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llvm-mirror/include/llvm/Analysis/DependenceAnalysis.h
Bardia Mahjour 4af1e9e981 [DA] Delinearization of fixed-size multi-dimensional arrays 
Summary:
Currently the dependence analysis in LLVM is unable to compute accurate
dependence vectors for multi-dimensional fixed size arrays.
This is mainly because the delinearization algorithm in scalar evolution
relies on parametric terms to be present in the access functions. In the
case of fixed size arrays such parametric terms are not present, but we
can use the indexes from GEP instructions to recover the subscripts for
each dimension of the arrays. This patch adds this ability under the
existing option `-da-disable-delinearization-checks`.

Authored By: bmahjour

Reviewer: Meinersbur, sebpop, fhahn, dmgreen, grosser, etiotto, bollu

Reviewed By: Meinersbur

Subscribers: hiraditya, arphaman, Whitney, ppc-slack, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D72178
2020-02-27 10:29:01 -05:00

1000 lines
42 KiB
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//===-- llvm/Analysis/DependenceAnalysis.h -------------------- -*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// DependenceAnalysis is an LLVM pass that analyses dependences between memory
// accesses. Currently, it is an implementation of the approach described in
//
// Practical Dependence Testing
// Goff, Kennedy, Tseng
// PLDI 1991
//
// There's a single entry point that analyzes the dependence between a pair
// of memory references in a function, returning either NULL, for no dependence,
// or a more-or-less detailed description of the dependence between them.
//
// This pass exists to support the DependenceGraph pass. There are two separate
// passes because there's a useful separation of concerns. A dependence exists
// if two conditions are met:
//
// 1) Two instructions reference the same memory location, and
// 2) There is a flow of control leading from one instruction to the other.
//
// DependenceAnalysis attacks the first condition; DependenceGraph will attack
// the second (it's not yet ready).
//
// Please note that this is work in progress and the interface is subject to
// change.
//
// Plausible changes:
// Return a set of more precise dependences instead of just one dependence
// summarizing all.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ANALYSIS_DEPENDENCEANALYSIS_H
#define LLVM_ANALYSIS_DEPENDENCEANALYSIS_H
#include "llvm/ADT/SmallBitVector.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/IR/Instructions.h"
#include "llvm/Pass.h"
namespace llvm {
template <typename T> class ArrayRef;
class Loop;
class LoopInfo;
class ScalarEvolution;
class SCEV;
class SCEVConstant;
class raw_ostream;
/// Dependence - This class represents a dependence between two memory
/// memory references in a function. It contains minimal information and
/// is used in the very common situation where the compiler is unable to
/// determine anything beyond the existence of a dependence; that is, it
/// represents a confused dependence (see also FullDependence). In most
/// cases (for output, flow, and anti dependences), the dependence implies
/// an ordering, where the source must precede the destination; in contrast,
/// input dependences are unordered.
///
/// When a dependence graph is built, each Dependence will be a member of
/// the set of predecessor edges for its destination instruction and a set
/// if successor edges for its source instruction. These sets are represented
/// as singly-linked lists, with the "next" fields stored in the dependence
/// itelf.
class Dependence {
protected:
Dependence(Dependence &&) = default;
Dependence &operator=(Dependence &&) = default;
public:
Dependence(Instruction *Source,
Instruction *Destination) :
Src(Source),
Dst(Destination),
NextPredecessor(nullptr),
NextSuccessor(nullptr) {}
virtual ~Dependence() {}
/// Dependence::DVEntry - Each level in the distance/direction vector
/// has a direction (or perhaps a union of several directions), and
/// perhaps a distance.
struct DVEntry {
enum { NONE = 0,
LT = 1,
EQ = 2,
LE = 3,
GT = 4,
NE = 5,
GE = 6,
ALL = 7 };
unsigned char Direction : 3; // Init to ALL, then refine.
bool Scalar : 1; // Init to true.
bool PeelFirst : 1; // Peeling the first iteration will break dependence.
bool PeelLast : 1; // Peeling the last iteration will break the dependence.
bool Splitable : 1; // Splitting the loop will break dependence.
const SCEV *Distance; // NULL implies no distance available.
DVEntry() : Direction(ALL), Scalar(true), PeelFirst(false),
PeelLast(false), Splitable(false), Distance(nullptr) { }
};
/// getSrc - Returns the source instruction for this dependence.
///
Instruction *getSrc() const { return Src; }
/// getDst - Returns the destination instruction for this dependence.
///
Instruction *getDst() const { return Dst; }
/// isInput - Returns true if this is an input dependence.
///
bool isInput() const;
/// isOutput - Returns true if this is an output dependence.
///
bool isOutput() const;
/// isFlow - Returns true if this is a flow (aka true) dependence.
