1 //===-- llvm/AbstractTypeUser.h - AbstractTypeUser Interface -----*- C++ -*--=//
3 // The AbstractTypeUser class is an interface to be implemented by classes who
4 // could possible use an abstract type. Abstract types are denoted by the
5 // isAbstract flag set to true in the Type class. These are classes that
6 // contain an Opaque type in their structure somehow.
8 // Classes must implement this interface so that they may be notified when an
9 // abstract type is resolved. Abstract types may be resolved into more concrete
10 // types through: linking, parsing, and bytecode reading. When this happens,
11 // all of the users of the type must be updated to reference the new, more
12 // concrete type. They are notified through the AbstractTypeUser interface.
14 // In addition to this, AbstractTypeUsers must keep the use list of the
15 // potentially abstract type that they reference up-to-date. To do this in a
16 // nice, transparent way, the PATypeHandle class is used to hold "Potentially
17 // Abstract Types", and keep the use list of the abstract types up-to-date.
19 //===----------------------------------------------------------------------===//
21 #ifndef LLVM_ABSTRACT_TYPE_USER_H
22 #define LLVM_ABSTRACT_TYPE_USER_H
27 class AbstractTypeUser {
29 virtual ~AbstractTypeUser() {} // Derive from me
32 // refineAbstractType - The callback method invoked when an abstract type
33 // has been found to be more concrete. A class must override this method to
34 // update its internal state to reference NewType instead of OldType. Soon
35 // after this method is invoked, OldType shall be deleted, so referencing it
38 // Another case that is important to consider is when a type is refined, but
39 // stays in the same place in memory. In this case OldTy will equal NewTy.
40 // This callback just notifies ATU's that the underlying structure of the type
41 // has changed... but any previously used properties are still valid.
43 // Note that it is possible to refine a type with parameters OldTy==NewTy, and
44 // OldTy is no longer abstract. In this case, abstract type users should
45 // release their hold on a type, because it went from being abstract to
48 virtual void refineAbstractType(const DerivedType *OldTy,
49 const Type *NewTy) = 0;
53 // PATypeHandle - Handle to a Type subclass. This class is parameterized so
54 // that users can have handles to MethodType's that are still specialized, for
55 // example. This class is a simple class used to keep the use list of abstract
58 template <class TypeSubClass>
60 const TypeSubClass *Ty;
61 AbstractTypeUser * const User;
63 // These functions are defined at the bottom of Type.h. See the comment there
65 inline void addUser();
66 inline void removeUser();
68 // ctor - Add use to type if abstract. Note that Ty must not be null
69 inline PATypeHandle(const TypeSubClass *ty, AbstractTypeUser *user)
70 : Ty(ty), User(user) {
74 // ctor - Add use to type if abstract.
75 inline PATypeHandle(const PATypeHandle &T) : Ty(T.Ty), User(T.User) {
79 // dtor - Remove reference to type...
80 inline ~PATypeHandle() { removeUser(); }
82 // Automatic casting operator so that the handle may be used naturally
83 inline operator const TypeSubClass *() const { return Ty; }
84 inline const TypeSubClass *get() const { return Ty; }
86 // operator= - Allow assignment to handle
87 inline const TypeSubClass *operator=(const TypeSubClass *ty) {
88 if (Ty != ty) { // Ensure we don't accidentally drop last ref to Ty
96 // operator= - Allow assignment to handle
97 inline const TypeSubClass *operator=(const PATypeHandle &T) {
98 return operator=(T.Ty);
101 inline bool operator==(const TypeSubClass *ty) {
105 // operator-> - Allow user to dereference handle naturally...
106 inline const TypeSubClass *operator->() const { return Ty; }
108 // removeUserFromConcrete - This function should be called when the User is
109 // notified that our type is refined... and the type is being refined to
110 // itself, which is now a concrete type. When a type becomes concrete like
111 // this, we MUST remove ourself from the AbstractTypeUser list, even though
112 // the type is apparently concrete.
114 inline void removeUserFromConcrete();
118 // PATypeHolder - Holder class for a potentially abstract type. This functions
119 // as both a handle (as above) and an AbstractTypeUser. It uses the callback to
120 // keep its pointer member updated to the current version of the type.
122 template <class TypeSC>
123 class PATypeHolder : public AbstractTypeUser, public PATypeHandle<TypeSC> {
125 inline PATypeHolder(const TypeSC *ty) : PATypeHandle<TypeSC>(ty, this) {}
126 inline PATypeHolder(const PATypeHolder &T)
127 : AbstractTypeUser(T), PATypeHandle<TypeSC>(T, this) {}
129 // refineAbstractType - All we do is update our PATypeHandle member to point
132 virtual void refineAbstractType(const DerivedType *OldTy, const Type *NewTy) {
133 assert(get() == (const Type*)OldTy && "Can't refine to unknown value!");
135 // Check to see if the type just became concrete. If so, we have to
136 // removeUser to get off its AbstractTypeUser list
137 removeUserFromConcrete();
139 if ((const Type*)OldTy != NewTy)
140 PATypeHandle<TypeSC>::operator=((const TypeSC*)NewTy);
143 // operator= - Allow assignment to handle
144 inline const TypeSC *operator=(const TypeSC *ty) {
145 return PATypeHandle<TypeSC>::operator=(ty);
148 // operator= - Allow assignment to handle
149 inline const TypeSC *operator=(const PATypeHandle<TypeSC> &T) {
150 return PATypeHandle<TypeSC>::operator=(T);
152 inline const TypeSC *operator=(const PATypeHolder<TypeSC> &H) {
153 return PATypeHandle<TypeSC>::operator=(H);