LLVM 19.0.0git
InductiveRangeCheckElimination.cpp
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1//===- InductiveRangeCheckElimination.cpp - -------------------------------===//
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// The InductiveRangeCheckElimination pass splits a loop's iteration space into
10// three disjoint ranges. It does that in a way such that the loop running in
11// the middle loop provably does not need range checks. As an example, it will
12// convert
13//
14// len = < known positive >
15// for (i = 0; i < n; i++) {
16// if (0 <= i && i < len) {
17// do_something();
18// } else {
19// throw_out_of_bounds();
20// }
21// }
22//
23// to
24//
25// len = < known positive >
26// limit = smin(n, len)
27// // no first segment
28// for (i = 0; i < limit; i++) {
29// if (0 <= i && i < len) { // this check is fully redundant
30// do_something();
31// } else {
32// throw_out_of_bounds();
33// }
34// }
35// for (i = limit; i < n; i++) {
36// if (0 <= i && i < len) {
37// do_something();
38// } else {
39// throw_out_of_bounds();
40// }
41// }
42//
43//===----------------------------------------------------------------------===//
44
46#include "llvm/ADT/APInt.h"
47#include "llvm/ADT/ArrayRef.h"
51#include "llvm/ADT/StringRef.h"
52#include "llvm/ADT/Twine.h"
59#include "llvm/IR/BasicBlock.h"
60#include "llvm/IR/CFG.h"
61#include "llvm/IR/Constants.h"
63#include "llvm/IR/Dominators.h"
64#include "llvm/IR/Function.h"
65#include "llvm/IR/IRBuilder.h"
66#include "llvm/IR/InstrTypes.h"
68#include "llvm/IR/Metadata.h"
69#include "llvm/IR/Module.h"
71#include "llvm/IR/Type.h"
72#include "llvm/IR/Use.h"
73#include "llvm/IR/User.h"
74#include "llvm/IR/Value.h"
79#include "llvm/Support/Debug.h"
89#include <algorithm>
90#include <cassert>
91#include <iterator>
92#include <optional>
93#include <utility>
94
95using namespace llvm;
96using namespace llvm::PatternMatch;
97
98static cl::opt<unsigned> LoopSizeCutoff("irce-loop-size-cutoff", cl::Hidden,
99 cl::init(64));
100
101static cl::opt<bool> PrintChangedLoops("irce-print-changed-loops", cl::Hidden,
102 cl::init(false));
103
104static cl::opt<bool> PrintRangeChecks("irce-print-range-checks", cl::Hidden,
105 cl::init(false));
106
107static cl::opt<bool> SkipProfitabilityChecks("irce-skip-profitability-checks",
108 cl::Hidden, cl::init(false));
109
110static cl::opt<unsigned> MinRuntimeIterations("irce-min-runtime-iterations",
111 cl::Hidden, cl::init(10));
112
113static cl::opt<bool> AllowUnsignedLatchCondition("irce-allow-unsigned-latch",
114 cl::Hidden, cl::init(true));
115
117 "irce-allow-narrow-latch", cl::Hidden, cl::init(true),
118 cl::desc("If set to true, IRCE may eliminate wide range checks in loops "
119 "with narrow latch condition."));
120
122 "irce-max-type-size-for-overflow-check", cl::Hidden, cl::init(32),
123 cl::desc(
124 "Maximum size of range check type for which can be produced runtime "
125 "overflow check of its limit's computation"));
126
127static cl::opt<bool>
128 PrintScaledBoundaryRangeChecks("irce-print-scaled-boundary-range-checks",
129 cl::Hidden, cl::init(false));
130
131#define DEBUG_TYPE "irce"
132
133namespace {
134
135/// An inductive range check is conditional branch in a loop with
136///
137/// 1. a very cold successor (i.e. the branch jumps to that successor very
138/// rarely)
139///
140/// and
141///
142/// 2. a condition that is provably true for some contiguous range of values
143/// taken by the containing loop's induction variable.
144///
145class InductiveRangeCheck {
146
147 const SCEV *Begin = nullptr;
148 const SCEV *Step = nullptr;
149 const SCEV *End = nullptr;
150 Use *CheckUse = nullptr;
151
152 static bool parseRangeCheckICmp(Loop *L, ICmpInst *ICI, ScalarEvolution &SE,
153 const SCEVAddRecExpr *&Index,
154 const SCEV *&End);
155
156 static void
157 extractRangeChecksFromCond(Loop *L, ScalarEvolution &SE, Use &ConditionUse,
159 SmallPtrSetImpl<Value *> &Visited);
160
161 static bool parseIvAgaisntLimit(Loop *L, Value *LHS, Value *RHS,
163 const SCEVAddRecExpr *&Index,
164 const SCEV *&End);
165
166 static bool reassociateSubLHS(Loop *L, Value *VariantLHS, Value *InvariantRHS,
168 const SCEVAddRecExpr *&Index, const SCEV *&End);
169
170public:
171 const SCEV *getBegin() const { return Begin; }
172 const SCEV *getStep() const { return Step; }
173 const SCEV *getEnd() const { return End; }
174
175 void print(raw_ostream &OS) const {
176 OS << "InductiveRangeCheck:\n";
177 OS << " Begin: ";
178 Begin->print(OS);
179 OS << " Step: ";
180 Step->print(OS);
181 OS << " End: ";
182 End->print(OS);
183 OS << "\n CheckUse: ";
184 getCheckUse()->getUser()->print(OS);
185 OS << " Operand: " << getCheckUse()->getOperandNo() << "\n";
186 }
187
189 void dump() {
190 print(dbgs());
191 }
192
193 Use *getCheckUse() const { return CheckUse; }
194
195 /// Represents an signed integer range [Range.getBegin(), Range.getEnd()). If
196 /// R.getEnd() le R.getBegin(), then R denotes the empty range.
197
198 class Range {
199 const SCEV *Begin;
200 const SCEV *End;
201
202 public:
203 Range(const SCEV *Begin, const SCEV *End) : Begin(Begin), End(End) {
204 assert(Begin->getType() == End->getType() && "ill-typed range!");
205 }
206
207 Type *getType() const { return Begin->getType(); }
208 const SCEV *getBegin() const { return Begin; }
209 const SCEV *getEnd() const { return End; }
210 bool isEmpty(ScalarEvolution &SE, bool IsSigned) const {
211 if (Begin == End)
212 return true;
213 if (IsSigned)
214 return SE.isKnownPredicate(ICmpInst::ICMP_SGE, Begin, End);
215 else
216 return SE.isKnownPredicate(ICmpInst::ICMP_UGE, Begin, End);
217 }
218 };
219
220 /// This is the value the condition of the branch needs to evaluate to for the
221 /// branch to take the hot successor (see (1) above).
222 bool getPassingDirection() { return true; }
223
224 /// Computes a range for the induction variable (IndVar) in which the range
225 /// check is redundant and can be constant-folded away. The induction
226 /// variable is not required to be the canonical {0,+,1} induction variable.
227 std::optional<Range> computeSafeIterationSpace(ScalarEvolution &SE,
228 const SCEVAddRecExpr *IndVar,
229 bool IsLatchSigned) const;
230
231 /// Parse out a set of inductive range checks from \p BI and append them to \p
232 /// Checks.
233 ///
234 /// NB! There may be conditions feeding into \p BI that aren't inductive range
235 /// checks, and hence don't end up in \p Checks.
