Coverage Report

Created: 2019-07-24 05:18

/Users/buildslave/jenkins/workspace/clang-stage2-coverage-R/llvm/include/llvm/Analysis/LoopAccessAnalysis.h
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//===- llvm/Analysis/LoopAccessAnalysis.h -----------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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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/LoopAnalysisManager.h"
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#include "llvm/Analysis/ScalarEvolutionExpressions.h"
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#include "llvm/IR/DiagnosticInfo.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;
32
class DataLayout;
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class ScalarEvolution;
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class Loop;
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class SCEV;
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class SCEVUnionPredicate;
37
class LoopAccessInfo;
38
class OptimizationRemarkEmitter;
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/// Collection of parameters shared beetween the Loop Vectorizer and the
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/// Loop Access Analysis.
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struct VectorizerParams {
43
  /// Maximum SIMD width.
44
  static const unsigned MaxVectorWidth;
45
46
  /// VF as overridden by the user.
47
  static unsigned VectorizationFactor;
48
  /// Interleave factor as overridden by the user.
49
  static unsigned VectorizationInterleave;
50
  /// True if force-vector-interleave was specified by the user.
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  static bool isInterleaveForced();
52
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  /// \When performing memory disambiguation checks at runtime do not
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  /// make more than this number of comparisons.
55
  static unsigned RuntimeMemoryCheckThreshold;
56
};
57
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/// Checks memory dependences among accesses to the same underlying
59
/// object to determine whether there vectorization is legal or not (and at
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/// which vectorization factor).
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///
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/// Note: This class will compute a conservative dependence for access to
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/// different underlying pointers. Clients, such as the loop vectorizer, will
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/// sometimes deal these potential dependencies by emitting runtime checks.
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///
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/// We use the ScalarEvolution framework to symbolically evalutate access
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/// functions pairs. Since we currently don't restructure the loop we can rely
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/// on the program order of memory accesses to determine their safety.
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/// At the moment we will only deem accesses as safe for:
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///  * A negative constant distance assuming program order.
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///
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///      Safe: tmp = a[i + 1];     OR     a[i + 1] = x;
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///            a[i] = tmp;                y = a[i];
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///
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///   The latter case is safe because later checks guarantuee that there can't
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///   be a cycle through a phi node (that is, we check that "x" and "y" is not
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///   the same variable: a header phi can only be an induction or a reduction, a
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///   reduction can't have a memory sink, an induction can't have a memory
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///   source). This is important and must not be violated (or we have to
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///   resort to checking for cycles through memory).
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///
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///  * A positive constant distance assuming program order that is bigger
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///    than the biggest memory access.
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///
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///     tmp = a[i]        OR              b[i] = x
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///     a[i+2] = tmp                      y = b[i+2];
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///
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///     Safe distance: 2 x sizeof(a[0]), and 2 x sizeof(b[0]), respectively.
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///
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///  * Zero distances and all accesses have the same size.
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///
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class MemoryDepChecker {
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public:
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  typedef PointerIntPair<Value *, 1, bool> MemAccessInfo;
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  typedef SmallVector<MemAccessInfo, 8> MemAccessInfoList;
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  /// Set of potential dependent memory accesses.
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  typedef EquivalenceClasses<MemAccessInfo> DepCandidates;
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  /// Type to keep track of the status of the dependence check. The order of
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  /// the elements is important and has to be from most permissive to least
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  /// permissive.
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  enum class VectorizationSafetyStatus {
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    // Can vectorize safely without RT checks. All dependences are known to be
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    // safe.
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    Safe,
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    // Can possibly vectorize with RT checks to overcome unknown dependencies.
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    PossiblySafeWithRtChecks,
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    // Cannot vectorize due to known unsafe dependencies.
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    Unsafe,
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  };
111
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  /// Dependece between memory access instructions.
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  struct Dependence {
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    /// The type of the dependence.
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    enum DepType {
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      // No dependence.
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      NoDep,
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      // We couldn't determine the direction or the distance.
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      Unknown,
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      // Lexically forward.
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      //
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      // FIXME: If we only have loop-independent forward dependences (e.g. a
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      // read and write of A[i]), LAA will locally deem the dependence "safe"
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      // without querying the MemoryDepChecker.  Therefore we can miss
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      // enumerating loop-independent forward dependences in
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      // getDependences.  Note that as soon as there are different
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      // indices used to access the same array, the MemoryDepChecker *is*
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      // queried and the dependence list is complete.
