//===-- llvm/Analysis/DependenceAnalysis.h -------------------- -*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// 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) {}
/// 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;
bool tryDelinearize(Instruction *Src, Instruction *Dst,
SmallVectorImpl<Subscript> &Pair);
}; // 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
/// Legacy pass manager pass to access dependence information
class DependenceAnalysisWrapperPass : public FunctionPass {
public:
static char ID; // Class identification, replacement for typeinfo
DependenceAnalysisWrapperPass() : FunctionPass(ID) {
initializeDependenceAnalysisWrapperPassPass(
*PassRegistry::getPassRegistry());
}
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