1 //===-- llvm/Analysis/DependenceAnalysis.h -------------------- -*- C++ -*-===//
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
7 //===----------------------------------------------------------------------===//
9 // DependenceAnalysis is an LLVM pass that analyses dependences between memory
10 // accesses. Currently, it is an implementation of the approach described in
12 // Practical Dependence Testing
13 // Goff, Kennedy, Tseng
16 // There's a single entry point that analyzes the dependence between a pair
17 // of memory references in a function, returning either NULL, for no dependence,
18 // or a more-or-less detailed description of the dependence between them.
20 // This pass exists to support the DependenceGraph pass. There are two separate
21 // passes because there's a useful separation of concerns. A dependence exists
22 // if two conditions are met:
24 // 1) Two instructions reference the same memory location, and
25 // 2) There is a flow of control leading from one instruction to the other.
27 // DependenceAnalysis attacks the first condition; DependenceGraph will attack
28 // the second (it's not yet ready).
30 // Please note that this is work in progress and the interface is subject to
34 // Return a set of more precise dependences instead of just one dependence
37 //===----------------------------------------------------------------------===//
39 #ifndef LLVM_ANALYSIS_DEPENDENCEANALYSIS_H
40 #define LLVM_ANALYSIS_DEPENDENCEANALYSIS_H
42 #include "llvm/ADT/SmallBitVector.h"
43 #include "llvm/IR/Instructions.h"
44 #include "llvm/IR/PassManager.h"
45 #include "llvm/Pass.h"
49 template <typename T> class ArrayRef;
52 class ScalarEvolution;
57 /// Dependence - This class represents a dependence between two memory
58 /// memory references in a function. It contains minimal information and
59 /// is used in the very common situation where the compiler is unable to
60 /// determine anything beyond the existence of a dependence; that is, it
61 /// represents a confused dependence (see also FullDependence). In most
62 /// cases (for output, flow, and anti dependences), the dependence implies
63 /// an ordering, where the source must precede the destination; in contrast,
64 /// input dependences are unordered.
66 /// When a dependence graph is built, each Dependence will be a member of
67 /// the set of predecessor edges for its destination instruction and a set
68 /// if successor edges for its source instruction. These sets are represented
69 /// as singly-linked lists, with the "next" fields stored in the dependence
73 Dependence(Dependence &&) = default;
74 Dependence &operator=(Dependence &&) = default;
77 Dependence(Instruction *Source,
78 Instruction *Destination) :
81 NextPredecessor(nullptr),
82 NextSuccessor(nullptr) {}
83 virtual ~Dependence() {}
85 /// Dependence::DVEntry - Each level in the distance/direction vector
86 /// has a direction (or perhaps a union of several directions), and
87 /// perhaps a distance.
97 unsigned char Direction : 3; // Init to ALL, then refine.
98 bool Scalar : 1; // Init to true.
99 bool PeelFirst : 1; // Peeling the first iteration will break dependence.
100 bool PeelLast : 1; // Peeling the last iteration will break the dependence.
101 bool Splitable : 1; // Splitting the loop will break dependence.
102 const SCEV *Distance; // NULL implies no distance available.
103 DVEntry() : Direction(ALL), Scalar(true), PeelFirst(false),
104 PeelLast(false), Splitable(false), Distance(nullptr) { }
107 /// getSrc - Returns the source instruction for this dependence.
109 Instruction *getSrc() const { return Src; }
111 /// getDst - Returns the destination instruction for this dependence.
113 Instruction *getDst() const { return Dst; }
115 /// isInput - Returns true if this is an input dependence.
117 bool isInput() const;
119 /// isOutput - Returns true if this is an output dependence.
121 bool isOutput() const;
123 /// isFlow - Returns true if this is a flow (aka true) dependence.
127 /// isAnti - Returns true if this is an anti dependence.
131 /// isOrdered - Returns true if dependence is Output, Flow, or Anti
133 bool isOrdered() const { return isOutput() || isFlow() || isAnti(); }
135 /// isUnordered - Returns true if dependence is Input
137 bool isUnordered() const { return isInput(); }
139 /// isLoopIndependent - Returns true if this is a loop-independent
141 virtual bool isLoopIndependent() const { return true; }
143 /// isConfused - Returns true if this dependence is confused
144 /// (the compiler understands nothing and makes worst-case
146 virtual bool isConfused() const { return true; }
148 /// isConsistent - Returns true if this dependence is consistent
149 /// (occurs every time the source and destination are executed).
150 virtual bool isConsistent() const { return false; }
152 /// getLevels - Returns the number of common loops surrounding the
153 /// source and destination of the dependence.
