1 /*
2 * Copyright (c) 2018, 2021, Red Hat, Inc. All rights reserved.
3 * Copyright (c) 2012, 2021 SAP SE. All rights reserved.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 *
24 */
25
26 #include "gc/shared/gcArguments.hpp"
27 #include "gc/shared/gc_globals.hpp"
28 #include "macroAssembler_ppc.hpp"
29 #include "precompiled.hpp"
30 #include "asm/macroAssembler.inline.hpp"
31 #include "gc/shenandoah/shenandoahBarrierSet.hpp"
32 #include "gc/shenandoah/shenandoahBarrierSetAssembler.hpp"
33 #include "gc/shenandoah/shenandoahForwarding.hpp"
34 #include "gc/shenandoah/shenandoahHeap.hpp"
35 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
36 #include "gc/shenandoah/shenandoahHeapRegion.hpp"
37 #include "gc/shenandoah/shenandoahRuntime.hpp"
38 #include "gc/shenandoah/shenandoahThreadLocalData.hpp"
39 #include "gc/shenandoah/heuristics/shenandoahHeuristics.hpp"
40 #include "interpreter/interpreter.hpp"
41 #include "runtime/javaThread.hpp"
42 #include "runtime/sharedRuntime.hpp"
43 #include "utilities/globalDefinitions.hpp"
44 #include "vm_version_ppc.hpp"
45 #ifdef COMPILER1
46 #include "c1/c1_LIRAssembler.hpp"
47 #include "c1/c1_MacroAssembler.hpp"
48 #include "gc/shenandoah/c1/shenandoahBarrierSetC1.hpp"
49 #endif
50
51 #define __ masm->
52
53 void ShenandoahBarrierSetAssembler::satb_write_barrier(MacroAssembler *masm,
54 Register base, RegisterOrConstant ind_or_offs,
55 Register tmp1, Register tmp2, Register tmp3,
56 MacroAssembler::PreservationLevel preservation_level) {
57 if (ShenandoahSATBBarrier) {
58 __ block_comment("satb_write_barrier (shenandoahgc) {");
59 satb_write_barrier_impl(masm, 0, base, ind_or_offs, tmp1, tmp2, tmp3, preservation_level);
73 satb_write_barrier_impl(masm, decorators, noreg, noreg, val, tmp1, tmp2, preservation_level);
74 __ block_comment("} iu_barrier (shenandoahgc)");
75 }
76 }
77
78 void ShenandoahBarrierSetAssembler::load_reference_barrier(MacroAssembler *masm, DecoratorSet decorators,
79 Register base, RegisterOrConstant ind_or_offs,
80 Register dst,
81 Register tmp1, Register tmp2,
82 MacroAssembler::PreservationLevel preservation_level) {
83 if (ShenandoahLoadRefBarrier) {
84 __ block_comment("load_reference_barrier (shenandoahgc) {");
85 load_reference_barrier_impl(masm, decorators, base, ind_or_offs, dst, tmp1, tmp2, preservation_level);
86 __ block_comment("} load_reference_barrier (shenandoahgc)");
87 }
88 }
89
90 void ShenandoahBarrierSetAssembler::arraycopy_prologue(MacroAssembler *masm, DecoratorSet decorators, BasicType type,
91 Register src, Register dst, Register count,
92 Register preserve1, Register preserve2) {
93 __ block_comment("arraycopy_prologue (shenandoahgc) {");
94
95 Register R11_tmp = R11_scratch1;
96
97 assert_different_registers(src, dst, count, R11_tmp, noreg);
98 if (preserve1 != noreg) {
99 // Technically not required, but likely to indicate an error.
100 assert_different_registers(preserve1, preserve2);
101 }
102
103 /* ==== Check whether barrier is required (optimizations) ==== */
104 // Fast path: Component type of array is not a reference type.
