616 continue; // Branching within subloops. Ignore it.
618 // BB branches from the original into a subloop header.
619 assert(L->getParentLoop() == &Unloop && "cannot skip into nested loops");
621 // Get the current nearest parent of the Subloop's exits.
622 L = SubloopParents[L];
623 // L could be Unloop if the only exit was an irreducible backedge.
628 // Handle critical edges from Unloop into a sibling loop.
629 if (L && !L->contains(&Unloop)) {
630 L = L->getParentLoop();
632 // Remember the nearest parent loop among successors or subloop exits.
633 if (NearLoop == &Unloop || !NearLoop || NearLoop->contains(L))
637 SubloopParents[Subloop] = NearLoop;
643 LoopInfo::LoopInfo(const DomTreeBase<BasicBlock> &DomTree) { analyze(DomTree); }
645 bool LoopInfo::invalidate(Function &F, const PreservedAnalyses &PA,
646 FunctionAnalysisManager::Invalidator &) {
647 // Check whether the analysis, all analyses on functions, or the function's
648 // CFG have been preserved.
649 auto PAC = PA.getChecker<LoopAnalysis>();
650 return !(PAC.preserved() || PAC.preservedSet<AllAnalysesOn<Function>>() ||
651 PAC.preservedSet<CFGAnalyses>());
654 void LoopInfo::erase(Loop *Unloop) {
655 assert(!Unloop->isInvalid() && "Loop has already been erased!");
657 auto InvalidateOnExit = make_scope_exit([&]() { destroy(Unloop); });
659 // First handle the special case of no parent loop to simplify the algorithm.
660 if (!Unloop->getParentLoop()) {
661 // Since BBLoop had no parent, Unloop blocks are no longer in a loop.
662 for (Loop::block_iterator I = Unloop->block_begin(),
663 E = Unloop->block_end();
666 // Don't reparent blocks in subloops.
667 if (getLoopFor(*I) != Unloop)
670 // Blocks no longer have a parent but are still referenced by Unloop until
671 // the Unloop object is deleted.
672 changeLoopFor(*I, nullptr);
675 // Remove the loop from the top-level LoopInfo object.
676 for (iterator I = begin();; ++I) {
677 assert(I != end() && "Couldn't find loop");
684 // Move all of the subloops to the top-level.
685 while (!Unloop->empty())
686 addTopLevelLoop(Unloop->removeChildLoop(std::prev(Unloop->end())));
691 // Update the parent loop for all blocks within the loop. Blocks within
692 // subloops will not change parents.
693 UnloopUpdater Updater(Unloop, this);
694 Updater.updateBlockParents();
696 // Remove blocks from former ancestor loops.
697 Updater.removeBlocksFromAncestors();
699 // Add direct subloops as children in their new parent loop.
700 Updater.updateSubloopParents();
702 // Remove unloop from its parent loop.
703 Loop *ParentLoop = Unloop->getParentLoop();
704 for (Loop::iterator I = ParentLoop->begin();; ++I) {
705 assert(I != ParentLoop->end() && "Couldn't find loop");
707 ParentLoop->removeChildLoop(I);
713 AnalysisKey LoopAnalysis::Key;
715 LoopInfo LoopAnalysis::run(Function &F, FunctionAnalysisManager &AM) {
716 // FIXME: Currently we create a LoopInfo from scratch for every function.
717 // This may prove to be too wasteful due to deallocating and re-allocating
718 // memory each time for the underlying map and vector datastructures. At some
719 // point it may prove worthwhile to use a freelist and recycle LoopInfo
720 // objects. I don't want to add that kind of complexity until the scope of
721 // the problem is better understood.
723 LI.analyze(AM.getResult<DominatorTreeAnalysis>(F));
727 PreservedAnalyses LoopPrinterPass::run(Function &F,
728 FunctionAnalysisManager &AM) {
729 AM.getResult<LoopAnalysis>(F).print(OS);
730 return PreservedAnalyses::all();
733 void llvm::printLoop(Loop &L, raw_ostream &OS, const std::string &Banner) {
735 if (forcePrintModuleIR()) {
736 // handling -print-module-scope
737 OS << Banner << " (loop: ";
738 L.getHeader()->printAsOperand(OS, false);
741 // printing whole module
742 OS << *L.getHeader()->getModule();
748 auto *PreHeader = L.getLoopPreheader();
750 OS << "\n; Preheader:";
751 PreHeader->print(OS);
755 for (auto *Block : L.blocks())
759 OS << "Printing <null> block";
761 SmallVector<BasicBlock *, 8> ExitBlocks;
762 L.getExitBlocks(ExitBlocks);
763 if (!ExitBlocks.empty()) {
764 OS << "\n; Exit blocks";
765 for (auto *Block : ExitBlocks)
769 OS << "Printing <null> block";
773 //===----------------------------------------------------------------------===//
774 // LoopInfo implementation
777 char LoopInfoWrapperPass::ID = 0;
778 INITIALIZE_PASS_BEGIN(LoopInfoWrapperPass, "loops", "Natural Loop Information",
780 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
781 INITIALIZE_PASS_END(LoopInfoWrapperPass, "loops", "Natural Loop Information",
784 bool LoopInfoWrapperPass::runOnFunction(Function &) {
786 LI.analyze(getAnalysis<DominatorTreeWrapperPass>().getDomTree());
790 void LoopInfoWrapperPass::verifyAnalysis() const {
791 // LoopInfoWrapperPass is a FunctionPass, but verifying every loop in the
792 // function each time verifyAnalysis is called is very expensive. The
793 // -verify-loop-info option can enable this. In order to perform some
794 // checking by default, LoopPass has been taught to call verifyLoop manually
795 // during loop pass sequences.
796 if (VerifyLoopInfo) {
797 auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
802 void LoopInfoWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
803 AU.setPreservesAll();
804 AU.addRequired<DominatorTreeWrapperPass>();
807 void LoopInfoWrapperPass::print(raw_ostream &OS, const Module *) const {
811 PreservedAnalyses LoopVerifierPass::run(Function &F,
812 FunctionAnalysisManager &AM) {
813 LoopInfo &LI = AM.getResult<LoopAnalysis>(F);
814 auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
816 return PreservedAnalyses::all();
819 //===----------------------------------------------------------------------===//
820 // LoopBlocksDFS implementation
823 /// Traverse the loop blocks and store the DFS result.
824 /// Useful for clients that just want the final DFS result and don't need to
825 /// visit blocks during the initial traversal.
826 void LoopBlocksDFS::perform(LoopInfo *LI) {
827 LoopBlocksTraversal Traversal(*this, LI);
828 for (LoopBlocksTraversal::POTIterator POI = Traversal.begin(),
829 POE = Traversal.end();