154 virtual unsigned getLevels() const { return 0; }
156 /// getDirection - Returns the direction associated with a particular
158 virtual unsigned getDirection(unsigned Level) const { return DVEntry::ALL; }
160 /// getDistance - Returns the distance (or NULL) associated with a
161 /// particular level.
162 virtual const SCEV *getDistance(unsigned Level) const { return nullptr; }
164 /// isPeelFirst - Returns true if peeling the first iteration from
165 /// this loop will break this dependence.
166 virtual bool isPeelFirst(unsigned Level) const { return false; }
168 /// isPeelLast - Returns true if peeling the last iteration from
169 /// this loop will break this dependence.
170 virtual bool isPeelLast(unsigned Level) const { return false; }
172 /// isSplitable - Returns true if splitting this loop will break
174 virtual bool isSplitable(unsigned Level) const { return false; }
176 /// isScalar - Returns true if a particular level is scalar; that is,
177 /// if no subscript in the source or destination mention the induction
178 /// variable associated with the loop at this level.
179 virtual bool isScalar(unsigned Level) const;
181 /// getNextPredecessor - Returns the value of the NextPredecessor
183 const Dependence *getNextPredecessor() const { return NextPredecessor; }
185 /// getNextSuccessor - Returns the value of the NextSuccessor
187 const Dependence *getNextSuccessor() const { return NextSuccessor; }
189 /// setNextPredecessor - Sets the value of the NextPredecessor
191 void setNextPredecessor(const Dependence *pred) { NextPredecessor = pred; }
193 /// setNextSuccessor - Sets the value of the NextSuccessor
195 void setNextSuccessor(const Dependence *succ) { NextSuccessor = succ; }
197 /// dump - For debugging purposes, dumps a dependence to OS.
199 void dump(raw_ostream &OS) const;
202 Instruction *Src, *Dst;
203 const Dependence *NextPredecessor, *NextSuccessor;
204 friend class DependenceInfo;
207 /// FullDependence - This class represents a dependence between two memory
208 /// references in a function. It contains detailed information about the
209 /// dependence (direction vectors, etc.) and is used when the compiler is
210 /// able to accurately analyze the interaction of the references; that is,
211 /// it is not a confused dependence (see Dependence). In most cases
212 /// (for output, flow, and anti dependences), the dependence implies an
213 /// ordering, where the source must precede the destination; in contrast,
214 /// input dependences are unordered.
215 class FullDependence final : public Dependence {
217 FullDependence(Instruction *Src, Instruction *Dst, bool LoopIndependent,
220 /// isLoopIndependent - Returns true if this is a loop-independent
222 bool isLoopIndependent() const override { return LoopIndependent; }
224 /// isConfused - Returns true if this dependence is confused
225 /// (the compiler understands nothing and makes worst-case
227 bool isConfused() const override { return false; }
229 /// isConsistent - Returns true if this dependence is consistent
230 /// (occurs every time the source and destination are executed).
231 bool isConsistent() const override { return Consistent; }
233 /// getLevels - Returns the number of common loops surrounding the
234 /// source and destination of the dependence.
235 unsigned getLevels() const override { return Levels; }
237 /// getDirection - Returns the direction associated with a particular
239 unsigned getDirection(unsigned Level) const override;
241 /// getDistance - Returns the distance (or NULL) associated with a
242 /// particular level.
243 const SCEV *getDistance(unsigned Level) const override;
245 /// isPeelFirst - Returns true if peeling the first iteration from
246 /// this loop will break this dependence.
247 bool isPeelFirst(unsigned Level) const override;
249 /// isPeelLast - Returns true if peeling the last iteration from
250 /// this loop will break this dependence.
251 bool isPeelLast(unsigned Level) const override;
253 /// isSplitable - Returns true if splitting the loop will break
255 bool isSplitable(unsigned Level) const override;
257 /// isScalar - Returns true if a particular level is scalar; that is,
258 /// if no subscript in the source or destination mention the induction
259 /// variable associated with the loop at this level.
260 bool isScalar(unsigned Level) const override;
263 unsigned short Levels;
264 bool LoopIndependent;
265 bool Consistent; // Init to true, then refine.
266 std::unique_ptr<DVEntry[]> DV;
267 friend class DependenceInfo;
270 /// DependenceInfo - This class is the main dependence-analysis driver.
272 class DependenceInfo {
274 DependenceInfo(Function *F, AAResults *AA, ScalarEvolution *SE,
276 : AA(AA), SE(SE), LI(LI), F(F) {}
278 /// Handle transitive invalidation when the cached analysis results go away.
279 bool invalidate(Function &F, const PreservedAnalyses &PA,
280 FunctionAnalysisManager::Invalidator &Inv);
282 /// depends - Tests for a dependence between the Src and Dst instructions.
