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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176519 91177308-0d34-0410-b5e6-96231b3b80d8
896 lines
37 KiB
C++
896 lines
37 KiB
C++
//===-- 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/IR/Instructions.h"
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#include "llvm/Pass.h"
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namespace llvm {
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class AliasAnalysis;
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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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class Dependence {
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public:
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Dependence(Instruction *Source,
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Instruction *Destination) :
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Src(Source), Dst(Destination) {}
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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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PeelLast(false), Splitable(false), Distance(NULL) { }
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};
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/// getSrc - Returns the source instruction for this dependence.
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///
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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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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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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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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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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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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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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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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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virtual const SCEV *getDistance(unsigned Level) const { return NULL; }
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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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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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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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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.
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virtual bool isScalar(unsigned Level) const;
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/// dump - For debugging purposes, dumps a dependence to OS.
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///
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void dump(raw_ostream &OS) const;
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private:
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Instruction *Src, *Dst;
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friend class DependenceAnalysis;
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};
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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 : public Dependence {
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public:
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FullDependence(Instruction *Src,
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Instruction *Dst,
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bool LoopIndependent,
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unsigned Levels);
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~FullDependence() {
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delete[] DV;
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}
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/// isLoopIndependent - Returns true if this is a loop-independent
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/// dependence.
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bool isLoopIndependent() const { 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 { 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 { 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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unsigned getLevels() const { return Levels; }
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/// getDirection - Returns the direction associated with a particular
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/// level.
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unsigned getDirection(unsigned Level) const;
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/// 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;
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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;
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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;
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/// isSplitable - Returns true if splitting the loop will break
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/// the dependence.
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bool isSplitable(unsigned Level) const;
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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;
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private:
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unsigned short Levels;
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bool LoopIndependent;
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bool Consistent; // Init to true, then refine.
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DVEntry *DV;
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friend class DependenceAnalysis;
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};
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/// DependenceAnalysis - This class is the main dependence-analysis driver.
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///
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class DependenceAnalysis : public FunctionPass {
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void operator=(const DependenceAnalysis &) LLVM_DELETED_FUNCTION;
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DependenceAnalysis(const DependenceAnalysis &) LLVM_DELETED_FUNCTION;
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public:
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/// depends - Tests for a dependence between the Src and Dst instructions.
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/// 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.
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Dependence *depends(Instruction *Src,
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Instruction *Dst,
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bool PossiblyLoopIndependent);
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/// getSplitIteration - Give a dependence that's splittable at some
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/// particular level, return the iteration that should be used to split
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/// the loop.
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///
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/// 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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///
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/// 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.
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/// Sometimes, peeling the first or last iteration of a loop will break
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/// dependences, and there are flags for those possibilities.
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/// 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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///
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/// Here's an example:
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///
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/// for (i = 0; i < 10; i++)
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/// A[i] = ...
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/// ... = A[11 - i]
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///
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/// There's a loop-carried flow dependence from the store to the load,
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/// 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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///
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/// for (i = 0; i <= 5; i++)
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/// A[i] = ...
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/// ... = A[11 - i]
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/// for (i = 6; i < 10; i++)
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/// 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
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/// both loops.
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const SCEV *getSplitIteration(const Dependence *Dep, unsigned Level);
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private:
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AliasAnalysis *AA;
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ScalarEvolution *SE;
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LoopInfo *LI;
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Function *F;
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/// Subscript - This private struct represents a pair of subscripts from
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/// a pair of potentially multi-dimensional array references. We use a
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/// vector of them to guide subscript partitioning.
