text: //===- llvm/Analysis/ScalarEvolution.h - Scalar Evolution -------*- C++ -*-===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // The ScalarEvolution class is an LLVM pass which can be used to analyze and
  // categorize scalar expressions in loops.  It specializes in recognizing
  // general induction variables, representing them with the abstract and opaque
  // SCEV class.  Given this analysis, trip counts of loops and other important
  // properties can be obtained.
  //
  // This analysis is primarily useful for induction variable substitution and
  // strength reduction.
  //
  //===----------------------------------------------------------------------===//
  
  #ifndef LLVM_ANALYSIS_SCALAREVOLUTION_H
  #define LLVM_ANALYSIS_SCALAREVOLUTION_H
  
  #include "llvm/Pass.h"
  #include "llvm/Instructions.h"
  #include "llvm/Function.h"
  #include "llvm/Support/DataTypes.h"
  #include "llvm/Support/ValueHandle.h"
  #include "llvm/Support/Allocator.h"
  #include "llvm/Support/ConstantRange.h"
  #include "llvm/ADT/FoldingSet.h"
  #include "llvm/ADT/DenseMap.h"
  #include <map>
  
  namespace llvm {
    class APInt;
    class Constant;
    class ConstantInt;
    class DominatorTree;
    class Type;
    class ScalarEvolution;
    class TargetData;
    class LLVMContext;
    class Loop;
    class LoopInfo;
    class Operator;
    class SCEVUnknown;
    class SCEV;
    template<> struct FoldingSetTrait<SCEV>;
  
    /// SCEV - This class represents an analyzed expression in the program.  These
    /// are opaque objects that the client is not allowed to do much with
    /// directly.
    ///
    class SCEV : public FoldingSetNode {
      friend struct FoldingSetTrait<SCEV>;
  
      /// FastID - A reference to an Interned FoldingSetNodeID for this node.
      /// The ScalarEvolution's BumpPtrAllocator holds the data.
      FoldingSetNodeIDRef FastID;
  
      // The SCEV baseclass this node corresponds to
      const unsigned short SCEVType;
  
    protected:
      /// SubclassData - This field is initialized to zero and may be used in
      /// subclasses to store miscellaneous information.
      unsigned short SubclassData;
  
    private:
      SCEV(const SCEV &);            // DO NOT IMPLEMENT
      void operator=(const SCEV &);  // DO NOT IMPLEMENT
  
    public:
      explicit SCEV(const FoldingSetNodeIDRef ID, unsigned SCEVTy) :
        FastID(ID), SCEVType(SCEVTy), SubclassData(0) {}
  
      unsigned getSCEVType() const { return SCEVType; }
  
      /// getType - Return the LLVM type of this SCEV expression.
      ///
      const Type *getType() const;
  
      /// isZero - Return true if the expression is a constant zero.
      ///
      bool isZero() const;
  
      /// isOne - Return true if the expression is a constant one.
      ///
      bool isOne() const;
  
      /// isAllOnesValue - Return true if the expression is a constant
      /// all-ones value.
      ///
      bool isAllOnesValue() const;
  
      /// print - Print out the internal representation of this scalar to the
      /// specified stream.  This should really only be used for debugging
      /// purposes.
      void print(raw_ostream &OS) const;
  
      /// dump - This method is used for debugging.
      ///
      void dump() const;
    };
  
    // Specialize FoldingSetTrait for SCEV to avoid needing to compute
    // temporary FoldingSetNodeID values.
    template<> struct FoldingSetTrait<SCEV> : DefaultFoldingSetTrait<SCEV> {
      static void Profile(const SCEV &X, FoldingSetNodeID& ID) {
        ID = X.FastID;
      }
      static bool Equals(const SCEV &X, const FoldingSetNodeID &ID,
                         FoldingSetNodeID &TempID) {
        return ID == X.FastID;
      }
      static unsigned ComputeHash(const SCEV &X, FoldingSetNodeID &TempID) {
        return X.FastID.ComputeHash();
      }
    };
  
    inline raw_ostream &operator<<(raw_ostream &OS, const SCEV &S) {
      S.print(OS);
      return OS;
    }
  