283 /// Returns NULL if no dependence; otherwise, returns a Dependence (or a
284 /// FullDependence) with as much information as can be gleaned.
285 /// The flag PossiblyLoopIndependent should be set by the caller
286 /// if it appears that control flow can reach from Src to Dst
287 /// without traversing a loop back edge.
288 std::unique_ptr<Dependence> depends(Instruction *Src,
290 bool PossiblyLoopIndependent);
292 /// getSplitIteration - Give a dependence that's splittable at some
293 /// particular level, return the iteration that should be used to split
296 /// Generally, the dependence analyzer will be used to build
297 /// a dependence graph for a function (basically a map from instructions
298 /// to dependences). Looking for cycles in the graph shows us loops
299 /// that cannot be trivially vectorized/parallelized.
301 /// We can try to improve the situation by examining all the dependences
302 /// that make up the cycle, looking for ones we can break.
303 /// Sometimes, peeling the first or last iteration of a loop will break
304 /// dependences, and there are flags for those possibilities.
305 /// Sometimes, splitting a loop at some other iteration will do the trick,
306 /// and we've got a flag for that case. Rather than waste the space to
307 /// record the exact iteration (since we rarely know), we provide
308 /// a method that calculates the iteration. It's a drag that it must work
309 /// from scratch, but wonderful in that it's possible.
311 /// Here's an example:
313 /// for (i = 0; i < 10; i++)
317 /// There's a loop-carried flow dependence from the store to the load,
318 /// found by the weak-crossing SIV test. The dependence will have a flag,
319 /// indicating that the dependence can be broken by splitting the loop.
320 /// Calling getSplitIteration will return 5.
321 /// Splitting the loop breaks the dependence, like so:
323 /// for (i = 0; i <= 5; i++)
326 /// for (i = 6; i < 10; i++)
330 /// breaks the dependence and allows us to vectorize/parallelize
332 const SCEV *getSplitIteration(const Dependence &Dep, unsigned Level);
334 Function *getFunction() const { return F; }
342 /// Subscript - This private struct represents a pair of subscripts from
343 /// a pair of potentially multi-dimensional array references. We use a
344 /// vector of them to guide subscript partitioning.
348 enum ClassificationKind { ZIV, SIV, RDIV, MIV, NonLinear } Classification;
349 SmallBitVector Loops;
350 SmallBitVector GroupLoops;
351 SmallBitVector Group;
354 struct CoefficientInfo {
358 const SCEV *Iterations;
362 const SCEV *Iterations;
363 const SCEV *Upper[8];
364 const SCEV *Lower[8];
365 unsigned char Direction;
366 unsigned char DirSet;
369 /// Constraint - This private class represents a constraint, as defined
372 /// Practical Dependence Testing
373 /// Goff, Kennedy, Tseng
376 /// There are 5 kinds of constraint, in a hierarchy.
377 /// 1) Any - indicates no constraint, any dependence is possible.
378 /// 2) Line - A line ax + by = c, where a, b, and c are parameters,
379 /// representing the dependence equation.
380 /// 3) Distance - The value d of the dependence distance;
381 /// 4) Point - A point <x, y> representing the dependence from
382 /// iteration x to iteration y.
383 /// 5) Empty - No dependence is possible.
386 enum ConstraintKind { Empty, Point, Distance, Line, Any } Kind;
391 const Loop *AssociatedLoop;
394 /// isEmpty - Return true if the constraint is of kind Empty.
395 bool isEmpty() const { return Kind == Empty; }
397 /// isPoint - Return true if the constraint is of kind Point.
398 bool isPoint() const { return Kind == Point; }
400 /// isDistance - Return true if the constraint is of kind Distance.
401 bool isDistance() const { return Kind == Distance; }
403 /// isLine - Return true if the constraint is of kind Line.
404 /// Since Distance's can also be represented as Lines, we also return
405 /// true if the constraint is of kind Distance.
406 bool isLine() const { return Kind == Line || Kind == Distance; }
408 /// isAny - Return true if the constraint is of kind Any;
409 bool isAny() const { return Kind == Any; }
411 /// getX - If constraint is a point <X, Y>, returns X.
412 /// Otherwise assert.
413 const SCEV *getX() const;
415 /// getY - If constraint is a point <X, Y>, returns Y.
416 /// Otherwise assert.
417 const SCEV *getY() const;
419 /// getA - If constraint is a line AX + BY = C, returns A.
420 /// Otherwise assert.
421 const SCEV *getA() const;
423 /// getB - If constraint is a line AX + BY = C, returns B.
424 /// Otherwise assert.
