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//===-- llvm/Constant.h - Constant class definition -------------*- C++ -*-===//
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// The LLVM Compiler Infrastructure
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//===----------------------------------------------------------------------===//
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// This file contains the declaration of the Constant class.
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_CONSTANT_H
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#define LLVM_CONSTANT_H
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#include "llvm/User.h"
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template<typename T> class SmallVectorImpl;
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/// This is an important base class in LLVM. It provides the common facilities
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/// of all constant values in an LLVM program. A constant is a value that is
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/// immutable at runtime. Functions are constants because their address is
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/// immutable. Same with global variables.
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/// All constants share the capabilities provided in this class. All constants
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/// can have a null value. They can have an operand list. Constants can be
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/// simple (integer and floating point values), complex (arrays and structures),
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/// or expression based (computations yielding a constant value composed of
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/// only certain operators and other constant values).
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/// Note that Constants are immutable (once created they never change)
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/// and are fully shared by structural equivalence. This means that two
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/// structurally equivalent constants will always have the same address.
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/// Constants are created on demand as needed and never deleted: thus clients
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/// don't have to worry about the lifetime of the objects.
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/// @brief LLVM Constant Representation
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class Constant : public User {
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void operator=(const Constant &); // Do not implement
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Constant(const Constant &); // Do not implement
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Constant(const Type *ty, ValueTy vty, Use *Ops, unsigned NumOps)
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: User(ty, vty, Ops, NumOps) {}
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void destroyConstantImpl();
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void setOperand(unsigned i, Value *V) {
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User::setOperand(i, V);
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/// isNullValue - Return true if this is the value that would be returned by
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virtual bool isNullValue() const = 0;
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/// isNegativeZeroValue - Return true if the value is what would be returned
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/// by getZeroValueForNegation.
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virtual bool isNegativeZeroValue() const { return isNullValue(); }
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/// canTrap - Return true if evaluation of this constant could trap. This is
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/// true for things like constant expressions that could divide by zero.
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/// isConstantUsed - Return true if the constant has users other than constant
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/// exprs and other dangling things.
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bool isConstantUsed() const;
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enum PossibleRelocationsTy {
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/// getRelocationInfo - This method classifies the entry according to
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/// whether or not it may generate a relocation entry. This must be
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/// conservative, so if it might codegen to a relocatable entry, it should say
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/// so. The return values are:
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/// NoRelocation: This constant pool entry is guaranteed to never have a
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/// relocation applied to it (because it holds a simple constant like
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/// LocalRelocation: This entry has relocations, but the entries are
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/// guaranteed to be resolvable by the static linker, so the dynamic
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/// linker will never see them.
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/// GlobalRelocations: This entry may have arbitrary relocations.
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/// FIXME: This really should not be in VMCore.
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PossibleRelocationsTy getRelocationInfo() const;
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// Specialize get/setOperand for Users as their operands are always
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// constants or BasicBlocks as well.
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User *getOperand(unsigned i) {
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return static_cast<User*>(User::getOperand(i));
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const User *getOperand(unsigned i) const {
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return static_cast<const User*>(User::getOperand(i));
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/// getVectorElements - This method, which is only valid on constant of vector
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/// type, returns the elements of the vector in the specified smallvector.
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/// This handles breaking down a vector undef into undef elements, etc. For
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/// constant exprs and other cases we can't handle, we return an empty vector.
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void getVectorElements(SmallVectorImpl<Constant*> &Elts) const;
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/// destroyConstant - Called if some element of this constant is no longer
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/// valid. At this point only other constants may be on the use_list for this
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/// constant. Any constants on our Use list must also be destroy'd. The
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/// implementation must be sure to remove the constant from the list of
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/// available cached constants. Implementations should call
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/// destroyConstantImpl as the last thing they do, to destroy all users and
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virtual void destroyConstant() { assert(0 && "Not reached!"); }
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//// Methods for support type inquiry through isa, cast, and dyn_cast:
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static inline bool classof(const Constant *) { return true; }
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static inline bool classof(const GlobalValue *) { return true; }
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static inline bool classof(const Value *V) {
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return V->getValueID() >= ConstantFirstVal &&
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V->getValueID() <= ConstantLastVal;
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/// replaceUsesOfWithOnConstant - This method is a special form of
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/// User::replaceUsesOfWith (which does not work on constants) that does work
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/// on constants. Basically this method goes through the trouble of building
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/// a new constant that is equivalent to the current one, with all uses of
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/// From replaced with uses of To. After this construction is completed, all
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/// of the users of 'this' are replaced to use the new constant, and then
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/// 'this' is deleted. In general, you should not call this method, instead,
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/// use Value::replaceAllUsesWith, which automatically dispatches to this
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/// method as needed.
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virtual void replaceUsesOfWithOnConstant(Value *, Value *, Use *) {
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// Provide a default implementation for constants (like integers) that
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// cannot use any other values. This cannot be called at runtime, but needs
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// to be here to avoid link errors.
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assert(getNumOperands() == 0 && "replaceUsesOfWithOnConstant must be "
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"implemented for all constants that have operands!");
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assert(0 && "Constants that do not have operands cannot be using 'From'!");
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static Constant* getNullValue(const Type* Ty);
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/// @returns the value for an integer constant of the given type that has all
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/// its bits set to true.
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/// @brief Get the all ones value
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static Constant* getAllOnesValue(const Type* Ty);
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/// getIntegerValue - Return the value for an integer or pointer constant,
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/// or a vector thereof, with the given scalar value.
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static Constant* getIntegerValue(const Type* Ty, const APInt &V);
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} // End llvm namespace