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 that 'BB' doesn't have any uses outside of the 'L'
453static bool isBlockInLCSSAForm(const Loop &L, const BasicBlock &BB,
454 const DominatorTree &DT, bool IgnoreTokens) {
455 for (const Instruction &I : BB) {
456 // Tokens can't be used in PHI nodes and live-out tokens prevent loop
457 // optimizations, so for the purposes of considered LCSSA form, we
458 // can ignore them.
459 if (IgnoreTokens && I.getType()->isTokenTy())
460 continue;
461
462 for (const Use &U : I.uses()) {
463 const Instruction *UI = cast<Instruction>(Val: U.getUser());
464 const BasicBlock *UserBB = UI->getParent();
465
466 // For practical purposes, we consider that the use in a PHI
467 // occurs in the respective predecessor block. For more info,
468 // see the `phi` doc in LangRef and the LCSSA doc.
469 if (const PHINode *P = dyn_cast<PHINode>(Val: UI))
470 UserBB = P->getIncomingBlock(U);
471
472 // Check the current block, as a fast-path, before checking whether
473 // the use is anywhere in the loop. Most values are used in the same
474 // block they are defined in. Also, blocks not reachable from the
475 // entry are special; uses in them don't need to go through PHIs.
476 if (UserBB != &BB && !L.contains(BB: UserBB) &&
477 DT.isReachableFromEntry(A: UserBB))
478 return false;
479 }
480 }
481 return true;
482}
483
484bool Loop::isLCSSAForm(const DominatorTree &DT, bool IgnoreTokens) const {
485 // For each block we check that it doesn't have any uses outside of this loop.
486 return all_of(Range: this->blocks(), P: [&](const BasicBlock *BB) {
487 return isBlockInLCSSAForm(L: *this, BB: *BB, DT, IgnoreTokens);
488 });
489}
490
491bool Loop::isRecursivelyLCSSAForm(const DominatorTree &DT, const LoopInfo &LI,
492 bool IgnoreTokens) const {
493 // For each block we check that it doesn't have any uses outside of its
494 // innermost loop. This process will transitively guarantee that the current
495 // loop and all of the nested loops are in LCSSA form.
496 return all_of(Range: this->blocks(), P: [&](const BasicBlock *BB) {
497 return isBlockInLCSSAForm(L: *LI.getLoopFor(BB), BB: *BB, DT, IgnoreTokens);
498 });
499}
500
501bool Loop::isLoopSimplifyForm() const {
502 // Normal-form loops have a preheader, a single backedge, and all of their
503 // exits have all their predecessors inside the loop.
504 return getLoopPreheader() && getLoopLatch() && hasDedicatedExits();
505}
506
507// Routines that reform the loop CFG and split edges often fail on indirectbr.
508bool Loop::isSafeToClone() const {
509 // Return false if any loop blocks contain indirectbrs, or there are any calls
510 // to noduplicate functions.
511 for (BasicBlock *BB : this->blocks()) {
512 if (isa<IndirectBrInst>(Val: BB->getTerminator()))
513 return false;
514
515 for (Instruction &I : *BB)
516 if (auto *CB = dyn_cast<CallBase>(Val: &I))
517 if (CB->cannotDuplicate())
518 return false;
519 }
520 return true;
521}
522
523MDNode *Loop::getLoopID() const {
524 MDNode *LoopID = nullptr;
525
526 // Go through the latch blocks and check the terminator for the metadata.
