Coverage Report

Created: 2018-07-19 03:59

/Users/buildslave/jenkins/workspace/clang-stage2-coverage-R/llvm/include/llvm/Analysis/DependenceAnalysis.h
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//===-- llvm/Analysis/DependenceAnalysis.h -------------------- -*- C++ -*-===//
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//
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//                     The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// DependenceAnalysis is an LLVM pass that analyses dependences between memory
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// accesses. Currently, it is an implementation of the approach described in
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//
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//            Practical Dependence Testing
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//            Goff, Kennedy, Tseng
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//            PLDI 1991
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//
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// There's a single entry point that analyzes the dependence between a pair
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// of memory references in a function, returning either NULL, for no dependence,
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// or a more-or-less detailed description of the dependence between them.
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//
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// This pass exists to support the DependenceGraph pass. There are two separate
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// passes because there's a useful separation of concerns. A dependence exists
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// if two conditions are met:
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//
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//    1) Two instructions reference the same memory location, and
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//    2) There is a flow of control leading from one instruction to the other.
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//
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// DependenceAnalysis attacks the first condition; DependenceGraph will attack
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// the second (it's not yet ready).
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//
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// Please note that this is work in progress and the interface is subject to
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// change.
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//
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// Plausible changes:
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//    Return a set of more precise dependences instead of just one dependence
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//    summarizing all.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ANALYSIS_DEPENDENCEANALYSIS_H
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#define LLVM_ANALYSIS_DEPENDENCEANALYSIS_H
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#include "llvm/ADT/SmallBitVector.h"
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#include "llvm/Analysis/AliasAnalysis.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/Pass.h"
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namespace llvm {
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template <typename T> class ArrayRef;
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  class Loop;
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  class LoopInfo;
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  class ScalarEvolution;
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  class SCEV;
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  class SCEVConstant;
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  class raw_ostream;
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  /// Dependence - This class represents a dependence between two memory
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  /// memory references in a function. It contains minimal information and
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  /// is used in the very common situation where the compiler is unable to
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  /// determine anything beyond the existence of a dependence; that is, it
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  /// represents a confused dependence (see also FullDependence). In most
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  /// cases (for output, flow, and anti dependences), the dependence implies
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  /// an ordering, where the source must precede the destination; in contrast,
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  /// input dependences are unordered.
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  ///
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  /// When a dependence graph is built, each Dependence will be a member of
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  /// the set of predecessor edges for its destination instruction and a set
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  /// if successor edges for its source instruction. These sets are represented
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  /// as singly-linked lists, with the "next" fields stored in the dependence
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  /// itelf.
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  class Dependence {
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  protected:
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429
    Dependence(Dependence &&) = default;
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    Dependence &operator=(Dependence &&) = default;
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  public:
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    Dependence(Instruction *Source,
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               Instruction *Destination) :
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      Src(Source),
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      Dst(Destination),
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      NextPredecessor(nullptr),
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1.46k
      NextSuccessor(nullptr) {}
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1.89k
    virtual ~Dependence() {}
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    /// Dependence::DVEntry - Each level in the distance/direction vector
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    /// has a direction (or perhaps a union of several directions), and
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    /// perhaps a distance.
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    struct DVEntry {
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      enum { NONE = 0,
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             LT = 1,
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             EQ = 2,
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             LE = 3,
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             GT = 4,
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             NE = 5,
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             GE = 6,
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             ALL = 7 };
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      unsigned char Direction : 3; // Init to ALL, then refine.
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      bool Scalar    : 1; // Init to true.
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      bool PeelFirst : 1; // Peeling the first iteration will break dependence.
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      bool PeelLast  : 1; // Peeling the last iteration will break the dependence.
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      bool Splitable : 1; // Splitting the loop will break dependence.
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      const SCEV *Distance; // NULL implies no distance available.
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      DVEntry() : Direction(ALL), Scalar(true), PeelFirst(false),
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1.37k
                  PeelLast(false), Splitable(false), Distance(nullptr) { }
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    };
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    /// getSrc - Returns the source instruction for this dependence.
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    ///
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3
    Instruction *getSrc() const { return Src; }
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    /// getDst - Returns the destination instruction for this dependence.
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    ///
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3
    Instruction *getDst() const { return Dst; }
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    /// isInput - Returns true if this is an input dependence.
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    ///
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    bool isInput() const;
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    /// isOutput - Returns true if this is an output dependence.
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    ///
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    bool isOutput() const;
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    /// isFlow - Returns true if this is a flow (aka true) dependence.
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    ///
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    bool isFlow() const;
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    /// isAnti - Returns true if this is an anti dependence.
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    ///
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    bool isAnti() const;
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    /// isOrdered - Returns true if dependence is Output, Flow, or Anti
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    ///
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0
    bool isOrdered() const { return isOutput() || isFlow() || isAnti(); }
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    /// isUnordered - Returns true if dependence is Input
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    ///
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0
    bool isUnordered() const { return isInput(); }
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    /// isLoopIndependent - Returns true if this is a loop-independent
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    /// dependence.
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0
    virtual bool isLoopIndependent() const { return true; }
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    /// isConfused - Returns true if this dependence is confused
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    /// (the compiler understands nothing and makes worst-case
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    /// assumptions).