236 static void extractRangeChecksFromBranch(
238 SmallVectorImpl<InductiveRangeCheck> &Checks, bool &Changed);
239};
240
241class InductiveRangeCheckElimination {
242 ScalarEvolution &SE;
244 DominatorTree &DT;
245 LoopInfo &LI;
246
247 using GetBFIFunc =
249 GetBFIFunc GetBFI;
250
251 // Returns true if it is profitable to do a transform basing on estimation of
252 // number of iterations.
253 bool isProfitableToTransform(const Loop &L, LoopStructure &LS);
254
255public:
256 InductiveRangeCheckElimination(ScalarEvolution &SE,
258 LoopInfo &LI, GetBFIFunc GetBFI = std::nullopt)
259 : SE(SE), BPI(BPI), DT(DT), LI(LI), GetBFI(GetBFI) {}
260
261 bool run(Loop *L, function_ref<void(Loop *, bool)> LPMAddNewLoop);
262};
263
264} // end anonymous namespace
265
266/// Parse a single ICmp instruction, `ICI`, into a range check. If `ICI` cannot
267/// be interpreted as a range check, return false. Otherwise set `Index` to the
268/// SCEV being range checked, and set `End` to the upper or lower limit `Index`
269/// is being range checked.
270bool InductiveRangeCheck::parseRangeCheckICmp(Loop *L, ICmpInst *ICI,
271 ScalarEvolution &SE,
272 const SCEVAddRecExpr *&Index,
273 const SCEV *&End) {
274 auto IsLoopInvariant = [&SE, L](Value *V) {
275 return SE.isLoopInvariant(SE.getSCEV(V), L);
276 };
277
278 ICmpInst::Predicate Pred = ICI->getPredicate();
279 Value *LHS = ICI->getOperand(0);
280 Value *RHS = ICI->getOperand(1);
281
282 // Canonicalize to the `Index Pred Invariant` comparison
283 if (IsLoopInvariant(LHS)) {
284 std::swap(LHS, RHS);
285 Pred = CmpInst::getSwappedPredicate(Pred);
286 } else if (!IsLoopInvariant(RHS))
287 // Both LHS and RHS are loop variant
288 return false;
289
290 if (parseIvAgaisntLimit(L, LHS, RHS, Pred, SE, Index, End))
291 return true;
292
293 if (reassociateSubLHS(L, LHS, RHS, Pred, SE, Index, End))
294 return true;
295
296 // TODO: support ReassociateAddLHS
297 return false;
298}
299
300// Try to parse range check in the form of "IV vs Limit"
301bool InductiveRangeCheck::parseIvAgaisntLimit(Loop *L, Value *LHS, Value *RHS,
303 ScalarEvolution &SE,
304 const SCEVAddRecExpr *&Index,
305 const SCEV *&End) {
306
307 auto SIntMaxSCEV = [&](Type *T) {
308 unsigned BitWidth = cast<IntegerType>(T)->getBitWidth();
310 };
311
312 const auto *AddRec = dyn_cast<SCEVAddRecExpr>(SE.getSCEV(LHS));
313 if (!AddRec)
314 return false;
315
316 // We strengthen "0 <= I" to "0 <= I < INT_SMAX" and "I < L" to "0 <= I < L".
317 // We can potentially do much better here.
318 // If we want to adjust upper bound for the unsigned range check as we do it
319 // for signed one, we will need to pick Unsigned max
320 switch (Pred) {
321 default:
322 return false;
323
324 case ICmpInst::ICMP_SGE:
325 if (match(RHS, m_ConstantInt<0>())) {
326 Index = AddRec;
327 End = SIntMaxSCEV(Index->getType());
328 return true;
329 }
330 return false;
331
332 case ICmpInst::ICMP_SGT:
333 if (match(RHS, m_ConstantInt<-1>())) {
334 Index = AddRec;
335 End = SIntMaxSCEV(Index->getType());
336 return true;
337 }
338 return false;
339
340 case ICmpInst::ICMP_SLT:
341 case ICmpInst::ICMP_ULT:
342 Index = AddRec;
343 End = SE.getSCEV(RHS);
344 return true;
345
346 case ICmpInst::ICMP_SLE:
347 case ICmpInst::ICMP_ULE:
348 const SCEV *One = SE.getOne(RHS->getType());
349 const SCEV *RHSS = SE.getSCEV(RHS);
350 bool Signed = Pred == ICmpInst::ICMP_SLE;
351 if (SE.willNotOverflow(Instruction::BinaryOps::Add, Signed, RHSS, One)) {
352 Index = AddRec;
353 End = SE.getAddExpr(RHSS, One);
354 return true;
355 }
356 return false;
357 }
358
359 llvm_unreachable("default clause returns!");
360}
361
362// Try to parse range check in the form of "IV - Offset vs Limit" or "Offset -
363// IV vs Limit"
364bool InductiveRangeCheck::reassociateSubLHS(
365 Loop *L, Value *VariantLHS, Value *InvariantRHS, ICmpInst::Predicate Pred,
366 ScalarEvolution &SE, const SCEVAddRecExpr *&Index, const SCEV *&End) {
367 Value *LHS, *RHS;
368 if (!match(VariantLHS, m_Sub(m_Value(LHS), m_Value(RHS))))
369 return false;
370
371 const SCEV *IV = SE.getSCEV(LHS);
372 const SCEV *Offset = SE.getSCEV(RHS);
373 const SCEV *Limit = SE.getSCEV(InvariantRHS);
374
375 bool OffsetSubtracted = false;
376 if (SE.isLoopInvariant(IV, L))
377 // "Offset - IV vs Limit"
379 else if (SE.isLoopInvariant(Offset, L))
380 // "IV - Offset vs Limit"
381 OffsetSubtracted = true;
382 else
383 return false;
384
385 const auto *AddRec = dyn_cast<SCEVAddRecExpr>(IV);
386 if (!AddRec)
387 return false;
388
389 // In order to turn "IV - Offset < Limit" into "IV < Limit + Offset", we need
390 // to be able to freely move values from left side of inequality to right side
391 // (just as in normal linear arithmetics). Overflows make things much more
392 // complicated, so we want to avoid this.
393 //
394 // Let's prove that the initial subtraction doesn't overflow with all IV's
395 // values from the safe range constructed for that check.
396 //
397 // [Case 1] IV - Offset < Limit
398 // It doesn't overflow if:
399 // SINT_MIN <= IV - Offset <= SINT_MAX
400 // In terms of scaled SINT we need to prove:
401 // SINT_MIN + Offset <= IV <= SINT_MAX + Offset
402 // Safe range will be constructed:
403 // 0 <= IV < Limit + Offset
404 // It means that 'IV - Offset' doesn't underflow, because:
405 // SINT_MIN + Offset < 0 <= IV
406 // and doesn't overflow:
407 // IV < Limit + Offset <= SINT_MAX + Offset
408 //
409 // [Case 2] Offset - IV > Limit
410 // It doesn't overflow if:
411 // SINT_MIN <= Offset - IV <= SINT_MAX
412 // In terms of scaled SINT we need to prove:
413 // -SINT_MIN >= IV - Offset >= -SINT_MAX
414 // Offset - SINT_MIN >= IV >= Offset - SINT_MAX
415 // Safe range will be constructed:
416 // 0 <= IV < Offset - Limit
417 // It means that 'Offset - IV' doesn't underflow, because
418 // Offset - SINT_MAX < 0 <= IV
419 // and doesn't overflow:
420 // IV < Offset - Limit <= Offset - SINT_MIN
421 //
422 // For the computed upper boundary of the IV's range (Offset +/- Limit) we
423 // don't know exactly whether it overflows or not. So if we can't prove this
424 // fact at compile time, we scale boundary computations to a wider type with
425 // the intention to add runtime overflow check.