527 SmallVector<BasicBlock *, 4> LatchesBlocks;
528 getLoopLatches(LoopLatches&: LatchesBlocks);
529 for (BasicBlock *BB : LatchesBlocks) {
530 Instruction *TI = BB->getTerminator();
531 MDNode *MD = TI->getMetadata(KindID: LLVMContext::MD_loop);
532
533 if (!MD)
534 return nullptr;
535
536 if (!LoopID)
537 LoopID = MD;
538 else if (MD != LoopID)
539 return nullptr;
540 }
541 if (!LoopID || LoopID->getNumOperands() == 0 ||
542 LoopID->getOperand(I: 0) != LoopID)
543 return nullptr;
544 return LoopID;
545}
546
547void Loop::setLoopID(MDNode *LoopID) const {
548 assert((!LoopID || LoopID->getNumOperands() > 0) &&
549 "Loop ID needs at least one operand");
550 assert((!LoopID || LoopID->getOperand(0) == LoopID) &&
551 "Loop ID should refer to itself");
552
553 SmallVector<BasicBlock *, 4> LoopLatches;
554 getLoopLatches(LoopLatches);
555 for (BasicBlock *BB : LoopLatches)
556 BB->getTerminator()->setMetadata(KindID: LLVMContext::MD_loop, Node: LoopID);
557}
558
559void Loop::setLoopAlreadyUnrolled() {
560 addStringLoopAttribute(Name: "llvm.loop.unroll.disable", RemovePrefixes: {"llvm.loop.unroll."});
561}
562
563void Loop::setLoopMustProgress() {
564 if (findOptionMDForLoop(TheLoop: this, Name: "llvm.loop.mustprogress"))
565 return;
566 addStringLoopAttribute(Name: "llvm.loop.mustprogress");
567}
568
569void Loop::addStringLoopAttribute(StringRef Name,
570 ArrayRef<StringRef> RemovePrefixes) const {
571 LLVMContext &Context = getHeader()->getContext();
572 MDNode *AttrMD = MDNode::get(Context, MDs: MDString::get(Context, Str: Name));
573 MDNode *LoopID = getLoopID();
574 MDNode *NewLoopID =
575 makePostTransformationMetadata(Context, OrigLoopID: LoopID, RemovePrefixes, AddAttrs: {AttrMD});
576 setLoopID(NewLoopID);
577}
578
579void Loop::addIntLoopAttribute(StringRef Name, unsigned Value,
580 ArrayRef<StringRef> RemovePrefixes) const {
581 LLVMContext &Context = getHeader()->getContext();
582 MDNode *AttrMD = MDNode::get(
583 Context,
584 MDs: {MDString::get(Context, Str: Name),
585 ConstantAsMetadata::get(C: ConstantInt::get(Context, V: APInt(32, Value)))});
586 MDNode *LoopID = getLoopID();
587 MDNode *NewLoopID =
588 makePostTransformationMetadata(Context, OrigLoopID: LoopID, RemovePrefixes, AddAttrs: {AttrMD});
589 setLoopID(NewLoopID);
590}
591
592bool Loop::isAnnotatedParallel() const {
593 MDNode *DesiredLoopIdMetadata = getLoopID();
594
595 if (!DesiredLoopIdMetadata)
596 return false;
597
598 MDNode *ParallelAccesses =
599 findOptionMDForLoop(TheLoop: this, Name: "llvm.loop.parallel_accesses");
600 SmallPtrSet<MDNode *, 4>
601 ParallelAccessGroups; // For scalable 'contains' check.
602 if (ParallelAccesses) {
603 for (const MDOperand &MD : drop_begin(RangeOrContainer: ParallelAccesses->operands())) {
604 MDNode *AccGroup = cast<MDNode>(Val: MD.get());
605 assert(isValidAsAccessGroup(AccGroup) &&
606 "List item must be an access group");
607 ParallelAccessGroups.insert(Ptr: AccGroup);
608 }
609 }
610
611 // The loop branch contains the parallel loop metadata. In order to ensure
612 // that any parallel-loop-unaware optimization pass hasn't added loop-carried
613 // dependencies (thus converted the loop back to a sequential loop), check
614 // that all the memory instructions in the loop belong to an access group that
615 // is parallel to this loop.
616 for (BasicBlock *BB : this->blocks()) {
617 for (Instruction &I : *BB) {
618 if (!I.mayReadOrWriteMemory())
619 continue;
620
621 if (MDNode *AccessGroup = I.getMetadata(KindID: LLVMContext::MD_access_group)) {
622 auto ContainsAccessGroup = [&ParallelAccessGroups](MDNode *AG) -> bool {
623 if (AG->getNumOperands() == 0) {
624 assert(isValidAsAccessGroup(AG) && "Item must be an access group");
625 return ParallelAccessGroups.count(Ptr: AG);
626 }
627
628 for (const MDOperand &AccessListItem : AG->operands()) {
629 MDNode *AccGroup = cast<MDNode>(Val: AccessListItem.get());
630 assert(isValidAsAccessGroup(AccGroup) &&
631 "List item must be an access group");
632 if (ParallelAccessGroups.count(Ptr: AccGroup))
633 return true;
634 }
635 return false;
636 };
637
638 if (ContainsAccessGroup(AccessGroup))
639 continue;
640 }
641
642 // The memory instruction can refer to the loop identifier metadata
643 // directly or indirectly through another list metadata (in case of
644 // nested parallel loops). The loop identifier metadata refers to
645 // itself so we can check both cases with the same routine.
