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4db669fb26
The only difference between these two is that VectorizerReport adds a vectorizer-specific prefix to its messages. When LAA is used in the vectorizer context the prefix is added when we promote the LoopAccessReport into a VectorizerReport via one of the constructors. This is part of the patchset that converts LoopAccessAnalysis into an actual analysis pass. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@229897 91177308-0d34-0410-b5e6-96231b3b80d8
275 lines
9.8 KiB
C++
275 lines
9.8 KiB
C++
//===- llvm/Analysis/LoopAccessAnalysis.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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// This file defines the interface for the loop memory dependence framework that
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// was originally developed for the Loop Vectorizer.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ANALYSIS_LOOPACCESSANALYSIS_H
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#define LLVM_ANALYSIS_LOOPACCESSANALYSIS_H
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#include "llvm/ADT/EquivalenceClasses.h"
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#include "llvm/ADT/Optional.h"
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#include "llvm/ADT/SetVector.h"
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#include "llvm/Analysis/AliasAnalysis.h"
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#include "llvm/Analysis/AliasSetTracker.h"
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#include "llvm/Analysis/ScalarEvolutionExpressions.h"
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#include "llvm/IR/ValueHandle.h"
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#include "llvm/Pass.h"
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#include "llvm/Support/raw_ostream.h"
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namespace llvm {
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class Value;
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class DataLayout;
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class AliasAnalysis;
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class ScalarEvolution;
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class Loop;
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class SCEV;
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/// Optimization analysis message produced during vectorization. Messages inform
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/// the user why vectorization did not occur.
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class LoopAccessReport {
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std::string Message;
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const Instruction *Instr;
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protected:
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LoopAccessReport(const Twine &Message, const Instruction *I)
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: Message(Message.str()), Instr(I) {}
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public:
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LoopAccessReport(const Instruction *I = nullptr) : Instr(I) {}
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template <typename A> LoopAccessReport &operator<<(const A &Value) {
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raw_string_ostream Out(Message);
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Out << Value;
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return *this;
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}
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const Instruction *getInstr() const { return Instr; }
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std::string &str() { return Message; }
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const std::string &str() const { return Message; }
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operator Twine() { return Message; }
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/// \brief Emit an analysis note for \p PassName with the debug location from
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/// the instruction in \p Message if available. Otherwise use the location of
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/// \p TheLoop.
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static void emitAnalysis(const LoopAccessReport &Message,
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const Function *TheFunction,
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const Loop *TheLoop,
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const char *PassName);
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};
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/// \brief Collection of parameters shared beetween the Loop Vectorizer and the
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/// Loop Access Analysis.
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struct VectorizerParams {
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/// \brief Maximum SIMD width.
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static const unsigned MaxVectorWidth;
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/// \brief VF as overridden by the user.
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static unsigned VectorizationFactor;
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/// \brief Interleave factor as overridden by the user.
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static unsigned VectorizationInterleave;
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/// \brief True if force-vector-interleave was specified by the user.
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static bool isInterleaveForced();
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/// \\brief When performing memory disambiguation checks at runtime do not
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/// make more than this number of comparisons.
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static const unsigned RuntimeMemoryCheckThreshold;
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};
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/// \brief Drive the analysis of memory accesses in the loop
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///
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/// This class is responsible for analyzing the memory accesses of a loop. It
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/// collects the accesses and then its main helper the AccessAnalysis class
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/// finds and categorizes the dependences in buildDependenceSets.
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///
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/// For memory dependences that can be analyzed at compile time, it determines
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/// whether the dependence is part of cycle inhibiting vectorization. This work
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/// is delegated to the MemoryDepChecker class.
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///
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/// For memory dependences that cannot be determined at compile time, it
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/// generates run-time checks to prove independence. This is done by
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/// AccessAnalysis::canCheckPtrAtRT and the checks are maintained by the
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/// RuntimePointerCheck class.
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class LoopAccessInfo {
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public:
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/// This struct holds information about the memory runtime legality check that
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/// a group of pointers do not overlap.
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struct RuntimePointerCheck {
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RuntimePointerCheck() : Need(false) {}
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/// Reset the state of the pointer runtime information.
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void reset() {
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Need = false;
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Pointers.clear();
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Starts.clear();
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Ends.clear();
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IsWritePtr.clear();
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DependencySetId.clear();
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AliasSetId.clear();
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}
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/// Insert a pointer and calculate the start and end SCEVs.
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void insert(ScalarEvolution *SE, Loop *Lp, Value *Ptr, bool WritePtr,
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unsigned DepSetId, unsigned ASId, ValueToValueMap &Strides);
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/// \brief Decide whether we need to issue a run-time check for pointer at
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/// index \p I and \p J to prove their independence.
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bool needsChecking(unsigned I, unsigned J) const;
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/// This flag indicates if we need to add the runtime check.
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bool Need;
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/// Holds the pointers that we need to check.
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SmallVector<TrackingVH<Value>, 2> Pointers;
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/// Holds the pointer value at the beginning of the loop.
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SmallVector<const SCEV*, 2> Starts;
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/// Holds the pointer value at the end of the loop.
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SmallVector<const SCEV*, 2> Ends;
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/// Holds the information if this pointer is used for writing to memory.
