1//===- LoopInfo.cpp - Natural Loop Calculator -----------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file defines the LoopInfo class that is used to identify natural loops
10// and determine the loop depth of various nodes of the CFG. Note that the
11// loops identified may actually be several natural loops that share the same
12// header node... not just a single natural loop.
13//
14//===----------------------------------------------------------------------===//
15
16#include "llvm/Analysis/LoopInfo.h"
17#include "llvm/ADT/ScopeExit.h"
18#include "llvm/ADT/SmallPtrSet.h"
19#include "llvm/Analysis/IVDescriptors.h"
20#include "llvm/Analysis/LoopIterator.h"
21#include "llvm/Analysis/LoopNestAnalysis.h"
22#include "llvm/Analysis/MemorySSA.h"
23#include "llvm/Analysis/MemorySSAUpdater.h"
24#include "llvm/Analysis/ScalarEvolutionExpressions.h"
25#include "llvm/Analysis/ValueTracking.h"
26#include "llvm/Config/llvm-config.h"
27#include "llvm/IR/CFG.h"
28#include "llvm/IR/Constants.h"
29#include "llvm/IR/DebugLoc.h"
30#include "llvm/IR/Dominators.h"
31#include "llvm/IR/Instructions.h"
32#include "llvm/IR/LLVMContext.h"
33#include "llvm/IR/Metadata.h"
34#include "llvm/IR/Module.h"
35#include "llvm/IR/PassManager.h"
36#include "llvm/IR/PrintPasses.h"
37#include "llvm/IR/ProfDataUtils.h"
38#include "llvm/InitializePasses.h"
39#include "llvm/Support/CommandLine.h"
40#include "llvm/Support/Compiler.h"
41#include "llvm/Support/GenericLoopInfoImpl.h"
42#include "llvm/Support/raw_ostream.h"
43using namespace llvm;
44
45// Explicitly instantiate methods in LoopInfoImpl.h for IR-level Loops.
46template class LLVM_EXPORT_TEMPLATE llvm::LoopBase<BasicBlock, Loop>;
47template class LLVM_EXPORT_TEMPLATE llvm::LoopInfoBase<BasicBlock, Loop>;
48
49// Always verify loopinfo if expensive checking is enabled.
50#ifdef EXPENSIVE_CHECKS
51bool llvm::VerifyLoopInfo = true;
52#else
53bool llvm::VerifyLoopInfo = false;
54#endif
55static cl::opt<bool, true>
56 VerifyLoopInfoX("verify-loop-info", cl::location(L&: VerifyLoopInfo),
57 cl::Hidden, cl::desc("Verify loop info (time consuming)"));
58
59namespace llvm {
60extern cl::opt<bool> ProfcheckDisableMetadataFixes;
61} // end namespace llvm
62
63//===----------------------------------------------------------------------===//
64// Loop implementation
65//
66
67bool Loop::isLoopInvariant(const Value *V) const {
68 if (const Instruction *I = dyn_cast<Instruction>(Val: V))
69 return !contains(Inst: I);
70 return true; // All non-instructions are loop invariant
71}
72
73bool Loop::hasLoopInvariantOperands(const Instruction *I) const {
74 return all_of(Range: I->operands(), P: [&](Value *V) { return isLoopInvariant(V); });
75}
76
77bool Loop::makeLoopInvariant(Value *V, bool &Changed, Instruction *InsertPt,
78 MemorySSAUpdater *MSSAU,
79 ScalarEvolution *SE) const {
80 if (Instruction *I = dyn_cast<Instruction>(Val: V))
81 return makeLoopInvariant(I, Changed, InsertPt, MSSAU, SE);
82 return true; // All non-instructions are loop-invariant.
83}
84
85bool Loop::makeLoopInvariant(Instruction *I, bool &Changed,
86 Instruction *InsertPt, MemorySSAUpdater *MSSAU,
87 ScalarEvolution *SE) const {
88 BasicBlock *OriginalParent = I->getParent();
89 // Test if the value is already loop-invariant.
90 if (isLoopInvariant(V: I))
91 return true;
92 if (!isSafeToSpeculativelyExecute(I))
93 return false;
94 if (I->mayReadFromMemory())
95 return false;
96 // EH block instructions are immobile.
97 if (I->isEHPad())
98 return false;
99 // Determine the insertion point, unless one was given.
100 if (!InsertPt) {
101 BasicBlock *Preheader = getLoopPreheader();
102 // Without a preheader, hoisting is not feasible.
103 if (!Preheader)
104 return false;
105 InsertPt = Preheader->getTerminator();
106 }
107 // Don't hoist instructions with loop-variant operands.
108 for (Value *Operand : I->operands())
109 if (!makeLoopInvariant(V: Operand, Changed, InsertPt, MSSAU, SE))
110 return false;
111
112 // Hoist.
113 I->moveBefore(InsertPos: InsertPt->getIterator());
114 if (MSSAU)
115 if (auto *MUD = MSSAU->getMemorySSA()->getMemoryAccess(I))
116 MSSAU->moveToPlace(What: MUD, BB: InsertPt->getParent(),
117 Where: MemorySSA::BeforeTerminator);
118
119 // We want to preserve profile metadata if possible. However, we need to
120 // ensure that profile metadata would remain the same outside of the loop.
121 // Given at this point we know the conditional is loop-invariant, we just
122 // need to worry about other control flow in the loop conditioned on values
123 // that are potentially not independent of the condition of the instruction
124 // we are interested in hoisting. Given this is not knowable in the general
125 // case, we only hoist from a loop header (which covers a reasonable number
126 // of cases) where we are guaranteed to not run into problems.
127 SmallVector<unsigned, 1> ProfileMetadataToPreserve;
128 if (!ProfcheckDisableMetadataFixes)
129 if (OriginalParent == getHeader())
130 ProfileMetadataToPreserve.push_back(Elt: LLVMContext::MD_prof);
131
132 // There is possibility of hoisting this instruction above some arbitrary
133 // condition. Any metadata defined on it can be control dependent on this
134 // condition. Conservatively strip it here so that we don't give any wrong
135 // information to the optimizer.
136 I->dropUnknownNonDebugMetadata(KnownIDs: ProfileMetadataToPreserve);
137
138 if (ProfileMetadataToPreserve.empty() && isa<SelectInst>(Val: I))
139 setExplicitlyUnknownBranchWeightsIfProfiled(I&: *I, PassName: "LoopInfo");
140
141 if (SE)
142 SE->forgetBlockAndLoopDispositions(V: I);
143
144 Changed = true;
145 return true;
146}
147
148bool Loop::getIncomingAndBackEdge(BasicBlock *&Incoming,
149 BasicBlock *&Backedge) const {
150 BasicBlock *H = getHeader();
151
152 Incoming = nullptr;
153 Backedge = nullptr;
154 pred_iterator PI = pred_begin(BB: H);
155 assert(PI != pred_end(H) && "Loop must have at least one backedge!");
156 Backedge = *PI++;
157 if (PI == pred_end(BB: H))
158 return false; // dead loop
159 Incoming = *PI++;
160 if (PI != pred_end(BB: H))
161 return false; // multiple backedges?