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      Forward,
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      // Forward, but if vectorized, is likely to prevent store-to-load
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      // forwarding.
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      ForwardButPreventsForwarding,
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      // Lexically backward.
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      Backward,
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      // Backward, but the distance allows a vectorization factor of
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      // MaxSafeDepDistBytes.
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      BackwardVectorizable,
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      // Same, but may prevent store-to-load forwarding.
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      BackwardVectorizableButPreventsForwarding
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    };
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    /// String version of the types.
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    static const char *DepName[];
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    /// Index of the source of the dependence in the InstMap vector.
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    unsigned Source;
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    /// Index of the destination of the dependence in the InstMap vector.
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    unsigned Destination;
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    /// The type of the dependence.
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    DepType Type;
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    Dependence(unsigned Source, unsigned Destination, DepType Type)
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30.2k
        : Source(Source), Destination(Destination), Type(Type) {}
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    /// Return the source instruction of the dependence.
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    Instruction *getSource(const LoopAccessInfo &LAI) const;
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    /// Return the destination instruction of the dependence.
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    Instruction *getDestination(const LoopAccessInfo &LAI) const;
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    /// Dependence types that don't prevent vectorization.
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    static VectorizationSafetyStatus isSafeForVectorization(DepType Type);
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    /// Lexically forward dependence.
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    bool isForward() const;
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    /// Lexically backward dependence.
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    bool isBackward() const;
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    /// May be a lexically backward dependence type (includes Unknown).
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    bool isPossiblyBackward() const;
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    /// Print the dependence.  \p Instr is used to map the instruction
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    /// indices to instructions.
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    void print(raw_ostream &OS, unsigned Depth,
174
               const SmallVectorImpl<Instruction *> &Instrs) const;
175
  };
176
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  MemoryDepChecker(PredicatedScalarEvolution &PSE, const Loop *L)
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      : PSE(PSE), InnermostLoop(L), AccessIdx(0), MaxSafeRegisterWidth(-1U),
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        FoundNonConstantDistanceDependence(false),
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191k
        Status(VectorizationSafetyStatus::Safe), RecordDependences(true) {}
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  /// Register the location (instructions are given increasing numbers)
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  /// of a write access.
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109k
  void addAccess(StoreInst *SI) {
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109k
    Value *Ptr = SI->getPointerOperand();
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109k
    Accesses[MemAccessInfo(Ptr, true)].push_back(AccessIdx);
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109k
    InstMap.push_back(SI);
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109k
    ++AccessIdx;
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109k
  }
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  /// Register the location (instructions are given increasing numbers)
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  /// of a write access.
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116k
  void addAccess(LoadInst *LI) {
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116k
    Value *Ptr = LI->getPointerOperand();
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116k
    Accesses[MemAccessInfo(Ptr, false)].push_back(AccessIdx);
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116k
    InstMap.push_back(LI);
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116k
    ++AccessIdx;
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116k
  }
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  /// Check whether the dependencies between the accesses are safe.
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  ///
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  /// Only checks sets with elements in \p CheckDeps.
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  bool areDepsSafe(DepCandidates &AccessSets, MemAccessInfoList &CheckDeps,
204
                   const ValueToValueMap &Strides);
205
206
  /// No memory dependence was encountered that would inhibit
207
  /// vectorization.
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  bool isSafeForVectorization() const {
209
27.3k
    return Status == VectorizationSafetyStatus::Safe;
210
27.3k
  }
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  /// The maximum number of bytes of a vector register we can vectorize
213
  /// the accesses safely with.
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22.1k
  uint64_t getMaxSafeDepDistBytes() { return MaxSafeDepDistBytes; }
215
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  /// Return the number of elements that are safe to operate on
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  /// simultaneously, multiplied by the size of the element in bits.
218
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  uint64_t getMaxSafeRegisterWidth() const { return MaxSafeRegisterWidth; }
219
220
  /// In same cases when the dependency check fails we can still
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  /// vectorize the loop with a dynamic array access check.
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1.76k
  bool shouldRetryWithRuntimeCheck() const {
223
1.76k
    return FoundNonConstantDistanceDependence &&
224
1.76k
           
Status == VectorizationSafetyStatus::PossiblySafeWithRtChecks592
;
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1.76k
  }
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  /// Returns the memory dependences.  If null is returned we exceeded
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  /// the MaxDependences threshold and this information is not
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  /// available.