    /// SCEVCouldNotCompute - An object of this class is returned by queries that
    /// could not be answered.  For example, if you ask for the number of
    /// iterations of a linked-list traversal loop, you will get one of these.
    /// None of the standard SCEV operations are valid on this class, it is just a
    /// marker.
    struct SCEVCouldNotCompute : public SCEV {
      SCEVCouldNotCompute();
  
      /// Methods for support type inquiry through isa, cast, and dyn_cast:
      static inline bool classof(const SCEVCouldNotCompute *S) { return true; }
      static bool classof(const SCEV *S);
    };
  
    /// ScalarEvolution - This class is the main scalar evolution driver.  Because
    /// client code (intentionally) can't do much with the SCEV objects directly,
    /// they must ask this class for services.
    ///
    class ScalarEvolution : public FunctionPass {
    public:
      /// LoopDisposition - An enum describing the relationship between a
      /// SCEV and a loop.
      enum LoopDisposition {
        LoopVariant,    ///< The SCEV is loop-variant (unknown).
        LoopInvariant,  ///< The SCEV is loop-invariant.
        LoopComputable  ///< The SCEV varies predictably with the loop.
      };
  
      /// BlockDisposition - An enum describing the relationship between a
      /// SCEV and a basic block.
      enum BlockDisposition {
        DoesNotDominateBlock,  ///< The SCEV does not dominate the block.
        DominatesBlock,        ///< The SCEV dominates the block.
        ProperlyDominatesBlock ///< The SCEV properly dominates the block.
      };
  
    private:
      /// SCEVCallbackVH - A CallbackVH to arrange for ScalarEvolution to be
      /// notified whenever a Value is deleted.
      class SCEVCallbackVH : public CallbackVH {
        ScalarEvolution *SE;
        virtual void deleted();
        virtual void allUsesReplacedWith(Value *New);
      public:
        SCEVCallbackVH(Value *V, ScalarEvolution *SE = 0);
      };
  
      friend class SCEVCallbackVH;
      friend class SCEVExpander;
      friend class SCEVUnknown;
  
      /// F - The function we are analyzing.
      ///
      Function *F;
  
      /// LI - The loop information for the function we are currently analyzing.
      ///
      LoopInfo *LI;
  
      /// TD - The target data information for the target we are targeting.
      ///
      TargetData *TD;
  
      /// DT - The dominator tree.
      ///
      DominatorTree *DT;
  
      /// CouldNotCompute - This SCEV is used to represent unknown trip
      /// counts and things.
      SCEVCouldNotCompute CouldNotCompute;
  
      /// ValueExprMapType - The typedef for ValueExprMap.
      ///
      typedef DenseMap<SCEVCallbackVH, const SCEV *, DenseMapInfo<Value *> >
        ValueExprMapType;
  
      /// ValueExprMap - This is a cache of the values we have analyzed so far.
      ///
      ValueExprMapType ValueExprMap;
  
      /// BackedgeTakenInfo - Information about the backedge-taken count
      /// of a loop. This currently includes an exact count and a maximum count.
      ///
      struct BackedgeTakenInfo {
        /// Exact - An expression indicating the exact backedge-taken count of
        /// the loop if it is known, or a SCEVCouldNotCompute otherwise.
        const SCEV *Exact;
  
        /// Max - An expression indicating the least maximum backedge-taken
        /// count of the loop that is known, or a SCEVCouldNotCompute.
        const SCEV *Max;
  
        /*implicit*/ BackedgeTakenInfo(const SCEV *exact) :
          Exact(exact), Max(exact) {}
  
        BackedgeTakenInfo(const SCEV *exact, const SCEV *max) :
          Exact(exact), Max(max) {}
  
        /// hasAnyInfo - Test whether this BackedgeTakenInfo contains any
        /// computed information, or whether it's all SCEVCouldNotCompute
        /// values.
        bool hasAnyInfo() const {
          return !isa<SCEVCouldNotCompute>(Exact) ||
                 !isa<SCEVCouldNotCompute>(Max);
        }
      };
  