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struct Subscript {
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const SCEV *Src;
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const SCEV *Dst;
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enum ClassificationKind { ZIV, SIV, RDIV, MIV, NonLinear } Classification;
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SmallBitVector Loops;
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SmallBitVector GroupLoops;
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SmallBitVector Group;
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};
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struct CoefficientInfo {
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const SCEV *Coeff;
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const SCEV *PosPart;
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const SCEV *NegPart;
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const SCEV *Iterations;
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};
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struct BoundInfo {
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const SCEV *Iterations;
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const SCEV *Upper[8];
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const SCEV *Lower[8];
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unsigned char Direction;
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unsigned char DirSet;
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};
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/// Constraint - This private class represents a constraint, as defined
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/// in the paper
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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 are 5 kinds of constraint, in a hierarchy.
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/// 1) Any - indicates no constraint, any dependence is possible.
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/// 2) Line - A line ax + by = c, where a, b, and c are parameters,
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/// representing the dependence equation.
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/// 3) Distance - The value d of the dependence distance;
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/// 4) Point - A point <x, y> representing the dependence from
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/// iteration x to iteration y.
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/// 5) Empty - No dependence is possible.
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class Constraint {
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private:
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enum ConstraintKind { Empty, Point, Distance, Line, Any } Kind;
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ScalarEvolution *SE;
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const SCEV *A;
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const SCEV *B;
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const SCEV *C;
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const Loop *AssociatedLoop;
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public:
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/// isEmpty - Return true if the constraint is of kind Empty.
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bool isEmpty() const { return Kind == Empty; }
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/// isPoint - Return true if the constraint is of kind Point.
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bool isPoint() const { return Kind == Point; }
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/// isDistance - Return true if the constraint is of kind Distance.
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bool isDistance() const { return Kind == Distance; }
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/// isLine - Return true if the constraint is of kind Line.
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/// Since Distance's can also be represented as Lines, we also return
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/// true if the constraint is of kind Distance.
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bool isLine() const { return Kind == Line || Kind == Distance; }
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/// isAny - Return true if the constraint is of kind Any;
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bool isAny() const { return Kind == Any; }
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/// getX - If constraint is a point <X, Y>, returns X.
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/// Otherwise assert.
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const SCEV *getX() const;
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/// getY - If constraint is a point <X, Y>, returns Y.
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/// Otherwise assert.
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const SCEV *getY() const;
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/// getA - If constraint is a line AX + BY = C, returns A.
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/// Otherwise assert.
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const SCEV *getA() const;
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/// getB - If constraint is a line AX + BY = C, returns B.
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/// Otherwise assert.
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const SCEV *getB() const;
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/// getC - If constraint is a line AX + BY = C, returns C.
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/// Otherwise assert.
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const SCEV *getC() const;
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/// getD - If constraint is a distance, returns D.
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/// Otherwise assert.
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const SCEV *getD() const;
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/// getAssociatedLoop - Returns the loop associated with this constraint.
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const Loop *getAssociatedLoop() const;
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/// setPoint - Change a constraint to Point.
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void setPoint(const SCEV *X, const SCEV *Y, const Loop *CurrentLoop);
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/// setLine - Change a constraint to Line.
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void setLine(const SCEV *A, const SCEV *B,
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const SCEV *C, const Loop *CurrentLoop);
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/// setDistance - Change a constraint to Distance.
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void setDistance(const SCEV *D, const Loop *CurrentLoop);
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/// setEmpty - Change a constraint to Empty.
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void setEmpty();
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/// setAny - Change a constraint to Any.
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void setAny(ScalarEvolution *SE);
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/// dump - For debugging purposes. Dumps the constraint
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/// out to OS.
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void dump(raw_ostream &OS) const;
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};
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/// establishNestingLevels - Examines the loop nesting of the Src and Dst
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/// instructions and establishes their shared loops. Sets the variables
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/// CommonLevels, SrcLevels, and MaxLevels.
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/// The source and destination instructions needn't be contained in the same
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/// loop. The routine establishNestingLevels finds the level of most deeply
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/// nested loop that contains them both, CommonLevels. An instruction that's
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/// not contained in a loop is at level = 0. MaxLevels is equal to the level
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/// of the source plus the level of the destination, minus CommonLevels.
