LLVM 20.0.0git
LoopInfo.cpp
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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
17#include "llvm/ADT/ScopeExit.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"
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"
41using namespace llvm;
42
43// Explicitly instantiate methods in LoopInfoImpl.h for IR-level Loops.
46
47// Always verify loopinfo if expensive checking is enabled.
48#ifdef EXPENSIVE_CHECKS
49bool llvm::VerifyLoopInfo = true;
50#else
52#endif
55 cl::Hidden, cl::desc("Verify loop info (time consuming)"));
56
57//===----------------------------------------------------------------------===//
58// Loop implementation
59//
60
61bool Loop::isLoopInvariant(const Value *V) const {
62 if (const Instruction *I = dyn_cast<Instruction>(V))
63 return !contains(I);
64 return true; // All non-instructions are loop invariant
65}
66
68 return all_of(I->operands(), [this](Value *V) { return isLoopInvariant(V); });
69}
70
71bool Loop::makeLoopInvariant(Value *V, bool &Changed, Instruction *InsertPt,
72 MemorySSAUpdater *MSSAU,
73 ScalarEvolution *SE) const {
74 if (Instruction *I = dyn_cast<Instruction>(V))
75 return makeLoopInvariant(I, Changed, InsertPt, MSSAU, SE);
76 return true; // All non-instructions are loop-invariant.
77}
78
80 Instruction *InsertPt, MemorySSAUpdater *MSSAU,
81 ScalarEvolution *SE) const {
82 // Test if the value is already loop-invariant.
83 if (isLoopInvariant(I))
84 return true;
86 return false;
87 if (I->mayReadFromMemory())
88 return false;
89 // EH block instructions are immobile.
90 if (I->isEHPad())
91 return false;
92 // Determine the insertion point, unless one was given.
93 if (!InsertPt) {
94 BasicBlock *Preheader = getLoopPreheader();
95 // Without a preheader, hoisting is not feasible.
96 if (!Preheader)
97 return false;
98 InsertPt = Preheader->getTerminator();
99 }
100 // Don't hoist instructions with loop-variant operands.
101 for (Value *Operand : I->operands())
102 if (!makeLoopInvariant(Operand, Changed, InsertPt, MSSAU, SE))
103 return false;
104
105 // Hoist.
106 I->moveBefore(InsertPt);
107 if (MSSAU)
108 if (auto *MUD = MSSAU->getMemorySSA()->getMemoryAccess(I))
109 MSSAU->moveToPlace(MUD, InsertPt->getParent(),
111
112 // There is possibility of hoisting this instruction above some arbitrary
113 // condition. Any metadata defined on it can be control dependent on this
114 // condition. Conservatively strip it here so that we don't give any wrong
115 // information to the optimizer.
116 I->dropUnknownNonDebugMetadata();
117
118 if (SE)
120
121 Changed = true;
122 return true;
123}
124
126 BasicBlock *&Backedge) const {
128
129 Incoming = nullptr;
130 Backedge = nullptr;
132 assert(PI != pred_end(H) && "Loop must have at least one backedge!");
133 Backedge = *PI++;
134 if (PI == pred_end(H))
135 return false; // dead loop
136 Incoming = *PI++;
137 if (PI != pred_end(H))
138 return false; // multiple backedges?
139
140 if (contains(Incoming)) {
141 if (contains(Backedge))
142 return false;
143 std::swap(Incoming, Backedge);
144 } else if (!contains(Backedge))
145 return false;
146
147 assert(Incoming && Backedge && "expected non-null incoming and backedges");
148 return true;
149}
150
153
154 BasicBlock *Incoming = nullptr, *Backedge = nullptr;
155 if (!getIncomingAndBackEdge(Incoming, Backedge))
156 return nullptr;
157
158 // Loop over all of the PHI nodes, looking for a canonical indvar.
159 for (BasicBlock::iterator I = H->begin(); isa<PHINode>(I); ++I) {
160 PHINode *PN = cast<PHINode>(I);
161 if (ConstantInt *CI =
162 dyn_cast<ConstantInt>(PN->getIncomingValueForBlock(Incoming)))
163 if (CI->isZero())
164 if (Instruction *Inc =
165 dyn_cast<Instruction>(PN->getIncomingValueForBlock(Backedge)))
166 if (Inc->getOpcode() == Instruction::Add && Inc->getOperand(0) == PN)
167 if (ConstantInt *CI = dyn_cast<ConstantInt>(Inc->getOperand(1)))
168 if (CI->isOne())
169 return PN;
170 }
171 return nullptr;
172}
173
174/// Get the latch condition instruction.
176 if (BasicBlock *Latch = getLoopLatch())
177 if (BranchInst *BI = dyn_cast_or_null<BranchInst>(Latch->getTerminator()))
178 if (BI->isConditional())
179 return dyn_cast<ICmpInst>(BI->getCondition());
180
181 return nullptr;
182}
183
184/// Return the final value of the loop induction variable if found.
185static Value *findFinalIVValue(const Loop &L, const PHINode &IndVar,
186 const Instruction &StepInst) {
187 ICmpInst *LatchCmpInst = L.getLatchCmpInst();
188 if (!LatchCmpInst)
189 return nullptr;
190
191 Value *Op0 = LatchCmpInst->getOperand(0);
192 Value *Op1 = LatchCmpInst->getOperand(1);
193 if (Op0 == &IndVar || Op0 == &StepInst)
194 return Op1;
195
196 if (Op1 == &IndVar || Op1 == &StepInst)
197 return Op0;
198
199 return nullptr;
200}
201
202std::optional<Loop::LoopBounds>
204 ScalarEvolution &SE) {
205 InductionDescriptor IndDesc;
206 if (!InductionDescriptor::isInductionPHI(&IndVar, &L, &SE, IndDesc))
207 return std::nullopt;
208
209 Value *InitialIVValue = IndDesc.getStartValue();
210 Instruction *StepInst = IndDesc.getInductionBinOp();
211 if (!InitialIVValue || !StepInst)
212 return std::nullopt;
213
214 const SCEV *Step = IndDesc.getStep();
215 Value *StepInstOp1 = StepInst->getOperand(1);
216 Value *StepInstOp0 = StepInst->getOperand(0);
217 Value *StepValue = nullptr;
218 if (SE.getSCEV(StepInstOp1) == Step)
219 StepValue = StepInstOp1;
220 else if (SE.getSCEV(StepInstOp0) == Step)
221 StepValue = StepInstOp0;
222
223 Value *FinalIVValue = findFinalIVValue(L, IndVar, *StepInst);
224 if (!FinalIVValue)
225 return std::nullopt;
226
227 return LoopBounds(L, *InitialIVValue, *StepInst, StepValue, *FinalIVValue,
228 SE);
229}
230
232
234 BasicBlock *Latch = L.getLoopLatch();
235 assert(Latch && "Expecting valid latch");
236
237 BranchInst *BI = dyn_cast_or_null<BranchInst>(Latch->getTerminator());
238 assert(BI && BI->isConditional() && "Expecting conditional latch branch");
239
240 ICmpInst *LatchCmpInst = dyn_cast<ICmpInst>(BI->getCondition());
241 assert(LatchCmpInst &&
242 "Expecting the latch compare instruction to be a CmpInst");
243
244 // Need to inverse the predicate when first successor is not the loop
245 // header
246 ICmpInst::Predicate Pred = (BI->getSuccessor(0) == L.getHeader())
247 ? LatchCmpInst->getPredicate()
248 : LatchCmpInst->getInversePredicate();
249
250 if (LatchCmpInst->getOperand(0) == &getFinalIVValue())
252
253 // Need to flip strictness of the predicate when the latch compare instruction
254 // is not using StepInst
255 if (LatchCmpInst->getOperand(0) == &getStepInst() ||
256 LatchCmpInst->getOperand(1) == &getStepInst())
257 return Pred;
258
259 // Cannot flip strictness of NE and EQ
260 if (Pred != ICmpInst::ICMP_NE && Pred != ICmpInst::ICMP_EQ)
262
263 Direction D = getDirection();
264 if (D == Direction::Increasing)
265 return ICmpInst::ICMP_SLT;
266
267 if (D == Direction::Decreasing)
268 return ICmpInst::ICMP_SGT;
269
270 // If cannot determine the direction, then unable to find the canonical
271 // predicate
273}
274
276 if (const SCEVAddRecExpr *StepAddRecExpr =
277 dyn_cast<SCEVAddRecExpr>(SE.getSCEV(&getStepInst())))
