ExprBuilder.cpp

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//===-- ExprBuilder.cpp ---------------------------------------------------===//
//
//                     The KLEE Symbolic Virtual Machine
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
 
#include "klee/Expr/ExprBuilder.h"
 
using namespace klee;
 
ExprBuilder::ExprBuilder() {
}
 
ExprBuilder::~ExprBuilder() {
}
 
namespace {
  class DefaultExprBuilder : public ExprBuilder {
    virtual ref<Expr> Constant(const llvm::APInt &Value) {
      return ConstantExpr::alloc(Value);
    }
 
    virtual ref<Expr> NotOptimized(const ref<Expr> &Index) {
      return NotOptimizedExpr::alloc(Index);
    }
 
    virtual ref<Expr> Read(const UpdateList &Updates,
                           const ref<Expr> &Index) {
      return ReadExpr::alloc(Updates, Index);
    }
 
    virtual ref<Expr> Select(const ref<Expr> &Cond,
                             const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return SelectExpr::alloc(Cond, LHS, RHS);
    }
 
    virtual ref<Expr> Concat(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return ConcatExpr::alloc(LHS, RHS);
    }
 
    virtual ref<Expr> Extract(const ref<Expr> &LHS,
                              unsigned Offset, Expr::Width W) {
      return ExtractExpr::alloc(LHS, Offset, W);
    }
 
    virtual ref<Expr> ZExt(const ref<Expr> &LHS, Expr::Width W) {
      return ZExtExpr::alloc(LHS, W);
    }
 
    virtual ref<Expr> SExt(const ref<Expr> &LHS, Expr::Width W) {
      return SExtExpr::alloc(LHS, W);
    }
 
    virtual ref<Expr> Add(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return AddExpr::alloc(LHS, RHS);
    }
 
    virtual ref<Expr> Sub(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return SubExpr::alloc(LHS, RHS);
    }
 
    virtual ref<Expr> Mul(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return MulExpr::alloc(LHS, RHS);
    }
 
    virtual ref<Expr> UDiv(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return UDivExpr::alloc(LHS, RHS);
    }
 
    virtual ref<Expr> SDiv(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return SDivExpr::alloc(LHS, RHS);
    }
 
    virtual ref<Expr> URem(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return URemExpr::alloc(LHS, RHS);
    }
 
    virtual ref<Expr> SRem(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return SRemExpr::alloc(LHS, RHS);
    }
 
    virtual ref<Expr> Not(const ref<Expr> &LHS) {
      return NotExpr::alloc(LHS);
    }
 
    virtual ref<Expr> And(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return AndExpr::alloc(LHS, RHS);
    }
 
    virtual ref<Expr> Or(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return OrExpr::alloc(LHS, RHS);
    }
 
    virtual ref<Expr> Xor(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return XorExpr::alloc(LHS, RHS);
    }
 
    virtual ref<Expr> Shl(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return ShlExpr::alloc(LHS, RHS);
    }
 
    virtual ref<Expr> LShr(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return LShrExpr::alloc(LHS, RHS);
    }
 
    virtual ref<Expr> AShr(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return AShrExpr::alloc(LHS, RHS);
    }
 
    virtual ref<Expr> Eq(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return EqExpr::alloc(LHS, RHS);
    }
 
    virtual ref<Expr> Ne(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return NeExpr::alloc(LHS, RHS);
    }
 
    virtual ref<Expr> Ult(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return UltExpr::alloc(LHS, RHS);
    }
 
    virtual ref<Expr> Ule(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return UleExpr::alloc(LHS, RHS);
    }
 
    virtual ref<Expr> Ugt(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return UgtExpr::alloc(LHS, RHS);
    }
 
    virtual ref<Expr> Uge(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return UgeExpr::alloc(LHS, RHS);
    }
 
    virtual ref<Expr> Slt(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return SltExpr::alloc(LHS, RHS);
    }
 
    virtual ref<Expr> Sle(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return SleExpr::alloc(LHS, RHS);
    }
 
    virtual ref<Expr> Sgt(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return SgtExpr::alloc(LHS, RHS);
    }
 
    virtual ref<Expr> Sge(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return SgeExpr::alloc(LHS, RHS);
    }
  };
 
  class ChainedBuilder {
  protected:
    ExprBuilder *Builder;
 
