-//===-- llvm/Constant.h - Constant class definition --------------*- C++ -*--=//
+//===-- 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.
//
#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
+
protected:
- inline Constant(const Type *Ty) : User(Ty, Value::ConstantVal) {}
- ~Constant() {}
-
- // 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!"); }
+ Constant(Type *ty, ValueTy vty, Use *Ops, unsigned NumOps)
+ : User(ty, vty, Ops, NumOps) {}
+
void destroyConstantImpl();
public:
- // Specialize setName to handle symbol table majik...
- virtual void setName(const std::string &name, SymbolTable *ST = 0);
+ /// isNullValue - Return true if this is the value that would be returned by
+ /// getNullValue.
+ bool isNullValue() const;
- // Static constructor to get a '0' constant of arbitrary type...
- static Constant *getNullValue(const Type *Ty);
+ /// isAllOnesValue - Return true if this is the value that would be returned by
+ /// getAllOnesValue.
+ bool isAllOnesValue() const;
- // isNullValue - Return true if this is the value that would be returned by
- // getNullValue.
- virtual bool isNullValue() const = 0;
+ /// isNegativeZeroValue - Return true if the value is what would be returned
+ /// by getZeroValueForNegation.
+ bool isNegativeZeroValue() const;
- virtual void print(std::ostream &O) 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;
- // Methods for support type inquiry through isa, cast, and dyn_cast:
+ /// 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;
+
+ /// 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->getValueType() == Value::ConstantVal;
+ 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'!");
+ }
+
+ static Constant *getNullValue(Type* Ty);
+
+ /// @returns the value for an 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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