///
bool isFlow() const;
/// isAnti - Returns true if this is an anti dependence.
///
bool isAnti() const;
/// isOrdered - Returns true if dependence is Output, Flow, or Anti
///
bool isOrdered() const { return isOutput() || isFlow() || isAnti(); }
/// isUnordered - Returns true if dependence is Input
///
bool isUnordered() const { return isInput(); }
/// isLoopIndependent - Returns true if this is a loop-independent
/// dependence.
virtual bool isLoopIndependent() const { return true; }
/// isConfused - Returns true if this dependence is confused
/// (the compiler understands nothing and makes worst-case
/// assumptions).
virtual bool isConfused() const { return true; }
/// isConsistent - Returns true if this dependence is consistent
/// (occurs every time the source and destination are executed).
virtual bool isConsistent() const { return false; }
/// getLevels - Returns the number of common loops surrounding the
/// source and destination of the dependence.
virtual unsigned getLevels() const { return 0; }
/// getDirection - Returns the direction associated with a particular
/// level.
virtual unsigned getDirection(unsigned Level) const { return DVEntry::ALL; }
/// getDistance - Returns the distance (or NULL) associated with a
/// particular level.
virtual const SCEV *getDistance(unsigned Level) const { return nullptr; }
/// isPeelFirst - Returns true if peeling the first iteration from
/// this loop will break this dependence.
virtual bool isPeelFirst(unsigned Level) const { return false; }
/// isPeelLast - Returns true if peeling the last iteration from
/// this loop will break this dependence.
virtual bool isPeelLast(unsigned Level) const { return false; }
/// isSplitable - Returns true if splitting this loop will break
/// the dependence.
virtual bool isSplitable(unsigned Level) const { return false; }
/// isScalar - Returns true if a particular level is scalar; that is,
/// if no subscript in the source or destination mention the induction
/// variable associated with the loop at this level.
virtual bool isScalar(unsigned Level) const;
/// getNextPredecessor - Returns the value of the NextPredecessor
/// field.
const Dependence *getNextPredecessor() const { return NextPredecessor; }
/// getNextSuccessor - Returns the value of the NextSuccessor
/// field.
const Dependence *getNextSuccessor() const { return NextSuccessor; }
/// setNextPredecessor - Sets the value of the NextPredecessor
/// field.
void setNextPredecessor(const Dependence *pred) { NextPredecessor = pred; }
/// setNextSuccessor - Sets the value of the NextSuccessor
/// field.
void setNextSuccessor(const Dependence *succ) { NextSuccessor = succ; }
/// dump - For debugging purposes, dumps a dependence to OS.
///
void dump(raw_ostream &OS) const;
private:
Instruction *Src, *Dst;
const Dependence *NextPredecessor, *NextSuccessor;
friend class DependenceInfo;
};
/// FullDependence - This class represents a dependence between two memory
/// references in a function. It contains detailed information about the
/// dependence (direction vectors, etc.) and is used when the compiler is
/// able to accurately analyze the interaction of the references; that is,
/// it is not a confused dependence (see Dependence). In most cases
/// (for output, flow, and anti dependences), the dependence implies an
/// ordering, where the source must precede the destination; in contrast,
/// input dependences are unordered.
class FullDependence final : public Dependence {
public:
FullDependence(Instruction *Src, Instruction *Dst, bool LoopIndependent,
unsigned Levels);
/// isLoopIndependent - Returns true if this is a loop-independent
/// dependence.
bool isLoopIndependent() const override { return LoopIndependent; }
/// isConfused - Returns true if this dependence is confused
/// (the compiler understands nothing and makes worst-case
/// assumptions).
bool isConfused() const override { return false; }
/// isConsistent - Returns true if this dependence is consistent
/// (occurs every time the source and destination are executed).
bool isConsistent() const override { return Consistent; }
/// getLevels - Returns the number of common loops surrounding the
/// source and destination of the dependence.
unsigned getLevels() const override { return Levels; }
/// getDirection - Returns the direction associated with a particular
/// level.
unsigned getDirection(unsigned Level) const override;
/// getDistance - Returns the distance (or NULL) associated with a
/// particular level.
const SCEV *getDistance(unsigned Level) const override;
/// isPeelFirst - Returns true if peeling the first iteration from
/// this loop will break this dependence.
bool isPeelFirst(unsigned Level) const override;
/// isPeelLast - Returns true if peeling the last iteration from
/// this loop will break this dependence.
bool isPeelLast(unsigned Level) const override;
/// isSplitable - Returns true if splitting the loop will break
/// the dependence.
bool isSplitable(unsigned Level) const override;
/// isScalar - Returns true if a particular level is scalar; that is,
/// if no subscript in the source or destination mention the induction
/// variable associated with the loop at this level.
bool isScalar(unsigned Level) const override;
private:
unsigned short Levels;
bool LoopIndependent;
bool Consistent; // Init to true, then refine.
std::unique_ptr<DVEntry[]> DV;
friend class DependenceInfo;
};
/// DependenceInfo - This class is the main dependence-analysis driver.