278 if (const SCEV *StepRecur = StepAddRecExpr->getStepRecurrence(SE)) {
279 if (SE.isKnownPositive(StepRecur))
280 return Direction::Increasing;
281 if (SE.isKnownNegative(StepRecur))
282 return Direction::Decreasing;
283 }
284
285 return Direction::Unknown;
286}
287
288std::optional<Loop::LoopBounds> Loop::getBounds(ScalarEvolution &SE) const {
289 if (PHINode *IndVar = getInductionVariable(SE))
290 return LoopBounds::getBounds(*this, *IndVar, SE);
291
292 return std::nullopt;
293}
294
296 if (!isLoopSimplifyForm())
297 return nullptr;
298
299 BasicBlock *Header = getHeader();
300 assert(Header && "Expected a valid loop header");
302 if (!CmpInst)
303 return nullptr;
304
305 Value *LatchCmpOp0 = CmpInst->getOperand(0);
306 Value *LatchCmpOp1 = CmpInst->getOperand(1);
307
308 for (PHINode &IndVar : Header->phis()) {
309 InductionDescriptor IndDesc;
310 if (!InductionDescriptor::isInductionPHI(&IndVar, this, &SE, IndDesc))
311 continue;
312
313 BasicBlock *Latch = getLoopLatch();
314 Value *StepInst = IndVar.getIncomingValueForBlock(Latch);
315
316 // case 1:
317 // IndVar = phi[{InitialValue, preheader}, {StepInst, latch}]
318 // StepInst = IndVar + step
319 // cmp = StepInst < FinalValue
320 if (StepInst == LatchCmpOp0 || StepInst == LatchCmpOp1)
321 return &IndVar;
322
323 // case 2:
324 // IndVar = phi[{InitialValue, preheader}, {StepInst, latch}]
325 // StepInst = IndVar + step
326 // cmp = IndVar < FinalValue
327 if (&IndVar == LatchCmpOp0 || &IndVar == LatchCmpOp1)
328 return &IndVar;
329 }
330
331 return nullptr;
332}
333
335 InductionDescriptor &IndDesc) const {
336 if (PHINode *IndVar = getInductionVariable(SE))
337 return InductionDescriptor::isInductionPHI(IndVar, this, &SE, IndDesc);
338
339 return false;
340}
341
343 ScalarEvolution &SE) const {
344 // Located in the loop header
345 BasicBlock *Header = getHeader();
346 if (AuxIndVar.getParent() != Header)
347 return false;
348
349 // No uses outside of the loop
350 for (User *U : AuxIndVar.users())
351 if (const Instruction *I = dyn_cast<Instruction>(U))
352 if (!contains(I))
353 return false;
354
355 InductionDescriptor IndDesc;
356 if (!InductionDescriptor::isInductionPHI(&AuxIndVar, this, &SE, IndDesc))
357 return false;
358
359 // The step instruction opcode should be add or sub.
360 if (IndDesc.getInductionOpcode() != Instruction::Add &&
361 IndDesc.getInductionOpcode() != Instruction::Sub)
362 return false;
363
364 // Incremented by a loop invariant step for each loop iteration
365 return SE.isLoopInvariant(IndDesc.getStep(), this);
366}
367
369 if (!isLoopSimplifyForm())
370 return nullptr;
371
372 BasicBlock *Preheader = getLoopPreheader();
373 assert(Preheader && getLoopLatch() &&
374 "Expecting a loop with valid preheader and latch");
375
376 // Loop should be in rotate form.
377 if (!isRotatedForm())
378 return nullptr;
379
380 // Disallow loops with more than one unique exit block, as we do not verify
381 // that GuardOtherSucc post dominates all exit blocks.
382 BasicBlock *ExitFromLatch = getUniqueExitBlock();
383 if (!ExitFromLatch)
384 return nullptr;
385
386 BasicBlock *GuardBB = Preheader->getUniquePredecessor();
387 if (!GuardBB)
388 return nullptr;
389
390 assert(GuardBB->getTerminator() && "Expecting valid guard terminator");
391
392 BranchInst *GuardBI = dyn_cast<BranchInst>(GuardBB->getTerminator());
393 if (!GuardBI || GuardBI->isUnconditional())
394 return nullptr;
395
396 BasicBlock *GuardOtherSucc = (GuardBI->getSuccessor(0) == Preheader)
397 ? GuardBI->getSuccessor(1)
398 : GuardBI->getSuccessor(0);
399
400 // Check if ExitFromLatch (or any BasicBlock which is an empty unique
401 // successor of ExitFromLatch) is equal to GuardOtherSucc. If
402 // skipEmptyBlockUntil returns GuardOtherSucc, then the guard branch for the
403 // loop is GuardBI (return GuardBI), otherwise return nullptr.
404 if (&LoopNest::skipEmptyBlockUntil(ExitFromLatch, GuardOtherSucc,
405 /*CheckUniquePred=*/true) ==
406 GuardOtherSucc)
407 return GuardBI;
408 else
409 return nullptr;
410}
411
413 InductionDescriptor IndDesc;
414 if (!getInductionDescriptor(SE, IndDesc))
415 return false;
416
417 ConstantInt *Init = dyn_cast_or_null<ConstantInt>(IndDesc.getStartValue());
418 if (!Init || !Init->isZero())
419 return false;
420
421 if (IndDesc.getInductionOpcode() != Instruction::Add)
422 return false;
423
424 ConstantInt *Step = IndDesc.getConstIntStepValue();
425 if (!Step || !Step->isOne())
426 return false;
427
428 return true;
429}
430
431// Check that 'BB' doesn't have any uses outside of the 'L'
432static bool isBlockInLCSSAForm(const Loop &L, const BasicBlock &BB,
433 const DominatorTree &DT, bool IgnoreTokens) {
434 for (const Instruction &I : BB) {
435 // Tokens can't be used in PHI nodes and live-out tokens prevent loop
436 // optimizations, so for the purposes of considered LCSSA form, we
437 // can ignore them.
438 if (IgnoreTokens && I.getType()->isTokenTy())
439 continue;
440
441 for (const Use &U : I.uses()) {
442 const Instruction *UI = cast<Instruction>(U.getUser());
443 const BasicBlock *UserBB = UI->getParent();
444
445 // For practical purposes, we consider that the use in a PHI
446 // occurs in the respective predecessor block. For more info,
447 // see the `phi` doc in LangRef and the LCSSA doc.
448 if (const PHINode *P = dyn_cast<PHINode>(UI))
449 UserBB = P->getIncomingBlock(U);
450
451 // Check the current block, as a fast-path, before checking whether
452 // the use is anywhere in the loop. Most values are used in the same
453 // block they are defined in. Also, blocks not reachable from the
454 // entry are special; uses in them don't need to go through PHIs.
455 if (UserBB != &BB && !L.contains(UserBB) &&
456 DT.isReachableFromEntry(UserBB))
457 return false;
458 }
459 }
460 return true;
461}
462
463bool Loop::isLCSSAForm(const DominatorTree &DT, bool IgnoreTokens) const {
464 // For each block we check that it doesn't have any uses outside of this loop.
465 return all_of(this->blocks(), [&](const BasicBlock *BB) {
466 return isBlockInLCSSAForm(*this, *BB, DT, IgnoreTokens);
467 });
468}
469
471 bool IgnoreTokens) const {
472 // For each block we check that it doesn't have any uses outside of its
473 // innermost loop. This process will transitively guarantee that the current
474 // loop and all of the nested loops are in LCSSA form.
475 return all_of(this->blocks(), [&](const BasicBlock *BB) {
476 return isBlockInLCSSAForm(*LI.getLoopFor(BB), *BB, DT, IgnoreTokens);
477 });
478}
479
481 // Normal-form loops have a preheader, a single backedge, and all of their
482 // exits have all their predecessors inside the loop.
484}
485
486// Routines that reform the loop CFG and split edges often fail on indirectbr.
488 // Return false if any loop blocks contain indirectbrs, or there are any calls
489 // to noduplicate functions.
490 for (BasicBlock *BB : this->blocks()) {
491 if (isa<IndirectBrInst>(BB->getTerminator()))
492 return false;
493
494 for (Instruction &I : *BB)
495 if (auto *CB = dyn_cast<CallBase>(&I))
496 if (CB->cannotDuplicate())
497 return false;
498 }
499 return true;
500}
501
503 MDNode *LoopID = nullptr;
504
505 // Go through the latch blocks and check the terminator for the metadata.
