/*

 * Copyright (c) 1999, 2010, 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.

 *

 */

#include "precompiled.hpp"

#include "ci/ciObject.hpp"

#include "ci/ciUtilities.hpp"

#include "gc_interface/collectedHeap.inline.hpp"

#include "oops/oop.inline2.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.

// ------------------------------------------------------------------

// ciObject::ciObject

ciObject::ciObject(oop o) {

  ASSERT_IN_VM;

  if (ciObjectFactory::is_initialized()) {

    _handle = JNIHandles::make_local(o);

  } else {

    _handle = JNIHandles::make_global(o);

  }

  _klass = NULL;

  _ident = 0;

  init_flags_from(o);

}

// ------------------------------------------------------------------

// ciObject::ciObject

//

ciObject::ciObject(Handle h) {

  ASSERT_IN_VM;

  if (ciObjectFactory::is_initialized()) {

    _handle = JNIHandles::make_local(h());

  } else {

    _handle = JNIHandles::make_global(h);

  }

  _klass = NULL;

  _ident = 0;

  init_flags_from(h());

}

// ------------------------------------------------------------------

// ciObject::ciObject

//

// Unloaded klass/method variant.  `klass' is the klass of the unloaded

// klass/method, if that makes sense.

ciObject::ciObject(ciKlass* klass) {

  ASSERT_IN_VM;

  assert(klass != NULL, "must supply klass");

  _handle = NULL;

  _klass = klass;

  _ident = 0;

}

// ------------------------------------------------------------------

// ciObject::ciObject

//

// NULL variant.  Used only by ciNullObject.

ciObject::ciObject() {

  ASSERT_IN_VM;

  _handle = NULL;

  _klass = NULL;

  _ident = 0;

}

// ------------------------------------------------------------------

// ciObject::klass

//

// Get the ciKlass of this ciObject.

ciKlass* ciObject::klass() {

  if (_klass == NULL) {

    if (_handle == NULL) {

      // When both _klass and _handle are NULL, we are dealing

      // with the distinguished instance of ciNullObject.

      // No one should ask it for its klass.

      assert(is_null_object(), "must be null object");

      ShouldNotReachHere();

      return NULL;

    }

    GUARDED_VM_ENTRY(

      oop o = get_oop();

      _klass = CURRENT_ENV->get_object(o->klass())->as_klass();

    );

  }

  return _klass;

}

// ------------------------------------------------------------------

// ciObject::set_ident

//

// Set the unique identity number of a ciObject.

void ciObject::set_ident(uint id) {

  assert((_ident >> FLAG_BITS) == 0, "must only initialize once");

  assert( id < ((uint)1 << (BitsPerInt-FLAG_BITS)), "id too big");

  _ident = _ident + (id << FLAG_BITS);

}

// ------------------------------------------------------------------

// ciObject::ident

//

// Report the unique identity number of a ciObject.

uint ciObject::ident() {

  uint id = _ident >> FLAG_BITS;

  assert(id != 0, "must be initialized");

  return id;

}

// ------------------------------------------------------------------

// ciObject::equals

//

// Are two ciObjects equal?

bool ciObject::equals(ciObject* obj) {

  return (this == obj);

}

// ------------------------------------------------------------------

// ciObject::hash

//

// A hash value for the convenience of compilers.

//

// Implementation note: we use the address of the ciObject as the

// basis for the hash.  Use the _ident field, which is well-behaved.

int ciObject::hash() {

  return ident() * 31;

}

// ------------------------------------------------------------------

// ciObject::constant_encoding

//

// 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.

//

//

//

// Implementation note: we use the handle as the encoding.  The

// nmethod constructor resolves the handle and patches in the oop.

//

// This method should be changed to return an generified address

// to discourage use of the JNI handle.

jobject ciObject::constant_encoding() {

  assert(is_null_object() || handle() != NULL, "cannot embed null pointer");

  assert(can_be_constant(), "oop must be NULL or perm");

  return handle();

}

// ------------------------------------------------------------------

// ciObject::can_be_constant

bool ciObject::can_be_constant() {

  if (ScavengeRootsInCode >= 1)  return true;  // now everybody can encode as a constant

  return handle() == NULL || is_perm();

}

// ------------------------------------------------------------------

// ciObject::should_be_constant()

bool ciObject::should_be_constant() {

  if (ScavengeRootsInCode >= 2)  return true;  // force everybody to be a constant

  if (is_null_object()) return true;

  ciEnv* env = CURRENT_ENV;

  if (!JavaObjectsInPerm) {

    // We want Strings and Classes to be embeddable by default since

    // they used to be in the perm world.  Not all Strings used to be

    // embeddable but there's no easy way to distinguish the interned

    // from the regulars ones so just treat them all that way.

    if (klass() == env->String_klass() || klass() == env->Class_klass()) {

      return true;

    }

  }

  if (EnableInvokeDynamic &&

      (klass()->is_subclass_of(env->MethodHandle_klass()) ||

       klass()->is_subclass_of(env->CallSite_klass()))) {

    assert(ScavengeRootsInCode >= 1, "must be");

    // We want to treat these aggressively.

    return true;

  }

  return handle() == NULL || is_perm();

}

// ------------------------------------------------------------------

// ciObject::print

//

// Print debugging output about this ciObject.

//

// Implementation note: dispatch to the virtual print_impl behavior

// for this ciObject.

void ciObject::print(outputStream* st) {

  st->print("<%s", type_string());

  GUARDED_VM_ENTRY(print_impl(st);)

  st->print(" ident=%d %s%s address=0x%x>", ident(),

        is_perm() ? "PERM" : "",

        is_scavengable() ? "SCAVENGABLE" : "",

        (address)this);

}

// ------------------------------------------------------------------

// ciObject::print_oop

//

// Print debugging output about the oop this ciObject represents.

void ciObject::print_oop(outputStream* st) {

  if (is_null_object()) {

    st->print_cr("NULL");

  } else if (!is_loaded()) {

    st->print_cr("UNLOADED");

  } else {

    GUARDED_VM_ENTRY(get_oop()->print_on(st);)

  }

}