646 MDNode *LoopIdMD =
647 I.getMetadata(KindID: LLVMContext::MD_mem_parallel_loop_access);
648
649 if (!LoopIdMD)
650 return false;
651
652 if (!llvm::is_contained(Range: LoopIdMD->operands(), Element: DesiredLoopIdMetadata))
653 return false;
654 }
655 }
656 return true;
657}
658
659DebugLoc Loop::getStartLoc() const { return getLocRange().getStart(); }
660
661Loop::LocRange Loop::getLocRange() const {
662 // If we have a debug location in the loop ID, then use it.
663 if (MDNode *LoopID = getLoopID()) {
664 DebugLoc Start;
665 // We use the first DebugLoc in the header as the start location of the loop
666 // and if there is a second DebugLoc in the header we use it as end location
667 // of the loop.
668 for (const MDOperand &MDO : llvm::drop_begin(RangeOrContainer: LoopID->operands())) {
669 if (DILocation *L = dyn_cast<DILocation>(Val: MDO)) {
670 if (!Start)
671 Start = DebugLoc(L);
672 else
673 return LocRange(Start, DebugLoc(L));
674 }
675 }
676
677 if (Start)
678 return LocRange(Start);
679 }
680
681 // Try the pre-header first.
682 if (BasicBlock *PHeadBB = getLoopPreheader())
683 if (DebugLoc DL = PHeadBB->getTerminator()->getDebugLoc())
684 return LocRange(DL);
685
686 // If we have no pre-header or there are no instructions with debug
687 // info in it, try the header.
688 if (BasicBlock *HeadBB = getHeader())
689 return LocRange(HeadBB->getTerminator()->getDebugLoc());
690
691 return LocRange();
692}
693
694std::string Loop::getLocStr() const {
695 std::string Result;
696 raw_string_ostream OS(Result);
697 if (const DebugLoc LoopDbgLoc = getStartLoc())
698 LoopDbgLoc.print(OS);
699 else
700 // Just print the module name.
701 OS << getHeader()->getParent()->getParent()->getModuleIdentifier();
702 return Result;
703}
704
705#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
706LLVM_DUMP_METHOD void Loop::dump() const { print(dbgs()); }
707
708LLVM_DUMP_METHOD void Loop::dumpVerbose() const {
709 print(dbgs(), /*Verbose=*/true);
710}
711#endif
712
713//===----------------------------------------------------------------------===//
714// UnloopUpdater implementation
715//
716
717namespace {
718/// Find the new parent loop for all blocks within the "unloop" whose last
719/// backedges has just been removed.
720class UnloopUpdater {
721 Loop &Unloop;
722 LoopInfo *LI;
723
724 LoopBlocksDFS DFS;
725
726 // Map unloop's immediate subloops to their nearest reachable parents. Nested
727 // loops within these subloops will not change parents. However, an immediate
728 // subloop's new parent will be the nearest loop reachable from either its own
729 // exits *or* any of its nested loop's exits.
730 DenseMap<Loop *, Loop *> SubloopParents;
731
732 // Flag the presence of an irreducible backedge whose destination is a block
733 // directly contained by the original unloop.
734 bool FoundIB = false;
735
736public:
737 UnloopUpdater(Loop *UL, LoopInfo *LInfo) : Unloop(*UL), LI(LInfo), DFS(UL) {}
738
739 void updateBlockParents();
740
741 void removeBlocksFromAncestors();
742
743 void updateSubloopParents();
744
745protected:
746 Loop *getNearestLoop(BasicBlock *BB, Loop *BBLoop);
747};
748} // end anonymous namespace
749
750/// Update the parent loop for all blocks that are directly contained within the
751/// original "unloop".
752void UnloopUpdater::updateBlockParents() {
753 if (Unloop.getNumBlocks()) {
754 // Perform a post order CFG traversal of all blocks within this loop,
755 // propagating the nearest loop from successors to predecessors.
756 LoopBlocksTraversal Traversal(DFS, LI);
757 for (BasicBlock *POI : Traversal) {
758
759 Loop *L = LI->getLoopFor(BB: POI);
760 Loop *NL = getNearestLoop(BB: POI, BBLoop: L);
761
762 if (NL != L) {
763 // For reducible loops, NL is now an ancestor of Unloop.