    ExprBuilder *Base;
 
  public:
    ChainedBuilder(ExprBuilder *_Builder, ExprBuilder *_Base) 
      : Builder(_Builder), Base(_Base) {}
    ~ChainedBuilder() { delete Base; }
 
    ref<Expr> Constant(const llvm::APInt &Value) {
      return Base->Constant(Value);
    }
 
    ref<Expr> NotOptimized(const ref<Expr> &Index) {
      return Base->NotOptimized(Index);
    }
 
    ref<Expr> Read(const UpdateList &Updates,
                   const ref<Expr> &Index) {
      return Base->Read(Updates, Index);
    }
 
    ref<Expr> Select(const ref<Expr> &Cond,
                     const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return Base->Select(Cond, LHS, RHS);
    }
 
    ref<Expr> Concat(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return Base->Concat(LHS, RHS);
    }
 
    ref<Expr> Extract(const ref<Expr> &LHS,
                      unsigned Offset, Expr::Width W) {
      return Base->Extract(LHS, Offset, W);
    }
 
    ref<Expr> ZExt(const ref<Expr> &LHS, Expr::Width W) {
      return Base->ZExt(LHS, W);
    }
 
    ref<Expr> SExt(const ref<Expr> &LHS, Expr::Width W) {
      return Base->SExt(LHS, W);
    }
 
    ref<Expr> Add(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return Base->Add(LHS, RHS);
    }
 
    ref<Expr> Sub(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return Base->Sub(LHS, RHS);
    }
 
    ref<Expr> Mul(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return Base->Mul(LHS, RHS);
    }
 
    ref<Expr> UDiv(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return Base->UDiv(LHS, RHS);
    }
 
    ref<Expr> SDiv(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return Base->SDiv(LHS, RHS);
    }
 
    ref<Expr> URem(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return Base->URem(LHS, RHS);
    }
 
    ref<Expr> SRem(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return Base->SRem(LHS, RHS);
    }
 
    ref<Expr> Not(const ref<Expr> &LHS) {
      return Base->Not(LHS);
    }
 
    ref<Expr> And(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return Base->And(LHS, RHS);
    }
 
    ref<Expr> Or(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return Base->Or(LHS, RHS);
    }
 
    ref<Expr> Xor(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return Base->Xor(LHS, RHS);
    }
 
    ref<Expr> Shl(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return Base->Shl(LHS, RHS);
    }
 
    ref<Expr> LShr(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return Base->LShr(LHS, RHS);
    }
 
    ref<Expr> AShr(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return Base->AShr(LHS, RHS);
    }
 
    ref<Expr> Eq(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return Base->Eq(LHS, RHS);
    }
 
    ref<Expr> Ne(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return Base->Ne(LHS, RHS);
    }
 
    ref<Expr> Ult(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return Base->Ult(LHS, RHS);
    }
 
    ref<Expr> Ule(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return Base->Ule(LHS, RHS);
    }
 
    ref<Expr> Ugt(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return Base->Ugt(LHS, RHS);
    }
 
    ref<Expr> Uge(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return Base->Uge(LHS, RHS);
    }
 
    ref<Expr> Slt(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return Base->Slt(LHS, RHS);
    }
 
    ref<Expr> Sle(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return Base->Sle(LHS, RHS);
    }
 
    ref<Expr> Sgt(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return Base->Sgt(LHS, RHS);
    }
 
    ref<Expr> Sge(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      return Base->Sge(LHS, RHS);
    }
  };
 
  template<typename SpecializedBuilder>
  class ConstantSpecializedExprBuilder : public ExprBuilder {
    SpecializedBuilder Builder;
 
  public:
    ConstantSpecializedExprBuilder(ExprBuilder *Base) : Builder(this, Base) {}
    ~ConstantSpecializedExprBuilder() {}
 
    virtual ref<Expr> Constant(const llvm::APInt &Value) {
      return Builder.Constant(Value);
    }
 
    virtual ref<Expr> NotOptimized(const ref<Expr> &Index) {
      return Builder.NotOptimized(Index);
    }
 
    virtual ref<Expr> Read(const UpdateList &Updates,
                           const ref<Expr> &Index) {
      // Roll back through writes when possible.
      auto UN = Updates.head;
      while (UN && Eq(Index, UN->index)->isFalse())
        UN = UN->next;
 
      if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Index))
        return Builder.Read(UpdateList(Updates.root, UN), CE);
 
      return Builder.Read(UpdateList(Updates.root, UN), Index);
    }
 
    virtual ref<Expr> Select(const ref<Expr> &Cond,
                             const ref<Expr> &LHS, const ref<Expr> &RHS) {
      if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Cond))
        return CE->isTrue() ? LHS : RHS;
 
      return Builder.Select(cast<NonConstantExpr>(Cond), LHS, RHS);
    }
 
    virtual ref<Expr> Concat(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      if (ConstantExpr *LCE = dyn_cast<ConstantExpr>(LHS)) {
        if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS))
          return LCE->Concat(RCE);
        return Builder.Concat(LCE, cast<NonConstantExpr>(RHS));
      } else if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS)) {
        return Builder.Concat(cast<NonConstantExpr>(LHS), RCE);
      }
 