105 if (!is_reference_type(type)) {
106 return;
107 }
108
109 bool dest_uninitialized = (decorators & IS_DEST_UNINITIALIZED) != 0;
110
111 // Fast path: No barrier required if for every barrier type, it is either disabled or would not store
112 // any useful information.
113 if ((!ShenandoahSATBBarrier || dest_uninitialized) && !ShenandoahIUBarrier && !ShenandoahLoadRefBarrier) {
114 return;
115 }
116
117 Label skip_prologue;
118
119 // Fast path: Array is of length zero.
120 __ cmpdi(CCR0, count, 0);
121 __ beq(CCR0, skip_prologue);
122
123 /* ==== Check whether barrier is required (gc state) ==== */
124 __ lbz(R11_tmp, in_bytes(ShenandoahThreadLocalData::gc_state_offset()),
125 R16_thread);
126
127 // The set of garbage collection states requiring barriers depends on the available barrier types and the
128 // type of the reference in question.
129 // For instance, satb barriers may be skipped if it is certain that the overridden values are not relevant
130 // for the garbage collector.
131 const int required_states = ShenandoahSATBBarrier && dest_uninitialized
132 ? ShenandoahHeap::HAS_FORWARDED
133 : ShenandoahHeap::HAS_FORWARDED | ShenandoahHeap::MARKING;
134
135 __ andi_(R11_tmp, R11_tmp, required_states);
136 __ beq(CCR0, skip_prologue);
170 {
171 __ pop_frame();
172 __ restore_LR_CR(R11_tmp);
173
174 __ ld(count, -BytesPerWord * highest_preserve_register_index--, R1_SP);
175 __ ld(dst, -BytesPerWord * highest_preserve_register_index--, R1_SP);
176 __ ld(src, -BytesPerWord * highest_preserve_register_index--, R1_SP);
177
178 if (preserve2 != noreg && preserve2 != preserve1 && preserve2->is_volatile()) {
179 __ ld(preserve2, -BytesPerWord * highest_preserve_register_index--, R1_SP);
180 }
181 if (preserve1 != noreg && preserve1->is_volatile()) {
182 __ ld(preserve1, -BytesPerWord * highest_preserve_register_index--, R1_SP);
183 }
184 }
185
186 __ bind(skip_prologue);
187 __ block_comment("} arraycopy_prologue (shenandoahgc)");
188 }
189
190 // The to-be-enqueued value can either be determined
191 // - dynamically by passing the reference's address information (load mode) or
192 // - statically by passing a register the value is stored in (preloaded mode)
193 // - for performance optimizations in cases where the previous value is known (currently not implemented) and
194 // - for incremental-update barriers.
195 //
196 // decorators: The previous value's decorator set.
197 // In "load mode", the value must equal '0'.
198 // base: Base register of the reference's address (load mode).
199 // In "preloaded mode", the register must equal 'noreg'.
200 // ind_or_offs: Index or offset of the reference's address (load mode).
201 // If 'base' equals 'noreg' (preloaded mode), the passed value is ignored.
202 // pre_val: Register holding the to-be-stored value (preloaded mode).
203 // In "load mode", this register acts as a temporary register and must
204 // thus not be 'noreg'. In "preloaded mode", its content will be sustained.
205 // tmp1/tmp2: Temporary registers, one of which must be non-volatile in "preloaded mode".
206 void ShenandoahBarrierSetAssembler::satb_write_barrier_impl(MacroAssembler *masm, DecoratorSet decorators,
207 Register base, RegisterOrConstant ind_or_offs,
208 Register pre_val,
209 Register tmp1, Register tmp2,
569 base, ind_or_offs,
570 intermediate_dst,
571 tmp1, R0,
572 preservation_level);
573
574 __ mr_if_needed(dst, intermediate_dst);
575 } else {
576 BarrierSetAssembler::load_at(masm, decorators, type,
577 base, ind_or_offs,
578 dst,
579 tmp1, tmp2,
580 preservation_level, L_handle_null);
581 }
582
583 /* ==== Apply keep-alive barrier, if required (e.g., to inhibit weak reference resurrection) ==== */
584 if (ShenandoahBarrierSet::need_keep_alive_barrier(decorators, type)) {
585 iu_barrier(masm, dst, tmp1, tmp2, preservation_level);
586 }
587 }
588
589 // base: Base register of the reference's address.