764 assert((NL != &Unloop && (!NL || NL->contains(&Unloop))) &&
765 "uninitialized successor");
766 LI->changeLoopFor(BB: POI, L: NL);
767 } else {
768 // Or the current block is part of a subloop, in which case its parent
769 // is unchanged.
770 assert((FoundIB || Unloop.contains(L)) && "uninitialized successor");
771 }
772 }
773 }
774 // Each irreducible loop within the unloop induces a round of iteration using
775 // the DFS result cached by Traversal.
776 bool Changed = FoundIB;
777 for (unsigned NIters = 0; Changed; ++NIters) {
778 assert(NIters < Unloop.getNumBlocks() && "runaway iterative algorithm");
779 (void)NIters;
780
781 // Iterate over the postorder list of blocks, propagating the nearest loop
782 // from successors to predecessors as before.
783 Changed = false;
784 for (LoopBlocksDFS::POIterator POI = DFS.beginPostorder(),
785 POE = DFS.endPostorder();
786 POI != POE; ++POI) {
787
788 Loop *L = LI->getLoopFor(BB: *POI);
789 Loop *NL = getNearestLoop(BB: *POI, BBLoop: L);
790 if (NL != L) {
791 assert(NL != &Unloop && (!NL || NL->contains(&Unloop)) &&
792 "uninitialized successor");
793 LI->changeLoopFor(BB: *POI, L: NL);
794 Changed = true;
795 }
796 }
797 }
798}
799
800/// Remove unloop's blocks from all ancestors below their new parents.
801void UnloopUpdater::removeBlocksFromAncestors() {
802 // Remove all unloop's blocks (including those in nested subloops) from
803 // ancestors below the new parent loop.
804 for (BasicBlock *BB : Unloop.blocks()) {
805 Loop *OuterParent = LI->getLoopFor(BB);
806 if (Unloop.contains(L: OuterParent)) {
807 while (OuterParent->getParentLoop() != &Unloop)
808 OuterParent = OuterParent->getParentLoop();
809 OuterParent = SubloopParents[OuterParent];
810 }
811 // Remove blocks from former Ancestors except Unloop itself which will be
812 // deleted.
813 for (Loop *OldParent = Unloop.getParentLoop(); OldParent != OuterParent;
814 OldParent = OldParent->getParentLoop()) {
815 assert(OldParent && "new loop is not an ancestor of the original");
816 OldParent->removeBlockFromLoop(BB);
817 }
818 }
819}
820
821/// Update the parent loop for all subloops directly nested within unloop.
822void UnloopUpdater::updateSubloopParents() {
823 while (!Unloop.isInnermost()) {
824 Loop *Subloop = *std::prev(x: Unloop.end());
825 Unloop.removeChildLoop(I: std::prev(x: Unloop.end()));
826
827 assert(SubloopParents.count(Subloop) && "DFS failed to visit subloop");
828 if (Loop *Parent = SubloopParents[Subloop])
829 Parent->addChildLoop(NewChild: Subloop);
830 else
831 LI->addTopLevelLoop(New: Subloop);
832 }
833}
834
835/// Return the nearest parent loop among this block's successors. If a successor
836/// is a subloop header, consider its parent to be the nearest parent of the
837/// subloop's exits.
838///
839/// For subloop blocks, simply update SubloopParents and return NULL.
840Loop *UnloopUpdater::getNearestLoop(BasicBlock *BB, Loop *BBLoop) {
841
842 // Initially for blocks directly contained by Unloop, NearLoop == Unloop and
843 // is considered uninitialized.
844 Loop *NearLoop = BBLoop;
845
846 Loop *Subloop = nullptr;
847 if (NearLoop != &Unloop && Unloop.contains(L: NearLoop)) {
848 Subloop = NearLoop;
849 // Find the subloop ancestor that is directly contained within Unloop.
850 while (Subloop->getParentLoop() != &Unloop) {
851 Subloop = Subloop->getParentLoop();
852 assert(Subloop && "subloop is not an ancestor of the original loop");
853 }
854 // Get the current nearest parent of the Subloop exits, initially Unloop.
855 NearLoop = SubloopParents.insert(KV: {Subloop, &Unloop}).first->second;
856 }
857
858 if (succ_empty(BB)) {
859 assert(!Subloop && "subloop blocks must have a successor");
860 NearLoop = nullptr; // unloop blocks may now exit the function.
861 }
862 for (BasicBlock *Succ : successors(BB)) {
863 if (Succ == BB)
864 continue; // self loops are uninteresting
865
866 Loop *L = LI->getLoopFor(BB: Succ);
867 if (L == &Unloop) {
868 // This successor has not been processed. This path must lead to an
869 // irreducible backedge.