506 SmallVector<BasicBlock *, 4> LatchesBlocks;
507 getLoopLatches(LatchesBlocks);
508 for (BasicBlock *BB : LatchesBlocks) {
509 Instruction *TI = BB->getTerminator();
510 MDNode *MD = TI->getMetadata(LLVMContext::MD_loop);
511
512 if (!MD)
513 return nullptr;
514
515 if (!LoopID)
516 LoopID = MD;
517 else if (MD != LoopID)
518 return nullptr;
519 }
520 if (!LoopID || LoopID->getNumOperands() == 0 ||
521 LoopID->getOperand(0) != LoopID)
522 return nullptr;
523 return LoopID;
524}
525
526void Loop::setLoopID(MDNode *LoopID) const {
527 assert((!LoopID || LoopID->getNumOperands() > 0) &&
528 "Loop ID needs at least one operand");
529 assert((!LoopID || LoopID->getOperand(0) == LoopID) &&
530 "Loop ID should refer to itself");
531
533 getLoopLatches(LoopLatches);
534 for (BasicBlock *BB : LoopLatches)
535 BB->getTerminator()->setMetadata(LLVMContext::MD_loop, LoopID);
536}
537
539 LLVMContext &Context = getHeader()->getContext();
540
541 MDNode *DisableUnrollMD =
542 MDNode::get(Context, MDString::get(Context, "llvm.loop.unroll.disable"));
543 MDNode *LoopID = getLoopID();
545 Context, LoopID, {"llvm.loop.unroll."}, {DisableUnrollMD});
546 setLoopID(NewLoopID);
547}
548
550 LLVMContext &Context = getHeader()->getContext();
551
552 MDNode *MustProgress = findOptionMDForLoop(this, "llvm.loop.mustprogress");
553
554 if (MustProgress)
555 return;
556
557 MDNode *MustProgressMD =
558 MDNode::get(Context, MDString::get(Context, "llvm.loop.mustprogress"));
559 MDNode *LoopID = getLoopID();
560 MDNode *NewLoopID =
561 makePostTransformationMetadata(Context, LoopID, {}, {MustProgressMD});
562 setLoopID(NewLoopID);
563}
564
566 MDNode *DesiredLoopIdMetadata = getLoopID();
567
568 if (!DesiredLoopIdMetadata)
569 return false;
570
571 MDNode *ParallelAccesses =
572 findOptionMDForLoop(this, "llvm.loop.parallel_accesses");
574 ParallelAccessGroups; // For scalable 'contains' check.
575 if (ParallelAccesses) {
576 for (const MDOperand &MD : drop_begin(ParallelAccesses->operands())) {
577 MDNode *AccGroup = cast<MDNode>(MD.get());
578 assert(isValidAsAccessGroup(AccGroup) &&
579 "List item must be an access group");
580 ParallelAccessGroups.insert(AccGroup);
581 }
582 }
583
584 // The loop branch contains the parallel loop metadata. In order to ensure
585 // that any parallel-loop-unaware optimization pass hasn't added loop-carried
586 // dependencies (thus converted the loop back to a sequential loop), check
587 // that all the memory instructions in the loop belong to an access group that
588 // is parallel to this loop.
589 for (BasicBlock *BB : this->blocks()) {
590 for (Instruction &I : *BB) {
591 if (!I.mayReadOrWriteMemory())
592 continue;
593
594 if (MDNode *AccessGroup = I.getMetadata(LLVMContext::MD_access_group)) {
595 auto ContainsAccessGroup = [&ParallelAccessGroups](MDNode *AG) -> bool {
596 if (AG->getNumOperands() == 0) {
597 assert(isValidAsAccessGroup(AG) && "Item must be an access group");
598 return ParallelAccessGroups.count(AG);
599 }
600
601 for (const MDOperand &AccessListItem : AG->operands()) {
602 MDNode *AccGroup = cast<MDNode>(AccessListItem.get());
603 assert(isValidAsAccessGroup(AccGroup) &&
604 "List item must be an access group");
605 if (ParallelAccessGroups.count(AccGroup))
606 return true;
607 }
608 return false;
609 };
610
611 if (ContainsAccessGroup(AccessGroup))
612 continue;
613 }
614
615 // The memory instruction can refer to the loop identifier metadata
616 // directly or indirectly through another list metadata (in case of
617 // nested parallel loops). The loop identifier metadata refers to
618 // itself so we can check both cases with the same routine.
619 MDNode *LoopIdMD =
620 I.getMetadata(LLVMContext::MD_mem_parallel_loop_access);
621
622 if (!LoopIdMD)
623 return false;
624
625 if (!llvm::is_contained(LoopIdMD->operands(), DesiredLoopIdMetadata))
626 return false;
627 }
628 }
629 return true;
630}
631
633
635 // If we have a debug location in the loop ID, then use it.
636 if (MDNode *LoopID = getLoopID()) {
637 DebugLoc Start;
638 // We use the first DebugLoc in the header as the start location of the loop
639 // and if there is a second DebugLoc in the header we use it as end location
640 // of the loop.
641 for (const MDOperand &MDO : llvm::drop_begin(LoopID->operands())) {
642 if (DILocation *L = dyn_cast<DILocation>(MDO)) {
643 if (!Start)
644 Start = DebugLoc(L);
645 else
646 return LocRange(Start, DebugLoc(L));
647 }
648 }
649
650 if (Start)
651 return LocRange(Start);
652 }
653
654 // Try the pre-header first.
655 if (BasicBlock *PHeadBB = getLoopPreheader())
656 if (DebugLoc DL = PHeadBB->getTerminator()->getDebugLoc())
657 return LocRange(DL);
658
659 // If we have no pre-header or there are no instructions with debug
660 // info in it, try the header.
661 if (BasicBlock *HeadBB = getHeader())
662 return LocRange(HeadBB->getTerminator()->getDebugLoc());
663
664 return LocRange();
665}
666
667std::string Loop::getLocStr() const {
668 std::string Result;
669 raw_string_ostream OS(Result);
670 if (const DebugLoc LoopDbgLoc = getStartLoc())
671 LoopDbgLoc.print(OS);
672 else
673 // Just print the module name.
675 return Result;
676}
677
678#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
680
682 print(dbgs(), /*Verbose=*/true);
683}
684#endif
685
686//===----------------------------------------------------------------------===//
687// UnloopUpdater implementation
688//
689
690namespace {
691/// Find the new parent loop for all blocks within the "unloop" whose last
692/// backedges has just been removed.
693class UnloopUpdater {
694 Loop &Unloop;
695 LoopInfo *LI;
696
697 LoopBlocksDFS DFS;
698
699 // Map unloop's immediate subloops to their nearest reachable parents. Nested
700 // loops within these subloops will not change parents. However, an immediate
701 // subloop's new parent will be the nearest loop reachable from either its own
702 // exits *or* any of its nested loop's exits.
703 DenseMap<Loop *, Loop *> SubloopParents;
704
705 // Flag the presence of an irreducible backedge whose destination is a block
706 // directly contained by the original unloop.
707 bool FoundIB = false;
708
709public:
710 UnloopUpdater(Loop *UL, LoopInfo *LInfo) : Unloop(*UL), LI(LInfo), DFS(UL) {}
711
712 void updateBlockParents();
713
714 void removeBlocksFromAncestors();
715
716 void updateSubloopParents();
717
718protected:
719 Loop *getNearestLoop(BasicBlock *BB, Loop *BBLoop);
720};
721} // end anonymous namespace
722
723/// Update the parent loop for all blocks that are directly contained within the
724/// original "unloop".
725void UnloopUpdater::updateBlockParents() {
726 if (Unloop.getNumBlocks()) {
727 // Perform a post order CFG traversal of all blocks within this loop,
728 // propagating the nearest loop from successors to predecessors.
729 LoopBlocksTraversal Traversal(DFS, LI);
730 for (BasicBlock *POI : Traversal) {
731
732 Loop *L = LI->getLoopFor(POI);
733 Loop *NL = getNearestLoop(POI, L);
734
735 if (NL != L) {
736 // For reducible loops, NL is now an ancestor of Unloop.
737 assert((NL != &Unloop && (!NL || NL->contains(&Unloop))) &&
738 "uninitialized successor");
739 LI->changeLoopFor(POI, NL);
740 } else {
741 // Or the current block is part of a subloop, in which case its parent
742 // is unchanged.
743 assert((FoundIB || Unloop.contains(L)) && "uninitialized successor");
744 }
745 }
746 }
747 // Each irreducible loop within the unloop induces a round of iteration using
748 // the DFS result cached by Traversal.
