ScalarEvolutionExpressions.h

//===- llvm/Analysis/ScalarEvolutionExpressions.h - SCEV Exprs --*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the classes used to represent and build scalar expressions.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_ANALYSIS_SCALAREVOLUTION_EXPRESSIONS_H
#define LLVM_ANALYSIS_SCALAREVOLUTION_EXPRESSIONS_H

#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Support/ErrorHandling.h"

namespace llvm {
  class ConstantInt;
  class ConstantRange;
  class DominatorTree;

  enum SCEVTypes {
    // These should be ordered in terms of increasing complexity to make the
    // folders simpler.
    scConstant, scTruncate, scZeroExtend, scSignExtend, scAddExpr, scMulExpr,
    scUDivExpr, scAddRecExpr, scUMaxExpr, scSMaxExpr,
    scUnknown, scCouldNotCompute
  };

  //===--------------------------------------------------------------------===//
  class SCEVConstant : public SCEV {
    friend class ScalarEvolution;

    ConstantInt *V;
    SCEVConstant(const FoldingSetNodeIDRef ID, ConstantInt *v) :
      SCEV(ID, scConstant), V(v) {}
  public:
    ConstantInt *getValue() const { return V; }

    virtual bool isLoopInvariant(const Loop *L) const {
      return true;
    }

    virtual bool hasComputableLoopEvolution(const Loop *L) const {
      return false;  // Not loop variant
    }

    virtual const Type *getType() const;

    virtual bool hasOperand(const SCEV *) const {
      return false;
    }

    bool dominates(BasicBlock *BB, DominatorTree *DT) const {
      return true;
    }

    bool properlyDominates(BasicBlock *BB, DominatorTree *DT) const {
      return true;
    }

    virtual void print(raw_ostream &OS) const;

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

  //===--------------------------------------------------------------------===//
  class SCEVCastExpr : public SCEV {
  protected:
    const SCEV *Op;
    const Type *Ty;

    SCEVCastExpr(const FoldingSetNodeIDRef ID,
                 unsigned SCEVTy, const SCEV *op, const Type *ty);

  public:
    const SCEV *getOperand() const { return Op; }
    virtual const Type *getType() const { return Ty; }

    virtual bool isLoopInvariant(const Loop *L) const {
      return Op->isLoopInvariant(L);
    }

    virtual bool hasComputableLoopEvolution(const Loop *L) const {
      return Op->hasComputableLoopEvolution(L);
    }

    virtual bool hasOperand(const SCEV *O) const {
      return Op == O || Op->hasOperand(O);
    }

    virtual bool dominates(BasicBlock *BB, DominatorTree *DT) const;

    virtual bool properlyDominates(BasicBlock *BB, DominatorTree *DT) const;

    static inline bool classof(const SCEVCastExpr *S) { return true; }
    static inline bool classof(const SCEV *S) {
      return S->getSCEVType() == scTruncate ||
             S->getSCEVType() == scZeroExtend ||
             S->getSCEVType() == scSignExtend;
    }
  };

  //===--------------------------------------------------------------------===//
  class SCEVTruncateExpr : public SCEVCastExpr {
    friend class ScalarEvolution;

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

  public:
    virtual void print(raw_ostream &OS) const;

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

  //===--------------------------------------------------------------------===//
  class SCEVZeroExtendExpr : public SCEVCastExpr {
    friend class ScalarEvolution;

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

  public:
    virtual void print(raw_ostream &OS) const;

    static inline bool classof(const SCEVZeroExtendExpr *S) { return true; }
    static inline bool classof(const SCEV *S) {
      return S->getSCEVType() == scZeroExtend;
    }
  };

  //===--------------------------------------------------------------------===//
  class SCEVSignExtendExpr : public SCEVCastExpr {
    friend class ScalarEvolution;

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

  public:
    virtual void print(raw_ostream &OS) const;

    static inline bool classof(const SCEVSignExtendExpr *S) { return true; }
    static inline bool classof(const SCEV *S) {
      return S->getSCEVType() == scSignExtend;
    }
  };


  //===--------------------------------------------------------------------===//
  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), 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];
    }

    typedef const SCEV *const *op_iterator;
    op_iterator op_begin() const { return Operands; }
    op_iterator op_end() const { return Operands + NumOperands; }

    virtual bool isLoopInvariant(const Loop *L) const {
      for (unsigned i = 0, e = getNumOperands(); i != e; ++i)
        if (!getOperand(i)->isLoopInvariant(L)) return false;
      return true;
    }

