1 /*
   2  * Copyright (c) 2018, 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 "asm/macroAssembler.inline.hpp"
  27 #include "gc/shared/barrierSet.hpp"
  28 #include "gc/shared/cardTable.hpp"
  29 #include "gc/shared/cardTableBarrierSet.hpp"
  30 #include "gc/shared/cardTableBarrierSetAssembler.hpp"
  31 #include "gc/shared/collectedHeap.hpp"
  32 #include "runtime/globals.hpp"
  33 
  34 #define __ masm->
  35 
  36 #ifdef PRODUCT
  37 #define BLOCK_COMMENT(str) /* nothing */
  38 #else
  39 #define BLOCK_COMMENT(str) __ block_comment(str)
  40 #endif
  41 
  42 #define BIND(label) bind(label); BLOCK_COMMENT(#label ":")
  43 
  44 void CardTableBarrierSetAssembler::gen_write_ref_array_post_barrier(MacroAssembler* masm, DecoratorSet decorators,
  45                                                                     Register addr, Register count, Register tmp) {
  46   BLOCK_COMMENT("CardTablePostBarrier");
  47   BarrierSet* bs = BarrierSet::barrier_set();
  48   CardTableBarrierSet* ctbs = barrier_set_cast<CardTableBarrierSet>(bs);
  49   CardTable* ct = ctbs->card_table();
  50   assert(sizeof(*ct->byte_map_base()) == sizeof(jbyte), "adjust this code");
  51 
  52   Label L_cardtable_loop, L_done;
  53 
  54   __ cbz_32(count, L_done); // zero count - nothing to do
  55 
  56   __ add_ptr_scaled_int32(count, addr, count, LogBytesPerHeapOop);
  57   __ sub(count, count, BytesPerHeapOop);                            // last addr
  58 
  59   __ logical_shift_right(addr, addr, CardTable::card_shift);
  60   __ logical_shift_right(count, count, CardTable::card_shift);
  61   __ sub(count, count, addr); // nb of cards
  62 
  63   // warning: Rthread has not been preserved
  64   __ mov_address(tmp, (address) ct->byte_map_base(), symbolic_Relocation::card_table_reference);
  65   __ add(addr,tmp, addr);
  66 
  67   Register zero = __ zero_register(tmp);
  68 
  69   __ BIND(L_cardtable_loop);
  70   __ strb(zero, Address(addr, 1, post_indexed));
  71   __ subs(count, count, 1);
  72   __ b(L_cardtable_loop, ge);
  73   __ BIND(L_done);
  74 }
  75 
  76 void CardTableBarrierSetAssembler::oop_store_at(MacroAssembler* masm, DecoratorSet decorators, BasicType type,
  77                                              Address obj, Register new_val, Register tmp1, Register tmp2, Register tmp3, bool is_null) {
  78   bool is_array = (decorators & IS_ARRAY) != 0;
  79   bool on_anonymous = (decorators & ON_UNKNOWN_OOP_REF) != 0;
  80   bool precise = is_array || on_anonymous;
  81 
  82   if (is_null) {
  83     BarrierSetAssembler::store_at(masm, decorators, type, obj, new_val, tmp1, tmp2, tmp3, true);
  84   } else {
  85     assert (!precise || (obj.index() == noreg && obj.disp() == 0),
  86             "store check address should be calculated beforehand");
  87 
  88     store_check_part1(masm, tmp1);
  89     BarrierSetAssembler::store_at(masm, decorators, type, obj, new_val, tmp1, tmp2, tmp3, false);
  90     new_val = noreg;
  91     store_check_part2(masm, obj.base(), tmp1, tmp2);
  92   }
  93 }
  94 
  95 // The 1st part of the store check.
  96 // Sets card_table_base register.