425 const SCEV *getB() const;
427 /// getC - If constraint is a line AX + BY = C, returns C.
428 /// Otherwise assert.
429 const SCEV *getC() const;
431 /// getD - If constraint is a distance, returns D.
432 /// Otherwise assert.
433 const SCEV *getD() const;
435 /// getAssociatedLoop - Returns the loop associated with this constraint.
436 const Loop *getAssociatedLoop() const;
438 /// setPoint - Change a constraint to Point.
439 void setPoint(const SCEV *X, const SCEV *Y, const Loop *CurrentLoop);
441 /// setLine - Change a constraint to Line.
442 void setLine(const SCEV *A, const SCEV *B,
443 const SCEV *C, const Loop *CurrentLoop);
445 /// setDistance - Change a constraint to Distance.
446 void setDistance(const SCEV *D, const Loop *CurrentLoop);
448 /// setEmpty - Change a constraint to Empty.
451 /// setAny - Change a constraint to Any.
452 void setAny(ScalarEvolution *SE);
454 /// dump - For debugging purposes. Dumps the constraint
456 void dump(raw_ostream &OS) const;
459 /// establishNestingLevels - Examines the loop nesting of the Src and Dst
460 /// instructions and establishes their shared loops. Sets the variables
461 /// CommonLevels, SrcLevels, and MaxLevels.
462 /// The source and destination instructions needn't be contained in the same
463 /// loop. The routine establishNestingLevels finds the level of most deeply
464 /// nested loop that contains them both, CommonLevels. An instruction that's
465 /// not contained in a loop is at level = 0. MaxLevels is equal to the level
466 /// of the source plus the level of the destination, minus CommonLevels.
467 /// This lets us allocate vectors MaxLevels in length, with room for every
468 /// distinct loop referenced in both the source and destination subscripts.
469 /// The variable SrcLevels is the nesting depth of the source instruction.
470 /// It's used to help calculate distinct loops referenced by the destination.
471 /// Here's the map from loops to levels:
473 /// 1 - outermost common loop
474 /// ... - other common loops
475 /// CommonLevels - innermost common loop
476 /// ... - loops containing Src but not Dst
477 /// SrcLevels - innermost loop containing Src but not Dst
478 /// ... - loops containing Dst but not Src
479 /// MaxLevels - innermost loop containing Dst but not Src
480 /// Consider the follow code fragment:
497 /// If we're looking at the possibility of a dependence between the store
498 /// to A (the Src) and the load from A (the Dst), we'll note that they
499 /// have 2 loops in common, so CommonLevels will equal 2 and the direction
500 /// vector for Result will have 2 entries. SrcLevels = 4 and MaxLevels = 7.
501 /// A map from loop names to level indices would look like
503 /// b - 2 = CommonLevels
505 /// d - 4 = SrcLevels
508 /// g - 7 = MaxLevels
509 void establishNestingLevels(const Instruction *Src,
510 const Instruction *Dst);
512 unsigned CommonLevels, SrcLevels, MaxLevels;
514 /// mapSrcLoop - Given one of the loops containing the source, return
515 /// its level index in our numbering scheme.
516 unsigned mapSrcLoop(const Loop *SrcLoop) const;
518 /// mapDstLoop - Given one of the loops containing the destination,
519 /// return its level index in our numbering scheme.
520 unsigned mapDstLoop(const Loop *DstLoop) const;
522 /// isLoopInvariant - Returns true if Expression is loop invariant
524 bool isLoopInvariant(const SCEV *Expression, const Loop *LoopNest) const;
526 /// Makes sure all subscript pairs share the same integer type by
527 /// sign-extending as necessary.
528 /// Sign-extending a subscript is safe because getelementptr assumes the
529 /// array subscripts are signed.
530 void unifySubscriptType(ArrayRef<Subscript *> Pairs);
532 /// removeMatchingExtensions - Examines a subscript pair.
533 /// If the source and destination are identically sign (or zero)
534 /// extended, it strips off the extension in an effort to
535 /// simplify the actual analysis.
536 void removeMatchingExtensions(Subscript *Pair);
538 /// collectCommonLoops - Finds the set of loops from the LoopNest that
539 /// have a level <= CommonLevels and are referred to by the SCEV Expression.
540 void collectCommonLoops(const SCEV *Expression,
541 const Loop *LoopNest,
542 SmallBitVector &Loops) const;
544 /// checkSrcSubscript - Examines the SCEV Src, returning true iff it's
545 /// linear. Collect the set of loops mentioned by Src.
546 bool checkSrcSubscript(const SCEV *Src,
547 const Loop *LoopNest,
548 SmallBitVector &Loops);
550 /// checkDstSubscript - Examines the SCEV Dst, returning true iff it's
551 /// linear. Collect the set of loops mentioned by Dst.
