text: /*
   * Copyright (c) 1999, 2011, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.
   *
   * This code is distributed in the hope that it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   * version 2 for more details (a copy is included in the LICENSE file that
   * accompanied this code).
   *
   * You should have received a copy of the GNU General Public License version
   * 2 along with this work; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   * or visit www.oracle.com if you need additional information or have any
   * questions.
   *
   */
  
  #ifndef SHARE_VM_CI_CIOBJECT_HPP
  #define SHARE_VM_CI_CIOBJECT_HPP
  
  #include "ci/ciClassList.hpp"
  #include "memory/allocation.hpp"
  #include "runtime/handles.hpp"
  #include "runtime/jniHandles.hpp"
  
  // ciObject
  //
  // This class represents an oop in the HotSpot virtual machine.
  // Its subclasses are structured in a hierarchy which mirrors
  // an aggregate of the VM's oop and klass hierarchies (see
  // oopHierarchy.hpp).  Each instance of ciObject holds a handle
  // to a corresponding oop on the VM side and provides routines
  // for accessing the information in its oop.  By using the ciObject
  // hierarchy for accessing oops in the VM, the compiler ensures
  // that it is safe with respect to garbage collection; that is,
  // GC and compilation can proceed independently without
  // interference.
  //
  // Within the VM, the oop and klass hierarchies are separate.
  // The compiler interface does not preserve this separation --
  // the distinction between `klassOop' and `Klass' are not
  // reflected in the interface and instead the Klass hierarchy
  // is directly modeled as the subclasses of ciKlass.
  class ciObject : public ResourceObj {
    CI_PACKAGE_ACCESS
    friend class ciEnv;
  
  private:
    // A JNI handle referring to an oop in the VM.  This
    // handle may, in a small set of cases, correctly be NULL.
    jobject  _handle;
    ciKlass* _klass;
    uint     _ident;
  
    enum { FLAG_BITS   = 2 };
    enum {
           PERM_FLAG        = 1,
           SCAVENGABLE_FLAG = 2
         };
  protected:
    ciObject();
    ciObject(oop o);
    ciObject(Handle h);
    ciObject(ciKlass* klass);
  
    jobject      handle()  const { return _handle; }
    // Get the VM oop that this object holds.
    oop get_oop() const {
      assert(_handle != NULL, "null oop");
      return JNIHandles::resolve_non_null(_handle);
    }
  
    void init_flags_from(oop x) {
      int flags = 0;
      if (x != NULL) {
        if (x->is_perm())
          flags |= PERM_FLAG;
        if (x->is_scavengable())
          flags |= SCAVENGABLE_FLAG;
      }
      _ident |= flags;
    }
  
    // Virtual behavior of the print() method.
    virtual void print_impl(outputStream* st) {}
  
    virtual const char* type_string() { return "ciObject"; }
  
    void set_ident(uint id);
  public:
    // The klass of this ciObject.
    ciKlass* klass();
  
    // A number unique to this object.
    uint ident();
  
    // Are two ciObjects equal?
    bool equals(ciObject* obj);
  
    // A hash value for the convenience of compilers.
    int hash();
  
    // Tells if this oop has an encoding as a constant.
    // True if is_perm is true.
    // Also true if ScavengeRootsInCode is non-zero.
    // If it does not have an encoding, the compiler is responsible for
    // making other arrangements for dealing with the oop.
    // See ciEnv::make_array
    bool can_be_constant();
  
    // Tells if this oop should be made a constant.
    // True if is_perm is true or ScavengeRootsInCode > 1.
    bool should_be_constant();
  
    // Is this object guaranteed to be in the permanent part of the heap?
    // If so, CollectedHeap::can_elide_permanent_oop_store_barriers is relevant.
    // If the answer is false, no guarantees are made.
    bool is_perm() { return (_ident & PERM_FLAG) != 0; }
  
    // Might this object possibly move during a scavenge operation?
    // If the answer is true and ScavengeRootsInCode==0, the oop cannot be embedded in code.
    bool is_scavengable() { return (_ident & SCAVENGABLE_FLAG) != 0; }
  
    // The address which the compiler should embed into the
    // generated code to represent this oop.  This address
    // is not the true address of the oop -- it will get patched
    // during nmethod creation.
    //
    // Usage note: no address arithmetic allowed.  Oop must
    // be registered with the oopRecorder.
    jobject constant_encoding();
  
    // What kind of ciObject is this?
    virtual bool is_null_object() const       { return false; }
    virtual bool is_call_site() const         { return false; }
    virtual bool is_cpcache() const           { return false; }
    virtual bool is_instance()                { return false; }
    virtual bool is_method()                  { return false; }
    virtual bool is_method_data()             { return false; }
    virtual bool is_method_handle() const     { return false; }
    virtual bool is_array()                   { return false; }
    virtual bool is_obj_array()               { return false; }
    virtual bool is_type_array()              { return false; }
    virtual bool is_symbol()                  { return false; }
    virtual bool is_type()                    { return false; }
    virtual bool is_return_address()          { return false; }
    virtual bool is_klass()                   { return false; }
    virtual bool is_instance_klass()          { return false; }
    virtual bool is_method_klass()            { return false; }
    virtual bool is_array_klass()             { return false; }
    virtual bool is_obj_array_klass()         { return false; }
    virtual bool is_type_array_klass()        { return false; }
    virtual bool is_symbol_klass()            { return false; }
    virtual bool is_klass_klass()             { return false; }
    virtual bool is_instance_klass_klass()    { return false; }
    virtual bool is_array_klass_klass()       { return false; }
    virtual bool is_obj_array_klass_klass()   { return false; }
    virtual bool is_type_array_klass_klass()  { return false; }
  