870 assert((FoundIB || !DFS.hasPostorder(Succ)) && "should have seen IB");
871 FoundIB = true;
872 }
873 if (L != &Unloop && Unloop.contains(L)) {
874 // Successor is in a subloop.
875 if (Subloop)
876 continue; // Branching within subloops. Ignore it.
877
878 // BB branches from the original into a subloop header.
879 assert(L->getParentLoop() == &Unloop && "cannot skip into nested loops");
880
881 // Get the current nearest parent of the Subloop's exits.
882 L = SubloopParents[L];
883 // L could be Unloop if the only exit was an irreducible backedge.
884 }
885 if (L == &Unloop) {
886 continue;
887 }
888 // Handle critical edges from Unloop into a sibling loop.
889 if (L && !L->contains(L: &Unloop)) {
890 L = L->getParentLoop();
891 }
892 // Remember the nearest parent loop among successors or subloop exits.
893 if (NearLoop == &Unloop || !NearLoop || NearLoop->contains(L))
894 NearLoop = L;
895 }
896 if (Subloop) {
897 SubloopParents[Subloop] = NearLoop;
898 return BBLoop;
899 }
900 return NearLoop;
901}
902
903LoopInfo::LoopInfo(const DomTreeBase<BasicBlock> &DomTree) { analyze(DomTree); }
904
905bool LoopInfo::invalidate(Function &F, const PreservedAnalyses &PA,
906 FunctionAnalysisManager::Invalidator &) {
907 // Check whether the analysis, all analyses on functions, or the function's
908 // CFG have been preserved.
909 auto PAC = PA.getChecker<LoopAnalysis>();
910 return !(PAC.preserved() || PAC.preservedSet<AllAnalysesOn<Function>>() ||
911 PAC.preservedSet<CFGAnalyses>());
912}
913
914void LoopInfo::erase(Loop *Unloop) {
915 assert(!Unloop->isInvalid() && "Loop has already been erased!");
916
917 llvm::scope_exit InvalidateOnExit([&]() { destroy(L: Unloop); });
918
919 // First handle the special case of no parent loop to simplify the algorithm.
920 if (Unloop->isOutermost()) {
921 // Since BBLoop had no parent, Unloop blocks are no longer in a loop.
922 for (BasicBlock *BB : Unloop->blocks()) {
923 // Don't reparent blocks in subloops.
924 if (getLoopFor(BB) != Unloop)
925 continue;
926
927 // Blocks no longer have a parent but are still referenced by Unloop until
928 // the Unloop object is deleted.
929 changeLoopFor(BB, L: nullptr);
930 }
931
932 // Remove the loop from the top-level LoopInfo object.
933 for (iterator I = begin();; ++I) {
934 assert(I != end() && "Couldn't find loop");
935 if (*I == Unloop) {
936 removeLoop(I);
937 break;
938 }
939 }
940
941 // Move all of the subloops to the top-level.
942 while (!Unloop->isInnermost())
943 addTopLevelLoop(New: Unloop->removeChildLoop(I: std::prev(x: Unloop->end())));
944
945 return;
946 }
947
948 // Update the parent loop for all blocks within the loop. Blocks within
949 // subloops will not change parents.
950 UnloopUpdater Updater(Unloop, this);
951 Updater.updateBlockParents();
952
953 // Remove blocks from former ancestor loops.
954 Updater.removeBlocksFromAncestors();
955
956 // Add direct subloops as children in their new parent loop.
957 Updater.updateSubloopParents();
958
959 // Remove unloop from its parent loop.
960 Loop *ParentLoop = Unloop->getParentLoop();
961 for (Loop::iterator I = ParentLoop->begin();; ++I) {
962 assert(I != ParentLoop->end() && "Couldn't find loop");
963 if (*I == Unloop) {
964 ParentLoop->removeChildLoop(I);
965 break;
966 }
967 }
968}
969
970bool LoopInfo::wouldBeOutOfLoopUseRequiringLCSSA(
971 const Value *V, const BasicBlock *ExitBB) const {
972 if (V->getType()->isTokenTy())
973 // We can't form PHIs of token type, so the definition of LCSSA excludes
974 // values of that type.
