EIC code displayed by LXR master/​include/​llvm/​Analysis/​DependenceAnalysis.h	Source navigation Diff markup Identifier search General search
	Version: master test Revert   Change

File indexing completed on 2026-05-10 08:43:12

 //===-- 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/IR/Instructions.h"
 #include "llvm/IR/PassManager.h"
 #include "llvm/Pass.h"
 
 namespace llvm {
   class AAResults;
   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) {}
     virtual ~Dependence() = default;
 
     /// 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 : unsigned char {
         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 = nullptr; // NULL implies no distance available.
       DVEntry()
           : Direction(ALL), Scalar(true), PeelFirst(false), PeelLast(false),
             Splitable(false) {}
     };
 
     /// 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; }
 
     /// Check if the direction vector is negative. A negative direction
     /// vector means Src and Dst are reversed in the actual program.
     virtual bool isDirectionNegative() const { return false; }
 
     /// If the direction vector is negative, normalize the direction
     /// vector to make it non-negative. Normalization is done by reversing
     /// Src and Dst, plus reversing the dependence directions and distances
     /// in the vector.
     virtual bool normalize(ScalarEvolution *SE) { return false; }
 
     /// 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;
 
   protected:
     Instruction *Src, *Dst;
 
   private:
     const Dependence *NextPredecessor = nullptr, *NextSuccessor = nullptr;
     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;
 
     /// Check if the direction vector is negative. A negative direction
     /// vector means Src and Dst are reversed in the actual program.
     bool isDirectionNegative() const override;
 
     /// If the direction vector is negative, normalize the direction
     /// vector to make it non-negative. Normalization is done by reversing
     /// Src and Dst, plus reversing the dependence directions and distances
     /// in the vector.
     bool normalize(ScalarEvolution *SE) 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, AAResults *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:
     AAResults *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 \p Src and \p Dst access functions for a fixed size
     /// multi-dimensional array. Calls tryDelinearizeFixedSizeImpl() to
     /// delinearize \p Src and \p Dst separately,
     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,
                                   bool NormalizeResults = false)
         : OS(OS), NormalizeResults(NormalizeResults) {}
 
     PreservedAnalyses run(Function &F, FunctionAnalysisManager &FAM);
 
     static bool isRequired() { return true; }
 
   private:
     raw_ostream &OS;
     bool NormalizeResults;
   }; // 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

This page was automatically generated by the 2.3.7 LXR engine. The LXR team