      return Builder.Concat(cast<NonConstantExpr>(LHS),
                            cast<NonConstantExpr>(RHS));
    }
 
    virtual ref<Expr> Extract(const ref<Expr> &LHS,
                              unsigned Offset, Expr::Width W) {
      if (ConstantExpr *CE = dyn_cast<ConstantExpr>(LHS))
        return CE->Extract(Offset, W);
 
      return Builder.Extract(cast<NonConstantExpr>(LHS), Offset, W);
    }
 
    virtual ref<Expr> ZExt(const ref<Expr> &LHS, Expr::Width W) {
      if (ConstantExpr *CE = dyn_cast<ConstantExpr>(LHS))
        return CE->ZExt(W);
 
      return Builder.ZExt(cast<NonConstantExpr>(LHS), W);
    }
 
    virtual ref<Expr> SExt(const ref<Expr> &LHS, Expr::Width W) {
      if (ConstantExpr *CE = dyn_cast<ConstantExpr>(LHS))
        return CE->SExt(W);
 
      return Builder.SExt(cast<NonConstantExpr>(LHS), W);
    }
 
    virtual ref<Expr> Add(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      if (ConstantExpr *LCE = dyn_cast<ConstantExpr>(LHS)) {
        if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS))
          return LCE->Add(RCE);
        return Builder.Add(LCE, cast<NonConstantExpr>(RHS));
      } else if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS)) {
        return Builder.Add(cast<NonConstantExpr>(LHS), RCE);
      }
 
      return Builder.Add(cast<NonConstantExpr>(LHS),
                         cast<NonConstantExpr>(RHS));
    }
 
    virtual ref<Expr> Sub(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      if (ConstantExpr *LCE = dyn_cast<ConstantExpr>(LHS)) {
        if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS))
          return LCE->Sub(RCE);
        return Builder.Sub(LCE, cast<NonConstantExpr>(RHS));
      } else if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS)) {
        return Builder.Sub(cast<NonConstantExpr>(LHS), RCE);
      }
 
      return Builder.Sub(cast<NonConstantExpr>(LHS),
                         cast<NonConstantExpr>(RHS));
    }
 
    virtual ref<Expr> Mul(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      if (ConstantExpr *LCE = dyn_cast<ConstantExpr>(LHS)) {
        if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS))
          return LCE->Mul(RCE);
        return Builder.Mul(LCE, cast<NonConstantExpr>(RHS));
      } else if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS)) {
        return Builder.Mul(cast<NonConstantExpr>(LHS), RCE);
      }
 
      return Builder.Mul(cast<NonConstantExpr>(LHS),
                         cast<NonConstantExpr>(RHS));
    }
 
    virtual ref<Expr> UDiv(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      if (ConstantExpr *LCE = dyn_cast<ConstantExpr>(LHS)) {
        if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS))
          return LCE->UDiv(RCE);
        return Builder.UDiv(LCE, cast<NonConstantExpr>(RHS));
      } else if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS)) {
        return Builder.UDiv(cast<NonConstantExpr>(LHS), RCE);
      }
 
      return Builder.UDiv(cast<NonConstantExpr>(LHS),
                          cast<NonConstantExpr>(RHS));
    }
 
    virtual ref<Expr> SDiv(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      if (ConstantExpr *LCE = dyn_cast<ConstantExpr>(LHS)) {
        if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS))
          return LCE->SDiv(RCE);
        return Builder.SDiv(LCE, cast<NonConstantExpr>(RHS));
      } else if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS)) {
        return Builder.SDiv(cast<NonConstantExpr>(LHS), RCE);
      }
 
      return Builder.SDiv(cast<NonConstantExpr>(LHS),
                          cast<NonConstantExpr>(RHS));
    }
 
    virtual ref<Expr> URem(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      if (ConstantExpr *LCE = dyn_cast<ConstantExpr>(LHS)) {
        if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS))
          return LCE->URem(RCE);
        return Builder.URem(LCE, cast<NonConstantExpr>(RHS));
      } else if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS)) {
        return Builder.URem(cast<NonConstantExpr>(LHS), RCE);
      }
 
      return Builder.URem(cast<NonConstantExpr>(LHS),
                          cast<NonConstantExpr>(RHS));
    }
 
    virtual ref<Expr> SRem(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      if (ConstantExpr *LCE = dyn_cast<ConstantExpr>(LHS)) {
        if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS))
          return LCE->SRem(RCE);
        return Builder.SRem(LCE, cast<NonConstantExpr>(RHS));
      } else if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS)) {
        return Builder.SRem(cast<NonConstantExpr>(LHS), RCE);
      }
 
