1 /*
  2  * Copyright (c) 2018, 2025, 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 "ci/ciUtilities.hpp"
 26 #include "code/aotCodeCache.hpp"
 27 #include "gc/shared/c2/cardTableBarrierSetC2.hpp"
 28 #include "gc/shared/cardTable.hpp"
 29 #include "gc/shared/cardTableBarrierSet.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::store_at_resolved(C2Access& access, C2AccessValue& val) const {
 40   DecoratorSet decorators = access.decorators();
 41 
 42   Node* adr = access.addr().node();
 43 
 44   bool is_array = (decorators & IS_ARRAY) != 0;
 45   bool anonymous = (decorators & ON_UNKNOWN_OOP_REF) != 0;
 46   bool in_heap = (decorators & IN_HEAP) != 0;
 47   bool use_precise = is_array || anonymous;
 48   bool tightly_coupled_alloc = (decorators & C2_TIGHTLY_COUPLED_ALLOC) != 0;
 49 
 50   if (!access.is_oop() || tightly_coupled_alloc || (!in_heap && !anonymous)) {
 51     return BarrierSetC2::store_at_resolved(access, val);
 52   }
 53 
 54   assert(access.is_parse_access(), "entry not supported at optimization time");
 55   C2ParseAccess& parse_access = static_cast<C2ParseAccess&>(access);
 56 
 57   Node* store = BarrierSetC2::store_at_resolved(access, val);
 58   post_barrier(parse_access.kit(), access.base(), adr, val.node(), use_precise);
 59 
 60   return store;
 61 }
 62 
 63 Node* CardTableBarrierSetC2::atomic_cmpxchg_val_at_resolved(C2AtomicParseAccess& access, Node* expected_val,
 64                                                             Node* new_val, const Type* value_type) const {
 65   if (!access.is_oop()) {
 66     return BarrierSetC2::atomic_cmpxchg_val_at_resolved(access, expected_val, new_val, value_type);
 67   }
 68 
 69   Node* result = BarrierSetC2::atomic_cmpxchg_val_at_resolved(access, expected_val, new_val, value_type);
 70 
 71   post_barrier(access.kit(), access.base(), access.addr().node(), new_val, true);
 72 
 73   return result;
 74 }
 75 
 76 Node* CardTableBarrierSetC2::atomic_cmpxchg_bool_at_resolved(C2AtomicParseAccess& access, Node* expected_val,
 77                                                              Node* new_val, const Type* value_type) const {
 78   GraphKit* kit = access.kit();
 79 
 80   if (!access.is_oop()) {
 81     return BarrierSetC2::atomic_cmpxchg_bool_at_resolved(access, expected_val, new_val, value_type);
 82   }
 83 
 84   Node* load_store = BarrierSetC2::atomic_cmpxchg_bool_at_resolved(access, expected_val, new_val, value_type);
 85 
 86   // Emit the post barrier only when the actual store happened. This makes sense
 87   // to check only for LS_cmp_* that can fail to set the value.
 88   // LS_cmp_exchange does not produce any branches by default, so there is no
 89   // boolean result to piggyback on. TODO: When we merge CompareAndSwap with
 90   // CompareAndExchange and move branches here, it would make sense to conditionalize
 91   // post_barriers for LS_cmp_exchange as well.
 92   //
 93   // CAS success path is marked more likely since we anticipate this is a performance
 94   // critical path, while CAS failure path can use the penalty for going through unlikely
 95   // path as backoff. Which is still better than doing a store barrier there.
 96   IdealKit ideal(kit);
 97   ideal.if_then(load_store, BoolTest::ne, ideal.ConI(0), PROB_STATIC_FREQUENT); {
 98     kit->sync_kit(ideal);
 99     post_barrier(kit, access.base(), access.addr().node(), new_val, true);
100     ideal.sync_kit(kit);
101   } ideal.end_if();
102   kit->final_sync(ideal);
103 
104   return load_store;
105 }
106 
107 Node* CardTableBarrierSetC2::atomic_xchg_at_resolved(C2AtomicParseAccess& access, Node* new_val, const Type* value_type) const {
108   Node* result = BarrierSetC2::atomic_xchg_at_resolved(access, new_val, value_type);
109   if (!access.is_oop()) {
110     return result;
111   }
112 
113   post_barrier(access.kit(), access.base(), access.addr().node(), new_val, true);
114 
115   return result;
116 }
117 
118 Node* CardTableBarrierSetC2::byte_map_base_node(IdealKit* kit) const {
119   // Get base of card map
120 #if INCLUDE_CDS
121   if (AOTCodeCache::is_on_for_dump()) {
122     // load the card table address from the AOT Runtime Constants area
123     Node* byte_map_base_adr = kit->makecon(TypeRawPtr::make(AOTRuntimeConstants::card_table_address()));
124     return kit->load_aot_const(byte_map_base_adr, TypeRawPtr::NOTNULL);
125   }
126 #endif
127   CardTable::CardValue* card_table_base = ci_card_table_address_const();
128    if (card_table_base != nullptr) {
129      return kit->makecon(TypeRawPtr::make((address)card_table_base));
130    } else {
131      return kit->makecon(Type::get_zero_type(T_ADDRESS));
132    }
133 }
134 
135 // vanilla post barrier
136 // Insert a write-barrier store.  This is to let generational GC work; we have
137 // to flag all oop-stores before the next GC point.
