New file for supporting abstract types

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@502 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/AbstractTypeUser.h

@@ -0,0 +1,134 @@
+//===-- llvm/AbstractTypeUser.h - AbstractTypeUser Interface -----*- C++ -*--=//
+//
+// The AbstractTypeUser class is an interface to be implemented by classes who
+// could possible use an abstract type.  Abstract types are denoted by the
+// isAbstract flag set to true in the Type class.  These are classes that
+// contain an Opaque type in their structure somehow.
+//
+// Classes must implement this interface so that they may be notified when an
+// abstract type is resolved.  Abstract types may be resolved into more concrete
+// types through: linking, parsing, and bytecode reading.  When this happens,
+// all of the users of the type must be updated to reference the new, more
+// concrete type.  They are notified through the AbstractTypeUser interface.
+//
+// In addition to this, AbstractTypeUsers must keep the use list of the
+// potentially abstract type that they reference up-to-date.  To do this in a
+// nice, transparent way, the PATypeHandle class is used to hold "Potentially
+// Abstract Types", and keep the use list of the abstract types up-to-date.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ABSTRACT_TYPE_USER_H
+#define LLVM_ABSTRACT_TYPE_USER_H
+
+class Type;
+class DerivedType;
+
+class AbstractTypeUser {
+protected:
+  virtual ~AbstractTypeUser() {}                        // Derive from me
+public:
+
+  // refineAbstractType - The callback method invoked when an abstract type
+  // has been found to be more concrete.  A class must override this method to
+  // update its internal state to reference NewType instead of OldType.  Soon
+  // after this method is invoked, OldType shall be deleted, so referencing it
+  // is quite unwise.
+  //
+  virtual void refineAbstractType(const DerivedType *OldTy,
+				  const Type *NewTy) = 0;
+};
+
+
+// PATypeHandle - Handle to a Type subclass.  This class is parameterized so
+// that users can have handles to MethodType's that are still specialized, for
+// example.  This class is a simple class used to keep the use list of abstract
+// types up-to-date.
+//
+template <class TypeSubClass>
+class PATypeHandle {
+  const TypeSubClass *Ty;
+  AbstractTypeUser * const User;
+
+  // These functions are defined at the bottom of Type.h.  See the comment there
+  // for justification.
+  inline void addUser();
+  inline void removeUser();
+public:
+  // ctor - Add use to type if abstract.  Note that Ty must not be null
+  inline PATypeHandle(const TypeSubClass *ty, AbstractTypeUser *user) 
+    : Ty(ty), User(user) {
+    addUser();
+  }
+
+  // ctor - Add use to type if abstract.
+  inline PATypeHandle(const PATypeHandle &T) : Ty(T.Ty), User(T.User) {
+    addUser();
+  }
+
+  // dtor - Remove reference to type...
+  inline ~PATypeHandle() { removeUser(); }
+
+  // Automatic casting operator so that the handle may be used naturally
+  inline operator const TypeSubClass *() const { return Ty; }
+  inline const TypeSubClass *get() const { return Ty; }
+
+  // operator= - Allow assignment to handle
+  inline const TypeSubClass *operator=(const TypeSubClass *ty) {
+    if (Ty != ty) {   // Ensure we don't accidentally drop last ref to Ty
+      removeUser();
+      Ty = ty;
+      addUser();
+    }
+    return Ty;
+  }
+
+  // operator= - Allow assignment to handle
+  inline const TypeSubClass *operator=(const PATypeHandle &T) {
+    return operator=(T.Ty);
+  }
+
+  inline bool operator==(const TypeSubClass *ty) {
+    return Ty == ty;
+  }
+
+  // operator-> - Allow user to dereference handle naturally...
+  inline const TypeSubClass *operator->() const { return Ty; }
+};
+
+
+// PATypeHolder - Holder class for a potentially abstract type.  This functions
+// as both a handle (as above) and an AbstractTypeUser.  It uses the callback to
+// keep its pointer member updated to the current version of the type.
+//
+template <class TypeSC>
+class PATypeHolder : public AbstractTypeUser, public PATypeHandle<TypeSC> {
+public:
+  inline PATypeHolder(const TypeSC *ty) : PATypeHandle<TypeSC>(ty, this) {}
+  inline PATypeHolder(const PATypeHolder &T)
+    : AbstractTypeUser(T), PATypeHandle<TypeSC>(T, this) {}
+
+  // refineAbstractType - All we do is update our PATypeHandle member to point
+  // to the new type.
+  //
+  virtual void refineAbstractType(const DerivedType *OldTy, const Type *NewTy) {
+    assert(get() == OldTy && "Can't refine to unknown value!");
+    PATypeHandle<TypeSC>::operator=((const TypeSC*)NewTy);
+  }
+
+  // operator= - Allow assignment to handle
+  inline const TypeSC *operator=(const TypeSC *ty) {
+    return PATypeHandle<TypeSC>::operator=(ty);
+  }
+
+  // operator= - Allow assignment to handle
+  inline const TypeSC *operator=(const PATypeHandle<TypeSC> &T) {
+    return PATypeHandle<TypeSC>::operator=(T);
+  }
+  inline const TypeSC *operator=(const PATypeHolder<TypeSC> &H) {
+    return PATypeHandle<TypeSC>::operator=(H);
+  }
+};
+
+
+#endif