      return Builder.SRem(cast<NonConstantExpr>(LHS),
                          cast<NonConstantExpr>(RHS));
    }
 
    virtual ref<Expr> Not(const ref<Expr> &LHS) {
      // !!X ==> X
      if (NotExpr *DblNot = dyn_cast<NotExpr>(LHS))
        return DblNot->getKid(0);
 
      if (ConstantExpr *CE = dyn_cast<ConstantExpr>(LHS))
        return CE->Not();
 
      return Builder.Not(cast<NonConstantExpr>(LHS));
    }
 
    virtual ref<Expr> And(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      if (ConstantExpr *LCE = dyn_cast<ConstantExpr>(LHS)) {
        if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS))
          return LCE->And(RCE);
        return Builder.And(LCE, cast<NonConstantExpr>(RHS));
      } else if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS)) {
        return Builder.And(cast<NonConstantExpr>(LHS), RCE);
      }
 
      return Builder.And(cast<NonConstantExpr>(LHS),
                         cast<NonConstantExpr>(RHS));
    }
 
    virtual ref<Expr> Or(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      if (ConstantExpr *LCE = dyn_cast<ConstantExpr>(LHS)) {
        if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS))
          return LCE->Or(RCE);
        return Builder.Or(LCE, cast<NonConstantExpr>(RHS));
      } else if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS)) {
        return Builder.Or(cast<NonConstantExpr>(LHS), RCE);
      }
 
      return Builder.Or(cast<NonConstantExpr>(LHS),
                        cast<NonConstantExpr>(RHS));
    }
 
    virtual ref<Expr> Xor(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      if (ConstantExpr *LCE = dyn_cast<ConstantExpr>(LHS)) {
        if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS))
          return LCE->Xor(RCE);
        return Builder.Xor(LCE, cast<NonConstantExpr>(RHS));
      } else if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS)) {
        return Builder.Xor(cast<NonConstantExpr>(LHS), RCE);
      }
 
      return Builder.Xor(cast<NonConstantExpr>(LHS),
                         cast<NonConstantExpr>(RHS));
    }
 
    virtual ref<Expr> Shl(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      if (ConstantExpr *LCE = dyn_cast<ConstantExpr>(LHS)) {
        if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS))
          return LCE->Shl(RCE);
        return Builder.Shl(LCE, cast<NonConstantExpr>(RHS));
      } else if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS)) {
        return Builder.Shl(cast<NonConstantExpr>(LHS), RCE);
      }
 
      return Builder.Shl(cast<NonConstantExpr>(LHS),
                         cast<NonConstantExpr>(RHS));
    }
 
    virtual ref<Expr> LShr(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      if (ConstantExpr *LCE = dyn_cast<ConstantExpr>(LHS)) {
        if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS))
          return LCE->LShr(RCE);
        return Builder.LShr(LCE, cast<NonConstantExpr>(RHS));
      } else if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS)) {
        return Builder.LShr(cast<NonConstantExpr>(LHS), RCE);
      }
 
      return Builder.LShr(cast<NonConstantExpr>(LHS),
                          cast<NonConstantExpr>(RHS));
    }
 
    virtual ref<Expr> AShr(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      if (ConstantExpr *LCE = dyn_cast<ConstantExpr>(LHS)) {
        if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS))
          return LCE->AShr(RCE);
        return Builder.AShr(LCE, cast<NonConstantExpr>(RHS));
      } else if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS)) {
        return Builder.AShr(cast<NonConstantExpr>(LHS), RCE);
      }
 
      return Builder.AShr(cast<NonConstantExpr>(LHS),
                          cast<NonConstantExpr>(RHS));
    }
 
    virtual ref<Expr> Eq(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      if (ConstantExpr *LCE = dyn_cast<ConstantExpr>(LHS)) {
        if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS))
          return LCE->Eq(RCE);
        return Builder.Eq(LCE, cast<NonConstantExpr>(RHS));
      } else if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS)) {
        return Builder.Eq(cast<NonConstantExpr>(LHS), RCE);
      }
 
      return Builder.Eq(cast<NonConstantExpr>(LHS),
                        cast<NonConstantExpr>(RHS));
    }
 
    virtual ref<Expr> Ne(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      if (ConstantExpr *LCE = dyn_cast<ConstantExpr>(LHS)) {
        if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS))
          return LCE->Ne(RCE);
        return Builder.Ne(LCE, cast<NonConstantExpr>(RHS));
      } else if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS)) {
        return Builder.Ne(cast<NonConstantExpr>(LHS), RCE);
      }
 