426
427 auto getExprScaledIfOverflow = [&](Instruction::BinaryOps BinOp,
428 const SCEV *LHS,
429 const SCEV *RHS) -> const SCEV * {
430 const SCEV *(ScalarEvolution::*Operation)(const SCEV *, const SCEV *,
431 SCEV::NoWrapFlags, unsigned);
432 switch (BinOp) {
433 default:
434 llvm_unreachable("Unsupported binary op");
435 case Instruction::Add:
437 break;
438 case Instruction::Sub:
440 break;
441 }
442
443 if (SE.willNotOverflow(BinOp, ICmpInst::isSigned(Pred), LHS, RHS,
444 cast<Instruction>(VariantLHS)))
445 return (SE.*Operation)(LHS, RHS, SCEV::FlagAnyWrap, 0);
446
447 // We couldn't prove that the expression does not overflow.
448 // Than scale it to a wider type to check overflow at runtime.
449 auto *Ty = cast<IntegerType>(LHS->getType());
450 if (Ty->getBitWidth() > MaxTypeSizeForOverflowCheck)
451 return nullptr;
452
453 auto WideTy = IntegerType::get(Ty->getContext(), Ty->getBitWidth() * 2);
454 return (SE.*Operation)(SE.getSignExtendExpr(LHS, WideTy),
455 SE.getSignExtendExpr(RHS, WideTy), SCEV::FlagAnyWrap,
456 0);
457 };
458
459 if (OffsetSubtracted)
460 // "IV - Offset < Limit" -> "IV" < Offset + Limit
461 Limit = getExprScaledIfOverflow(Instruction::BinaryOps::Add, Offset, Limit);
462 else {
463 // "Offset - IV > Limit" -> "IV" < Offset - Limit
464 Limit = getExprScaledIfOverflow(Instruction::BinaryOps::Sub, Offset, Limit);
465 Pred = ICmpInst::getSwappedPredicate(Pred);
466 }
467
468 if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE) {
469 // "Expr <= Limit" -> "Expr < Limit + 1"
470 if (Pred == ICmpInst::ICMP_SLE && Limit)
471 Limit = getExprScaledIfOverflow(Instruction::BinaryOps::Add, Limit,
472 SE.getOne(Limit->getType()));
473 if (Limit) {
474 Index = AddRec;
475 End = Limit;
476 return true;
477 }
478 }
479 return false;
480}
481
482void InductiveRangeCheck::extractRangeChecksFromCond(
483 Loop *L, ScalarEvolution &SE, Use &ConditionUse,
485 SmallPtrSetImpl<Value *> &Visited) {
486 Value *Condition = ConditionUse.get();
487 if (!Visited.insert(Condition).second)
488 return;
489
490 // TODO: Do the same for OR, XOR, NOT etc?
491 if (match(Condition, m_LogicalAnd(m_Value(), m_Value()))) {
492 extractRangeChecksFromCond(L, SE, cast<User>(Condition)->getOperandUse(0),
493 Checks, Visited);
494 extractRangeChecksFromCond(L, SE, cast<User>(Condition)->getOperandUse(1),
495 Checks, Visited);
496 return;
497 }
498
499 ICmpInst *ICI = dyn_cast<ICmpInst>(Condition);
500 if (!ICI)
501 return;
502
503 const SCEV *End = nullptr;
504 const SCEVAddRecExpr *IndexAddRec = nullptr;
505 if (!parseRangeCheckICmp(L, ICI, SE, IndexAddRec, End))
506 return;
507
508 assert(IndexAddRec && "IndexAddRec was not computed");
509 assert(End && "End was not computed");
510
511 if ((IndexAddRec->getLoop() != L) || !IndexAddRec->isAffine())
512 return;
513
514 InductiveRangeCheck IRC;
515 IRC.End = End;
516 IRC.Begin = IndexAddRec->getStart();
517 IRC.Step = IndexAddRec->getStepRecurrence(SE);
518 IRC.CheckUse = &ConditionUse;
519 Checks.push_back(IRC);
520}
521
522void InductiveRangeCheck::extractRangeChecksFromBranch(
524 SmallVectorImpl<InductiveRangeCheck> &Checks, bool &Changed) {
525 if (BI->isUnconditional() || BI->getParent() == L->getLoopLatch())
526 return;
527
528 unsigned IndexLoopSucc = L->contains(BI->getSuccessor(0)) ? 0 : 1;
529 assert(L->contains(BI->getSuccessor(IndexLoopSucc)) &&
530 "No edges coming to loop?");
531 BranchProbability LikelyTaken(15, 16);
532
533 if (!SkipProfitabilityChecks && BPI &&
534 BPI->getEdgeProbability(BI->getParent(), IndexLoopSucc) < LikelyTaken)
535 return;
536
537 // IRCE expects branch's true edge comes to loop. Invert branch for opposite
538 // case.
539 if (IndexLoopSucc != 0) {
540 IRBuilder<> Builder(BI);
541 InvertBranch(BI, Builder);
542 if (BPI)
544 Changed = true;
545 }
546
548 InductiveRangeCheck::extractRangeChecksFromCond(L, SE, BI->getOperandUse(0),
549 Checks, Visited);
550}
551
552/// If the type of \p S matches with \p Ty, return \p S. Otherwise, return
553/// signed or unsigned extension of \p S to type \p Ty.
554static const SCEV *NoopOrExtend(const SCEV *S, Type *Ty, ScalarEvolution &SE,
555 bool Signed) {
556 return Signed ? SE.getNoopOrSignExtend(S, Ty) : SE.getNoopOrZeroExtend(S, Ty);
557}
558
559// Compute a safe set of limits for the main loop to run in -- effectively the
560// intersection of `Range' and the iteration space of the original loop.
561// Return std::nullopt if unable to compute the set of subranges.
562static std::optional<LoopConstrainer::SubRanges>
564 InductiveRangeCheck::Range &Range,
565 const LoopStructure &MainLoopStructure) {
566 auto *RTy = cast<IntegerType>(Range.getType());
567 // We only support wide range checks and narrow latches.
568 if (!AllowNarrowLatchCondition && RTy != MainLoopStructure.ExitCountTy)
569 return std::nullopt;
570 if (RTy->getBitWidth() < MainLoopStructure.ExitCountTy->getBitWidth())
571 return std::nullopt;
572
574
575 bool IsSignedPredicate = MainLoopStructure.IsSignedPredicate;
576 // I think we can be more aggressive here and make this nuw / nsw if the
577 // addition that feeds into the icmp for the latch's terminating branch is nuw
578 // / nsw. In any case, a wrapping 2's complement addition is safe.
579 const SCEV *Start = NoopOrExtend(SE.getSCEV(MainLoopStructure.IndVarStart),
580 RTy, SE, IsSignedPredicate);
581 const SCEV *End = NoopOrExtend(SE.getSCEV(MainLoopStructure.LoopExitAt), RTy,
582 SE, IsSignedPredicate);
583
584 bool Increasing = MainLoopStructure.IndVarIncreasing;
585
586 // We compute `Smallest` and `Greatest` such that [Smallest, Greatest), or
587 // [Smallest, GreatestSeen] is the range of values the induction variable
588 // takes.
