1 /*
2 * Copyright (c) 2026, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2018, 2021, Red Hat, Inc. All rights reserved.
4 * Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
5 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
6 *
7 * This code is free software; you can redistribute it and/or modify it
8 * under the terms of the GNU General Public License version 2 only, as
9 * published by the Free Software Foundation.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 *
25 */
26
27 #include "gc/shenandoah/heuristics/shenandoahHeuristics.hpp"
28 #include "gc/shenandoah/mode/shenandoahMode.hpp"
29 #include "gc/shenandoah/shenandoahBarrierSet.hpp"
30 #include "gc/shenandoah/shenandoahBarrierSetAssembler.hpp"
31 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
32 #include "gc/shenandoah/shenandoahHeapRegion.hpp"
33 #include "gc/shenandoah/shenandoahNMethod.inline.hpp"
34 #include "gc/shenandoah/shenandoahRuntime.hpp"
35 #include "gc/shenandoah/shenandoahThreadLocalData.hpp"
36 #include "interpreter/interpreter.hpp"
37 #include "nativeInst_x86.hpp"
38 #include "runtime/javaThread.hpp"
39 #include "runtime/sharedRuntime.hpp"
40 #include "utilities/macros.hpp"
41 #ifdef COMPILER1
42 #include "c1/c1_LIRAssembler.hpp"
43 #include "c1/c1_MacroAssembler.hpp"
44 #include "gc/shenandoah/c1/shenandoahBarrierSetC1.hpp"
45 #endif
46 #ifdef COMPILER2
47 #include "gc/shenandoah/c2/shenandoahBarrierSetC2.hpp"
48 #endif
49
50 #define __ masm->
51
52 void ShenandoahBarrierSetAssembler::arraycopy_prologue(MacroAssembler* masm, DecoratorSet decorators, BasicType type,
53 Register src, Register dst, Register count) {
54
55 bool dest_uninitialized = (decorators & IS_DEST_UNINITIALIZED) != 0;
56
57 if (is_reference_type(type)) {
58 if (ShenandoahCardBarrier) {
59 bool checkcast = (decorators & ARRAYCOPY_CHECKCAST) != 0;
60 bool disjoint = (decorators & ARRAYCOPY_DISJOINT) != 0;
61 bool obj_int = (type == T_OBJECT) && UseCompressedOops;
62
63 // We need to save the original element count because the array copy stub
64 // will destroy the value and we need it for the card marking barrier.
65 if (!checkcast) {
66 if (!obj_int) {
67 // Save count for barrier
68 __ movptr(r11, count);
69 } else if (disjoint) {
70 // Save dst in r11 in the disjoint case
71 __ movq(r11, dst);
72 }
73 }
74 }
75
76 if ((ShenandoahSATBBarrier && !dest_uninitialized) || ShenandoahLoadRefBarrier) {
77 Register thread = r15_thread;
78 assert_different_registers(src, dst, count, thread);
79
80 Label L_done;
81 // Short-circuit if count == 0.
82 __ testptr(count, count);
83 __ jcc(Assembler::zero, L_done);
84
85 // Avoid runtime call when not active.
86 Address gc_state(thread, in_bytes(ShenandoahThreadLocalData::gc_state_offset()));
87 int flags;
88 if (ShenandoahSATBBarrier && dest_uninitialized) {
89 flags = ShenandoahHeap::HAS_FORWARDED;
90 } else {
91 flags = ShenandoahHeap::HAS_FORWARDED | ShenandoahHeap::MARKING;
92 }
93 __ testb(gc_state, flags);
94 __ jcc(Assembler::zero, L_done);
95
96 __ push_call_clobbered_registers(/* save_fpu = */ false);
97 // If arguments are not in proper places, shuffle them.
98 // Doing this via the stack is the most straight-forward way to avoid
99 // accidentally smashing any register.
100 if (c_rarg0 != src || c_rarg1 != dst || c_rarg2 != count) {
101 __ push(src);
102 __ push(dst);
103 __ push(count);
104 __ pop(c_rarg2);
105 __ pop(c_rarg1);
106 __ pop(c_rarg0);
107 }
108 address target = nullptr;
109 if (UseCompressedOops) {
110 target = CAST_FROM_FN_PTR(address, ShenandoahRuntime::arraycopy_barrier_narrow_oop);
111 } else {
112 target = CAST_FROM_FN_PTR(address, ShenandoahRuntime::arraycopy_barrier_oop);
113 }
114 __ call_VM_leaf(target, 3);
115
116 __ pop_call_clobbered_registers(/* restore_fpu = */ false);
117
118 __ bind(L_done);
119 }
120 }
121
122 }
123
124 void ShenandoahBarrierSetAssembler::arraycopy_epilogue(MacroAssembler* masm, DecoratorSet decorators, BasicType type,
125 Register src, Register dst, Register count) {
126
127 if (ShenandoahCardBarrier && is_reference_type(type)) {
128 bool checkcast = (decorators & ARRAYCOPY_CHECKCAST) != 0;
129 bool disjoint = (decorators & ARRAYCOPY_DISJOINT) != 0;
130 bool obj_int = (type == T_OBJECT) && UseCompressedOops;
131 Register tmp = rax;
132
133 if (!checkcast) {
134 if (!obj_int) {
135 // Save count for barrier
136 count = r11;
137 } else if (disjoint) {
138 // Use the saved dst in the disjoint case
139 dst = r11;
140 }
141 } else {
142 tmp = rscratch1;
143 }
144 gen_write_ref_array_post_barrier(masm, decorators, dst, count, tmp);
145 }
146 }
147
148 void ShenandoahBarrierSetAssembler::satb_barrier(MacroAssembler* masm,
149 Register obj,
150 Register pre_val,
151 Register tmp) {
152 assert(ShenandoahSATBBarrier, "Should be checked by caller");
153 const Register thread = r15_thread;
154
155 Label done;
156 Label runtime;
157
158 assert(pre_val != noreg, "check this code");
159
160 if (obj != noreg) {
161 assert_different_registers(obj, pre_val, tmp);
162 assert(pre_val != rax, "check this code");
163 }
164
165 Address index(thread, in_bytes(ShenandoahThreadLocalData::satb_mark_queue_index_offset()));
166 Address buffer(thread, in_bytes(ShenandoahThreadLocalData::satb_mark_queue_buffer_offset()));
167
168 Address gc_state(thread, in_bytes(ShenandoahThreadLocalData::gc_state_offset()));
169 __ testb(gc_state, ShenandoahHeap::MARKING);
170 __ jcc(Assembler::zero, done);
171
172 // Do we need to load the previous value?
