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
52 ciObject::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 //
67 ciObject::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.
83 ciObject::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.
94 ciObject::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.
104 ciKlass* 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?
127 bool 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.
138 int 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.
157 jobject 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
165 bool 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()
172 bool 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()
197 void ciObject::init_flags_from(oop x) {
198 int flags = 0;
199 if (x != NULL) {
200 assert(GC::gc()->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.
214 void 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.
226 void 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 }