589
590 const SCEV *Smallest = nullptr, *Greatest = nullptr, *GreatestSeen = nullptr;
591
592 const SCEV *One = SE.getOne(RTy);
593 if (Increasing) {
594 Smallest = Start;
595 Greatest = End;
596 // No overflow, because the range [Smallest, GreatestSeen] is not empty.
597 GreatestSeen = SE.getMinusSCEV(End, One);
598 } else {
599 // These two computations may sign-overflow. Here is why that is okay:
600 //
601 // We know that the induction variable does not sign-overflow on any
602 // iteration except the last one, and it starts at `Start` and ends at
603 // `End`, decrementing by one every time.
604 //
605 // * if `Smallest` sign-overflows we know `End` is `INT_SMAX`. Since the
606 // induction variable is decreasing we know that the smallest value
607 // the loop body is actually executed with is `INT_SMIN` == `Smallest`.
608 //
609 // * if `Greatest` sign-overflows, we know it can only be `INT_SMIN`. In
610 // that case, `Clamp` will always return `Smallest` and
611 // [`Result.LowLimit`, `Result.HighLimit`) = [`Smallest`, `Smallest`)
612 // will be an empty range. Returning an empty range is always safe.
613
614 Smallest = SE.getAddExpr(End, One);
615 Greatest = SE.getAddExpr(Start, One);
616 GreatestSeen = Start;
617 }
618
619 auto Clamp = [&SE, Smallest, Greatest, IsSignedPredicate](const SCEV *S) {
620 return IsSignedPredicate
621 ? SE.getSMaxExpr(Smallest, SE.getSMinExpr(Greatest, S))
622 : SE.getUMaxExpr(Smallest, SE.getUMinExpr(Greatest, S));
623 };
624
625 // In some cases we can prove that we don't need a pre or post loop.
626 ICmpInst::Predicate PredLE =
627 IsSignedPredicate ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE;
628 ICmpInst::Predicate PredLT =
629 IsSignedPredicate ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
630
631 bool ProvablyNoPreloop =
632 SE.isKnownPredicate(PredLE, Range.getBegin(), Smallest);
633 if (!ProvablyNoPreloop)
634 Result.LowLimit = Clamp(Range.getBegin());
635
636 bool ProvablyNoPostLoop =
637 SE.isKnownPredicate(PredLT, GreatestSeen, Range.getEnd());
638 if (!ProvablyNoPostLoop)
639 Result.HighLimit = Clamp(Range.getEnd());
640
641 return Result;
642}
643
644/// Computes and returns a range of values for the induction variable (IndVar)
645/// in which the range check can be safely elided. If it cannot compute such a
646/// range, returns std::nullopt.
647std::optional<InductiveRangeCheck::Range>
648InductiveRangeCheck::computeSafeIterationSpace(ScalarEvolution &SE,
649 const SCEVAddRecExpr *IndVar,
650 bool IsLatchSigned) const {
651 // We can deal when types of latch check and range checks don't match in case
652 // if latch check is more narrow.
653 auto *IVType = dyn_cast<IntegerType>(IndVar->getType());
654 auto *RCType = dyn_cast<IntegerType>(getBegin()->getType());
655 auto *EndType = dyn_cast<IntegerType>(getEnd()->getType());
656 // Do not work with pointer types.
657 if (!IVType || !RCType)
658 return std::nullopt;
659 if (IVType->getBitWidth() > RCType->getBitWidth())
660 return std::nullopt;
661
662 // IndVar is of the form "A + B * I" (where "I" is the canonical induction
663 // variable, that may or may not exist as a real llvm::Value in the loop) and
664 // this inductive range check is a range check on the "C + D * I" ("C" is
665 // getBegin() and "D" is getStep()). We rewrite the value being range
666 // checked to "M + N * IndVar" where "N" = "D * B^(-1)" and "M" = "C - NA".
667 //
668 // The actual inequalities we solve are of the form
669 //
670 // 0 <= M + 1 * IndVar < L given L >= 0 (i.e. N == 1)
671 //
672 // Here L stands for upper limit of the safe iteration space.
673 // The inequality is satisfied by (0 - M) <= IndVar < (L - M). To avoid
674 // overflows when calculating (0 - M) and (L - M) we, depending on type of
675 // IV's iteration space, limit the calculations by borders of the iteration
676 // space. For example, if IndVar is unsigned, (0 - M) overflows for any M > 0.
677 // If we figured out that "anything greater than (-M) is safe", we strengthen
678 // this to "everything greater than 0 is safe", assuming that values between
679 // -M and 0 just do not exist in unsigned iteration space, and we don't want
680 // to deal with overflown values.
681
682 if (!IndVar->isAffine())
683 return std::nullopt;
684
685 const SCEV *A = NoopOrExtend(IndVar->getStart(), RCType, SE, IsLatchSigned);
686 const SCEVConstant *B = dyn_cast<SCEVConstant>(
687 NoopOrExtend(IndVar->getStepRecurrence(SE), RCType, SE, IsLatchSigned));
688 if (!B)
689 return std::nullopt;
690 assert(!B->isZero() && "Recurrence with zero step?");
691
692 const SCEV *C = getBegin();
693 const SCEVConstant *D = dyn_cast<SCEVConstant>(getStep());
694 if (D != B)
695 return std::nullopt;
696
697 assert(!D->getValue()->isZero() && "Recurrence with zero step?");
698 unsigned BitWidth = RCType->getBitWidth();
701
702 // Subtract Y from X so that it does not go through border of the IV
703 // iteration space. Mathematically, it is equivalent to:
704 //
705 // ClampedSubtract(X, Y) = min(max(X - Y, INT_MIN), INT_MAX). [1]
706 //
707 // In [1], 'X - Y' is a mathematical subtraction (result is not bounded to
708 // any width of bit grid). But after we take min/max, the result is
709 // guaranteed to be within [INT_MIN, INT_MAX].
710 //
711 // In [1], INT_MAX and INT_MIN are respectively signed and unsigned max/min
712 // values, depending on type of latch condition that defines IV iteration
713 // space.
714 auto ClampedSubtract = [&](const SCEV *X, const SCEV *Y) {
715 // FIXME: The current implementation assumes that X is in [0, SINT_MAX].
716 // This is required to ensure that SINT_MAX - X does not overflow signed and
717 // that X - Y does not overflow unsigned if Y is negative. Can we lift this
718 // restriction and make it work for negative X either?
719 if (IsLatchSigned) {
720 // X is a number from signed range, Y is interpreted as signed.
721 // Even if Y is SINT_MAX, (X - Y) does not reach SINT_MIN. So the only
722 // thing we should care about is that we didn't cross SINT_MAX.
723 // So, if Y is positive, we subtract Y safely.
724 // Rule 1: Y > 0 ---> Y.
725 // If 0 <= -Y <= (SINT_MAX - X), we subtract Y safely.
726 // Rule 2: Y >=s (X - SINT_MAX) ---> Y.
727 // If 0 <= (SINT_MAX - X) < -Y, we can only subtract (X - SINT_MAX).
728 // Rule 3: Y <s (X - SINT_MAX) ---> (X - SINT_MAX).
729 // It gives us smax(Y, X - SINT_MAX) to subtract in all cases.
730 const SCEV *XMinusSIntMax = SE.getMinusSCEV(X, SIntMax);
731 return SE.getMinusSCEV(X, SE.getSMaxExpr(Y, XMinusSIntMax),
733 } else
734 // X is a number from unsigned range, Y is interpreted as signed.
