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/Analysis/AliasAnalysis.h"
44 #include "llvm/IR/Instructions.h"
45 #include "llvm/Pass.h"
48 template <typename T
> class ArrayRef
;
51 class ScalarEvolution
;
56 /// Dependence - This class represents a dependence between two memory
57 /// memory references in a function. It contains minimal information and
58 /// is used in the very common situation where the compiler is unable to
59 /// determine anything beyond the existence of a dependence; that is, it
60 /// represents a confused dependence (see also FullDependence). In most
61 /// cases (for output, flow, and anti dependences), the dependence implies
62 /// an ordering, where the source must precede the destination; in contrast,
63 /// input dependences are unordered.
65 /// When a dependence graph is built, each Dependence will be a member of
66 /// the set of predecessor edges for its destination instruction and a set
67 /// if successor edges for its source instruction. These sets are represented
68 /// as singly-linked lists, with the "next" fields stored in the dependence
72 Dependence(Dependence
&&) = default;
73 Dependence
&operator=(Dependence
&&) = default;
76 Dependence(Instruction
*Source
,
77 Instruction
*Destination
) :
80 NextPredecessor(nullptr),
81 NextSuccessor(nullptr) {}
82 virtual ~Dependence() {}
84 /// Dependence::DVEntry - Each level in the distance/direction vector
85 /// has a direction (or perhaps a union of several directions), and
86 /// perhaps a distance.
96 unsigned char Direction
: 3; // Init to ALL, then refine.
97 bool Scalar
: 1; // Init to true.
98 bool PeelFirst
: 1; // Peeling the first iteration will break dependence.
99 bool PeelLast
: 1; // Peeling the last iteration will break the dependence.
100 bool Splitable
: 1; // Splitting the loop will break dependence.
101 const SCEV
*Distance
; // NULL implies no distance available.
102 DVEntry() : Direction(ALL
), Scalar(true), PeelFirst(false),
103 PeelLast(false), Splitable(false), Distance(nullptr) { }
106 /// getSrc - Returns the source instruction for this dependence.
108 Instruction
*getSrc() const { return Src
; }
110 /// getDst - Returns the destination instruction for this dependence.
112 Instruction
*getDst() const { return Dst
; }
114 /// isInput - Returns true if this is an input dependence.
116 bool isInput() const;
118 /// isOutput - Returns true if this is an output dependence.
120 bool isOutput() const;
122 /// isFlow - Returns true if this is a flow (aka true) dependence.
126 /// isAnti - Returns true if this is an anti dependence.
130 /// isOrdered - Returns true if dependence is Output, Flow, or Anti
132 bool isOrdered() const { return isOutput() || isFlow() || isAnti(); }
134 /// isUnordered - Returns true if dependence is Input
136 bool isUnordered() const { return isInput(); }
138 /// isLoopIndependent - Returns true if this is a loop-independent
140 virtual bool isLoopIndependent() const { return true; }
142 /// isConfused - Returns true if this dependence is confused
143 /// (the compiler understands nothing and makes worst-case
145 virtual bool isConfused() const { return true; }
147 /// isConsistent - Returns true if this dependence is consistent
148 /// (occurs every time the source and destination are executed).
149 virtual bool isConsistent() const { return false; }
151 /// getLevels - Returns the number of common loops surrounding the
152 /// source and destination of the dependence.
153 virtual unsigned getLevels() const { return 0; }
155 /// getDirection - Returns the direction associated with a particular
157 virtual unsigned getDirection(unsigned Level
) const { return DVEntry::ALL
; }
159 /// getDistance - Returns the distance (or NULL) associated with a
160 /// particular level.
161 virtual const SCEV
*getDistance(unsigned Level
) const { return nullptr; }
163 /// isPeelFirst - Returns true if peeling the first iteration from
164 /// this loop will break this dependence.
165 virtual bool isPeelFirst(unsigned Level
) const { return false; }
167 /// isPeelLast - Returns true if peeling the last iteration from
168 /// this loop will break this dependence.
169 virtual bool isPeelLast(unsigned Level
) const { return false; }
171 /// isSplitable - Returns true if splitting this loop will break
173 virtual bool isSplitable(unsigned Level
) const { return false; }
175 /// isScalar - Returns true if a particular level is scalar; that is,
176 /// if no subscript in the source or destination mention the induction
177 /// variable associated with the loop at this level.