230
207k
  const SmallVectorImpl<Dependence> *getDependences() const {
231
207k
    return RecordDependences ? 
&Dependences207k
:
nullptr119
;
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207k
  }
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  void clearDependences() { Dependences.clear(); }
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  /// The vector of memory access instructions.  The indices are used as
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  /// instruction identifiers in the Dependence class.
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22.2k
  const SmallVectorImpl<Instruction *> &getMemoryInstructions() const {
239
22.2k
    return InstMap;
240
22.2k
  }
241
242
  /// Generate a mapping between the memory instructions and their
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  /// indices according to program order.
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253
  DenseMap<Instruction *, unsigned> generateInstructionOrderMap() const {
245
253
    DenseMap<Instruction *, unsigned> OrderMap;
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253
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1.79k
    for (unsigned I = 0; I < InstMap.size(); 
++I1.53k
)
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      OrderMap[InstMap[I]] = I;
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    return OrderMap;
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  }
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  /// Find the set of instructions that read or write via \p Ptr.
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  SmallVector<Instruction *, 4> getInstructionsForAccess(Value *Ptr,
255
                                                         bool isWrite) const;
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257
private:
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  /// A wrapper around ScalarEvolution, used to add runtime SCEV checks, and
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  /// applies dynamic knowledge to simplify SCEV expressions and convert them
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  /// to a more usable form. We need this in case assumptions about SCEV
261
  /// expressions need to be made in order to avoid unknown dependences. For
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  /// example we might assume a unit stride for a pointer in order to prove
263
  /// that a memory access is strided and doesn't wrap.
264
  PredicatedScalarEvolution &PSE;
265
  const Loop *InnermostLoop;
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  /// Maps access locations (ptr, read/write) to program order.
268
  DenseMap<MemAccessInfo, std::vector<unsigned> > Accesses;
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  /// Memory access instructions in program order.
271
  SmallVector<Instruction *, 16> InstMap;
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273
  /// The program order index to be used for the next instruction.
274
  unsigned AccessIdx;
275
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  // We can access this many bytes in parallel safely.
277
  uint64_t MaxSafeDepDistBytes;
278
279
  /// Number of elements (from consecutive iterations) that are safe to
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  /// operate on simultaneously, multiplied by the size of the element in bits.
281
  /// The size of the element is taken from the memory access that is most
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  /// restrictive.
283
  uint64_t MaxSafeRegisterWidth;
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285
  /// If we see a non-constant dependence distance we can still try to
286
  /// vectorize this loop with runtime checks.
287
  bool FoundNonConstantDistanceDependence;
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  /// Result of the dependence checks, indicating whether the checked
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  /// dependences are safe for vectorization, require RT checks or are known to
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  /// be unsafe.
292
  VectorizationSafetyStatus Status;
293
294
  //// True if Dependences reflects the dependences in the
295
  //// loop.  If false we exceeded MaxDependences and
296
  //// Dependences is invalid.
297
  bool RecordDependences;
298
299
  /// Memory dependences collected during the analysis.  Only valid if
300
  /// RecordDependences is true.
301
  SmallVector<Dependence, 8> Dependences;
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303
  /// Check whether there is a plausible dependence between the two
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  /// accesses.
305
  ///
306
  /// Access \p A must happen before \p B in program order. The two indices
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  /// identify the index into the program order map.
308
  ///
309
  /// This function checks  whether there is a plausible dependence (or the
310
  /// absence of such can't be proved) between the two accesses. If there is a
311
  /// plausible dependence but the dependence distance is bigger than one
312
  /// element access it records this distance in \p MaxSafeDepDistBytes (if this
313
  /// distance is smaller than any other distance encountered so far).
314
  /// Otherwise, this function returns true signaling a possible dependence.
315
  Dependence::DepType isDependent(const MemAccessInfo &A, unsigned AIdx,
316
                                  const MemAccessInfo &B, unsigned BIdx,
317
                                  const ValueToValueMap &Strides);
318
319
  /// Check whether the data dependence could prevent store-load
320
  /// forwarding.
321
  ///
322
  /// \return false if we shouldn't vectorize at all or avoid larger
323
  /// vectorization factors by limiting MaxSafeDepDistBytes.
