Subversion Repositories QNX 8.QNX8 LLVM/Clang compiler suite

//===- llvm/Analysis/ScalarEvolutionExpressions.h - SCEV Exprs --*- C++ -*-===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

//

// This file defines the classes used to represent and build scalar expressions.

//

//===----------------------------------------------------------------------===//

#ifndef LLVM_ANALYSIS_SCALAREVOLUTIONEXPRESSIONS_H

#define LLVM_ANALYSIS_SCALAREVOLUTIONEXPRESSIONS_H

#include "llvm/ADT/DenseMap.h"

#include "llvm/ADT/SmallPtrSet.h"

#include "llvm/ADT/SmallVector.h"

#include "llvm/ADT/iterator_range.h"

#include "llvm/Analysis/ScalarEvolution.h"

#include "llvm/IR/Constants.h"

#include "llvm/IR/ValueHandle.h"

#include "llvm/Support/Casting.h"

#include "llvm/Support/ErrorHandling.h"

#include <cassert>

#include <cstddef>

namespace llvm {

class APInt;

class Constant;

class ConstantInt;

class ConstantRange;

class Loop;

class Type;

class Value;

enum SCEVTypes : unsigned short {

  // These should be ordered in terms of increasing complexity to make the

  // folders simpler.

  scConstant,

  scTruncate,

  scZeroExtend,

  scSignExtend,

  scAddExpr,

  scMulExpr,

  scUDivExpr,

  scAddRecExpr,

  scUMaxExpr,

  scSMaxExpr,

  scUMinExpr,

  scSMinExpr,

  scSequentialUMinExpr,

  scPtrToInt,

  scUnknown,

  scCouldNotCompute

};

/// This class represents a constant integer value.

class SCEVConstant : public SCEV {

  friend class ScalarEvolution;

  ConstantInt *V;

  SCEVConstant(const FoldingSetNodeIDRef ID, ConstantInt *v)

      : SCEV(ID, scConstant, 1), V(v) {}

public:

  ConstantInt *getValue() const { return V; }

  const APInt &getAPInt() const { return getValue()->getValue(); }

  Type *getType() const { return V->getType(); }

  /// Methods for support type inquiry through isa, cast, and dyn_cast:

  static bool classof(const SCEV *S) { return S->getSCEVType() == scConstant; }

};

inline unsigned short computeExpressionSize(ArrayRef<const SCEV *> Args) {

  APInt Size(16, 1);

  for (const auto *Arg : Args)

    Size = Size.uadd_sat(APInt(16, Arg->getExpressionSize()));

  return (unsigned short)Size.getZExtValue();

}

/// This is the base class for unary cast operator classes.

class SCEVCastExpr : public SCEV {

protected:

  const SCEV *Op;

  Type *Ty;

  SCEVCastExpr(const FoldingSetNodeIDRef ID, SCEVTypes SCEVTy, const SCEV *op,

               Type *ty);

public:

  const SCEV *getOperand() const { return Op; }

  const SCEV *getOperand(unsigned i) const {

    assert(i == 0 && "Operand index out of range!");

    return Op;

  }

  ArrayRef<const SCEV *> operands() const { return Op; }

  size_t getNumOperands() const { return 1; }

  Type *getType() const { return Ty; }

  /// Methods for support type inquiry through isa, cast, and dyn_cast:

  static bool classof(const SCEV *S) {

    return S->getSCEVType() == scPtrToInt || S->getSCEVType() == scTruncate ||

           S->getSCEVType() == scZeroExtend || S->getSCEVType() == scSignExtend;

  }

};

/// This class represents a cast from a pointer to a pointer-sized integer

/// value.

class SCEVPtrToIntExpr : public SCEVCastExpr {

  friend class ScalarEvolution;

  SCEVPtrToIntExpr(const FoldingSetNodeIDRef ID, const SCEV *Op, Type *ITy);

public:

  /// Methods for support type inquiry through isa, cast, and dyn_cast:

  static bool classof(const SCEV *S) { return S->getSCEVType() == scPtrToInt; }

};

/// This is the base class for unary integral cast operator classes.

class SCEVIntegralCastExpr : public SCEVCastExpr {

protected:

  SCEVIntegralCastExpr(const FoldingSetNodeIDRef ID, SCEVTypes SCEVTy,

                       const SCEV *op, Type *ty);

public:

  /// Methods for support type inquiry through isa, cast, and dyn_cast:

  static bool classof(const SCEV *S) {

    return S->getSCEVType() == scTruncate || S->getSCEVType() == scZeroExtend ||

           S->getSCEVType() == scSignExtend;

  }

};

/// This class represents a truncation of an integer value to a

/// smaller integer value.

class SCEVTruncateExpr : public SCEVIntegralCastExpr {

  friend class ScalarEvolution;

  SCEVTruncateExpr(const FoldingSetNodeIDRef ID, const SCEV *op, Type *ty);

public:

  /// Methods for support type inquiry through isa, cast, and dyn_cast:

  static bool classof(const SCEV *S) { return S->getSCEVType() == scTruncate; }

};

/// This class represents a zero extension of a small integer value

/// to a larger integer value.

class SCEVZeroExtendExpr : public SCEVIntegralCastExpr {

  friend class ScalarEvolution;

  SCEVZeroExtendExpr(const FoldingSetNodeIDRef ID, const SCEV *op, Type *ty);

public:

  /// Methods for support type inquiry through isa, cast, and dyn_cast:

  static bool classof(const SCEV *S) {

    return S->getSCEVType() == scZeroExtend;

  }

};

/// This class represents a sign extension of a small integer value

/// to a larger integer value.

class SCEVSignExtendExpr : public SCEVIntegralCastExpr {

  friend class ScalarEvolution;

  SCEVSignExtendExpr(const FoldingSetNodeIDRef ID, const SCEV *op, Type *ty);

public:

  /// Methods for support type inquiry through isa, cast, and dyn_cast:

  static bool classof(const SCEV *S) {

    return S->getSCEVType() == scSignExtend;

  }

};

/// This node is a base class providing common functionality for

/// n'ary operators.

class SCEVNAryExpr : public SCEV {

protected:

  // Since SCEVs are immutable, ScalarEvolution allocates operand

  // arrays with its SCEVAllocator, so this class just needs a simple

  // pointer rather than a more elaborate vector-like data structure.

  // This also avoids the need for a non-trivial destructor.

  const SCEV *const *Operands;

  size_t NumOperands;

  SCEVNAryExpr(const FoldingSetNodeIDRef ID, enum SCEVTypes T,

               const SCEV *const *O, size_t N)

      : SCEV(ID, T, computeExpressionSize(ArrayRef(O, N))), Operands(O),

        NumOperands(N) {}

public:

  size_t getNumOperands() const { return NumOperands; }

  const SCEV *getOperand(unsigned i) const {

    assert(i < NumOperands && "Operand index out of range!");

    return Operands[i];

  }

  ArrayRef<const SCEV *> operands() const {

    return ArrayRef(Operands, NumOperands);

  }

  NoWrapFlags getNoWrapFlags(NoWrapFlags Mask = NoWrapMask) const {

    return (NoWrapFlags)(SubclassData & Mask);

  }

  bool hasNoUnsignedWrap() const {

    return getNoWrapFlags(FlagNUW) != FlagAnyWrap;

  }

  bool hasNoSignedWrap() const {

    return getNoWrapFlags(FlagNSW) != FlagAnyWrap;

  }

  bool hasNoSelfWrap() const { return getNoWrapFlags(FlagNW) != FlagAnyWrap; }

  /// Methods for support type inquiry through isa, cast, and dyn_cast:

  static bool classof(const SCEV *S) {

    return S->getSCEVType() == scAddExpr || S->getSCEVType() == scMulExpr ||

           S->getSCEVType() == scSMaxExpr || S->getSCEVType() == scUMaxExpr ||

           S->getSCEVType() == scSMinExpr || S->getSCEVType() == scUMinExpr ||

           S->getSCEVType() == scSequentialUMinExpr ||

           S->getSCEVType() == scAddRecExpr;

  }

};

/// This node is the base class for n'ary commutative operators.

class SCEVCommutativeExpr : public SCEVNAryExpr {

protected:

