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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 {
class APInt;
template<typename T> class SmallVectorImpl;
/// 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
virtual void anchor();
protected:
Constant(Type *ty, ValueTy vty, Use *Ops, unsigned NumOps)
: User(ty, vty, Ops, NumOps) {}
void destroyConstantImpl();
public:
/// isNullValue - Return true if this is the value that would be returned by
/// getNullValue.
bool isNullValue() const;
/// isAllOnesValue - Return true if this is the value that would be returned by
/// getAllOnesValue.
bool isAllOnesValue() const;
/// isNegativeZeroValue - Return true if the value is what would be returned
/// by getZeroValueForNegation.
bool isNegativeZeroValue() const;
/// 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;
/// isConstantUsed - Return true if the constant has users other than constant
/// exprs and other dangling things.
bool isConstantUsed() const;
enum PossibleRelocationsTy {
NoRelocation = 0,
LocalRelocation = 1,
GlobalRelocations = 2
};
/// getRelocationInfo - This method classifies the entry according to
/// whether or not it may generate a relocation entry. This must be
/// conservative, so if it might codegen to a relocatable entry, it should say
/// so. The return values are:
///
/// NoRelocation: This constant pool entry is guaranteed to never have a
/// relocation applied to it (because it holds a simple constant like
/// '4').
/// LocalRelocation: This entry has relocations, but the entries are
/// guaranteed to be resolvable by the static linker, so the dynamic
/// linker will never see them.
/// GlobalRelocations: This entry may have arbitrary relocations.
///
/// FIXME: This really should not be in VMCore.
PossibleRelocationsTy getRelocationInfo() const;
/// getAggregateElement - For aggregates (struct/array/vector) return the
/// constant that corresponds to the specified element if possible, or null if
/// not. This can return null if the element index is a ConstantExpr, or if
/// 'this' is a constant expr.
Constant *getAggregateElement(unsigned Elt) const;
Constant *getAggregateElement(Constant *Elt) 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() { llvm_unreachable("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!");
llvm_unreachable("Constants that do not have operands cannot be using "
"'From'!");
}
static Constant *getNullValue(Type* Ty);
/// @returns the value for an integer or vector of integer constant of the
/// given type that has all its bits set to true.
/// @brief Get the all ones value
static Constant *getAllOnesValue(Type* Ty);
/// getIntegerValue - Return the value for an integer or pointer constant,
/// or a vector thereof, with the given scalar value.
static Constant *getIntegerValue(Type* Ty, const APInt &V);
/// removeDeadConstantUsers - If there are any dead constant users dangling
/// off of this constant, remove them. This method is useful for clients
/// that want to check to see if a global is unused, but don't want to deal
/// with potentially dead constants hanging off of the globals.
void removeDeadConstantUsers() const;
};
} // End llvm namespace
#endif
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