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531
    virtual bool isConfused() const { return true; }
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    /// isConsistent - Returns true if this dependence is consistent
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    /// (occurs every time the source and destination are executed).
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0
    virtual bool isConsistent() const { return false; }
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    /// getLevels - Returns the number of common loops surrounding the
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    /// source and destination of the dependence.
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529
    virtual unsigned getLevels() const { return 0; }
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    /// getDirection - Returns the direction associated with a particular
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    /// level.
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    virtual unsigned getDirection(unsigned Level) const { return DVEntry::ALL; }
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    /// getDistance - Returns the distance (or NULL) associated with a
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    /// particular level.
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0
    virtual const SCEV *getDistance(unsigned Level) const { return nullptr; }
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    /// isPeelFirst - Returns true if peeling the first iteration from
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    /// this loop will break this dependence.
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0
    virtual bool isPeelFirst(unsigned Level) const { return false; }
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    /// isPeelLast - Returns true if peeling the last iteration from
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    /// this loop will break this dependence.
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0
    virtual bool isPeelLast(unsigned Level) const { return false; }
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    /// isSplitable - Returns true if splitting this loop will break
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    /// the dependence.
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0
    virtual bool isSplitable(unsigned Level) const { return false; }
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    /// isScalar - Returns true if a particular level is scalar; that is,
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    /// if no subscript in the source or destination mention the induction
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    /// variable associated with the loop at this level.
179
    virtual bool isScalar(unsigned Level) const;
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    /// getNextPredecessor - Returns the value of the NextPredecessor
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    /// field.
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0
    const Dependence *getNextPredecessor() const { return NextPredecessor; }
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    /// getNextSuccessor - Returns the value of the NextSuccessor
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    /// field.
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0
    const Dependence *getNextSuccessor() const { return NextSuccessor; }
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    /// setNextPredecessor - Sets the value of the NextPredecessor
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    /// field.
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0
    void setNextPredecessor(const Dependence *pred) { NextPredecessor = pred; }
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    /// setNextSuccessor - Sets the value of the NextSuccessor
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    /// field.
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0
    void setNextSuccessor(const Dependence *succ) { NextSuccessor = succ; }
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    /// dump - For debugging purposes, dumps a dependence to OS.
198
    ///
199
    void dump(raw_ostream &OS) const;
200
201
  private:
202
    Instruction *Src, *Dst;
203
    const Dependence *NextPredecessor, *NextSuccessor;
204
    friend class DependenceInfo;
205
  };
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  /// FullDependence - This class represents a dependence between two memory
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  /// references in a function. It contains detailed information about the
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  /// dependence (direction vectors, etc.) and is used when the compiler is
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  /// able to accurately analyze the interaction of the references; that is,
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  /// it is not a confused dependence (see Dependence). In most cases
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  /// (for output, flow, and anti dependences), the dependence implies an
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  /// ordering, where the source must precede the destination; in contrast,
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  /// input dependences are unordered.
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  class FullDependence final : public Dependence {
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  public:
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    FullDependence(Instruction *Src, Instruction *Dst, bool LoopIndependent,
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                   unsigned Levels);
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220
    /// isLoopIndependent - Returns true if this is a loop-independent
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    /// dependence.
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    bool isLoopIndependent() const override { return LoopIndependent; }
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    /// isConfused - Returns true if this dependence is confused
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    /// (the compiler understands nothing and makes worst-case
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    /// assumptions).
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    bool isConfused() const override { return false; }
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    /// isConsistent - Returns true if this dependence is consistent
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    /// (occurs every time the source and destination are executed).
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    bool isConsistent() const override { return Consistent; }
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    /// getLevels - Returns the number of common loops surrounding the
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    /// source and destination of the dependence.
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1.48k
    unsigned getLevels() const override { return Levels; }
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    /// getDirection - Returns the direction associated with a particular
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    /// level.
239
    unsigned getDirection(unsigned Level) const override;
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241
    /// getDistance - Returns the distance (or NULL) associated with a
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    /// particular level.
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    const SCEV *getDistance(unsigned Level) const override;
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    /// isPeelFirst - Returns true if peeling the first iteration from
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    /// this loop will break this dependence.
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    bool isPeelFirst(unsigned Level) const override;
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    /// isPeelLast - Returns true if peeling the last iteration from
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    /// this loop will break this dependence.
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    bool isPeelLast(unsigned Level) const override;
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    /// isSplitable - Returns true if splitting the loop will break
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    /// the dependence.
255
    bool isSplitable(unsigned Level) const override;
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    /// isScalar - Returns true if a particular level is scalar; that is,
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    /// if no subscript in the source or destination mention the induction
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    /// variable associated with the loop at this level.
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    bool isScalar(unsigned Level) const override;
261
262
  private:
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    unsigned short Levels;
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    bool LoopIndependent;
265
    bool Consistent; // Init to true, then refine.
266
    std::unique_ptr<DVEntry[]> DV;
267
    friend class DependenceInfo;
268
  };
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  /// DependenceInfo - This class is the main dependence-analysis driver.
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  ///
272
  class DependenceInfo {
273
  public:
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    DependenceInfo(Function *F, AliasAnalysis *AA, ScalarEvolution *SE,
275
                   LoopInfo *LI)
276
268
        : AA(AA), SE(SE), LI(LI), F(F) {}
277
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    /// depends - Tests for a dependence between the Src and Dst instructions.