173 if (obj != noreg) {
174 if (UseCompressedOops) {
175 __ movl(pre_val, Address(obj, 0));
176 __ decode_heap_oop(pre_val);
177 } else {
178 __ movq(pre_val, Address(obj, 0));
179 }
180 }
181
182 // Is the previous value null?
183 __ cmpptr(pre_val, NULL_WORD);
184 __ jcc(Assembler::equal, done);
185
186 // Can we store original value in the thread's buffer?
187 // Is index == 0?
188 // (The index field is typed as size_t.)
189
190 __ movptr(tmp, index); // tmp := *index_adr
191 __ cmpptr(tmp, 0); // tmp == 0?
192 __ jcc(Assembler::equal, runtime); // If yes, goto runtime
193
194 __ subptr(tmp, wordSize); // tmp := tmp - wordSize
195 __ movptr(index, tmp); // *index_adr := tmp
196 __ addptr(tmp, buffer); // tmp := tmp + *buffer_adr
197
198 // Record the previous value
199 __ movptr(Address(tmp, 0), pre_val);
200 __ jmp(done);
201
202 __ bind(runtime);
203
204 // Slow-path call.
205 // Some paths can be reached from the c2i adapter with live fp arguments in registers.
206 __ enter();
207 __ push_call_clobbered_registers(/* save_fpu = */ true);
208
209 assert(thread != c_rarg0, "smashed arg");
210 if (c_rarg0 != pre_val) {
211 __ mov(c_rarg0, pre_val);
212 }
213
214 // Calling with super_call_VM_leaf with c_rarg0 bypasses interpreter checks and avoids any moves.
215 __ super_call_VM_leaf(CAST_FROM_FN_PTR(address, ShenandoahRuntime::write_barrier_pre), c_rarg0);
216
217 __ pop_call_clobbered_registers(/* restore_fpu = */ true);
218 __ leave();
219
220 __ bind(done);
221 }
222
223 void ShenandoahBarrierSetAssembler::load_reference_barrier(MacroAssembler* masm, Register dst, Address src, DecoratorSet decorators) {
224 assert(ShenandoahLoadRefBarrier, "Should be enabled");
225
226 bool is_strong = ShenandoahBarrierSet::is_strong_access(decorators);
227 bool is_weak = ShenandoahBarrierSet::is_weak_access(decorators);
228 bool is_phantom = ShenandoahBarrierSet::is_phantom_access(decorators);
229 bool is_native = ShenandoahBarrierSet::is_native_access(decorators);
230 bool is_narrow = UseCompressedOops && !is_native;
231
232 Label heap_stable, not_cset;
233
234 __ block_comment("load_reference_barrier { ");
235
236 // Check if GC is active
237 Register thread = r15_thread;
238
239 Address gc_state(thread, in_bytes(ShenandoahThreadLocalData::gc_state_offset()));
240 int flags = ShenandoahHeap::HAS_FORWARDED;
241 if (!is_strong) {
242 flags |= ShenandoahHeap::WEAK_ROOTS;
243 }
244 __ testb(gc_state, flags);
245 __ jcc(Assembler::zero, heap_stable);
246
247 Register tmp1 = noreg, tmp2 = noreg;
248 if (is_strong) {
249 // Test for object in cset
250 // Allocate temporary registers
251 for (int i = 0; i < Register::available_gp_registers(); i++) {
252 Register r = as_Register(i);
253 if (r != rsp && r != rbp && r != rcx && r != dst && r != src.base() && r != src.index() ) {
254 if (tmp1 == noreg) {
255 tmp1 = r;
256 } else {
257 tmp2 = r;
258 break;
259 }
260 }
261 }
262 assert(tmp1 != noreg, "tmp1 allocated");
263 assert(tmp2 != noreg, "tmp2 allocated");
264 assert_different_registers(tmp1, tmp2, src.base(), src.index());
265 assert_different_registers(tmp1, tmp2, dst);
266
267 __ push(tmp1);
268 __ push(tmp2);
269
270 // Optimized cset-test
271 __ movptr(tmp1, dst);
272 if (AOTCodeCache::is_on_for_dump()) {
273 assert_different_registers(tmp1, tmp2, rcx);
274 __ lea(tmp2, ExternalAddress(AOTRuntimeConstants::grain_shift_address()));
275 __ push(rcx);
276 __ movb(rcx, Address(tmp2));
277 __ shrptr(tmp1);
278 __ pop(rcx);
279 __ lea(tmp2, ExternalAddress(AOTRuntimeConstants::cset_base_address()));
280 __ movptr(tmp2, Address(tmp2));
281 } else {
282 __ shrptr(tmp1, ShenandoahHeapRegion::region_size_bytes_shift_jint());
283 __ movptr(tmp2, (intptr_t) ShenandoahHeap::in_cset_fast_test_addr());
284 }
285 __ movbool(tmp1, Address(tmp1, tmp2, Address::times_1));
286 __ testbool(tmp1);
287 __ jcc(Assembler::zero, not_cset);
288 }
289
290 // Slow-path call.
291 // Save registers that can be clobbered by call.
292 // Some paths can be reached from the c2i adapter with live fp arguments in registers.
293 __ enter();
294 if (dst != rax) {
295 __ push(rax);
296 }
297 __ push_call_clobbered_registers_except(rax, /* save_fpu = */ true);
298
299 // Shuffle registers such that dst is in c_rarg0 and addr in c_rarg1.
300 if (dst == c_rarg1) {
301 __ lea(c_rarg0, src);
302 __ xchgptr(c_rarg1, c_rarg0);
303 } else {
304 __ lea(c_rarg1, src);
305 __ movptr(c_rarg0, dst);
306 }
307
308 address target = nullptr;
309 if (is_strong) {
310 if (is_narrow) {
311 target = CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier_strong_narrow);
312 } else {
313 target = CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier_strong);
314 }
315 } else if (is_weak) {
316 if (is_narrow) {
317 target = CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier_weak_narrow);
318 } else {
319 target = CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier_weak);
320 }
321 } else {
322 assert(is_phantom, "only remaining strength");
323 assert(!is_narrow, "phantom access cannot be narrow");
324 target = CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier_phantom);
325 }
326
327 // Calling with super_call_VM_leaf with c_rarg0/1 bypasses interpreter checks and avoids any moves.