324
  bool couldPreventStoreLoadForward(uint64_t Distance, uint64_t TypeByteSize);
325
326
  /// Updates the current safety status with \p S. We can go from Safe to
327
  /// either PossiblySafeWithRtChecks or Unsafe and from
328
  /// PossiblySafeWithRtChecks to Unsafe.
329
  void mergeInStatus(VectorizationSafetyStatus S);
330
};
331
332
/// Holds information about the memory runtime legality checks to verify
333
/// that a group of pointers do not overlap.
334
class RuntimePointerChecking {
335
public:
336
  struct PointerInfo {
337
    /// Holds the pointer value that we need to check.
338
    TrackingVH<Value> PointerValue;
339
    /// Holds the smallest byte address accessed by the pointer throughout all
340
    /// iterations of the loop.
341
    const SCEV *Start;
342
    /// Holds the largest byte address accessed by the pointer throughout all
343
    /// iterations of the loop, plus 1.
344
    const SCEV *End;
345
    /// Holds the information if this pointer is used for writing to memory.
346
    bool IsWritePtr;
347
    /// Holds the id of the set of pointers that could be dependent because of a
348
    /// shared underlying object.
349
    unsigned DependencySetId;
350
    /// Holds the id of the disjoint alias set to which this pointer belongs.
351
    unsigned AliasSetId;
352
    /// SCEV for the access.
353
    const SCEV *Expr;
354
355
    PointerInfo(Value *PointerValue, const SCEV *Start, const SCEV *End,
356
                bool IsWritePtr, unsigned DependencySetId, unsigned AliasSetId,
357
                const SCEV *Expr)
358
        : PointerValue(PointerValue), Start(Start), End(End),
359
          IsWritePtr(IsWritePtr), DependencySetId(DependencySetId),
360
99.9k
          AliasSetId(AliasSetId), Expr(Expr) {}
361
  };
362
363
191k
  RuntimePointerChecking(ScalarEvolution *SE) : Need(false), SE(SE) {}
364
365
  /// Reset the state of the pointer runtime information.
366
4.66k
  void reset() {
367
4.66k
    Need = false;
368
4.66k
    Pointers.clear();
369
4.66k
    Checks.clear();
370
4.66k
  }
371
372
  /// Insert a pointer and calculate the start and end SCEVs.
373
  /// We need \p PSE in order to compute the SCEV expression of the pointer
374
  /// according to the assumptions that we've made during the analysis.
375
  /// The method might also version the pointer stride according to \p Strides,
376
  /// and add new predicates to \p PSE.
377
  void insert(Loop *Lp, Value *Ptr, bool WritePtr, unsigned DepSetId,
378
              unsigned ASId, const ValueToValueMap &Strides,
379
              PredicatedScalarEvolution &PSE);
380
381
  /// No run-time memory checking is necessary.
382
0
  bool empty() const { return Pointers.empty(); }
383
384
  /// A grouping of pointers. A single memcheck is required between
385
  /// two groups.
386
  struct CheckingPtrGroup {
387
    /// Create a new pointer checking group containing a single
388
    /// pointer, with index \p Index in RtCheck.
389
    CheckingPtrGroup(unsigned Index, RuntimePointerChecking &RtCheck)
390
        : RtCheck(RtCheck), High(RtCheck.Pointers[Index].End),
391
28.7k
          Low(RtCheck.Pointers[Index].Start) {
392
28.7k
      Members.push_back(Index);
393
28.7k
    }
394
395
    /// Tries to add the pointer recorded in RtCheck at index
396
    /// \p Index to this pointer checking group. We can only add a pointer
397
    /// to a checking group if we will still be able to get
398
    /// the upper and lower bounds of the check. Returns true in case
399
    /// of success, false otherwise.
400
    bool addPointer(unsigned Index);
401
402
    /// Constitutes the context of this pointer checking group. For each
403
    /// pointer that is a member of this group we will retain the index
404
    /// at which it appears in RtCheck.
405
    RuntimePointerChecking &RtCheck;
406
    /// The SCEV expression which represents the upper bound of all the
407
    /// pointers in this group.
408
    const SCEV *High;
409
    /// The SCEV expression which represents the lower bound of all the
410
    /// pointers in this group.
411
    const SCEV *Low;
412
    /// Indices of all the pointers that constitute this grouping.
413
    SmallVector<unsigned, 2> Members;
414
  };
415
416
  /// A memcheck which made up of a pair of grouped pointers.