///
class DependenceInfo {
public:
DependenceInfo(Function *F, AliasAnalysis *AA, ScalarEvolution *SE,
LoopInfo *LI)
: AA(AA), SE(SE), LI(LI), F(F) {}
/// Handle transitive invalidation when the cached analysis results go away.
bool invalidate(Function &F, const PreservedAnalyses &PA,
FunctionAnalysisManager::Invalidator &Inv);
/// depends - Tests for a dependence between the Src and Dst instructions.
/// Returns NULL if no dependence; otherwise, returns a Dependence (or a
/// FullDependence) with as much information as can be gleaned.
/// The flag PossiblyLoopIndependent should be set by the caller
/// if it appears that control flow can reach from Src to Dst
/// without traversing a loop back edge.
std::unique_ptr<Dependence> depends(Instruction *Src,
Instruction *Dst,
bool PossiblyLoopIndependent);
/// getSplitIteration - Give a dependence that's splittable at some
/// particular level, return the iteration that should be used to split
/// the loop.
///
/// Generally, the dependence analyzer will be used to build
/// a dependence graph for a function (basically a map from instructions
/// to dependences). Looking for cycles in the graph shows us loops
/// that cannot be trivially vectorized/parallelized.
///
/// We can try to improve the situation by examining all the dependences
/// that make up the cycle, looking for ones we can break.
/// Sometimes, peeling the first or last iteration of a loop will break
/// dependences, and there are flags for those possibilities.
/// Sometimes, splitting a loop at some other iteration will do the trick,
/// and we've got a flag for that case. Rather than waste the space to
/// record the exact iteration (since we rarely know), we provide
/// a method that calculates the iteration. It's a drag that it must work
/// from scratch, but wonderful in that it's possible.
///
/// Here's an example:
///
/// for (i = 0; i < 10; i++)
/// A[i] = ...
/// ... = A[11 - i]
///
/// There's a loop-carried flow dependence from the store to the load,
/// found by the weak-crossing SIV test. The dependence will have a flag,
/// indicating that the dependence can be broken by splitting the loop.
/// Calling getSplitIteration will return 5.
/// Splitting the loop breaks the dependence, like so:
///
/// for (i = 0; i <= 5; i++)
/// A[i] = ...
/// ... = A[11 - i]
/// for (i = 6; i < 10; i++)
/// A[i] = ...
/// ... = A[11 - i]
///
/// breaks the dependence and allows us to vectorize/parallelize
/// both loops.
const SCEV *getSplitIteration(const Dependence &Dep, unsigned Level);
Function *getFunction() const { return F; }
private:
AliasAnalysis *AA;
ScalarEvolution *SE;
LoopInfo *LI;
Function *F;
/// Subscript - This private struct represents a pair of subscripts from
/// a pair of potentially multi-dimensional array references. We use a
/// vector of them to guide subscript partitioning.
struct Subscript {
const SCEV *Src;
const SCEV *Dst;
enum ClassificationKind { ZIV, SIV, RDIV, MIV, NonLinear } Classification;
SmallBitVector Loops;
SmallBitVector GroupLoops;
SmallBitVector Group;
};
struct CoefficientInfo {
const SCEV *Coeff;
const SCEV *PosPart;
const SCEV *NegPart;
const SCEV *Iterations;
};
struct BoundInfo {
const SCEV *Iterations;
const SCEV *Upper[8];
const SCEV *Lower[8];
unsigned char Direction;
unsigned char DirSet;
};
/// Constraint - This private class represents a constraint, as defined
/// in the paper
///
/// Practical Dependence Testing
/// Goff, Kennedy, Tseng
/// PLDI 1991
///
/// There are 5 kinds of constraint, in a hierarchy.
/// 1) Any - indicates no constraint, any dependence is possible.
/// 2) Line - A line ax + by = c, where a, b, and c are parameters,
/// representing the dependence equation.
/// 3) Distance - The value d of the dependence distance;
/// 4) Point - A point <x, y> representing the dependence from
/// iteration x to iteration y.
/// 5) Empty - No dependence is possible.
class Constraint {
private:
enum ConstraintKind { Empty, Point, Distance, Line, Any } Kind;
ScalarEvolution *SE;
const SCEV *A;
const SCEV *B;
const SCEV *C;
const Loop *AssociatedLoop;
public:
/// isEmpty - Return true if the constraint is of kind Empty.
bool isEmpty() const { return Kind == Empty; }
/// isPoint - Return true if the constraint is of kind Point.
bool isPoint() const { return Kind == Point; }
/// isDistance - Return true if the constraint is of kind Distance.
bool isDistance() const { return Kind == Distance; }
/// isLine - Return true if the constraint is of kind Line.