279
    /// Returns NULL if no dependence; otherwise, returns a Dependence (or a
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    /// FullDependence) with as much information as can be gleaned.
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    /// The flag PossiblyLoopIndependent should be set by the caller
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    /// if it appears that control flow can reach from Src to Dst
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    /// without traversing a loop back edge.
284
    std::unique_ptr<Dependence> depends(Instruction *Src,
285
                                        Instruction *Dst,
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                                        bool PossiblyLoopIndependent);
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288
    /// getSplitIteration - Give a dependence that's splittable at some
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    /// particular level, return the iteration that should be used to split
290
    /// the loop.
291
    ///
292
    /// Generally, the dependence analyzer will be used to build
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    /// a dependence graph for a function (basically a map from instructions
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    /// to dependences). Looking for cycles in the graph shows us loops
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    /// that cannot be trivially vectorized/parallelized.
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    ///
297
    /// We can try to improve the situation by examining all the dependences
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    /// that make up the cycle, looking for ones we can break.
299
    /// Sometimes, peeling the first or last iteration of a loop will break
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    /// dependences, and there are flags for those possibilities.
301
    /// Sometimes, splitting a loop at some other iteration will do the trick,
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    /// and we've got a flag for that case. Rather than waste the space to
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    /// record the exact iteration (since we rarely know), we provide
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    /// a method that calculates the iteration. It's a drag that it must work
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    /// from scratch, but wonderful in that it's possible.
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    ///
307
    /// Here's an example:
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    ///
309
    ///    for (i = 0; i < 10; i++)
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    ///        A[i] = ...
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    ///        ... = A[11 - i]
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    ///
313
    /// There's a loop-carried flow dependence from the store to the load,
314
    /// found by the weak-crossing SIV test. The dependence will have a flag,
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    /// indicating that the dependence can be broken by splitting the loop.
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    /// Calling getSplitIteration will return 5.
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    /// Splitting the loop breaks the dependence, like so:
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    ///
319
    ///    for (i = 0; i <= 5; i++)
320
    ///        A[i] = ...
321
    ///        ... = A[11 - i]
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    ///    for (i = 6; i < 10; i++)
323
    ///        A[i] = ...
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    ///        ... = A[11 - i]
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    ///
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    /// breaks the dependence and allows us to vectorize/parallelize
327
    /// both loops.
328
    const SCEV *getSplitIteration(const Dependence &Dep, unsigned Level);
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    Function *getFunction() const { return F; }
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  private:
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    AliasAnalysis *AA;
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    ScalarEvolution *SE;
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    LoopInfo *LI;
336
    Function *F;
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338
    /// Subscript - This private struct represents a pair of subscripts from
339
    /// a pair of potentially multi-dimensional array references. We use a
340
    /// vector of them to guide subscript partitioning.
341
    struct Subscript {
342
      const SCEV *Src;
343
      const SCEV *Dst;
344
      enum ClassificationKind { ZIV, SIV, RDIV, MIV, NonLinear } Classification;
345
      SmallBitVector Loops;
346
      SmallBitVector GroupLoops;
347
      SmallBitVector Group;
348
    };
349
350
    struct CoefficientInfo {
351
      const SCEV *Coeff;
352
      const SCEV *PosPart;
353
      const SCEV *NegPart;
354
      const SCEV *Iterations;
355
    };
356
357
    struct BoundInfo {
358
      const SCEV *Iterations;
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      const SCEV *Upper[8];
360
      const SCEV *Lower[8];
361
      unsigned char Direction;
362
      unsigned char DirSet;
363
    };
364
365
    /// Constraint - This private class represents a constraint, as defined
366
    /// in the paper
367
    ///
368
    ///           Practical Dependence Testing
369
    ///           Goff, Kennedy, Tseng
370
    ///           PLDI 1991
371
    ///
372
    /// There are 5 kinds of constraint, in a hierarchy.
373
    ///   1) Any - indicates no constraint, any dependence is possible.
374
    ///   2) Line - A line ax + by = c, where a, b, and c are parameters,
375
    ///             representing the dependence equation.
376
    ///   3) Distance - The value d of the dependence distance;
377
    ///   4) Point - A point <x, y> representing the dependence from
378
    ///              iteration x to iteration y.
379
    ///   5) Empty - No dependence is possible.
380
    class Constraint {
381
    private:
382
      enum ConstraintKind { Empty, Point, Distance, Line, Any } Kind;
383
      ScalarEvolution *SE;
384
      const SCEV *A;
385
      const SCEV *B;
386
      const SCEV *C;
387
      const Loop *AssociatedLoop;
388
389
    public:
390
      /// isEmpty - Return true if the constraint is of kind Empty.
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4
      bool isEmpty() const { return Kind == Empty; }
392
393
      /// isPoint - Return true if the constraint is of kind Point.
394
1
      bool isPoint() const { return Kind == Point; }
395
396
      /// isDistance - Return true if the constraint is of kind Distance.
397
2
      bool isDistance() const { return Kind == Distance; }
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399
      /// isLine - Return true if the constraint is of kind Line.
400
      /// Since Distance's can also be represented as Lines, we also return
401
      /// true if the constraint is of kind Distance.
