1 /* 2 * Copyright (c) 2019, 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 #ifndef SHARE_GC_SHARED_SCAVENGABLENMETHODDATAS_HPP 26 #define SHARE_GC_SHARED_SCAVENGABLENMETHODDATAS_HPP 27 28 #include "memory/allocation.hpp" 29 #include "utilities/globalDefinitions.hpp" 30 31 class nmethod; 32 33 class ScavengableNMethodsData : public CHeapObj<mtGC> { 34 // State bits put into the two lower alignment bits. 35 static const uintptr_t state_bits = 2; 36 static const uintptr_t state_mask = (1 << state_bits) - 1; 37 static const uintptr_t state_on_list = 0x1; 38 static const uintptr_t state_marked = 0x2; 39 40 // nmethod containing the GC data. 41 nmethod* const _nm; 42 43 // The data is stored as a bit pattern in a void* inside the nmethod. data() const44 uintptr_t data() const { return reinterpret_cast<uintptr_t>(_nm->gc_data<void>()); } set_data(uintptr_t data) const45 void set_data(uintptr_t data) const { _nm->set_gc_data(reinterpret_cast<void*>(data)); } 46 state() const47 jbyte state() const { return data() & state_mask; } set_state(jbyte state) const48 void set_state(jbyte state) const { set_data((data() & ~state_mask) | state); } 49 from_nmethod(nmethod * nm) const50 uintptr_t from_nmethod(nmethod* nm) const { return reinterpret_cast<uintptr_t>(nm); } to_nmethod(uintptr_t data) const51 nmethod* to_nmethod(uintptr_t data) const { return reinterpret_cast<nmethod*>(data); } 52 53 public: ScavengableNMethodsData(nmethod * nm)54 ScavengableNMethodsData(nmethod* nm) : _nm(nm) { 55 assert(is_aligned(nm, 4), "Must be aligned to fit state bits"); 56 } 57 58 // Scavengable oop support on_list() const59 bool on_list() const { return (state() & state_on_list) != 0; } set_on_list()60 void set_on_list() { set_state(state_on_list); } clear_on_list()61 void clear_on_list() { set_state(0); } 62 63 #ifndef PRODUCT set_marked()64 void set_marked() { set_state(state() | state_marked); } clear_marked()65 void clear_marked() { set_state(state() & ~state_marked); } not_marked()66 bool not_marked() { return (state() & ~state_on_list) == 0; } 67 // N.B. there is no positive marked query, and we only use the not_marked query for asserts. 68 #endif //PRODUCT 69 next() const70 nmethod* next() const { return to_nmethod(data() & ~state_mask); } set_next(nmethod * n)71 void set_next(nmethod *n) { set_data(from_nmethod(n) | state()); } 72 }; 73 74 #endif // SHARE_GC_SHARED_SCAVENGABLENMETHODDATAS_HPP 75