/// Since Distance's can also be represented as Lines, we also return
/// true if the constraint is of kind Distance.
bool isLine() const { return Kind == Line || Kind == Distance; }
/// isAny - Return true if the constraint is of kind Any;
bool isAny() const { return Kind == Any; }
/// getX - If constraint is a point <X, Y>, returns X.
/// Otherwise assert.
const SCEV *getX() const;
/// getY - If constraint is a point <X, Y>, returns Y.
/// Otherwise assert.
const SCEV *getY() const;
/// getA - If constraint is a line AX + BY = C, returns A.
/// Otherwise assert.
const SCEV *getA() const;
/// getB - If constraint is a line AX + BY = C, returns B.
/// Otherwise assert.
const SCEV *getB() const;
/// getC - If constraint is a line AX + BY = C, returns C.
/// Otherwise assert.
const SCEV *getC() const;
/// getD - If constraint is a distance, returns D.
/// Otherwise assert.
const SCEV *getD() const;
/// getAssociatedLoop - Returns the loop associated with this constraint.
const Loop *getAssociatedLoop() const;
/// setPoint - Change a constraint to Point.
void setPoint(const SCEV *X, const SCEV *Y, const Loop *CurrentLoop);
/// setLine - Change a constraint to Line.
void setLine(const SCEV *A, const SCEV *B,
const SCEV *C, const Loop *CurrentLoop);
/// setDistance - Change a constraint to Distance.
void setDistance(const SCEV *D, const Loop *CurrentLoop);
/// setEmpty - Change a constraint to Empty.
void setEmpty();
/// setAny - Change a constraint to Any.
void setAny(ScalarEvolution *SE);
/// dump - For debugging purposes. Dumps the constraint
/// out to OS.
void dump(raw_ostream &OS) const;
};
/// establishNestingLevels - Examines the loop nesting of the Src and Dst
/// instructions and establishes their shared loops. Sets the variables
/// CommonLevels, SrcLevels, and MaxLevels.
/// The source and destination instructions needn't be contained in the same
/// loop. The routine establishNestingLevels finds the level of most deeply
/// nested loop that contains them both, CommonLevels. An instruction that's
/// not contained in a loop is at level = 0. MaxLevels is equal to the level
/// of the source plus the level of the destination, minus CommonLevels.
/// This lets us allocate vectors MaxLevels in length, with room for every
/// distinct loop referenced in both the source and destination subscripts.
/// The variable SrcLevels is the nesting depth of the source instruction.
/// It's used to help calculate distinct loops referenced by the destination.
/// Here's the map from loops to levels:
/// 0 - unused
/// 1 - outermost common loop
/// ... - other common loops
/// CommonLevels - innermost common loop
/// ... - loops containing Src but not Dst
/// SrcLevels - innermost loop containing Src but not Dst
/// ... - loops containing Dst but not Src
/// MaxLevels - innermost loop containing Dst but not Src
/// Consider the follow code fragment:
/// for (a = ...) {
/// for (b = ...) {
/// for (c = ...) {
/// for (d = ...) {
/// A[] = ...;
/// }
/// }
/// for (e = ...) {
/// for (f = ...) {
/// for (g = ...) {
/// ... = A[];
/// }
/// }
/// }
/// }
/// }
/// If we're looking at the possibility of a dependence between the store
/// to A (the Src) and the load from A (the Dst), we'll note that they
/// have 2 loops in common, so CommonLevels will equal 2 and the direction
/// vector for Result will have 2 entries. SrcLevels = 4 and MaxLevels = 7.
/// A map from loop names to level indices would look like
/// a - 1
/// b - 2 = CommonLevels
/// c - 3
/// d - 4 = SrcLevels
/// e - 5
/// f - 6
/// g - 7 = MaxLevels
void establishNestingLevels(const Instruction *Src,
const Instruction *Dst);
unsigned CommonLevels, SrcLevels, MaxLevels;
/// mapSrcLoop - Given one of the loops containing the source, return
/// its level index in our numbering scheme.
unsigned mapSrcLoop(const Loop *SrcLoop) const;
/// mapDstLoop - Given one of the loops containing the destination,
/// return its level index in our numbering scheme.
unsigned mapDstLoop(const Loop *DstLoop) const;
/// isLoopInvariant - Returns true if Expression is loop invariant
/// in LoopNest.
bool isLoopInvariant(const SCEV *Expression, const Loop *LoopNest) const;
/// Makes sure all subscript pairs share the same integer type by
/// sign-extending as necessary.
/// Sign-extending a subscript is safe because getelementptr assumes the
/// array subscripts are signed.
void unifySubscriptType(ArrayRef<Subscript *> Pairs);
/// removeMatchingExtensions - Examines a subscript pair.