178 virtual bool isScalar(unsigned Level
) const;
180 /// getNextPredecessor - Returns the value of the NextPredecessor
182 const Dependence
*getNextPredecessor() const { return NextPredecessor
; }
184 /// getNextSuccessor - Returns the value of the NextSuccessor
186 const Dependence
*getNextSuccessor() const { return NextSuccessor
; }
188 /// setNextPredecessor - Sets the value of the NextPredecessor
190 void setNextPredecessor(const Dependence
*pred
) { NextPredecessor
= pred
; }
192 /// setNextSuccessor - Sets the value of the NextSuccessor
194 void setNextSuccessor(const Dependence
*succ
) { NextSuccessor
= succ
; }
196 /// dump - For debugging purposes, dumps a dependence to OS.
198 void dump(raw_ostream
&OS
) const;
201 Instruction
*Src
, *Dst
;
202 const Dependence
*NextPredecessor
, *NextSuccessor
;
203 friend class DependenceInfo
;
206 /// FullDependence - This class represents a dependence between two memory
207 /// references in a function. It contains detailed information about the
208 /// dependence (direction vectors, etc.) and is used when the compiler is
209 /// able to accurately analyze the interaction of the references; that is,
210 /// it is not a confused dependence (see Dependence). In most cases
211 /// (for output, flow, and anti dependences), the dependence implies an
212 /// ordering, where the source must precede the destination; in contrast,
213 /// input dependences are unordered.
214 class FullDependence final
: public Dependence
{
216 FullDependence(Instruction
*Src
, Instruction
*Dst
, bool LoopIndependent
,
219 /// isLoopIndependent - Returns true if this is a loop-independent
221 bool isLoopIndependent() const override
{ return LoopIndependent
; }
223 /// isConfused - Returns true if this dependence is confused
224 /// (the compiler understands nothing and makes worst-case
226 bool isConfused() const override
{ return false; }
228 /// isConsistent - Returns true if this dependence is consistent
229 /// (occurs every time the source and destination are executed).
230 bool isConsistent() const override
{ return Consistent
; }
232 /// getLevels - Returns the number of common loops surrounding the
233 /// source and destination of the dependence.
234 unsigned getLevels() const override
{ return Levels
; }
236 /// getDirection - Returns the direction associated with a particular
238 unsigned getDirection(unsigned Level
) const override
;
240 /// getDistance - Returns the distance (or NULL) associated with a
241 /// particular level.
242 const SCEV
*getDistance(unsigned Level
) const override
;
244 /// isPeelFirst - Returns true if peeling the first iteration from
245 /// this loop will break this dependence.
246 bool isPeelFirst(unsigned Level
) const override
;
248 /// isPeelLast - Returns true if peeling the last iteration from
249 /// this loop will break this dependence.
250 bool isPeelLast(unsigned Level
) const override
;
252 /// isSplitable - Returns true if splitting the loop will break
254 bool isSplitable(unsigned Level
) const override
;
256 /// isScalar - Returns true if a particular level is scalar; that is,
257 /// if no subscript in the source or destination mention the induction
258 /// variable associated with the loop at this level.
259 bool isScalar(unsigned Level
) const override
;
262 unsigned short Levels
;
263 bool LoopIndependent
;
264 bool Consistent
; // Init to true, then refine.
265 std::unique_ptr
<DVEntry
[]> DV
;
266 friend class DependenceInfo
;
269 /// DependenceInfo - This class is the main dependence-analysis driver.
271 class DependenceInfo
{
273 DependenceInfo(Function
*F
, AliasAnalysis
*AA
, ScalarEvolution
*SE
,
275 : AA(AA
), SE(SE
), LI(LI
), F(F
) {}
277 /// Handle transitive invalidation when the cached analysis results go away.
278 bool invalidate(Function
&F
, const PreservedAnalyses
&PA
,
279 FunctionAnalysisManager::Invalidator
&Inv
);
281 /// depends - Tests for a dependence between the Src and Dst instructions.
282 /// Returns NULL if no dependence; otherwise, returns a Dependence (or a
283 /// FullDependence) with as much information as can be gleaned.
284 /// The flag PossiblyLoopIndependent should be set by the caller
285 /// if it appears that control flow can reach from Src to Dst
286 /// without traversing a loop back edge.
287 std::unique_ptr
<Dependence
> depends(Instruction
*Src
,
289 bool PossiblyLoopIndependent
);
291 /// getSplitIteration - Give a dependence that's splittable at some
292 /// particular level, return the iteration that should be used to split
295 /// Generally, the dependence analyzer will be used to build
296 /// a dependence graph for a function (basically a map from instructions
297 /// to dependences). Looking for cycles in the graph shows us loops
298 /// that cannot be trivially vectorized/parallelized.