328 __ super_call_VM_leaf(target, c_rarg0, c_rarg1);
329 __ pop_call_clobbered_registers_except(rax, /* restore_fpu = */ true);
330 if (dst != rax) {
331 __ movptr(dst, rax);
332 __ pop(rax);
333 }
334 __ leave();
335
336 __ bind(not_cset);
337
338 if (is_strong) {
339 __ pop(tmp2);
340 __ pop(tmp1);
341 }
342
343 __ bind(heap_stable);
344
345 __ block_comment("} load_reference_barrier");
346 }
347
348 //
349 // Arguments:
350 //
351 // Inputs:
352 // src: oop location, might be clobbered
353 // tmp1: scratch register, might not be valid.
354 //
355 // Output:
356 // dst: oop loaded from src location
357 //
358 // Kill:
359 // tmp1 (if it is valid)
360 //
361 void ShenandoahBarrierSetAssembler::load_at(MacroAssembler* masm, DecoratorSet decorators, BasicType type,
362 Register dst, Address src, Register tmp1) {
363 // 1: non-reference load, no additional barrier is needed
364 if (!is_reference_type(type)) {
365 BarrierSetAssembler::load_at(masm, decorators, type, dst, src, tmp1);
366 return;
367 }
368
369 assert((decorators & ON_UNKNOWN_OOP_REF) == 0, "Not expected");
370
371 // 2: load a reference from src location and apply LRB if needed
372 if (ShenandoahBarrierSet::need_load_reference_barrier(decorators, type)) {
373 Register result_dst = dst;
374 bool use_tmp1_for_dst = false;
375
376 // Preserve src location for LRB
377 if (dst == src.base() || dst == src.index()) {
378 // Use tmp1 for dst if possible, as it is not used in BarrierAssembler::load_at()
379 if (tmp1->is_valid() && tmp1 != src.base() && tmp1 != src.index()) {
380 dst = tmp1;
381 use_tmp1_for_dst = true;
382 } else {
383 dst = rdi;
384 __ push(dst);
385 }
386 assert_different_registers(dst, src.base(), src.index());
387 }
388
389 BarrierSetAssembler::load_at(masm, decorators, type, dst, src, tmp1);
390
391 load_reference_barrier(masm, dst, src, decorators);
392
393 // Move loaded oop to final destination
394 if (dst != result_dst) {
395 __ movptr(result_dst, dst);
396
397 if (!use_tmp1_for_dst) {
398 __ pop(dst);
399 }
400
401 dst = result_dst;
402 }
403 } else {
404 BarrierSetAssembler::load_at(masm, decorators, type, dst, src, tmp1);
405 }
406
407 // 3: apply keep-alive barrier if needed
408 if (ShenandoahBarrierSet::need_keep_alive_barrier(decorators, type)) {
409 satb_barrier(masm /* masm */,
410 noreg /* obj */,
411 dst /* pre_val */,
412 tmp1 /* tmp */);
413 }
414 }
415
416 void ShenandoahBarrierSetAssembler::card_barrier(MacroAssembler* masm, Register obj) {
417 assert(ShenandoahCardBarrier, "Should have been checked by caller");
418
419 // Does a store check for the oop in register obj. The content of
420 // register obj is destroyed afterwards.
421 __ shrptr(obj, CardTable::card_shift());
422
423 // We'll use this register as the TLS base address and also later on
424 // to hold the byte_map_base.
425 Register thread = r15_thread;
426 Register tmp = rscratch1;
427
428 Address curr_ct_holder_addr(thread, in_bytes(ShenandoahThreadLocalData::card_table_offset()));
429 __ movptr(tmp, curr_ct_holder_addr);
430 Address card_addr(tmp, obj, Address::times_1);
431
432 int dirty = CardTable::dirty_card_val();
433 if (UseCondCardMark) {
434 Label L_already_dirty;
435 __ cmpb(card_addr, dirty);
436 __ jccb(Assembler::equal, L_already_dirty);
437 __ movb(card_addr, dirty);
438 __ bind(L_already_dirty);
439 } else {
440 __ movb(card_addr, dirty);
441 }
442 }
443
444 void ShenandoahBarrierSetAssembler::store_at(MacroAssembler* masm, DecoratorSet decorators, BasicType type,
445 Address dst, Register val, Register tmp1, Register tmp2, Register tmp3) {
446
447 // 1: non-reference types require no barriers
448 if (!is_reference_type(type)) {
449 BarrierSetAssembler::store_at(masm, decorators, type, dst, val, tmp1, tmp2, tmp3);
450 return;
451 }
452
453 // Flatten object address right away for simplicity: likely needed by barriers
454 assert_different_registers(val, tmp1, tmp2, tmp3, r15_thread);
455 if (dst.index() == noreg && dst.disp() == 0) {
456 if (dst.base() != tmp1) {
457 __ movptr(tmp1, dst.base());
458 }
459 } else {
460 __ lea(tmp1, dst);
461 }
462
463 // 2: pre-barrier: SATB needs the previous value
464 if (ShenandoahBarrierSet::need_satb_barrier(decorators, type)) {
465 satb_barrier(masm,
466 tmp1 /* obj */,
467 tmp2 /* pre_val */,
468 tmp3 /* tmp */);
469 }
470
471 // Store!
472 BarrierSetAssembler::store_at(masm, decorators, type, Address(tmp1, 0), val, noreg, noreg, noreg);
473
474 // 3: post-barrier: card barrier needs store address
475 bool storing_non_null = (val != noreg);
476 if (ShenandoahBarrierSet::need_card_barrier(decorators, type) && storing_non_null) {
477 card_barrier(masm, tmp1);
478 }
479 }
480
481 void ShenandoahBarrierSetAssembler::try_resolve_jobject_in_native(MacroAssembler* masm, Register jni_env,
482 Register obj, Register tmp, Label& slowpath) {
483 Label done;
484 // Resolve jobject
485 BarrierSetAssembler::try_resolve_jobject_in_native(masm, jni_env, obj, tmp, slowpath);
486
487 // Check for null.