749 bool Changed = FoundIB;
750 for (unsigned NIters = 0; Changed; ++NIters) {
751 assert(NIters < Unloop.getNumBlocks() && "runaway iterative algorithm");
752 (void)NIters;
753
754 // Iterate over the postorder list of blocks, propagating the nearest loop
755 // from successors to predecessors as before.
756 Changed = false;
757 for (LoopBlocksDFS::POIterator POI = DFS.beginPostorder(),
758 POE = DFS.endPostorder();
759 POI != POE; ++POI) {
760
761 Loop *L = LI->getLoopFor(*POI);
762 Loop *NL = getNearestLoop(*POI, L);
763 if (NL != L) {
764 assert(NL != &Unloop && (!NL || NL->contains(&Unloop)) &&
765 "uninitialized successor");
766 LI->changeLoopFor(*POI, NL);
767 Changed = true;
768 }
769 }
770 }
771}
772
773/// Remove unloop's blocks from all ancestors below their new parents.
774void UnloopUpdater::removeBlocksFromAncestors() {
775 // Remove all unloop's blocks (including those in nested subloops) from
776 // ancestors below the new parent loop.
777 for (BasicBlock *BB : Unloop.blocks()) {
778 Loop *OuterParent = LI->getLoopFor(BB);
779 if (Unloop.contains(OuterParent)) {
780 while (OuterParent->getParentLoop() != &Unloop)
781 OuterParent = OuterParent->getParentLoop();
782 OuterParent = SubloopParents[OuterParent];
783 }
784 // Remove blocks from former Ancestors except Unloop itself which will be
785 // deleted.
786 for (Loop *OldParent = Unloop.getParentLoop(); OldParent != OuterParent;
787 OldParent = OldParent->getParentLoop()) {
788 assert(OldParent && "new loop is not an ancestor of the original");
789 OldParent->removeBlockFromLoop(BB);
790 }
791 }
792}
793
794/// Update the parent loop for all subloops directly nested within unloop.
795void UnloopUpdater::updateSubloopParents() {
796 while (!Unloop.isInnermost()) {
797 Loop *Subloop = *std::prev(Unloop.end());
798 Unloop.removeChildLoop(std::prev(Unloop.end()));
799
800 assert(SubloopParents.count(Subloop) && "DFS failed to visit subloop");
801 if (Loop *Parent = SubloopParents[Subloop])
802 Parent->addChildLoop(Subloop);
803 else
804 LI->addTopLevelLoop(Subloop);
805 }
806}
807
808/// Return the nearest parent loop among this block's successors. If a successor
809/// is a subloop header, consider its parent to be the nearest parent of the
810/// subloop's exits.
811///
812/// For subloop blocks, simply update SubloopParents and return NULL.
813Loop *UnloopUpdater::getNearestLoop(BasicBlock *BB, Loop *BBLoop) {
814
815 // Initially for blocks directly contained by Unloop, NearLoop == Unloop and
816 // is considered uninitialized.
817 Loop *NearLoop = BBLoop;
818
819 Loop *Subloop = nullptr;
820 if (NearLoop != &Unloop && Unloop.contains(NearLoop)) {
821 Subloop = NearLoop;
822 // Find the subloop ancestor that is directly contained within Unloop.
823 while (Subloop->getParentLoop() != &Unloop) {
824 Subloop = Subloop->getParentLoop();
825 assert(Subloop && "subloop is not an ancestor of the original loop");
826 }
827 // Get the current nearest parent of the Subloop exits, initially Unloop.
828 NearLoop = SubloopParents.insert({Subloop, &Unloop}).first->second;
829 }
830
831 if (succ_empty(BB)) {
832 assert(!Subloop && "subloop blocks must have a successor");
833 NearLoop = nullptr; // unloop blocks may now exit the function.
834 }
835 for (BasicBlock *Succ : successors(BB)) {
836 if (Succ == BB)
837 continue; // self loops are uninteresting
838
839 Loop *L = LI->getLoopFor(Succ);
840 if (L == &Unloop) {
841 // This successor has not been processed. This path must lead to an
842 // irreducible backedge.
843 assert((FoundIB || !DFS.hasPostorder(Succ)) && "should have seen IB");
844 FoundIB = true;
845 }
846 if (L != &Unloop && Unloop.contains(L)) {
847 // Successor is in a subloop.
848 if (Subloop)
849 continue; // Branching within subloops. Ignore it.
850
851 // BB branches from the original into a subloop header.
852 assert(L->getParentLoop() == &Unloop && "cannot skip into nested loops");
853
854 // Get the current nearest parent of the Subloop's exits.
855 L = SubloopParents[L];
856 // L could be Unloop if the only exit was an irreducible backedge.
857 }
858 if (L == &Unloop) {
859 continue;
860 }
861 // Handle critical edges from Unloop into a sibling loop.
862 if (L && !L->contains(&Unloop)) {
863 L = L->getParentLoop();
864 }
865 // Remember the nearest parent loop among successors or subloop exits.
866 if (NearLoop == &Unloop || !NearLoop || NearLoop->contains(L))
867 NearLoop = L;
868 }
869 if (Subloop) {
870 SubloopParents[Subloop] = NearLoop;
871 return BBLoop;
872 }
873 return NearLoop;
874}
875
876LoopInfo::LoopInfo(const DomTreeBase<BasicBlock> &DomTree) { analyze(DomTree); }
877
880 // Check whether the analysis, all analyses on functions, or the function's
881 // CFG have been preserved.
882 auto PAC = PA.getChecker<LoopAnalysis>();
883 return !(PAC.preserved() || PAC.preservedSet<AllAnalysesOn<Function>>() ||
884 PAC.preservedSet<CFGAnalyses>());
885}
886
887void LoopInfo::erase(Loop *Unloop) {
888 assert(!Unloop->isInvalid() && "Loop has already been erased!");
889
890 auto InvalidateOnExit = make_scope_exit([&]() { destroy(Unloop); });
891
892 // First handle the special case of no parent loop to simplify the algorithm.
893 if (Unloop->isOutermost()) {
894 // Since BBLoop had no parent, Unloop blocks are no longer in a loop.
895 for (BasicBlock *BB : Unloop->blocks()) {
896 // Don't reparent blocks in subloops.
897 if (getLoopFor(BB) != Unloop)
898 continue;
899
900 // Blocks no longer have a parent but are still referenced by Unloop until
901 // the Unloop object is deleted.
902 changeLoopFor(BB, nullptr);
903 }
904
905 // Remove the loop from the top-level LoopInfo object.
906 for (iterator I = begin();; ++I) {
907 assert(I != end() && "Couldn't find loop");
908 if (*I == Unloop) {
909 removeLoop(I);
910 break;
911 }
912 }
913
914 // Move all of the subloops to the top-level.
915 while (!Unloop->isInnermost())
916 addTopLevelLoop(Unloop->removeChildLoop(std::prev(Unloop->end())));
917
918 return;
919 }
920
921 // Update the parent loop for all blocks within the loop. Blocks within
922 // subloops will not change parents.
923 UnloopUpdater Updater(Unloop, this);
924 Updater.updateBlockParents();
925
926 // Remove blocks from former ancestor loops.
927 Updater.removeBlocksFromAncestors();
928
929 // Add direct subloops as children in their new parent loop.
930 Updater.updateSubloopParents();
931
932 // Remove unloop from its parent loop.
933 Loop *ParentLoop = Unloop->getParentLoop();
934 for (Loop::iterator I = ParentLoop->begin();; ++I) {
935 assert(I != ParentLoop->end() && "Couldn't find loop");
936 if (*I == Unloop) {
937 ParentLoop->removeChildLoop(I);
938 break;
939 }
940 }
941}
942
944 const Value *V, const BasicBlock *ExitBB) const {
945 if (V->getType()->isTokenTy())
946 // We can't form PHIs of token type, so the definition of LCSSA excludes
947 // values of that type.
948 return false;
949
950 const Instruction *I = dyn_cast<Instruction>(V);
951 if (!I)
952 return false;
953 const Loop *L = getLoopFor(I->getParent());
954 if (!L)
955 return false;
956 if (L->contains(ExitBB))
957 // Could be an exit bb of a subloop and contained in defining loop
958 return false;
959
960 // We found a (new) out-of-loop use location, for a value defined in-loop.
961 // (Note that because of LCSSA, we don't have to account for values defined
962 // in sibling loops. Such values will have LCSSA phis of their own in the
963 // common parent loop.)
964 return true;
965}
966
967AnalysisKey LoopAnalysis::Key;
968
970 // FIXME: Currently we create a LoopInfo from scratch for every function.