417
  ///
418
  /// These *have* to be const for now, since checks are generated from
419
  /// CheckingPtrGroups in LAI::addRuntimeChecks which is a const member
420
  /// function.  FIXME: once check-generation is moved inside this class (after
421
  /// the PtrPartition hack is removed), we could drop const.
422
  typedef std::pair<const CheckingPtrGroup *, const CheckingPtrGroup *>
423
      PointerCheck;
424
425
  /// Generate the checks and store it.  This also performs the grouping
426
  /// of pointers to reduce the number of memchecks necessary.
427
  void generateChecks(MemoryDepChecker::DepCandidates &DepCands,
428
                      bool UseDependencies);
429
430
  /// Returns the checks that generateChecks created.
431
5.07k
  const SmallVector<PointerCheck, 4> &getChecks() const { return Checks; }
432
433
  /// Decide if we need to add a check between two groups of pointers,
434
  /// according to needsChecking.
435
  bool needsChecking(const CheckingPtrGroup &M,
436
                     const CheckingPtrGroup &N) const;
437
438
  /// Returns the number of run-time checks required according to
439
  /// needsChecking.
440
19.9k
  unsigned getNumberOfChecks() const { return Checks.size(); }
441
442
  /// Print the list run-time memory checks necessary.
443
  void print(raw_ostream &OS, unsigned Depth = 0) const;
444
445
  /// Print \p Checks.
446
  void printChecks(raw_ostream &OS, const SmallVectorImpl<PointerCheck> &Checks,
447
                   unsigned Depth = 0) const;
448
449
  /// This flag indicates if we need to add the runtime check.
450
  bool Need;
451
452
  /// Information about the pointers that may require checking.
453
  SmallVector<PointerInfo, 2> Pointers;
454
455
  /// Holds a partitioning of pointers into "check groups".
456
  SmallVector<CheckingPtrGroup, 2> CheckingGroups;
457
458
  /// Check if pointers are in the same partition
459
  ///
460
  /// \p PtrToPartition contains the partition number for pointers (-1 if the
461
  /// pointer belongs to multiple partitions).
462
  static bool
463
  arePointersInSamePartition(const SmallVectorImpl<int> &PtrToPartition,
464
                             unsigned PtrIdx1, unsigned PtrIdx2);
465
466
  /// Decide whether we need to issue a run-time check for pointer at
467
  /// index \p I and \p J to prove their independence.
468
  bool needsChecking(unsigned I, unsigned J) const;
469
470
  /// Return PointerInfo for pointer at index \p PtrIdx.
471
7.02k
  const PointerInfo &getPointerInfo(unsigned PtrIdx) const {
472
7.02k
    return Pointers[PtrIdx];
473
7.02k
  }
474
475
private:
476
  /// Groups pointers such that a single memcheck is required
477
  /// between two different groups. This will clear the CheckingGroups vector
478
  /// and re-compute it. We will only group dependecies if \p UseDependencies
479
  /// is true, otherwise we will create a separate group for each pointer.
480
  void groupChecks(MemoryDepChecker::DepCandidates &DepCands,
481
                   bool UseDependencies);
482
483
  /// Generate the checks and return them.
484
  SmallVector<PointerCheck, 4>
485
  generateChecks() const;
486
487
  /// Holds a pointer to the ScalarEvolution analysis.
488
  ScalarEvolution *SE;
489
490
  /// Set of run-time checks required to establish independence of
491
  /// otherwise may-aliasing pointers in the loop.
492
  SmallVector<PointerCheck, 4> Checks;
493
};
494
495
/// Drive the analysis of memory accesses in the loop
496
///
497
/// This class is responsible for analyzing the memory accesses of a loop.  It
498
/// collects the accesses and then its main helper the AccessAnalysis class
499
/// finds and categorizes the dependences in buildDependenceSets.
500
///
501
/// For memory dependences that can be analyzed at compile time, it determines
502
/// whether the dependence is part of cycle inhibiting vectorization.  This work
503
/// is delegated to the MemoryDepChecker class.
504
///
505
/// For memory dependences that cannot be determined at compile time, it
506
/// generates run-time checks to prove independence.  This is done by
507
/// AccessAnalysis::canCheckPtrAtRT and the checks are maintained by the
508
/// RuntimePointerCheck class.
509
///
510
/// If pointers can wrap or can't be expressed as affine AddRec expressions by
511
/// ScalarEvolution, we will generate run-time checks by emitting a
512
/// SCEVUnionPredicate.