  97 void CardTableBarrierSetAssembler::store_check_part1(MacroAssembler* masm, Register card_table_base) {
  98   // Check barrier set type (should be card table) and element size
  99   BarrierSet* bs = BarrierSet::barrier_set();
 100   assert(bs->kind() == BarrierSet::CardTableBarrierSet,
 101          "Wrong barrier set kind");
 102 
 103   CardTableBarrierSet* ctbs = barrier_set_cast<CardTableBarrierSet>(bs);
 104   CardTable* ct = ctbs->card_table();
 105   assert(sizeof(*ct->byte_map_base()) == sizeof(jbyte), "Adjust store check code");
 106 
 107   // Load card table base address.
 108 
 109   /* Performance note.
 110 
 111      There is an alternative way of loading card table base address
 112      from thread descriptor, which may look more efficient:
 113 
 114      ldr(card_table_base, Address(Rthread, JavaThread::card_table_base_offset()));
 115 
 116      However, performance measurements of micro benchmarks and specJVM98
 117      showed that loading of card table base from thread descriptor is
 118      7-18% slower compared to loading of literal embedded into the code.
 119      Possible cause is a cache miss (card table base address resides in a
 120      rarely accessed area of thread descriptor).
 121   */
 122   // TODO-AARCH64 Investigate if mov_slow is faster than ldr from Rthread on AArch64
 123   __ mov_address(card_table_base, (address)ct->byte_map_base(), symbolic_Relocation::card_table_reference);
 124 }
 125 
 126 // The 2nd part of the store check.
 127 void CardTableBarrierSetAssembler::store_check_part2(MacroAssembler* masm, Register obj, Register card_table_base, Register tmp) {
 128   assert_different_registers(obj, card_table_base, tmp);
 129 
 130   BarrierSet* bs = BarrierSet::barrier_set();
 131   assert(bs->kind() == BarrierSet::CardTableBarrierSet,
 132          "Wrong barrier set kind");
 133 
 134   CardTableBarrierSet* ctbs = barrier_set_cast<CardTableBarrierSet>(bs);
 135   CardTable* ct = ctbs->card_table();
 136   assert(sizeof(*ct->byte_map_base()) == sizeof(jbyte), "Adjust store check code");
 137 
 138   assert(CardTable::dirty_card_val() == 0, "Dirty card value must be 0 due to optimizations.");
 139 #ifdef AARCH64
 140   add(card_table_base, card_table_base, AsmOperand(obj, lsr, CardTable::card_shift));
 141   Address card_table_addr(card_table_base);
 142 #else
 143   Address card_table_addr(card_table_base, obj, lsr, CardTable::card_shift);
 144 #endif
 145 
 146   if (UseCondCardMark) {
 147     if (ct->scanned_concurrently()) {
 148       __ membar(MacroAssembler::Membar_mask_bits(MacroAssembler::StoreLoad), noreg);
 149     }
 150     Label already_dirty;
 151 
 152     __ ldrb(tmp, card_table_addr);
 153     __ cbz(tmp, already_dirty);
 154 
 155     set_card(masm, card_table_base, card_table_addr, tmp);
 156     __ bind(already_dirty);
 157 
 158   } else {
 159     if (ct->scanned_concurrently()) {
 160       __ membar(MacroAssembler::Membar_mask_bits(MacroAssembler::StoreStore), noreg);
 161     }
 162     set_card(masm, card_table_base, card_table_addr, tmp);
 163   }
 164 }
 165 
 166 void CardTableBarrierSetAssembler::set_card(MacroAssembler* masm, Register card_table_base, Address card_table_addr, Register tmp) {
 167 #ifdef AARCH64
 168   strb(ZR, card_table_addr);
 169 #else
 170   CardTableBarrierSet* ctbs = barrier_set_cast<CardTableBarrierSet>(BarrierSet::barrier_set());
 171   CardTable* ct = ctbs->card_table();
 172   if ((((uintptr_t)ct->byte_map_base() & 0xff) == 0)) {
 173     // Card table is aligned so the lowest byte of the table address base is zero.
 174     // This works only if the code is not saved for later use, possibly
 175     // in a context where the base would no longer be aligned.
 176     __ strb(card_table_base, card_table_addr);
 177   } else {
 178     __ mov(tmp, 0);
 179     __ strb(tmp, card_table_addr);
 180   }
 181 #endif // AARCH64
 182 }