  SCEVCommutativeExpr(const FoldingSetNodeIDRef ID, enum SCEVTypes T,

                      const SCEV *const *O, size_t N)

      : SCEVNAryExpr(ID, T, O, N) {}

public:

  /// Methods for support type inquiry through isa, cast, and dyn_cast:

  static bool classof(const SCEV *S) {

    return S->getSCEVType() == scAddExpr || S->getSCEVType() == scMulExpr ||

           S->getSCEVType() == scSMaxExpr || S->getSCEVType() == scUMaxExpr ||

           S->getSCEVType() == scSMinExpr || S->getSCEVType() == scUMinExpr;

  }

  /// Set flags for a non-recurrence without clearing previously set flags.

  void setNoWrapFlags(NoWrapFlags Flags) { SubclassData |= Flags; }

};

/// This node represents an addition of some number of SCEVs.

class SCEVAddExpr : public SCEVCommutativeExpr {

  friend class ScalarEvolution;

  Type *Ty;

  SCEVAddExpr(const FoldingSetNodeIDRef ID, const SCEV *const *O, size_t N)

      : SCEVCommutativeExpr(ID, scAddExpr, O, N) {

    auto *FirstPointerTypedOp = find_if(operands(), [](const SCEV *Op) {

      return Op->getType()->isPointerTy();

    });

    if (FirstPointerTypedOp != operands().end())

      Ty = (*FirstPointerTypedOp)->getType();

    else

      Ty = getOperand(0)->getType();

  }

public:

  Type *getType() const { return Ty; }

  /// Methods for support type inquiry through isa, cast, and dyn_cast:

  static bool classof(const SCEV *S) { return S->getSCEVType() == scAddExpr; }

};

/// This node represents multiplication of some number of SCEVs.

class SCEVMulExpr : public SCEVCommutativeExpr {

  friend class ScalarEvolution;

  SCEVMulExpr(const FoldingSetNodeIDRef ID, const SCEV *const *O, size_t N)

      : SCEVCommutativeExpr(ID, scMulExpr, O, N) {}

public:

  Type *getType() const { return getOperand(0)->getType(); }

  /// Methods for support type inquiry through isa, cast, and dyn_cast:

  static bool classof(const SCEV *S) { return S->getSCEVType() == scMulExpr; }

};

/// This class represents a binary unsigned division operation.

class SCEVUDivExpr : public SCEV {

  friend class ScalarEvolution;

  std::array<const SCEV *, 2> Operands;

  SCEVUDivExpr(const FoldingSetNodeIDRef ID, const SCEV *lhs, const SCEV *rhs)

      : SCEV(ID, scUDivExpr, computeExpressionSize({lhs, rhs})) {

    Operands[0] = lhs;

    Operands[1] = rhs;

  }

public:

  const SCEV *getLHS() const { return Operands[0]; }

  const SCEV *getRHS() const { return Operands[1]; }

  size_t getNumOperands() const { return 2; }

  const SCEV *getOperand(unsigned i) const {

    assert((i == 0 || i == 1) && "Operand index out of range!");

    return i == 0 ? getLHS() : getRHS();

  }

  ArrayRef<const SCEV *> operands() const { return Operands; }

  Type *getType() const {

    // In most cases the types of LHS and RHS will be the same, but in some

    // crazy cases one or the other may be a pointer. ScalarEvolution doesn't

    // depend on the type for correctness, but handling types carefully can

    // avoid extra casts in the SCEVExpander. The LHS is more likely to be

    // a pointer type than the RHS, so use the RHS' type here.

    return getRHS()->getType();

  }

  /// Methods for support type inquiry through isa, cast, and dyn_cast:

  static bool classof(const SCEV *S) { return S->getSCEVType() == scUDivExpr; }

};

/// This node represents a polynomial recurrence on the trip count

/// of the specified loop.  This is the primary focus of the

/// ScalarEvolution framework; all the other SCEV subclasses are

/// mostly just supporting infrastructure to allow SCEVAddRecExpr

/// expressions to be created and analyzed.

///

/// All operands of an AddRec are required to be loop invariant.