      /// BackedgeTakenCounts - Cache the backedge-taken count of the loops for
      /// this function as they are computed.
      std::map<const Loop*, BackedgeTakenInfo> BackedgeTakenCounts;
  
      /// ConstantEvolutionLoopExitValue - This map contains entries for all of
      /// the PHI instructions that we attempt to compute constant evolutions for.
      /// This allows us to avoid potentially expensive recomputation of these
      /// properties.  An instruction maps to null if we are unable to compute its
      /// exit value.
      std::map<PHINode*, Constant*> ConstantEvolutionLoopExitValue;
  
      /// ValuesAtScopes - This map contains entries for all the expressions
      /// that we attempt to compute getSCEVAtScope information for, which can
      /// be expensive in extreme cases.
      std::map<const SCEV *,
               std::map<const Loop *, const SCEV *> > ValuesAtScopes;
  
      /// LoopDispositions - Memoized computeLoopDisposition results.
      std::map<const SCEV *,
               std::map<const Loop *, LoopDisposition> > LoopDispositions;
  
      /// computeLoopDisposition - Compute a LoopDisposition value.
      LoopDisposition computeLoopDisposition(const SCEV *S, const Loop *L);
  
      /// BlockDispositions - Memoized computeBlockDisposition results.
      std::map<const SCEV *,
               std::map<const BasicBlock *, BlockDisposition> > BlockDispositions;
  
      /// computeBlockDisposition - Compute a BlockDisposition value.
      BlockDisposition computeBlockDisposition(const SCEV *S, const BasicBlock *BB);
  
      /// UnsignedRanges - Memoized results from getUnsignedRange
      DenseMap<const SCEV *, ConstantRange> UnsignedRanges;
  
      /// SignedRanges - Memoized results from getSignedRange
      DenseMap<const SCEV *, ConstantRange> SignedRanges;
  
      /// setUnsignedRange - Set the memoized unsigned range for the given SCEV.
      const ConstantRange &setUnsignedRange(const SCEV *S,
                                            const ConstantRange &CR) {
        std::pair<DenseMap<const SCEV *, ConstantRange>::iterator, bool> Pair =
          UnsignedRanges.insert(std::make_pair(S, CR));
        if (!Pair.second)
          Pair.first->second = CR;
        return Pair.first->second;
      }
  
      /// setUnsignedRange - Set the memoized signed range for the given SCEV.
      const ConstantRange &setSignedRange(const SCEV *S,
                                          const ConstantRange &CR) {
        std::pair<DenseMap<const SCEV *, ConstantRange>::iterator, bool> Pair =
          SignedRanges.insert(std::make_pair(S, CR));
        if (!Pair.second)
          Pair.first->second = CR;
        return Pair.first->second;
      }
  
      /// createSCEV - We know that there is no SCEV for the specified value.
      /// Analyze the expression.
      const SCEV *createSCEV(Value *V);
  
      /// createNodeForPHI - Provide the special handling we need to analyze PHI
      /// SCEVs.
      const SCEV *createNodeForPHI(PHINode *PN);
  
      /// createNodeForGEP - Provide the special handling we need to analyze GEP
      /// SCEVs.
      const SCEV *createNodeForGEP(GEPOperator *GEP);
  
      /// computeSCEVAtScope - Implementation code for getSCEVAtScope; called
      /// at most once for each SCEV+Loop pair.
      ///
      const SCEV *computeSCEVAtScope(const SCEV *S, const Loop *L);
  
      /// ForgetSymbolicValue - This looks up computed SCEV values for all
      /// instructions that depend on the given instruction and removes them from
      /// the ValueExprMap map if they reference SymName. This is used during PHI
      /// resolution.
      void ForgetSymbolicName(Instruction *I, const SCEV *SymName);
  
      /// getBECount - Subtract the end and start values and divide by the step,
      /// rounding up, to get the number of times the backedge is executed. Return
      /// CouldNotCompute if an intermediate computation overflows.
      const SCEV *getBECount(const SCEV *Start,
                             const SCEV *End,
                             const SCEV *Step,
                             bool NoWrap);
  