138 void CardTableBarrierSetC2::post_barrier(GraphKit* kit,
139                                          Node* obj,
140                                          Node* adr,
141                                          Node* val,
142                                          bool use_precise) const {
143   // No store check needed if we're storing a null.
144   if (val != nullptr && val->is_Con()) {
145     const Type* t = val->bottom_type();
146     if (t == TypePtr::NULL_PTR || t == Type::TOP) {
147       return;
148     }
149   }
150 
151   if (use_ReduceInitialCardMarks()
152       && obj == kit->just_allocated_object(kit->control())) {
153     // We can skip marks on a freshly-allocated object in Eden.
154     // Keep this code in sync with CardTableBarrierSet::on_slowpath_allocation_exit.
155     // That routine informs GC to take appropriate compensating steps,
156     // upon a slow-path allocation, so as to make this card-mark
157     // elision safe.
158     return;
159   }
160 
161   if (!use_precise) {
162     // All card marks for a (non-array) instance are in one place:
163     adr = obj;
164   } else {
165     // Else it's an array (or unknown), and we want more precise card marks.
166   }
167 
168   assert(adr != nullptr, "");
169 
170   IdealKit ideal(kit, true);
171 
172   // Convert the pointer to an int prior to doing math on it
173   Node* cast = __ CastPX(__ ctrl(), adr);
174 
175   // Divide by card size
176   Node* card_offset = __ URShiftX(cast, __ ConI(CardTable::card_shift()));
177 
178   // Combine card table base and card offset
179   Node* card_adr = __ AddP(__ top(), byte_map_base_node(&ideal), card_offset);
180 
181   // Get the alias_index for raw card-mark memory
182   int adr_type = Compile::AliasIdxRaw;
183 
184   // Dirty card value to store
185   Node* dirty = __ ConI(CardTable::dirty_card_val());
186 
187   if (UseCondCardMark) {
188     // The classic GC reference write barrier is typically implemented
189     // as a store into the global card mark table.  Unfortunately
190     // unconditional stores can result in false sharing and excessive
191     // coherence traffic as well as false transactional aborts.
192     // UseCondCardMark enables MP "polite" conditional card mark
193     // stores.  In theory we could relax the load from ctrl() to
194     // no_ctrl, but that doesn't buy much latitude.
195     Node* card_val = __ load( __ ctrl(), card_adr, TypeInt::BYTE, T_BYTE, adr_type);
196     __ if_then(card_val, BoolTest::ne, dirty);
197   }
198 
199   // Smash dirty value into card
200   __ store(__ ctrl(), card_adr, dirty, T_BYTE, adr_type, MemNode::unordered);
201 
202   if (UseCondCardMark) {
203     __ end_if();
204   }
205 
206   // Final sync IdealKit and GraphKit.
207   kit->final_sync(ideal);
208 }
209 
210 bool CardTableBarrierSetC2::use_ReduceInitialCardMarks() {
211   return ReduceInitialCardMarks;
212 }
213 
214 void CardTableBarrierSetC2::eliminate_gc_barrier(PhaseMacroExpand* macro, Node* node) const {
215   assert(node->Opcode() == Op_CastP2X, "ConvP2XNode required");
216   Node *shift = node->unique_out();
217   Node *addp = shift->unique_out();
218   for (DUIterator_Last jmin, j = addp->last_outs(jmin); j >= jmin; --j) {
219     Node *mem = addp->last_out(j);
220     if (UseCondCardMark && mem->is_Load()) {
221       assert(mem->Opcode() == Op_LoadB, "unexpected code shape");
222       // The load is checking if the card has been written so
223       // replace it with zero to fold the test.
224       macro->replace_node(mem, macro->intcon(0));
225       continue;
226     }
227     assert(mem->is_Store(), "store required");
228     macro->replace_node(mem, mem->in(MemNode::Memory));
229   }
230 }
231 
232 bool CardTableBarrierSetC2::array_copy_requires_gc_barriers(bool tightly_coupled_alloc, BasicType type, bool is_clone, bool is_clone_instance, ArrayCopyPhase phase) const {
233   bool is_oop = is_reference_type(type);
234   return is_oop && (!tightly_coupled_alloc || !use_ReduceInitialCardMarks());
235 }
--- EOF ---