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/// This lets us allocate vectors MaxLevels in length, with room for every
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/// distinct loop referenced in both the source and destination subscripts.
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/// The variable SrcLevels is the nesting depth of the source instruction.
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/// It's used to help calculate distinct loops referenced by the destination.
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/// Here's the map from loops to levels:
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/// 0 - unused
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/// 1 - outermost common loop
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/// ... - other common loops
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/// CommonLevels - innermost common loop
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/// ... - loops containing Src but not Dst
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/// SrcLevels - innermost loop containing Src but not Dst
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/// ... - loops containing Dst but not Src
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/// MaxLevels - innermost loop containing Dst but not Src
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/// Consider the follow code fragment:
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/// for (a = ...) {
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/// for (b = ...) {
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/// for (c = ...) {
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/// for (d = ...) {
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/// A[] = ...;
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/// }
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/// }
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/// for (e = ...) {
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/// for (f = ...) {
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/// for (g = ...) {
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/// ... = A[];
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/// }
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/// }
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/// }
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/// }
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/// }
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/// If we're looking at the possibility of a dependence between the store
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/// to A (the Src) and the load from A (the Dst), we'll note that they
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/// have 2 loops in common, so CommonLevels will equal 2 and the direction
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/// vector for Result will have 2 entries. SrcLevels = 4 and MaxLevels = 7.
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/// A map from loop names to level indices would look like
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/// a - 1
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/// b - 2 = CommonLevels
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/// c - 3
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/// d - 4 = SrcLevels
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/// e - 5
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/// f - 6
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/// g - 7 = MaxLevels
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void establishNestingLevels(const Instruction *Src,
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const Instruction *Dst);
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unsigned CommonLevels, SrcLevels, MaxLevels;
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/// mapSrcLoop - Given one of the loops containing the source, return
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/// its level index in our numbering scheme.
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unsigned mapSrcLoop(const Loop *SrcLoop) const;
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/// mapDstLoop - Given one of the loops containing the destination,
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/// return its level index in our numbering scheme.
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unsigned mapDstLoop(const Loop *DstLoop) const;
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/// isLoopInvariant - Returns true if Expression is loop invariant
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/// in LoopNest.
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bool isLoopInvariant(const SCEV *Expression, const Loop *LoopNest) const;
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/// removeMatchingExtensions - Examines a subscript pair.
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/// If the source and destination are identically sign (or zero)
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/// extended, it strips off the extension in an effort to
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/// simplify the actual analysis.
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void removeMatchingExtensions(Subscript *Pair);
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/// collectCommonLoops - Finds the set of loops from the LoopNest that
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/// have a level <= CommonLevels and are referred to by the SCEV Expression.
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void collectCommonLoops(const SCEV *Expression,
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const Loop *LoopNest,
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SmallBitVector &Loops) const;
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/// checkSrcSubscript - Examines the SCEV Src, returning true iff it's
|
|
/// linear. Collect the set of loops mentioned by Src.
|
|
bool checkSrcSubscript(const SCEV *Src,
|
|
const Loop *LoopNest,
|
|
SmallBitVector &Loops);
|
|
|
|
/// checkDstSubscript - Examines the SCEV Dst, returning true iff it's
|
|
/// linear. Collect the set of loops mentioned by Dst.
|
|
bool checkDstSubscript(const SCEV *Dst,
|
|
const Loop *LoopNest,
|
|
SmallBitVector &Loops);
|
|
|
|
/// isKnownPredicate - Compare X and Y using the predicate Pred.
|
|
/// Basically a wrapper for SCEV::isKnownPredicate,
|
|
/// but tries harder, especially in the presence of sign and zero
|
|
/// extensions and symbolics.
|
|
bool isKnownPredicate(ICmpInst::Predicate Pred,
|
|
const SCEV *X,
|
|
const SCEV *Y) const;
|
|
|
|
/// collectUpperBound - All subscripts are the same type (on my machine,
|
|
/// an i64). The loop bound may be a smaller type. collectUpperBound
|
|
/// find the bound, if available, and zero extends it to the Type T.