590 // ind_or_offs: Index or offset of the reference's address.
591 // val: To-be-stored value/reference's new value.
592 void ShenandoahBarrierSetAssembler::store_at(MacroAssembler *masm, DecoratorSet decorators, BasicType type,
593 Register base, RegisterOrConstant ind_or_offs, Register val,
594 Register tmp1, Register tmp2, Register tmp3,
595 MacroAssembler::PreservationLevel preservation_level) {
596 if (is_reference_type(type)) {
597 if (ShenandoahSATBBarrier) {
598 satb_write_barrier(masm, base, ind_or_offs, tmp1, tmp2, tmp3, preservation_level);
599 }
600
601 if (ShenandoahIUBarrier && val != noreg) {
602 iu_barrier(masm, val, tmp1, tmp2, preservation_level, decorators);
603 }
604 }
605
606 BarrierSetAssembler::store_at(masm, decorators, type,
607 base, ind_or_offs,
608 val,
609 tmp1, tmp2, tmp3,
610 preservation_level);
611 }
612
613 void ShenandoahBarrierSetAssembler::try_resolve_jobject_in_native(MacroAssembler *masm,
614 Register dst, Register jni_env, Register obj,
615 Register tmp, Label &slowpath) {
616 __ block_comment("try_resolve_jobject_in_native (shenandoahgc) {");
617
618 assert_different_registers(jni_env, obj, tmp);
619
620 Label done;
621
622 // Fast path: Reference is null (JNI tags are zero for null pointers).
623 __ cmpdi(CCR0, obj, 0);
624 __ beq(CCR0, done);
625
626 // Resolve jobject using standard implementation.
627 BarrierSetAssembler::try_resolve_jobject_in_native(masm, dst, jni_env, obj, tmp, slowpath);
628
629 // Check whether heap is stable.
630 __ lbz(tmp,
740 // unlikely case should be handled by the smallest possible code. Instead of emitting a third,
741 // explicit CAS operation, the code jumps back and reuses the first CAS operation (step 1)
742 // (passed arguments are identical).
743 //
744 // A failure of the CAS operation in step 1 would imply that the overall CAS operation is supposed
745 // to fail. Jumping back to step 1 requires, however, that step 2 and step 3 are re-executed as well.
746 // It is thus important to ensure that a re-execution of those steps does not put program correctness
747 // at risk:
748 // - Step 2: Either terminates in failure (desired result) or falls through to step 3.
749 // - Step 3: Terminates if the comparison between the forwarded, fetched pointer and the expected value
750 // fails. Unless the reference has been updated in the meanwhile once again, this is
751 // guaranteed to be the case.
752 // In case of a concurrent update, the CAS would be retried again. This is legitimate
753 // in terms of program correctness (even though it is not desired).
754 __ bne(CCR0, step_four);
755
756 __ bind(done);
757 __ block_comment("} cmpxchg_oop (shenandoahgc)");
758 }
759
760 #undef __
761
762 #ifdef COMPILER1
763
764 #define __ ce->masm()->
765
766 void ShenandoahBarrierSetAssembler::gen_pre_barrier_stub(LIR_Assembler *ce, ShenandoahPreBarrierStub *stub) {
767 __ block_comment("gen_pre_barrier_stub (shenandoahgc) {");
768
769 ShenandoahBarrierSetC1 *bs = (ShenandoahBarrierSetC1*) BarrierSet::barrier_set()->barrier_set_c1();
770 __ bind(*stub->entry());
771
772 // GC status has already been verified by 'ShenandoahBarrierSetC1::pre_barrier'.