975 return false;
976
977 const Instruction *I = dyn_cast<Instruction>(Val: V);
978 if (!I)
979 return false;
980 const Loop *L = getLoopFor(BB: I->getParent());
981 if (!L)
982 return false;
983 if (L->contains(BB: ExitBB))
984 // Could be an exit bb of a subloop and contained in defining loop
985 return false;
986
987 // We found a (new) out-of-loop use location, for a value defined in-loop.
988 // (Note that because of LCSSA, we don't have to account for values defined
989 // in sibling loops. Such values will have LCSSA phis of their own in the
990 // common parent loop.)
991 return true;
992}
993
994AnalysisKey LoopAnalysis::Key;
995
996LoopInfo LoopAnalysis::run(Function &F, FunctionAnalysisManager &AM) {
997 // FIXME: Currently we create a LoopInfo from scratch for every function.
998 // This may prove to be too wasteful due to deallocating and re-allocating
999 // memory each time for the underlying map and vector datastructures. At some
1000 // point it may prove worthwhile to use a freelist and recycle LoopInfo
1001 // objects. I don't want to add that kind of complexity until the scope of
1002 // the problem is better understood.
1003 LoopInfo LI;
1004 LI.analyze(DomTree: AM.getResult<DominatorTreeAnalysis>(IR&: F));
1005 return LI;
1006}
1007
1008PreservedAnalyses LoopPrinterPass::run(Function &F,
1009 FunctionAnalysisManager &AM) {
1010 auto &LI = AM.getResult<LoopAnalysis>(IR&: F);
1011 OS << "Loop info for function '" << F.getName() << "':\n";
1012 LI.print(OS);
1013 return PreservedAnalyses::all();
1014}
1015
1016void llvm::printLoop(const Loop &L, raw_ostream &OS,
1017 const std::string &Banner) {
1018 if (forcePrintModuleIR()) {
1019 // handling -print-module-scope
1020 OS << Banner << " (loop: ";
1021 L.getHeader()->printAsOperand(O&: OS, PrintType: false);
1022 OS << ")\n";
1023
1024 // printing whole module
1025 OS << *L.getHeader()->getModule();
1026 return;
1027 }
1028
1029 if (forcePrintFuncIR()) {
1030 // handling -print-loop-func-scope.
1031 // -print-module-scope overrides this.
1032 OS << Banner << " (loop: ";
1033 L.getHeader()->printAsOperand(O&: OS, PrintType: false);
1034 OS << ")\n";
1035
1036 // printing whole function.
1037 OS << *L.getHeader()->getParent();
1038 return;
1039 }
1040
1041 OS << Banner;
1042
1043 auto *PreHeader = L.getLoopPreheader();
1044 if (PreHeader) {
1045 OS << "\n; Preheader:";
1046 PreHeader->print(OS);
1047 OS << "\n; Loop:";
1048 }
1049
1050 for (auto *Block : L.blocks())
1051 if (Block)
1052 Block->print(OS);
1053 else
1054 OS << "Printing <null> block";
1055
1056 SmallVector<BasicBlock *, 8> ExitBlocks;
1057 L.getExitBlocks(ExitBlocks);
1058 if (!ExitBlocks.empty()) {
1059 OS << "\n; Exit blocks";
1060 for (auto *Block : ExitBlocks)
1061 if (Block)
1062 Block->print(OS);
1063 else
1064 OS << "Printing <null> block";
1065 }
1066}
1067
1068MDNode *llvm::findOptionMDForLoopID(MDNode *LoopID, StringRef Name) {
1069 // No loop metadata node, no loop properties.
1070 if (!LoopID)
1071 return nullptr;
1072
1073 // First operand should refer to the metadata node itself, for legacy reasons.
1074 assert(LoopID->getNumOperands() > 0 && "requires at least one operand");
1075 assert(LoopID->getOperand(0) == LoopID && "invalid loop id");
1076
1077 // Iterate over the metdata node operands and look for MDString metadata.
1078 for (const MDOperand &MDO : llvm::drop_begin(RangeOrContainer: LoopID->operands())) {
1079 MDNode *MD = dyn_cast<MDNode>(Val: MDO);
1080 if (!MD || MD->getNumOperands() < 1)
1081 continue;
1082 MDString *S = dyn_cast<MDString>(Val: MD->getOperand(I: 0));
1083 if (!S)
1084 continue;
1085 // Return the operand node if MDString holds expected metadata.
1086 if (Name == S->getString())
1087 return MD;
1088 }
1089
1090 // Loop property not found.
