1 /*
2 * Copyright (c) 2018, 2021, Red Hat, Inc. 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 "gc/shenandoah/shenandoahBarrierSet.hpp"
27 #include "gc/shenandoah/shenandoahBarrierSetAssembler.hpp"
28 #include "gc/shenandoah/shenandoahForwarding.hpp"
29 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
30 #include "gc/shenandoah/shenandoahHeapRegion.hpp"
31 #include "gc/shenandoah/shenandoahRuntime.hpp"
32 #include "gc/shenandoah/shenandoahThreadLocalData.hpp"
33 #include "gc/shenandoah/heuristics/shenandoahHeuristics.hpp"
34 #include "gc/shenandoah/mode/shenandoahMode.hpp"
35 #include "interpreter/interpreter.hpp"
36 #include "interpreter/interp_masm.hpp"
37 #include "runtime/sharedRuntime.hpp"
38 #include "runtime/thread.hpp"
39 #ifdef COMPILER1
40 #include "c1/c1_LIRAssembler.hpp"
41 #include "c1/c1_MacroAssembler.hpp"
42 #include "gc/shenandoah/c1/shenandoahBarrierSetC1.hpp"
43 #endif
44
45 #define __ masm->
46
47 void ShenandoahBarrierSetAssembler::arraycopy_prologue(MacroAssembler* masm, DecoratorSet decorators, bool is_oop,
48 Register src, Register dst, Register count, RegSet saved_regs) {
49 if (is_oop) {
50 bool dest_uninitialized = (decorators & IS_DEST_UNINITIALIZED) != 0;
51 if ((ShenandoahSATBBarrier && !dest_uninitialized) || ShenandoahIUBarrier || ShenandoahLoadRefBarrier) {
52
53 Label done;
54
55 // Avoid calling runtime if count == 0
56 __ cbz(count, done);
57
58 // Is GC active?
59 Address gc_state(rthread, in_bytes(ShenandoahThreadLocalData::gc_state_offset()));
60 __ ldrb(rscratch1, gc_state);
61 if (ShenandoahSATBBarrier && dest_uninitialized) {
62 __ tbz(rscratch1, ShenandoahHeap::HAS_FORWARDED_BITPOS, done);
63 } else {
64 __ mov(rscratch2, ShenandoahHeap::HAS_FORWARDED | ShenandoahHeap::YOUNG_MARKING | ShenandoahHeap::OLD_MARKING);
65 __ tst(rscratch1, rscratch2);
66 __ br(Assembler::EQ, done);
67 }
68
69 __ push(saved_regs, sp);
70 if (UseCompressedOops) {
71 __ call_VM_leaf(CAST_FROM_FN_PTR(address, ShenandoahRuntime::arraycopy_barrier_narrow_oop_entry), src, dst, count);
72 } else {
73 __ call_VM_leaf(CAST_FROM_FN_PTR(address, ShenandoahRuntime::arraycopy_barrier_oop_entry), src, dst, count);
74 }
75 __ pop(saved_regs, sp);
76 __ bind(done);
77 }
78 }
79 }
80
81 void ShenandoahBarrierSetAssembler::arraycopy_epilogue(MacroAssembler* masm, DecoratorSet decorators, bool is_oop,
82 Register start, Register count, Register tmp, RegSet saved_regs) {
83 if (is_oop) {
84 gen_write_ref_array_post_barrier(masm, decorators, start, count, tmp, saved_regs);
85 }
86 }
87
88 void ShenandoahBarrierSetAssembler::shenandoah_write_barrier_pre(MacroAssembler* masm,
89 Register obj,
90 Register pre_val,
91 Register thread,
92 Register tmp,
93 bool tosca_live,
94 bool expand_call) {
95 if (ShenandoahSATBBarrier) {
96 satb_write_barrier_pre(masm, obj, pre_val, thread, tmp, tosca_live, expand_call);
97 }
98 }
99
100 void ShenandoahBarrierSetAssembler::satb_write_barrier_pre(MacroAssembler* masm,
101 Register obj,
102 Register pre_val,
103 Register thread,
104 Register tmp,
105 bool tosca_live,
106 bool expand_call) {
107 // If expand_call is true then we expand the call_VM_leaf macro
108 // directly to skip generating the check by
109 // InterpreterMacroAssembler::call_VM_leaf_base that checks _last_sp.