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SmallVector<bool, 2> IsWritePtr;
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/// Holds the id of the set of pointers that could be dependent because of a
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/// shared underlying object.
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SmallVector<unsigned, 2> DependencySetId;
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/// Holds the id of the disjoint alias set to which this pointer belongs.
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SmallVector<unsigned, 2> AliasSetId;
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};
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LoopAccessInfo(Loop *L, ScalarEvolution *SE, const DataLayout *DL,
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const TargetLibraryInfo *TLI, AliasAnalysis *AA,
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DominatorTree *DT, ValueToValueMap &Strides);
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/// Return true we can analyze the memory accesses in the loop and there are
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/// no memory dependence cycles.
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bool canVectorizeMemory() { return CanVecMem; }
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RuntimePointerCheck *getRuntimePointerCheck() { return &PtrRtCheck; }
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/// Return true if the block BB needs to be predicated in order for the loop
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/// to be vectorized.
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static bool blockNeedsPredication(BasicBlock *BB, Loop *TheLoop,
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DominatorTree *DT);
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/// Returns true if the value V is uniform within the loop.
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bool isUniform(Value *V);
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unsigned getMaxSafeDepDistBytes() const { return MaxSafeDepDistBytes; }
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unsigned getNumStores() const { return NumStores; }
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unsigned getNumLoads() const { return NumLoads;}
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/// \brief Add code that checks at runtime if the accessed arrays overlap.
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///
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/// Returns a pair of instructions where the first element is the first
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/// instruction generated in possibly a sequence of instructions and the
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/// second value is the final comparator value or NULL if no check is needed.
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std::pair<Instruction *, Instruction *> addRuntimeCheck(Instruction *Loc);
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/// \brief The diagnostics report generated for the analysis. E.g. why we
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/// couldn't analyze the loop.
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Optional<LoopAccessReport> &getReport() { return Report; }
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/// \brief Used to ensure that if the analysis was run with speculating the
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/// value of symbolic strides, the client queries it with the same assumption.
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/// Only used in DEBUG build but we don't want NDEBUG-depedent ABI.
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unsigned NumSymbolicStrides;
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private:
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/// \brief Analyze the loop. Substitute symbolic strides using Strides.
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void analyzeLoop(ValueToValueMap &Strides);
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/// \brief Check if the structure of the loop allows it to be analyzed by this
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/// pass.
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bool canAnalyzeLoop();
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void emitAnalysis(LoopAccessReport &Message);
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/// We need to check that all of the pointers in this list are disjoint
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/// at runtime.
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RuntimePointerCheck PtrRtCheck;
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Loop *TheLoop;
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ScalarEvolution *SE;
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const DataLayout *DL;
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const TargetLibraryInfo *TLI;
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AliasAnalysis *AA;
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DominatorTree *DT;
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unsigned NumLoads;
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unsigned NumStores;
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unsigned MaxSafeDepDistBytes;
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/// \brief Cache the result of analyzeLoop.
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bool CanVecMem;
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/// \brief The diagnostics report generated for the analysis. E.g. why we
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/// couldn't analyze the loop.
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Optional<LoopAccessReport> Report;
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};
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Value *stripIntegerCast(Value *V);
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///\brief Return the SCEV corresponding to a pointer with the symbolic stride
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///replaced with constant one.
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///
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/// If \p OrigPtr is not null, use it to look up the stride value instead of \p
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/// Ptr. \p PtrToStride provides the mapping between the pointer value and its
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/// stride as collected by LoopVectorizationLegality::collectStridedAccess.
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const SCEV *replaceSymbolicStrideSCEV(ScalarEvolution *SE,
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ValueToValueMap &PtrToStride,
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Value *Ptr, Value *OrigPtr = nullptr);
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/// \brief This analysis provides dependence information for the memory accesses
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/// of a loop.
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///
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/// It runs the analysis for a loop on demand. This can be initiated by
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/// querying the loop access info via LAA::getInfo. getInfo return a
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/// LoopAccessInfo object. See this class for the specifics of what information
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/// is provided.
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class LoopAccessAnalysis : public FunctionPass {
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public:
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static char ID;
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LoopAccessAnalysis() : FunctionPass(ID) {
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initializeLoopAccessAnalysisPass(*PassRegistry::getPassRegistry());
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}
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bool runOnFunction(Function &F) override;
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void getAnalysisUsage(AnalysisUsage &AU) const override;
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/// \brief Query the result of the loop access information for the loop \p L.
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///
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/// If the client speculates (and then issues run-time checks) for the values
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/// of symbolic strides, \p Strides provides the mapping (see
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/// replaceSymbolicStrideSCEV). If there is no cached result available run
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/// the analysis.
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LoopAccessInfo &getInfo(Loop *L, ValueToValueMap &Strides);
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void releaseMemory() override {
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// Invalidate the cache when the pass is freed.
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LoopAccessInfoMap.clear();
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}
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private:
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/// \brief The cache.
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DenseMap<Loop *, std::unique_ptr<LoopAccessInfo>> LoopAccessInfoMap;
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// The used analysis passes.
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ScalarEvolution *SE;
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const DataLayout *DL;
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const TargetLibraryInfo *TLI;
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AliasAnalysis *AA;
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DominatorTree *DT;
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};
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} // End llvm namespace
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#endif
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