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//===- llvm/Analysis/LoopDependenceAnalysis.h --------------- -*- C++ -*---===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// LoopDependenceAnalysis is an LLVM pass that analyses dependences in memory
// accesses in loops.
//
// Please note that this is work in progress and the interface is subject to
// change.
//
// TODO: adapt as interface progresses
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ANALYSIS_LOOP_DEPENDENCE_ANALYSIS_H
#define LLVM_ANALYSIS_LOOP_DEPENDENCE_ANALYSIS_H
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/FoldingSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Support/Allocator.h"
namespace llvm {
class AliasAnalysis;
class AnalysisUsage;
class ScalarEvolution;
class SCEV;
class Value;
class raw_ostream;
class LoopDependenceAnalysis : public LoopPass {
AliasAnalysis *AA;
ScalarEvolution *SE;
/// L - The loop we are currently analysing.
Loop *L;
/// TODO: doc
enum DependenceResult { Independent = 0, Dependent = 1, Unknown = 2 };
/// TODO: doc
struct Subscript {
/// TODO: Add distance, direction, breaking conditions, ...
};
/// DependencePair - Represents a data dependence relation between to memory
/// reference instructions.
struct DependencePair : public FastFoldingSetNode {
Value *A;
Value *B;
DependenceResult Result;
SmallVector<Subscript, 4> Subscripts;
DependencePair(const FoldingSetNodeID &ID, Value *a, Value *b) :
FastFoldingSetNode(ID), A(a), B(b), Result(Unknown), Subscripts() {}
};
/// findOrInsertDependencePair - Return true if a DependencePair for the
/// given Values already exists, false if a new DependencePair had to be
/// created. The third argument is set to the pair found or created.
bool findOrInsertDependencePair(Value*, Value*, DependencePair*&);
/// getLoops - Collect all loops of the loop nest L in which
/// a given SCEV is variant.
void getLoops(const SCEV*, DenseSet<const Loop*>*) const;
/// isLoopInvariant - True if a given SCEV is invariant in all loops of the
/// loop nest starting at the innermost loop L.
bool isLoopInvariant(const SCEV*) const;
/// isAffine - An SCEV is affine with respect to the loop nest starting at
/// the innermost loop L if it is of the form A+B*X where A, B are invariant
/// in the loop nest and X is a induction variable in the loop nest.
bool isAffine(const SCEV*) const;
/// TODO: doc
bool isZIVPair(const SCEV*, const SCEV*) const;
bool isSIVPair(const SCEV*, const SCEV*) const;
DependenceResult analyseZIV(const SCEV*, const SCEV*, Subscript*) const;
DependenceResult analyseSIV(const SCEV*, const SCEV*, Subscript*) const;
DependenceResult analyseMIV(const SCEV*, const SCEV*, Subscript*) const;
DependenceResult analyseSubscript(const SCEV*, const SCEV*, Subscript*) const;
DependenceResult analysePair(DependencePair*) const;
public:
static char ID; // Class identification, replacement for typeinfo
LoopDependenceAnalysis() : LoopPass(&ID) {}
/// isDependencePair - Check whether two values can possibly give rise to
/// a data dependence: that is the case if both are instructions accessing
/// memory and at least one of those accesses is a write.
bool isDependencePair(const Value*, const Value*) const;
/// depends - Return a boolean indicating if there is a data dependence
/// between two instructions.
bool depends(Value*, Value*);
bool runOnLoop(Loop*, LPPassManager&);
virtual void releaseMemory();
virtual void getAnalysisUsage(AnalysisUsage&) const;
void print(raw_ostream&, const Module* = 0) const;
private:
FoldingSet<DependencePair> Pairs;
BumpPtrAllocator PairAllocator;
}; // class LoopDependenceAnalysis
// createLoopDependenceAnalysisPass - This creates an instance of the
// LoopDependenceAnalysis pass.
//
LoopPass *createLoopDependenceAnalysisPass();
} // namespace llvm
#endif /* LLVM_ANALYSIS_LOOP_DEPENDENCE_ANALYSIS_H */
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