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//===-- llvm/Constant.h - Constant class definition -------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains the declaration of the Constant class.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CONSTANT_H
#define LLVM_CONSTANT_H
#include "llvm/User.h"
namespace llvm {
template<typename T> class SmallVectorImpl;
/// If object contains references to other objects, then relocations are
/// usually required for emission of such object (especially in PIC mode). One
/// usually distinguishes local and global relocations. Local relocations are
/// made wrt objects in the same module and these objects have local (internal
/// or private) linkage. Global relocations are made wrt externally visible
/// objects. In most cases local relocations can be resolved via so-called
/// 'pre-link' technique.
namespace Reloc {
const unsigned None = 0;
const unsigned Local = 1 << 0; ///< Local relocations are required
const unsigned Global = 1 << 1; ///< Global relocations are required
const unsigned LocalOrGlobal = Local | Global;
}
/// This is an important base class in LLVM. It provides the common facilities
/// of all constant values in an LLVM program. A constant is a value that is
/// immutable at runtime. Functions are constants because their address is
/// immutable. Same with global variables.
///
/// All constants share the capabilities provided in this class. All constants
/// can have a null value. They can have an operand list. Constants can be
/// simple (integer and floating point values), complex (arrays and structures),
/// or expression based (computations yielding a constant value composed of
/// only certain operators and other constant values).
///
/// Note that Constants are immutable (once created they never change)
/// and are fully shared by structural equivalence. This means that two
/// structurally equivalent constants will always have the same address.
/// Constants are created on demand as needed and never deleted: thus clients
/// don't have to worry about the lifetime of the objects.
/// @brief LLVM Constant Representation
class Constant : public User {
void operator=(const Constant &); // Do not implement
Constant(const Constant &); // Do not implement
protected:
Constant(const Type *ty, ValueTy vty, Use *Ops, unsigned NumOps)
: User(ty, vty, Ops, NumOps) {}
void destroyConstantImpl();
public:
/// Static constructor to get a '0' constant of arbitrary type...
///
static Constant *getNullValue(const Type *Ty);
/// Static constructor to get a '-1' constant. This supports integers and
/// vectors.
///
static Constant *getAllOnesValue(const Type *Ty);
/// isNullValue - Return true if this is the value that would be returned by
/// getNullValue.
virtual bool isNullValue() const = 0;
/// canTrap - Return true if evaluation of this constant could trap. This is
/// true for things like constant expressions that could divide by zero.
bool canTrap() const;
/// ContainsRelocations - Return true if the constant value contains
/// relocations which cannot be resolved at compile time. Note that answer is
/// not exclusive: there can be possibility that relocations of other kind are
/// required as well.
bool ContainsRelocations(unsigned Kind = Reloc::LocalOrGlobal) const;
// Specialize get/setOperand for Constants as their operands are always
// constants as well.
Constant *getOperand(unsigned i) {
return static_cast<Constant*>(User::getOperand(i));
}
const Constant *getOperand(unsigned i) const {
return static_cast<const Constant*>(User::getOperand(i));
}
void setOperand(unsigned i, Constant *C) {
User::setOperand(i, C);
}
/// getVectorElements - This method, which is only valid on constant of vector
/// type, returns the elements of the vector in the specified smallvector.
/// This handles breaking down a vector undef into undef elements, etc. For
/// constant exprs and other cases we can't handle, we return an empty vector.
void getVectorElements(SmallVectorImpl<Constant*> &Elts) const;
/// destroyConstant - Called if some element of this constant is no longer
/// valid. At this point only other constants may be on the use_list for this
/// constant. Any constants on our Use list must also be destroy'd. The
/// implementation must be sure to remove the constant from the list of
/// available cached constants. Implementations should call
/// destroyConstantImpl as the last thing they do, to destroy all users and
/// delete this.
virtual void destroyConstant() { assert(0 && "Not reached!"); }
//// Methods for support type inquiry through isa, cast, and dyn_cast:
static inline bool classof(const Constant *) { return true; }
static inline bool classof(const GlobalValue *) { return true; }
static inline bool classof(const Value *V) {
return V->getValueID() >= ConstantFirstVal &&
V->getValueID() <= ConstantLastVal;
}
/// replaceUsesOfWithOnConstant - This method is a special form of
/// User::replaceUsesOfWith (which does not work on constants) that does work
/// on constants. Basically this method goes through the trouble of building
/// a new constant that is equivalent to the current one, with all uses of
/// From replaced with uses of To. After this construction is completed, all
/// of the users of 'this' are replaced to use the new constant, and then
/// 'this' is deleted. In general, you should not call this method, instead,
/// use Value::replaceAllUsesWith, which automatically dispatches to this
/// method as needed.
///
virtual void replaceUsesOfWithOnConstant(Value *, Value *, Use *) {
// Provide a default implementation for constants (like integers) that
// cannot use any other values. This cannot be called at runtime, but needs
// to be here to avoid link errors.
assert(getNumOperands() == 0 && "replaceUsesOfWithOnConstant must be "
"implemented for all constants that have operands!");
assert(0 && "Constants that do not have operands cannot be using 'From'!");
}
};
} // End llvm namespace
#endif
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