|
|
/// (I zero extend since the bound should always be >= 0.)
|
|
/// If no upper bound is available, return NULL.
|
|
const SCEV *collectUpperBound(const Loop *l, Type *T) const;
|
|
|
|
/// collectConstantUpperBound - Calls collectUpperBound(), then
|
|
/// attempts to cast it to SCEVConstant. If the cast fails,
|
|
/// returns NULL.
|
|
const SCEVConstant *collectConstantUpperBound(const Loop *l, Type *T) const;
|
|
|
|
/// classifyPair - Examines the subscript pair (the Src and Dst SCEVs)
|
|
/// and classifies it as either ZIV, SIV, RDIV, MIV, or Nonlinear.
|
|
/// Collects the associated loops in a set.
|
|
Subscript::ClassificationKind classifyPair(const SCEV *Src,
|
|
const Loop *SrcLoopNest,
|
|
const SCEV *Dst,
|
|
const Loop *DstLoopNest,
|
|
SmallBitVector &Loops);
|
|
|
|
/// testZIV - Tests the ZIV subscript pair (Src and Dst) for dependence.
|
|
/// Returns true if any possible dependence is disproved.
|
|
/// If there might be a dependence, returns false.
|
|
/// If the dependence isn't proven to exist,
|
|
/// marks the Result as inconsistent.
|
|
bool testZIV(const SCEV *Src,
|
|
const SCEV *Dst,
|
|
FullDependence &Result) const;
|
|
|
|
/// testSIV - Tests the SIV subscript pair (Src and Dst) for dependence.
|
|
/// Things of the form [c1 + a1*i] and [c2 + a2*j], where
|
|
/// i and j are induction variables, c1 and c2 are loop invariant,
|
|
/// and a1 and a2 are constant.
|
|
/// Returns true if any possible dependence is disproved.
|
|
/// If there might be a dependence, returns false.
|
|
/// Sets appropriate direction vector entry and, when possible,
|
|
/// the distance vector entry.
|
|
/// If the dependence isn't proven to exist,
|
|
/// marks the Result as inconsistent.
|
|
bool testSIV(const SCEV *Src,
|
|
const SCEV *Dst,
|
|
unsigned &Level,
|
|
FullDependence &Result,
|
|
Constraint &NewConstraint,
|
|
const SCEV *&SplitIter) const;
|
|
|
|
/// testRDIV - Tests the RDIV subscript pair (Src and Dst) for dependence.
|
|
/// Things of the form [c1 + a1*i] and [c2 + a2*j]
|
|
/// where i and j are induction variables, c1 and c2 are loop invariant,
|
|
/// and a1 and a2 are constant.
|
|
/// With minor algebra, this test can also be used for things like
|
|
/// [c1 + a1*i + a2*j][c2].
|
|
/// Returns true if any possible dependence is disproved.
|
|
/// If there might be a dependence, returns false.
|
|
/// Marks the Result as inconsistent.
|
|
bool testRDIV(const SCEV *Src,
|
|
const SCEV *Dst,
|
|
FullDependence &Result) const;
|
|
|
|
/// testMIV - Tests the MIV subscript pair (Src and Dst) for dependence.
|
|
/// Returns true if dependence disproved.
|
|
/// Can sometimes refine direction vectors.
|
|
bool testMIV(const SCEV *Src,
|
|
const SCEV *Dst,
|
|
const SmallBitVector &Loops,
|
|
FullDependence &Result) const;
|
|
|
|
/// strongSIVtest - Tests the strong SIV subscript pair (Src and Dst)
|
|
/// for dependence.
|
|
/// Things of the form [c1 + a*i] and [c2 + a*i],
|
|
/// where i is an induction variable, c1 and c2 are loop invariant,
|
|
/// and a is a constant
|
|
/// Returns true if any possible dependence is disproved.