735 // Even if Y is SINT_MIN, (X - Y) does not reach UINT_MAX. So the only
736 // thing we should care about is that we didn't cross zero.
737 // So, if Y is negative, we subtract Y safely.
738 // Rule 1: Y <s 0 ---> Y.
739 // If 0 <= Y <= X, we subtract Y safely.
740 // Rule 2: Y <=s X ---> Y.
741 // If 0 <= X < Y, we should stop at 0 and can only subtract X.
742 // Rule 3: Y >s X ---> X.
743 // It gives us smin(X, Y) to subtract in all cases.
744 return SE.getMinusSCEV(X, SE.getSMinExpr(X, Y), SCEV::FlagNUW);
745 };
746 const SCEV *M = SE.getMinusSCEV(C, A);
747 const SCEV *Zero = SE.getZero(M->getType());
748
749 // This function returns SCEV equal to 1 if X is non-negative 0 otherwise.
750 auto SCEVCheckNonNegative = [&](const SCEV *X) {
751 const Loop *L = IndVar->getLoop();
752 const SCEV *Zero = SE.getZero(X->getType());
753 const SCEV *One = SE.getOne(X->getType());
754 // Can we trivially prove that X is a non-negative or negative value?
755 if (isKnownNonNegativeInLoop(X, L, SE))
756 return One;
757 else if (isKnownNegativeInLoop(X, L, SE))
758 return Zero;
759 // If not, we will have to figure it out during the execution.
760 // Function smax(smin(X, 0), -1) + 1 equals to 1 if X >= 0 and 0 if X < 0.
761 const SCEV *NegOne = SE.getNegativeSCEV(One);
762 return SE.getAddExpr(SE.getSMaxExpr(SE.getSMinExpr(X, Zero), NegOne), One);
763 };
764
765 // This function returns SCEV equal to 1 if X will not overflow in terms of
766 // range check type, 0 otherwise.
767 auto SCEVCheckWillNotOverflow = [&](const SCEV *X) {
768 // X doesn't overflow if SINT_MAX >= X.
769 // Then if (SINT_MAX - X) >= 0, X doesn't overflow
770 const SCEV *SIntMaxExt = SE.getSignExtendExpr(SIntMax, X->getType());
771 const SCEV *OverflowCheck =
772 SCEVCheckNonNegative(SE.getMinusSCEV(SIntMaxExt, X));
773
774 // X doesn't underflow if X >= SINT_MIN.
775 // Then if (X - SINT_MIN) >= 0, X doesn't underflow
776 const SCEV *SIntMinExt = SE.getSignExtendExpr(SIntMin, X->getType());
777 const SCEV *UnderflowCheck =
778 SCEVCheckNonNegative(SE.getMinusSCEV(X, SIntMinExt));
779
780 return SE.getMulExpr(OverflowCheck, UnderflowCheck);
781 };
782
783 // FIXME: Current implementation of ClampedSubtract implicitly assumes that
784 // X is non-negative (in sense of a signed value). We need to re-implement
785 // this function in a way that it will correctly handle negative X as well.
786 // We use it twice: for X = 0 everything is fine, but for X = getEnd() we can
787 // end up with a negative X and produce wrong results. So currently we ensure
788 // that if getEnd() is negative then both ends of the safe range are zero.
789 // Note that this may pessimize elimination of unsigned range checks against
790 // negative values.
791 const SCEV *REnd = getEnd();
792 const SCEV *EndWillNotOverflow = SE.getOne(RCType);
793
794 auto PrintRangeCheck = [&](raw_ostream &OS) {
795 auto L = IndVar->getLoop();
796 OS << "irce: in function ";
797 OS << L->getHeader()->getParent()->getName();
798 OS << ", in ";
799 L->print(OS);
800 OS << "there is range check with scaled boundary:\n";
801 print(OS);
802 };
803
804 if (EndType->getBitWidth() > RCType->getBitWidth()) {
805 assert(EndType->getBitWidth() == RCType->getBitWidth() * 2);
807 PrintRangeCheck(errs());
808 // End is computed with extended type but will be truncated to a narrow one
809 // type of range check. Therefore we need a check that the result will not
810 // overflow in terms of narrow type.
811 EndWillNotOverflow =
812 SE.getTruncateExpr(SCEVCheckWillNotOverflow(REnd), RCType);
813 REnd = SE.getTruncateExpr(REnd, RCType);
814 }
815
816 const SCEV *RuntimeChecks =
817 SE.getMulExpr(SCEVCheckNonNegative(REnd), EndWillNotOverflow);
818 const SCEV *Begin = SE.getMulExpr(ClampedSubtract(Zero, M), RuntimeChecks);
819 const SCEV *End = SE.getMulExpr(ClampedSubtract(REnd, M), RuntimeChecks);
820
821 return InductiveRangeCheck::Range(Begin, End);
822}
823
824static std::optional<InductiveRangeCheck::Range>
826 const std::optional<InductiveRangeCheck::Range> &R1,
827 const InductiveRangeCheck::Range &R2) {
828 if (R2.isEmpty(SE, /* IsSigned */ true))
829 return std::nullopt;
830 if (!R1)
831 return R2;
832 auto &R1Value = *R1;
833 // We never return empty ranges from this function, and R1 is supposed to be
834 // a result of intersection. Thus, R1 is never empty.
835 assert(!R1Value.isEmpty(SE, /* IsSigned */ true) &&
836 "We should never have empty R1!");
837
838 // TODO: we could widen the smaller range and have this work; but for now we
839 // bail out to keep things simple.
840 if (R1Value.getType() != R2.getType())
841 return std::nullopt;
842
843 const SCEV *NewBegin = SE.getSMaxExpr(R1Value.getBegin(), R2.getBegin());
844 const SCEV *NewEnd = SE.getSMinExpr(R1Value.getEnd(), R2.getEnd());
845
846 // If the resulting range is empty, just return std::nullopt.
847 auto Ret = InductiveRangeCheck::Range(NewBegin, NewEnd);
848 if (Ret.isEmpty(SE, /* IsSigned */ true))
849 return std::nullopt;
850 return Ret;
851}
852
853static std::optional<InductiveRangeCheck::Range>
855 const std::optional<InductiveRangeCheck::Range> &R1,
856 const InductiveRangeCheck::Range &R2) {
857 if (R2.isEmpty(SE, /* IsSigned */ false))
858 return std::nullopt;
859 if (!R1)
860 return R2;
861 auto &R1Value = *R1;
862 // We never return empty ranges from this function, and R1 is supposed to be
863 // a result of intersection. Thus, R1 is never empty.
864 assert(!R1Value.isEmpty(SE, /* IsSigned */ false) &&
865 "We should never have empty R1!");
866
867 // TODO: we could widen the smaller range and have this work; but for now we
868 // bail out to keep things simple.
869 if (R1Value.getType() != R2.getType())
870 return std::nullopt;
871
872 const SCEV *NewBegin = SE.getUMaxExpr(R1Value.getBegin(), R2.getBegin());
873 const SCEV *NewEnd = SE.getUMinExpr(R1Value.getEnd(), R2.getEnd());
874
875 // If the resulting range is empty, just return std::nullopt.
876 auto Ret = InductiveRangeCheck::Range(NewBegin, NewEnd);
877 if (Ret.isEmpty(SE, /* IsSigned */ false))
878 return std::nullopt;
879 return Ret;
880}
881
883 auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
884 LoopInfo &LI = AM.getResult<LoopAnalysis>(F);
885 // There are no loops in the function. Return before computing other expensive
886 // analyses.