///

class SCEVAddRecExpr : public SCEVNAryExpr {

  friend class ScalarEvolution;

  const Loop *L;

  SCEVAddRecExpr(const FoldingSetNodeIDRef ID, const SCEV *const *O, size_t N,

                 const Loop *l)

      : SCEVNAryExpr(ID, scAddRecExpr, O, N), L(l) {}

public:

  Type *getType() const { return getStart()->getType(); }

  const SCEV *getStart() const { return Operands[0]; }

  const Loop *getLoop() const { return L; }

  /// Constructs and returns the recurrence indicating how much this

  /// expression steps by.  If this is a polynomial of degree N, it

  /// returns a chrec of degree N-1.  We cannot determine whether

  /// the step recurrence has self-wraparound.

  const SCEV *getStepRecurrence(ScalarEvolution &SE) const {

    if (isAffine())

      return getOperand(1);

    return SE.getAddRecExpr(

        SmallVector<const SCEV *, 3>(operands().drop_front()), getLoop(),

        FlagAnyWrap);

  }

  /// Return true if this represents an expression A + B*x where A

  /// and B are loop invariant values.

  bool isAffine() const {

    // We know that the start value is invariant.  This expression is thus

    // affine iff the step is also invariant.

    return getNumOperands() == 2;

  }

  /// Return true if this represents an expression A + B*x + C*x^2

  /// where A, B and C are loop invariant values.  This corresponds

  /// to an addrec of the form {L,+,M,+,N}

  bool isQuadratic() const { return getNumOperands() == 3; }

  /// Set flags for a recurrence without clearing any previously set flags.

  /// For AddRec, either NUW or NSW implies NW. Keep track of this fact here

  /// to make it easier to propagate flags.

  void setNoWrapFlags(NoWrapFlags Flags) {

    if (Flags & (FlagNUW | FlagNSW))

      Flags = ScalarEvolution::setFlags(Flags, FlagNW);

    SubclassData |= Flags;

  }

  /// Return the value of this chain of recurrences at the specified

  /// iteration number.

  const SCEV *evaluateAtIteration(const SCEV *It, ScalarEvolution &SE) const;

  /// Return the value of this chain of recurrences at the specified iteration

  /// number. Takes an explicit list of operands to represent an AddRec.

  static const SCEV *evaluateAtIteration(ArrayRef<const SCEV *> Operands,

                                         const SCEV *It, ScalarEvolution &SE);

  /// Return the number of iterations of this loop that produce

  /// values in the specified constant range.  Another way of

  /// looking at this is that it returns the first iteration number

  /// where the value is not in the condition, thus computing the

  /// exit count.  If the iteration count can't be computed, an

  /// instance of SCEVCouldNotCompute is returned.

  const SCEV *getNumIterationsInRange(const ConstantRange &Range,

                                      ScalarEvolution &SE) const;

  /// Return an expression representing the value of this expression

  /// one iteration of the loop ahead.

  const SCEVAddRecExpr *getPostIncExpr(ScalarEvolution &SE) const;

  /// Methods for support type inquiry through isa, cast, and dyn_cast:

  static bool classof(const SCEV *S) {

    return S->getSCEVType() == scAddRecExpr;

  }

};

/// This node is the base class min/max selections.

class SCEVMinMaxExpr : public SCEVCommutativeExpr {

  friend class ScalarEvolution;

  static bool isMinMaxType(enum SCEVTypes T) {

    return T == scSMaxExpr || T == scUMaxExpr || T == scSMinExpr ||

           T == scUMinExpr;

  }

protected:

  /// Note: Constructing subclasses via this constructor is allowed

  SCEVMinMaxExpr(const FoldingSetNodeIDRef ID, enum SCEVTypes T,

                 const SCEV *const *O, size_t N)

      : SCEVCommutativeExpr(ID, T, O, N) {

    assert(isMinMaxType(T));

    // Min and max never overflow

    setNoWrapFlags((NoWrapFlags)(FlagNUW | FlagNSW));

  }

public:

  Type *getType() const { return getOperand(0)->getType(); }

  static bool classof(const SCEV *S) { return isMinMaxType(S->getSCEVType()); }

  static enum SCEVTypes negate(enum SCEVTypes T) {

    switch (T) {

    case scSMaxExpr:

      return scSMinExpr;

    case scSMinExpr:

      return scSMaxExpr;

    case scUMaxExpr:

      return scUMinExpr;

    case scUMinExpr:

      return scUMaxExpr;

    default:

      llvm_unreachable("Not a min or max SCEV type!");