552 bool checkDstSubscript(const SCEV *Dst,
553 const Loop *LoopNest,
554 SmallBitVector &Loops);
556 /// isKnownPredicate - Compare X and Y using the predicate Pred.
557 /// Basically a wrapper for SCEV::isKnownPredicate,
558 /// but tries harder, especially in the presence of sign and zero
559 /// extensions and symbolics.
560 bool isKnownPredicate(ICmpInst::Predicate Pred,
562 const SCEV *Y) const;
564 /// isKnownLessThan - Compare to see if S is less than Size
565 /// Another wrapper for isKnownNegative(S - max(Size, 1)) with some extra
566 /// checking if S is an AddRec and we can prove lessthan using the loop
568 bool isKnownLessThan(const SCEV *S, const SCEV *Size) const;
570 /// isKnownNonNegative - Compare to see if S is known not to be negative
571 /// Uses the fact that S comes from Ptr, which may be an inbound GEP,
572 /// Proving there is no wrapping going on.
573 bool isKnownNonNegative(const SCEV *S, const Value *Ptr) const;
575 /// collectUpperBound - All subscripts are the same type (on my machine,
576 /// an i64). The loop bound may be a smaller type. collectUpperBound
577 /// find the bound, if available, and zero extends it to the Type T.
578 /// (I zero extend since the bound should always be >= 0.)
579 /// If no upper bound is available, return NULL.
580 const SCEV *collectUpperBound(const Loop *l, Type *T) const;
582 /// collectConstantUpperBound - Calls collectUpperBound(), then
583 /// attempts to cast it to SCEVConstant. If the cast fails,
585 const SCEVConstant *collectConstantUpperBound(const Loop *l, Type *T) const;
587 /// classifyPair - Examines the subscript pair (the Src and Dst SCEVs)
588 /// and classifies it as either ZIV, SIV, RDIV, MIV, or Nonlinear.
589 /// Collects the associated loops in a set.
590 Subscript::ClassificationKind classifyPair(const SCEV *Src,
591 const Loop *SrcLoopNest,
593 const Loop *DstLoopNest,
594 SmallBitVector &Loops);
596 /// testZIV - Tests the ZIV subscript pair (Src and Dst) for dependence.
597 /// Returns true if any possible dependence is disproved.
598 /// If there might be a dependence, returns false.
599 /// If the dependence isn't proven to exist,
600 /// marks the Result as inconsistent.
601 bool testZIV(const SCEV *Src,
603 FullDependence &Result) const;
605 /// testSIV - Tests the SIV subscript pair (Src and Dst) for dependence.
606 /// Things of the form [c1 + a1*i] and [c2 + a2*j], where
607 /// i and j are induction variables, c1 and c2 are loop invariant,
608 /// and a1 and a2 are constant.
609 /// Returns true if any possible dependence is disproved.
610 /// If there might be a dependence, returns false.
611 /// Sets appropriate direction vector entry and, when possible,
612 /// the distance vector entry.
613 /// If the dependence isn't proven to exist,
614 /// marks the Result as inconsistent.
615 bool testSIV(const SCEV *Src,
618 FullDependence &Result,
619 Constraint &NewConstraint,
620 const SCEV *&SplitIter) const;
622 /// testRDIV - Tests the RDIV subscript pair (Src and Dst) for dependence.
623 /// Things of the form [c1 + a1*i] and [c2 + a2*j]
624 /// where i and j are induction variables, c1 and c2 are loop invariant,
625 /// and a1 and a2 are constant.
626 /// With minor algebra, this test can also be used for things like
627 /// [c1 + a1*i + a2*j][c2].
628 /// Returns true if any possible dependence is disproved.
629 /// If there might be a dependence, returns false.
630 /// Marks the Result as inconsistent.
631 bool testRDIV(const SCEV *Src,
633 FullDependence &Result) const;
635 /// testMIV - Tests the MIV subscript pair (Src and Dst) for dependence.
636 /// Returns true if dependence disproved.
637 /// Can sometimes refine direction vectors.
638 bool testMIV(const SCEV *Src,
640 const SmallBitVector &Loops,
641 FullDependence &Result) const;
643 /// strongSIVtest - Tests the strong SIV subscript pair (Src and Dst)
645 /// Things of the form [c1 + a*i] and [c2 + a*i],
646 /// where i is an induction variable, c1 and c2 are loop invariant,
647 /// and a is a constant
648 /// Returns true if any possible dependence is disproved.
649 /// If there might be a dependence, returns false.
650 /// Sets appropriate direction and distance.