      return Builder.Ne(cast<NonConstantExpr>(LHS),
                        cast<NonConstantExpr>(RHS));
    }
 
    virtual ref<Expr> Ult(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      if (ConstantExpr *LCE = dyn_cast<ConstantExpr>(LHS)) {
        if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS))
          return LCE->Ult(RCE);
        return Builder.Ult(LCE, cast<NonConstantExpr>(RHS));
      } else if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS)) {
        return Builder.Ult(cast<NonConstantExpr>(LHS), RCE);
      }
 
      return Builder.Ult(cast<NonConstantExpr>(LHS),
                         cast<NonConstantExpr>(RHS));
    }
 
    virtual ref<Expr> Ule(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      if (ConstantExpr *LCE = dyn_cast<ConstantExpr>(LHS)) {
        if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS))
          return LCE->Ule(RCE);
        return Builder.Ule(LCE, cast<NonConstantExpr>(RHS));
      } else if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS)) {
        return Builder.Ule(cast<NonConstantExpr>(LHS), RCE);
      }
 
      return Builder.Ule(cast<NonConstantExpr>(LHS),
                         cast<NonConstantExpr>(RHS));
    }
 
    virtual ref<Expr> Ugt(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      if (ConstantExpr *LCE = dyn_cast<ConstantExpr>(LHS)) {
        if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS))
          return LCE->Ugt(RCE);
        return Builder.Ugt(LCE, cast<NonConstantExpr>(RHS));
      } else if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS)) {
        return Builder.Ugt(cast<NonConstantExpr>(LHS), RCE);
      }
 
      return Builder.Ugt(cast<NonConstantExpr>(LHS),
                         cast<NonConstantExpr>(RHS));
    }
 
    virtual ref<Expr> Uge(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      if (ConstantExpr *LCE = dyn_cast<ConstantExpr>(LHS)) {
        if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS))
          return LCE->Uge(RCE);
        return Builder.Uge(LCE, cast<NonConstantExpr>(RHS));
      } else if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS)) {
        return Builder.Uge(cast<NonConstantExpr>(LHS), RCE);
      }
 
      return Builder.Uge(cast<NonConstantExpr>(LHS),
                         cast<NonConstantExpr>(RHS));
    }
 
    virtual ref<Expr> Slt(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      if (ConstantExpr *LCE = dyn_cast<ConstantExpr>(LHS)) {
        if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS))
          return LCE->Slt(RCE);
        return Builder.Slt(LCE, cast<NonConstantExpr>(RHS));
      } else if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS)) {
        return Builder.Slt(cast<NonConstantExpr>(LHS), RCE);
      }
 
      return Builder.Slt(cast<NonConstantExpr>(LHS),
                         cast<NonConstantExpr>(RHS));
    }
 
    virtual ref<Expr> Sle(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      if (ConstantExpr *LCE = dyn_cast<ConstantExpr>(LHS)) {
        if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS))
          return LCE->Sle(RCE);
        return Builder.Sle(LCE, cast<NonConstantExpr>(RHS));
      } else if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS)) {
        return Builder.Sle(cast<NonConstantExpr>(LHS), RCE);
      }
 
      return Builder.Sle(cast<NonConstantExpr>(LHS),
                         cast<NonConstantExpr>(RHS));
    }
 
    virtual ref<Expr> Sgt(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      if (ConstantExpr *LCE = dyn_cast<ConstantExpr>(LHS)) {
        if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS))
          return LCE->Sgt(RCE);
        return Builder.Sgt(LCE, cast<NonConstantExpr>(RHS));
      } else if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS)) {
        return Builder.Sgt(cast<NonConstantExpr>(LHS), RCE);
      }
 
      return Builder.Sgt(cast<NonConstantExpr>(LHS),
                         cast<NonConstantExpr>(RHS));
    }
 
    virtual ref<Expr> Sge(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      if (ConstantExpr *LCE = dyn_cast<ConstantExpr>(LHS)) {
        if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS))
          return LCE->Sge(RCE);
        return Builder.Sge(LCE, cast<NonConstantExpr>(RHS));
      } else if (ConstantExpr *RCE = dyn_cast<ConstantExpr>(RHS)) {
        return Builder.Sge(cast<NonConstantExpr>(LHS), RCE);
      }
 
      return Builder.Sge(cast<NonConstantExpr>(LHS),
                         cast<NonConstantExpr>(RHS));
    }
  };
 
  class ConstantFoldingBuilder :
    public ChainedBuilder {
  public:
    ConstantFoldingBuilder(ExprBuilder *Builder, ExprBuilder *Base)
      : ChainedBuilder(Builder, Base) {}
 