488 __ testptr(obj, obj);
489 __ jcc(Assembler::zero, done);
490
491 Address gc_state(jni_env, ShenandoahThreadLocalData::gc_state_offset() - JavaThread::jni_environment_offset());
492 __ testb(gc_state, ShenandoahHeap::EVACUATION);
493 __ jccb(Assembler::notZero, slowpath);
494 __ bind(done);
495 }
496
497 void ShenandoahBarrierSetAssembler::try_peek_weak_handle_in_nmethod(MacroAssembler* masm, Register weak_handle, Register obj, Label& slowpath) {
498 Label done;
499
500 // Peek weak handle using the standard implementation.
501 BarrierSetAssembler::try_peek_weak_handle_in_nmethod(masm, weak_handle, obj, slowpath);
502
503 // Check if the reference is null, and if it is, take the fast path.
504 __ testptr(obj, obj);
505 __ jcc(Assembler::zero, done);
506
507 Address gc_state(r15_thread, ShenandoahThreadLocalData::gc_state_offset());
508
509 // Check if the heap is under weak-reference/roots processing, in
510 // which case we need to take the slow path.
511 __ testb(gc_state, ShenandoahHeap::WEAK_ROOTS);
512 __ jcc(Assembler::notZero, slowpath);
513 __ bind(done);
514 }
515
516 #ifdef PRODUCT
517 #define BLOCK_COMMENT(str) /* nothing */
518 #else
519 #define BLOCK_COMMENT(str) __ block_comment(str)
520 #endif
521
522 #define BIND(label) bind(label); BLOCK_COMMENT(#label ":")
523
524 #define TIMES_OOP (UseCompressedOops ? Address::times_4 : Address::times_8)
525
526 void ShenandoahBarrierSetAssembler::gen_write_ref_array_post_barrier(MacroAssembler* masm, DecoratorSet decorators,
527 Register addr, Register count,
528 Register tmp) {
529 assert(ShenandoahCardBarrier, "Should have been checked by caller");
530
531 Label L_loop, L_done;
532 const Register end = count;
533 assert_different_registers(addr, end);
534
535 // Zero count? Nothing to do.
536 __ testl(count, count);
537 __ jccb(Assembler::zero, L_done);
538
539 const Register thread = r15_thread;
540 Address curr_ct_holder_addr(thread, in_bytes(ShenandoahThreadLocalData::card_table_offset()));
541 __ movptr(tmp, curr_ct_holder_addr);
542
543 __ leaq(end, Address(addr, count, TIMES_OOP, 0)); // end == addr+count*oop_size
544 __ subptr(end, BytesPerHeapOop); // end - 1 to make inclusive
545 __ shrptr(addr, CardTable::card_shift());
546 __ shrptr(end, CardTable::card_shift());
547 __ subptr(end, addr); // end --> cards count
548
549 __ addptr(addr, tmp);
550
551 __ BIND(L_loop);
552 __ movb(Address(addr, count, Address::times_1), 0);
553 __ decrement(count);
554 __ jccb(Assembler::greaterEqual, L_loop);
555
556 __ BIND(L_done);
557 }
558
559 #undef __
560
561 #ifdef COMPILER1
562
563 #define __ ce->masm()->
564
565 void ShenandoahBarrierSetAssembler::gen_pre_barrier_stub(LIR_Assembler* ce, ShenandoahPreBarrierStub* stub) {
566 ShenandoahBarrierSetC1* bs = (ShenandoahBarrierSetC1*)BarrierSet::barrier_set()->barrier_set_c1();
567 // At this point we know that marking is in progress.
568 // If do_load() is true then we have to emit the
569 // load of the previous value; otherwise it has already
570 // been loaded into _pre_val.
571
572 __ bind(*stub->entry());
573 assert(stub->pre_val()->is_register(), "Precondition.");
574
575 Register pre_val_reg = stub->pre_val()->as_register();
576
577 if (stub->do_load()) {
578 ce->mem2reg(stub->addr(), stub->pre_val(), T_OBJECT, stub->patch_code(), stub->info(), false /*wide*/);
579 }
580
581 __ cmpptr(pre_val_reg, NULL_WORD);
582 __ jcc(Assembler::equal, *stub->continuation());
583 ce->store_parameter(stub->pre_val()->as_register(), 0);
584 __ call(RuntimeAddress(bs->pre_barrier_c1_runtime_code_blob()->code_begin()));
585 __ jmp(*stub->continuation());
586
587 }
588
589 void ShenandoahBarrierSetAssembler::gen_load_reference_barrier_stub(LIR_Assembler* ce, ShenandoahLoadReferenceBarrierStub* stub) {
590 ShenandoahBarrierSetC1* bs = (ShenandoahBarrierSetC1*)BarrierSet::barrier_set()->barrier_set_c1();
591 __ bind(*stub->entry());
592
593 DecoratorSet decorators = stub->decorators();
594 bool is_strong = ShenandoahBarrierSet::is_strong_access(decorators);
595 bool is_weak = ShenandoahBarrierSet::is_weak_access(decorators);
596 bool is_phantom = ShenandoahBarrierSet::is_phantom_access(decorators);
597 bool is_native = ShenandoahBarrierSet::is_native_access(decorators);
598
599 Register obj = stub->obj()->as_register();
600 Register res = stub->result()->as_register();
601 Register addr = stub->addr()->as_pointer_register();
602 Register tmp1 = stub->tmp1()->as_register();
603 Register tmp2 = stub->tmp2()->as_register();
604 assert_different_registers(obj, res, addr, tmp1, tmp2);
605
606 Label slow_path;
607
608 assert(res == rax, "result must arrive in rax");
609
610 if (res != obj) {
611 __ mov(res, obj);
612 }
613
614 if (is_strong) {
615 // Check for object being in the collection set.