773 // This stub is the slowpath of that function.
774
775 assert(stub->pre_val()->is_register(), "pre_val must be a register");
776 Register pre_val = stub->pre_val()->as_register();
777
778 // If 'do_load()' returns false, the to-be-stored value is already available in 'stub->pre_val()'
779 // ("preloaded mode" of the store barrier).
|
1 /*
2 * Copyright (c) 2018, 2021, Red Hat, Inc. All rights reserved.
3 * Copyright (c) 2012, 2022 SAP SE. All rights reserved.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 *
24 */
25
26 #include "gc/shared/gcArguments.hpp"
27 #include "gc/shared/gc_globals.hpp"
28 #include "macroAssembler_ppc.hpp"
29 #include "precompiled.hpp"
30 #include "asm/macroAssembler.inline.hpp"
31 #include "gc/shenandoah/shenandoahBarrierSet.hpp"
32 #include "gc/shenandoah/shenandoahBarrierSetAssembler.hpp"
33 #include "gc/shenandoah/shenandoahForwarding.hpp"
34 #include "gc/shenandoah/shenandoahHeap.hpp"
35 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
36 #include "gc/shenandoah/shenandoahHeapRegion.hpp"
37 #include "gc/shenandoah/shenandoahRuntime.hpp"
38 #include "gc/shenandoah/shenandoahThreadLocalData.hpp"
39 #include "gc/shenandoah/heuristics/shenandoahHeuristics.hpp"
40 #include "gc/shenandoah/mode/shenandoahMode.hpp"
41 #include "interpreter/interpreter.hpp"
42 #include "runtime/javaThread.hpp"
43 #include "runtime/sharedRuntime.hpp"
44 #include "utilities/globalDefinitions.hpp"
45 #include "vm_version_ppc.hpp"
46 #ifdef COMPILER1
47 #include "c1/c1_LIRAssembler.hpp"
48 #include "c1/c1_MacroAssembler.hpp"
49 #include "gc/shenandoah/c1/shenandoahBarrierSetC1.hpp"
50 #endif
51
52 #define __ masm->
53
54 void ShenandoahBarrierSetAssembler::satb_write_barrier(MacroAssembler *masm,
55 Register base, RegisterOrConstant ind_or_offs,
56 Register tmp1, Register tmp2, Register tmp3,
57 MacroAssembler::PreservationLevel preservation_level) {
58 if (ShenandoahSATBBarrier) {
59 __ block_comment("satb_write_barrier (shenandoahgc) {");
60 satb_write_barrier_impl(masm, 0, base, ind_or_offs, tmp1, tmp2, tmp3, preservation_level);
74 satb_write_barrier_impl(masm, decorators, noreg, noreg, val, tmp1, tmp2, preservation_level);
75 __ block_comment("} iu_barrier (shenandoahgc)");
76 }
77 }
78
79 void ShenandoahBarrierSetAssembler::load_reference_barrier(MacroAssembler *masm, DecoratorSet decorators,
80 Register base, RegisterOrConstant ind_or_offs,
81 Register dst,
82 Register tmp1, Register tmp2,
83 MacroAssembler::PreservationLevel preservation_level) {
84 if (ShenandoahLoadRefBarrier) {
85 __ block_comment("load_reference_barrier (shenandoahgc) {");
86 load_reference_barrier_impl(masm, decorators, base, ind_or_offs, dst, tmp1, tmp2, preservation_level);
87 __ block_comment("} load_reference_barrier (shenandoahgc)");
88 }
89 }
90
91 void ShenandoahBarrierSetAssembler::arraycopy_prologue(MacroAssembler *masm, DecoratorSet decorators, BasicType type,
92 Register src, Register dst, Register count,
93 Register preserve1, Register preserve2) {
94 Register R11_tmp = R11_scratch1;
95
96 assert_different_registers(src, dst, count, R11_tmp, noreg);
97 if (preserve1 != noreg) {
98 // Technically not required, but likely to indicate an error.