402
3
      bool isLine() const { return Kind == Line || 
Kind == Distance1
; }
403
404
      /// isAny - Return true if the constraint is of kind Any;
405
4
      bool isAny() const { return Kind == Any; }
406
407
      /// getX - If constraint is a point <X, Y>, returns X.
408
      /// Otherwise assert.
409
      const SCEV *getX() const;
410
411
      /// getY - If constraint is a point <X, Y>, returns Y.
412
      /// Otherwise assert.
413
      const SCEV *getY() const;
414
415
      /// getA - If constraint is a line AX + BY = C, returns A.
416
      /// Otherwise assert.
417
      const SCEV *getA() const;
418
419
      /// getB - If constraint is a line AX + BY = C, returns B.
420
      /// Otherwise assert.
421
      const SCEV *getB() const;
422
423
      /// getC - If constraint is a line AX + BY = C, returns C.
424
      /// Otherwise assert.
425
      const SCEV *getC() const;
426
427
      /// getD - If constraint is a distance, returns D.
428
      /// Otherwise assert.
429
      const SCEV *getD() const;
430
431
      /// getAssociatedLoop - Returns the loop associated with this constraint.
432
      const Loop *getAssociatedLoop() const;
433
434
      /// setPoint - Change a constraint to Point.
435
      void setPoint(const SCEV *X, const SCEV *Y, const Loop *CurrentLoop);
436
437
      /// setLine - Change a constraint to Line.
438
      void setLine(const SCEV *A, const SCEV *B,
439
                   const SCEV *C, const Loop *CurrentLoop);
440
441
      /// setDistance - Change a constraint to Distance.
442
      void setDistance(const SCEV *D, const Loop *CurrentLoop);
443
444
      /// setEmpty - Change a constraint to Empty.
445
      void setEmpty();
446
447
      /// setAny - Change a constraint to Any.
448
      void setAny(ScalarEvolution *SE);
449
450
      /// dump - For debugging purposes. Dumps the constraint
451
      /// out to OS.
452
      void dump(raw_ostream &OS) const;
453
    };
454
455
    /// establishNestingLevels - Examines the loop nesting of the Src and Dst
456
    /// instructions and establishes their shared loops. Sets the variables
457
    /// CommonLevels, SrcLevels, and MaxLevels.
458
    /// The source and destination instructions needn't be contained in the same
459
    /// loop. The routine establishNestingLevels finds the level of most deeply
460
    /// nested loop that contains them both, CommonLevels. An instruction that's
461
    /// not contained in a loop is at level = 0. MaxLevels is equal to the level
462
    /// of the source plus the level of the destination, minus CommonLevels.
463
    /// This lets us allocate vectors MaxLevels in length, with room for every
464
    /// distinct loop referenced in both the source and destination subscripts.
465
    /// The variable SrcLevels is the nesting depth of the source instruction.
466
    /// It's used to help calculate distinct loops referenced by the destination.
467
    /// Here's the map from loops to levels:
468
    ///            0 - unused
469
    ///            1 - outermost common loop
470
    ///          ... - other common loops
471
    /// CommonLevels - innermost common loop
472
    ///          ... - loops containing Src but not Dst
473
    ///    SrcLevels - innermost loop containing Src but not Dst
474
    ///          ... - loops containing Dst but not Src
475
    ///    MaxLevels - innermost loop containing Dst but not Src
476
    /// Consider the follow code fragment:
477
    ///    for (a = ...) {
478
    ///      for (b = ...) {
479
    ///        for (c = ...) {
480
    ///          for (d = ...) {
481
    ///            A[] = ...;
482
    ///          }
483
    ///        }
484
    ///        for (e = ...) {
485
    ///          for (f = ...) {
486
    ///            for (g = ...) {
487
    ///              ... = A[];
488
    ///            }
489
    ///          }
490
    ///        }
491
    ///      }
492
    ///    }
493
    /// If we're looking at the possibility of a dependence between the store
494
    /// to A (the Src) and the load from A (the Dst), we'll note that they
495
    /// have 2 loops in common, so CommonLevels will equal 2 and the direction
496
    /// vector for Result will have 2 entries. SrcLevels = 4 and MaxLevels = 7.
497
    /// A map from loop names to level indices would look like
498
    ///     a - 1
499
    ///     b - 2 = CommonLevels
500
    ///     c - 3
501
    ///     d - 4 = SrcLevels
502
    ///     e - 5
503
    ///     f - 6
504
    ///     g - 7 = MaxLevels
505
    void establishNestingLevels(const Instruction *Src,
506
                                const Instruction *Dst);
507
508
    unsigned CommonLevels, SrcLevels, MaxLevels;
509
510
    /// mapSrcLoop - Given one of the loops containing the source, return
511
    /// its level index in our numbering scheme.
512
    unsigned mapSrcLoop(const Loop *SrcLoop) const;
513
514
    /// mapDstLoop - Given one of the loops containing the destination,
515
    /// return its level index in our numbering scheme.
516
    unsigned mapDstLoop(const Loop *DstLoop) const;
517
518
    /// isLoopInvariant - Returns true if Expression is loop invariant
519
    /// in LoopNest.
520
    bool isLoopInvariant(const SCEV *Expression, const Loop *LoopNest) const;
521
522
    /// Makes sure all subscript pairs share the same integer type by
523
    /// sign-extending as necessary.