      /// getBackedgeTakenInfo - Return the BackedgeTakenInfo for the given
      /// loop, lazily computing new values if the loop hasn't been analyzed
      /// yet.
      const BackedgeTakenInfo &getBackedgeTakenInfo(const Loop *L);
  
      /// ComputeBackedgeTakenCount - Compute the number of times the specified
      /// loop will iterate.
      BackedgeTakenInfo ComputeBackedgeTakenCount(const Loop *L);
  
      /// ComputeBackedgeTakenCountFromExit - Compute the number of times the
      /// backedge of the specified loop will execute if it exits via the
      /// specified block.
      BackedgeTakenInfo ComputeBackedgeTakenCountFromExit(const Loop *L,
                                                        BasicBlock *ExitingBlock);
  
      /// ComputeBackedgeTakenCountFromExitCond - Compute the number of times the
      /// backedge of the specified loop will execute if its exit condition
      /// were a conditional branch of ExitCond, TBB, and FBB.
      BackedgeTakenInfo
        ComputeBackedgeTakenCountFromExitCond(const Loop *L,
                                              Value *ExitCond,
                                              BasicBlock *TBB,
                                              BasicBlock *FBB);
  
      /// ComputeBackedgeTakenCountFromExitCondICmp - Compute the number of
      /// times the backedge of the specified loop will execute if its exit
      /// condition were a conditional branch of the ICmpInst ExitCond, TBB,
      /// and FBB.
      BackedgeTakenInfo
        ComputeBackedgeTakenCountFromExitCondICmp(const Loop *L,
                                                  ICmpInst *ExitCond,
                                                  BasicBlock *TBB,
                                                  BasicBlock *FBB);
  
      /// ComputeLoadConstantCompareBackedgeTakenCount - Given an exit condition
      /// of 'icmp op load X, cst', try to see if we can compute the
      /// backedge-taken count.
      BackedgeTakenInfo
        ComputeLoadConstantCompareBackedgeTakenCount(LoadInst *LI,
                                                     Constant *RHS,
                                                     const Loop *L,
                                                     ICmpInst::Predicate p);
  
      /// ComputeBackedgeTakenCountExhaustively - If the loop is known to execute
      /// a constant number of times (the condition evolves only from constants),
      /// try to evaluate a few iterations of the loop until we get the exit
      /// condition gets a value of ExitWhen (true or false).  If we cannot
      /// evaluate the backedge-taken count of the loop, return CouldNotCompute.
      const SCEV *ComputeBackedgeTakenCountExhaustively(const Loop *L,
                                                        Value *Cond,
                                                        bool ExitWhen);
  
      /// HowFarToZero - Return the number of times a backedge comparing the
      /// specified value to zero will execute.  If not computable, return
      /// CouldNotCompute.
      BackedgeTakenInfo HowFarToZero(const SCEV *V, const Loop *L);
  
      /// HowFarToNonZero - Return the number of times a backedge checking the
      /// specified value for nonzero will execute.  If not computable, return
      /// CouldNotCompute.
      BackedgeTakenInfo HowFarToNonZero(const SCEV *V, const Loop *L);
  
      /// HowManyLessThans - Return the number of times a backedge containing the
      /// specified less-than comparison will execute.  If not computable, return
      /// CouldNotCompute. isSigned specifies whether the less-than is signed.
      BackedgeTakenInfo HowManyLessThans(const SCEV *LHS, const SCEV *RHS,
                                         const Loop *L, bool isSigned);
  
      /// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB
      /// (which may not be an immediate predecessor) which has exactly one
      /// successor from which BB is reachable, or null if no such block is
      /// found.
      std::pair<BasicBlock *, BasicBlock *>
      getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB);
  
      /// isImpliedCond - Test whether the condition described by Pred, LHS, and
      /// RHS is true whenever the given FoundCondValue value evaluates to true.
      bool isImpliedCond(ICmpInst::Predicate Pred,
                         const SCEV *LHS, const SCEV *RHS,
                         Value *FoundCondValue,
                         bool Inverse);
  