/// If the source and destination are identically sign (or zero)
/// extended, it strips off the extension in an effort to
/// simplify the actual analysis.
void removeMatchingExtensions(Subscript *Pair);
/// collectCommonLoops - Finds the set of loops from the LoopNest that
/// have a level <= CommonLevels and are referred to by the SCEV Expression.
void collectCommonLoops(const SCEV *Expression,
const Loop *LoopNest,
SmallBitVector &Loops) const;
/// checkSrcSubscript - Examines the SCEV Src, returning true iff it's
/// linear. Collect the set of loops mentioned by Src.
bool checkSrcSubscript(const SCEV *Src,
const Loop *LoopNest,
SmallBitVector &Loops);
/// checkDstSubscript - Examines the SCEV Dst, returning true iff it's
/// linear. Collect the set of loops mentioned by Dst.
bool checkDstSubscript(const SCEV *Dst,
const Loop *LoopNest,
SmallBitVector &Loops);
/// isKnownPredicate - Compare X and Y using the predicate Pred.
/// Basically a wrapper for SCEV::isKnownPredicate,
/// but tries harder, especially in the presence of sign and zero
/// extensions and symbolics.
bool isKnownPredicate(ICmpInst::Predicate Pred,
const SCEV *X,
const SCEV *Y) const;
/// isKnownLessThan - Compare to see if S is less than Size
/// Another wrapper for isKnownNegative(S - max(Size, 1)) with some extra
/// checking if S is an AddRec and we can prove lessthan using the loop
/// bounds.
bool isKnownLessThan(const SCEV *S, const SCEV *Size) const;
/// isKnownNonNegative - Compare to see if S is known not to be negative
/// Uses the fact that S comes from Ptr, which may be an inbound GEP,
/// Proving there is no wrapping going on.
bool isKnownNonNegative(const SCEV *S, const Value *Ptr) const;
/// collectUpperBound - All subscripts are the same type (on my machine,
/// an i64). The loop bound may be a smaller type. collectUpperBound
/// find the bound, if available, and zero extends it to the Type T.
/// (I zero extend since the bound should always be >= 0.)
/// If no upper bound is available, return NULL.
const SCEV *collectUpperBound(const Loop *l, Type *T) const;
/// collectConstantUpperBound - Calls collectUpperBound(), then
/// attempts to cast it to SCEVConstant. If the cast fails,
/// returns NULL.
const SCEVConstant *collectConstantUpperBound(const Loop *l, Type *T) const;
/// classifyPair - Examines the subscript pair (the Src and Dst SCEVs)
/// and classifies it as either ZIV, SIV, RDIV, MIV, or Nonlinear.
/// Collects the associated loops in a set.
Subscript::ClassificationKind classifyPair(const SCEV *Src,
const Loop *SrcLoopNest,
const SCEV *Dst,
const Loop *DstLoopNest,
SmallBitVector &Loops);
/// testZIV - Tests the ZIV subscript pair (Src and Dst) for dependence.
/// Returns true if any possible dependence is disproved.
/// If there might be a dependence, returns false.
/// If the dependence isn't proven to exist,
/// marks the Result as inconsistent.
bool testZIV(const SCEV *Src,
const SCEV *Dst,
FullDependence &Result) const;
/// testSIV - Tests the SIV subscript pair (Src and Dst) for dependence.
/// Things of the form [c1 + a1*i] and [c2 + a2*j], where
/// i and j are induction variables, c1 and c2 are loop invariant,
/// and a1 and a2 are constant.
/// Returns true if any possible dependence is disproved.
/// If there might be a dependence, returns false.
/// Sets appropriate direction vector entry and, when possible,
/// the distance vector entry.
/// If the dependence isn't proven to exist,
/// marks the Result as inconsistent.
bool testSIV(const SCEV *Src,
const SCEV *Dst,
unsigned &Level,
FullDependence &Result,
Constraint &NewConstraint,
const SCEV *&SplitIter) const;
/// testRDIV - Tests the RDIV subscript pair (Src and Dst) for dependence.
/// Things of the form [c1 + a1*i] and [c2 + a2*j]
/// where i and j are induction variables, c1 and c2 are loop invariant,
/// and a1 and a2 are constant.
/// With minor algebra, this test can also be used for things like
/// [c1 + a1*i + a2*j][c2].
/// Returns true if any possible dependence is disproved.
/// If there might be a dependence, returns false.
/// Marks the Result as inconsistent.
bool testRDIV(const SCEV *Src,
const SCEV *Dst,
FullDependence &Result) const;
/// testMIV - Tests the MIV subscript pair (Src and Dst) for dependence.
/// Returns true if dependence disproved.