300 /// We can try to improve the situation by examining all the dependences
301 /// that make up the cycle, looking for ones we can break.
302 /// Sometimes, peeling the first or last iteration of a loop will break
303 /// dependences, and there are flags for those possibilities.
304 /// Sometimes, splitting a loop at some other iteration will do the trick,
305 /// and we've got a flag for that case. Rather than waste the space to
306 /// record the exact iteration (since we rarely know), we provide
307 /// a method that calculates the iteration. It's a drag that it must work
308 /// from scratch, but wonderful in that it's possible.
310 /// Here's an example:
312 /// for (i = 0; i < 10; i++)
316 /// There's a loop-carried flow dependence from the store to the load,
317 /// found by the weak-crossing SIV test. The dependence will have a flag,
318 /// indicating that the dependence can be broken by splitting the loop.
319 /// Calling getSplitIteration will return 5.
320 /// Splitting the loop breaks the dependence, like so:
322 /// for (i = 0; i <= 5; i++)
325 /// for (i = 6; i < 10; i++)
329 /// breaks the dependence and allows us to vectorize/parallelize
331 const SCEV
*getSplitIteration(const Dependence
&Dep
, unsigned Level
);
333 Function
*getFunction() const { return F
; }
341 /// Subscript - This private struct represents a pair of subscripts from
342 /// a pair of potentially multi-dimensional array references. We use a
343 /// vector of them to guide subscript partitioning.
347 enum ClassificationKind
{ ZIV
, SIV
, RDIV
, MIV
, NonLinear
} Classification
;
348 SmallBitVector Loops
;
349 SmallBitVector GroupLoops
;
350 SmallBitVector Group
;
353 struct CoefficientInfo
{
357 const SCEV
*Iterations
;
361 const SCEV
*Iterations
;
362 const SCEV
*Upper
[8];
363 const SCEV
*Lower
[8];
364 unsigned char Direction
;
365 unsigned char DirSet
;
368 /// Constraint - This private class represents a constraint, as defined
371 /// Practical Dependence Testing
372 /// Goff, Kennedy, Tseng
375 /// There are 5 kinds of constraint, in a hierarchy.
376 /// 1) Any - indicates no constraint, any dependence is possible.
377 /// 2) Line - A line ax + by = c, where a, b, and c are parameters,
378 /// representing the dependence equation.
379 /// 3) Distance - The value d of the dependence distance;
380 /// 4) Point - A point <x, y> representing the dependence from
381 /// iteration x to iteration y.
382 /// 5) Empty - No dependence is possible.
385 enum ConstraintKind
{ Empty
, Point
, Distance
, Line
, Any
} Kind
;
390 const Loop
*AssociatedLoop
;
393 /// isEmpty - Return true if the constraint is of kind Empty.
394 bool isEmpty() const { return Kind
== Empty
; }
396 /// isPoint - Return true if the constraint is of kind Point.
397 bool isPoint() const { return Kind
== Point
; }
399 /// isDistance - Return true if the constraint is of kind Distance.
400 bool isDistance() const { return Kind
== Distance
; }
402 /// isLine - Return true if the constraint is of kind Line.
403 /// Since Distance's can also be represented as Lines, we also return
404 /// true if the constraint is of kind Distance.
405 bool isLine() const { return Kind
== Line
|| Kind
== Distance
; }
407 /// isAny - Return true if the constraint is of kind Any;
408 bool isAny() const { return Kind
== Any
; }
410 /// getX - If constraint is a point <X, Y>, returns X.
411 /// Otherwise assert.
412 const SCEV
*getX() const;
414 /// getY - If constraint is a point <X, Y>, returns Y.
415 /// Otherwise assert.
416 const SCEV
*getY() const;
418 /// getA - If constraint is a line AX + BY = C, returns A.
419 /// Otherwise assert.
420 const SCEV
*getA() const;
422 /// getB - If constraint is a line AX + BY = C, returns B.
423 /// Otherwise assert.
424 const SCEV
*getB() const;
426 /// getC - If constraint is a line AX + BY = C, returns C.
427 /// Otherwise assert.
428 const SCEV
*getC() const;
430 /// getD - If constraint is a distance, returns D.
431 /// Otherwise assert.
432 const SCEV
*getD() const;
434 /// getAssociatedLoop - Returns the loop associated with this constraint.
435 const Loop
*getAssociatedLoop() const;
437 /// setPoint - Change a constraint to Point.