1091 return nullptr;
1092}
1093
1094MDNode *llvm::findOptionMDForLoop(const Loop *TheLoop, StringRef Name) {
1095 return findOptionMDForLoopID(LoopID: TheLoop->getLoopID(), Name);
1096}
1097
1098/// Find string metadata for loop
1099///
1100/// If it has a value (e.g. {"llvm.distribute", 1} return the value as an
1101/// operand or null otherwise. If the string metadata is not found return
1102/// Optional's not-a-value.
1103std::optional<const MDOperand *>
1104llvm::findStringMetadataForLoop(const Loop *TheLoop, StringRef Name) {
1105 MDNode *MD = findOptionMDForLoop(TheLoop, Name);
1106 if (!MD)
1107 return std::nullopt;
1108 switch (MD->getNumOperands()) {
1109 case 1:
1110 return nullptr;
1111 case 2:
1112 return &MD->getOperand(I: 1);
1113 default:
1114 llvm_unreachable("loop metadata has 0 or 1 operand");
1115 }
1116}
1117
1118std::optional<bool> llvm::getOptionalBoolLoopAttribute(const Loop *TheLoop,
1119 StringRef Name) {
1120 MDNode *MD = findOptionMDForLoop(TheLoop, Name);
1121 if (!MD)
1122 return std::nullopt;
1123 switch (MD->getNumOperands()) {
1124 case 1:
1125 // When the value is absent it is interpreted as 'attribute set'.
1126 return true;
1127 case 2:
1128 if (ConstantInt *IntMD =
1129 mdconst::extract_or_null<ConstantInt>(MD: MD->getOperand(I: 1).get()))
1130 return IntMD->getZExtValue();
1131 return true;
1132 }
1133 llvm_unreachable("unexpected number of options");
1134}
1135
1136bool llvm::getBooleanLoopAttribute(const Loop *TheLoop, StringRef Name) {
1137 return getOptionalBoolLoopAttribute(TheLoop, Name).value_or(u: false);
1138}
1139
1140std::optional<int> llvm::getOptionalIntLoopAttribute(const Loop *TheLoop,
1141 StringRef Name) {
1142 const MDOperand *AttrMD =
1143 findStringMetadataForLoop(TheLoop, Name).value_or(u: nullptr);
1144 if (!AttrMD)
1145 return std::nullopt;
1146
1147 ConstantInt *IntMD = mdconst::extract_or_null<ConstantInt>(MD: AttrMD->get());
1148 if (!IntMD)
1149 return std::nullopt;
1150
1151 return IntMD->getSExtValue();
1152}
1153
1154int llvm::getIntLoopAttribute(const Loop *TheLoop, StringRef Name,
1155 int Default) {
1156 return getOptionalIntLoopAttribute(TheLoop, Name).value_or(u&: Default);
1157}
1158
1159CallBase *llvm::getLoopConvergenceHeart(const Loop *TheLoop) {
1160 BasicBlock *H = TheLoop->getHeader();
1161 for (Instruction &II : *H) {
1162 if (auto *CB = dyn_cast<CallBase>(Val: &II)) {
1163 if (!CB->isConvergent())
1164 continue;
1165 // This is the heart if it uses a token defined outside the loop. The
1166 // verifier has already checked that only the loop intrinsic can use such
1167 // a token.
1168 if (auto *Token = CB->getConvergenceControlToken()) {
1169 auto *TokenDef = cast<Instruction>(Val: Token);
1170 if (!TheLoop->contains(BB: TokenDef->getParent()))
1171 return CB;
1172 }
1173 return nullptr;
1174 }
1175 }
1176 return nullptr;
1177}
1178
1179bool llvm::isFinite(const Loop *L) {
1180 return L->getHeader()->getParent()->willReturn();
1181}
1182
1183static const char *LLVMLoopMustProgress = "llvm.loop.mustprogress";
1184
1185bool llvm::hasMustProgress(const Loop *L) {
1186 return getBooleanLoopAttribute(TheLoop: L, Name: LLVMLoopMustProgress);
1187}
1188
1189bool llvm::isMustProgress(const Loop *L) {
1190 return L->getHeader()->getParent()->mustProgress() || hasMustProgress(L);
1191}
1192
1193bool llvm::isValidAsAccessGroup(MDNode *Node) {
1194 return Node->getNumOperands() == 0 && Node->isDistinct();
1195}
1196
1197MDNode *llvm::makePostTransformationMetadata(LLVMContext &Context,
1198 MDNode *OrigLoopID,
1199 ArrayRef<StringRef> RemovePrefixes,
1200 ArrayRef<MDNode *> AddAttrs) {
1201 // First remove any existing loop metadata related to this transformation.