/// Can sometimes refine direction vectors.
bool testMIV(const SCEV *Src,
const SCEV *Dst,
const SmallBitVector &Loops,
FullDependence &Result) const;
/// strongSIVtest - Tests the strong SIV subscript pair (Src and Dst)
/// for dependence.
/// Things of the form [c1 + a*i] and [c2 + a*i],
/// where i is an induction variable, c1 and c2 are loop invariant,
/// and a is a constant
/// Returns true if any possible dependence is disproved.
/// If there might be a dependence, returns false.
/// Sets appropriate direction and distance.
bool strongSIVtest(const SCEV *Coeff,
const SCEV *SrcConst,
const SCEV *DstConst,
const Loop *CurrentLoop,
unsigned Level,
FullDependence &Result,
Constraint &NewConstraint) const;
/// weakCrossingSIVtest - Tests the weak-crossing SIV subscript pair
/// (Src and Dst) for dependence.
/// Things of the form [c1 + a*i] and [c2 - a*i],
/// where i is an induction variable, c1 and c2 are loop invariant,
/// and a is a constant.
/// Returns true if any possible dependence is disproved.
/// If there might be a dependence, returns false.
/// Sets appropriate direction entry.
/// Set consistent to false.
/// Marks the dependence as splitable.
bool weakCrossingSIVtest(const SCEV *SrcCoeff,
const SCEV *SrcConst,
const SCEV *DstConst,
const Loop *CurrentLoop,
unsigned Level,
FullDependence &Result,
Constraint &NewConstraint,
const SCEV *&SplitIter) const;
/// ExactSIVtest - Tests the SIV subscript pair
/// (Src and Dst) for dependence.
/// Things of the form [c1 + a1*i] and [c2 + a2*i],
/// where i is an induction variable, c1 and c2 are loop invariant,
/// and a1 and a2 are constant.
/// Returns true if any possible dependence is disproved.
/// If there might be a dependence, returns false.
/// Sets appropriate direction entry.
/// Set consistent to false.
bool exactSIVtest(const SCEV *SrcCoeff,
const SCEV *DstCoeff,
const SCEV *SrcConst,
const SCEV *DstConst,
const Loop *CurrentLoop,
unsigned Level,
FullDependence &Result,
Constraint &NewConstraint) const;
/// weakZeroSrcSIVtest - Tests the weak-zero SIV subscript pair
/// (Src and Dst) for dependence.
/// Things of the form [c1] and [c2 + a*i],
/// where i is an induction variable, c1 and c2 are loop invariant,
/// and a is a constant. See also weakZeroDstSIVtest.
/// Returns true if any possible dependence is disproved.
/// If there might be a dependence, returns false.
/// Sets appropriate direction entry.
/// Set consistent to false.
/// If loop peeling will break the dependence, mark appropriately.
bool weakZeroSrcSIVtest(const SCEV *DstCoeff,
const SCEV *SrcConst,
const SCEV *DstConst,
const Loop *CurrentLoop,
unsigned Level,
FullDependence &Result,
Constraint &NewConstraint) const;
/// weakZeroDstSIVtest - Tests the weak-zero SIV subscript pair
/// (Src and Dst) for dependence.
/// Things of the form [c1 + a*i] and [c2],
/// where i is an induction variable, c1 and c2 are loop invariant,
/// and a is a constant. See also weakZeroSrcSIVtest.
/// Returns true if any possible dependence is disproved.
/// If there might be a dependence, returns false.
/// Sets appropriate direction entry.
/// Set consistent to false.
/// If loop peeling will break the dependence, mark appropriately.
bool weakZeroDstSIVtest(const SCEV *SrcCoeff,
const SCEV *SrcConst,
const SCEV *DstConst,
const Loop *CurrentLoop,
unsigned Level,
FullDependence &Result,
Constraint &NewConstraint) const;
/// exactRDIVtest - Tests the RDIV subscript pair for dependence.
/// Things of the form [c1 + a*i] and [c2 + b*j],
/// where i and j are induction variable, c1 and c2 are loop invariant,
/// and a and b are constants.
/// Returns true if any possible dependence is disproved.
/// Marks the result as inconsistent.
/// Works in some cases that symbolicRDIVtest doesn't,
/// and vice versa.
bool exactRDIVtest(const SCEV *SrcCoeff,
const SCEV *DstCoeff,
const SCEV *SrcConst,
const SCEV *DstConst,
const Loop *SrcLoop,
const Loop *DstLoop,
FullDependence &Result) const;
/// symbolicRDIVtest - Tests the RDIV subscript pair for dependence.
/// Things of the form [c1 + a*i] and [c2 + b*j],
/// where i and j are induction variable, c1 and c2 are loop invariant,
/// and a and b are constants.
/// Returns true if any possible dependence is disproved.
/// Marks the result as inconsistent.