    // hasComputableLoopEvolution - N-ary expressions have computable loop
    // evolutions iff they have at least one operand that varies with the loop,
    // but that all varying operands are computable.
    virtual bool hasComputableLoopEvolution(const Loop *L) const {
      bool HasVarying = false;
      for (unsigned i = 0, e = getNumOperands(); i != e; ++i)
        if (!getOperand(i)->isLoopInvariant(L)) {
          if (getOperand(i)->hasComputableLoopEvolution(L))
            HasVarying = true;
          else
            return false;
        }
      return HasVarying;
    }

    virtual bool hasOperand(const SCEV *O) const {
      for (unsigned i = 0, e = getNumOperands(); i != e; ++i)
        if (O == getOperand(i) || getOperand(i)->hasOperand(O))
          return true;
      return false;
    }

    bool dominates(BasicBlock *BB, DominatorTree *DT) const;

    bool properlyDominates(BasicBlock *BB, DominatorTree *DT) const;

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

    bool hasNoUnsignedWrap() const { return SubclassData & (1 << 0); }
    void setHasNoUnsignedWrap(bool B) {
      SubclassData = (SubclassData & ~(1 << 0)) | (B << 0);
    }
    bool hasNoSignedWrap() const { return SubclassData & (1 << 1); }
    void setHasNoSignedWrap(bool B) {
      SubclassData = (SubclassData & ~(1 << 1)) | (B << 1);
    }

    static inline bool classof(const SCEVNAryExpr *S) { return true; }
    static inline bool classof(const SCEV *S) {
      return S->getSCEVType() == scAddExpr ||
             S->getSCEVType() == scMulExpr ||
             S->getSCEVType() == scSMaxExpr ||
             S->getSCEVType() == scUMaxExpr ||
             S->getSCEVType() == scAddRecExpr;
    }
  };

  //===--------------------------------------------------------------------===//
  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:
    virtual const char *getOperationStr() const = 0;

    virtual void print(raw_ostream &OS) const;

    static inline bool classof(const SCEVCommutativeExpr *S) { return true; }
    static inline bool classof(const SCEV *S) {
      return S->getSCEVType() == scAddExpr ||
             S->getSCEVType() == scMulExpr ||
             S->getSCEVType() == scSMaxExpr ||
             S->getSCEVType() == scUMaxExpr;
    }
  };


  //===--------------------------------------------------------------------===//
  class SCEVAddExpr : public SCEVCommutativeExpr {
    friend class ScalarEvolution;

    SCEVAddExpr(const FoldingSetNodeIDRef ID,
                const SCEV *const *O, size_t N)
      : SCEVCommutativeExpr(ID, scAddExpr, O, N) {
    }

  public:
    virtual const char *getOperationStr() const { return " + "; }

    virtual const Type *getType() const {
      // Use the type of the last operand, which is likely to be a pointer
      // type, if there is one. This doesn't usually matter, but it can help
      // reduce casts when the expressions are expanded.
      return getOperand(getNumOperands() - 1)->getType();
    }

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

  //===--------------------------------------------------------------------===//
  class SCEVMulExpr : public SCEVCommutativeExpr {
    friend class ScalarEvolution;

    SCEVMulExpr(const FoldingSetNodeIDRef ID,
                const SCEV *const *O, size_t N)
      : SCEVCommutativeExpr(ID, scMulExpr, O, N) {
    }

  public:
    virtual const char *getOperationStr() const { return " * "; }

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


  //===--------------------------------------------------------------------===//
  class SCEVUDivExpr : public SCEV {
    friend class ScalarEvolution;

    const SCEV *LHS;
    const SCEV *RHS;
    SCEVUDivExpr(const FoldingSetNodeIDRef ID, const SCEV *lhs, const SCEV *rhs)
      : SCEV(ID, scUDivExpr), LHS(lhs), RHS(rhs) {}

  public:
    const SCEV *getLHS() const { return LHS; }
    const SCEV *getRHS() const { return RHS; }

    virtual bool isLoopInvariant(const Loop *L) const {
      return LHS->isLoopInvariant(L) && RHS->isLoopInvariant(L);
    }

    virtual bool hasComputableLoopEvolution(const Loop *L) const {
      return LHS->hasComputableLoopEvolution(L) &&
             RHS->hasComputableLoopEvolution(L);
    }

    virtual bool hasOperand(const SCEV *O) const {
      return O == LHS || O == RHS || LHS->hasOperand(O) || RHS->hasOperand(O);
    }

    bool dominates(BasicBlock *BB, DominatorTree *DT) const;

    bool properlyDominates(BasicBlock *BB, DominatorTree *DT) const;

    virtual const Type *getType() const;

    void print(raw_ostream &OS) const;