887 if (LI.empty())
888 return PreservedAnalyses::all();
889 auto &SE = AM.getResult<ScalarEvolutionAnalysis>(F);
890 auto &BPI = AM.getResult<BranchProbabilityAnalysis>(F);
891
892 // Get BFI analysis result on demand. Please note that modification of
893 // CFG invalidates this analysis and we should handle it.
894 auto getBFI = [&F, &AM ]()->BlockFrequencyInfo & {
896 };
897 InductiveRangeCheckElimination IRCE(SE, &BPI, DT, LI, { getBFI });
898
899 bool Changed = false;
900 {
901 bool CFGChanged = false;
902 for (const auto &L : LI) {
903 CFGChanged |= simplifyLoop(L, &DT, &LI, &SE, nullptr, nullptr,
904 /*PreserveLCSSA=*/false);
905 Changed |= formLCSSARecursively(*L, DT, &LI, &SE);
906 }
907 Changed |= CFGChanged;
908
909 if (CFGChanged && !SkipProfitabilityChecks) {
912 AM.invalidate(F, PA);
913 }
914 }
915
917 appendLoopsToWorklist(LI, Worklist);
918 auto LPMAddNewLoop = [&Worklist](Loop *NL, bool IsSubloop) {
919 if (!IsSubloop)
920 appendLoopsToWorklist(*NL, Worklist);
921 };
922
923 while (!Worklist.empty()) {
924 Loop *L = Worklist.pop_back_val();
925 if (IRCE.run(L, LPMAddNewLoop)) {
926 Changed = true;
930 AM.invalidate(F, PA);
931 }
932 }
933 }
934
935 if (!Changed)
936 return PreservedAnalyses::all();
938}
939
940bool
941InductiveRangeCheckElimination::isProfitableToTransform(const Loop &L,
942 LoopStructure &LS) {
944 return true;
945 if (GetBFI) {
946 BlockFrequencyInfo &BFI = (*GetBFI)();
947 uint64_t hFreq = BFI.getBlockFreq(LS.Header).getFrequency();
948 uint64_t phFreq = BFI.getBlockFreq(L.getLoopPreheader()).getFrequency();
949 if (phFreq != 0 && hFreq != 0 && (hFreq / phFreq < MinRuntimeIterations)) {
950 LLVM_DEBUG(dbgs() << "irce: could not prove profitability: "
951 << "the estimated number of iterations basing on "
952 "frequency info is " << (hFreq / phFreq) << "\n";);
953 return false;
954 }
955 return true;
956 }
957
958 if (!BPI)
959 return true;
960 BranchProbability ExitProbability =
961 BPI->getEdgeProbability(LS.Latch, LS.LatchBrExitIdx);
962 if (ExitProbability > BranchProbability(1, MinRuntimeIterations)) {
963 LLVM_DEBUG(dbgs() << "irce: could not prove profitability: "
964 << "the exit probability is too big " << ExitProbability
965 << "\n";);
966 return false;
967 }
968 return true;
969}
970
971bool InductiveRangeCheckElimination::run(
972 Loop *L, function_ref<void(Loop *, bool)> LPMAddNewLoop) {
973 if (L->getBlocks().size() >= LoopSizeCutoff) {
974 LLVM_DEBUG(dbgs() << "irce: giving up constraining loop, too large\n");
975 return false;
976 }
977
978 BasicBlock *Preheader = L->getLoopPreheader();
979 if (!Preheader) {
980 LLVM_DEBUG(dbgs() << "irce: loop has no preheader, leaving\n");
981 return false;
982 }
983
984 LLVMContext &Context = Preheader->getContext();
986 bool Changed = false;
987
988 for (auto *BBI : L->getBlocks())
989 if (BranchInst *TBI = dyn_cast<BranchInst>(BBI->getTerminator()))
990 InductiveRangeCheck::extractRangeChecksFromBranch(TBI, L, SE, BPI,
991 RangeChecks, Changed);
992
993 if (RangeChecks.empty())
994 return Changed;
995
996 auto PrintRecognizedRangeChecks = [&](raw_ostream &OS) {
997 OS << "irce: looking at loop "; L->print(OS);
998 OS << "irce: loop has " << RangeChecks.size()
999 << " inductive range checks: \n";
1000 for (InductiveRangeCheck &IRC : RangeChecks)
1001 IRC.print(OS);
1002 };
1003
1004 LLVM_DEBUG(PrintRecognizedRangeChecks(dbgs()));
1005
1006 if (PrintRangeChecks)
1007 PrintRecognizedRangeChecks(errs());
1008
1009 const char *FailureReason = nullptr;
1010 std::optional<LoopStructure> MaybeLoopStructure =
1012 FailureReason);
1013 if (!MaybeLoopStructure) {
1014 LLVM_DEBUG(dbgs() << "irce: could not parse loop structure: "
1015 << FailureReason << "\n";);
1016 return Changed;
1017 }
1018 LoopStructure LS = *MaybeLoopStructure;
1019 if (!isProfitableToTransform(*L, LS))
1020 return Changed;
1021 const SCEVAddRecExpr *IndVar =
1022 cast<SCEVAddRecExpr>(SE.getMinusSCEV(SE.getSCEV(LS.IndVarBase), SE.getSCEV(LS.IndVarStep)));
1023
1024 std::optional<InductiveRangeCheck::Range> SafeIterRange;
1025
1026 SmallVector<InductiveRangeCheck, 4> RangeChecksToEliminate;
1027 // Basing on the type of latch predicate, we interpret the IV iteration range
1028 // as signed or unsigned range. We use different min/max functions (signed or
1029 // unsigned) when intersecting this range with safe iteration ranges implied
1030 // by range checks.
1031 auto IntersectRange =
1032 LS.IsSignedPredicate ? IntersectSignedRange : IntersectUnsignedRange;
1033
1034 for (InductiveRangeCheck &IRC : RangeChecks) {
1035 auto Result = IRC.computeSafeIterationSpace(SE, IndVar,
1036 LS.IsSignedPredicate);
1037 if (Result) {
1038 auto MaybeSafeIterRange = IntersectRange(SE, SafeIterRange, *Result);
1039 if (MaybeSafeIterRange) {
1040 assert(!MaybeSafeIterRange->isEmpty(SE, LS.IsSignedPredicate) &&
1041 "We should never return empty ranges!");
1042 RangeChecksToEliminate.push_back(IRC);
1043 SafeIterRange = *MaybeSafeIterRange;
1044 }
1045 }
1046 }
1047
1048 if (!SafeIterRange)
1049 return Changed;
1050
1051 std::optional<LoopConstrainer::SubRanges> MaybeSR =
1052 calculateSubRanges(SE, *L, *SafeIterRange, LS);
1053 if (!MaybeSR) {
1054 LLVM_DEBUG(dbgs() << "irce: could not compute subranges\n");
1055 return false;
1056 }
1057
1058 LoopConstrainer LC(*L, LI, LPMAddNewLoop, LS, SE, DT,
1059 SafeIterRange->getBegin()->getType(), *MaybeSR);
1060
1061 if (LC.run()) {
1062 Changed = true;
1063
1064 auto PrintConstrainedLoopInfo = [L]() {
1065 dbgs() << "irce: in function ";
1066 dbgs() << L->getHeader()->getParent()->getName() << ": ";
1067 dbgs() << "constrained ";
1068 L->print(dbgs());
1069 };
1070
1071 LLVM_DEBUG(PrintConstrainedLoopInfo());
1072
1074 PrintConstrainedLoopInfo();
1075
1076 // Optimize away the now-redundant range checks.