971 // This may prove to be too wasteful due to deallocating and re-allocating
972 // memory each time for the underlying map and vector datastructures. At some
973 // point it may prove worthwhile to use a freelist and recycle LoopInfo
974 // objects. I don't want to add that kind of complexity until the scope of
975 // the problem is better understood.
976 LoopInfo LI;
978 return LI;
979}
980
983 auto &LI = AM.getResult<LoopAnalysis>(F);
984 OS << "Loop info for function '" << F.getName() << "':\n";
985 LI.print(OS);
986 return PreservedAnalyses::all();
987}
988
989void llvm::printLoop(Loop &L, raw_ostream &OS, const std::string &Banner) {
990
991 if (forcePrintModuleIR()) {
992 // handling -print-module-scope
993 OS << Banner << " (loop: ";
994 L.getHeader()->printAsOperand(OS, false);
995 OS << ")\n";
996
997 // printing whole module
998 OS << *L.getHeader()->getModule();
999 return;
1000 }
1001
1002 OS << Banner;
1003
1004 auto *PreHeader = L.getLoopPreheader();
1005 if (PreHeader) {
1006 OS << "\n; Preheader:";
1007 PreHeader->print(OS);
1008 OS << "\n; Loop:";
1009 }
1010
1011 for (auto *Block : L.blocks())
1012 if (Block)
1013 Block->print(OS);
1014 else
1015 OS << "Printing <null> block";
1016
1018 L.getExitBlocks(ExitBlocks);
1019 if (!ExitBlocks.empty()) {
1020 OS << "\n; Exit blocks";
1021 for (auto *Block : ExitBlocks)
1022 if (Block)
1023 Block->print(OS);
1024 else
1025 OS << "Printing <null> block";
1026 }
1027}
1028
1030 // No loop metadata node, no loop properties.
1031 if (!LoopID)
1032 return nullptr;
1033
1034 // First operand should refer to the metadata node itself, for legacy reasons.
1035 assert(LoopID->getNumOperands() > 0 && "requires at least one operand");
1036 assert(LoopID->getOperand(0) == LoopID && "invalid loop id");
1037
1038 // Iterate over the metdata node operands and look for MDString metadata.
1039 for (const MDOperand &MDO : llvm::drop_begin(LoopID->operands())) {
1040 MDNode *MD = dyn_cast<MDNode>(MDO);
1041 if (!MD || MD->getNumOperands() < 1)
1042 continue;
1043 MDString *S = dyn_cast<MDString>(MD->getOperand(0));
1044 if (!S)
1045 continue;
1046 // Return the operand node if MDString holds expected metadata.
1047 if (Name == S->getString())
1048 return MD;
1049 }
1050
1051 // Loop property not found.
1052 return nullptr;
1053}
1054
1056 return findOptionMDForLoopID(TheLoop->getLoopID(), Name);
1057}
1058
1059/// Find string metadata for loop
1060///
1061/// If it has a value (e.g. {"llvm.distribute", 1} return the value as an
1062/// operand or null otherwise. If the string metadata is not found return
1063/// Optional's not-a-value.
1064std::optional<const MDOperand *>
1066 MDNode *MD = findOptionMDForLoop(TheLoop, Name);
1067 if (!MD)
1068 return std::nullopt;
1069 switch (MD->getNumOperands()) {
1070 case 1:
1071 return nullptr;
1072 case 2:
1073 return &MD->getOperand(1);
1074 default:
1075 llvm_unreachable("loop metadata has 0 or 1 operand");
1076 }
1077}
1078
1079std::optional<bool> llvm::getOptionalBoolLoopAttribute(const Loop *TheLoop,
1080 StringRef Name) {
1081 MDNode *MD = findOptionMDForLoop(TheLoop, Name);
1082 if (!MD)
1083 return std::nullopt;
1084 switch (MD->getNumOperands()) {
1085 case 1:
1086 // When the value is absent it is interpreted as 'attribute set'.
1087 return true;
1088 case 2:
1089 if (ConstantInt *IntMD =
1090 mdconst::extract_or_null<ConstantInt>(MD->getOperand(1).get()))
1091 return IntMD->getZExtValue();
1092 return true;
1093 }
1094 llvm_unreachable("unexpected number of options");
1095}
1096
1098 return getOptionalBoolLoopAttribute(TheLoop, Name).value_or(false);
1099}
1100
1101std::optional<int> llvm::getOptionalIntLoopAttribute(const Loop *TheLoop,
1102 StringRef Name) {
1103 const MDOperand *AttrMD =
1104 findStringMetadataForLoop(TheLoop, Name).value_or(nullptr);
1105 if (!AttrMD)
1106 return std::nullopt;
1107
1108 ConstantInt *IntMD = mdconst::extract_or_null<ConstantInt>(AttrMD->get());
1109 if (!IntMD)
1110 return std::nullopt;
1111
1112 return IntMD->getSExtValue();
1113}
1114
1116 int Default) {
1117 return getOptionalIntLoopAttribute(TheLoop, Name).value_or(Default);
1118}
1119
1121 BasicBlock *H = TheLoop->getHeader();
1122 for (Instruction &II : *H) {
1123 if (auto *CB = dyn_cast<CallBase>(&II)) {
1124 if (!CB->isConvergent())
1125 continue;
1126 // This is the heart if it uses a token defined outside the loop. The
1127 // verifier has already checked that only the loop intrinsic can use such
1128 // a token.
1129 if (auto *Token = CB->getConvergenceControlToken()) {
1130 auto *TokenDef = cast<Instruction>(Token);
1131 if (!TheLoop->contains(TokenDef->getParent()))
1132 return CB;
1133 }
1134 return nullptr;
1135 }
1136 }
1137 return nullptr;
1138}
1139
1140bool llvm::isFinite(const Loop *L) {
1141 return L->getHeader()->getParent()->willReturn();
1142}
1143
1144static const char *LLVMLoopMustProgress = "llvm.loop.mustprogress";
1145
1148}
1149
1151 return L->getHeader()->getParent()->mustProgress() || hasMustProgress(L);
1152}
1153
1155 return Node->getNumOperands() == 0 && Node->isDistinct();
1156}
1157
1159 MDNode *OrigLoopID,
1160 ArrayRef<StringRef> RemovePrefixes,
1161 ArrayRef<MDNode *> AddAttrs) {
1162 // First remove any existing loop metadata related to this transformation.
1164
1165 // Reserve first location for self reference to the LoopID metadata node.
1166 MDs.push_back(nullptr);
1167
1168 // Remove metadata for the transformation that has been applied or that became
1169 // outdated.
1170 if (OrigLoopID) {
1171 for (const MDOperand &MDO : llvm::drop_begin(OrigLoopID->operands())) {
1172 bool IsVectorMetadata = false;
1173 Metadata *Op = MDO;
1174 if (MDNode *MD = dyn_cast<MDNode>(Op)) {
1175 const MDString *S = dyn_cast<MDString>(MD->getOperand(0));
1176 if (S)
1177 IsVectorMetadata =
1178 llvm::any_of(RemovePrefixes, [S](StringRef Prefix) -> bool {
1179 return S->getString().starts_with(Prefix);
1180 });
1181 }
1182 if (!IsVectorMetadata)
1183 MDs.push_back(Op);
1184 }
1185 }
1186
1187 // Add metadata to avoid reapplying a transformation, such as
1188 // llvm.loop.unroll.disable and llvm.loop.isvectorized.
1189 MDs.append(AddAttrs.begin(), AddAttrs.end());
1190
1191 MDNode *NewLoopID = MDNode::getDistinct(Context, MDs);
1192 // Replace the temporary node with a self-reference.
1193 NewLoopID->replaceOperandWith(0, NewLoopID);
1194 return NewLoopID;
1195}
1196
1197//===----------------------------------------------------------------------===//
1198// LoopInfo implementation
1199//
1200
1203}
1204
1206INITIALIZE_PASS_BEGIN(LoopInfoWrapperPass, "loops", "Natural Loop Information",
1207 true, true)
1211
1213 releaseMemory();
1214 LI.analyze(getAnalysis<DominatorTreeWrapperPass>().getDomTree());
1215 return false;
1216}
1217
1219 // LoopInfoWrapperPass is a FunctionPass, but verifying every loop in the
1220 // function each time verifyAnalysis is called is very expensive. The
1221 // -verify-loop-info option can enable this. In order to perform some
1222 // checking by default, LoopPass has been taught to call verifyLoop manually
1223 // during loop pass sequences.
