1 /*
2 * Copyright (c) 2018, 2023, 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/ciUtilities.hpp"
27 #include "gc/shared/cardTable.hpp"
28 #include "gc/shared/cardTableBarrierSet.hpp"
29 #include "gc/shared/c2/cardTableBarrierSetC2.hpp"
30 #include "gc/shared/gc_globals.hpp"
31 #include "opto/arraycopynode.hpp"
32 #include "opto/graphKit.hpp"
33 #include "opto/idealKit.hpp"
34 #include "opto/macro.hpp"
35 #include "utilities/macros.hpp"
36
37 #define __ ideal.
38
39 Node* CardTableBarrierSetC2::byte_map_base_node(GraphKit* kit) const {
40 // Get base of card map
41 CardTable::CardValue* card_table_base = ci_card_table_address();
42 if (card_table_base != nullptr) {
43 return kit->makecon(TypeRawPtr::make((address)card_table_base));
44 } else {
45 return kit->null();
46 }
47 }
48
49 // vanilla post barrier
50 // Insert a write-barrier store. This is to let generational GC work; we have
51 // to flag all oop-stores before the next GC point.
52 void CardTableBarrierSetC2::post_barrier(GraphKit* kit,
53 Node* ctl,
54 Node* oop_store,
55 Node* obj,
56 Node* adr,
57 uint adr_idx,
58 Node* val,
59 BasicType bt,
60 bool use_precise) const {
61 // No store check needed if we're storing a null.
62 if (val != nullptr && val->is_Con()) {
63 const Type* t = val->bottom_type();
64 if (t == TypePtr::NULL_PTR || t == Type::TOP) {
65 return;
66 }
67 }
68
69 if (use_ReduceInitialCardMarks()
70 && obj == kit->just_allocated_object(kit->control())) {
71 // We can skip marks on a freshly-allocated object in Eden.
72 // Keep this code in sync with CardTableBarrierSet::on_slowpath_allocation_exit.
73 // That routine informs GC to take appropriate compensating steps,
74 // upon a slow-path allocation, so as to make this card-mark
75 // elision safe.
76 return;
77 }
78
79 if (!use_precise) {
80 // All card marks for a (non-array) instance are in one place:
81 adr = obj;
82 } else {
83 // Else it's an array (or unknown), and we want more precise card marks.
84 }
85
86 assert(adr != nullptr, "");
87
88 IdealKit ideal(kit, true);
89
90 // Convert the pointer to an int prior to doing math on it
91 Node* cast = __ CastPX(__ ctrl(), adr);
92
93 // Divide by card size
94 Node* card_offset = __ URShiftX(cast, __ ConI(CardTable::card_shift()));
95
96 // Combine card table base and card offset
97 Node* card_adr = __ AddP(__ top(), byte_map_base_node(kit), card_offset);
98
99 // Get the alias_index for raw card-mark memory
100 int adr_type = Compile::AliasIdxRaw;
101
102 // Dirty card value to store
103 Node* dirty = __ ConI(CardTable::dirty_card_val());
104
105 if (UseCondCardMark) {
106 // The classic GC reference write barrier is typically implemented
107 // as a store into the global card mark table. Unfortunately
108 // unconditional stores can result in false sharing and excessive
109 // coherence traffic as well as false transactional aborts.
110 // UseCondCardMark enables MP "polite" conditional card mark
111 // stores. In theory we could relax the load from ctrl() to
112 // no_ctrl, but that doesn't buy much latitude.
113 Node* card_val = __ load( __ ctrl(), card_adr, TypeInt::BYTE, T_BYTE, adr_type);
114 __ if_then(card_val, BoolTest::ne, dirty);
115 }
116
117 // Smash dirty value into card
118 __ store(__ ctrl(), card_adr, dirty, T_BYTE, adr_type, MemNode::unordered);
119
120 if (UseCondCardMark) {
121 __ end_if();
122 }
123
124 // Final sync IdealKit and GraphKit.
125 kit->final_sync(ideal);
126 }
127
128 bool CardTableBarrierSetC2::use_ReduceInitialCardMarks() const {
129 return ReduceInitialCardMarks;
130 }
131
132 void CardTableBarrierSetC2::eliminate_gc_barrier(PhaseMacroExpand* macro, Node* node) const {
133 assert(node->Opcode() == Op_CastP2X, "ConvP2XNode required");
134 Node *shift = node->unique_out();
135 Node *addp = shift->unique_out();
136 for (DUIterator_Last jmin, j = addp->last_outs(jmin); j >= jmin; --j) {
137 Node *mem = addp->last_out(j);
138 if (UseCondCardMark && mem->is_Load()) {
139 assert(mem->Opcode() == Op_LoadB, "unexpected code shape");
140 // The load is checking if the card has been written so
141 // replace it with zero to fold the test.
142 macro->replace_node(mem, macro->intcon(0));
143 continue;
144 }
145 assert(mem->is_Store(), "store required");
146 macro->replace_node(mem, mem->in(MemNode::Memory));
147 }
148 }
149
150 bool CardTableBarrierSetC2::array_copy_requires_gc_barriers(bool tightly_coupled_alloc, BasicType type, bool is_clone, bool is_clone_instance, ArrayCopyPhase phase) const {
151 bool is_oop = is_reference_type(type);
152 return is_oop && (!tightly_coupled_alloc || !use_ReduceInitialCardMarks());
153 }