616 __ mov(tmp1, res);
617 if (AOTCodeCache::is_on_for_dump()) {
618 __ push(rcx);
619 __ lea(rcx, ExternalAddress(AOTRuntimeConstants::grain_shift_address()));
620 __ movl(rcx, Address(rcx));
621 if (tmp1 != rcx) {
622 __ mov(tmp1, res);
623 __ shrptr(tmp1);
624 __ pop(rcx);
625 } else {
626 assert_different_registers(tmp2, rcx);
627 __ mov(tmp2, res);
628 __ shrptr(tmp2);
629 __ pop(rcx);
630 __ movptr(tmp1, tmp2);
631 }
632 __ lea(tmp2, ExternalAddress(AOTRuntimeConstants::cset_base_address()));
633 __ movptr(tmp2, Address(tmp2));
634 } else {
635 __ shrptr(tmp1, ShenandoahHeapRegion::region_size_bytes_shift_jint());
636 __ movptr(tmp2, (intptr_t) ShenandoahHeap::in_cset_fast_test_addr());
637 }
638 __ movbool(tmp2, Address(tmp2, tmp1, Address::times_1));
639 __ testbool(tmp2);
640 __ jcc(Assembler::zero, *stub->continuation());
641 }
642
643 __ bind(slow_path);
644 ce->store_parameter(res, 0);
645 ce->store_parameter(addr, 1);
646 if (is_strong) {
647 if (is_native) {
648 __ call(RuntimeAddress(bs->load_reference_barrier_strong_native_rt_code_blob()->code_begin()));
649 } else {
650 __ call(RuntimeAddress(bs->load_reference_barrier_strong_rt_code_blob()->code_begin()));
651 }
652 } else if (is_weak) {
653 __ call(RuntimeAddress(bs->load_reference_barrier_weak_rt_code_blob()->code_begin()));
654 } else {
655 assert(is_phantom, "only remaining strength");
656 __ call(RuntimeAddress(bs->load_reference_barrier_phantom_rt_code_blob()->code_begin()));
657 }
658 __ jmp(*stub->continuation());
659 }
660
661 #undef __
662
663 #define __ sasm->
664
665 void ShenandoahBarrierSetAssembler::generate_c1_pre_barrier_runtime_stub(StubAssembler* sasm) {
666 __ prologue("shenandoah_pre_barrier", false);
667 // arg0 : previous value of memory
668
669 __ push(rax);
670 __ push(rdx);
671
672 const Register pre_val = rax;
673 const Register thread = r15_thread;
674 const Register tmp = rdx;
675
676 Address queue_index(thread, in_bytes(ShenandoahThreadLocalData::satb_mark_queue_index_offset()));
677 Address buffer(thread, in_bytes(ShenandoahThreadLocalData::satb_mark_queue_buffer_offset()));
678
679 Label done;
680 Label runtime;
681
682 // Is SATB still active?
683 Address gc_state(thread, in_bytes(ShenandoahThreadLocalData::gc_state_offset()));
684 __ testb(gc_state, ShenandoahHeap::MARKING);
685 __ jcc(Assembler::zero, done);
686
687 // Can we store original value in the thread's buffer?
688
689 __ movptr(tmp, queue_index);
690 __ testptr(tmp, tmp);
691 __ jcc(Assembler::zero, runtime);
692 __ subptr(tmp, wordSize);
693 __ movptr(queue_index, tmp);
694 __ addptr(tmp, buffer);
695
696 // prev_val (rax)
697 __ load_parameter(0, pre_val);
698 __ movptr(Address(tmp, 0), pre_val);
699 __ jmp(done);
700
701 __ bind(runtime);
702
703 __ save_live_registers_no_oop_map(true);
704
705 // load the pre-value
706 __ load_parameter(0, rcx);
707 __ call_VM_leaf(CAST_FROM_FN_PTR(address, ShenandoahRuntime::write_barrier_pre), rcx);
708
709 __ restore_live_registers(true);
710
711 __ bind(done);
712
713 __ pop(rdx);
714 __ pop(rax);
715
716 __ epilogue();
717 }
718
719 void ShenandoahBarrierSetAssembler::generate_c1_load_reference_barrier_runtime_stub(StubAssembler* sasm, DecoratorSet decorators) {
720 __ prologue("shenandoah_load_reference_barrier", false);
721 // arg0 : object to be resolved
722
723 __ save_live_registers_no_oop_map(true);
724
725 bool is_strong = ShenandoahBarrierSet::is_strong_access(decorators);
726 bool is_weak = ShenandoahBarrierSet::is_weak_access(decorators);
727 bool is_phantom = ShenandoahBarrierSet::is_phantom_access(decorators);
728 bool is_native = ShenandoahBarrierSet::is_native_access(decorators);
729
730 __ load_parameter(0, c_rarg0);
731 __ load_parameter(1, c_rarg1);
732 if (is_strong) {
733 if (is_native) {
734 __ call_VM_leaf(CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier_strong), c_rarg0, c_rarg1);
735 } else {
736 if (UseCompressedOops) {
737 __ call_VM_leaf(CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier_strong_narrow), c_rarg0, c_rarg1);
738 } else {
739 __ call_VM_leaf(CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier_strong), c_rarg0, c_rarg1);
740 }
741 }
742 } else if (is_weak) {
743 assert(!is_native, "weak must not be called off-heap");
744 if (UseCompressedOops) {
745 __ call_VM_leaf(CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier_weak_narrow), c_rarg0, c_rarg1);
746 } else {
747 __ call_VM_leaf(CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier_weak), c_rarg0, c_rarg1);
748 }
749 } else {
750 assert(is_phantom, "only remaining strength");
751 assert(is_native, "phantom must only be called off-heap");
752 __ call_VM_leaf(CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier_phantom), c_rarg0, c_rarg1);
753 }
754
755 __ restore_live_registers_except_rax(true);
756
757 __ epilogue();
758 }
759
760 #undef __
761
762 #endif // COMPILER1
763
764 #ifdef COMPILER2
765
766 #undef __
767 #define __ masm->
768
769 void ShenandoahBarrierSetAssembler::load_c2(const MachNode* node, MacroAssembler* masm, Register dst, Address src, bool narrow) {
770 // Do the actual load. This load is the candidate for implicit null check, and MUST come first.