99 assert_different_registers(preserve1, preserve2);
100 }
101
102 /* ==== Check whether barrier is required (optimizations) ==== */
103 // Fast path: Component type of array is not a reference type.
104 if (!is_reference_type(type)) {
105 return;
106 }
107
108 bool dest_uninitialized = (decorators & IS_DEST_UNINITIALIZED) != 0;
109
110 // Fast path: No barrier required if for every barrier type, it is either disabled or would not store
111 // any useful information.
112 if ((!ShenandoahSATBBarrier || dest_uninitialized) && !ShenandoahIUBarrier && !ShenandoahLoadRefBarrier) {
113 return;
114 }
115
116 __ block_comment("arraycopy_prologue (shenandoahgc) {");
117 Label skip_prologue;
118
119 // Fast path: Array is of length zero.
120 __ cmpdi(CCR0, count, 0);
121 __ beq(CCR0, skip_prologue);
122
123 /* ==== Check whether barrier is required (gc state) ==== */
124 __ lbz(R11_tmp, in_bytes(ShenandoahThreadLocalData::gc_state_offset()),
125 R16_thread);
126
127 // The set of garbage collection states requiring barriers depends on the available barrier types and the
128 // type of the reference in question.
129 // For instance, satb barriers may be skipped if it is certain that the overridden values are not relevant
130 // for the garbage collector.
131 const int required_states = ShenandoahSATBBarrier && dest_uninitialized
132 ? ShenandoahHeap::HAS_FORWARDED
133 : ShenandoahHeap::HAS_FORWARDED | ShenandoahHeap::MARKING;
134
135 __ andi_(R11_tmp, R11_tmp, required_states);
136 __ beq(CCR0, skip_prologue);
170 {
171 __ pop_frame();
172 __ restore_LR_CR(R11_tmp);
173
174 __ ld(count, -BytesPerWord * highest_preserve_register_index--, R1_SP);
175 __ ld(dst, -BytesPerWord * highest_preserve_register_index--, R1_SP);
176 __ ld(src, -BytesPerWord * highest_preserve_register_index--, R1_SP);
177
178 if (preserve2 != noreg && preserve2 != preserve1 && preserve2->is_volatile()) {
179 __ ld(preserve2, -BytesPerWord * highest_preserve_register_index--, R1_SP);
180 }
181 if (preserve1 != noreg && preserve1->is_volatile()) {
182 __ ld(preserve1, -BytesPerWord * highest_preserve_register_index--, R1_SP);
183 }
184 }
185
186 __ bind(skip_prologue);
187 __ block_comment("} arraycopy_prologue (shenandoahgc)");
188 }
189
190 void ShenandoahBarrierSetAssembler::arraycopy_epilogue(MacroAssembler* masm, DecoratorSet decorators, BasicType type,
191 Register dst, Register count,
192 Register preserve) {
193 if (ShenandoahCardBarrier && is_reference_type(type)) {
194 __ block_comment("arraycopy_epilogue (shenandoahgc) {");
195 gen_write_ref_array_post_barrier(masm, decorators, dst, count, preserve);
196 __ block_comment("} arraycopy_epilogue (shenandoahgc)");
197 }
198 }
199
200 // The to-be-enqueued value can either be determined
201 // - dynamically by passing the reference's address information (load mode) or
202 // - statically by passing a register the value is stored in (preloaded mode)
203 // - for performance optimizations in cases where the previous value is known (currently not implemented) and
204 // - for incremental-update barriers.
205 //
206 // decorators: The previous value's decorator set.
207 // In "load mode", the value must equal '0'.
208 // base: Base register of the reference's address (load mode).
209 // In "preloaded mode", the register must equal 'noreg'.
210 // ind_or_offs: Index or offset of the reference's address (load mode).
211 // If 'base' equals 'noreg' (preloaded mode), the passed value is ignored.