      /// isImpliedCondOperands - Test whether the condition described by Pred,
      /// LHS, and RHS is true whenever the condition described by Pred, FoundLHS,
      /// and FoundRHS is true.
      bool isImpliedCondOperands(ICmpInst::Predicate Pred,
                                 const SCEV *LHS, const SCEV *RHS,
                                 const SCEV *FoundLHS, const SCEV *FoundRHS);
  
      /// isImpliedCondOperandsHelper - Test whether the condition described by
      /// Pred, LHS, and RHS is true whenever the condition described by Pred,
      /// FoundLHS, and FoundRHS is true.
      bool isImpliedCondOperandsHelper(ICmpInst::Predicate Pred,
                                       const SCEV *LHS, const SCEV *RHS,
                                       const SCEV *FoundLHS, const SCEV *FoundRHS);
  
      /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is
      /// in the header of its containing loop, we know the loop executes a
      /// constant number of times, and the PHI node is just a recurrence
      /// involving constants, fold it.
      Constant *getConstantEvolutionLoopExitValue(PHINode *PN, const APInt& BEs,
                                                  const Loop *L);
  
      /// isKnownPredicateWithRanges - Test if the given expression is known to
      /// satisfy the condition described by Pred and the known constant ranges
      /// of LHS and RHS.
      ///
      bool isKnownPredicateWithRanges(ICmpInst::Predicate Pred,
                                      const SCEV *LHS, const SCEV *RHS);
  
      /// forgetMemoizedResults - Drop memoized information computed for S.
      void forgetMemoizedResults(const SCEV *S);
  
    public:
      static char ID; // Pass identification, replacement for typeid
      ScalarEvolution();
  
      LLVMContext &getContext() const { return F->getContext(); }
  
      /// isSCEVable - Test if values of the given type are analyzable within
      /// the SCEV framework. This primarily includes integer types, and it
      /// can optionally include pointer types if the ScalarEvolution class
      /// has access to target-specific information.
      bool isSCEVable(const Type *Ty) const;
  
      /// getTypeSizeInBits - Return the size in bits of the specified type,
      /// for which isSCEVable must return true.
      uint64_t getTypeSizeInBits(const Type *Ty) const;
  
      /// getEffectiveSCEVType - Return a type with the same bitwidth as
      /// the given type and which represents how SCEV will treat the given
      /// type, for which isSCEVable must return true. For pointer types,
      /// this is the pointer-sized integer type.
      const Type *getEffectiveSCEVType(const Type *Ty) const;
  
      /// getSCEV - Return a SCEV expression for the full generality of the
      /// specified expression.
      const SCEV *getSCEV(Value *V);
  