    }

  }

};

/// This class represents a signed maximum selection.

class SCEVSMaxExpr : public SCEVMinMaxExpr {

  friend class ScalarEvolution;

  SCEVSMaxExpr(const FoldingSetNodeIDRef ID, const SCEV *const *O, size_t N)

      : SCEVMinMaxExpr(ID, scSMaxExpr, O, N) {}

public:

  /// Methods for support type inquiry through isa, cast, and dyn_cast:

  static bool classof(const SCEV *S) { return S->getSCEVType() == scSMaxExpr; }

};

/// This class represents an unsigned maximum selection.

class SCEVUMaxExpr : public SCEVMinMaxExpr {

  friend class ScalarEvolution;

  SCEVUMaxExpr(const FoldingSetNodeIDRef ID, const SCEV *const *O, size_t N)

      : SCEVMinMaxExpr(ID, scUMaxExpr, O, N) {}

public:

  /// Methods for support type inquiry through isa, cast, and dyn_cast:

  static bool classof(const SCEV *S) { return S->getSCEVType() == scUMaxExpr; }

};

/// This class represents a signed minimum selection.

class SCEVSMinExpr : public SCEVMinMaxExpr {

  friend class ScalarEvolution;

  SCEVSMinExpr(const FoldingSetNodeIDRef ID, const SCEV *const *O, size_t N)

      : SCEVMinMaxExpr(ID, scSMinExpr, O, N) {}

public:

  /// Methods for support type inquiry through isa, cast, and dyn_cast:

  static bool classof(const SCEV *S) { return S->getSCEVType() == scSMinExpr; }

};

/// This class represents an unsigned minimum selection.

class SCEVUMinExpr : public SCEVMinMaxExpr {

  friend class ScalarEvolution;

  SCEVUMinExpr(const FoldingSetNodeIDRef ID, const SCEV *const *O, size_t N)

      : SCEVMinMaxExpr(ID, scUMinExpr, O, N) {}

public:

  /// Methods for support type inquiry through isa, cast, and dyn_cast:

  static bool classof(const SCEV *S) { return S->getSCEVType() == scUMinExpr; }

};

/// This node is the base class for sequential/in-order min/max selections.

/// Note that their fundamental difference from SCEVMinMaxExpr's is that they

/// are early-returning upon reaching saturation point.

/// I.e. given `0 umin_seq poison`, the result will be `0`,

/// while the result of `0 umin poison` is `poison`.

class SCEVSequentialMinMaxExpr : public SCEVNAryExpr {

  friend class ScalarEvolution;

  static bool isSequentialMinMaxType(enum SCEVTypes T) {

    return T == scSequentialUMinExpr;

  }

  /// Set flags for a non-recurrence without clearing previously set flags.

  void setNoWrapFlags(NoWrapFlags Flags) { SubclassData |= Flags; }

protected:

  /// Note: Constructing subclasses via this constructor is allowed

  SCEVSequentialMinMaxExpr(const FoldingSetNodeIDRef ID, enum SCEVTypes T,

                           const SCEV *const *O, size_t N)

      : SCEVNAryExpr(ID, T, O, N) {

    assert(isSequentialMinMaxType(T));

    // Min and max never overflow

    setNoWrapFlags((NoWrapFlags)(FlagNUW | FlagNSW));

  }

public:

  Type *getType() const { return getOperand(0)->getType(); }

  static SCEVTypes getEquivalentNonSequentialSCEVType(SCEVTypes Ty) {

    assert(isSequentialMinMaxType(Ty));

    switch (Ty) {

    case scSequentialUMinExpr:

      return scUMinExpr;

    default:

      llvm_unreachable("Not a sequential min/max type.");

    }

  }

  SCEVTypes getEquivalentNonSequentialSCEVType() const {

    return getEquivalentNonSequentialSCEVType(getSCEVType());

  }

  static bool classof(const SCEV *S) {

    return isSequentialMinMaxType(S->getSCEVType());

  }

};