1224 if (VerifyLoopInfo) {
1225 auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
1226 LI.verify(DT);
1227 }
1228}
1229
1231 AU.setPreservesAll();
1233}
1234
1236 LI.print(OS);
1237}
1238
1241 LoopInfo &LI = AM.getResult<LoopAnalysis>(F);
1242 auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
1243 LI.verify(DT);
1244 return PreservedAnalyses::all();
1245}
1246
1247//===----------------------------------------------------------------------===//
1248// LoopBlocksDFS implementation
1249//
1250
1251/// Traverse the loop blocks and store the DFS result.
1252/// Useful for clients that just want the final DFS result and don't need to
1253/// visit blocks during the initial traversal.
1255 LoopBlocksTraversal Traversal(*this, LI);
1256 for (LoopBlocksTraversal::POTIterator POI = Traversal.begin(),
1257 POE = Traversal.end();
1258 POI != POE; ++POI)
1259 ;
1260}
MachineBasicBlock MachineBasicBlock::iterator DebugLoc DL
basic Basic Alias true
static GCRegistry::Add< StatepointGC > D("statepoint-example", "an example strategy for statepoint")
#define LLVM_DUMP_METHOD
Mark debug helper function definitions like dump() that should not be stripped from debug builds.
Definition: Compiler.h:537
This file contains the declarations for the subclasses of Constant, which represent the different fla...
#define NL
std::string Name
static bool runOnFunction(Function &F, bool PostInlining)
This file provides various utilities for inspecting and working with the control flow graph in LLVM I...
static bool isBlockInLCSSAForm(const Loop &L, const BasicBlock &BB, const DominatorTree &DT, bool IgnoreTokens)
Definition: LoopInfo.cpp:432
loops
Definition: LoopInfo.cpp:1209
static const char * LLVMLoopMustProgress
Definition: LoopInfo.cpp:1144
static Value * findFinalIVValue(const Loop &L, const PHINode &IndVar, const Instruction &StepInst)
Return the final value of the loop induction variable if found.
Definition: LoopInfo.cpp:185
Natural Loop Information
Definition: LoopInfo.cpp:1209
static cl::opt< bool, true > VerifyLoopInfoX("verify-loop-info", cl::location(VerifyLoopInfo), cl::Hidden, cl::desc("Verify loop info (time consuming)"))
This file defines the interface for the loop nest analysis.
#define F(x, y, z)
Definition: MD5.cpp:55
#define I(x, y, z)
Definition: MD5.cpp:58
#define H(x, y, z)
Definition: MD5.cpp:57
This file exposes an interface to building/using memory SSA to walk memory instructions using a use/d...
This file contains the declarations for metadata subclasses.
Module.h This file contains the declarations for the Module class.
uint64_t IntrinsicInst * II
#define P(N)
This header defines various interfaces for pass management in LLVM.
#define INITIALIZE_PASS_DEPENDENCY(depName)
Definition: PassSupport.h:55
#define INITIALIZE_PASS_END(passName, arg, name, cfg, analysis)
Definition: PassSupport.h:57
#define INITIALIZE_PASS_BEGIN(passName, arg, name, cfg, analysis)
Definition: PassSupport.h:52
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
raw_pwrite_stream & OS
This file defines the make_scope_exit function, which executes user-defined cleanup logic at scope ex...
This file defines the SmallPtrSet class.
DEMANGLE_NAMESPACE_BEGIN bool starts_with(std::string_view self, char C) noexcept
This templated class represents "all analyses that operate over <a particular IR unit>" (e....
Definition: Analysis.h:49
API to communicate dependencies between analyses during invalidation.
Definition: PassManager.h:292
A container for analyses that lazily runs them and caches their results.
Definition: PassManager.h:253
PassT::Result & getResult(IRUnitT &IR, ExtraArgTs... ExtraArgs)
Get the result of an analysis pass for a given IR unit.
Definition: PassManager.h:405
Represent the analysis usage information of a pass.
void setPreservesAll()
Set by analyses that do not transform their input at all.
AnalysisUsage & addRequiredTransitive()
ArrayRef - Represent a constant reference to an array (0 or more elements consecutively in memory),...
Definition: ArrayRef.h:41
iterator end() const
Definition: ArrayRef.h:154
iterator begin() const
Definition: ArrayRef.h:153
LLVM Basic Block Representation.
Definition: BasicBlock.h:61
const BasicBlock * getUniquePredecessor() const
Return the predecessor of this block if it has a unique predecessor block.
Definition: BasicBlock.cpp:467
const Function * getParent() const
Return the enclosing method, or null if none.
Definition: BasicBlock.h:219
InstListType::iterator iterator
Instruction iterators...
Definition: BasicBlock.h:177
LLVMContext & getContext() const
Get the context in which this basic block lives.
Definition: BasicBlock.cpp:168
const Instruction * getTerminator() const LLVM_READONLY
Returns the terminator instruction if the block is well formed or null if the block is not well forme...
Definition: BasicBlock.h:239
Conditional or Unconditional Branch instruction.
bool isConditional() const
BasicBlock * getSuccessor(unsigned i) const
bool isUnconditional() const
Value * getCondition() const
Represents analyses that only rely on functions' control flow.
Definition: Analysis.h:72
Base class for all callable instructions (InvokeInst and CallInst) Holds everything related to callin...
Definition: InstrTypes.h:1236
This class is the base class for the comparison instructions.
Definition: InstrTypes.h:747
Predicate
This enumeration lists the possible predicates for CmpInst subclasses.
Definition: InstrTypes.h:757
@ ICMP_SLT
signed less than
Definition: InstrTypes.h:786
@ ICMP_SGT
signed greater than
Definition: InstrTypes.h:784
@ ICMP_EQ
equal
Definition: InstrTypes.h:778
@ ICMP_NE
not equal
Definition: InstrTypes.h:779
Predicate getSwappedPredicate() const
For example, EQ->EQ, SLE->SGE, ULT->UGT, OEQ->OEQ, ULE->UGE, OLT->OGT, etc.
Definition: InstrTypes.h:909
Predicate getInversePredicate() const
For example, EQ -> NE, UGT -> ULE, SLT -> SGE, OEQ -> UNE, UGT -> OLE, OLT -> UGE,...
Definition: InstrTypes.h:871
Predicate getPredicate() const
Return the predicate for this instruction.
Definition: InstrTypes.h:847
Predicate getFlippedStrictnessPredicate() const
For predicate of kind "is X or equal to 0" returns the predicate "is X".
Definition: InstrTypes.h:975
This is the shared class of boolean and integer constants.
Definition: Constants.h:81
bool isOne() const
This is just a convenience method to make client code smaller for a common case.
Definition: Constants.h:212
int64_t getSExtValue() const
Return the constant as a 64-bit integer value after it has been sign extended as appropriate for the ...
Definition: Constants.h:161
Debug location.
This class represents an Operation in the Expression.
A debug info location.
Definition: DebugLoc.h:33
Analysis pass which computes a DominatorTree.
Definition: Dominators.h:279
Core dominator tree base class.
Legacy analysis pass which computes a DominatorTree.
Definition: Dominators.h:317
Concrete subclass of DominatorTreeBase that is used to compute a normal dominator tree.
Definition: Dominators.h:162
bool isReachableFromEntry(const Use &U) const
Provide an overload for a Use.
Definition: Dominators.cpp:321
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:310
Module * getParent()
Get the module that this global value is contained inside of...
Definition: GlobalValue.h:656
This instruction compares its operands according to the predicate given to the constructor.
A struct for saving information about induction variables.
BinaryOperator * getInductionBinOp() const
const SCEV * getStep() const
static bool isInductionPHI(PHINode *Phi, const Loop *L, ScalarEvolution *SE, InductionDescriptor &D, const SCEV *Expr=nullptr, SmallVectorImpl< Instruction * > *CastsToIgnore=nullptr)
Returns true if Phi is an induction in the loop L.
Instruction::BinaryOps getInductionOpcode() const
Returns binary opcode of the induction operator.
Value * getStartValue() const
ConstantInt * getConstIntStepValue() const
MDNode * getMetadata(unsigned KindID) const
Get the metadata of given kind attached to this Instruction.
Definition: Instruction.h:381
This is an important class for using LLVM in a threaded context.
Definition: LLVMContext.h:67
Analysis pass that exposes the LoopInfo for a function.
Definition: LoopInfo.h:571
LoopInfo run(Function &F, FunctionAnalysisManager &AM)
Definition: LoopInfo.cpp:969
Instances of this class are used to represent loops that are detected in the flow graph.
bool contains(const Loop *L) const
Return true if the specified loop is contained within in this loop.
bool isOutermost() const
Return true if the loop does not have a parent (natural) loop.