162
163 if (contains(BB: Incoming)) {
164 if (contains(BB: Backedge))
165 return false;
166 std::swap(a&: Incoming, b&: Backedge);
167 } else if (!contains(BB: Backedge))
168 return false;
169
170 assert(Incoming && Backedge && "expected non-null incoming and backedges");
171 return true;
172}
173
174PHINode *Loop::getCanonicalInductionVariable() const {
175 BasicBlock *H = getHeader();
176
177 BasicBlock *Incoming = nullptr, *Backedge = nullptr;
178 if (!getIncomingAndBackEdge(Incoming, Backedge))
179 return nullptr;
180
181 // Loop over all of the PHI nodes, looking for a canonical indvar.
182 for (BasicBlock::iterator I = H->begin(); isa<PHINode>(Val: I); ++I) {
183 PHINode *PN = cast<PHINode>(Val&: I);
184 if (ConstantInt *CI =
185 dyn_cast<ConstantInt>(Val: PN->getIncomingValueForBlock(BB: Incoming)))
186 if (CI->isZero())
187 if (Instruction *Inc =
188 dyn_cast<Instruction>(Val: PN->getIncomingValueForBlock(BB: Backedge)))
189 if (Inc->getOpcode() == Instruction::Add && Inc->getOperand(i: 0) == PN)
190 if (ConstantInt *CI = dyn_cast<ConstantInt>(Val: Inc->getOperand(i: 1)))
191 if (CI->isOne())
192 return PN;
193 }
194 return nullptr;
195}
196
197/// Get the latch condition instruction.
198ICmpInst *Loop::getLatchCmpInst() const {
199 if (BasicBlock *Latch = getLoopLatch())
200 if (CondBrInst *BI = dyn_cast_or_null<CondBrInst>(Val: Latch->getTerminator()))
201 return dyn_cast<ICmpInst>(Val: BI->getCondition());
202
203 return nullptr;
204}
205
206/// Return the final value of the loop induction variable if found.
207static Value *findFinalIVValue(const Loop &L, const PHINode &IndVar,
208 const Instruction &StepInst) {
209 ICmpInst *LatchCmpInst = L.getLatchCmpInst();
210 if (!LatchCmpInst)
211 return nullptr;
212
213 Value *Op0 = LatchCmpInst->getOperand(i_nocapture: 0);
214 Value *Op1 = LatchCmpInst->getOperand(i_nocapture: 1);
215 if (Op0 == &IndVar || Op0 == &StepInst)
216 return Op1;
217
218 if (Op1 == &IndVar || Op1 == &StepInst)
219 return Op0;
220
221 return nullptr;
222}
223
224std::optional<Loop::LoopBounds>
225Loop::LoopBounds::getBounds(const Loop &L, PHINode &IndVar,
226 ScalarEvolution &SE) {
227 InductionDescriptor IndDesc;
228 if (!InductionDescriptor::isInductionPHI(Phi: &IndVar, L: &L, SE: &SE, D&: IndDesc))
229 return std::nullopt;
230
231 Value *InitialIVValue = IndDesc.getStartValue();
232 Instruction *StepInst = IndDesc.getInductionBinOp();
233 if (!InitialIVValue || !StepInst)
234 return std::nullopt;
235
236 const SCEV *Step = IndDesc.getStep();
237 Value *StepInstOp1 = StepInst->getOperand(i: 1);
238 Value *StepInstOp0 = StepInst->getOperand(i: 0);
239 Value *StepValue = nullptr;
240 if (SE.getSCEV(V: StepInstOp1) == Step)
241 StepValue = StepInstOp1;
242 else if (SE.getSCEV(V: StepInstOp0) == Step)
243 StepValue = StepInstOp0;
244
245 Value *FinalIVValue = findFinalIVValue(L, IndVar, StepInst: *StepInst);
246 if (!FinalIVValue)
247 return std::nullopt;
248
249 return LoopBounds(L, *InitialIVValue, *StepInst, StepValue, *FinalIVValue,
250 SE);
251}
252
253using Direction = Loop::LoopBounds::Direction;
254
255ICmpInst::Predicate Loop::LoopBounds::getCanonicalPredicate() const {
256 BasicBlock *Latch = L.getLoopLatch();
257 assert(Latch && "Expecting valid latch");
258
259 CondBrInst *BI = cast<CondBrInst>(Val: Latch->getTerminator());
260
261 ICmpInst *LatchCmpInst = dyn_cast<ICmpInst>(Val: BI->getCondition());
262 assert(LatchCmpInst &&
263 "Expecting the latch compare instruction to be a CmpInst");
264
265 // Need to inverse the predicate when first successor is not the loop
266 // header
267 ICmpInst::Predicate Pred = (BI->getSuccessor(i: 0) == L.getHeader())
268 ? LatchCmpInst->getPredicate()
269 : LatchCmpInst->getInversePredicate();
270
271 if (LatchCmpInst->getOperand(i_nocapture: 0) == &getFinalIVValue())
272 Pred = ICmpInst::getSwappedPredicate(pred: Pred);
273
274 // Need to flip strictness of the predicate when the latch compare instruction
275 // is not using StepInst
276 if (LatchCmpInst->getOperand(i_nocapture: 0) == &getStepInst() ||
277 LatchCmpInst->getOperand(i_nocapture: 1) == &getStepInst())
278 return Pred;
279
280 // Cannot flip strictness of NE and EQ
281 if (Pred != ICmpInst::ICMP_NE && Pred != ICmpInst::ICMP_EQ)
282 return ICmpInst::getFlippedStrictnessPredicate(pred: Pred);
283
284 Direction D = getDirection();
285 if (D == Direction::Increasing)
286 return ICmpInst::ICMP_SLT;
287
288 if (D == Direction::Decreasing)
289 return ICmpInst::ICMP_SGT;
290
291 // If cannot determine the direction, then unable to find the canonical
292 // predicate
293 return ICmpInst::BAD_ICMP_PREDICATE;
294}
295
296Direction Loop::LoopBounds::getDirection() const {
297 if (const SCEVAddRecExpr *StepAddRecExpr =
298 dyn_cast<SCEVAddRecExpr>(Val: SE.getSCEV(V: &getStepInst())))
299 if (const SCEV *StepRecur = StepAddRecExpr->getStepRecurrence(SE)) {
300 if (SE.isKnownPositive(S: StepRecur))
301 return Direction::Increasing;
302 if (SE.isKnownNegative(S: StepRecur))
303 return Direction::Decreasing;
304 }
305
306 return Direction::Unknown;
307}
308
309std::optional<Loop::LoopBounds> Loop::getBounds(ScalarEvolution &SE) const {
310 if (PHINode *IndVar = getInductionVariable(SE))
311 return LoopBounds::getBounds(L: *this, IndVar&: *IndVar, SE);
312
313 return std::nullopt;
314}
315
316PHINode *Loop::getInductionVariable(ScalarEvolution &SE) const {