771 if (narrow) {
772 __ movl(dst, src);
773 } else {
774 __ movq(dst, src);
775 }
776
777 ShenandoahBarrierStubC2::load_post(masm, node, dst, src, noreg, noreg, narrow);
778 }
779
780 void ShenandoahBarrierSetAssembler::store_c2(const MachNode* node, MacroAssembler* masm,
781 Address dst, bool dst_narrow,
782 Register src, bool src_narrow,
783 Register tmp) {
784
785 ShenandoahBarrierStubC2::store_pre(masm, node, dst, tmp, noreg, noreg, dst_narrow);
786
787 // Need to encode into tmp, because we cannot clobber src.
788 if (dst_narrow && !src_narrow) {
789 __ movq(tmp, src);
790 if ((node->barrier_data() & ShenandoahBitNotNull) == 0) {
791 __ encode_heap_oop(tmp);
792 } else {
793 __ encode_heap_oop_not_null(tmp);
794 }
795 src = tmp;
796 }
797
798 // Do the actual store
799 if (dst_narrow) {
800 __ movl(dst, src);
801 } else {
802 __ movq(dst, src);
803 }
804
805 ShenandoahBarrierStubC2::store_post(masm, node, dst, tmp, noreg);
806 }
807
808 void ShenandoahBarrierSetAssembler::compare_and_set_c2(const MachNode* node, MacroAssembler* masm,
809 Register res, Address addr,
810 Register oldval, Register newval, Register tmp,
811 bool narrow) {
812
813 assert(oldval == rax, "must be in rax for implicit use in cmpxchg");
814
815 // Oldval and newval can be in the same register, but all other registers should be
816 // distinct for extra safety, as we shuffle register values around.
817 assert_different_registers(oldval, tmp, addr.base(), addr.index());
818 assert_different_registers(newval, tmp, addr.base(), addr.index());
819
820 ShenandoahBarrierStubC2::load_store_pre(masm, node, addr, tmp, noreg, noreg, narrow);
821
822 // CAS!
823 __ lock();
824 if (narrow) {
825 __ cmpxchgl(newval, addr);
826 } else {
827 __ cmpxchgptr(newval, addr);
828 }
829
830 // If we need a boolean result out of CAS, set the flag appropriately and promote the result.
831 if (res != noreg) {
832 __ setcc(Assembler::equal, res);
833 }
834
835 ShenandoahBarrierStubC2::load_store_post(masm, node, addr, tmp, noreg);
836 }
837
838 void ShenandoahBarrierSetAssembler::get_and_set_c2(const MachNode* node, MacroAssembler* masm, Register newval, Address addr, Register tmp, bool narrow) {
839 assert_different_registers(newval, tmp, addr.base(), addr.index());
840
841 ShenandoahBarrierStubC2::load_store_pre(masm, node, addr, tmp, noreg, noreg, narrow);
842
843 if (narrow) {
844 __ xchgl(newval, addr);
845 } else {
846 __ xchgq(newval, addr);
847 }
848
849 ShenandoahBarrierStubC2::load_store_post(masm, node, addr, tmp, noreg);
850 }
851
852 #undef __
853 #define __ masm.
854
855 void ShenandoahBarrierStubC2::cardtable(MacroAssembler& masm, Address addr, Register tmp1, Register tmp2) {
856 Assembler::InlineSkippedInstructionsCounter skip_counter(&masm);
857
858 __ lea(tmp1, addr);
859 __ shrptr(tmp1, CardTable::card_shift());
860 __ addptr(tmp1, Address(r15_thread, in_bytes(ShenandoahThreadLocalData::card_table_offset())));
861 Address card_address(tmp1, 0);
862
863 assert(CardTable::dirty_card_val() == 0, "Encoding assumption");
864 Label L_done;
865 if (UseCondCardMark) {
866 __ cmpb(card_address, 0);
867 __ jccb(Assembler::equal, L_done);
868 }
869 if (UseCompressedOops && CompressedOops::base() == nullptr) {
870 __ movb(card_address, r12);
871 } else {
872 __ movb(card_address, 0);
873 }
874 __ bind(L_done);
875 }
876
877 void ShenandoahBarrierStubC2::enter_if_gc_state(MacroAssembler& masm, const char test_state, Register tmp) {
878 Assembler::InlineSkippedInstructionsCounter skip_counter(&masm);
879
880 // Emit the unconditional branch in the first version of the method.
881 // Let the rest of runtime figure out how to manage it.
882 __ relocate(barrier_Relocation::spec(), ShenandoahNMethod::gc_state_to_reloc(test_state));
883 __ jmp(*entry(), /* maybe_short = */ false);
884
885 __ bind(*continuation());
886 }
887
888 address ShenandoahBarrierSetAssembler::parse_stub_address(address pc) {
889 NativeInstruction* ni = nativeInstruction_at(pc);
890 assert(ni->is_jump(), "Initial code version: GC barrier fastpath must be a jump");
891 NativeJump* jmp = nativeJump_at(pc);
892 return jmp->jump_destination();
893 }
894
895 static void insert_5_byte_nop(address pc) {
896 *(pc + 0) = 0x0F;
897 *(pc + 1) = 0x1F;
898 *(pc + 2) = 0x44;
899 *(pc + 3) = 0x00;
900 *(pc + 4) = 0x00;
901 ICache::invalidate_range(pc, 5);
902 }
903
904 static bool is_5_byte_nop(address pc) {
905 if (*(pc + 0) != 0x0F) return false;
906 if (*(pc + 1) != 0x1F) return false;
907 if (*(pc + 2) != 0x44) return false;
908 if (*(pc + 3) != 0x00) return false;
909 if (*(pc + 4) != 0x00) return false;
910 return true;
911 }
912
913 static void check_at(bool cond, address pc, const char* msg) {
914 assert(cond, "%s: at PC " PTR_FORMAT ": %02x%02x%02x%02x%02x",
915 msg, p2i(pc), *(pc + 0), *(pc + 1), *(pc + 2), *(pc + 3), *(pc + 4));
916 }
917
918 bool ShenandoahBarrierSetAssembler::is_active(address pc) {
919 NativeInstruction* ni = nativeInstruction_at(pc);
920 return ni->is_jump();
921 }
922
923 void ShenandoahBarrierSetAssembler::patch_branch_to_nop(address pc) {
924 NativeInstruction* ni = nativeInstruction_at(pc);
925 if (ni->is_jump()) {
926 insert_5_byte_nop(pc);
927 } else {
928 check_at(is_5_byte_nop(pc), pc, "Should already be nop");
929 }
930 }
931
932 void ShenandoahBarrierSetAssembler::patch_nop_to_branch(address pc, address stub_addr) {
933 NativeInstruction* ni = nativeInstruction_at(pc);
934 if (is_5_byte_nop(pc)) {
935 NativeJump::insert(pc, stub_addr);
936 } else {
937 check_at(ni->is_jump(), pc, "Should already be jump");
938 check_at(nativeJump_at(pc)->jump_destination() == stub_addr, pc, "Jump should be to the same address");
939 }
940 }
941
942 void ShenandoahBarrierStubC2::emit_code(MacroAssembler& masm) {
943 Assembler::InlineSkippedInstructionsCounter skip_counter(&masm);
944 assert(_needs_keep_alive_barrier || _needs_load_ref_barrier, "Why are you here?");
945
946 // On x86, there is a significant penalty with unaligned branch target, for example
947 // when the target instruction straggles the fetch line. It makes (performance) sense
948 // to spend some code size to align the target better.