513
///
514
/// Checks for both memory dependences and the SCEV predicates contained in the
515
/// PSE must be emitted in order for the results of this analysis to be valid.
516
class LoopAccessInfo {
517
public:
518
  LoopAccessInfo(Loop *L, ScalarEvolution *SE, const TargetLibraryInfo *TLI,
519
                 AliasAnalysis *AA, DominatorTree *DT, LoopInfo *LI);
520
521
  /// Return true we can analyze the memory accesses in the loop and there are
522
  /// no memory dependence cycles.
523
27.4k
  bool canVectorizeMemory() const { return CanVecMem; }
524
525
  /// Return true if there is a convergent operation in the loop. There may
526
  /// still be reported runtime pointer checks that would be required, but it is
527
  /// not legal to insert them.
528
116
  bool hasConvergentOp() const { return HasConvergentOp; }
529
530
28.4k
  const RuntimePointerChecking *getRuntimePointerChecking() const {
531
28.4k
    return PtrRtChecking.get();
532
28.4k
  }
533
534
  /// Number of memchecks required to prove independence of otherwise
535
  /// may-alias pointers.
536
19.9k
  unsigned getNumRuntimePointerChecks() const {
537
19.9k
    return PtrRtChecking->getNumberOfChecks();
538
19.9k
  }
539
540
  /// Return true if the block BB needs to be predicated in order for the loop
541
  /// to be vectorized.
542
  static bool blockNeedsPredication(BasicBlock *BB, Loop *TheLoop,
543
                                    DominatorTree *DT);
544
545
  /// Returns true if the value V is uniform within the loop.
546
  bool isUniform(Value *V) const;
547
548
38.8k
  uint64_t getMaxSafeDepDistBytes() const { return MaxSafeDepDistBytes; }
549
15.6k
  unsigned getNumStores() const { return NumStores; }
550
15.6k
  unsigned getNumLoads() const { return NumLoads;}
551
552
  /// Add code that checks at runtime if the accessed arrays overlap.
553
  ///
554
  /// Returns a pair of instructions where the first element is the first
555
  /// instruction generated in possibly a sequence of instructions and the
556
  /// second value is the final comparator value or NULL if no check is needed.
557
  std::pair<Instruction *, Instruction *>
558
  addRuntimeChecks(Instruction *Loc) const;
559
560
  /// Generete the instructions for the checks in \p PointerChecks.
561
  ///
562
  /// Returns a pair of instructions where the first element is the first
563
  /// instruction generated in possibly a sequence of instructions and the
564
  /// second value is the final comparator value or NULL if no check is needed.
565
  std::pair<Instruction *, Instruction *>
566
  addRuntimeChecks(Instruction *Loc,
567
                   const SmallVectorImpl<RuntimePointerChecking::PointerCheck>
568
                       &PointerChecks) const;
569
570
  /// The diagnostics report generated for the analysis.  E.g. why we
571
  /// couldn't analyze the loop.
572
27.4k
  const OptimizationRemarkAnalysis *getReport() const { return Report.get(); }
573
574
  /// the Memory Dependence Checker which can determine the
575
  /// loop-independent and loop-carried dependences between memory accesses.
576
249k
  const MemoryDepChecker &getDepChecker() const { return *DepChecker; }
577
578
  /// Return the list of instructions that use \p Ptr to read or write
579
  /// memory.
580
  SmallVector<Instruction *, 4> getInstructionsForAccess(Value *Ptr,
581
220
                                                         bool isWrite) const {
582
220
    return DepChecker->getInstructionsForAccess(Ptr, isWrite);
583
220
  }
584
585
  /// If an access has a symbolic strides, this maps the pointer value to
586
  /// the stride symbol.
587
338k
  const ValueToValueMap &getSymbolicStrides() const { return SymbolicStrides; }
588
589
  /// Pointer has a symbolic stride.
590
212k
  bool hasStride(Value *V) const { return StrideSet.count(V); }
591
592
  /// Print the information about the memory accesses in the loop.
593
  void print(raw_ostream &OS, unsigned Depth = 0) const;
594
595
  /// If the loop has memory dependence involving an invariant address, i.e. two
596
  /// stores or a store and a load, then return true, else return false.