BasicBlock * getLoopLatch() const
If there is a single latch block for this loop, return it.
bool isInnermost() const
Return true if the loop does not contain any (natural) loops.
void getLoopLatches(SmallVectorImpl< BasicBlock * > &LoopLatches) const
Return all loop latch blocks of this loop.
void print(raw_ostream &OS, bool Verbose=false, bool PrintNested=true, unsigned Depth=0) const
Print loop with all the BBs inside it.
std::vector< Loop * >::const_iterator iterator
iterator_range< block_iterator > blocks() const
bool isInvalid() const
Return true if this loop is no longer valid.
BasicBlock * getLoopPreheader() const
If there is a preheader for this loop, return it.
LoopT * getParentLoop() const
Return the parent loop if it exists or nullptr for top level loops.
bool hasDedicatedExits() const
Return true if no exit block for the loop has a predecessor that is outside the loop.
BasicBlock * getUniqueExitBlock() const
If getUniqueExitBlocks would return exactly one block, return that block.
LoopT * removeChildLoop(iterator I)
This removes the specified child from being a subloop of this loop.
Store the result of a depth first search within basic blocks contained by a single loop.
Definition: LoopIterator.h:97
std::vector< BasicBlock * >::const_iterator POIterator
Postorder list iterators.
Definition: LoopIterator.h:100
void perform(const LoopInfo *LI)
Traverse the loop blocks and store the DFS result.
Definition: LoopInfo.cpp:1254
Traverse the blocks in a loop using a depth-first search.
Definition: LoopIterator.h:200
POTIterator begin()
Postorder traversal over the graph.
Definition: LoopIterator.h:216
This class builds and contains all of the top-level loop structures in the specified function.
void verify(const DominatorTreeBase< BlockT, false > &DomTree) const
void analyze(const DominatorTreeBase< BlockT, false > &DomTree)
Create the loop forest using a stable algorithm.
void print(raw_ostream &OS) const
LoopT * getLoopFor(const BlockT *BB) const
Return the inner most loop that BB lives in.
std::vector< Loop * >::const_iterator iterator
iterator/begin/end - The interface to the top-level loops in the current function.
The legacy pass manager's analysis pass to compute loop information.
Definition: LoopInfo.h:598
void getAnalysisUsage(AnalysisUsage &AU) const override
getAnalysisUsage - This function should be overriden by passes that need analysis information to do t...
Definition: LoopInfo.cpp:1230
void verifyAnalysis() const override
verifyAnalysis() - This member can be implemented by a analysis pass to check state of analysis infor...
Definition: LoopInfo.cpp:1218
void print(raw_ostream &O, const Module *M=nullptr) const override
print - Print out the internal state of the pass.
Definition: LoopInfo.cpp:1235
LoopInfo()=default
bool wouldBeOutOfLoopUseRequiringLCSSA(const Value *V, const BasicBlock *ExitBB) const
Definition: LoopInfo.cpp:943
bool invalidate(Function &F, const PreservedAnalyses &PA, FunctionAnalysisManager::Invalidator &)
Handle invalidation explicitly.
Definition: LoopInfo.cpp:878
void erase(Loop *L)
Update LoopInfo after removing the last backedge from a loop.
Definition: LoopInfo.cpp:887
static const BasicBlock & skipEmptyBlockUntil(const BasicBlock *From, const BasicBlock *End, bool CheckUniquePred=false)
Recursivelly traverse all empty 'single successor' basic blocks of From (if there are any).
PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM)
Definition: LoopInfo.cpp:981
A range representing the start and end location of a loop.
Definition: LoopInfo.h:47
const DebugLoc & getStart() const
Definition: LoopInfo.h:57
Represents a single loop in the control flow graph.
Definition: LoopInfo.h:44
bool isCanonical(ScalarEvolution &SE) const
Return true if the loop induction variable starts at zero and increments by one each time through the...
Definition: LoopInfo.cpp:412
bool isLCSSAForm(const DominatorTree &DT, bool IgnoreTokens=true) const
Return true if the Loop is in LCSSA form.
Definition: LoopInfo.cpp:463
std::optional< LoopBounds > getBounds(ScalarEvolution &SE) const
Return the struct LoopBounds collected if all struct members are found, else std::nullopt.
Definition: LoopInfo.cpp:288
bool isSafeToClone() const
Return true if the loop body is safe to clone in practice.
Definition: LoopInfo.cpp:487
std::string getLocStr() const
Return a string containing the debug location of the loop (file name + line number if present,...
Definition: LoopInfo.cpp:667
void dumpVerbose() const
Definition: LoopInfo.cpp:681
bool hasLoopInvariantOperands(const Instruction *I) const
Return true if all the operands of the specified instruction are loop invariant.
Definition: LoopInfo.cpp:67
BranchInst * getLoopGuardBranch() const
Return the loop guard branch, if it exists.
Definition: LoopInfo.cpp:368
bool isAnnotatedParallel() const
Returns true if the loop is annotated parallel.
Definition: LoopInfo.cpp:565
DebugLoc getStartLoc() const
Return the debug location of the start of this loop.
Definition: LoopInfo.cpp:632
void dump() const
Definition: LoopInfo.cpp:679
LocRange getLocRange() const
Return the source code span of the loop.
Definition: LoopInfo.cpp:634
bool isLoopInvariant(const Value *V) const
Return true if the specified value is loop invariant.
Definition: LoopInfo.cpp:61
ICmpInst * getLatchCmpInst() const
Get the latch condition instruction.
Definition: LoopInfo.cpp:175
bool getInductionDescriptor(ScalarEvolution &SE, InductionDescriptor &IndDesc) const
Get the loop induction descriptor for the loop induction variable.
Definition: LoopInfo.cpp:334
bool isRotatedForm() const
Return true if the loop is in rotated form.
Definition: LoopInfo.h:307
void setLoopMustProgress()
Add llvm.loop.mustprogress to this loop's loop id metadata.
Definition: LoopInfo.cpp:549
PHINode * getInductionVariable(ScalarEvolution &SE) const
Return the loop induction variable if found, else return nullptr.
Definition: LoopInfo.cpp:295
bool isLoopSimplifyForm() const
Return true if the Loop is in the form that the LoopSimplify form transforms loops to,...
Definition: LoopInfo.cpp:480
bool isRecursivelyLCSSAForm(const DominatorTree &DT, const LoopInfo &LI, bool IgnoreTokens=true) const
Return true if this Loop and all inner subloops are in LCSSA form.
Definition: LoopInfo.cpp:470
void setLoopID(MDNode *LoopID) const
Set the llvm.loop loop id metadata for this loop.
Definition: LoopInfo.cpp:526
void setLoopAlreadyUnrolled()
Add llvm.loop.unroll.disable to this loop's loop id metadata.
Definition: LoopInfo.cpp:538
bool makeLoopInvariant(Value *V, bool &Changed, Instruction *InsertPt=nullptr, MemorySSAUpdater *MSSAU=nullptr, ScalarEvolution *SE=nullptr) const
If the given value is an instruction inside of the loop and it can be hoisted, do so to make it trivi...
Definition: LoopInfo.cpp:71
PHINode * getCanonicalInductionVariable() const
Check to see if the loop has a canonical induction variable: an integer recurrence that starts at 0 a...
Definition: LoopInfo.cpp:151
bool getIncomingAndBackEdge(BasicBlock *&Incoming, BasicBlock *&Backedge) const
Obtain the unique incoming and back edge.
Definition: LoopInfo.cpp:125
MDNode * getLoopID() const
Return the llvm.loop loop id metadata node for this loop if it is present.
Definition: LoopInfo.cpp:502
bool isAuxiliaryInductionVariable(PHINode &AuxIndVar, ScalarEvolution &SE) const
Return true if the given PHINode AuxIndVar is.
Definition: LoopInfo.cpp:342
Metadata node.
Definition: Metadata.h:1069
void replaceOperandWith(unsigned I, Metadata *New)
Replace a specific operand.
Definition: Metadata.cpp:1077
static MDTuple * getDistinct(LLVMContext &Context, ArrayRef< Metadata * > MDs)
Definition: Metadata.h:1550
const MDOperand & getOperand(unsigned I) const
Definition: Metadata.h:1430
ArrayRef< MDOperand > operands() const
Definition: Metadata.h:1428
static MDTuple * get(LLVMContext &Context, ArrayRef< Metadata * > MDs)
Definition: Metadata.h:1542
unsigned getNumOperands() const
Return number of MDNode operands.
Definition: Metadata.h:1436
Tracking metadata reference owned by Metadata.
