1 /*
2 * Copyright (c) 2021, 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 #ifndef SHARE_GC_SHARED_SLIDINGFORWARDING_INLINE_HPP
25 #define SHARE_GC_SHARED_SLIDINGFORWARDING_INLINE_HPP
26
27 #include "gc/shared/slidingForwarding.hpp"
28 #include "oops/markWord.hpp"
29 #include "oops/oop.inline.hpp"
30
31 #ifdef _LP64
32 size_t SlidingForwarding::region_index_containing(HeapWord* addr) const {
33 assert(addr >= _heap_start, "sanity: addr: " PTR_FORMAT " heap base: " PTR_FORMAT, p2i(addr), p2i(_heap_start));
34 size_t index = ((size_t) (addr - _heap_start)) >> _region_size_words_shift;
35 assert(index < _num_regions, "Region index is in bounds: " PTR_FORMAT, p2i(addr));
36 return index;
37 }
38
39 bool SlidingForwarding::region_contains(HeapWord* region_base, HeapWord* addr) const {
40 return uintptr_t(addr - region_base) < (ONE << _region_size_words_shift);
41 }
42
43
44 uintptr_t SlidingForwarding::encode_forwarding(HeapWord* original, HeapWord* target) {
45 size_t orig_idx = region_index_containing(original);
46 size_t base_table_idx = orig_idx * 2;
47 size_t target_idx = region_index_containing(target);
48 HeapWord* encode_base;
49 uintptr_t region_idx;
50 for (region_idx = 0; region_idx < NUM_REGIONS; region_idx++) {
51 encode_base = _target_base_table[base_table_idx + region_idx];
52 if (encode_base == UNUSED_BASE) {
53 encode_base = _heap_start + target_idx * (ONE << _region_size_words_shift);
54 _target_base_table[base_table_idx + region_idx] = encode_base;
55 break;
56 } else if (region_contains(encode_base, target)) {
57 break;
58 }
59 }
60 if (region_idx >= NUM_REGIONS) {
61 tty->print_cr("target: " PTR_FORMAT, p2i(target));
62 for (region_idx = 0; region_idx < NUM_REGIONS; region_idx++) {
63 tty->print_cr("region_idx: " INTPTR_FORMAT ", encode_base: " PTR_FORMAT, region_idx, p2i(_target_base_table[base_table_idx + region_idx]));
64 }
65 }
66 assert(region_idx < NUM_REGIONS, "need to have found an encoding base");
67 assert(target >= encode_base, "target must be above encode base, target:" PTR_FORMAT ", encoded_base: " PTR_FORMAT ", target_idx: " SIZE_FORMAT ", heap start: " PTR_FORMAT ", region_idx: " INTPTR_FORMAT,
68 p2i(target), p2i(encode_base), target_idx, p2i(_heap_start), region_idx);
69 assert(region_contains(encode_base, target), "region must contain target: original: " PTR_FORMAT ", target: " PTR_FORMAT ", encode_base: " PTR_FORMAT ", region_idx: " INTPTR_FORMAT, p2i(original), p2i(target), p2i(encode_base), region_idx);
70 uintptr_t encoded = (((uintptr_t)(target - encode_base)) << COMPRESSED_BITS_SHIFT) |
71 (region_idx << BASE_SHIFT) | markWord::marked_value;
72 assert(target == decode_forwarding(original, encoded), "must be reversible");
73 return encoded;
74 }
75
76 HeapWord* SlidingForwarding::decode_forwarding(HeapWord* original, uintptr_t encoded) const {
77 assert((encoded & markWord::marked_value) == markWord::marked_value, "must be marked as forwarded");
78 size_t orig_idx = region_index_containing(original);
79 size_t region_idx = (encoded >> BASE_SHIFT) & right_n_bits(NUM_REGION_BITS);
80 size_t base_table_idx = orig_idx * 2 + region_idx;
81 HeapWord* decoded = _target_base_table[base_table_idx] + (encoded >> COMPRESSED_BITS_SHIFT);
82 assert(decoded >= _heap_start, "must be above heap start, encoded: " INTPTR_FORMAT ", region_idx: " SIZE_FORMAT ", base: " PTR_FORMAT, encoded, region_idx, p2i(_target_base_table[base_table_idx]));
83 return decoded;
84 }
85 #endif
86
87 void SlidingForwarding::forward_to(oop original, oop target) {
88 #ifdef _LP64
89 markWord header = original->mark();
90 if (header.has_displaced_mark_helper()) {
91 header = header.displaced_mark_helper();
92 }
93 uintptr_t encoded = encode_forwarding(cast_from_oop<HeapWord*>(original), cast_from_oop<HeapWord*>(target));
94 assert((encoded & markWord::klass_mask_in_place) == 0, "encoded forwardee must not overlap with Klass*: " PTR_FORMAT, encoded);
95 header = markWord((header.value() & markWord::klass_mask_in_place) | encoded);
96 original->set_mark(header);
97 #else
98 original->forward_to(target);
99 #endif
100 }
101
102 oop SlidingForwarding::forwardee(oop original) const {
103 #ifdef _LP64
104 markWord header = original->mark();
105 uintptr_t encoded = header.value() & ~markWord::klass_mask_in_place;
106 HeapWord* forwardee = decode_forwarding(cast_from_oop<HeapWord*>(original), encoded);
107 return cast_to_oop(forwardee);
108 #else
109 return original->forwardee();
110 #endif
111 }
112
113 #endif // SHARE_GC_SHARED_SLIDINGFORWARDING_INLINE_HPP