597
19.9k
  bool hasDependenceInvolvingLoopInvariantAddress() const {
598
19.9k
    return HasDependenceInvolvingLoopInvariantAddress;
599
19.9k
  }
600
601
  /// Used to add runtime SCEV checks. Simplifies SCEV expressions and converts
602
  /// them to a more usable form.  All SCEV expressions during the analysis
603
  /// should be re-written (and therefore simplified) according to PSE.
604
  /// A user of LoopAccessAnalysis will need to emit the runtime checks
605
  /// associated with this predicate.
606
184k
  const PredicatedScalarEvolution &getPSE() const { return *PSE; }
607
608
private:
609
  /// Analyze the loop.
610
  void analyzeLoop(AliasAnalysis *AA, LoopInfo *LI,
611
                   const TargetLibraryInfo *TLI, DominatorTree *DT);
612
613
  /// Check if the structure of the loop allows it to be analyzed by this
614
  /// pass.
615
  bool canAnalyzeLoop();
616
617
  /// Save the analysis remark.
618
  ///
619
  /// LAA does not directly emits the remarks.  Instead it stores it which the
620
  /// client can retrieve and presents as its own analysis
621
  /// (e.g. -Rpass-analysis=loop-vectorize).
622
  OptimizationRemarkAnalysis &recordAnalysis(StringRef RemarkName,
623
                                             Instruction *Instr = nullptr);
624
625
  /// Collect memory access with loop invariant strides.
626
  ///
627
  /// Looks for accesses like "a[i * StrideA]" where "StrideA" is loop
628
  /// invariant.
629
  void collectStridedAccess(Value *LoadOrStoreInst);
630
631
  std::unique_ptr<PredicatedScalarEvolution> PSE;
632
633
  /// We need to check that all of the pointers in this list are disjoint
634
  /// at runtime. Using std::unique_ptr to make using move ctor simpler.
635
  std::unique_ptr<RuntimePointerChecking> PtrRtChecking;
636
637
  /// the Memory Dependence Checker which can determine the
638
  /// loop-independent and loop-carried dependences between memory accesses.
639
  std::unique_ptr<MemoryDepChecker> DepChecker;
640
641
  Loop *TheLoop;
642
643
  unsigned NumLoads;
644
  unsigned NumStores;
645
646
  uint64_t MaxSafeDepDistBytes;
647
648
  /// Cache the result of analyzeLoop.
649
  bool CanVecMem;
650
  bool HasConvergentOp;
651
652
  /// Indicator that there are non vectorizable stores to a uniform address.
653
  bool HasDependenceInvolvingLoopInvariantAddress;
654
655
  /// The diagnostics report generated for the analysis.  E.g. why we
656
  /// couldn't analyze the loop.
657
  std::unique_ptr<OptimizationRemarkAnalysis> Report;
658
659
  /// If an access has a symbolic strides, this maps the pointer value to
660
  /// the stride symbol.
661
  ValueToValueMap SymbolicStrides;
662
663
  /// Set of symbolic strides values.
664
  SmallPtrSet<Value *, 8> StrideSet;
665
};
666
667
Value *stripIntegerCast(Value *V);
668
669
/// Return the SCEV corresponding to a pointer with the symbolic stride
670
/// replaced with constant one, assuming the SCEV predicate associated with
671
/// \p PSE is true.
672
///
673
/// If necessary this method will version the stride of the pointer according
674
/// to \p PtrToStride and therefore add further predicates to \p PSE.
675
///
676
/// If \p OrigPtr is not null, use it to look up the stride value instead of \p
677
/// Ptr.  \p PtrToStride provides the mapping between the pointer value and its
678
/// stride as collected by LoopVectorizationLegality::collectStridedAccess.
679
const SCEV *replaceSymbolicStrideSCEV(PredicatedScalarEvolution &PSE,
680
                                      const ValueToValueMap &PtrToStride,
681
                                      Value *Ptr, Value *OrigPtr = nullptr);
682
683
/// If the pointer has a constant stride return it in units of its
684
/// element size.  Otherwise return zero.
685
///
686
/// Ensure that it does not wrap in the address space, assuming the predicate
687
/// associated with \p PSE is true.
688
///
689
/// If necessary this method will version the stride of the pointer according
690
/// to \p PtrToStride and therefore add further predicates to \p PSE.
691
/// The \p Assume parameter indicates if we are allowed to make additional
692
/// run-time assumptions.