1077
1078 for (InductiveRangeCheck &IRC : RangeChecksToEliminate) {
1079 ConstantInt *FoldedRangeCheck = IRC.getPassingDirection()
1080 ? ConstantInt::getTrue(Context)
1082 IRC.getCheckUse()->set(FoldedRangeCheck);
1083 }
1084 }
1085
1086 return Changed;
1087}
This file implements a class to represent arbitrary precision integral constant values and operations...
static void print(raw_ostream &Out, object::Archive::Kind Kind, T Val)
static GCRegistry::Add< OcamlGC > B("ocaml", "ocaml 3.10-compatible GC")
static GCRegistry::Add< ErlangGC > A("erlang", "erlang-compatible garbage collector")
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:529
This file contains the declarations for the subclasses of Constant, which represent the different fla...
#define LLVM_DEBUG(X)
Definition: Debug.h:101
#define NL
bool End
Definition: ELF_riscv.cpp:480
static GCMetadataPrinterRegistry::Add< ErlangGCPrinter > X("erlang", "erlang-compatible garbage collector")
This file provides various utilities for inspecting and working with the control flow graph in LLVM I...
static const SCEV * NoopOrExtend(const SCEV *S, Type *Ty, ScalarEvolution &SE, bool Signed)
If the type of S matches with Ty, return S.
static cl::opt< bool > PrintRangeChecks("irce-print-range-checks", cl::Hidden, cl::init(false))
static cl::opt< bool > AllowUnsignedLatchCondition("irce-allow-unsigned-latch", cl::Hidden, cl::init(true))
static cl::opt< unsigned > MinRuntimeIterations("irce-min-runtime-iterations", cl::Hidden, cl::init(10))
static cl::opt< unsigned > LoopSizeCutoff("irce-loop-size-cutoff", cl::Hidden, cl::init(64))
static std::optional< InductiveRangeCheck::Range > IntersectSignedRange(ScalarEvolution &SE, const std::optional< InductiveRangeCheck::Range > &R1, const InductiveRangeCheck::Range &R2)
static cl::opt< bool > AllowNarrowLatchCondition("irce-allow-narrow-latch", cl::Hidden, cl::init(true), cl::desc("If set to true, IRCE may eliminate wide range checks in loops " "with narrow latch condition."))
static cl::opt< unsigned > MaxTypeSizeForOverflowCheck("irce-max-type-size-for-overflow-check", cl::Hidden, cl::init(32), cl::desc("Maximum size of range check type for which can be produced runtime " "overflow check of its limit's computation"))
static cl::opt< bool > PrintChangedLoops("irce-print-changed-loops", cl::Hidden, cl::init(false))
static std::optional< InductiveRangeCheck::Range > IntersectUnsignedRange(ScalarEvolution &SE, const std::optional< InductiveRangeCheck::Range > &R1, const InductiveRangeCheck::Range &R2)
static cl::opt< bool > SkipProfitabilityChecks("irce-skip-profitability-checks", cl::Hidden, cl::init(false))
static std::optional< LoopConstrainer::SubRanges > calculateSubRanges(ScalarEvolution &SE, const Loop &L, InductiveRangeCheck::Range &Range, const LoopStructure &MainLoopStructure)
static cl::opt< bool > PrintScaledBoundaryRangeChecks("irce-print-scaled-boundary-range-checks", cl::Hidden, cl::init(false))
static Constant * getFalse(Type *Ty)
For a boolean type or a vector of boolean type, return false or a vector with every element false.
This header provides classes for managing per-loop analyses.
#define F(x, y, z)
Definition: MD5.cpp:55
#define R2(n)
This file contains the declarations for metadata subclasses.
Module.h This file contains the declarations for the Module class.
LLVMContext & Context
static GCMetadataPrinterRegistry::Add< OcamlGCMetadataPrinter > Y("ocaml", "ocaml 3.10-compatible collector")
PowerPC Reduce CR logical Operation
This file provides a priority worklist.
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
raw_pwrite_stream & OS
This file defines the SmallPtrSet class.
This file defines the SmallVector class.
static SymbolRef::Type getType(const Symbol *Sym)
Definition: TapiFile.cpp:40
This defines the Use class.
Value * RHS
Value * LHS
static const uint32_t IV[8]
Definition: blake3_impl.h:78
static APInt getSignedMaxValue(unsigned numBits)
Gets maximum signed value of APInt for a specific bit width.
Definition: APInt.h:187
static APInt getSignedMinValue(unsigned numBits)
Gets minimum signed value of APInt for a specific bit width.
Definition: APInt.h:197
A container for analyses that lazily runs them and caches their results.
Definition: PassManager.h:348
void invalidate(IRUnitT &IR, const PreservedAnalyses &PA)
Invalidate cached analyses for an IR unit.
PassT::Result & getResult(IRUnitT &IR, ExtraArgTs... ExtraArgs)
Get the result of an analysis pass for a given IR unit.
Definition: PassManager.h:500
LLVM Basic Block Representation.
Definition: BasicBlock.h:60
LLVMContext & getContext() const
Get the context in which this basic block lives.
Definition: BasicBlock.cpp:155
Analysis pass which computes BlockFrequencyInfo.
BlockFrequencyInfo pass uses BlockFrequencyInfoImpl implementation to estimate IR basic block frequen...
Conditional or Unconditional Branch instruction.
BasicBlock * getSuccessor(unsigned i) const
bool isUnconditional() const
Analysis pass which computes BranchProbabilityInfo.
Analysis providing branch probability information.
BranchProbability getEdgeProbability(const BasicBlock *Src, unsigned IndexInSuccessors) const
Get an edge's probability, relative to other out-edges of the Src.
void swapSuccEdgesProbabilities(const BasicBlock *Src)
Swap outgoing edges probabilities for Src with branch terminator.
Predicate
This enumeration lists the possible predicates for CmpInst subclasses.
Definition: InstrTypes.h:965
Predicate getSwappedPredicate() const
For example, EQ->EQ, SLE->SGE, ULT->UGT, OEQ->OEQ, ULE->UGE, OLT->OGT, etc.
Definition: InstrTypes.h:1128
Predicate getPredicate() const
Return the predicate for this instruction.
Definition: InstrTypes.h:1066
This is the shared class of boolean and integer constants.
Definition: Constants.h:79
static ConstantInt * getTrue(LLVMContext &Context)
Definition: Constants.cpp:849
Analysis pass which computes a DominatorTree.
Definition: Dominators.h:279
Concrete subclass of DominatorTreeBase that is used to compute a normal dominator tree.
Definition: Dominators.h:162
This instruction compares its operands according to the predicate given to the constructor.
This provides a uniform API for creating instructions and inserting them into a basic block: either a...
Definition: IRBuilder.h:2649
PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM)
const BasicBlock * getParent() const
Definition: Instruction.h:151
static IntegerType * get(LLVMContext &C, unsigned NumBits)
This static method is the primary way of constructing an IntegerType.
Definition: Type.cpp:278
unsigned getBitWidth() const
Get the number of bits in this IntegerType.
Definition: DerivedTypes.h:72
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:566
This class is used to constrain loops to run within a given iteration space.
Represents a single loop in the control flow graph.
Definition: LoopInfo.h:44
A set of analyses that are preserved following a run of a transformation pass.
Definition: Analysis.h:109
static PreservedAnalyses all()
Construct a special preserved set that preserves all passes.