317 if (!isLoopSimplifyForm())
318 return nullptr;
319
320 BasicBlock *Header = getHeader();
321 assert(Header && "Expected a valid loop header");
322 ICmpInst *CmpInst = getLatchCmpInst();
323 if (!CmpInst)
324 return nullptr;
325
326 Value *LatchCmpOp0 = CmpInst->getOperand(i_nocapture: 0);
327 Value *LatchCmpOp1 = CmpInst->getOperand(i_nocapture: 1);
328
329 for (PHINode &IndVar : Header->phis()) {
330 InductionDescriptor IndDesc;
331 if (!InductionDescriptor::isInductionPHI(Phi: &IndVar, L: this, SE: &SE, D&: IndDesc))
332 continue;
333
334 BasicBlock *Latch = getLoopLatch();
335 Value *StepInst = IndVar.getIncomingValueForBlock(BB: Latch);
336
337 // case 1:
338 // IndVar = phi[{InitialValue, preheader}, {StepInst, latch}]
339 // StepInst = IndVar + step
340 // cmp = StepInst < FinalValue
341 if (StepInst == LatchCmpOp0 || StepInst == LatchCmpOp1)
342 return &IndVar;
343
344 // case 2:
345 // IndVar = phi[{InitialValue, preheader}, {StepInst, latch}]
346 // StepInst = IndVar + step
347 // cmp = IndVar < FinalValue
348 if (&IndVar == LatchCmpOp0 || &IndVar == LatchCmpOp1)
349 return &IndVar;
350 }
351
352 return nullptr;
353}
354
355bool Loop::getInductionDescriptor(ScalarEvolution &SE,
356 InductionDescriptor &IndDesc) const {
357 if (PHINode *IndVar = getInductionVariable(SE))
358 return InductionDescriptor::isInductionPHI(Phi: IndVar, L: this, SE: &SE, D&: IndDesc);
359
360 return false;
361}
362
363bool Loop::isAuxiliaryInductionVariable(PHINode &AuxIndVar,
364 ScalarEvolution &SE) const {
365 // Located in the loop header
366 BasicBlock *Header = getHeader();
367 if (AuxIndVar.getParent() != Header)
368 return false;
369
370 // No uses outside of the loop
371 for (User *U : AuxIndVar.users())
372 if (const Instruction *I = dyn_cast<Instruction>(Val: U))
373 if (!contains(Inst: I))
374 return false;
375
376 InductionDescriptor IndDesc;
377 if (!InductionDescriptor::isInductionPHI(Phi: &AuxIndVar, L: this, SE: &SE, D&: IndDesc))
378 return false;
379
380 // The step instruction opcode should be add or sub.
381 if (IndDesc.getInductionOpcode() != Instruction::Add &&
382 IndDesc.getInductionOpcode() != Instruction::Sub)
383 return false;
384
385 // Incremented by a loop invariant step for each loop iteration
386 return SE.isLoopInvariant(S: IndDesc.getStep(), L: this);
387}
388
389CondBrInst *Loop::getLoopGuardBranch() const {
390 if (!isLoopSimplifyForm())
391 return nullptr;
392
393 BasicBlock *Preheader = getLoopPreheader();
394 assert(Preheader && getLoopLatch() &&
395 "Expecting a loop with valid preheader and latch");
396
397 // Loop should be in rotate form.
398 if (!isRotatedForm())
399 return nullptr;
400
401 // Disallow loops with more than one unique exit block, as we do not verify
402 // that GuardOtherSucc post dominates all exit blocks.
403 BasicBlock *ExitFromLatch = getUniqueExitBlock();
404 if (!ExitFromLatch)
405 return nullptr;
406
407 BasicBlock *GuardBB = Preheader->getUniquePredecessor();
408 if (!GuardBB)
409 return nullptr;
410
411 assert(GuardBB->getTerminator() && "Expecting valid guard terminator");
412
413 CondBrInst *GuardBI = dyn_cast<CondBrInst>(Val: GuardBB->getTerminator());
414 if (!GuardBI)
415 return nullptr;
416
417 BasicBlock *GuardOtherSucc = (GuardBI->getSuccessor(i: 0) == Preheader)
418 ? GuardBI->getSuccessor(i: 1)
419 : GuardBI->getSuccessor(i: 0);
420
421 // Check if ExitFromLatch (or any BasicBlock which is an empty unique
422 // successor of ExitFromLatch) is equal to GuardOtherSucc. If
423 // skipEmptyBlockUntil returns GuardOtherSucc, then the guard branch for the
424 // loop is GuardBI (return GuardBI), otherwise return nullptr.
425 if (&LoopNest::skipEmptyBlockUntil(From: ExitFromLatch, End: GuardOtherSucc,
426 /*CheckUniquePred=*/true) ==
427 GuardOtherSucc)
428 return GuardBI;
429 else
430 return nullptr;
431}
432
433bool Loop::isCanonical(ScalarEvolution &SE) const {
434 InductionDescriptor IndDesc;
435 if (!getInductionDescriptor(SE, IndDesc))
436 return false;
437
438 ConstantInt *Init = dyn_cast_or_null<ConstantInt>(Val: IndDesc.getStartValue());
439 if (!Init || !Init->isZero())
440 return false;
441
442 if (IndDesc.getInductionOpcode() != Instruction::Add)
443 return false;
444
445 ConstantInt *Step = IndDesc.getConstIntStepValue();
446 if (!Step || !Step->isOne())
447 return false;
448
449 return true;
450}
451
452// Check whether the use \p U of a value defined in block \p BB (which is part
453// of loop \p L) does not require a live-out phi, i.e. whether it is contained
454// in the loop for LCSSA purposes.
455static bool loopContainsUser(const Loop &L, const BasicBlock &BB, const Use &U,
456 const DominatorTree &DT) {
457 const Instruction *UI = cast<Instruction>(Val: U.getUser());
458 const BasicBlock *UserBB = UI->getParent();
459
460 // For practical purposes, we consider that the use in a PHI
461 // occurs in the respective predecessor block. For more info,
462 // see the `phi` doc in LangRef and the LCSSA doc.
463 if (const PHINode *P = dyn_cast<PHINode>(Val: UI))
464 UserBB = P->getIncomingBlock(U);
465
466 // Check the current block, as a fast-path, before checking whether
467 // the use is anywhere in the loop. Most values are used in the same
468 // block they are defined in. Also, blocks not reachable from the
469 // entry are special; uses in them don't need to go through PHIs.
