1/*
2 * Copyright (c) 1999, 2017, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25#include "precompiled.hpp"
26#include "ci/ciObject.hpp"
27#include "ci/ciUtilities.hpp"
28#include "gc/shared/collectedHeap.inline.hpp"
29#include "oops/oop.inline.hpp"
30
31// ciObject
32//
33// This class represents an oop in the HotSpot virtual machine.
34// Its subclasses are structured in a hierarchy which mirrors
35// an aggregate of the VM's oop and klass hierarchies (see
36// oopHierarchy.hpp).  Each instance of ciObject holds a handle
37// to a corresponding oop on the VM side and provides routines
38// for accessing the information in its oop.  By using the ciObject
39// hierarchy for accessing oops in the VM, the compiler ensures
40// that it is safe with respect to garbage collection; that is,
41// GC and compilation can proceed independently without
42// interference.
43//
44// Within the VM, the oop and klass hierarchies are separate.
45// The compiler interface does not preserve this separation --
46// the distinction between `Klass*' and `Klass' are not
47// reflected in the interface and instead the Klass hierarchy
48// is directly modeled as the subclasses of ciKlass.
49
50// ------------------------------------------------------------------
51// ciObject::ciObject
52ciObject::ciObject(oop o) {
53  ASSERT_IN_VM;
54  if (ciObjectFactory::is_initialized()) {
55    _handle = JNIHandles::make_local(o);
56  } else {
57    Handle obj(Thread::current(), o);
58    _handle = JNIHandles::make_global(obj);
59  }
60  _klass = NULL;
61  init_flags_from(o);
62}
63
64// ------------------------------------------------------------------
65// ciObject::ciObject
66//
67ciObject::ciObject(Handle h) {
68  ASSERT_IN_VM;
69  if (ciObjectFactory::is_initialized()) {
70    _handle = JNIHandles::make_local(h());
71  } else {
72    _handle = JNIHandles::make_global(h);
73  }
74  _klass = NULL;
75  init_flags_from(h());
76}
77
78// ------------------------------------------------------------------
79// ciObject::ciObject
80//
81// Unloaded klass/method variant.  `klass' is the klass of the unloaded
82// klass/method, if that makes sense.
83ciObject::ciObject(ciKlass* klass) {
84  ASSERT_IN_VM;
85  assert(klass != NULL, "must supply klass");
86  _handle = NULL;
87  _klass = klass;
88}
89
90// ------------------------------------------------------------------
91// ciObject::ciObject
92//
93// NULL variant.  Used only by ciNullObject.
94ciObject::ciObject() {
95  ASSERT_IN_VM;
96  _handle = NULL;
97  _klass = NULL;
98}
99
100// ------------------------------------------------------------------
101// ciObject::klass
102//
103// Get the ciKlass of this ciObject.
104ciKlass* ciObject::klass() {
105  if (_klass == NULL) {
106    if (_handle == NULL) {
107      // When both _klass and _handle are NULL, we are dealing
108      // with the distinguished instance of ciNullObject.
109      // No one should ask it for its klass.
110      assert(is_null_object(), "must be null object");
111      ShouldNotReachHere();
112      return NULL;
113    }
114
115    GUARDED_VM_ENTRY(
116      oop o = get_oop();
117      _klass = CURRENT_ENV->get_klass(o->klass());
118    );
119  }
120  return _klass;
121}
122
123// ------------------------------------------------------------------
124// ciObject::equals
125//
126// Are two ciObjects equal?
127bool ciObject::equals(ciObject* obj) {
128  return (this == obj);
129}
130
131// ------------------------------------------------------------------
132// ciObject::hash
133//
134// A hash value for the convenience of compilers.
135//
136// Implementation note: we use the address of the ciObject as the
137// basis for the hash.  Use the _ident field, which is well-behaved.
138int ciObject::hash() {
139  return ident() * 31;
140}
141
142// ------------------------------------------------------------------
143// ciObject::constant_encoding
144//
145// The address which the compiler should embed into the
146// generated code to represent this oop.  This address
147// is not the true address of the oop -- it will get patched
148// during nmethod creation.
149//
150//
151//
152// Implementation note: we use the handle as the encoding.  The
153// nmethod constructor resolves the handle and patches in the oop.
154//
155// This method should be changed to return an generified address
156// to discourage use of the JNI handle.
157jobject ciObject::constant_encoding() {
158  assert(is_null_object() || handle() != NULL, "cannot embed null pointer");
159  assert(can_be_constant(), "oop must be NULL or perm");
160  return handle();
161}
162
163// ------------------------------------------------------------------
164// ciObject::can_be_constant
165bool ciObject::can_be_constant() {
166  if (ScavengeRootsInCode >= 1)  return true;  // now everybody can encode as a constant
167  return handle() == NULL;
168}
169
170// ------------------------------------------------------------------
171// ciObject::should_be_constant()
172bool ciObject::should_be_constant() {
173  if (ScavengeRootsInCode >= 2)  return true;  // force everybody to be a constant
174  if (is_null_object()) return true;
175
176  ciEnv* env = CURRENT_ENV;
177
178    // We want Strings and Classes to be embeddable by default since
179    // they used to be in the perm world.  Not all Strings used to be
180    // embeddable but there's no easy way to distinguish the interned
181    // from the regulars ones so just treat them all that way.
182    if (klass() == env->String_klass() || klass() == env->Class_klass()) {
183      return true;
184    }
185  if (klass()->is_subclass_of(env->MethodHandle_klass()) ||
186      klass()->is_subclass_of(env->CallSite_klass())) {
187    assert(ScavengeRootsInCode >= 1, "must be");
188    // We want to treat these aggressively.
189    return true;
190  }
191
192  return handle() == NULL;
193}
194
195// ------------------------------------------------------------------
196// ciObject::should_be_constant()
197void ciObject::init_flags_from(oop x) {
198  int flags = 0;
199  if (x != NULL) {
200    assert(Universe::heap()->is_in_reserved(x), "must be");
201    if (x->is_scavengable())
202      flags |= SCAVENGABLE_FLAG;
203  }
204  _ident |= flags;
205}
206
207// ------------------------------------------------------------------
208// ciObject::print
209//
210// Print debugging output about this ciObject.
211//
212// Implementation note: dispatch to the virtual print_impl behavior
213// for this ciObject.
214void ciObject::print(outputStream* st) {
215  st->print("<%s", type_string());
216  GUARDED_VM_ENTRY(print_impl(st);)
217  st->print(" ident=%d %s address=" INTPTR_FORMAT ">", ident(),
218        is_scavengable() ? "SCAVENGABLE" : "",
219        p2i((address)this));
220}
221
222// ------------------------------------------------------------------
223// ciObject::print_oop
224//
225// Print debugging output about the oop this ciObject represents.
226void ciObject::print_oop(outputStream* st) {
227  if (is_null_object()) {
228    st->print_cr("NULL");
229  } else if (!is_loaded()) {
230    st->print_cr("UNLOADED");
231  } else {
232    GUARDED_VM_ENTRY(get_oop()->print_on(st);)
233  }
234}
235