524
    /// Sign-extending a subscript is safe because getelementptr assumes the
525
    /// array subscripts are signed.
526
    void unifySubscriptType(ArrayRef<Subscript *> Pairs);
527
528
    /// removeMatchingExtensions - Examines a subscript pair.
529
    /// If the source and destination are identically sign (or zero)
530
    /// extended, it strips off the extension in an effort to
531
    /// simplify the actual analysis.
532
    void removeMatchingExtensions(Subscript *Pair);
533
534
    /// collectCommonLoops - Finds the set of loops from the LoopNest that
535
    /// have a level <= CommonLevels and are referred to by the SCEV Expression.
536
    void collectCommonLoops(const SCEV *Expression,
537
                            const Loop *LoopNest,
538
                            SmallBitVector &Loops) const;
539
540
    /// checkSrcSubscript - Examines the SCEV Src, returning true iff it's
541
    /// linear. Collect the set of loops mentioned by Src.
542
    bool checkSrcSubscript(const SCEV *Src,
543
                           const Loop *LoopNest,
544
                           SmallBitVector &Loops);
545
546
    /// checkDstSubscript - Examines the SCEV Dst, returning true iff it's
547
    /// linear. Collect the set of loops mentioned by Dst.
548
    bool checkDstSubscript(const SCEV *Dst,
549
                           const Loop *LoopNest,
550
                           SmallBitVector &Loops);
551
552
    /// isKnownPredicate - Compare X and Y using the predicate Pred.
553
    /// Basically a wrapper for SCEV::isKnownPredicate,
554
    /// but tries harder, especially in the presence of sign and zero
555
    /// extensions and symbolics.
556
    bool isKnownPredicate(ICmpInst::Predicate Pred,
557
                          const SCEV *X,
558
                          const SCEV *Y) const;
559
560
    /// isKnownLessThan - Compare to see if S is less than Size
561
    /// Another wrapper for isKnownNegative(S - max(Size, 1)) with some extra
562
    /// checking if S is an AddRec and we can prove lessthan using the loop
563
    /// bounds.
564
    bool isKnownLessThan(const SCEV *S, const SCEV *Size) const;
565
566
    /// isKnownNonNegative - Compare to see if S is known not to be negative
567
    /// Uses the fact that S comes from Ptr, which may be an inbound GEP,
568
    /// Proving there is no wrapping going on.
569
    bool isKnownNonNegative(const SCEV *S, const Value *Ptr) const;
570
571
    /// collectUpperBound - All subscripts are the same type (on my machine,
572
    /// an i64). The loop bound may be a smaller type. collectUpperBound
573
    /// find the bound, if available, and zero extends it to the Type T.
574
    /// (I zero extend since the bound should always be >= 0.)
575
    /// If no upper bound is available, return NULL.
576
    const SCEV *collectUpperBound(const Loop *l, Type *T) const;
577
578
    /// collectConstantUpperBound - Calls collectUpperBound(), then
579
    /// attempts to cast it to SCEVConstant. If the cast fails,
580
    /// returns NULL.
581
    const SCEVConstant *collectConstantUpperBound(const Loop *l, Type *T) const;
582
583
    /// classifyPair - Examines the subscript pair (the Src and Dst SCEVs)
584
    /// and classifies it as either ZIV, SIV, RDIV, MIV, or Nonlinear.
585
    /// Collects the associated loops in a set.
586
    Subscript::ClassificationKind classifyPair(const SCEV *Src,
587
                                           const Loop *SrcLoopNest,
588
                                           const SCEV *Dst,
589
                                           const Loop *DstLoopNest,
590
                                           SmallBitVector &Loops);
591
592
    /// testZIV - Tests the ZIV subscript pair (Src and Dst) for dependence.
593
    /// Returns true if any possible dependence is disproved.
594
    /// If there might be a dependence, returns false.
595
    /// If the dependence isn't proven to exist,
596
    /// marks the Result as inconsistent.
597
    bool testZIV(const SCEV *Src,
598
                 const SCEV *Dst,
599
                 FullDependence &Result) const;
600
601
    /// testSIV - Tests the SIV subscript pair (Src and Dst) for dependence.
602
    /// Things of the form [c1 + a1*i] and [c2 + a2*j], where
603
    /// i and j are induction variables, c1 and c2 are loop invariant,
604
    /// and a1 and a2 are constant.
605
    /// Returns true if any possible dependence is disproved.
606
    /// If there might be a dependence, returns false.
607
    /// Sets appropriate direction vector entry and, when possible,
608
    /// the distance vector entry.
609
    /// If the dependence isn't proven to exist,
610
    /// marks the Result as inconsistent.
611
    bool testSIV(const SCEV *Src,
612
                 const SCEV *Dst,
613
                 unsigned &Level,
614
                 FullDependence &Result,
615
                 Constraint &NewConstraint,
616
                 const SCEV *&SplitIter) const;
617
618
    /// testRDIV - Tests the RDIV subscript pair (Src and Dst) for dependence.
619
    /// Things of the form [c1 + a1*i] and [c2 + a2*j]
620
    /// where i and j are induction variables, c1 and c2 are loop invariant,
621
    /// and a1 and a2 are constant.
622
    /// With minor algebra, this test can also be used for things like
623
    /// [c1 + a1*i + a2*j][c2].
624
    /// Returns true if any possible dependence is disproved.