470 if (UserBB != &BB && !L.contains(BB: UserBB) && DT.isReachableFromEntry(A: UserBB))
471 return false;
472
473 return true;
474}
475
476// Check that 'BB' doesn't have any uses outside of the 'L'
477static bool isBlockInLCSSAForm(const Loop &L, const BasicBlock &BB,
478 const DominatorTree &DT, bool IgnoreTokens) {
479 for (const Instruction &I : BB) {
480 // Token-like values can't be used in PHI nodes and live-out token-like
481 // values prevent loop optimizations, so for the purposes of considered
482 // LCSSA form, we can ignore them.
483 if (IgnoreTokens && I.getType()->isTokenLikeTy())
484 continue;
485
486 for (const Use &U : I.uses()) {
487 if (!loopContainsUser(L, BB, U, DT))
488 return false;
489 }
490 }
491 return true;
492}
493
494bool Loop::isLCSSAForm(const DominatorTree &DT, bool IgnoreTokens) const {
495 // For each block we check that it doesn't have any uses outside of this loop.
496 return all_of(Range: this->blocks(), P: [&](const BasicBlock *BB) {
497 return isBlockInLCSSAForm(L: *this, BB: *BB, DT, IgnoreTokens);
498 });
499}
500
501bool Loop::isRecursivelyLCSSAForm(const DominatorTree &DT, const LoopInfo &LI,
502 bool IgnoreTokens) const {
503 // For each block we check that it doesn't have any uses outside of its
504 // innermost loop. This process will transitively guarantee that the current
505 // loop and all of the nested loops are in LCSSA form.
506 return all_of(Range: this->blocks(), P: [&](const BasicBlock *BB) {
507 return isBlockInLCSSAForm(L: *LI.getLoopFor(BB), BB: *BB, DT, IgnoreTokens);
508 });
509}
510
511bool Loop::isLoopSimplifyForm() const {
512 // Normal-form loops have a preheader, a single backedge, and all of their
513 // exits have all their predecessors inside the loop.
514 return getLoopPreheader() && getLoopLatch() && hasDedicatedExits();
515}
516
517// Routines that reform the loop CFG and split edges often fail on indirectbr.
518bool Loop::isSafeToClone() const {
519 // Return false if any loop blocks contain indirectbrs, or there are any calls
520 // to noduplicate functions.
521 for (BasicBlock *BB : this->blocks()) {
522 if (isa<IndirectBrInst>(Val: BB->getTerminator()))
523 return false;
524
525 for (Instruction &I : *BB)
526 if (auto *CB = dyn_cast<CallBase>(Val: &I))
527 if (CB->cannotDuplicate())
528 return false;
529 }
530 return true;
531}
532
533MDNode *Loop::getLoopID() const {
534 MDNode *LoopID = nullptr;
535
536 // Go through the latch blocks and check the terminator for the metadata.
537 SmallVector<BasicBlock *, 4> LatchesBlocks;
538 getLoopLatches(LoopLatches&: LatchesBlocks);
539 for (BasicBlock *BB : LatchesBlocks) {
540 Instruction *TI = BB->getTerminator();
541 MDNode *MD = TI->getMetadata(KindID: LLVMContext::MD_loop);
542
543 if (!MD)
544 return nullptr;
545
546 if (!LoopID)
547 LoopID = MD;
548 else if (MD != LoopID)
549 return nullptr;
550 }
551 if (!LoopID || LoopID->getNumOperands() == 0 ||
552 LoopID->getOperand(I: 0) != LoopID)
553 return nullptr;
554 return LoopID;
555}
556
557void Loop::setLoopID(MDNode *LoopID) const {
558 assert((!LoopID || LoopID->getNumOperands() > 0) &&
559 "Loop ID needs at least one operand");
560 assert((!LoopID || LoopID->getOperand(0) == LoopID) &&
561 "Loop ID should refer to itself");
562
563 SmallVector<BasicBlock *, 4> LoopLatches;
564 getLoopLatches(LoopLatches);
565 for (BasicBlock *BB : LoopLatches)
566 BB->getTerminator()->setMetadata(KindID: LLVMContext::MD_loop, Node: LoopID);
567}
568
569void Loop::setLoopAlreadyUnrolled() {
570 addStringLoopAttribute(Name: "llvm.loop.unroll.disable", RemovePrefixes: {"llvm.loop.unroll."});
571}
572
573void Loop::setLoopMustProgress() {
574 if (findOptionMDForLoop(TheLoop: this, Name: "llvm.loop.mustprogress"))
575 return;
576 addStringLoopAttribute(Name: "llvm.loop.mustprogress");
577}
578
579void Loop::addStringLoopAttribute(StringRef Name,
580 ArrayRef<StringRef> RemovePrefixes) const {
581 LLVMContext &Context = getHeader()->getContext();
582 MDNode *AttrMD = MDNode::get(Context, MDs: MDString::get(Context, Str: Name));
583 MDNode *LoopID = getLoopID();
584 MDNode *NewLoopID =
585 makePostTransformationMetadata(Context, OrigLoopID: LoopID, RemovePrefixes, AddAttrs: {AttrMD});
586 setLoopID(NewLoopID);
587}
588
589void Loop::addIntLoopAttribute(StringRef Name, unsigned Value,
590 ArrayRef<StringRef> RemovePrefixes) const {
591 LLVMContext &Context = getHeader()->getContext();
592 MDNode *AttrMD = MDNode::get(
593 Context,
594 MDs: {MDString::get(Context, Str: Name),
595 ConstantAsMetadata::get(C: ConstantInt::get(Context, V: APInt(32, Value)))});
596 MDNode *LoopID = getLoopID();
597 MDNode *NewLoopID =
598 makePostTransformationMetadata(Context, OrigLoopID: LoopID, RemovePrefixes, AddAttrs: {AttrMD});
599 setLoopID(NewLoopID);
600}
601
602bool Loop::isAnnotatedParallel() const {
603 MDNode *DesiredLoopIdMetadata = getLoopID();
604
605 if (!DesiredLoopIdMetadata)
606 return false;
607
608 MDNode *ParallelAccesses =
609 findOptionMDForLoop(TheLoop: this, Name: "llvm.loop.parallel_accesses");
610 SmallPtrSet<MDNode *, 4>
611 ParallelAccessGroups; // For scalable 'contains' check.
612 if (ParallelAccesses) {
613 for (const MDOperand &MD : drop_begin(RangeOrContainer: ParallelAccesses->operands())) {
614 MDNode *AccGroup = cast<MDNode>(Val: MD.get());
615 assert(isValidAsAccessGroup(AccGroup) &&
616 "List item must be an access group");
617 ParallelAccessGroups.insert(Ptr: AccGroup);
618 }
619 }
620
621 // The loop branch contains the parallel loop metadata. In order to ensure
622 // that any parallel-loop-unaware optimization pass hasn't added loop-carried
623 // dependencies (thus converted the loop back to a sequential loop), check
624 // that all the memory instructions in the loop belong to an access group that
625 // is parallel to this loop.