    ref<Expr> Add(const ref<ConstantExpr> &LHS,
                  const ref<NonConstantExpr> &RHS) {
      // 0 + X ==> X
      if (LHS->isZero())
        return RHS;
 
      switch (RHS->getKind()) {
      default: break;
 
      case Expr::Add: {
        BinaryExpr *BE = cast<BinaryExpr>(RHS);
        // C_0 + (C_1 + X) ==> (C_0 + C1) + X
        if (ConstantExpr *CE = dyn_cast<ConstantExpr>(BE->left))
          return Builder->Add(LHS->Add(CE), BE->right);
        // C_0 + (X + C_1) ==> (C_0 + C1) + X
        if (ConstantExpr *CE = dyn_cast<ConstantExpr>(BE->right))
          return Builder->Add(LHS->Add(CE), BE->left);
        break;
      }
 
      case Expr::Sub: {
        BinaryExpr *BE = cast<BinaryExpr>(RHS);
        // C_0 + (C_1 - X) ==> (C_0 + C1) - X
        if (ConstantExpr *CE = dyn_cast<ConstantExpr>(BE->left))
          return Builder->Sub(LHS->Add(CE), BE->right);
        // C_0 + (X - C_1) ==> (C_0 - C1) + X
        if (ConstantExpr *CE = dyn_cast<ConstantExpr>(BE->right))
          return Builder->Add(LHS->Sub(CE), BE->left);
        break;
      }
      }
 
      return Base->Add(LHS, RHS);
    }
 
    ref<Expr> Add(const ref<NonConstantExpr> &LHS,
                  const ref<ConstantExpr> &RHS) {
      return Add(RHS, LHS);
    }
 
    ref<Expr> Add(const ref<NonConstantExpr> &LHS,
                  const ref<NonConstantExpr> &RHS) {
      switch (LHS->getKind()) {
      default: break;
 
      case Expr::Add: {
        BinaryExpr *BE = cast<BinaryExpr>(LHS);
        // (X + Y) + Z ==> X + (Y + Z)
        return Builder->Add(BE->left,
                            Builder->Add(BE->right, RHS));
      }
 
      case Expr::Sub: {
        BinaryExpr *BE = cast<BinaryExpr>(LHS);
        // (X - Y) + Z ==> X + (Z - Y)
        return Builder->Add(BE->left,
                            Builder->Sub(RHS, BE->right));
      }
      }
 
      switch (RHS->getKind()) {
      default: break;
 
      case Expr::Add: {
        BinaryExpr *BE = cast<BinaryExpr>(RHS);
        // X + (C_0 + Y) ==> C_0 + (X + Y)
        if (ConstantExpr *CE = dyn_cast<ConstantExpr>(BE->left))
          return Builder->Add(CE, Builder->Add(LHS, BE->right));
        // X + (Y + C_0) ==> C_0 + (X + Y)
        if (ConstantExpr *CE = dyn_cast<ConstantExpr>(BE->right))
          return Builder->Add(CE, Builder->Add(LHS, BE->left));
        break;
      }
 
      case Expr::Sub: {
        BinaryExpr *BE = cast<BinaryExpr>(RHS);
        // X + (C_0 - Y) ==> C_0 + (X - Y)
        if (ConstantExpr *CE = dyn_cast<ConstantExpr>(BE->left))
          return Builder->Add(CE, Builder->Sub(LHS, BE->right));
        // X + (Y - C_0) ==> -C_0 + (X + Y)
        if (ConstantExpr *CE = dyn_cast<ConstantExpr>(BE->right))
          return Builder->Add(CE->Neg(), Builder->Add(LHS, BE->left));
        break;
      }
      }
 
      return Base->Add(LHS, RHS);
    }
 
    ref<Expr> Sub(const ref<ConstantExpr> &LHS,
                  const ref<NonConstantExpr> &RHS) {
      switch (RHS->getKind()) {
      default: break;
 
      case Expr::Add: {
        BinaryExpr *BE = cast<BinaryExpr>(RHS);
        // C_0 - (C_1 + X) ==> (C_0 - C1) - X
        if (ConstantExpr *CE = dyn_cast<ConstantExpr>(BE->left))
          return Builder->Sub(LHS->Sub(CE), BE->right);
        // C_0 - (X + C_1) ==> (C_0 + C1) + X
        if (ConstantExpr *CE = dyn_cast<ConstantExpr>(BE->right))
          return Builder->Sub(LHS->Sub(CE), BE->left);
        break;
      }
 