Definition: Metadata.h:891
Metadata * get() const
Definition: Metadata.h:920
A single uniqued string.
Definition: Metadata.h:720
StringRef getString() const
Definition: Metadata.cpp:616
static MDString * get(LLVMContext &Context, StringRef Str)
Definition: Metadata.cpp:606
MemorySSA * getMemorySSA() const
Get handle on MemorySSA.
void moveToPlace(MemoryUseOrDef *What, BasicBlock *BB, MemorySSA::InsertionPlace Where)
MemoryUseOrDef * getMemoryAccess(const Instruction *I) const
Given a memory Mod/Ref'ing instruction, get the MemorySSA access associated with it.
Definition: MemorySSA.h:719
Root of the metadata hierarchy.
Definition: Metadata.h:62
A Module instance is used to store all the information related to an LLVM module.
Definition: Module.h:65
const std::string & getModuleIdentifier() const
Get the module identifier which is, essentially, the name of the module.
Definition: Module.h:265
Value * getIncomingValueForBlock(const BasicBlock *BB) const
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
A set of analyses that are preserved following a run of a transformation pass.
Definition: Analysis.h:111
static PreservedAnalyses all()
Construct a special preserved set that preserves all passes.
Definition: Analysis.h:117
PreservedAnalysisChecker getChecker() const
Build a checker for this PreservedAnalyses and the specified analysis type.
Definition: Analysis.h:264
This node represents a polynomial recurrence on the trip count of the specified loop.
This class represents an analyzed expression in the program.
The main scalar evolution driver.
const SCEV * getSCEV(Value *V)
Return a SCEV expression for the full generality of the specified expression.
bool isLoopInvariant(const SCEV *S, const Loop *L)
Return true if the value of the given SCEV is unchanging in the specified loop.
void forgetBlockAndLoopDispositions(Value *V=nullptr)
Called when the client has changed the disposition of values in a loop or block.
size_type count(ConstPtrType Ptr) const
count - Return 1 if the specified pointer is in the set, 0 otherwise.
Definition: SmallPtrSet.h:436
std::pair< iterator, bool > insert(PtrType Ptr)
Inserts Ptr if and only if there is no element in the container equal to Ptr.
Definition: SmallPtrSet.h:368
SmallPtrSet - This class implements a set which is optimized for holding SmallSize or less elements.
Definition: SmallPtrSet.h:503
bool empty() const
Definition: SmallVector.h:95
void append(ItTy in_start, ItTy in_end)
Add the specified range to the end of the SmallVector.
Definition: SmallVector.h:697
void push_back(const T &Elt)
Definition: SmallVector.h:427
This is a 'vector' (really, a variable-sized array), optimized for the case when the array is small.
Definition: SmallVector.h:1210
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:50
A Use represents the edge between a Value definition and its users.
Definition: Use.h:43
Value * getOperand(unsigned i) const
Definition: User.h:169
LLVM Value Representation.
Definition: Value.h:74
iterator_range< user_iterator > users()
Definition: Value.h:421
const ParentTy * getParent() const
Definition: ilist_node.h:32
This class implements an extremely fast bulk output stream that can only output to a stream.
Definition: raw_ostream.h:52
A raw_ostream that writes to an std::string.
Definition: raw_ostream.h:661
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
LocationClass< Ty > location(Ty &L)
Definition: CommandLine.h:463
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
auto drop_begin(T &&RangeOrContainer, size_t N=1)
Return a range covering RangeOrContainer with the first N elements excluded.
Definition: STLExtras.h:329
pred_iterator pred_end(BasicBlock *BB)
Definition: CFG.h:114
bool all_of(R &&range, UnaryPredicate P)
Provide wrappers to std::all_of which take ranges instead of having to pass begin/end explicitly.
Definition: STLExtras.h:1722
bool getBooleanLoopAttribute(const Loop *TheLoop, StringRef Name)
Returns true if Name is applied to TheLoop and enabled.
Definition: LoopInfo.cpp:1097
bool succ_empty(const Instruction *I)
Definition: CFG.h:255
bool forcePrintModuleIR()
void initializeLoopInfoWrapperPassPass(PassRegistry &)
detail::scope_exit< std::decay_t< Callable > > make_scope_exit(Callable &&F)
Definition: ScopeExit.h:59
std::optional< bool > getOptionalBoolLoopAttribute(const Loop *TheLoop, StringRef Name)
Definition: LoopInfo.cpp:1079
int getIntLoopAttribute(const Loop *TheLoop, StringRef Name, int Default=0)
Find named metadata for a loop with an integer value.
Definition: LoopInfo.cpp:1115
std::optional< const MDOperand * > findStringMetadataForLoop(const Loop *TheLoop, StringRef Name)
Find string metadata for loop.
Definition: LoopInfo.cpp:1065
auto successors(const MachineBasicBlock *BB)
MDNode * findOptionMDForLoop(const Loop *TheLoop, StringRef Name)
Find string metadata for a loop.
Definition: LoopInfo.cpp:1055
bool hasMustProgress(const Loop *L)
Look for the loop attribute that requires progress within the loop.
Definition: LoopInfo.cpp:1146
bool any_of(R &&range, UnaryPredicate P)
Provide wrappers to std::any_of which take ranges instead of having to pass begin/end explicitly.
Definition: STLExtras.h:1729
pred_iterator pred_begin(BasicBlock *BB)
Definition: CFG.h:110
bool isMustProgress(const Loop *L)
Return true if this loop can be assumed to make progress.
Definition: LoopInfo.cpp:1150
CallBase * getLoopConvergenceHeart(const Loop *TheLoop)
Find the convergence heart of the loop.
Definition: LoopInfo.cpp:1120
bool isFinite(const Loop *L)
Return true if this loop can be assumed to run for a finite number of iterations.
Definition: LoopInfo.cpp:1140
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:163
bool isSafeToSpeculativelyExecute(const Instruction *I, const Instruction *CtxI=nullptr, AssumptionCache *AC=nullptr, const DominatorTree *DT=nullptr, const TargetLibraryInfo *TLI=nullptr, bool UseVariableInfo=true)
Return true if the instruction does not have any effects besides calculating the result and does not ...
bool VerifyLoopInfo
Enable verification of loop info.
Definition: LoopInfo.cpp:51
std::optional< int > getOptionalIntLoopAttribute(const Loop *TheLoop, StringRef Name)
Find named metadata for a loop with an integer value.
Definition: LoopInfo.cpp:1101
bool isValidAsAccessGroup(MDNode *AccGroup)
Return whether an MDNode might represent an access group.
Definition: LoopInfo.cpp:1154
llvm::MDNode * makePostTransformationMetadata(llvm::LLVMContext &Context, MDNode *OrigLoopID, llvm::ArrayRef< llvm::StringRef > RemovePrefixes, llvm::ArrayRef< llvm::MDNode * > AddAttrs)
Create a new LoopID after the loop has been transformed.
Definition: LoopInfo.cpp:1158
bool is_contained(R &&Range, const E &Element)
Returns true if Element is found in Range.
Definition: STLExtras.h:1879
@ Default
The result values are uniform if and only if all operands are uniform.
void printLoop(Loop &L, raw_ostream &OS, const std::string &Banner="")
Function to print a loop's contents as LLVM's text IR assembly.
Definition: LoopInfo.cpp:989
MDNode * findOptionMDForLoopID(MDNode *LoopID, StringRef Name)
Find and return the loop attribute node for the attribute Name in LoopID.
Definition: LoopInfo.cpp:1029
void swap(llvm::BitVector &LHS, llvm::BitVector &RHS)
Implement std::swap in terms of BitVector swap.
Definition: BitVector.h:860
A special type used by analysis passes to provide an address that identifies that particular analysis...
Definition: Analysis.h:28
Incoming for lane maks phi as machine instruction, incoming register Reg and incoming block Block are...
PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM)
Definition: LoopInfo.cpp:1239
Below are some utilities to get the loop guard, loop bounds and induction variable,...
Definition: LoopInfo.h:157
static std::optional< Loop::LoopBounds > getBounds(const Loop &L, PHINode &IndVar, ScalarEvolution &SE)
Return the LoopBounds object if.
Definition: LoopInfo.cpp:203
Direction
An enum for the direction of the loop.
Definition: LoopInfo.h:220
ICmpInst::Predicate getCanonicalPredicate() const
Return the canonical predicate for the latch compare instruction, if able to be calcuated.
Definition: LoopInfo.cpp:233
Direction getDirection() const
Get the direction of the loop.
Definition: LoopInfo.cpp:275