625
    /// If there might be a dependence, returns false.
626
    /// Marks the Result as inconsistent.
627
    bool testRDIV(const SCEV *Src,
628
                  const SCEV *Dst,
629
                  FullDependence &Result) const;
630
631
    /// testMIV - Tests the MIV subscript pair (Src and Dst) for dependence.
632
    /// Returns true if dependence disproved.
633
    /// Can sometimes refine direction vectors.
634
    bool testMIV(const SCEV *Src,
635
                 const SCEV *Dst,
636
                 const SmallBitVector &Loops,
637
                 FullDependence &Result) const;
638
639
    /// strongSIVtest - Tests the strong SIV subscript pair (Src and Dst)
640
    /// for dependence.
641
    /// Things of the form [c1 + a*i] and [c2 + a*i],
642
    /// where i is an induction variable, c1 and c2 are loop invariant,
643
    /// and a is a constant
644
    /// Returns true if any possible dependence is disproved.
645
    /// If there might be a dependence, returns false.
646
    /// Sets appropriate direction and distance.
647
    bool strongSIVtest(const SCEV *Coeff,
648
                       const SCEV *SrcConst,
649
                       const SCEV *DstConst,
650
                       const Loop *CurrentLoop,
651
                       unsigned Level,
652
                       FullDependence &Result,
653
                       Constraint &NewConstraint) const;
654
655
    /// weakCrossingSIVtest - Tests the weak-crossing SIV subscript pair
656
    /// (Src and Dst) for dependence.
657
    /// Things of the form [c1 + a*i] and [c2 - a*i],
658
    /// where i is an induction variable, c1 and c2 are loop invariant,
659
    /// and a is a constant.
660
    /// Returns true if any possible dependence is disproved.
661
    /// If there might be a dependence, returns false.
662
    /// Sets appropriate direction entry.
663
    /// Set consistent to false.
664
    /// Marks the dependence as splitable.
665
    bool weakCrossingSIVtest(const SCEV *SrcCoeff,
666
                             const SCEV *SrcConst,
667
                             const SCEV *DstConst,
668
                             const Loop *CurrentLoop,
669
                             unsigned Level,
670
                             FullDependence &Result,
671
                             Constraint &NewConstraint,
672
                             const SCEV *&SplitIter) const;
673
674
    /// ExactSIVtest - Tests the SIV subscript pair
675
    /// (Src and Dst) for dependence.
676
    /// Things of the form [c1 + a1*i] and [c2 + a2*i],
677
    /// where i is an induction variable, c1 and c2 are loop invariant,
678
    /// and a1 and a2 are constant.
679
    /// Returns true if any possible dependence is disproved.
680
    /// If there might be a dependence, returns false.
681
    /// Sets appropriate direction entry.
682
    /// Set consistent to false.
683
    bool exactSIVtest(const SCEV *SrcCoeff,
684
                      const SCEV *DstCoeff,
685
                      const SCEV *SrcConst,
686
                      const SCEV *DstConst,
687
                      const Loop *CurrentLoop,
688
                      unsigned Level,
689
                      FullDependence &Result,
690
                      Constraint &NewConstraint) const;
691
692
    /// weakZeroSrcSIVtest - Tests the weak-zero SIV subscript pair
693
    /// (Src and Dst) for dependence.
694
    /// Things of the form [c1] and [c2 + a*i],
695
    /// where i is an induction variable, c1 and c2 are loop invariant,
696
    /// and a is a constant. See also weakZeroDstSIVtest.
697
    /// Returns true if any possible dependence is disproved.
698
    /// If there might be a dependence, returns false.
699
    /// Sets appropriate direction entry.
700
    /// Set consistent to false.
701
    /// If loop peeling will break the dependence, mark appropriately.
702
    bool weakZeroSrcSIVtest(const SCEV *DstCoeff,
703
                            const SCEV *SrcConst,
704
                            const SCEV *DstConst,
705
                            const Loop *CurrentLoop,
706
                            unsigned Level,
707
                            FullDependence &Result,
708
                            Constraint &NewConstraint) const;
709
710
    /// weakZeroDstSIVtest - Tests the weak-zero SIV subscript pair
711
    /// (Src and Dst) for dependence.
712
    /// Things of the form [c1 + a*i] and [c2],
713
    /// where i is an induction variable, c1 and c2 are loop invariant,
714
    /// and a is a constant. See also weakZeroSrcSIVtest.
715
    /// Returns true if any possible dependence is disproved.
716
    /// If there might be a dependence, returns false.
717
    /// Sets appropriate direction entry.
718
    /// Set consistent to false.
719
    /// If loop peeling will break the dependence, mark appropriately.
720
    bool weakZeroDstSIVtest(const SCEV *SrcCoeff,
721
                            const SCEV *SrcConst,
722
                            const SCEV *DstConst,
723
                            const Loop *CurrentLoop,
724
                            unsigned Level,
725
                            FullDependence &Result,
726
                            Constraint &NewConstraint) const;
727
728
    /// exactRDIVtest - Tests the RDIV subscript pair for dependence.
729
    /// Things of the form [c1 + a*i] and [c2 + b*j],
730
    /// where i and j are induction variable, c1 and c2 are loop invariant,
731
    /// and a and b are constants.
732
    /// Returns true if any possible dependence is disproved.