      case Expr::Sub: {
        BinaryExpr *BE = cast<BinaryExpr>(RHS);
        // C_0 - (C_1 - X) ==> (C_0 - C1) + X
        if (ConstantExpr *CE = dyn_cast<ConstantExpr>(BE->left))
          return Builder->Add(LHS->Sub(CE), BE->right);
        // C_0 - (X - C_1) ==> (C_0 + C1) - X
        if (ConstantExpr *CE = dyn_cast<ConstantExpr>(BE->right))
          return Builder->Sub(LHS->Add(CE), BE->left);
        break;
      }
      }
 
      return Base->Sub(LHS, RHS);
    }
 
    ref<Expr> Sub(const ref<NonConstantExpr> &LHS,
                  const ref<ConstantExpr> &RHS) {
        // X - C_0 ==> -C_0 + X
      return Add(RHS->Neg(), LHS);
    }
 
    ref<Expr> Sub(const ref<NonConstantExpr> &LHS,
                  const ref<NonConstantExpr> &RHS) {
      switch (LHS->getKind()) {
      default: break;
 
      case Expr::Add: {
        BinaryExpr *BE = cast<BinaryExpr>(LHS);
        // (X + Y) - Z ==> X + (Y - Z)
        return Builder->Add(BE->left, Builder->Sub(BE->right, RHS));
      }
 
      case Expr::Sub: {
        BinaryExpr *BE = cast<BinaryExpr>(LHS);
        // (X - Y) - Z ==> X - (Y + Z)
        return Builder->Sub(BE->left, Builder->Add(BE->right, RHS));
      }
      }
 
      switch (RHS->getKind()) {
      default: break;
 
      case Expr::Add: {
        BinaryExpr *BE = cast<BinaryExpr>(RHS);
        // X - (C + Y) ==> -C + (X - Y)
        if (ConstantExpr *CE = dyn_cast<ConstantExpr>(BE->left))
          return Builder->Add(CE->Neg(), Builder->Sub(LHS, BE->right));
        // X - (Y + C) ==> -C + (X + Y)
        if (ConstantExpr *CE = dyn_cast<ConstantExpr>(BE->right))
          return Builder->Add(CE->Neg(), Builder->Sub(LHS, BE->left));
        break;
      }
 
      case Expr::Sub: {
        BinaryExpr *BE = cast<BinaryExpr>(RHS);
        // X - (C - Y) ==> -C + (X + Y)
        if (ConstantExpr *CE = dyn_cast<ConstantExpr>(BE->left))
          return Builder->Add(CE->Neg(), Builder->Add(LHS, BE->right));
        // X - (Y - C) ==> C + (X - Y)
        if (ConstantExpr *CE = dyn_cast<ConstantExpr>(BE->right))
          return Builder->Add(CE, Builder->Sub(LHS, BE->left));
        break;
      }
      }
 
      return Base->Sub(LHS, RHS);
    }
 
    ref<Expr> Mul(const ref<ConstantExpr> &LHS,
                  const ref<NonConstantExpr> &RHS) {
      if (LHS->isZero())
        return LHS;
      if (LHS->isOne())
        return RHS;
      // FIXME: Unbalance nested muls, fold constants through
      // {sub,add}-with-constant, etc.
      return Base->Mul(LHS, RHS);
    }
 
    ref<Expr> Mul(const ref<NonConstantExpr> &LHS,
                  const ref<ConstantExpr> &RHS) {
      return Mul(RHS, LHS);
    }
 
    ref<Expr> Mul(const ref<NonConstantExpr> &LHS,
                  const ref<NonConstantExpr> &RHS) {
      return Base->Mul(LHS, RHS);
    }
 
    ref<Expr> And(const ref<ConstantExpr> &LHS,
                  const ref<NonConstantExpr> &RHS) {
      if (LHS->isZero())
        return LHS;
      if (LHS->isAllOnes())
        return RHS;
      // FIXME: Unbalance nested ands, fold constants through
      // {and,or}-with-constant, etc.
      return Base->And(LHS, RHS);
    }
 
    ref<Expr> And(const ref<NonConstantExpr> &LHS,
                  const ref<ConstantExpr> &RHS) {
      return And(RHS, LHS);
    }
 
    ref<Expr> And(const ref<NonConstantExpr> &LHS,
                  const ref<NonConstantExpr> &RHS) {
      return Base->And(LHS, RHS);
    }
 
    ref<Expr> Or(const ref<ConstantExpr> &LHS,
                  const ref<NonConstantExpr> &RHS) {
      if (LHS->isZero())
        return RHS;
      if (LHS->isAllOnes())
        return LHS;
      // FIXME: Unbalance nested ors, fold constants through
      // {and,or}-with-constant, etc.
      return Base->Or(LHS, RHS);
    }
 
    ref<Expr> Or(const ref<NonConstantExpr> &LHS,
                 const ref<ConstantExpr> &RHS) {
      return Or(RHS, LHS);
    }
 