626 for (BasicBlock *BB : this->blocks()) {
627 for (Instruction &I : *BB) {
628 if (!I.mayReadOrWriteMemory())
629 continue;
630
631 if (MDNode *AccessGroup = I.getMetadata(KindID: LLVMContext::MD_access_group)) {
632 auto ContainsAccessGroup = [&ParallelAccessGroups](MDNode *AG) -> bool {
633 if (AG->getNumOperands() == 0) {
634 assert(isValidAsAccessGroup(AG) && "Item must be an access group");
635 return ParallelAccessGroups.count(Ptr: AG);
636 }
637
638 for (const MDOperand &AccessListItem : AG->operands()) {
639 MDNode *AccGroup = cast<MDNode>(Val: AccessListItem.get());
640 assert(isValidAsAccessGroup(AccGroup) &&
641 "List item must be an access group");
642 if (ParallelAccessGroups.count(Ptr: AccGroup))
643 return true;
644 }
645 return false;
646 };
647
648 if (ContainsAccessGroup(AccessGroup))
649 continue;
650 }
651
652 // The memory instruction can refer to the loop identifier metadata
653 // directly or indirectly through another list metadata (in case of
654 // nested parallel loops). The loop identifier metadata refers to
655 // itself so we can check both cases with the same routine.
656 MDNode *LoopIdMD =
657 I.getMetadata(KindID: LLVMContext::MD_mem_parallel_loop_access);
658
659 if (!LoopIdMD)
660 return false;
661
662 if (!llvm::is_contained(Range: LoopIdMD->operands(), Element: DesiredLoopIdMetadata))
663 return false;
664 }
665 }
666 return true;
667}
668
669DebugLoc Loop::getStartLoc() const { return getLocRange().getStart(); }
670
671Loop::LocRange Loop::getLocRange() const {
672 // If we have a debug location in the loop ID, then use it.
673 if (MDNode *LoopID = getLoopID()) {
674 DebugLoc Start;
675 // We use the first DebugLoc in the header as the start location of the loop
676 // and if there is a second DebugLoc in the header we use it as end location
677 // of the loop.
678 for (const MDOperand &MDO : llvm::drop_begin(RangeOrContainer: LoopID->operands())) {
679 if (DILocation *L = dyn_cast<DILocation>(Val: MDO)) {
680 if (!Start)
681 Start = DebugLoc(L);
682 else
683 return LocRange(Start, DebugLoc(L));
684 }
685 }
686
687 if (Start)
688 return LocRange(Start);
689 }
690
691 // Try the pre-header first.
692 if (BasicBlock *PHeadBB = getLoopPreheader())
693 if (DebugLoc DL = PHeadBB->getTerminator()->getDebugLoc())
694 return LocRange(DL);
695
696 // If we have no pre-header or there are no instructions with debug
697 // info in it, try the header.
698 if (BasicBlock *HeadBB = getHeader())
699 return LocRange(HeadBB->getTerminator()->getDebugLoc());
700
701 return LocRange();
702}
703
704std::string Loop::getLocStr() const {
705 std::string Result;
706 raw_string_ostream OS(Result);
707 if (const DebugLoc LoopDbgLoc = getStartLoc())
708 LoopDbgLoc.print(OS);
709 else
710 // Just print the module name.
711 OS << getHeader()->getParent()->getParent()->getModuleIdentifier();
712 return Result;
713}
714
715#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
716LLVM_DUMP_METHOD void Loop::dump() const { print(dbgs()); }
717
718LLVM_DUMP_METHOD void Loop::dumpVerbose() const {
719 print(dbgs(), /*Verbose=*/true);
720}
721#endif
722
723//===----------------------------------------------------------------------===//
724// UnloopUpdater implementation
725//
726
727namespace {
728/// Find the new parent loop for all blocks within the "unloop" whose last
729/// backedges has just been removed.
730class UnloopUpdater {
731 Loop &Unloop;
732 LoopInfo *LI;
733
734 LoopBlocksDFS DFS;
735
736 // Map unloop's immediate subloops to their nearest reachable parents. Nested
737 // loops within these subloops will not change parents. However, an immediate
738 // subloop's new parent will be the nearest loop reachable from either its own
739 // exits *or* any of its nested loop's exits.
740 DenseMap<Loop *, Loop *> SubloopParents;
741
742 // Flag the presence of an irreducible backedge whose destination is a block
743 // directly contained by the original unloop.
744 bool FoundIB = false;
745
746public:
747 UnloopUpdater(Loop *UL, LoopInfo *LInfo) : Unloop(*UL), LI(LInfo), DFS(UL) {}
748
749 void updateBlockParents();
750
751 void removeBlocksFromAncestors();
752
753 void updateSubloopParents();
754
755protected:
756 Loop *getNearestLoop(BasicBlock *BB, Loop *BBLoop);
757};
758} // end anonymous namespace
759
760/// Update the parent loop for all blocks that are directly contained within the
761/// original "unloop".
762void UnloopUpdater::updateBlockParents() {
763 if (Unloop.getNumBlocks()) {
764 // Perform a post order CFG traversal of all blocks within this loop,
765 // propagating the nearest loop from successors to predecessors.
766 LoopBlocksTraversal Traversal(DFS, LI);
767 for (BasicBlock *POI : Traversal) {
768
769 Loop *L = LI->getLoopFor(BB: POI);
770 Loop *NL = getNearestLoop(BB: POI, BBLoop: L);
771
772 if (NL != L) {
773 // For reducible loops, NL is now an ancestor of Unloop.
774 assert((NL != &Unloop && (!NL || NL->contains(&Unloop))) &&
775 "uninitialized successor");
776 LI->changeLoopFor(BB: POI, L: NL);
777 } else {
778 // Or the current block is part of a subloop, in which case its parent
779 // is unchanged.
780 assert((FoundIB || Unloop.contains(L)) && "uninitialized successor");
781 }
782 }
783 }
784 // Each irreducible loop within the unloop induces a round of iteration using
785 // the DFS result cached by Traversal.
786 bool Changed = FoundIB;
787 for (unsigned NIters = 0; Changed; ++NIters) {
788 assert(NIters < Unloop.getNumBlocks() && "runaway iterative algorithm");
789 (void)NIters;
790
791 // Iterate over the postorder list of blocks, propagating the nearest loop
792 // from successors to predecessors as before.
793 Changed = false;
794 for (LoopBlocksDFS::POIterator POI = DFS.beginPostorder(),
795 POE = DFS.endPostorder();
796 POI != POE; ++POI) {
797
798 Loop *L = LI->getLoopFor(BB: *POI);
799 Loop *NL = getNearestLoop(BB: *POI, BBLoop: L);
800 if (NL != L) {
801 assert(NL != &Unloop && (!NL || NL->contains(&Unloop)) &&
802 "uninitialized successor");
803 LI->changeLoopFor(BB: *POI, L: NL);
804 Changed = true;
805 }
806 }
807 }
808}
809
810/// Remove unloop's blocks from all ancestors below their new parents.