|
|
/// If there might be a dependence, returns false.
|
|
/// Sets appropriate direction and distance.
|
|
bool strongSIVtest(const SCEV *Coeff,
|
|
const SCEV *SrcConst,
|
|
const SCEV *DstConst,
|
|
const Loop *CurrentLoop,
|
|
unsigned Level,
|
|
FullDependence &Result,
|
|
Constraint &NewConstraint) const;
|
|
|
|
/// weakCrossingSIVtest - Tests the weak-crossing SIV subscript pair
|
|
/// (Src and Dst) for dependence.
|
|
/// Things of the form [c1 + a*i] and [c2 - a*i],
|
|
/// where i is an induction variable, c1 and c2 are loop invariant,
|
|
/// and a is a constant.
|
|
/// Returns true if any possible dependence is disproved.
|
|
/// If there might be a dependence, returns false.
|
|
/// Sets appropriate direction entry.
|
|
/// Set consistent to false.
|
|
/// Marks the dependence as splitable.
|
|
bool weakCrossingSIVtest(const SCEV *SrcCoeff,
|
|
const SCEV *SrcConst,
|
|
const SCEV *DstConst,
|
|
const Loop *CurrentLoop,
|
|
unsigned Level,
|
|
FullDependence &Result,
|
|
Constraint &NewConstraint,
|
|
const SCEV *&SplitIter) const;
|
|
|
|
/// ExactSIVtest - Tests the SIV subscript pair
|
|
/// (Src and Dst) for dependence.
|
|
/// Things of the form [c1 + a1*i] and [c2 + a2*i],
|
|
/// where i is an induction variable, c1 and c2 are loop invariant,
|
|
/// and a1 and a2 are constant.
|
|
/// Returns true if any possible dependence is disproved.
|
|
/// If there might be a dependence, returns false.
|
|
/// Sets appropriate direction entry.
|
|
/// Set consistent to false.
|
|
bool exactSIVtest(const SCEV *SrcCoeff,
|
|
const SCEV *DstCoeff,
|
|
const SCEV *SrcConst,
|
|
const SCEV *DstConst,
|
|
const Loop *CurrentLoop,
|
|
unsigned Level,
|
|
FullDependence &Result,
|
|
Constraint &NewConstraint) const;
|
|
|
|
/// weakZeroSrcSIVtest - Tests the weak-zero SIV subscript pair
|
|
/// (Src and Dst) for dependence.
|
|
/// Things of the form [c1] and [c2 + a*i],
|
|
/// where i is an induction variable, c1 and c2 are loop invariant,
|
|
/// and a is a constant. See also weakZeroDstSIVtest.
|
|
/// Returns true if any possible dependence is disproved.
|
|
/// If there might be a dependence, returns false.
|
|
/// Sets appropriate direction entry.
|
|
/// Set consistent to false.
|
|
/// If loop peeling will break the dependence, mark appropriately.
|
|
bool weakZeroSrcSIVtest(const SCEV *DstCoeff,
|
|
const SCEV *SrcConst,
|
|
const SCEV *DstConst,
|
|
const Loop *CurrentLoop,
|
|
unsigned Level,
|
|
FullDependence &Result,
|
|
Constraint &NewConstraint) const;
|
|
|
|
/// weakZeroDstSIVtest - Tests the weak-zero SIV subscript pair
|
|
/// (Src and Dst) for dependence.
|
|
/// Things of the form [c1 + a*i] and [c2],
|
|
/// where i is an induction variable, c1 and c2 are loop invariant,
|
|
/// and a is a constant. See also weakZeroSrcSIVtest.
|
|
/// Returns true if any possible dependence is disproved.
|
|
/// If there might be a dependence, returns false.
|
|
/// Sets appropriate direction entry.
|
|
/// Set consistent to false.
|
|
/// If loop peeling will break the dependence, mark appropriately.