949 __ align(16);
950 __ bind(*entry());
951
952 // If we need to load ourselves, do it here.
953 if (_do_load) {
954 if (_narrow) {
955 __ movl(_obj, _addr);
956 } else {
957 __ movq(_obj, _addr);
958 }
959 }
960
961 // If the object is null, there is no point in applying barriers.
962 maybe_far_jump_if_zero(masm, _obj);
963
964 // We need to make sure that loads done by callers survive across slow-path calls.
965 // For self-loads, we need to care about the case when both KA and LRB are enabled (rare).
966 bool needs_both_barriers = _needs_keep_alive_barrier && _needs_load_ref_barrier;
967 if (!_do_load || needs_both_barriers) {
968 preserve(_obj);
969 }
970
971 // Go for barriers. Barriers can return straight to continuation, as long
972 // as another barrier is not needed.
973 if (needs_both_barriers) {
974 keepalive(masm, nullptr);
975 lrb(masm);
976 } else if (_needs_keep_alive_barrier) {
977 keepalive(masm, continuation());
978 } else if (_needs_load_ref_barrier) {
979 lrb(masm);
980 } else {
981 ShouldNotReachHere();
982 }
983 }
984
985 void ShenandoahBarrierStubC2::keepalive(MacroAssembler& masm, Label* L_done) {
986 Address index(r15_thread, in_bytes(ShenandoahThreadLocalData::satb_mark_queue_index_offset()));
987 Address buffer(r15_thread, in_bytes(ShenandoahThreadLocalData::satb_mark_queue_buffer_offset()));
988
989 Label L_through, L_pop_and_slow;
990
991 // If another barrier is enabled as well, do a check for a specific barrier.
992 if (_needs_load_ref_barrier) {
993 assert(L_done == nullptr, "Should be");
994 // Emit the unconditional branch in the first version of the method.
995 // Let the rest of runtime figure out how to manage it.
996 // TODO: We could have spared the over-jump if patching knew we need the inverse branch.
997 char state_to_check = ShenandoahHeap::MARKING;
998 Label L_over;
999 __ relocate(barrier_Relocation::spec(), ShenandoahNMethod::gc_state_to_reloc(state_to_check));
1000 __ jmp(L_over, /* maybe_short = */ false);
1001 __ jmp(L_through);
1002 __ bind(L_over);
1003 }
1004
1005 // Need temp to work, allocate one now.
1006 bool tmp_live;
1007 Register tmp = select_temp_register(tmp_live);
1008 if (tmp_live) {
1009 __ push(tmp);
1010 }
1011
1012 // Fast-path: put object into buffer.
1013 // If buffer is already full, go slow.
1014 __ movptr(tmp, index);
1015 __ subptr(tmp, wordSize);
1016 __ jccb(Assembler::below, L_pop_and_slow);
1017 __ movptr(index, tmp);
1018 __ addptr(tmp, buffer);
1019
1020 // Store the object in queue.
1021 // If object is narrow, we need to decode it before inserting.
1022 // We can skip the re-encoding if we know that object is not preserved.
1023 if (_narrow) {
1024 __ decode_heap_oop_not_null(_obj);
1025 }
1026 __ movptr(Address(tmp, 0), _obj);
1027 if (_narrow && is_preserved(_obj)) {
1028 __ encode_heap_oop_not_null(_obj);
1029 }
1030
1031 // Fast-path exits here.
1032 if (tmp_live) {
1033 __ pop(tmp);
1034 }
1035
1036 if (L_done != nullptr) {
1037 __ jmp(*L_done);
1038 } else {
1039 __ jmp(L_through);
1040 }
1041
1042 // Slow-path: call runtime to handle.
1043 // Need to pop tmp immediately for stack to remain aligned.
1044 __ bind(L_pop_and_slow);
1045 if (tmp_live) {
1046 __ pop(tmp);
1047 }
1048 {
1049 SaveLiveRegisters slr(&masm, this);
1050
1051 // Shuffle in the arguments. The end result should be:
1052 // c_rarg0 <-- obj
1053 if (c_rarg0 != _obj) {
1054 __ mov(c_rarg0, _obj);
1055 }
1056
1057 // Go to runtime and handle the rest there.
1058 // Use rax as scratch, as it will be saved if live.
1059 __ call(RuntimeAddress(keepalive_runtime_entry_addr()), rax);
1060 }
1061 if (L_done != nullptr) {
1062 __ jmp(*L_done);
1063 } else {
1064 __ bind(L_through);
1065 }
1066 }
1067
1068 void ShenandoahBarrierStubC2::lrb(MacroAssembler& masm) {
1069 Label L_pop_and_slow, L_slow;
1070
1071 // If weak references are being processed, weak/phantom loads need to go slow,
1072 // regardless of their cset status.
1073 if (_needs_load_ref_weak_barrier) {
1074 char state_to_check = ShenandoahHeap::WEAK_ROOTS;
1075 __ relocate(barrier_Relocation::spec(), ShenandoahNMethod::gc_state_to_reloc(state_to_check));
1076 __ jmp(L_slow, /* maybe_short = */ false);
1077 }
1078
1079 if (_needs_keep_alive_barrier) {
1080 // Emit the unconditional branch in the first version of the method.