811void UnloopUpdater::removeBlocksFromAncestors() {
812 // Remove all unloop's blocks (including those in nested subloops) from
813 // ancestors below the new parent loop.
814 for (BasicBlock *BB : Unloop.blocks()) {
815 Loop *OuterParent = LI->getLoopFor(BB);
816 if (Unloop.contains(L: OuterParent)) {
817 while (OuterParent->getParentLoop() != &Unloop)
818 OuterParent = OuterParent->getParentLoop();
819 OuterParent = SubloopParents[OuterParent];
820 }
821 // Remove blocks from former Ancestors except Unloop itself which will be
822 // deleted.
823 for (Loop *OldParent = Unloop.getParentLoop(); OldParent != OuterParent;
824 OldParent = OldParent->getParentLoop()) {
825 assert(OldParent && "new loop is not an ancestor of the original");
826 OldParent->removeBlockFromLoop(BB);
827 }
828 }
829}
830
831/// Update the parent loop for all subloops directly nested within unloop.
832void UnloopUpdater::updateSubloopParents() {
833 while (!Unloop.isInnermost()) {
834 Loop *Subloop = *std::prev(x: Unloop.end());
835 Unloop.removeChildLoop(I: std::prev(x: Unloop.end()));
836
837 assert(SubloopParents.count(Subloop) && "DFS failed to visit subloop");
838 if (Loop *Parent = SubloopParents[Subloop])
839 Parent->addChildLoop(NewChild: Subloop);
840 else
841 LI->addTopLevelLoop(New: Subloop);
842 }
843}
844
845/// Return the nearest parent loop among this block's successors. If a successor
846/// is a subloop header, consider its parent to be the nearest parent of the
847/// subloop's exits.
848///
849/// For subloop blocks, simply update SubloopParents and return NULL.
850Loop *UnloopUpdater::getNearestLoop(BasicBlock *BB, Loop *BBLoop) {
851
852 // Initially for blocks directly contained by Unloop, NearLoop == Unloop and
853 // is considered uninitialized.
854 Loop *NearLoop = BBLoop;
855
856 Loop *Subloop = nullptr;
857 if (NearLoop != &Unloop && Unloop.contains(L: NearLoop)) {
858 Subloop = NearLoop;
859 // Find the subloop ancestor that is directly contained within Unloop.
860 while (Subloop->getParentLoop() != &Unloop) {
861 Subloop = Subloop->getParentLoop();
862 assert(Subloop && "subloop is not an ancestor of the original loop");
863 }
864 // Get the current nearest parent of the Subloop exits, initially Unloop.
865 NearLoop = SubloopParents.insert(KV: {Subloop, &Unloop}).first->second;
866 }
867
868 if (succ_empty(BB)) {
869 assert(!Subloop && "subloop blocks must have a successor");
870 NearLoop = nullptr; // unloop blocks may now exit the function.
871 }
872 for (BasicBlock *Succ : successors(BB)) {
873 if (Succ == BB)
874 continue; // self loops are uninteresting
875
876 Loop *L = LI->getLoopFor(BB: Succ);
877 if (L == &Unloop) {
878 // This successor has not been processed. This path must lead to an
879 // irreducible backedge.
880 assert((FoundIB || !DFS.hasPostorder(Succ)) && "should have seen IB");
881 FoundIB = true;
882 }
883 if (L != &Unloop && Unloop.contains(L)) {
884 // Successor is in a subloop.
885 if (Subloop)
886 continue; // Branching within subloops. Ignore it.
887
888 // BB branches from the original into a subloop header.
889 assert(L->getParentLoop() == &Unloop && "cannot skip into nested loops");
890
891 // Get the current nearest parent of the Subloop's exits.
892 L = SubloopParents[L];
893 // L could be Unloop if the only exit was an irreducible backedge.
894 }
895 if (L == &Unloop) {
896 continue;
897 }
898 // Handle critical edges from Unloop into a sibling loop.
899 if (L && !L->contains(L: &Unloop)) {
900 L = L->getParentLoop();
901 }
902 // Remember the nearest parent loop among successors or subloop exits.
903 if (NearLoop == &Unloop || !NearLoop || NearLoop->contains(L))
904 NearLoop = L;
905 }
906 if (Subloop) {
907 SubloopParents[Subloop] = NearLoop;
908 return BBLoop;
909 }
910 return NearLoop;
911}
912
913LoopInfo::LoopInfo(const DomTreeBase<BasicBlock> &DomTree) { analyze(DomTree); }
914
915bool LoopInfo::invalidate(Function &F, const PreservedAnalyses &PA,
916 FunctionAnalysisManager::Invalidator &) {
917 // Check whether the analysis, all analyses on functions, or the function's
918 // CFG have been preserved.
919 auto PAC = PA.getChecker<LoopAnalysis>();
920 return !(PAC.preserved() || PAC.preservedSet<AllAnalysesOn<Function>>() ||
921 PAC.preservedSet<CFGAnalyses>());
922}
923
924void LoopInfo::erase(Loop *Unloop) {
925 assert(!Unloop->isInvalid() && "Loop has already been erased!");
926
927 llvm::scope_exit InvalidateOnExit([&]() { destroy(L: Unloop); });
928
929 // First handle the special case of no parent loop to simplify the algorithm.
930 if (Unloop->isOutermost()) {
931 // Since BBLoop had no parent, Unloop blocks are no longer in a loop.
932 for (BasicBlock *BB : Unloop->blocks()) {
933 // Don't reparent blocks in subloops.
934 if (getLoopFor(BB) != Unloop)
935 continue;
936
937 // Blocks no longer have a parent but are still referenced by Unloop until
938 // the Unloop object is deleted.
939 changeLoopFor(BB, L: nullptr);
940 }
941
942 // Remove the loop from the top-level LoopInfo object.
943 for (iterator I = begin();; ++I) {
944 assert(I != end() && "Couldn't find loop");
945 if (*I == Unloop) {
946 removeLoop(I);
947 break;
948 }
949 }
950
951 // Move all of the subloops to the top-level.
952 while (!Unloop->isInnermost())
953 addTopLevelLoop(New: Unloop->removeChildLoop(I: std::prev(x: Unloop->end())));
954
955 return;
956 }
957
958 // Update the parent loop for all blocks within the loop. Blocks within
959 // subloops will not change parents.
960 UnloopUpdater Updater(Unloop, this);
961 Updater.updateBlockParents();
962
963 // Remove blocks from former ancestor loops.
964 Updater.removeBlocksFromAncestors();
965
966 // Add direct subloops as children in their new parent loop.
967 Updater.updateSubloopParents();
968
969 // Remove unloop from its parent loop.