|
|
bool weakZeroDstSIVtest(const SCEV *SrcCoeff,
|
|
const SCEV *SrcConst,
|
|
const SCEV *DstConst,
|
|
const Loop *CurrentLoop,
|
|
unsigned Level,
|
|
FullDependence &Result,
|
|
Constraint &NewConstraint) const;
|
|
|
|
/// exactRDIVtest - Tests the RDIV subscript pair for dependence.
|
|
/// Things of the form [c1 + a*i] and [c2 + b*j],
|
|
/// where i and j are induction variable, c1 and c2 are loop invariant,
|
|
/// and a and b are constants.
|
|
/// Returns true if any possible dependence is disproved.
|
|
/// Marks the result as inconsistent.
|
|
/// Works in some cases that symbolicRDIVtest doesn't,
|
|
/// and vice versa.
|
|
bool exactRDIVtest(const SCEV *SrcCoeff,
|
|
const SCEV *DstCoeff,
|
|
const SCEV *SrcConst,
|
|
const SCEV *DstConst,
|
|
const Loop *SrcLoop,
|
|
const Loop *DstLoop,
|
|
FullDependence &Result) const;
|
|
|
|
/// symbolicRDIVtest - Tests the RDIV subscript pair for dependence.
|
|
/// Things of the form [c1 + a*i] and [c2 + b*j],
|
|
/// where i and j are induction variable, c1 and c2 are loop invariant,
|
|
/// and a and b are constants.
|
|
/// Returns true if any possible dependence is disproved.
|
|
/// Marks the result as inconsistent.
|
|
/// Works in some cases that exactRDIVtest doesn't,
|
|
/// and vice versa. Can also be used as a backup for
|
|
/// ordinary SIV tests.
|
|
bool symbolicRDIVtest(const SCEV *SrcCoeff,
|
|
const SCEV *DstCoeff,
|
|
const SCEV *SrcConst,
|
|
const SCEV *DstConst,
|
|
const Loop *SrcLoop,
|
|
const Loop *DstLoop) const;
|
|
|
|
/// gcdMIVtest - Tests an MIV subscript pair for dependence.
|
|
/// Returns true if any possible dependence is disproved.
|
|
/// Marks the result as inconsistent.
|
|
/// Can sometimes disprove the equal direction for 1 or more loops.
|
|
// Can handle some symbolics that even the SIV tests don't get,
|
|
/// so we use it as a backup for everything.
|
|
bool gcdMIVtest(const SCEV *Src,
|
|
const SCEV *Dst,
|
|
FullDependence &Result) const;
|
|
|
|
/// banerjeeMIVtest - Tests an MIV subscript pair for dependence.
|
|
/// Returns true if any possible dependence is disproved.
|
|
/// Marks the result as inconsistent.
|
|
/// Computes directions.
|
|
bool banerjeeMIVtest(const SCEV *Src,
|
|
const SCEV *Dst,
|
|
const SmallBitVector &Loops,
|
|
FullDependence &Result) const;
|
|
|
|
/// collectCoefficientInfo - Walks through the subscript,
|
|
/// collecting each coefficient, the associated loop bounds,
|
|
/// and recording its positive and negative parts for later use.
|
|
CoefficientInfo *collectCoeffInfo(const SCEV *Subscript,
|
|
bool SrcFlag,
|
|
const SCEV *&Constant) const;
|
|
|
|
/// getPositivePart - X^+ = max(X, 0).
|
|
///
|
|
const SCEV *getPositivePart(const SCEV *X) const;
|
|
|
|
/// getNegativePart - X^- = min(X, 0).
|
|
///
|
|
const SCEV *getNegativePart(const SCEV *X) const;
|
|
|
|
/// getLowerBound - Looks through all the bounds info and
|
|
/// computes the lower bound given the current direction settings
|
|
/// at each level.