438 void setPoint(const SCEV
*X
, const SCEV
*Y
, const Loop
*CurrentLoop
);
440 /// setLine - Change a constraint to Line.
441 void setLine(const SCEV
*A
, const SCEV
*B
,
442 const SCEV
*C
, const Loop
*CurrentLoop
);
444 /// setDistance - Change a constraint to Distance.
445 void setDistance(const SCEV
*D
, const Loop
*CurrentLoop
);
447 /// setEmpty - Change a constraint to Empty.
450 /// setAny - Change a constraint to Any.
451 void setAny(ScalarEvolution
*SE
);
453 /// dump - For debugging purposes. Dumps the constraint
455 void dump(raw_ostream
&OS
) const;
458 /// establishNestingLevels - Examines the loop nesting of the Src and Dst
459 /// instructions and establishes their shared loops. Sets the variables
460 /// CommonLevels, SrcLevels, and MaxLevels.
461 /// The source and destination instructions needn't be contained in the same
462 /// loop. The routine establishNestingLevels finds the level of most deeply
463 /// nested loop that contains them both, CommonLevels. An instruction that's
464 /// not contained in a loop is at level = 0. MaxLevels is equal to the level
465 /// of the source plus the level of the destination, minus CommonLevels.
466 /// This lets us allocate vectors MaxLevels in length, with room for every
467 /// distinct loop referenced in both the source and destination subscripts.
468 /// The variable SrcLevels is the nesting depth of the source instruction.
469 /// It's used to help calculate distinct loops referenced by the destination.
470 /// Here's the map from loops to levels:
472 /// 1 - outermost common loop
473 /// ... - other common loops
474 /// CommonLevels - innermost common loop
475 /// ... - loops containing Src but not Dst
476 /// SrcLevels - innermost loop containing Src but not Dst
477 /// ... - loops containing Dst but not Src
478 /// MaxLevels - innermost loop containing Dst but not Src
479 /// Consider the follow code fragment:
496 /// If we're looking at the possibility of a dependence between the store
497 /// to A (the Src) and the load from A (the Dst), we'll note that they
498 /// have 2 loops in common, so CommonLevels will equal 2 and the direction
499 /// vector for Result will have 2 entries. SrcLevels = 4 and MaxLevels = 7.
500 /// A map from loop names to level indices would look like
502 /// b - 2 = CommonLevels
504 /// d - 4 = SrcLevels
507 /// g - 7 = MaxLevels
508 void establishNestingLevels(const Instruction
*Src
,
509 const Instruction
*Dst
);
511 unsigned CommonLevels
, SrcLevels
, MaxLevels
;
513 /// mapSrcLoop - Given one of the loops containing the source, return
514 /// its level index in our numbering scheme.
515 unsigned mapSrcLoop(const Loop
*SrcLoop
) const;
517 /// mapDstLoop - Given one of the loops containing the destination,
518 /// return its level index in our numbering scheme.
519 unsigned mapDstLoop(const Loop
*DstLoop
) const;
521 /// isLoopInvariant - Returns true if Expression is loop invariant
523 bool isLoopInvariant(const SCEV
*Expression
, const Loop
*LoopNest
) const;
525 /// Makes sure all subscript pairs share the same integer type by
526 /// sign-extending as necessary.
527 /// Sign-extending a subscript is safe because getelementptr assumes the
528 /// array subscripts are signed.
529 void unifySubscriptType(ArrayRef
<Subscript
*> Pairs
);
531 /// removeMatchingExtensions - Examines a subscript pair.
532 /// If the source and destination are identically sign (or zero)
533 /// extended, it strips off the extension in an effort to
534 /// simplify the actual analysis.
535 void removeMatchingExtensions(Subscript
*Pair
);
537 /// collectCommonLoops - Finds the set of loops from the LoopNest that
538 /// have a level <= CommonLevels and are referred to by the SCEV Expression.
539 void collectCommonLoops(const SCEV
*Expression
,
540 const Loop
*LoopNest
,
541 SmallBitVector
&Loops
) const;
543 /// checkSrcSubscript - Examines the SCEV Src, returning true iff it's
544 /// linear. Collect the set of loops mentioned by Src.
545 bool checkSrcSubscript(const SCEV
*Src
,
546 const Loop
*LoopNest
,
547 SmallBitVector
&Loops
);
549 /// checkDstSubscript - Examines the SCEV Dst, returning true iff it's
550 /// linear. Collect the set of loops mentioned by Dst.