/// Works in some cases that exactRDIVtest doesn't,
/// and vice versa. Can also be used as a backup for
/// ordinary SIV tests.
bool symbolicRDIVtest(const SCEV *SrcCoeff,
const SCEV *DstCoeff,
const SCEV *SrcConst,
const SCEV *DstConst,
const Loop *SrcLoop,
const Loop *DstLoop) const;
/// gcdMIVtest - Tests an MIV subscript pair for dependence.
/// Returns true if any possible dependence is disproved.
/// Marks the result as inconsistent.
/// Can sometimes disprove the equal direction for 1 or more loops.
// Can handle some symbolics that even the SIV tests don't get,
/// so we use it as a backup for everything.
bool gcdMIVtest(const SCEV *Src,
const SCEV *Dst,
FullDependence &Result) const;
/// banerjeeMIVtest - Tests an MIV subscript pair for dependence.
/// Returns true if any possible dependence is disproved.
/// Marks the result as inconsistent.
/// Computes directions.
bool banerjeeMIVtest(const SCEV *Src,
const SCEV *Dst,
const SmallBitVector &Loops,
FullDependence &Result) const;
/// collectCoefficientInfo - Walks through the subscript,
/// collecting each coefficient, the associated loop bounds,
/// and recording its positive and negative parts for later use.
CoefficientInfo *collectCoeffInfo(const SCEV *Subscript,
bool SrcFlag,
const SCEV *&Constant) const;
/// getPositivePart - X^+ = max(X, 0).
///
const SCEV *getPositivePart(const SCEV *X) const;
/// getNegativePart - X^- = min(X, 0).
///
const SCEV *getNegativePart(const SCEV *X) const;
/// getLowerBound - Looks through all the bounds info and
/// computes the lower bound given the current direction settings
/// at each level.
const SCEV *getLowerBound(BoundInfo *Bound) const;
/// getUpperBound - Looks through all the bounds info and
/// computes the upper bound given the current direction settings
/// at each level.
const SCEV *getUpperBound(BoundInfo *Bound) const;
/// exploreDirections - Hierarchically expands the direction vector
/// search space, combining the directions of discovered dependences
/// in the DirSet field of Bound. Returns the number of distinct
/// dependences discovered. If the dependence is disproved,
/// it will return 0.
unsigned exploreDirections(unsigned Level,
CoefficientInfo *A,
CoefficientInfo *B,
BoundInfo *Bound,
const SmallBitVector &Loops,
unsigned &DepthExpanded,
const SCEV *Delta) const;
/// testBounds - Returns true iff the current bounds are plausible.
bool testBounds(unsigned char DirKind,
unsigned Level,
BoundInfo *Bound,
const SCEV *Delta) const;
/// findBoundsALL - Computes the upper and lower bounds for level K
/// using the * direction. Records them in Bound.
void findBoundsALL(CoefficientInfo *A,
CoefficientInfo *B,
BoundInfo *Bound,
unsigned K) const;
/// findBoundsLT - Computes the upper and lower bounds for level K
/// using the < direction. Records them in Bound.
void findBoundsLT(CoefficientInfo *A,
CoefficientInfo *B,
BoundInfo *Bound,
unsigned K) const;
/// findBoundsGT - Computes the upper and lower bounds for level K
/// using the > direction. Records them in Bound.
void findBoundsGT(CoefficientInfo *A,
CoefficientInfo *B,
BoundInfo *Bound,
unsigned K) const;
/// findBoundsEQ - Computes the upper and lower bounds for level K
/// using the = direction. Records them in Bound.
void findBoundsEQ(CoefficientInfo *A,
CoefficientInfo *B,
BoundInfo *Bound,
unsigned K) const;
/// intersectConstraints - Updates X with the intersection
/// of the Constraints X and Y. Returns true if X has changed.
bool intersectConstraints(Constraint *X,
const Constraint *Y);
/// propagate - Review the constraints, looking for opportunities
/// to simplify a subscript pair (Src and Dst).
/// Return true if some simplification occurs.
/// If the simplification isn't exact (that is, if it is conservative
/// in terms of dependence), set consistent to false.
bool propagate(const SCEV *&Src,
const SCEV *&Dst,
SmallBitVector &Loops,
SmallVectorImpl<Constraint> &Constraints,
bool &Consistent);
/// propagateDistance - Attempt to propagate a distance
/// constraint into a subscript pair (Src and Dst).
/// Return true if some simplification occurs.
/// If the simplification isn't exact (that is, if it is conservative
/// in terms of dependence), set consistent to false.
bool propagateDistance(const SCEV *&Src,
const SCEV *&Dst,
Constraint &CurConstraint,
bool &Consistent);
/// propagatePoint - Attempt to propagate a point
/// constraint into a subscript pair (Src and Dst).