      const SCEV *getConstant(ConstantInt *V);
      const SCEV *getConstant(const APInt& Val);
      const SCEV *getConstant(const Type *Ty, uint64_t V, bool isSigned = false);
      const SCEV *getTruncateExpr(const SCEV *Op, const Type *Ty);
      const SCEV *getZeroExtendExpr(const SCEV *Op, const Type *Ty);
      const SCEV *getSignExtendExpr(const SCEV *Op, const Type *Ty);
      const SCEV *getAnyExtendExpr(const SCEV *Op, const Type *Ty);
      const SCEV *getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
                             bool HasNUW = false, bool HasNSW = false);
      const SCEV *getAddExpr(const SCEV *LHS, const SCEV *RHS,
                             bool HasNUW = false, bool HasNSW = false) {
        SmallVector<const SCEV *, 2> Ops;
        Ops.push_back(LHS);
        Ops.push_back(RHS);
        return getAddExpr(Ops, HasNUW, HasNSW);
      }
      const SCEV *getAddExpr(const SCEV *Op0, const SCEV *Op1,
                             const SCEV *Op2,
                             bool HasNUW = false, bool HasNSW = false) {
        SmallVector<const SCEV *, 3> Ops;
        Ops.push_back(Op0);
        Ops.push_back(Op1);
        Ops.push_back(Op2);
        return getAddExpr(Ops, HasNUW, HasNSW);
      }
      const SCEV *getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
                             bool HasNUW = false, bool HasNSW = false);
      const SCEV *getMulExpr(const SCEV *LHS, const SCEV *RHS,
                             bool HasNUW = false, bool HasNSW = false) {
        SmallVector<const SCEV *, 2> Ops;
        Ops.push_back(LHS);
        Ops.push_back(RHS);
        return getMulExpr(Ops, HasNUW, HasNSW);
      }
      const SCEV *getUDivExpr(const SCEV *LHS, const SCEV *RHS);
      const SCEV *getAddRecExpr(const SCEV *Start, const SCEV *Step,
                                const Loop *L,
                                bool HasNUW = false, bool HasNSW = false);
      const SCEV *getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands,
                                const Loop *L,
                                bool HasNUW = false, bool HasNSW = false);
      const SCEV *getAddRecExpr(const SmallVectorImpl<const SCEV *> &Operands,
                                const Loop *L,
                                bool HasNUW = false, bool HasNSW = false) {
        SmallVector<const SCEV *, 4> NewOp(Operands.begin(), Operands.end());
        return getAddRecExpr(NewOp, L, HasNUW, HasNSW);
      }
      const SCEV *getSMaxExpr(const SCEV *LHS, const SCEV *RHS);
      const SCEV *getSMaxExpr(SmallVectorImpl<const SCEV *> &Operands);
      const SCEV *getUMaxExpr(const SCEV *LHS, const SCEV *RHS);
      const SCEV *getUMaxExpr(SmallVectorImpl<const SCEV *> &Operands);
      const SCEV *getSMinExpr(const SCEV *LHS, const SCEV *RHS);
      const SCEV *getUMinExpr(const SCEV *LHS, const SCEV *RHS);
      const SCEV *getUnknown(Value *V);
      const SCEV *getCouldNotCompute();
  
      /// getSizeOfExpr - Return an expression for sizeof on the given type.
      ///
      const SCEV *getSizeOfExpr(const Type *AllocTy);
  
      /// getAlignOfExpr - Return an expression for alignof on the given type.
      ///
      const SCEV *getAlignOfExpr(const Type *AllocTy);
  
      /// getOffsetOfExpr - Return an expression for offsetof on the given field.
      ///
      const SCEV *getOffsetOfExpr(const StructType *STy, unsigned FieldNo);
  
      /// getOffsetOfExpr - Return an expression for offsetof on the given field.
      ///
      const SCEV *getOffsetOfExpr(const Type *CTy, Constant *FieldNo);
  
      /// getNegativeSCEV - Return the SCEV object corresponding to -V.
      ///
      const SCEV *getNegativeSCEV(const SCEV *V);
  
      /// getNotSCEV - Return the SCEV object corresponding to ~V.
      ///
      const SCEV *getNotSCEV(const SCEV *V);
  
      /// getMinusSCEV - Return LHS-RHS.  Minus is represented in SCEV as A+B*-1,
      /// and thus the HasNUW and HasNSW bits apply to the resultant add, not
      /// whether the sub would have overflowed.
      const SCEV *getMinusSCEV(const SCEV *LHS, const SCEV *RHS,
                               bool HasNUW = false, bool HasNSW = false);
  
      /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion
      /// of the input value to the specified type.  If the type must be
      /// extended, it is zero extended.
      const SCEV *getTruncateOrZeroExtend(const SCEV *V, const Type *Ty);
  
      /// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion
      /// of the input value to the specified type.  If the type must be
      /// extended, it is sign extended.
      const SCEV *getTruncateOrSignExtend(const SCEV *V, const Type *Ty);
  
      /// getNoopOrZeroExtend - Return a SCEV corresponding to a conversion of
      /// the input value to the specified type.  If the type must be extended,
      /// it is zero extended.  The conversion must not be narrowing.
      const SCEV *getNoopOrZeroExtend(const SCEV *V, const Type *Ty);
  
      /// getNoopOrSignExtend - Return a SCEV corresponding to a conversion of
      /// the input value to the specified type.  If the type must be extended,
      /// it is sign extended.  The conversion must not be narrowing.
      const SCEV *getNoopOrSignExtend(const SCEV *V, const Type *Ty);
  