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


  //===--------------------------------------------------------------------===//
  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) {
      for (size_t i = 0, e = NumOperands; i != e; ++i)
        assert(Operands[i]->isLoopInvariant(l) &&
               "Operands of AddRec must be loop-invariant!");
    }

  public:
    const SCEV *getStart() const { return Operands[0]; }
    const Loop *getLoop() const { return L; }

    const SCEV *getStepRecurrence(ScalarEvolution &SE) const {
      if (isAffine()) return getOperand(1);
      return SE.getAddRecExpr(SmallVector<const SCEV *, 3>(op_begin()+1,
                                                           op_end()),
                              getLoop());
    }

    virtual bool hasComputableLoopEvolution(const Loop *QL) const {
      return L == QL;
    }

    virtual bool isLoopInvariant(const Loop *QueryLoop) const;

    bool dominates(BasicBlock *BB, DominatorTree *DT) const;

    bool properlyDominates(BasicBlock *BB, DominatorTree *DT) const;

    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;
    }

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

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

    const SCEV *getNumIterationsInRange(ConstantRange Range,
                                       ScalarEvolution &SE) const;

    const SCEVAddRecExpr *getPostIncExpr(ScalarEvolution &SE) const {
      return cast<SCEVAddRecExpr>(SE.getAddExpr(this, getStepRecurrence(SE)));
    }

    virtual void print(raw_ostream &OS) const;

    static inline bool classof(const SCEVAddRecExpr *S) { return true; }
    static inline bool classof(const SCEV *S) {
      return S->getSCEVType() == scAddRecExpr;
    }
  };


  //===--------------------------------------------------------------------===//
  class SCEVSMaxExpr : public SCEVCommutativeExpr {
    friend class ScalarEvolution;

    SCEVSMaxExpr(const FoldingSetNodeIDRef ID,
                 const SCEV *const *O, size_t N)
      : SCEVCommutativeExpr(ID, scSMaxExpr, O, N) {
      // Max never overflows.
      setHasNoUnsignedWrap(true);
      setHasNoSignedWrap(true);
    }

  public:
    virtual const char *getOperationStr() const { return " smax "; }

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


  //===--------------------------------------------------------------------===//
  class SCEVUMaxExpr : public SCEVCommutativeExpr {
    friend class ScalarEvolution;

    SCEVUMaxExpr(const FoldingSetNodeIDRef ID,
                 const SCEV *const *O, size_t N)
      : SCEVCommutativeExpr(ID, scUMaxExpr, O, N) {
      // Max never overflows.
      setHasNoUnsignedWrap(true);
      setHasNoSignedWrap(true);
    }

  public:
    virtual const char *getOperationStr() const { return " umax "; }

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

  //===--------------------------------------------------------------------===//
  class SCEVUnknown : public SCEV {
    friend class ScalarEvolution;

    Value *V;
    SCEVUnknown(const FoldingSetNodeIDRef ID, Value *v) :
      SCEV(ID, scUnknown), V(v) {}

  public:
    Value *getValue() const { return V; }

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

    virtual bool isLoopInvariant(const Loop *L) const;
    virtual bool hasComputableLoopEvolution(const Loop *QL) const {
      return false; // not computable
    }

    virtual bool hasOperand(const SCEV *) const {
      return false;
    }

    bool dominates(BasicBlock *BB, DominatorTree *DT) const;

    bool properlyDominates(BasicBlock *BB, DominatorTree *DT) const;

    virtual const Type *getType() const;

    virtual void print(raw_ostream &OS) const;

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

  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 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 scUnknown:
        return ((SC*)this)->visitUnknown((const SCEVUnknown*)S);
      case scCouldNotCompute:
        return ((SC*)this)->visitCouldNotCompute((const SCEVCouldNotCompute*)S);
      default:
        llvm_unreachable("Unknown SCEV type!");
      }
    }

    RetVal visitCouldNotCompute(const SCEVCouldNotCompute *S) {
      llvm_unreachable("Invalid use of SCEVCouldNotCompute!");
      return RetVal();
    }
  };
}

#endif

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