1081 // Let the rest of runtime figure out how to manage it.
1082 // TODO: We could have spared the over-jump if patching knew we need the inverse branch.
1083 char state_to_check = ShenandoahHeap::HAS_FORWARDED | (_needs_load_ref_weak_barrier ? ShenandoahHeap::WEAK_ROOTS : 0);
1084 Label L_over;
1085 __ relocate(barrier_Relocation::spec(), ShenandoahNMethod::gc_state_to_reloc(state_to_check));
1086 __ jmp(L_over, /* maybe_short = */ false);
1087 __ jmp(*continuation());
1088 __ bind(L_over);
1089 }
1090
1091 bool is_aot = AOTCodeCache::is_on_for_dump();
1092
1093 // Need temp to work, allocate one now.
1094 bool tmp_live;
1095 Register tmp = select_temp_register(tmp_live, /* skip_reg1 = */ is_aot ? rcx : noreg);
1096 if (tmp_live) {
1097 __ push(tmp);
1098 }
1099
1100 // Compute the cset bitmap index
1101 if (_narrow) {
1102 __ decode_heap_oop_not_null(tmp, _obj);
1103 } else {
1104 __ movptr(tmp, _obj);
1105 }
1106
1107 Address cset_addr_arg;
1108 intptr_t cset_addr = reinterpret_cast<intptr_t>(ShenandoahHeap::in_cset_fast_test_addr());
1109 if (!is_aot && cset_addr < INT32_MAX) {
1110 // Cset bitmap is at easily encodeable address. Just use it as displacement.
1111 __ shrptr(tmp, ShenandoahHeapRegion::region_size_bytes_shift_jint());
1112 cset_addr_arg = Address(tmp, checked_cast<int>(cset_addr));
1113 } else {
1114 bool tmp2_live;
1115 Register tmp2 = select_temp_register(tmp2_live, /* skip_reg1 = */ tmp, /* skip_reg2 = */ is_aot ? rcx : noreg);
1116 if (tmp2_live) {
1117 __ push(tmp2);
1118 }
1119 if (is_aot) {
1120 // Generating AOT code, pull the cset bitmap and region shift from AOT table.
1121 assert_different_registers(tmp, tmp2, rcx);
1122 __ push(rcx);
1123 __ lea(rcx, ExternalAddress(AOTRuntimeConstants::grain_shift_address()));
1124 __ movl(rcx, Address(rcx));
1125 __ shrptr(tmp);
1126 __ pop(rcx);
1127 __ lea(tmp2, ExternalAddress(AOTRuntimeConstants::cset_base_address()));
1128 __ addptr(tmp, Address(tmp2));
1129 } else {
1130 // Cset bitmap is far away. Add its address fully.
1131 __ shrptr(tmp, ShenandoahHeapRegion::region_size_bytes_shift_jint());
1132 __ movptr(tmp2, cset_addr);
1133 __ addptr(tmp, tmp2);
1134 }
1135 if (tmp2_live) {
1136 __ pop(tmp2);
1137 }
1138 cset_addr_arg = Address(tmp, 0);
1139 }
1140
1141 // Cset-check. Fall-through to slow if in collection set.
1142 __ cmpb(cset_addr_arg, 0);
1143 if (tmp_live) {
1144 __ jccb(Assembler::notEqual, L_pop_and_slow);
1145 __ pop(tmp);
1146 __ jmp(*continuation());
1147 } else {
1148 // Nothing else to do, jump back
1149 __ jcc(Assembler::equal, *continuation());
1150 }
1151
1152 // Slow path
1153 __ bind(L_pop_and_slow);
1154 // Need to pop tmp immediately for stack to remain aligned.
1155 if (tmp_live) {
1156 __ pop(tmp);
1157 }
1158 __ bind(L_slow);
1159
1160 // Obj is the result, need to temporarily stop preserving it.
1161 bool is_obj_preserved = is_preserved(_obj);
1162 if (is_obj_preserved) {
1163 dont_preserve(_obj);
1164 }
1165 {
1166 SaveLiveRegisters slr(&masm, this);
1167
1168 assert_different_registers(rax, c_rarg0, c_rarg1);
1169
1170 // Shuffle in the arguments. The end result should be:
1171 // c_rarg0 <-- obj
1172 // c_rarg1 <-- lea(addr)
1173 if (_obj == c_rarg0) {
1174 __ lea(c_rarg1, _addr);
1175 } else if (_obj == c_rarg1) {
1176 // Set up arguments in reverse, and then flip them
1177 __ lea(c_rarg0, _addr);
1178 __ xchgptr(c_rarg0, c_rarg1);
1179 } else {
1180 assert_different_registers(_obj, c_rarg0, c_rarg1);
1181 __ lea(c_rarg1, _addr);
1182 __ movptr(c_rarg0, _obj);
1183 }
1184
1185 // Go to runtime and handle the rest there.
1186 // Use rax as scratch, as it will be clobbered by result anyway.
1187 __ call(RuntimeAddress(lrb_runtime_entry_addr()), rax);
1188
1189 // Save the result where needed.
1190 if (_narrow) {
1191 __ movl(_obj, rax);
1192 } else if (_obj != rax) {
1193 __ movptr(_obj, rax);
1194 }
1195 }
1196 if (is_obj_preserved) {
1197 preserve(_obj);
1198 }
1199
1200 __ jmp(*continuation());
1201 }
1202
1203 int ShenandoahBarrierStubC2::available_gp_registers() {
1204 return Register::available_gp_registers();
1205 }
1206
1207 bool ShenandoahBarrierStubC2::is_special_register(Register r) {
1208 return r == rsp || r == rbp || r == r12_heapbase || r == r15_thread;
1209 }
1210
1211 void ShenandoahBarrierStubC2::post_init() {
1212 // Do nothing.
1213 }
1214
1215 void ShenandoahBarrierStubC2::maybe_far_jump_if_zero(MacroAssembler& masm, Register reg) {
1216 if (_narrow) {
1217 __ testl(reg, reg);
1218 } else {
1219 __ testq(reg, reg);
1220 }
1221 __ jcc(Assembler::zero, *continuation());
1222 }
1223
1224 #endif // COMPILER2