    ref<Expr> Or(const ref<NonConstantExpr> &LHS,
                 const ref<NonConstantExpr> &RHS) {
      return Base->Or(LHS, RHS);
    }
 
    ref<Expr> Xor(const ref<ConstantExpr> &LHS,
                  const ref<NonConstantExpr> &RHS) {
      if (LHS->isZero())
        return RHS;
      // FIXME: Unbalance nested ors, fold constants through
      // {and,or}-with-constant, etc.
      return Base->Xor(LHS, RHS);
    }
 
    ref<Expr> Xor(const ref<NonConstantExpr> &LHS,
                  const ref<ConstantExpr> &RHS) {
      return Xor(RHS, LHS);
    }
 
    ref<Expr> Xor(const ref<NonConstantExpr> &LHS,
                  const ref<NonConstantExpr> &RHS) {
      return Base->Xor(LHS, RHS);
    }
 
    ref<Expr> Eq(const ref<ConstantExpr> &LHS, 
                 const ref<NonConstantExpr> &RHS) {
      Expr::Width Width = LHS->getWidth();
      
      if (Width == Expr::Bool) {
        // true == X ==> X
        if (LHS->isTrue())
          return RHS;
 
        // false == ... (not)
        return Base->Not(RHS);
      }
 
      return Base->Eq(LHS, RHS);
    }
 
    ref<Expr> Eq(const ref<NonConstantExpr> &LHS, 
                 const ref<ConstantExpr> &RHS) {
      return Eq(RHS, LHS);
    }
 
    ref<Expr> Eq(const ref<NonConstantExpr> &LHS, 
                 const ref<NonConstantExpr> &RHS) {
      return Base->Eq(LHS, RHS);
    }
  };
 
  typedef ConstantSpecializedExprBuilder<ConstantFoldingBuilder>
    ConstantFoldingExprBuilder;
 
  class SimplifyingBuilder : public ChainedBuilder {
  public:
    SimplifyingBuilder(ExprBuilder *Builder, ExprBuilder *Base)
      : ChainedBuilder(Builder, Base) {}
 
    ref<Expr> Eq(const ref<ConstantExpr> &LHS, 
                 const ref<NonConstantExpr> &RHS) {
      Expr::Width Width = LHS->getWidth();
      
      if (Width == Expr::Bool) {
        // true == X ==> X
        if (LHS->isTrue())
          return RHS;
 
        // false == X (not)
        return Base->Not(RHS);
      }
 
      return Base->Eq(LHS, RHS);
    }
 
    ref<Expr> Eq(const ref<NonConstantExpr> &LHS, 
                 const ref<ConstantExpr> &RHS) {
      return Eq(RHS, LHS);
    }
 
    ref<Expr> Eq(const ref<NonConstantExpr> &LHS, 
                 const ref<NonConstantExpr> &RHS) {
      // X == X ==> true
      if (LHS == RHS)
          return Builder->True();
 
      return Base->Eq(LHS, RHS);
    }
 
    ref<Expr> Not(const ref<NonConstantExpr> &LHS) {
      // Transform !(a or b) ==> !a and !b.
      if (const OrExpr *OE = dyn_cast<OrExpr>(LHS))
        return Builder->And(Builder->Not(OE->left),
                            Builder->Not(OE->right));
      return Base->Not(LHS);
    }
 
    ref<Expr> Ne(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      // X != Y ==> !(X == Y)
      return Builder->Not(Builder->Eq(LHS, RHS));
    }
 
    ref<Expr> Ugt(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      // X u> Y ==> Y u< X
      return Builder->Ult(RHS, LHS);
    }
 
    ref<Expr> Uge(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      // X u>= Y ==> Y u<= X
      return Builder->Ule(RHS, LHS);
    }
 
    ref<Expr> Sgt(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      // X s> Y ==> Y s< X
      return Builder->Slt(RHS, LHS);
    }
 
    ref<Expr> Sge(const ref<Expr> &LHS, const ref<Expr> &RHS) {
      // X s>= Y ==> Y s<= X
      return Builder->Sle(RHS, LHS);
    }
  };
 
  typedef ConstantSpecializedExprBuilder<SimplifyingBuilder>
    SimplifyingExprBuilder;
}
 
ExprBuilder *klee::createDefaultExprBuilder() {
  return new DefaultExprBuilder();
}
 
ExprBuilder *klee::createConstantFoldingExprBuilder(ExprBuilder *Base) {
  return new ConstantFoldingExprBuilder(Base);
}
 
ExprBuilder *klee::createSimplifyingExprBuilder(ExprBuilder *Base) {
  return new SimplifyingExprBuilder(Base);
}