      /// getNoopOrAnyExtend - Return a SCEV corresponding to a conversion of
      /// the input value to the specified type. If the type must be extended,
      /// it is extended with unspecified bits. The conversion must not be
      /// narrowing.
      const SCEV *getNoopOrAnyExtend(const SCEV *V, const Type *Ty);
  
      /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the
      /// input value to the specified type.  The conversion must not be
      /// widening.
      const SCEV *getTruncateOrNoop(const SCEV *V, const Type *Ty);
  
      /// getUMaxFromMismatchedTypes - Promote the operands to the wider of
      /// the types using zero-extension, and then perform a umax operation
      /// with them.
      const SCEV *getUMaxFromMismatchedTypes(const SCEV *LHS,
                                             const SCEV *RHS);
  
      /// getUMinFromMismatchedTypes - Promote the operands to the wider of
      /// the types using zero-extension, and then perform a umin operation
      /// with them.
      const SCEV *getUMinFromMismatchedTypes(const SCEV *LHS,
                                             const SCEV *RHS);
  
      /// getSCEVAtScope - Return a SCEV expression for the specified value
      /// at the specified scope in the program.  The L value specifies a loop
      /// nest to evaluate the expression at, where null is the top-level or a
      /// specified loop is immediately inside of the loop.
      ///
      /// This method can be used to compute the exit value for a variable defined
      /// in a loop by querying what the value will hold in the parent loop.
      ///
      /// In the case that a relevant loop exit value cannot be computed, the
      /// original value V is returned.
      const SCEV *getSCEVAtScope(const SCEV *S, const Loop *L);
  
      /// getSCEVAtScope - This is a convenience function which does
      /// getSCEVAtScope(getSCEV(V), L).
      const SCEV *getSCEVAtScope(Value *V, const Loop *L);
  
      /// isLoopEntryGuardedByCond - Test whether entry to the loop is protected
      /// by a conditional between LHS and RHS.  This is used to help avoid max
      /// expressions in loop trip counts, and to eliminate casts.
      bool isLoopEntryGuardedByCond(const Loop *L, ICmpInst::Predicate Pred,
                                    const SCEV *LHS, const SCEV *RHS);
  
      /// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is
      /// protected by a conditional between LHS and RHS.  This is used to
      /// to eliminate casts.
      bool isLoopBackedgeGuardedByCond(const Loop *L, ICmpInst::Predicate Pred,
                                       const SCEV *LHS, const SCEV *RHS);
  
      /// getBackedgeTakenCount - If the specified loop has a predictable
      /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute
      /// object. The backedge-taken count is the number of times the loop header
      /// will be branched to from within the loop. This is one less than the
      /// trip count of the loop, since it doesn't count the first iteration,
      /// when the header is branched to from outside the loop.
      ///
      /// Note that it is not valid to call this method on a loop without a
      /// loop-invariant backedge-taken count (see
      /// hasLoopInvariantBackedgeTakenCount).
      ///
      const SCEV *getBackedgeTakenCount(const Loop *L);
  
      /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except
      /// return the least SCEV value that is known never to be less than the
      /// actual backedge taken count.
      const SCEV *getMaxBackedgeTakenCount(const Loop *L);
  
      /// hasLoopInvariantBackedgeTakenCount - Return true if the specified loop
      /// has an analyzable loop-invariant backedge-taken count.
      bool hasLoopInvariantBackedgeTakenCount(const Loop *L);
  
      /// forgetLoop - This method should be called by the client when it has
      /// changed a loop in a way that may effect ScalarEvolution's ability to
      /// compute a trip count, or if the loop is deleted.
      void forgetLoop(const Loop *L);
  
      /// forgetValue - This method should be called by the client when it has
      /// changed a value in a way that may effect its value, or which may
      /// disconnect it from a def-use chain linking it to a loop.
      void forgetValue(Value *V);
  
