1 /*
2 * Copyright (c) 1999, 2018, 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 #include "runtime/jniHandles.inline.hpp"
31
32 // ciObject
33 //
34 // This class represents an oop in the HotSpot virtual machine.
35 // Its subclasses are structured in a hierarchy which mirrors
36 // an aggregate of the VM's oop and klass hierarchies (see
37 // oopHierarchy.hpp). Each instance of ciObject holds a handle
38 // to a corresponding oop on the VM side and provides routines
39 // for accessing the information in its oop. By using the ciObject
40 // hierarchy for accessing oops in the VM, the compiler ensures
41 // that it is safe with respect to garbage collection; that is,
42 // GC and compilation can proceed independently without
43 // interference.
44 //
45 // Within the VM, the oop and klass hierarchies are separate.
46 // The compiler interface does not preserve this separation --
47 // the distinction between `Klass*' and `Klass' are not
48 // reflected in the interface and instead the Klass hierarchy
49 // is directly modeled as the subclasses of ciKlass.
50
51 // ------------------------------------------------------------------
52 // ciObject::ciObject
53 ciObject::ciObject(oop o) {
54 ASSERT_IN_VM;
55 if (ciObjectFactory::is_initialized()) {
56 _handle = JNIHandles::make_local(o);
57 } else {
58 Handle obj(Thread::current(), o);
59 _handle = JNIHandles::make_global(obj);
60 }
61 _klass = NULL;
62 init_flags_from(o);
63 }
64
65 // ------------------------------------------------------------------
66 // ciObject::ciObject
67 //
68 ciObject::ciObject(Handle h) {
69 ASSERT_IN_VM;
70 if (ciObjectFactory::is_initialized()) {
71 _handle = JNIHandles::make_local(h());
72 } else {
73 _handle = JNIHandles::make_global(h);
74 }
75 _klass = NULL;
76 init_flags_from(h());
77 }
78
79 // ------------------------------------------------------------------
80 // ciObject::ciObject
81 //
82 // Unloaded klass/method variant. `klass' is the klass of the unloaded
83 // klass/method, if that makes sense.
84 ciObject::ciObject(ciKlass* klass) {
85 ASSERT_IN_VM;
86 assert(klass != NULL, "must supply klass");
87 _handle = NULL;
88 _klass = klass;
89 }
90
91 // ------------------------------------------------------------------
92 // ciObject::ciObject
93 //
94 // NULL variant. Used only by ciNullObject.
95 ciObject::ciObject() {
96 ASSERT_IN_VM;
97 _handle = NULL;
98 _klass = NULL;
99 }
100
101 // ------------------------------------------------------------------
102 // ciObject::get_oop
103 //
104 // Get the oop of this ciObject.
105 oop ciObject::get_oop() const {
106 return JNIHandles::resolve_non_null(_handle);
107 }
108
109 // ------------------------------------------------------------------
110 // ciObject::klass
111 //
112 // Get the ciKlass of this ciObject.
113 ciKlass* ciObject::klass() {
114 if (_klass == NULL) {
115 if (_handle == NULL) {
116 // When both _klass and _handle are NULL, we are dealing
117 // with the distinguished instance of ciNullObject.
118 // No one should ask it for its klass.
119 assert(is_null_object(), "must be null object");
120 ShouldNotReachHere();
121 return NULL;
122 }
123
124 GUARDED_VM_ENTRY(
125 oop o = get_oop();
126 _klass = CURRENT_ENV->get_klass(o->klass());
127 );
128 }
129 return _klass;
130 }
131
132 // ------------------------------------------------------------------
133 // ciObject::equals
134 //
135 // Are two ciObjects equal?
136 bool ciObject::equals(ciObject* obj) {
137 return (this == obj);
138 }
139
140 // ------------------------------------------------------------------
141 // ciObject::hash
142 //
143 // A hash value for the convenience of compilers.
144 //
145 // Implementation note: we use the address of the ciObject as the
146 // basis for the hash. Use the _ident field, which is well-behaved.
147 int ciObject::hash() {
148 return ident() * 31;
149 }
150
151 // ------------------------------------------------------------------
152 // ciObject::constant_encoding
153 //
154 // The address which the compiler should embed into the
155 // generated code to represent this oop. This address
156 // is not the true address of the oop -- it will get patched
157 // during nmethod creation.
158 //
159 //
160 //
161 // Implementation note: we use the handle as the encoding. The
162 // nmethod constructor resolves the handle and patches in the oop.
163 //
164 // This method should be changed to return an generified address
165 // to discourage use of the JNI handle.
166 jobject ciObject::constant_encoding() {
167 assert(is_null_object() || handle() != NULL, "cannot embed null pointer");
168 assert(can_be_constant(), "oop must be NULL or perm");
169 return handle();
170 }
171
172 // ------------------------------------------------------------------
173 // ciObject::can_be_constant
174 bool ciObject::can_be_constant() {
175 if (ScavengeRootsInCode >= 1) return true; // now everybody can encode as a constant
176 return handle() == NULL;
177 }
178
179 // ------------------------------------------------------------------
180 // ciObject::should_be_constant()
181 bool ciObject::should_be_constant() {
182 if (ScavengeRootsInCode >= 2) return true; // force everybody to be a constant
183 if (is_null_object()) return true;
184
185 ciEnv* env = CURRENT_ENV;
186
187 // We want Strings and Classes to be embeddable by default since
188 // they used to be in the perm world. Not all Strings used to be
189 // embeddable but there's no easy way to distinguish the interned
190 // from the regulars ones so just treat them all that way.
191 if (klass() == env->String_klass() || klass() == env->Class_klass()) {
192 return true;
193 }
194 if (klass()->is_subclass_of(env->MethodHandle_klass()) ||
195 klass()->is_subclass_of(env->CallSite_klass())) {
196 assert(ScavengeRootsInCode >= 1, "must be");
197 // We want to treat these aggressively.
198 return true;
199 }
200
201 return handle() == NULL;
202 }
203
204 // ------------------------------------------------------------------
205 // ciObject::should_be_constant()
206 void ciObject::init_flags_from(oop x) {
207 int flags = 0;
208 if (x != NULL) {
209 assert(Universe::heap()->is_in_reserved(x), "must be");
210 if (x->is_scavengable())
211 flags |= SCAVENGABLE_FLAG;
212 }
213 _ident |= flags;
214 }
215
216 // ------------------------------------------------------------------
217 // ciObject::print
218 //
219 // Print debugging output about this ciObject.
220 //
221 // Implementation note: dispatch to the virtual print_impl behavior
222 // for this ciObject.
223 void ciObject::print(outputStream* st) {
224 st->print("<%s", type_string());
225 GUARDED_VM_ENTRY(print_impl(st);)
226 st->print(" ident=%d %s address=" INTPTR_FORMAT ">", ident(),
227 is_scavengable() ? "SCAVENGABLE" : "",
228 p2i((address)this));
229 }
230
231 // ------------------------------------------------------------------
232 // ciObject::print_oop
233 //
234 // Print debugging output about the oop this ciObject represents.
235 void ciObject::print_oop(outputStream* st) {
236 if (is_null_object()) {
237 st->print_cr("NULL");
238 } else if (!is_loaded()) {
239 st->print_cr("UNLOADED");
240 } else {
241 GUARDED_VM_ENTRY(get_oop()->print_on(st);)
242 }
243 }