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