      /// GetMinTrailingZeros - Determine the minimum number of zero bits that S
      /// is guaranteed to end in (at every loop iteration).  It is, at the same
      /// time, the minimum number of times S is divisible by 2.  For example,
      /// given {4,+,8} it returns 2.  If S is guaranteed to be 0, it returns the
      /// bitwidth of S.
      uint32_t GetMinTrailingZeros(const SCEV *S);
  
      /// getUnsignedRange - Determine the unsigned range for a particular SCEV.
      ///
      ConstantRange getUnsignedRange(const SCEV *S);
  
      /// getSignedRange - Determine the signed range for a particular SCEV.
      ///
      ConstantRange getSignedRange(const SCEV *S);
  
      /// isKnownNegative - Test if the given expression is known to be negative.
      ///
      bool isKnownNegative(const SCEV *S);
  
      /// isKnownPositive - Test if the given expression is known to be positive.
      ///
      bool isKnownPositive(const SCEV *S);
  
      /// isKnownNonNegative - Test if the given expression is known to be
      /// non-negative.
      ///
      bool isKnownNonNegative(const SCEV *S);
  
      /// isKnownNonPositive - Test if the given expression is known to be
      /// non-positive.
      ///
      bool isKnownNonPositive(const SCEV *S);
  
      /// isKnownNonZero - Test if the given expression is known to be
      /// non-zero.
      ///
      bool isKnownNonZero(const SCEV *S);
  
      /// isKnownPredicate - Test if the given expression is known to satisfy
      /// the condition described by Pred, LHS, and RHS.
      ///
      bool isKnownPredicate(ICmpInst::Predicate Pred,
                            const SCEV *LHS, const SCEV *RHS);
  
      /// SimplifyICmpOperands - Simplify LHS and RHS in a comparison with
      /// predicate Pred. Return true iff any changes were made. If the
      /// operands are provably equal or inequal, LHS and RHS are set to
      /// the same value and Pred is set to either ICMP_EQ or ICMP_NE.
      ///
      bool SimplifyICmpOperands(ICmpInst::Predicate &Pred,
                                const SCEV *&LHS,
                                const SCEV *&RHS);
  
      /// getLoopDisposition - Return the "disposition" of the given SCEV with
      /// respect to the given loop.
      LoopDisposition getLoopDisposition(const SCEV *S, const Loop *L);
  
      /// isLoopInvariant - Return true if the value of the given SCEV is
      /// unchanging in the specified loop.
      bool isLoopInvariant(const SCEV *S, const Loop *L);
  
      /// hasComputableLoopEvolution - Return true if the given SCEV changes value
      /// in a known way in the specified loop.  This property being true implies
      /// that the value is variant in the loop AND that we can emit an expression
      /// to compute the value of the expression at any particular loop iteration.
      bool hasComputableLoopEvolution(const SCEV *S, const Loop *L);
  
      /// getLoopDisposition - Return the "disposition" of the given SCEV with
      /// respect to the given block.
      BlockDisposition getBlockDisposition(const SCEV *S, const BasicBlock *BB);
  
      /// dominates - Return true if elements that makes up the given SCEV
      /// dominate the specified basic block.
      bool dominates(const SCEV *S, const BasicBlock *BB);
  
      /// properlyDominates - Return true if elements that makes up the given SCEV
      /// properly dominate the specified basic block.
      bool properlyDominates(const SCEV *S, const BasicBlock *BB);
  
      /// hasOperand - Test whether the given SCEV has Op as a direct or
      /// indirect operand.
      bool hasOperand(const SCEV *S, const SCEV *Op) const;
  
      virtual bool runOnFunction(Function &F);
      virtual void releaseMemory();
      virtual void getAnalysisUsage(AnalysisUsage &AU) const;
      virtual void print(raw_ostream &OS, const Module* = 0) const;
  
    private:
      FoldingSet<SCEV> UniqueSCEVs;
      BumpPtrAllocator SCEVAllocator;
  
      /// FirstUnknown - The head of a linked list of all SCEVUnknown
      /// values that have been allocated. This is used by releaseMemory
      /// to locate them all and call their destructors.
      SCEVUnknown *FirstUnknown;
    };
  }
  
  #endif
  