651 bool strongSIVtest(const SCEV *Coeff,
652 const SCEV *SrcConst,
653 const SCEV *DstConst,
654 const Loop *CurrentLoop,
656 FullDependence &Result,
657 Constraint &NewConstraint) const;
659 /// weakCrossingSIVtest - Tests the weak-crossing SIV subscript pair
660 /// (Src and Dst) for dependence.
661 /// Things of the form [c1 + a*i] and [c2 - a*i],
662 /// where i is an induction variable, c1 and c2 are loop invariant,
663 /// and a is a constant.
664 /// Returns true if any possible dependence is disproved.
665 /// If there might be a dependence, returns false.
666 /// Sets appropriate direction entry.
667 /// Set consistent to false.
668 /// Marks the dependence as splitable.
669 bool weakCrossingSIVtest(const SCEV *SrcCoeff,
670 const SCEV *SrcConst,
671 const SCEV *DstConst,
672 const Loop *CurrentLoop,
674 FullDependence &Result,
675 Constraint &NewConstraint,
676 const SCEV *&SplitIter) const;
678 /// ExactSIVtest - Tests the SIV subscript pair
679 /// (Src and Dst) for dependence.
680 /// Things of the form [c1 + a1*i] and [c2 + a2*i],
681 /// where i is an induction variable, c1 and c2 are loop invariant,
682 /// and a1 and a2 are constant.
683 /// Returns true if any possible dependence is disproved.
684 /// If there might be a dependence, returns false.
685 /// Sets appropriate direction entry.
686 /// Set consistent to false.
687 bool exactSIVtest(const SCEV *SrcCoeff,
688 const SCEV *DstCoeff,
689 const SCEV *SrcConst,
690 const SCEV *DstConst,
691 const Loop *CurrentLoop,
693 FullDependence &Result,
694 Constraint &NewConstraint) const;
696 /// weakZeroSrcSIVtest - Tests the weak-zero SIV subscript pair
697 /// (Src and Dst) for dependence.
698 /// Things of the form [c1] and [c2 + a*i],
699 /// where i is an induction variable, c1 and c2 are loop invariant,
700 /// and a is a constant. See also weakZeroDstSIVtest.
701 /// Returns true if any possible dependence is disproved.
702 /// If there might be a dependence, returns false.
703 /// Sets appropriate direction entry.
704 /// Set consistent to false.
705 /// If loop peeling will break the dependence, mark appropriately.
706 bool weakZeroSrcSIVtest(const SCEV *DstCoeff,
707 const SCEV *SrcConst,
708 const SCEV *DstConst,
709 const Loop *CurrentLoop,
711 FullDependence &Result,
712 Constraint &NewConstraint) const;
714 /// weakZeroDstSIVtest - Tests the weak-zero SIV subscript pair
715 /// (Src and Dst) for dependence.
716 /// Things of the form [c1 + a*i] and [c2],
717 /// where i is an induction variable, c1 and c2 are loop invariant,
718 /// and a is a constant. See also weakZeroSrcSIVtest.
719 /// Returns true if any possible dependence is disproved.
720 /// If there might be a dependence, returns false.
721 /// Sets appropriate direction entry.
722 /// Set consistent to false.
723 /// If loop peeling will break the dependence, mark appropriately.
724 bool weakZeroDstSIVtest(const SCEV *SrcCoeff,
725 const SCEV *SrcConst,
726 const SCEV *DstConst,
727 const Loop *CurrentLoop,
729 FullDependence &Result,
730 Constraint &NewConstraint) const;
732 /// exactRDIVtest - Tests the RDIV subscript pair for dependence.
733 /// Things of the form [c1 + a*i] and [c2 + b*j],
734 /// where i and j are induction variable, c1 and c2 are loop invariant,
735 /// and a and b are constants.
736 /// Returns true if any possible dependence is disproved.
737 /// Marks the result as inconsistent.
738 /// Works in some cases that symbolicRDIVtest doesn't,
740 bool exactRDIVtest(const SCEV *SrcCoeff,
741 const SCEV *DstCoeff,
742 const SCEV *SrcConst,
743 const SCEV *DstConst,
746 FullDependence &Result) const;
748 /// symbolicRDIVtest - Tests the RDIV subscript pair for dependence.
749 /// Things of the form [c1 + a*i] and [c2 + b*j],
750 /// where i and j are induction variable, c1 and c2 are loop invariant,
751 /// and a and b are constants.
752 /// Returns true if any possible dependence is disproved.
753 /// Marks the result as inconsistent.
754 /// Works in some cases that exactRDIVtest doesn't,
755 /// and vice versa. Can also be used as a backup for
756 /// ordinary SIV tests.