551 bool checkDstSubscript(const SCEV
*Dst
,
552 const Loop
*LoopNest
,
553 SmallBitVector
&Loops
);
555 /// isKnownPredicate - Compare X and Y using the predicate Pred.
556 /// Basically a wrapper for SCEV::isKnownPredicate,
557 /// but tries harder, especially in the presence of sign and zero
558 /// extensions and symbolics.
559 bool isKnownPredicate(ICmpInst::Predicate Pred
,
561 const SCEV
*Y
) const;
563 /// isKnownLessThan - Compare to see if S is less than Size
564 /// Another wrapper for isKnownNegative(S - max(Size, 1)) with some extra
565 /// checking if S is an AddRec and we can prove lessthan using the loop
567 bool isKnownLessThan(const SCEV
*S
, const SCEV
*Size
) const;
569 /// isKnownNonNegative - Compare to see if S is known not to be negative
570 /// Uses the fact that S comes from Ptr, which may be an inbound GEP,
571 /// Proving there is no wrapping going on.
572 bool isKnownNonNegative(const SCEV
*S
, const Value
*Ptr
) const;
574 /// collectUpperBound - All subscripts are the same type (on my machine,
575 /// an i64). The loop bound may be a smaller type. collectUpperBound
576 /// find the bound, if available, and zero extends it to the Type T.
577 /// (I zero extend since the bound should always be >= 0.)
578 /// If no upper bound is available, return NULL.
579 const SCEV
*collectUpperBound(const Loop
*l
, Type
*T
) const;
581 /// collectConstantUpperBound - Calls collectUpperBound(), then
582 /// attempts to cast it to SCEVConstant. If the cast fails,
584 const SCEVConstant
*collectConstantUpperBound(const Loop
*l
, Type
*T
) const;
586 /// classifyPair - Examines the subscript pair (the Src and Dst SCEVs)
587 /// and classifies it as either ZIV, SIV, RDIV, MIV, or Nonlinear.
588 /// Collects the associated loops in a set.
589 Subscript::ClassificationKind
classifyPair(const SCEV
*Src
,
590 const Loop
*SrcLoopNest
,
592 const Loop
*DstLoopNest
,
593 SmallBitVector
&Loops
);
595 /// testZIV - Tests the ZIV subscript pair (Src and Dst) for dependence.
596 /// Returns true if any possible dependence is disproved.
597 /// If there might be a dependence, returns false.
598 /// If the dependence isn't proven to exist,
599 /// marks the Result as inconsistent.
600 bool testZIV(const SCEV
*Src
,
602 FullDependence
&Result
) const;
604 /// testSIV - Tests the SIV subscript pair (Src and Dst) for dependence.
605 /// Things of the form [c1 + a1*i] and [c2 + a2*j], where
606 /// i and j are induction variables, c1 and c2 are loop invariant,
607 /// and a1 and a2 are constant.
608 /// Returns true if any possible dependence is disproved.
609 /// If there might be a dependence, returns false.
610 /// Sets appropriate direction vector entry and, when possible,
611 /// the distance vector entry.
612 /// If the dependence isn't proven to exist,
613 /// marks the Result as inconsistent.
614 bool testSIV(const SCEV
*Src
,
617 FullDependence
&Result
,
618 Constraint
&NewConstraint
,
619 const SCEV
*&SplitIter
) const;
621 /// testRDIV - Tests the RDIV subscript pair (Src and Dst) for dependence.
622 /// Things of the form [c1 + a1*i] and [c2 + a2*j]
623 /// where i and j are induction variables, c1 and c2 are loop invariant,
624 /// and a1 and a2 are constant.
625 /// With minor algebra, this test can also be used for things like
626 /// [c1 + a1*i + a2*j][c2].
627 /// Returns true if any possible dependence is disproved.
628 /// If there might be a dependence, returns false.
629 /// Marks the Result as inconsistent.
630 bool testRDIV(const SCEV
*Src
,
632 FullDependence
&Result
) const;
634 /// testMIV - Tests the MIV subscript pair (Src and Dst) for dependence.
635 /// Returns true if dependence disproved.
636 /// Can sometimes refine direction vectors.
637 bool testMIV(const SCEV
*Src
,
639 const SmallBitVector
&Loops
,
640 FullDependence
&Result
) const;
642 /// strongSIVtest - Tests the strong SIV subscript pair (Src and Dst)
644 /// Things of the form [c1 + a*i] and [c2 + a*i],
645 /// where i is an induction variable, c1 and c2 are loop invariant,
646 /// and a is a constant
647 /// Returns true if any possible dependence is disproved.
