1 /* 2 * Copyright (c) 2015, 2019, Red Hat, Inc. 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 #ifndef SHARE_GC_SHENANDOAH_SHENANDOAHFORWARDING_INLINE_HPP 26 #define SHARE_GC_SHENANDOAH_SHENANDOAHFORWARDING_INLINE_HPP 27 28 #include "gc/shenandoah/shenandoahForwarding.hpp" 29 30 #include "gc/shenandoah/shenandoahAsserts.hpp" 31 #include "oops/markWord.hpp" 32 #include "runtime/javaThread.hpp" 33 #include "runtime/synchronizer.hpp" 34 35 inline oop ShenandoahForwarding::get_forwardee_raw(oop obj) { 36 shenandoah_assert_in_heap(nullptr, obj); 37 return get_forwardee_raw_unchecked(obj); 38 } 39 40 inline oop ShenandoahForwarding::get_forwardee_raw_unchecked(oop obj) { 41 // JVMTI and JFR code use mark words for marking objects for their needs. 42 // On this path, we can encounter the "marked" object, but with null 43 // fwdptr. That object is still not forwarded, and we need to return 44 // the object itself. 45 markWord mark = obj->mark(); 46 if (mark.is_marked()) { 47 HeapWord* fwdptr = (HeapWord*) mark.clear_lock_bits().to_pointer(); 48 if (fwdptr != nullptr) { 49 return cast_to_oop(fwdptr); 50 } 51 } 52 return obj; 53 } 54 55 inline oop ShenandoahForwarding::get_forwardee_mutator(oop obj) { 56 // Same as above, but mutator thread cannot ever see null forwardee. 57 shenandoah_assert_correct(nullptr, obj); 58 assert(Thread::current()->is_Java_thread(), "Must be a mutator thread"); 59 60 markWord mark = obj->mark(); 61 if (mark.is_marked()) { 62 HeapWord* fwdptr = (HeapWord*) mark.clear_lock_bits().to_pointer(); 63 assert(fwdptr != nullptr, "Forwarding pointer is never null here"); 64 return cast_to_oop(fwdptr); 65 } else { 66 return obj; 67 } 68 } 69 70 inline oop ShenandoahForwarding::get_forwardee(oop obj) { 71 shenandoah_assert_correct(nullptr, obj); 72 return get_forwardee_raw_unchecked(obj); 73 } 74 75 inline bool ShenandoahForwarding::is_forwarded(oop obj) { 76 return obj->mark().is_marked(); 77 } 78 79 inline oop ShenandoahForwarding::try_update_forwardee(oop obj, oop update) { 80 markWord old_mark = obj->mark(); 81 if (old_mark.is_marked()) { 82 return cast_to_oop(old_mark.clear_lock_bits().to_pointer()); 83 } 84 85 markWord new_mark = markWord::encode_pointer_as_mark(update); 86 markWord prev_mark = obj->cas_set_mark(new_mark, old_mark, memory_order_conservative); 87 if (prev_mark == old_mark) { 88 return update; 89 } else { 90 assert(prev_mark.is_marked(), "must be forwarded"); 91 return cast_to_oop(prev_mark.clear_lock_bits().to_pointer()); 92 } 93 } 94 95 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHFORWARDING_INLINE_HPP