757 bool symbolicRDIVtest(const SCEV *SrcCoeff,
758 const SCEV *DstCoeff,
759 const SCEV *SrcConst,
760 const SCEV *DstConst,
762 const Loop *DstLoop) const;
764 /// gcdMIVtest - Tests an MIV subscript pair for dependence.
765 /// Returns true if any possible dependence is disproved.
766 /// Marks the result as inconsistent.
767 /// Can sometimes disprove the equal direction for 1 or more loops.
768 // Can handle some symbolics that even the SIV tests don't get,
769 /// so we use it as a backup for everything.
770 bool gcdMIVtest(const SCEV *Src,
772 FullDependence &Result) const;
774 /// banerjeeMIVtest - Tests an MIV subscript pair for dependence.
775 /// Returns true if any possible dependence is disproved.
776 /// Marks the result as inconsistent.
777 /// Computes directions.
778 bool banerjeeMIVtest(const SCEV *Src,
780 const SmallBitVector &Loops,
781 FullDependence &Result) const;
783 /// collectCoefficientInfo - Walks through the subscript,
784 /// collecting each coefficient, the associated loop bounds,
785 /// and recording its positive and negative parts for later use.
786 CoefficientInfo *collectCoeffInfo(const SCEV *Subscript,
788 const SCEV *&Constant) const;
790 /// getPositivePart - X^+ = max(X, 0).
792 const SCEV *getPositivePart(const SCEV *X) const;
794 /// getNegativePart - X^- = min(X, 0).
796 const SCEV *getNegativePart(const SCEV *X) const;
798 /// getLowerBound - Looks through all the bounds info and
799 /// computes the lower bound given the current direction settings
801 const SCEV *getLowerBound(BoundInfo *Bound) const;
803 /// getUpperBound - Looks through all the bounds info and
804 /// computes the upper bound given the current direction settings
806 const SCEV *getUpperBound(BoundInfo *Bound) const;
808 /// exploreDirections - Hierarchically expands the direction vector
809 /// search space, combining the directions of discovered dependences
810 /// in the DirSet field of Bound. Returns the number of distinct
811 /// dependences discovered. If the dependence is disproved,
812 /// it will return 0.
813 unsigned exploreDirections(unsigned Level,
817 const SmallBitVector &Loops,
818 unsigned &DepthExpanded,
819 const SCEV *Delta) const;
821 /// testBounds - Returns true iff the current bounds are plausible.
822 bool testBounds(unsigned char DirKind,
825 const SCEV *Delta) const;
827 /// findBoundsALL - Computes the upper and lower bounds for level K
828 /// using the * direction. Records them in Bound.
829 void findBoundsALL(CoefficientInfo *A,
834 /// findBoundsLT - Computes the upper and lower bounds for level K
835 /// using the < direction. Records them in Bound.
836 void findBoundsLT(CoefficientInfo *A,
841 /// findBoundsGT - Computes the upper and lower bounds for level K
842 /// using the > direction. Records them in Bound.
843 void findBoundsGT(CoefficientInfo *A,
848 /// findBoundsEQ - Computes the upper and lower bounds for level K
849 /// using the = direction. Records them in Bound.
850 void findBoundsEQ(CoefficientInfo *A,
855 /// intersectConstraints - Updates X with the intersection
856 /// of the Constraints X and Y. Returns true if X has changed.
857 bool intersectConstraints(Constraint *X,
858 const Constraint *Y);
860 /// propagate - Review the constraints, looking for opportunities
861 /// to simplify a subscript pair (Src and Dst).
862 /// Return true if some simplification occurs.
863 /// If the simplification isn't exact (that is, if it is conservative
864 /// in terms of dependence), set consistent to false.
865 bool propagate(const SCEV *&Src,
867 SmallBitVector &Loops,
868 SmallVectorImpl<Constraint> &Constraints,
871 /// propagateDistance - Attempt to propagate a distance
872 /// constraint into a subscript pair (Src and Dst).
873 /// Return true if some simplification occurs.
874 /// If the simplification isn't exact (that is, if it is conservative
875 /// in terms of dependence), set consistent to false.
876 bool propagateDistance(const SCEV *&Src,
878 Constraint &CurConstraint,
881 /// propagatePoint - Attempt to propagate a point
882 /// constraint into a subscript pair (Src and Dst).
883 /// Return true if some simplification occurs.
884 bool propagatePoint(const SCEV *&Src,
886 Constraint &CurConstraint);
888 /// propagateLine - Attempt to propagate a line
889 /// constraint into a subscript pair (Src and Dst).
890 /// Return true if some simplification occurs.
891 /// If the simplification isn't exact (that is, if it is conservative
892 /// in terms of dependence), set consistent to false.