Definition: Analysis.h:115
void abandon()
Mark an analysis as abandoned.
Definition: Analysis.h:162
bool empty() const
Determine if the PriorityWorklist is empty or not.
This node represents a polynomial recurrence on the trip count of the specified loop.
const SCEV * getStepRecurrence(ScalarEvolution &SE) const
Constructs and returns the recurrence indicating how much this expression steps by.
bool isAffine() const
Return true if this represents an expression A + B*x where A and B are loop invariant values.
This class represents a constant integer value.
This class represents an analyzed expression in the program.
void print(raw_ostream &OS) const
Print out the internal representation of this scalar to the specified stream.
Type * getType() const
Return the LLVM type of this SCEV expression.
NoWrapFlags
NoWrapFlags are bitfield indices into SubclassData.
Analysis pass that exposes the ScalarEvolution for a function.
The main scalar evolution driver.
const SCEV * getNegativeSCEV(const SCEV *V, SCEV::NoWrapFlags Flags=SCEV::FlagAnyWrap)
Return the SCEV object corresponding to -V.
const SCEV * getSMaxExpr(const SCEV *LHS, const SCEV *RHS)
const SCEV * getSMinExpr(const SCEV *LHS, const SCEV *RHS)
const SCEV * getUMaxExpr(const SCEV *LHS, const SCEV *RHS)
const SCEV * getZero(Type *Ty)
Return a SCEV for the constant 0 of a specific type.
bool willNotOverflow(Instruction::BinaryOps BinOp, bool Signed, const SCEV *LHS, const SCEV *RHS, const Instruction *CtxI=nullptr)
Is operation BinOp between LHS and RHS provably does not have a signed/unsigned overflow (Signed)?...
const SCEV * getConstant(ConstantInt *V)
const SCEV * getSCEV(Value *V)
Return a SCEV expression for the full generality of the specified expression.
const SCEV * getNoopOrSignExtend(const SCEV *V, Type *Ty)
Return a SCEV corresponding to a conversion of the input value to the specified type.
const SCEV * getOne(Type *Ty)
Return a SCEV for the constant 1 of a specific type.
bool isLoopInvariant(const SCEV *S, const Loop *L)
Return true if the value of the given SCEV is unchanging in the specified loop.
bool isKnownPredicate(ICmpInst::Predicate Pred, const SCEV *LHS, const SCEV *RHS)
Test if the given expression is known to satisfy the condition described by Pred, LHS,...
const SCEV * getUMinExpr(const SCEV *LHS, const SCEV *RHS, bool Sequential=false)
const SCEV * getTruncateExpr(const SCEV *Op, Type *Ty, unsigned Depth=0)
const SCEV * getMinusSCEV(const SCEV *LHS, const SCEV *RHS, SCEV::NoWrapFlags Flags=SCEV::FlagAnyWrap, unsigned Depth=0)
Return LHS-RHS.
const SCEV * getNoopOrZeroExtend(const SCEV *V, Type *Ty)
Return a SCEV corresponding to a conversion of the input value to the specified type.
const SCEV * getSignExtendExpr(const SCEV *Op, Type *Ty, unsigned Depth=0)
const SCEV * getMulExpr(SmallVectorImpl< const SCEV * > &Ops, SCEV::NoWrapFlags Flags=SCEV::FlagAnyWrap, unsigned Depth=0)
Get a canonical multiply expression, or something simpler if possible.
const SCEV * getAddExpr(SmallVectorImpl< const SCEV * > &Ops, SCEV::NoWrapFlags Flags=SCEV::FlagAnyWrap, unsigned Depth=0)
Get a canonical add expression, or something simpler if possible.
A version of PriorityWorklist that selects small size optimized data structures for the vector and ma...
A templated base class for SmallPtrSet which provides the typesafe interface that is common across al...
Definition: SmallPtrSet.h:321
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:342
SmallPtrSet - This class implements a set which is optimized for holding SmallSize or less elements.
Definition: SmallPtrSet.h:427
bool empty() const
Definition: SmallVector.h:94
size_t size() const
Definition: SmallVector.h:91
This class consists of common code factored out of the SmallVector class to reduce code duplication b...
Definition: SmallVector.h:586
void push_back(const T &Elt)
Definition: SmallVector.h:426
This is a 'vector' (really, a variable-sized array), optimized for the case when the array is small.
Definition: SmallVector.h:1209
The instances of the Type class are immutable: once they are created, they are never changed.
Definition: Type.h:45
A Use represents the edge between a Value definition and its users.
Definition: Use.h:43
Value * get() const
Definition: Use.h:66
const Use & getOperandUse(unsigned i) const
Definition: User.h:182
Value * getOperand(unsigned i) const
Definition: User.h:169
LLVM Value Representation.
Definition: Value.h:74
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:255
An efficient, type-erasing, non-owning reference to a callable.
This class implements an extremely fast bulk output stream that can only output to a stream.
Definition: raw_ostream.h:52
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
@ C
The default llvm calling convention, compatible with C.
Definition: CallingConv.h:34
bool match(Val *V, const Pattern &P)
Definition: PatternMatch.h:49
class_match< Value > m_Value()
Match an arbitrary value and ignore it.
Definition: PatternMatch.h:92
auto m_LogicalAnd()
Matches L && R where L and R are arbitrary values.
BinaryOp_match< LHS, RHS, Instruction::Sub > m_Sub(const LHS &L, const RHS &R)
initializer< Ty > init(const Ty &Val)
Definition: CommandLine.h:450
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
bool simplifyLoop(Loop *L, DominatorTree *DT, LoopInfo *LI, ScalarEvolution *SE, AssumptionCache *AC, MemorySSAUpdater *MSSAU, bool PreserveLCSSA)
Simplify each loop in a loop nest recursively.
void dump(const SparseBitVector< ElementSize > &LHS, raw_ostream &out)
@ Offset
Definition: DWP.cpp:456
bool formLCSSARecursively(Loop &L, const DominatorTree &DT, const LoopInfo *LI, ScalarEvolution *SE)
Put a loop nest into LCSSA form.
Definition: LCSSA.cpp:425
void InvertBranch(BranchInst *PBI, IRBuilderBase &Builder)
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:163
raw_fd_ostream & errs()
This returns a reference to a raw_ostream for standard error.
void appendLoopsToWorklist(RangeT &&, SmallPriorityWorklist< Loop *, 4 > &)
Utility that implements appending of loops onto a worklist given a range.
Definition: LoopUtils.cpp:1681
bool isKnownNegativeInLoop(const SCEV *S, const Loop *L, ScalarEvolution &SE)
Returns true if we can prove that S is defined and always negative in loop L.
Definition: LoopUtils.cpp:1255
constexpr unsigned BitWidth
Definition: BitmaskEnum.h:191
PreservedAnalyses getLoopPassPreservedAnalyses()
Returns the minimum set of Analyses that all loop passes must preserve.
bool isKnownNonNegativeInLoop(const SCEV *S, const Loop *L, ScalarEvolution &SE)
Returns true if we can prove that S is defined and always non-negative in loop L.
Definition: LoopUtils.cpp:1262
static bool isProfitableToTransform(const Loop &L, const BranchInst *BI)
void swap(llvm::BitVector &LHS, llvm::BitVector &RHS)
Implement std::swap in terms of BitVector swap.
Definition: BitVector.h:860
IntegerType * ExitCountTy
static std::optional< LoopStructure > parseLoopStructure(ScalarEvolution &, Loop &, bool, const char *&)