648 /// If there might be a dependence, returns false.
649 /// Sets appropriate direction and distance.
650 bool strongSIVtest(const SCEV
*Coeff
,
651 const SCEV
*SrcConst
,
652 const SCEV
*DstConst
,
653 const Loop
*CurrentLoop
,
655 FullDependence
&Result
,
656 Constraint
&NewConstraint
) const;
658 /// weakCrossingSIVtest - Tests the weak-crossing SIV subscript pair
659 /// (Src and Dst) for dependence.
660 /// Things of the form [c1 + a*i] and [c2 - a*i],
661 /// where i is an induction variable, c1 and c2 are loop invariant,
662 /// and a is a constant.
663 /// Returns true if any possible dependence is disproved.
664 /// If there might be a dependence, returns false.
665 /// Sets appropriate direction entry.
666 /// Set consistent to false.
667 /// Marks the dependence as splitable.
668 bool weakCrossingSIVtest(const SCEV
*SrcCoeff
,
669 const SCEV
*SrcConst
,
670 const SCEV
*DstConst
,
671 const Loop
*CurrentLoop
,
673 FullDependence
&Result
,
674 Constraint
&NewConstraint
,
675 const SCEV
*&SplitIter
) const;
677 /// ExactSIVtest - Tests the SIV subscript pair
678 /// (Src and Dst) for dependence.
679 /// Things of the form [c1 + a1*i] and [c2 + a2*i],
680 /// where i is an induction variable, c1 and c2 are loop invariant,
681 /// and a1 and a2 are constant.
682 /// Returns true if any possible dependence is disproved.
683 /// If there might be a dependence, returns false.
684 /// Sets appropriate direction entry.
685 /// Set consistent to false.
686 bool exactSIVtest(const SCEV
*SrcCoeff
,
687 const SCEV
*DstCoeff
,
688 const SCEV
*SrcConst
,
689 const SCEV
*DstConst
,
690 const Loop
*CurrentLoop
,
692 FullDependence
&Result
,
693 Constraint
&NewConstraint
) const;
695 /// weakZeroSrcSIVtest - Tests the weak-zero SIV subscript pair
696 /// (Src and Dst) for dependence.
697 /// Things of the form [c1] and [c2 + a*i],
698 /// where i is an induction variable, c1 and c2 are loop invariant,
699 /// and a is a constant. See also weakZeroDstSIVtest.
700 /// Returns true if any possible dependence is disproved.
701 /// If there might be a dependence, returns false.
702 /// Sets appropriate direction entry.
703 /// Set consistent to false.
704 /// If loop peeling will break the dependence, mark appropriately.
705 bool weakZeroSrcSIVtest(const SCEV
*DstCoeff
,
706 const SCEV
*SrcConst
,
707 const SCEV
*DstConst
,
708 const Loop
*CurrentLoop
,
710 FullDependence
&Result
,
711 Constraint
&NewConstraint
) const;
713 /// weakZeroDstSIVtest - Tests the weak-zero SIV subscript pair
714 /// (Src and Dst) for dependence.
715 /// Things of the form [c1 + a*i] and [c2],
716 /// where i is an induction variable, c1 and c2 are loop invariant,
717 /// and a is a constant. See also weakZeroSrcSIVtest.
718 /// Returns true if any possible dependence is disproved.
719 /// If there might be a dependence, returns false.
720 /// Sets appropriate direction entry.
721 /// Set consistent to false.
722 /// If loop peeling will break the dependence, mark appropriately.
723 bool weakZeroDstSIVtest(const SCEV
*SrcCoeff
,
724 const SCEV
*SrcConst
,
725 const SCEV
*DstConst
,
726 const Loop
*CurrentLoop
,
728 FullDependence
&Result
,
729 Constraint
&NewConstraint
) const;
731 /// exactRDIVtest - Tests the RDIV subscript pair for dependence.
732 /// Things of the form [c1 + a*i] and [c2 + b*j],
733 /// where i and j are induction variable, c1 and c2 are loop invariant,
734 /// and a and b are constants.
735 /// Returns true if any possible dependence is disproved.
736 /// Marks the result as inconsistent.
737 /// Works in some cases that symbolicRDIVtest doesn't,
739 bool exactRDIVtest(const SCEV
*SrcCoeff
,
740 const SCEV
*DstCoeff
,
741 const SCEV
*SrcConst
,
742 const SCEV
*DstConst
,
745 FullDependence
&Result
) const;
747 /// symbolicRDIVtest - Tests the RDIV subscript pair for dependence.