/// Return true if some simplification occurs.
bool propagatePoint(const SCEV *&Src,
const SCEV *&Dst,
Constraint &CurConstraint);
/// propagateLine - Attempt to propagate a line
/// constraint into a subscript pair (Src and Dst).
/// Return true if some simplification occurs.
/// If the simplification isn't exact (that is, if it is conservative
/// in terms of dependence), set consistent to false.
bool propagateLine(const SCEV *&Src,
const SCEV *&Dst,
Constraint &CurConstraint,
bool &Consistent);
/// findCoefficient - Given a linear SCEV,
/// return the coefficient corresponding to specified loop.
/// If there isn't one, return the SCEV constant 0.
/// For example, given a*i + b*j + c*k, returning the coefficient
/// corresponding to the j loop would yield b.
const SCEV *findCoefficient(const SCEV *Expr,
const Loop *TargetLoop) const;
/// zeroCoefficient - Given a linear SCEV,
/// return the SCEV given by zeroing out the coefficient
/// corresponding to the specified loop.
/// For example, given a*i + b*j + c*k, zeroing the coefficient
/// corresponding to the j loop would yield a*i + c*k.
const SCEV *zeroCoefficient(const SCEV *Expr,
const Loop *TargetLoop) const;
/// addToCoefficient - Given a linear SCEV Expr,
/// return the SCEV given by adding some Value to the
/// coefficient corresponding to the specified TargetLoop.
/// For example, given a*i + b*j + c*k, adding 1 to the coefficient
/// corresponding to the j loop would yield a*i + (b+1)*j + c*k.
const SCEV *addToCoefficient(const SCEV *Expr,
const Loop *TargetLoop,
const SCEV *Value) const;
/// updateDirection - Update direction vector entry
/// based on the current constraint.
void updateDirection(Dependence::DVEntry &Level,
const Constraint &CurConstraint) const;
/// Given a linear access function, tries to recover subscripts
/// for each dimension of the array element access.
bool tryDelinearize(Instruction *Src, Instruction *Dst,
SmallVectorImpl<Subscript> &Pair);
/// Tries to delinearize access function for a fixed size multi-dimensional
/// array, by deriving subscripts from GEP instructions. Returns true upon
/// success and false otherwise.
bool tryDelinearizeFixedSize(Instruction *Src, Instruction *Dst,
const SCEV *SrcAccessFn,
const SCEV *DstAccessFn,
SmallVectorImpl<const SCEV *> &SrcSubscripts,
SmallVectorImpl<const SCEV *> &DstSubscripts);
/// Tries to delinearize access function for a multi-dimensional array with
/// symbolic runtime sizes.
/// Returns true upon success and false otherwise.
bool tryDelinearizeParametricSize(
Instruction *Src, Instruction *Dst, const SCEV *SrcAccessFn,
const SCEV *DstAccessFn, SmallVectorImpl<const SCEV *> &SrcSubscripts,
SmallVectorImpl<const SCEV *> &DstSubscripts);
/// checkSubscript - Helper function for checkSrcSubscript and
/// checkDstSubscript to avoid duplicate code
bool checkSubscript(const SCEV *Expr, const Loop *LoopNest,
SmallBitVector &Loops, bool IsSrc);
}; // class DependenceInfo
/// AnalysisPass to compute dependence information in a function
class DependenceAnalysis : public AnalysisInfoMixin<DependenceAnalysis> {
public:
typedef DependenceInfo Result;
Result run(Function &F, FunctionAnalysisManager &FAM);
private:
static AnalysisKey Key;
friend struct AnalysisInfoMixin<DependenceAnalysis>;
}; // class DependenceAnalysis
/// Printer pass to dump DA results.
struct DependenceAnalysisPrinterPass
: public PassInfoMixin<DependenceAnalysisPrinterPass> {
DependenceAnalysisPrinterPass(raw_ostream &OS) : OS(OS) {}
PreservedAnalyses run(Function &F, FunctionAnalysisManager &FAM);
private:
raw_ostream &OS;
}; // class DependenceAnalysisPrinterPass
/// Legacy pass manager pass to access dependence information
class DependenceAnalysisWrapperPass : public FunctionPass {
public:
static char ID; // Class identification, replacement for typeinfo
DependenceAnalysisWrapperPass();
bool runOnFunction(Function &F) override;
void releaseMemory() override;
void getAnalysisUsage(AnalysisUsage &) const override;
void print(raw_ostream &, const Module * = nullptr) const override;
DependenceInfo &getDI() const;
private:
std::unique_ptr<DependenceInfo> info;
}; // class DependenceAnalysisWrapperPass
/// createDependenceAnalysisPass - This creates an instance of the
/// DependenceAnalysis wrapper pass.
FunctionPass *createDependenceAnalysisWrapperPass();
} // namespace llvm
#endif
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