693
int64_t getPtrStride(PredicatedScalarEvolution &PSE, Value *Ptr, const Loop *Lp,
694
                     const ValueToValueMap &StridesMap = ValueToValueMap(),
695
                     bool Assume = false, bool ShouldCheckWrap = true);
696
697
/// Attempt to sort the pointers in \p VL and return the sorted indices
698
/// in \p SortedIndices, if reordering is required.
699
///
700
/// Returns 'true' if sorting is legal, otherwise returns 'false'.
701
///
702
/// For example, for a given \p VL of memory accesses in program order, a[i+4],
703
/// a[i+0], a[i+1] and a[i+7], this function will sort the \p VL and save the
704
/// sorted indices in \p SortedIndices as a[i+0], a[i+1], a[i+4], a[i+7] and
705
/// saves the mask for actual memory accesses in program order in
706
/// \p SortedIndices as <1,2,0,3>
707
bool sortPtrAccesses(ArrayRef<Value *> VL, const DataLayout &DL,
708
                     ScalarEvolution &SE,
709
                     SmallVectorImpl<unsigned> &SortedIndices);
710
711
/// Returns true if the memory operations \p A and \p B are consecutive.
712
/// This is a simple API that does not depend on the analysis pass.
713
bool isConsecutiveAccess(Value *A, Value *B, const DataLayout &DL,
714
                         ScalarEvolution &SE, bool CheckType = true);
715
716
/// This analysis provides dependence information for the memory accesses
717
/// of a loop.
718
///
719
/// It runs the analysis for a loop on demand.  This can be initiated by
720
/// querying the loop access info via LAA::getInfo.  getInfo return a
721
/// LoopAccessInfo object.  See this class for the specifics of what information
722
/// is provided.
723
class LoopAccessLegacyAnalysis : public FunctionPass {
724
public:
725
  static char ID;
726
727
39.7k
  LoopAccessLegacyAnalysis() : FunctionPass(ID) {
728
39.7k
    initializeLoopAccessLegacyAnalysisPass(*PassRegistry::getPassRegistry());
729
39.7k
  }
730
731
  bool runOnFunction(Function &F) override;
732
733
  void getAnalysisUsage(AnalysisUsage &AU) const override;
734
735
  /// Query the result of the loop access information for the loop \p L.
736
  ///
737
  /// If there is no cached result available run the analysis.
738
  const LoopAccessInfo &getInfo(Loop *L);
739
740
836k
  void releaseMemory() override {
741
836k
    // Invalidate the cache when the pass is freed.
742
836k
    LoopAccessInfoMap.clear();
743
836k
  }
744
745
  /// Print the result of the analysis when invoked with -analyze.
746
  void print(raw_ostream &OS, const Module *M = nullptr) const override;
747
748
private:
749
  /// The cache.
750
  DenseMap<Loop *, std::unique_ptr<LoopAccessInfo>> LoopAccessInfoMap;
751
752
  // The used analysis passes.
753
  ScalarEvolution *SE;
754
  const TargetLibraryInfo *TLI;
755
  AliasAnalysis *AA;
756
  DominatorTree *DT;
757
  LoopInfo *LI;
758
};
759
760
/// This analysis provides dependence information for the memory
761
/// accesses of a loop.
762
///
763
/// It runs the analysis for a loop on demand.  This can be initiated by
764
/// querying the loop access info via AM.getResult<LoopAccessAnalysis>.
765
/// getResult return a LoopAccessInfo object.  See this class for the
766
/// specifics of what information is provided.
767
class LoopAccessAnalysis
768
    : public AnalysisInfoMixin<LoopAccessAnalysis> {
769
  friend AnalysisInfoMixin<LoopAccessAnalysis>;
770
  static AnalysisKey Key;
771
772
public:
773
  typedef LoopAccessInfo Result;
774
775
  Result run(Loop &L, LoopAnalysisManager &AM, LoopStandardAnalysisResults &AR);
776
};
777
778
inline Instruction *MemoryDepChecker::Dependence::getSource(
779
11.0k
    const LoopAccessInfo &LAI) const {
780
11.0k
  return LAI.getDepChecker().getMemoryInstructions()[Source];
781
11.0k
}
782
783
inline Instruction *MemoryDepChecker::Dependence::getDestination(
784
11.0k
    const LoopAccessInfo &LAI) const {
785
11.0k
  return LAI.getDepChecker().getMemoryInstructions()[Destination];
786
11.0k
}
787
788
} // End llvm namespace
789
790
#endif