1202 SmallVector<Metadata *, 4> MDs;
1203
1204 // Reserve first location for self reference to the LoopID metadata node.
1205 MDs.push_back(Elt: nullptr);
1206
1207 // Remove metadata for the transformation that has been applied or that became
1208 // outdated.
1209 if (OrigLoopID) {
1210 for (const MDOperand &MDO : llvm::drop_begin(RangeOrContainer: OrigLoopID->operands())) {
1211 bool IsVectorMetadata = false;
1212 Metadata *Op = MDO;
1213 if (MDNode *MD = dyn_cast<MDNode>(Val: Op)) {
1214 const MDString *S = dyn_cast<MDString>(Val: MD->getOperand(I: 0));
1215 if (S)
1216 IsVectorMetadata =
1217 llvm::any_of(Range&: RemovePrefixes, P: [S](StringRef Prefix) -> bool {
1218 return S->getString().starts_with(Prefix);
1219 });
1220 }
1221 if (!IsVectorMetadata)
1222 MDs.push_back(Elt: Op);
1223 }
1224 }
1225
1226 // Add metadata to avoid reapplying a transformation, such as
1227 // llvm.loop.unroll.disable and llvm.loop.isvectorized.
1228 MDs.append(in_start: AddAttrs.begin(), in_end: AddAttrs.end());
1229
1230 MDNode *NewLoopID = MDNode::getDistinct(Context, MDs);
1231 // Replace the temporary node with a self-reference.
1232 NewLoopID->replaceOperandWith(I: 0, New: NewLoopID);
1233 return NewLoopID;
1234}
1235
1236//===----------------------------------------------------------------------===//
1237// LoopInfo implementation
1238//
1239
1240LoopInfoWrapperPass::LoopInfoWrapperPass() : FunctionPass(ID) {}
1241
1242char LoopInfoWrapperPass::ID = 0;
1243INITIALIZE_PASS_BEGIN(LoopInfoWrapperPass, "loops", "Natural Loop Information",
1244 true, true)
1245INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
1246INITIALIZE_PASS_END(LoopInfoWrapperPass, "loops", "Natural Loop Information",
1247 true, true)
1248
1249bool LoopInfoWrapperPass::runOnFunction(Function &) {
1250 releaseMemory();
1251 LI.analyze(DomTree: getAnalysis<DominatorTreeWrapperPass>().getDomTree());
1252 return false;
1253}
1254
1255void LoopInfoWrapperPass::verifyAnalysis() const {
1256 // LoopInfoWrapperPass is a FunctionPass, but verifying every loop in the
1257 // function each time verifyAnalysis is called is very expensive. The
1258 // -verify-loop-info option can enable this. In order to perform some
1259 // checking by default, LoopPass has been taught to call verifyLoop manually
1260 // during loop pass sequences.
1261 if (VerifyLoopInfo) {
1262 auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
1263 LI.verify(DomTree: DT);
1264 }
1265}
1266
1267void LoopInfoWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
1268 AU.setPreservesAll();
1269 AU.addRequiredTransitive<DominatorTreeWrapperPass>();
1270}
1271
1272void LoopInfoWrapperPass::print(raw_ostream &OS, const Module *) const {
1273 LI.print(OS);
1274}
1275
1276PreservedAnalyses LoopVerifierPass::run(Function &F,
1277 FunctionAnalysisManager &AM) {
1278 LoopInfo &LI = AM.getResult<LoopAnalysis>(IR&: F);
1279 auto &DT = AM.getResult<DominatorTreeAnalysis>(IR&: F);
1280 LI.verify(DomTree: DT);
1281 return PreservedAnalyses::all();
1282}
1283
1284//===----------------------------------------------------------------------===//
1285// LoopBlocksDFS implementation
1286//
1287
1288/// Traverse the loop blocks and store the DFS result.
1289/// Useful for clients that just want the final DFS result and don't need to
1290/// visit blocks during the initial traversal.
1291void LoopBlocksDFS::perform(const LoopInfo *LI) {
1292 LoopBlocksTraversal Traversal(*this, LI);
1293 for ([[maybe_unused]] BasicBlock *BB : Traversal)
1294 ;
1295}
1296