970 Loop *ParentLoop = Unloop->getParentLoop();
971 for (Loop::iterator I = ParentLoop->begin();; ++I) {
972 assert(I != ParentLoop->end() && "Couldn't find loop");
973 if (*I == Unloop) {
974 ParentLoop->removeChildLoop(I);
975 break;
976 }
977 }
978}
979
980bool LoopInfo::wouldBeOutOfLoopUseRequiringLCSSA(
981 const Value *V, const BasicBlock *ExitBB) const {
982 if (V->getType()->isTokenLikeTy())
983 // We can't form PHIs of token-like type, so the definition of LCSSA
984 // excludes values of that type.
985 return false;
986
987 const Instruction *I = dyn_cast<Instruction>(Val: V);
988 if (!I)
989 return false;
990 const Loop *L = getLoopFor(BB: I->getParent());
991 if (!L)
992 return false;
993 if (L->contains(BB: ExitBB))
994 // Could be an exit bb of a subloop and contained in defining loop
995 return false;
996
997 // We found a (new) out-of-loop use location, for a value defined in-loop.
998 // (Note that because of LCSSA, we don't have to account for values defined
999 // in sibling loops. Such values will have LCSSA phis of their own in the
1000 // common parent loop.)
1001 return true;
1002}
1003
1004AnalysisKey LoopAnalysis::Key;
1005
1006LoopInfo LoopAnalysis::run(Function &F, FunctionAnalysisManager &AM) {
1007 // FIXME: Currently we create a LoopInfo from scratch for every function.
1008 // This may prove to be too wasteful due to deallocating and re-allocating
1009 // memory each time for the underlying map and vector datastructures. At some
1010 // point it may prove worthwhile to use a freelist and recycle LoopInfo
1011 // objects. I don't want to add that kind of complexity until the scope of
1012 // the problem is better understood.
1013 LoopInfo LI;
1014 LI.analyze(DomTree: AM.getResult<DominatorTreeAnalysis>(IR&: F));
1015 return LI;
1016}
1017
1018PreservedAnalyses LoopPrinterPass::run(Function &F,
1019 FunctionAnalysisManager &AM) {
1020 auto &LI = AM.getResult<LoopAnalysis>(IR&: F);
1021 OS << "Loop info for function '" << F.getName() << "':\n";
1022 LI.print(OS);
1023 return PreservedAnalyses::all();
1024}
1025
1026void llvm::printLoop(const Loop &L, raw_ostream &OS,
1027 const std::string &Banner) {
1028 if (forcePrintModuleIR()) {
1029 // handling -print-module-scope
1030 OS << Banner << " (loop: ";
1031 L.getHeader()->printAsOperand(O&: OS, PrintType: false);
1032 OS << ")\n";
1033
1034 // printing whole module
1035 OS << *L.getHeader()->getModule();
1036 return;
1037 }
1038
1039 if (forcePrintFuncIR()) {
1040 // handling -print-loop-func-scope.
1041 // -print-module-scope overrides this.
1042 OS << Banner << " (loop: ";
1043 L.getHeader()->printAsOperand(O&: OS, PrintType: false);
1044 OS << ")\n";
1045
1046 // printing whole function.
1047 OS << *L.getHeader()->getParent();
1048 return;
1049 }
1050
1051 OS << Banner;
1052
1053 auto *PreHeader = L.getLoopPreheader();
1054 if (PreHeader) {
1055 OS << "\n; Preheader:";
1056 PreHeader->print(OS);
1057 OS << "\n; Loop:";
1058 }
1059
1060 for (auto *Block : L.blocks())
1061 if (Block)
1062 Block->print(OS);
1063 else
1064 OS << "Printing <null> block";
1065
1066 SmallVector<BasicBlock *, 8> ExitBlocks;
1067 L.getExitBlocks(ExitBlocks);
1068 if (!ExitBlocks.empty()) {
1069 OS << "\n; Exit blocks";
1070 for (auto *Block : ExitBlocks)
1071 if (Block)
1072 Block->print(OS);
1073 else
1074 OS << "Printing <null> block";
1075 }
1076}
1077
1078MDNode *llvm::findOptionMDForLoopID(MDNode *LoopID, StringRef Name) {
1079 // No loop metadata node, no loop properties.
1080 if (!LoopID)
1081 return nullptr;
1082
1083 // First operand should refer to the metadata node itself, for legacy reasons.
1084 assert(LoopID->getNumOperands() > 0 && "requires at least one operand");
1085 assert(LoopID->getOperand(0) == LoopID && "invalid loop id");
1086
1087 // Iterate over the metdata node operands and look for MDString metadata.
1088 for (const MDOperand &MDO : llvm::drop_begin(RangeOrContainer: LoopID->operands())) {
1089 MDNode *MD = dyn_cast<MDNode>(Val: MDO);
1090 if (!MD || MD->getNumOperands() < 1)
1091 continue;
1092 MDString *S = dyn_cast<MDString>(Val: MD->getOperand(I: 0));
1093 if (!S)
1094 continue;
1095 // Return the operand node if MDString holds expected metadata.
1096 if (Name == S->getString())
1097 return MD;
1098 }
1099
1100 // Loop property not found.
1101 return nullptr;
1102}
1103
1104MDNode *llvm::findOptionMDForLoop(const Loop *TheLoop, StringRef Name) {
1105 return findOptionMDForLoopID(LoopID: TheLoop->getLoopID(), Name);
1106}
1107
1108/// Find string metadata for loop
1109///
1110/// If it has a value (e.g. {"llvm.distribute", 1} return the value as an
1111/// operand or null otherwise. If the string metadata is not found return
1112/// Optional's not-a-value.
1113std::optional<const MDOperand *>
1114llvm::findStringMetadataForLoop(const Loop *TheLoop, StringRef Name) {
1115 MDNode *MD = findOptionMDForLoop(TheLoop, Name);
1116 if (!MD)
1117 return std::nullopt;
1118 switch (MD->getNumOperands()) {
1119 case 1:
1120 return nullptr;
1121 case 2:
1122 return &MD->getOperand(I: 1);
1123 default:
1124 llvm_unreachable("loop metadata has 0 or 1 operand");
1125 }
1126}
1127
1128std::optional<bool> llvm::getOptionalBoolLoopAttribute(const Loop *TheLoop,
1129 StringRef Name) {
1130 MDNode *MD = findOptionMDForLoop(TheLoop, Name);
1131 if (!MD)
1132 return std::nullopt;
1133 switch (MD->getNumOperands()) {
1134 case 1:
1135 // When the value is absent it is interpreted as 'attribute set'.