748 /// Things of the form [c1 + a*i] and [c2 + b*j],
749 /// where i and j are induction variable, c1 and c2 are loop invariant,
750 /// and a and b are constants.
751 /// Returns true if any possible dependence is disproved.
752 /// Marks the result as inconsistent.
753 /// Works in some cases that exactRDIVtest doesn't,
754 /// and vice versa. Can also be used as a backup for
755 /// ordinary SIV tests.
756 bool symbolicRDIVtest(const SCEV
*SrcCoeff
,
757 const SCEV
*DstCoeff
,
758 const SCEV
*SrcConst
,
759 const SCEV
*DstConst
,
761 const Loop
*DstLoop
) const;
763 /// gcdMIVtest - Tests an MIV subscript pair for dependence.
764 /// Returns true if any possible dependence is disproved.
765 /// Marks the result as inconsistent.
766 /// Can sometimes disprove the equal direction for 1 or more loops.
767 // Can handle some symbolics that even the SIV tests don't get,
768 /// so we use it as a backup for everything.
769 bool gcdMIVtest(const SCEV
*Src
,
771 FullDependence
&Result
) const;
773 /// banerjeeMIVtest - Tests an MIV subscript pair for dependence.
774 /// Returns true if any possible dependence is disproved.
775 /// Marks the result as inconsistent.
776 /// Computes directions.
777 bool banerjeeMIVtest(const SCEV
*Src
,
779 const SmallBitVector
&Loops
,
780 FullDependence
&Result
) const;
782 /// collectCoefficientInfo - Walks through the subscript,
783 /// collecting each coefficient, the associated loop bounds,
784 /// and recording its positive and negative parts for later use.
785 CoefficientInfo
*collectCoeffInfo(const SCEV
*Subscript
,
787 const SCEV
*&Constant
) const;
789 /// getPositivePart - X^+ = max(X, 0).
791 const SCEV
*getPositivePart(const SCEV
*X
) const;
793 /// getNegativePart - X^- = min(X, 0).
795 const SCEV
*getNegativePart(const SCEV
*X
) const;
797 /// getLowerBound - Looks through all the bounds info and
798 /// computes the lower bound given the current direction settings
800 const SCEV
*getLowerBound(BoundInfo
*Bound
) const;
802 /// getUpperBound - Looks through all the bounds info and
803 /// computes the upper bound given the current direction settings
805 const SCEV
*getUpperBound(BoundInfo
*Bound
) const;
807 /// exploreDirections - Hierarchically expands the direction vector
808 /// search space, combining the directions of discovered dependences
809 /// in the DirSet field of Bound. Returns the number of distinct
810 /// dependences discovered. If the dependence is disproved,
811 /// it will return 0.
812 unsigned exploreDirections(unsigned Level
,
816 const SmallBitVector
&Loops
,
817 unsigned &DepthExpanded
,
818 const SCEV
*Delta
) const;
820 /// testBounds - Returns true iff the current bounds are plausible.
821 bool testBounds(unsigned char DirKind
,
824 const SCEV
*Delta
) const;
826 /// findBoundsALL - Computes the upper and lower bounds for level K
827 /// using the * direction. Records them in Bound.
828 void findBoundsALL(CoefficientInfo
*A
,
833 /// findBoundsLT - Computes the upper and lower bounds for level K
834 /// using the < direction. Records them in Bound.
835 void findBoundsLT(CoefficientInfo
*A
,
840 /// findBoundsGT - Computes the upper and lower bounds for level K
841 /// using the > direction. Records them in Bound.
842 void findBoundsGT(CoefficientInfo
*A
,
847 /// findBoundsEQ - Computes the upper and lower bounds for level K
848 /// using the = direction. Records them in Bound.
849 void findBoundsEQ(CoefficientInfo
*A
,
854 /// intersectConstraints - Updates X with the intersection
855 /// of the Constraints X and Y. Returns true if X has changed.
856 bool intersectConstraints(Constraint
*X
,
857 const Constraint
*Y
);
859 /// propagate - Review the constraints, looking for opportunities
860 /// to simplify a subscript pair (Src and Dst).
861 /// Return true if some simplification occurs.
862 /// If the simplification isn't exact (that is, if it is conservative
863 /// in terms of dependence), set consistent to false.
864 bool propagate(const SCEV
*&Src
,
866 SmallBitVector
&Loops
,
867 SmallVectorImpl
<Constraint
> &Constraints
,
870 /// propagateDistance - Attempt to propagate a distance
871 /// constraint into a subscript pair (Src and Dst).