893 bool propagateLine(const SCEV *&Src,
895 Constraint &CurConstraint,
898 /// findCoefficient - Given a linear SCEV,
899 /// return the coefficient corresponding to specified loop.
900 /// If there isn't one, return the SCEV constant 0.
901 /// For example, given a*i + b*j + c*k, returning the coefficient
902 /// corresponding to the j loop would yield b.
903 const SCEV *findCoefficient(const SCEV *Expr,
904 const Loop *TargetLoop) const;
906 /// zeroCoefficient - Given a linear SCEV,
907 /// return the SCEV given by zeroing out the coefficient
908 /// corresponding to the specified loop.
909 /// For example, given a*i + b*j + c*k, zeroing the coefficient
910 /// corresponding to the j loop would yield a*i + c*k.
911 const SCEV *zeroCoefficient(const SCEV *Expr,
912 const Loop *TargetLoop) const;
914 /// addToCoefficient - Given a linear SCEV Expr,
915 /// return the SCEV given by adding some Value to the
916 /// coefficient corresponding to the specified TargetLoop.
917 /// For example, given a*i + b*j + c*k, adding 1 to the coefficient
918 /// corresponding to the j loop would yield a*i + (b+1)*j + c*k.
919 const SCEV *addToCoefficient(const SCEV *Expr,
920 const Loop *TargetLoop,
921 const SCEV *Value) const;
923 /// updateDirection - Update direction vector entry
924 /// based on the current constraint.
925 void updateDirection(Dependence::DVEntry &Level,
926 const Constraint &CurConstraint) const;
928 /// Given a linear access function, tries to recover subscripts
929 /// for each dimension of the array element access.
930 bool tryDelinearize(Instruction *Src, Instruction *Dst,
931 SmallVectorImpl<Subscript> &Pair);
933 /// Tries to delinearize access function for a fixed size multi-dimensional
934 /// array, by deriving subscripts from GEP instructions. Returns true upon
935 /// success and false otherwise.
936 bool tryDelinearizeFixedSize(Instruction *Src, Instruction *Dst,
937 const SCEV *SrcAccessFn,
938 const SCEV *DstAccessFn,
939 SmallVectorImpl<const SCEV *> &SrcSubscripts,
940 SmallVectorImpl<const SCEV *> &DstSubscripts);
942 /// Tries to delinearize access function for a multi-dimensional array with
943 /// symbolic runtime sizes.
944 /// Returns true upon success and false otherwise.
945 bool tryDelinearizeParametricSize(
946 Instruction *Src, Instruction *Dst, const SCEV *SrcAccessFn,
947 const SCEV *DstAccessFn, SmallVectorImpl<const SCEV *> &SrcSubscripts,
948 SmallVectorImpl<const SCEV *> &DstSubscripts);
950 /// checkSubscript - Helper function for checkSrcSubscript and
951 /// checkDstSubscript to avoid duplicate code
952 bool checkSubscript(const SCEV *Expr, const Loop *LoopNest,
953 SmallBitVector &Loops, bool IsSrc);
954 }; // class DependenceInfo
956 /// AnalysisPass to compute dependence information in a function
957 class DependenceAnalysis : public AnalysisInfoMixin<DependenceAnalysis> {
959 typedef DependenceInfo Result;
960 Result run(Function &F, FunctionAnalysisManager &FAM);
963 static AnalysisKey Key;
964 friend struct AnalysisInfoMixin<DependenceAnalysis>;
965 }; // class DependenceAnalysis
967 /// Printer pass to dump DA results.
968 struct DependenceAnalysisPrinterPass
969 : public PassInfoMixin<DependenceAnalysisPrinterPass> {
970 DependenceAnalysisPrinterPass(raw_ostream &OS) : OS(OS) {}
972 PreservedAnalyses run(Function &F, FunctionAnalysisManager &FAM);
976 }; // class DependenceAnalysisPrinterPass
978 /// Legacy pass manager pass to access dependence information
979 class DependenceAnalysisWrapperPass : public FunctionPass {
981 static char ID; // Class identification, replacement for typeinfo
982 DependenceAnalysisWrapperPass();
984 bool runOnFunction(Function &F) override;
985 void releaseMemory() override;
986 void getAnalysisUsage(AnalysisUsage &) const override;
987 void print(raw_ostream &, const Module * = nullptr) const override;
988 DependenceInfo &getDI() const;
991 std::unique_ptr<DependenceInfo> info;
992 }; // class DependenceAnalysisWrapperPass
994 /// createDependenceAnalysisPass - This creates an instance of the
995 /// DependenceAnalysis wrapper pass.
996 FunctionPass *createDependenceAnalysisWrapperPass();