1136 return true;
1137 case 2:
1138 if (ConstantInt *IntMD =
1139 mdconst::extract_or_null<ConstantInt>(MD: MD->getOperand(I: 1).get()))
1140 return IntMD->getZExtValue();
1141 return true;
1142 }
1143 llvm_unreachable("unexpected number of options");
1144}
1145
1146bool llvm::getBooleanLoopAttribute(const Loop *TheLoop, StringRef Name) {
1147 return getOptionalBoolLoopAttribute(TheLoop, Name).value_or(u: false);
1148}
1149
1150std::optional<int> llvm::getOptionalIntLoopAttribute(const Loop *TheLoop,
1151 StringRef Name) {
1152 const MDOperand *AttrMD =
1153 findStringMetadataForLoop(TheLoop, Name).value_or(u: nullptr);
1154 if (!AttrMD)
1155 return std::nullopt;
1156
1157 ConstantInt *IntMD = mdconst::extract_or_null<ConstantInt>(MD: AttrMD->get());
1158 if (!IntMD)
1159 return std::nullopt;
1160
1161 return IntMD->getSExtValue();
1162}
1163
1164int llvm::getIntLoopAttribute(const Loop *TheLoop, StringRef Name,
1165 int Default) {
1166 return getOptionalIntLoopAttribute(TheLoop, Name).value_or(u&: Default);
1167}
1168
1169CallBase *llvm::getLoopConvergenceHeart(const Loop *TheLoop) {
1170 BasicBlock *H = TheLoop->getHeader();
1171 for (Instruction &II : *H) {
1172 if (auto *CB = dyn_cast<CallBase>(Val: &II)) {
1173 if (!CB->isConvergent())
1174 continue;
1175 // This is the heart if it uses a token defined outside the loop. The
1176 // verifier has already checked that only the loop intrinsic can use such
1177 // a token.
1178 if (auto *Token = CB->getConvergenceControlToken()) {
1179 auto *TokenDef = cast<Instruction>(Val: Token);
1180 if (!TheLoop->contains(BB: TokenDef->getParent()))
1181 return CB;
1182 }
1183 return nullptr;
1184 }
1185 }
1186 return nullptr;
1187}
1188
1189bool llvm::isFinite(const Loop *L) {
1190 return L->getHeader()->getParent()->willReturn();
1191}
1192
1193static const char *LLVMLoopMustProgress = "llvm.loop.mustprogress";
1194
1195bool llvm::hasMustProgress(const Loop *L) {
1196 return getBooleanLoopAttribute(TheLoop: L, Name: LLVMLoopMustProgress);
1197}
1198
1199bool llvm::isMustProgress(const Loop *L) {
1200 return L->getHeader()->getParent()->mustProgress() || hasMustProgress(L);
1201}
1202
1203bool llvm::isValidAsAccessGroup(MDNode *Node) {
1204 return Node->getNumOperands() == 0 && Node->isDistinct();
1205}
1206
1207MDNode *llvm::makePostTransformationMetadata(LLVMContext &Context,
1208 MDNode *OrigLoopID,
1209 ArrayRef<StringRef> RemovePrefixes,
1210 ArrayRef<MDNode *> AddAttrs) {
1211 // First remove any existing loop metadata related to this transformation.
1212 SmallVector<Metadata *, 4> MDs;
1213
1214 // Reserve first location for self reference to the LoopID metadata node.
1215 MDs.push_back(Elt: nullptr);
1216
1217 // Remove metadata for the transformation that has been applied or that became
1218 // outdated.
1219 if (OrigLoopID) {
1220 for (const MDOperand &MDO : llvm::drop_begin(RangeOrContainer: OrigLoopID->operands())) {
1221 bool IsVectorMetadata = false;
1222 Metadata *Op = MDO;
1223 if (MDNode *MD = dyn_cast<MDNode>(Val: Op)) {
1224 const MDString *S = dyn_cast<MDString>(Val: MD->getOperand(I: 0));
1225 if (S)
1226 IsVectorMetadata =
1227 llvm::any_of(Range&: RemovePrefixes, P: [S](StringRef Prefix) -> bool {
1228 return S->getString().starts_with(Prefix);
1229 });
1230 }
1231 if (!IsVectorMetadata)
1232 MDs.push_back(Elt: Op);
1233 }
1234 }
1235
1236 // Add metadata to avoid reapplying a transformation, such as
1237 // llvm.loop.unroll.disable and llvm.loop.isvectorized.
1238 MDs.append(in_start: AddAttrs.begin(), in_end: AddAttrs.end());
1239
1240 MDNode *NewLoopID = MDNode::getDistinct(Context, MDs);
1241 // Replace the temporary node with a self-reference.
1242 NewLoopID->replaceOperandWith(I: 0, New: NewLoopID);
1243 return NewLoopID;
1244}
1245
1246//===----------------------------------------------------------------------===//
1247// LoopInfo implementation
1248//
1249
1250LoopInfoWrapperPass::LoopInfoWrapperPass() : FunctionPass(ID) {}
1251
1252char LoopInfoWrapperPass::ID = 0;
1253INITIALIZE_PASS_BEGIN(LoopInfoWrapperPass, "loops", "Natural Loop Information",
1254 true, true)
1255INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
1256INITIALIZE_PASS_END(LoopInfoWrapperPass, "loops", "Natural Loop Information",
1257 true, true)
1258
1259bool LoopInfoWrapperPass::runOnFunction(Function &) {
1260 releaseMemory();
1261 LI.analyze(DomTree: getAnalysis<DominatorTreeWrapperPass>().getDomTree());
1262 return false;
1263}
1264
1265void LoopInfoWrapperPass::verifyAnalysis() const {
1266 // LoopInfoWrapperPass is a FunctionPass, but verifying every loop in the
1267 // function each time verifyAnalysis is called is very expensive. The
1268 // -verify-loop-info option can enable this. In order to perform some
1269 // checking by default, LoopPass has been taught to call verifyLoop manually
1270 // during loop pass sequences.
1271 if (VerifyLoopInfo) {
1272 auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
1273 LI.verify(DomTree: DT);
1274 }
1275}
1276
1277void LoopInfoWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
1278 AU.setPreservesAll();
1279 AU.addRequiredTransitive<DominatorTreeWrapperPass>();
1280}
1281
1282void LoopInfoWrapperPass::print(raw_ostream &OS, const Module *) const {
1283 LI.print(OS);
1284}
1285
1286PreservedAnalyses LoopVerifierPass::run(Function &F,
1287 FunctionAnalysisManager &AM) {
1288 LoopInfo &LI = AM.getResult<LoopAnalysis>(IR&: F);
1289 auto &DT = AM.getResult<DominatorTreeAnalysis>(IR&: F);
1290 LI.verify(DomTree: DT);
1291 return PreservedAnalyses::all();
1292}
1293
1294//===----------------------------------------------------------------------===//
1295// LoopBlocksDFS implementation
1296//
1297
1298/// Traverse the loop blocks and store the DFS result.
1299/// Useful for clients that just want the final DFS result and don't need to
1300/// visit blocks during the initial traversal.
1301void LoopBlocksDFS::perform(const LoopInfo *LI) {
1302 LoopBlocksTraversal Traversal(*this, LI);
1303 for ([[maybe_unused]] BasicBlock *BB : Traversal)
1304 ;
1305}
1306