    // Is this a type or value which has no associated class?
    // It is true of primitive types and null objects.
    virtual bool is_classless() const         { return false; }
  
    // Is this ciObject a Java Language Object?  That is,
    // is the ciObject an instance or an array
    virtual bool is_java_object()             { return false; }
  
    // Does this ciObject represent a Java Language class?
    // That is, is the ciObject an instanceKlass or arrayKlass?
    virtual bool is_java_klass()              { return false; }
  
    // Is this ciObject the ciInstanceKlass representing
    // java.lang.Object()?
    virtual bool is_java_lang_Object()        { return false; }
  
    // Does this ciObject refer to a real oop in the VM?
    //
    // Note: some ciObjects refer to oops which have yet to be
    // created.  We refer to these as "unloaded".  Specifically,
    // there are unloaded ciMethods, ciObjArrayKlasses, and
    // ciInstanceKlasses.  By convention the ciNullObject is
    // considered loaded, and primitive types are considered loaded.
    bool is_loaded() const {
      return handle() != NULL || is_classless();
    }
  
    // Subclass casting with assertions.
    ciNullObject*            as_null_object() {
      assert(is_null_object(), "bad cast");
      return (ciNullObject*)this;
    }
    ciCallSite*              as_call_site() {
      assert(is_call_site(), "bad cast");
      return (ciCallSite*) this;
    }
    ciCPCache*               as_cpcache() {
      assert(is_cpcache(), "bad cast");
      return (ciCPCache*) this;
    }
    ciInstance*              as_instance() {
      assert(is_instance(), "bad cast");
      return (ciInstance*)this;
    }
    ciMethod*                as_method() {
      assert(is_method(), "bad cast");
      return (ciMethod*)this;
    }
    ciMethodData*            as_method_data() {
      assert(is_method_data(), "bad cast");
      return (ciMethodData*)this;
    }
    ciMethodHandle*          as_method_handle() {
      assert(is_method_handle(), "bad cast");
      return (ciMethodHandle*) this;
    }
    ciArray*                 as_array() {
      assert(is_array(), "bad cast");
      return (ciArray*)this;
    }
    ciObjArray*              as_obj_array() {
      assert(is_obj_array(), "bad cast");
      return (ciObjArray*)this;
    }
    ciTypeArray*             as_type_array() {
      assert(is_type_array(), "bad cast");
      return (ciTypeArray*)this;
    }
    ciSymbol*                as_symbol() {
      assert(is_symbol(), "bad cast");
      return (ciSymbol*)this;
    }
    ciType*                  as_type() {
      assert(is_type(), "bad cast");
      return (ciType*)this;
    }
    ciReturnAddress*         as_return_address() {
      assert(is_return_address(), "bad cast");
      return (ciReturnAddress*)this;
    }
    ciKlass*                 as_klass() {
      assert(is_klass(), "bad cast");
      return (ciKlass*)this;
    }
    ciInstanceKlass*         as_instance_klass() {
      assert(is_instance_klass(), "bad cast");
      return (ciInstanceKlass*)this;
    }
    ciMethodKlass*           as_method_klass() {
      assert(is_method_klass(), "bad cast");
      return (ciMethodKlass*)this;
    }
    ciArrayKlass*            as_array_klass() {
      assert(is_array_klass(), "bad cast");
      return (ciArrayKlass*)this;
    }
    ciObjArrayKlass*         as_obj_array_klass() {
      assert(is_obj_array_klass(), "bad cast");
      return (ciObjArrayKlass*)this;
    }
    ciTypeArrayKlass*        as_type_array_klass() {
      assert(is_type_array_klass(), "bad cast");
      return (ciTypeArrayKlass*)this;
    }
    ciKlassKlass*            as_klass_klass() {
      assert(is_klass_klass(), "bad cast");
      return (ciKlassKlass*)this;
    }
    ciInstanceKlassKlass*    as_instance_klass_klass() {
      assert(is_instance_klass_klass(), "bad cast");
      return (ciInstanceKlassKlass*)this;
    }
    ciArrayKlassKlass*       as_array_klass_klass() {
      assert(is_array_klass_klass(), "bad cast");
      return (ciArrayKlassKlass*)this;
    }
    ciObjArrayKlassKlass*    as_obj_array_klass_klass() {
      assert(is_obj_array_klass_klass(), "bad cast");
      return (ciObjArrayKlassKlass*)this;
    }
    ciTypeArrayKlassKlass*   as_type_array_klass_klass() {
      assert(is_type_array_klass_klass(), "bad cast");
      return (ciTypeArrayKlassKlass*)this;
    }
  
    // Print debugging output about this ciObject.
    void print(outputStream* st = tty);
  
    // Print debugging output about the oop this ciObject represents.
    void print_oop(outputStream* st = tty);
  };
  
  #endif // SHARE_VM_CI_CIOBJECT_HPP
  