1 /* 2 * Copyright (c) 1999, 2015, 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_interface/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 = JNIHandles::make_global(o); 58 } 59 _klass = NULL; 60 init_flags_from(o); 61 } 62 63 // ------------------------------------------------------------------ 64 // ciObject::ciObject 65 // 66 ciObject::ciObject(Handle h) { 67 ASSERT_IN_VM; 68 if (ciObjectFactory::is_initialized()) { 69 _handle = JNIHandles::make_local(h()); 70 } else { 71 _handle = JNIHandles::make_global(h); 72 } 73 _klass = NULL; 74 init_flags_from(h()); 75 } 76 77 // ------------------------------------------------------------------ 78 // ciObject::ciObject 79 // 80 // Unloaded klass/method variant. `klass' is the klass of the unloaded 81 // klass/method, if that makes sense. 82 ciObject::ciObject(ciKlass* klass) { 83 ASSERT_IN_VM; 84 assert(klass != NULL, "must supply klass"); 85 _handle = NULL; 86 _klass = klass; 87 } 88 89 // ------------------------------------------------------------------ 90 // ciObject::ciObject 91 // 92 // NULL variant. Used only by ciNullObject. 93 ciObject::ciObject() { 94 ASSERT_IN_VM; 95 _handle = NULL; 96 _klass = NULL; 97 } 98 99 // ------------------------------------------------------------------ 100 // ciObject::klass 101 // 102 // Get the ciKlass of this ciObject. 103 ciKlass* ciObject::klass() { 104 if (_klass == NULL) { 105 if (_handle == NULL) { 106 // When both _klass and _handle are NULL, we are dealing 107 // with the distinguished instance of ciNullObject. 108 // No one should ask it for its klass. 109 assert(is_null_object(), "must be null object"); 110 ShouldNotReachHere(); 111 return NULL; 112 } 113 114 GUARDED_VM_ENTRY( 115 oop o = get_oop(); 116 _klass = CURRENT_ENV->get_klass(o->klass()); 117 ); 118 } 119 return _klass; 120 } 121 122 // ------------------------------------------------------------------ 123 // ciObject::equals 124 // 125 // Are two ciObjects equal? 126 bool ciObject::equals(ciObject* obj) { 127 return (this == obj); 128 } 129 130 // ------------------------------------------------------------------ 131 // ciObject::hash 132 // 133 // A hash value for the convenience of compilers. 134 // 135 // Implementation note: we use the address of the ciObject as the 136 // basis for the hash. Use the _ident field, which is well-behaved. 137 int ciObject::hash() { 138 return ident() * 31; 139 } 140 141 // ------------------------------------------------------------------ 142 // ciObject::constant_encoding 143 // 144 // The address which the compiler should embed into the 145 // generated code to represent this oop. This address 146 // is not the true address of the oop -- it will get patched 147 // during nmethod creation. 148 // 149 // 150 // 151 // Implementation note: we use the handle as the encoding. The 152 // nmethod constructor resolves the handle and patches in the oop. 153 // 154 // This method should be changed to return an generified address 155 // to discourage use of the JNI handle. 156 jobject ciObject::constant_encoding() { 157 assert(is_null_object() || handle() != NULL, "cannot embed null pointer"); 158 assert(can_be_constant(), "oop must be NULL or perm"); 159 return handle(); 160 } 161 162 // ------------------------------------------------------------------ 163 // ciObject::can_be_constant 164 bool ciObject::can_be_constant() { 165 if (ScavengeRootsInCode >= 1) return true; // now everybody can encode as a constant 166 return handle() == NULL; 167 } 168 169 // ------------------------------------------------------------------ 170 // ciObject::should_be_constant() 171 bool ciObject::should_be_constant() { 172 if (ScavengeRootsInCode >= 2) return true; // force everybody to be a constant 173 if (is_null_object()) return true; 174 175 ciEnv* env = CURRENT_ENV; 176 177 // We want Strings and Classes to be embeddable by default since 178 // they used to be in the perm world. Not all Strings used to be 179 // embeddable but there's no easy way to distinguish the interned 180 // from the regulars ones so just treat them all that way. 181 if (klass() == env->String_klass() || klass() == env->Class_klass()) { 182 return true; 183 } 184 if (klass()->is_subclass_of(env->MethodHandle_klass()) || 185 klass()->is_subclass_of(env->CallSite_klass())) { 186 assert(ScavengeRootsInCode >= 1, "must be"); 187 // We want to treat these aggressively. 188 return true; 189 } 190 191 return handle() == NULL; 192 } 193 194 // ------------------------------------------------------------------ 195 // ciObject::should_be_constant() 196 void ciObject::init_flags_from(oop x) { 197 int flags = 0; 198 if (x != NULL) { 199 assert(Universe::heap()->is_in_reserved(x), "must be"); 200 if (x->is_scavengable()) 201 flags |= SCAVENGABLE_FLAG; 202 } 203 _ident |= flags; 204 } 205 206 // ------------------------------------------------------------------ 207 // ciObject::print 208 // 209 // Print debugging output about this ciObject. 210 // 211 // Implementation note: dispatch to the virtual print_impl behavior 212 // for this ciObject. 213 void ciObject::print(outputStream* st) { 214 st->print("<%s", type_string()); 215 GUARDED_VM_ENTRY(print_impl(st);) 216 st->print(" ident=%d %s address=" INTPTR_FORMAT ">", ident(), 217 is_scavengable() ? "SCAVENGABLE" : "", 218 p2i((address)this)); 219 } 220 221 // ------------------------------------------------------------------ 222 // ciObject::print_oop 223 // 224 // Print debugging output about the oop this ciObject represents. 225 void ciObject::print_oop(outputStream* st) { 226 if (is_null_object()) { 227 st->print_cr("NULL"); 228 } else if (!is_loaded()) { 229 st->print_cr("UNLOADED"); 230 } else { 231 GUARDED_VM_ENTRY(get_oop()->print_on(st);) 232 } 233 }