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LoopDependenceAnalysis::getLoops is currently O(N*M) for a loop-nest of depth N and a compound SCEV of M atomic SCEVs. As both N and M will typically be very small, this should not be a problem. If it turns out to be one, rewriting getLoops as SCEVVisitor will reduce complexity to O(M). llvm-svn: 78394
125 lines
4.2 KiB
C++
125 lines
4.2 KiB
C++
//===- llvm/Analysis/LoopDependenceAnalysis.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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// LoopDependenceAnalysis is an LLVM pass that analyses dependences in memory
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// accesses in loops.
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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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// TODO: adapt as interface progresses
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ANALYSIS_LOOP_DEPENDENCE_ANALYSIS_H
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#define LLVM_ANALYSIS_LOOP_DEPENDENCE_ANALYSIS_H
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#include "llvm/ADT/DenseSet.h"
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#include "llvm/ADT/FoldingSet.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/Analysis/LoopPass.h"
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#include "llvm/Support/Allocator.h"
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#include <iosfwd>
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namespace llvm {
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class AliasAnalysis;
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class AnalysisUsage;
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class ScalarEvolution;
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class SCEV;
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class Value;
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class raw_ostream;
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class LoopDependenceAnalysis : public LoopPass {
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AliasAnalysis *AA;
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ScalarEvolution *SE;
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/// L - The loop we are currently analysing.
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Loop *L;
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/// TODO: doc
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enum DependenceResult { Independent = 0, Dependent = 1, Unknown = 2 };
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/// TODO: doc
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struct Subscript {
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/// TODO: Add distance, direction, breaking conditions, ...
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};
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/// DependencePair - Represents a data dependence relation between to memory
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/// reference instructions.
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struct DependencePair : public FastFoldingSetNode {
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Value *A;
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Value *B;
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DependenceResult Result;
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SmallVector<Subscript, 4> Subscripts;
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DependencePair(const FoldingSetNodeID &ID, Value *a, Value *b) :
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FastFoldingSetNode(ID), A(a), B(b), Result(Unknown), Subscripts() {}
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};
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/// findOrInsertDependencePair - Return true if a DependencePair for the
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/// given Values already exists, false if a new DependencePair had to be
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/// created. The third argument is set to the pair found or created.
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bool findOrInsertDependencePair(Value*, Value*, DependencePair*&);
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/// getLoops - Collect all loops of the loop-nest L a given SCEV is variant
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/// in.
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void getLoops(const SCEV*, DenseSet<const Loop*>*) const;
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/// isLoopInvariant - True if a given SCEV is invariant in all loops of the
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/// loop-nest starting at the innermost loop L.
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bool isLoopInvariant(const SCEV*) const;
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/// isAffine - An SCEV is affine with respect to the loop-nest starting at
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/// the innermost loop L if it is of the form A+B*X where A, B are invariant
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/// in the loop-nest and X is a induction variable in the loop-nest.
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bool isAffine(const SCEV*) const;
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/// TODO: doc
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bool isZIVPair(const SCEV*, const SCEV*) const;
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bool isSIVPair(const SCEV*, const SCEV*) const;
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DependenceResult analyseZIV(const SCEV*, const SCEV*, Subscript*) const;
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DependenceResult analyseSIV(const SCEV*, const SCEV*, Subscript*) const;
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DependenceResult analyseMIV(const SCEV*, const SCEV*, Subscript*) const;
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DependenceResult analyseSubscript(const SCEV*, const SCEV*, Subscript*) const;
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DependenceResult analysePair(DependencePair*) const;
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public:
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static char ID; // Class identification, replacement for typeinfo
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LoopDependenceAnalysis() : LoopPass(&ID) {}
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/// isDependencePair - Check wether two values can possibly give rise to a
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/// data dependence: that is the case if both are instructions accessing
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/// memory and at least one of those accesses is a write.
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bool isDependencePair(const Value*, const Value*) const;
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/// depends - Return a boolean indicating if there is a data dependence
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/// between two instructions.
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bool depends(Value*, Value*);
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bool runOnLoop(Loop*, LPPassManager&);
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virtual void releaseMemory();
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virtual void getAnalysisUsage(AnalysisUsage&) const;
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void print(raw_ostream&, const Module* = 0) const;
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virtual void print(std::ostream&, const Module* = 0) const;
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private:
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FoldingSet<DependencePair> Pairs;
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BumpPtrAllocator PairAllocator;
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}; // class LoopDependenceAnalysis
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// createLoopDependenceAnalysisPass - This creates an instance of the
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// LoopDependenceAnalysis pass.
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//
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LoopPass *createLoopDependenceAnalysisPass();
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} // namespace llvm
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#endif /* LLVM_ANALYSIS_LOOP_DEPENDENCE_ANALYSIS_H */
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