|
|
const SCEV *getLowerBound(BoundInfo *Bound) const;
|
|
|
|
/// getUpperBound - Looks through all the bounds info and
|
|
/// computes the upper bound given the current direction settings
|
|
/// at each level.
|
|
const SCEV *getUpperBound(BoundInfo *Bound) const;
|
|
|
|
/// exploreDirections - Hierarchically expands the direction vector
|
|
/// search space, combining the directions of discovered dependences
|
|
/// in the DirSet field of Bound. Returns the number of distinct
|
|
/// dependences discovered. If the dependence is disproved,
|
|
/// it will return 0.
|
|
unsigned exploreDirections(unsigned Level,
|
|
CoefficientInfo *A,
|
|
CoefficientInfo *B,
|
|
BoundInfo *Bound,
|
|
const SmallBitVector &Loops,
|
|
unsigned &DepthExpanded,
|
|
const SCEV *Delta) const;
|
|
|
|
/// testBounds - Returns true iff the current bounds are plausible.
|
|
///
|
|
bool testBounds(unsigned char DirKind,
|
|
unsigned Level,
|
|
BoundInfo *Bound,
|
|
const SCEV *Delta) const;
|
|
|
|
/// findBoundsALL - Computes the upper and lower bounds for level K
|
|
/// using the * direction. Records them in Bound.
|
|
void findBoundsALL(CoefficientInfo *A,
|
|
CoefficientInfo *B,
|
|
BoundInfo *Bound,
|
|
unsigned K) const;
|
|
|
|
/// findBoundsLT - Computes the upper and lower bounds for level K
|
|
/// using the < direction. Records them in Bound.
|
|
void findBoundsLT(CoefficientInfo *A,
|
|
CoefficientInfo *B,
|
|
BoundInfo *Bound,
|
|
unsigned K) const;
|
|
|
|
/// findBoundsGT - Computes the upper and lower bounds for level K
|
|
/// using the > direction. Records them in Bound.
|
|
void findBoundsGT(CoefficientInfo *A,
|
|
CoefficientInfo *B,
|
|
BoundInfo *Bound,
|
|
unsigned K) const;
|
|
|
|
/// findBoundsEQ - Computes the upper and lower bounds for level K
|
|
/// using the = direction. Records them in Bound.
|
|
void findBoundsEQ(CoefficientInfo *A,
|
|
CoefficientInfo *B,
|
|
BoundInfo *Bound,
|
|
unsigned K) const;
|
|
|
|
/// intersectConstraints - Updates X with the intersection
|
|
/// of the Constraints X and Y. Returns true if X has changed.
|
|
bool intersectConstraints(Constraint *X,
|
|
const Constraint *Y);
|
|
|
|
/// propagate - Review the constraints, looking for opportunities
|
|
/// to simplify a subscript pair (Src and Dst).
|
|
/// Return true if some simplification occurs.
|
|
/// If the simplification isn't exact (that is, if it is conservative
|
|
/// in terms of dependence), set consistent to false.
|
|
bool propagate(const SCEV *&Src,
|
|
const SCEV *&Dst,
|
|
SmallBitVector &Loops,
|
|
SmallVector<Constraint, 4> &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;
|
|
public:
|
|
static char ID; // Class identification, replacement for typeinfo
|
|
DependenceAnalysis() : FunctionPass(ID) {
|
|
initializeDependenceAnalysisPass(*PassRegistry::getPassRegistry());
|
|
}
|
|
|
|
bool runOnFunction(Function &F);
|
|
void releaseMemory();
|
|
void getAnalysisUsage(AnalysisUsage &) const;
|
|
void print(raw_ostream &, const Module * = 0) const;
|
|
}; // class DependenceAnalysis
|
|
|
|
/// createDependenceAnalysisPass - This creates an instance of the
|
|
/// DependenceAnalysis pass.
|
|
FunctionPass *createDependenceAnalysisPass();
|
|
|
|
} // namespace llvm
|
|
|
|
#endif
|