212 // pre_val: Register holding the to-be-stored value (preloaded mode).
213 // In "load mode", this register acts as a temporary register and must
214 // thus not be 'noreg'. In "preloaded mode", its content will be sustained.
215 // tmp1/tmp2: Temporary registers, one of which must be non-volatile in "preloaded mode".
216 void ShenandoahBarrierSetAssembler::satb_write_barrier_impl(MacroAssembler *masm, DecoratorSet decorators,
217 Register base, RegisterOrConstant ind_or_offs,
218 Register pre_val,
219 Register tmp1, Register tmp2,
579 base, ind_or_offs,
580 intermediate_dst,
581 tmp1, R0,
582 preservation_level);
583
584 __ mr_if_needed(dst, intermediate_dst);
585 } else {
586 BarrierSetAssembler::load_at(masm, decorators, type,
587 base, ind_or_offs,
588 dst,
589 tmp1, tmp2,
590 preservation_level, L_handle_null);
591 }
592
593 /* ==== Apply keep-alive barrier, if required (e.g., to inhibit weak reference resurrection) ==== */
594 if (ShenandoahBarrierSet::need_keep_alive_barrier(decorators, type)) {
595 iu_barrier(masm, dst, tmp1, tmp2, preservation_level);
596 }
597 }
598
599 void ShenandoahBarrierSetAssembler::store_check(MacroAssembler* masm, Register base, RegisterOrConstant ind_or_offs, Register tmp) {
600 assert(ShenandoahCardBarrier, "Should have been checked by caller");
601
602 ShenandoahBarrierSet* ctbs = ShenandoahBarrierSet::barrier_set();
603 CardTable* ct = ctbs->card_table();
604 assert_different_registers(base, tmp, R0);
605
606 if (ind_or_offs.is_constant()) {
607 __ add_const_optimized(base, base, ind_or_offs.as_constant(), tmp);
608 } else {
609 __ add(base, ind_or_offs.as_register(), base);
610 }
611
612 __ load_const_optimized(tmp, (address)ct->byte_map_base(), R0);
613 __ srdi(base, base, CardTable::card_shift());
614 __ li(R0, CardTable::dirty_card_val());
615 __ stbx(R0, tmp, base);
616 }
617
618 // base: Base register of the reference's address.
619 // ind_or_offs: Index or offset of the reference's address.
620 // val: To-be-stored value/reference's new value.
621 void ShenandoahBarrierSetAssembler::store_at(MacroAssembler *masm, DecoratorSet decorators, BasicType type,
622 Register base, RegisterOrConstant ind_or_offs, Register val,
623 Register tmp1, Register tmp2, Register tmp3,
624 MacroAssembler::PreservationLevel preservation_level) {
625 if (is_reference_type(type)) {
626 if (ShenandoahSATBBarrier) {
627 satb_write_barrier(masm, base, ind_or_offs, tmp1, tmp2, tmp3, preservation_level);
628 }
629
630 if (ShenandoahIUBarrier && val != noreg) {
631 iu_barrier(masm, val, tmp1, tmp2, preservation_level, decorators);
632 }
633 }
634
635 BarrierSetAssembler::store_at(masm, decorators, type,
636 base, ind_or_offs,
637 val,
638 tmp1, tmp2, tmp3,
639 preservation_level);
640
641 // No need for post barrier if storing NULL
642 if (ShenandoahCardBarrier && is_reference_type(type) && val != noreg) {
643 store_check(masm, base, ind_or_offs, tmp1);
644 }
645 }
646
647 void ShenandoahBarrierSetAssembler::try_resolve_jobject_in_native(MacroAssembler *masm,
648 Register dst, Register jni_env, Register obj,
649 Register tmp, Label &slowpath) {
650 __ block_comment("try_resolve_jobject_in_native (shenandoahgc) {");
651
652 assert_different_registers(jni_env, obj, tmp);
653
654 Label done;
655
656 // Fast path: Reference is null (JNI tags are zero for null pointers).