/// This class represents a sequential/in-order unsigned minimum selection.

class SCEVSequentialUMinExpr : public SCEVSequentialMinMaxExpr {

  friend class ScalarEvolution;

  SCEVSequentialUMinExpr(const FoldingSetNodeIDRef ID, const SCEV *const *O,

                         size_t N)

      : SCEVSequentialMinMaxExpr(ID, scSequentialUMinExpr, O, N) {}

public:

  /// Methods for support type inquiry through isa, cast, and dyn_cast:

  static bool classof(const SCEV *S) {

    return S->getSCEVType() == scSequentialUMinExpr;

  }

};

/// This means that we are dealing with an entirely unknown SCEV

/// value, and only represent it as its LLVM Value.  This is the

/// "bottom" value for the analysis.

class SCEVUnknown final : public SCEV, private CallbackVH {

  friend class ScalarEvolution;

  /// The parent ScalarEvolution value. This is used to update the

  /// parent's maps when the value associated with a SCEVUnknown is

  /// deleted or RAUW'd.

  ScalarEvolution *SE;

  /// The next pointer in the linked list of all SCEVUnknown

  /// instances owned by a ScalarEvolution.

  SCEVUnknown *Next;

  SCEVUnknown(const FoldingSetNodeIDRef ID, Value *V, ScalarEvolution *se,

              SCEVUnknown *next)

      : SCEV(ID, scUnknown, 1), CallbackVH(V), SE(se), Next(next) {}

  // Implement CallbackVH.

  void deleted() override;

  void allUsesReplacedWith(Value *New) override;

public:

  Value *getValue() const { return getValPtr(); }

  /// @{

  /// Test whether this is a special constant representing a type

  /// size, alignment, or field offset in a target-independent

  /// manner, and hasn't happened to have been folded with other

  /// operations into something unrecognizable. This is mainly only

  /// useful for pretty-printing and other situations where it isn't

  /// absolutely required for these to succeed.

  bool isSizeOf(Type *&AllocTy) const;

  bool isAlignOf(Type *&AllocTy) const;

  bool isOffsetOf(Type *&STy, Constant *&FieldNo) const;

  /// @}

  Type *getType() const { return getValPtr()->getType(); }

  /// Methods for support type inquiry through isa, cast, and dyn_cast:

  static bool classof(const SCEV *S) { return S->getSCEVType() == scUnknown; }

};

/// This class defines a simple visitor class that may be used for

/// various SCEV analysis purposes.

template <typename SC, typename RetVal = void> struct SCEVVisitor {

  RetVal visit(const SCEV *S) {

    switch (S->getSCEVType()) {

    case scConstant:

      return ((SC *)this)->visitConstant((const SCEVConstant *)S);

    case scPtrToInt:

      return ((SC *)this)->visitPtrToIntExpr((const SCEVPtrToIntExpr *)S);

    case scTruncate:

      return ((SC *)this)->visitTruncateExpr((const SCEVTruncateExpr *)S);

    case scZeroExtend:

      return ((SC *)this)->visitZeroExtendExpr((const SCEVZeroExtendExpr *)S);

    case scSignExtend:

      return ((SC *)this)->visitSignExtendExpr((const SCEVSignExtendExpr *)S);

    case scAddExpr:

      return ((SC *)this)->visitAddExpr((const SCEVAddExpr *)S);

    case scMulExpr:

      return ((SC *)this)->visitMulExpr((const SCEVMulExpr *)S);

    case scUDivExpr:

      return ((SC *)this)->visitUDivExpr((const SCEVUDivExpr *)S);

    case scAddRecExpr:

      return ((SC *)this)->visitAddRecExpr((const SCEVAddRecExpr *)S);

    case scSMaxExpr:

      return ((SC *)this)->visitSMaxExpr((const SCEVSMaxExpr *)S);

    case scUMaxExpr:

      return ((SC *)this)->visitUMaxExpr((const SCEVUMaxExpr *)S);

    case scSMinExpr:

      return ((SC *)this)->visitSMinExpr((const SCEVSMinExpr *)S);

    case scUMinExpr:

      return ((SC *)this)->visitUMinExpr((const SCEVUMinExpr *)S);

    case scSequentialUMinExpr:

      return ((SC *)this)

