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+//===-- 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;
+
+ /// 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
+
+ /// \brief 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
+
+ /// \brief 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