657 __ cmpdi(CCR0, obj, 0);
658 __ beq(CCR0, done);
659
660 // Resolve jobject using standard implementation.
661 BarrierSetAssembler::try_resolve_jobject_in_native(masm, dst, jni_env, obj, tmp, slowpath);
662
663 // Check whether heap is stable.
664 __ lbz(tmp,
774 // unlikely case should be handled by the smallest possible code. Instead of emitting a third,
775 // explicit CAS operation, the code jumps back and reuses the first CAS operation (step 1)
776 // (passed arguments are identical).
777 //
778 // A failure of the CAS operation in step 1 would imply that the overall CAS operation is supposed
779 // to fail. Jumping back to step 1 requires, however, that step 2 and step 3 are re-executed as well.
780 // It is thus important to ensure that a re-execution of those steps does not put program correctness
781 // at risk:
782 // - Step 2: Either terminates in failure (desired result) or falls through to step 3.
783 // - Step 3: Terminates if the comparison between the forwarded, fetched pointer and the expected value
784 // fails. Unless the reference has been updated in the meanwhile once again, this is
785 // guaranteed to be the case.
786 // In case of a concurrent update, the CAS would be retried again. This is legitimate
787 // in terms of program correctness (even though it is not desired).
788 __ bne(CCR0, step_four);
789
790 __ bind(done);
791 __ block_comment("} cmpxchg_oop (shenandoahgc)");
792 }
793
794 void ShenandoahBarrierSetAssembler::gen_write_ref_array_post_barrier(MacroAssembler* masm, DecoratorSet decorators,
795 Register addr, Register count, Register preserve) {
796 assert(ShenandoahCardBarrier, "Should have been checked by caller");
797
798 ShenandoahBarrierSet* bs = ShenandoahBarrierSet::barrier_set();
799 CardTable* ct = bs->card_table();
800 assert_different_registers(addr, count, R0);
801
802 Label L_skip_loop, L_store_loop;
803
804 __ sldi_(count, count, LogBytesPerHeapOop);
805
806 // Zero length? Skip.
807 __ beq(CCR0, L_skip_loop);
808
809 __ addi(count, count, -BytesPerHeapOop);
810 __ add(count, addr, count);
811 // Use two shifts to clear out those low order two bits! (Cannot opt. into 1.)
812 __ srdi(addr, addr, CardTable::card_shift());
813 __ srdi(count, count, CardTable::card_shift());
814 __ subf(count, addr, count);
815 __ add_const_optimized(addr, addr, (address)ct->byte_map_base(), R0);
816 __ addi(count, count, 1);
817 __ li(R0, 0);
818 __ mtctr(count);
819
820 // Byte store loop
821 __ bind(L_store_loop);
822 __ stb(R0, 0, addr);
823 __ addi(addr, addr, 1);
824 __ bdnz(L_store_loop);
825 __ bind(L_skip_loop);
826 }
827
828 #undef __
829
830 #ifdef COMPILER1
831
832 #define __ ce->masm()->
833
834 void ShenandoahBarrierSetAssembler::gen_pre_barrier_stub(LIR_Assembler *ce, ShenandoahPreBarrierStub *stub) {
835 __ block_comment("gen_pre_barrier_stub (shenandoahgc) {");
836
837 ShenandoahBarrierSetC1 *bs = (ShenandoahBarrierSetC1*) BarrierSet::barrier_set()->barrier_set_c1();
838 __ bind(*stub->entry());
839
840 // GC status has already been verified by 'ShenandoahBarrierSetC1::pre_barrier'.
841 // This stub is the slowpath of that function.
842
843 assert(stub->pre_val()->is_register(), "pre_val must be a register");
844 Register pre_val = stub->pre_val()->as_register();
845
846 // If 'do_load()' returns false, the to-be-stored value is already available in 'stub->pre_val()'
847 // ("preloaded mode" of the store barrier).
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