733
    /// Marks the result as inconsistent.
734
    /// Works in some cases that symbolicRDIVtest doesn't,
735
    /// and vice versa.
736
    bool exactRDIVtest(const SCEV *SrcCoeff,
737
                       const SCEV *DstCoeff,
738
                       const SCEV *SrcConst,
739
                       const SCEV *DstConst,
740
                       const Loop *SrcLoop,
741
                       const Loop *DstLoop,
742
                       FullDependence &Result) const;
743
744
    /// symbolicRDIVtest - Tests the RDIV subscript pair for dependence.
745
    /// Things of the form [c1 + a*i] and [c2 + b*j],
746
    /// where i and j are induction variable, c1 and c2 are loop invariant,
747
    /// and a and b are constants.
748
    /// Returns true if any possible dependence is disproved.
749
    /// Marks the result as inconsistent.
750
    /// Works in some cases that exactRDIVtest doesn't,
751
    /// and vice versa. Can also be used as a backup for
752
    /// ordinary SIV tests.
753
    bool symbolicRDIVtest(const SCEV *SrcCoeff,
754
                          const SCEV *DstCoeff,
755
                          const SCEV *SrcConst,
756
                          const SCEV *DstConst,
757
                          const Loop *SrcLoop,
758
                          const Loop *DstLoop) const;
759
760
    /// gcdMIVtest - Tests an MIV subscript pair for dependence.
761
    /// Returns true if any possible dependence is disproved.
762
    /// Marks the result as inconsistent.
763
    /// Can sometimes disprove the equal direction for 1 or more loops.
764
    //  Can handle some symbolics that even the SIV tests don't get,
765
    /// so we use it as a backup for everything.
766
    bool gcdMIVtest(const SCEV *Src,
767
                    const SCEV *Dst,
768
                    FullDependence &Result) const;
769
770
    /// banerjeeMIVtest - Tests an MIV subscript pair for dependence.
771
    /// Returns true if any possible dependence is disproved.
772
    /// Marks the result as inconsistent.
773
    /// Computes directions.
774
    bool banerjeeMIVtest(const SCEV *Src,
775
                         const SCEV *Dst,
776
                         const SmallBitVector &Loops,
777
                         FullDependence &Result) const;
778
779
    /// collectCoefficientInfo - Walks through the subscript,
780
    /// collecting each coefficient, the associated loop bounds,
781
    /// and recording its positive and negative parts for later use.
782
    CoefficientInfo *collectCoeffInfo(const SCEV *Subscript,
783
                                      bool SrcFlag,
784
                                      const SCEV *&Constant) const;
785
786
    /// getPositivePart - X^+ = max(X, 0).
787
    ///
788
    const SCEV *getPositivePart(const SCEV *X) const;
789
790
    /// getNegativePart - X^- = min(X, 0).
791
    ///
792
    const SCEV *getNegativePart(const SCEV *X) const;
793
794
    /// getLowerBound - Looks through all the bounds info and
795
    /// computes the lower bound given the current direction settings
796
    /// at each level.
797
    const SCEV *getLowerBound(BoundInfo *Bound) const;
798
799
    /// getUpperBound - Looks through all the bounds info and
800
    /// computes the upper bound given the current direction settings
801
    /// at each level.
802
    const SCEV *getUpperBound(BoundInfo *Bound) const;
803
804
    /// exploreDirections - Hierarchically expands the direction vector
805
    /// search space, combining the directions of discovered dependences
806
    /// in the DirSet field of Bound. Returns the number of distinct
807
    /// dependences discovered. If the dependence is disproved,
808
    /// it will return 0.
809
    unsigned exploreDirections(unsigned Level,
810
                               CoefficientInfo *A,
811
                               CoefficientInfo *B,
812
                               BoundInfo *Bound,
813
                               const SmallBitVector &Loops,
814
                               unsigned &DepthExpanded,
815
                               const SCEV *Delta) const;
816
817
    /// testBounds - Returns true iff the current bounds are plausible.
818
    bool testBounds(unsigned char DirKind,
819
                    unsigned Level,
820
                    BoundInfo *Bound,
821
                    const SCEV *Delta) const;
822
823
    /// findBoundsALL - Computes the upper and lower bounds for level K
824
    /// using the * direction. Records them in Bound.
825
    void findBoundsALL(CoefficientInfo *A,
826
                       CoefficientInfo *B,
827
                       BoundInfo *Bound,
828
                       unsigned K) const;
829
830
    /// findBoundsLT - Computes the upper and lower bounds for level K
831
    /// using the < direction. Records them in Bound.
832
    void findBoundsLT(CoefficientInfo *A,
833
                      CoefficientInfo *B,
834
                      BoundInfo *Bound,
835
                      unsigned K) const;
836
837
    /// findBoundsGT - Computes the upper and lower bounds for level K
838
    /// using the > direction. Records them in Bound.
839
    void findBoundsGT(CoefficientInfo *A,
840
                      CoefficientInfo *B,
841
                      BoundInfo *Bound,
842
                      unsigned K) const;
843
844
    /// findBoundsEQ - Computes the upper and lower bounds for level K
845
    /// using the = direction. Records them in Bound.
