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 void CardTableBarrierSetC2::clone(GraphKit* kit, Node* src, Node* dst, Node* size, bool is_array) const { 129 BarrierSetC2::clone(kit, src, dst, size, is_array); 130 const TypePtr* raw_adr_type = TypeRawPtr::BOTTOM; 131 132 // If necessary, emit some card marks afterwards. (Non-arrays only.) 133 bool card_mark = !is_array && !use_ReduceInitialCardMarks(); 134 if (card_mark) { 135 assert(!is_array, ""); 136 // Put in store barrier for any and all oops we are sticking 137 // into this object. (We could avoid this if we could prove 138 // that the object type contains no oop fields at all.) 139 Node* no_particular_value = nullptr; 140 Node* no_particular_field = nullptr; 141 int raw_adr_idx = Compile::AliasIdxRaw; 142 post_barrier(kit, kit->control(), 143 kit->memory(raw_adr_type), 144 dst, 145 no_particular_field, 146 raw_adr_idx, 147 no_particular_value, 148 T_OBJECT, 149 false); 150 } 151 } 152 153 bool CardTableBarrierSetC2::use_ReduceInitialCardMarks() const { 154 return ReduceInitialCardMarks; 155 } 156 157 bool CardTableBarrierSetC2::is_gc_barrier_node(Node* node) const { 158 return ModRefBarrierSetC2::is_gc_barrier_node(node) || node->Opcode() == Op_StoreCM; 159 } 160 161 void CardTableBarrierSetC2::eliminate_gc_barrier(PhaseIterGVN* igvn, Node* node) const { 162 assert(node->Opcode() == Op_CastP2X, "ConvP2XNode required"); 163 for (DUIterator_Last imin, i = node->last_outs(imin); i >= imin; --i) { 164 Node* shift = node->last_out(i); 165 for (DUIterator_Last jmin, j = shift->last_outs(jmin); j >= jmin; --j) { 166 Node* addp = shift->last_out(j); 167 for (DUIterator_Last kmin, k = addp->last_outs(kmin); k >= kmin; --k) { 168 Node* mem = addp->last_out(k); 169 if (UseCondCardMark && mem->is_Load()) { 170 assert(mem->Opcode() == Op_LoadB, "unexpected code shape"); 171 // The load is checking if the card has been written so 172 // replace it with zero to fold the test. 173 igvn->replace_node(mem, igvn->intcon(0)); 174 continue; 175 } 176 assert(mem->is_Store(), "store required"); 177 igvn->replace_node(mem, mem->in(MemNode::Memory)); 178 } 179 } 180 } 181 } 182 183 bool CardTableBarrierSetC2::array_copy_requires_gc_barriers(bool tightly_coupled_alloc, BasicType type, bool is_clone, bool is_clone_instance, ArrayCopyPhase phase) const { 184 bool is_oop = type == T_OBJECT || type == T_ARRAY; 185 return is_oop && (!tightly_coupled_alloc || !use_ReduceInitialCardMarks()); 186 }