          ->visitSequentialUMinExpr((const SCEVSequentialUMinExpr *)S);

    case scUnknown:

      return ((SC *)this)->visitUnknown((const SCEVUnknown *)S);

    case scCouldNotCompute:

      return ((SC *)this)->visitCouldNotCompute((const SCEVCouldNotCompute *)S);

    }

    llvm_unreachable("Unknown SCEV kind!");

  }

  RetVal visitCouldNotCompute(const SCEVCouldNotCompute *S) {

    llvm_unreachable("Invalid use of SCEVCouldNotCompute!");

  }

};

/// Visit all nodes in the expression tree using worklist traversal.

///

/// Visitor implements:

///   // return true to follow this node.

///   bool follow(const SCEV *S);

///   // return true to terminate the search.

///   bool isDone();

template <typename SV> class SCEVTraversal {

  SV &Visitor;

  SmallVector<const SCEV *, 8> Worklist;

  SmallPtrSet<const SCEV *, 8> Visited;

  void push(const SCEV *S) {

    if (Visited.insert(S).second && Visitor.follow(S))

      Worklist.push_back(S);

  }

public:

  SCEVTraversal(SV &V) : Visitor(V) {}

  void visitAll(const SCEV *Root) {

    push(Root);

    while (!Worklist.empty() && !Visitor.isDone()) {

      const SCEV *S = Worklist.pop_back_val();

      switch (S->getSCEVType()) {

      case scConstant:

      case scUnknown:

        continue;

      case scPtrToInt:

      case scTruncate:

      case scZeroExtend:

      case scSignExtend:

      case scAddExpr:

      case scMulExpr:

      case scUDivExpr:

      case scSMaxExpr:

      case scUMaxExpr:

      case scSMinExpr:

      case scUMinExpr:

      case scSequentialUMinExpr:

      case scAddRecExpr:

        for (const auto *Op : S->operands()) {

          push(Op);

          if (Visitor.isDone())

            break;

        }

        continue;

      case scCouldNotCompute:

        llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");

      }

      llvm_unreachable("Unknown SCEV kind!");

    }

  }

};

/// Use SCEVTraversal to visit all nodes in the given expression tree.

template <typename SV> void visitAll(const SCEV *Root, SV &Visitor) {

  SCEVTraversal<SV> T(Visitor);

  T.visitAll(Root);

}

/// Return true if any node in \p Root satisfies the predicate \p Pred.

template <typename PredTy>

bool SCEVExprContains(const SCEV *Root, PredTy Pred) {

  struct FindClosure {

    bool Found = false;

    PredTy Pred;

    FindClosure(PredTy Pred) : Pred(Pred) {}

    bool follow(const SCEV *S) {

      if (!Pred(S))

        return true;

      Found = true;

      return false;

    }

    bool isDone() const { return Found; }

  };

  FindClosure FC(Pred);

  visitAll(Root, FC);

  return FC.Found;

}

/// This visitor recursively visits a SCEV expression and re-writes it.

/// The result from each visit is cached, so it will return the same

/// SCEV for the same input.

template <typename SC>

class SCEVRewriteVisitor : public SCEVVisitor<SC, const SCEV *> {

protected:

  ScalarEvolution &SE;

  // Memoize the result of each visit so that we only compute once for

  // the same input SCEV. This is to avoid redundant computations when

  // a SCEV is referenced by multiple SCEVs. Without memoization, this

  // visit algorithm would have exponential time complexity in the worst

  // case, causing the compiler to hang on certain tests.

  DenseMap<const SCEV *, const SCEV *> RewriteResults;

public:

  SCEVRewriteVisitor(ScalarEvolution &SE) : SE(SE) {}

  const SCEV *visit(const SCEV *S) {

    auto It = RewriteResults.find(S);

    if (It != RewriteResults.end())

      return It->second;

    auto *Visited = SCEVVisitor<SC, const SCEV *>::visit(S);

    auto Result = RewriteResults.try_emplace(S, Visited);

    assert(Result.second && "Should insert a new entry");

    return Result.first->second;

  }

  const SCEV *visitConstant(const SCEVConstant *Constant) { return Constant; }