872 /// Return true if some simplification occurs.
873 /// If the simplification isn't exact (that is, if it is conservative
874 /// in terms of dependence), set consistent to false.
875 bool propagateDistance(const SCEV
*&Src
,
877 Constraint
&CurConstraint
,
880 /// propagatePoint - Attempt to propagate a point
881 /// constraint into a subscript pair (Src and Dst).
882 /// Return true if some simplification occurs.
883 bool propagatePoint(const SCEV
*&Src
,
885 Constraint
&CurConstraint
);
887 /// propagateLine - Attempt to propagate a line
888 /// constraint into a subscript pair (Src and Dst).
889 /// Return true if some simplification occurs.
890 /// If the simplification isn't exact (that is, if it is conservative
891 /// in terms of dependence), set consistent to false.
892 bool propagateLine(const SCEV
*&Src
,
894 Constraint
&CurConstraint
,
897 /// findCoefficient - Given a linear SCEV,
898 /// return the coefficient corresponding to specified loop.
899 /// If there isn't one, return the SCEV constant 0.
900 /// For example, given a*i + b*j + c*k, returning the coefficient
901 /// corresponding to the j loop would yield b.
902 const SCEV
*findCoefficient(const SCEV
*Expr
,
903 const Loop
*TargetLoop
) const;
905 /// zeroCoefficient - Given a linear SCEV,
906 /// return the SCEV given by zeroing out the coefficient
907 /// corresponding to the specified loop.
908 /// For example, given a*i + b*j + c*k, zeroing the coefficient
909 /// corresponding to the j loop would yield a*i + c*k.
910 const SCEV
*zeroCoefficient(const SCEV
*Expr
,
911 const Loop
*TargetLoop
) const;
913 /// addToCoefficient - Given a linear SCEV Expr,
914 /// return the SCEV given by adding some Value to the
915 /// coefficient corresponding to the specified TargetLoop.
916 /// For example, given a*i + b*j + c*k, adding 1 to the coefficient
917 /// corresponding to the j loop would yield a*i + (b+1)*j + c*k.
918 const SCEV
*addToCoefficient(const SCEV
*Expr
,
919 const Loop
*TargetLoop
,
920 const SCEV
*Value
) const;
922 /// updateDirection - Update direction vector entry
923 /// based on the current constraint.
924 void updateDirection(Dependence::DVEntry
&Level
,
925 const Constraint
&CurConstraint
) const;
927 bool tryDelinearize(Instruction
*Src
, Instruction
*Dst
,
928 SmallVectorImpl
<Subscript
> &Pair
);
929 }; // class DependenceInfo
931 /// AnalysisPass to compute dependence information in a function
932 class DependenceAnalysis
: public AnalysisInfoMixin
<DependenceAnalysis
> {
934 typedef DependenceInfo Result
;
935 Result
run(Function
&F
, FunctionAnalysisManager
&FAM
);
938 static AnalysisKey Key
;
939 friend struct AnalysisInfoMixin
<DependenceAnalysis
>;
940 }; // class DependenceAnalysis
942 /// Printer pass to dump DA results.
943 struct DependenceAnalysisPrinterPass
944 : public PassInfoMixin
<DependenceAnalysisPrinterPass
> {
945 DependenceAnalysisPrinterPass(raw_ostream
&OS
) : OS(OS
) {}
947 PreservedAnalyses
run(Function
&F
, FunctionAnalysisManager
&FAM
);
951 }; // class DependenceAnalysisPrinterPass
953 /// Legacy pass manager pass to access dependence information
954 class DependenceAnalysisWrapperPass
: public FunctionPass
{
956 static char ID
; // Class identification, replacement for typeinfo
957 DependenceAnalysisWrapperPass() : FunctionPass(ID
) {
958 initializeDependenceAnalysisWrapperPassPass(
959 *PassRegistry::getPassRegistry());
962 bool runOnFunction(Function
&F
) override
;
963 void releaseMemory() override
;
964 void getAnalysisUsage(AnalysisUsage
&) const override
;
965 void print(raw_ostream
&, const Module
* = nullptr) const override
;
966 DependenceInfo
&getDI() const;
969 std::unique_ptr
<DependenceInfo
> info
;
970 }; // class DependenceAnalysisWrapperPass
972 /// createDependenceAnalysisPass - This creates an instance of the
973 /// DependenceAnalysis wrapper pass.
974 FunctionPass
*createDependenceAnalysisWrapperPass();