846
    void findBoundsEQ(CoefficientInfo *A,
847
                      CoefficientInfo *B,
848
                      BoundInfo *Bound,
849
                      unsigned K) const;
850
851
    /// intersectConstraints - Updates X with the intersection
852
    /// of the Constraints X and Y. Returns true if X has changed.
853
    bool intersectConstraints(Constraint *X,
854
                              const Constraint *Y);
855
856
    /// propagate - Review the constraints, looking for opportunities
857
    /// to simplify a subscript pair (Src and Dst).
858
    /// Return true if some simplification occurs.
859
    /// If the simplification isn't exact (that is, if it is conservative
860
    /// in terms of dependence), set consistent to false.
861
    bool propagate(const SCEV *&Src,
862
                   const SCEV *&Dst,
863
                   SmallBitVector &Loops,
864
                   SmallVectorImpl<Constraint> &Constraints,
865
                   bool &Consistent);
866
867
    /// propagateDistance - Attempt to propagate a distance
868
    /// constraint into a subscript pair (Src and Dst).
869
    /// Return true if some simplification occurs.
870
    /// If the simplification isn't exact (that is, if it is conservative
871
    /// in terms of dependence), set consistent to false.
872
    bool propagateDistance(const SCEV *&Src,
873
                           const SCEV *&Dst,
874
                           Constraint &CurConstraint,
875
                           bool &Consistent);
876
877
    /// propagatePoint - Attempt to propagate a point
878
    /// constraint into a subscript pair (Src and Dst).
879
    /// Return true if some simplification occurs.
880
    bool propagatePoint(const SCEV *&Src,
881
                        const SCEV *&Dst,
882
                        Constraint &CurConstraint);
883
884
    /// propagateLine - Attempt to propagate a line
885
    /// constraint into a subscript pair (Src and Dst).
886
    /// Return true if some simplification occurs.
887
    /// If the simplification isn't exact (that is, if it is conservative
888
    /// in terms of dependence), set consistent to false.
889
    bool propagateLine(const SCEV *&Src,
890
                       const SCEV *&Dst,
891
                       Constraint &CurConstraint,
892
                       bool &Consistent);
893
894
    /// findCoefficient - Given a linear SCEV,
895
    /// return the coefficient corresponding to specified loop.
896
    /// If there isn't one, return the SCEV constant 0.
897
    /// For example, given a*i + b*j + c*k, returning the coefficient
898
    /// corresponding to the j loop would yield b.
899
    const SCEV *findCoefficient(const SCEV *Expr,
900
                                const Loop *TargetLoop) const;
901
902
    /// zeroCoefficient - Given a linear SCEV,
903
    /// return the SCEV given by zeroing out the coefficient
904
    /// corresponding to the specified loop.
905
    /// For example, given a*i + b*j + c*k, zeroing the coefficient
906
    /// corresponding to the j loop would yield a*i + c*k.
907
    const SCEV *zeroCoefficient(const SCEV *Expr,
908
                                const Loop *TargetLoop) const;
909
910
    /// addToCoefficient - Given a linear SCEV Expr,
911
    /// return the SCEV given by adding some Value to the
912
    /// coefficient corresponding to the specified TargetLoop.
913
    /// For example, given a*i + b*j + c*k, adding 1 to the coefficient
914
    /// corresponding to the j loop would yield a*i + (b+1)*j + c*k.
915
    const SCEV *addToCoefficient(const SCEV *Expr,
916
                                 const Loop *TargetLoop,
917
                                 const SCEV *Value)  const;
918
919
    /// updateDirection - Update direction vector entry
920
    /// based on the current constraint.
921
    void updateDirection(Dependence::DVEntry &Level,
922
                         const Constraint &CurConstraint) const;
923
924
    bool tryDelinearize(Instruction *Src, Instruction *Dst,
925
                        SmallVectorImpl<Subscript> &Pair);
926
  }; // class DependenceInfo
927
928
  /// AnalysisPass to compute dependence information in a function
929
  class DependenceAnalysis : public AnalysisInfoMixin<DependenceAnalysis> {
930
  public:
931
    typedef DependenceInfo Result;
932
    Result run(Function &F, FunctionAnalysisManager &FAM);
933
934
  private:
935
    static AnalysisKey Key;
936
    friend struct AnalysisInfoMixin<DependenceAnalysis>;
937
  }; // class DependenceAnalysis
938
939
  /// Legacy pass manager pass to access dependence information
940
  class DependenceAnalysisWrapperPass : public FunctionPass {
941
  public:
942
    static char ID; // Class identification, replacement for typeinfo
943
42
    DependenceAnalysisWrapperPass() : FunctionPass(ID) {
944
42
      initializeDependenceAnalysisWrapperPassPass(
945
42
          *PassRegistry::getPassRegistry());
946
42
    }
947
948
    bool runOnFunction(Function &F) override;
949
    void releaseMemory() override;
950
    void getAnalysisUsage(AnalysisUsage &) const override;
951
    void print(raw_ostream &, const Module * = nullptr) const override;
952
    DependenceInfo &getDI() const;
953
954
  private:
955
    std::unique_ptr<DependenceInfo> info;
956
  }; // class DependenceAnalysisWrapperPass
957
958
  /// createDependenceAnalysisPass - This creates an instance of the
959
  /// DependenceAnalysis wrapper pass.
960
  FunctionPass *createDependenceAnalysisWrapperPass();
961
962
} // namespace llvm
963
964
#endif