110
111 assert(thread == rthread, "must be");
112
113 Label done;
114 Label runtime;
115
116 assert_different_registers(obj, pre_val, tmp, rscratch1);
117 assert(pre_val != noreg && tmp != noreg, "expecting a register");
118
119 Address in_progress(thread, in_bytes(ShenandoahThreadLocalData::satb_mark_queue_active_offset()));
120 Address index(thread, in_bytes(ShenandoahThreadLocalData::satb_mark_queue_index_offset()));
121 Address buffer(thread, in_bytes(ShenandoahThreadLocalData::satb_mark_queue_buffer_offset()));
122
123 // Is marking active?
124 if (in_bytes(SATBMarkQueue::byte_width_of_active()) == 4) {
125 __ ldrw(tmp, in_progress);
126 } else {
127 assert(in_bytes(SATBMarkQueue::byte_width_of_active()) == 1, "Assumption");
128 __ ldrb(tmp, in_progress);
129 }
130 __ cbzw(tmp, done);
131
132 // Do we need to load the previous value?
133 if (obj != noreg) {
134 __ load_heap_oop(pre_val, Address(obj, 0), noreg, noreg, AS_RAW);
135 }
136
137 // Is the previous value null?
138 __ cbz(pre_val, done);
139
140 // Can we store original value in the thread's buffer?
141 // Is index == 0?
142 // (The index field is typed as size_t.)
143
144 __ ldr(tmp, index); // tmp := *index_adr
145 __ cbz(tmp, runtime); // tmp == 0?
146 // If yes, goto runtime
147
148 __ sub(tmp, tmp, wordSize); // tmp := tmp - wordSize
149 __ str(tmp, index); // *index_adr := tmp
150 __ ldr(rscratch1, buffer);
151 __ add(tmp, tmp, rscratch1); // tmp := tmp + *buffer_adr
152
153 // Record the previous value
154 __ str(pre_val, Address(tmp, 0));
155 __ b(done);
156
157 __ bind(runtime);
158 // save the live input values
159 RegSet saved = RegSet::of(pre_val);
160 if (tosca_live) saved += RegSet::of(r0);
161 if (obj != noreg) saved += RegSet::of(obj);
162
163 __ push(saved, sp);
164
165 // Calling the runtime using the regular call_VM_leaf mechanism generates
166 // code (generated by InterpreterMacroAssember::call_VM_leaf_base)
167 // that checks that the *(rfp+frame::interpreter_frame_last_sp) == NULL.
168 //
169 // If we care generating the pre-barrier without a frame (e.g. in the
170 // intrinsified Reference.get() routine) then ebp might be pointing to
171 // the caller frame and so this check will most likely fail at runtime.
172 //
173 // Expanding the call directly bypasses the generation of the check.
174 // So when we do not have have a full interpreter frame on the stack
175 // expand_call should be passed true.
176
177 if (expand_call) {
178 assert(pre_val != c_rarg1, "smashed arg");
179 __ super_call_VM_leaf(CAST_FROM_FN_PTR(address, ShenandoahRuntime::write_ref_field_pre_entry), pre_val, thread);
180 } else {
181 __ call_VM_leaf(CAST_FROM_FN_PTR(address, ShenandoahRuntime::write_ref_field_pre_entry), pre_val, thread);
182 }
183
184 __ pop(saved, sp);
185
186 __ bind(done);
187 }
188
189 void ShenandoahBarrierSetAssembler::resolve_forward_pointer(MacroAssembler* masm, Register dst, Register tmp) {
190 assert(ShenandoahLoadRefBarrier || ShenandoahCASBarrier, "Should be enabled");
191 Label is_null;
192 __ cbz(dst, is_null);
193 resolve_forward_pointer_not_null(masm, dst, tmp);
194 __ bind(is_null);
195 }
196
197 // IMPORTANT: This must preserve all registers, even rscratch1 and rscratch2, except those explicitely
198 // passed in.
199 void ShenandoahBarrierSetAssembler::resolve_forward_pointer_not_null(MacroAssembler* masm, Register dst, Register tmp) {
200 assert(ShenandoahLoadRefBarrier || ShenandoahCASBarrier, "Should be enabled");
201 // The below loads the mark word, checks if the lowest two bits are
202 // set, and if so, clear the lowest two bits and copy the result
203 // to dst. Otherwise it leaves dst alone.
204 // Implementing this is surprisingly awkward. I do it here by:
205 // - Inverting the mark word
206 // - Test lowest two bits == 0
207 // - If so, set the lowest two bits
208 // - Invert the result back, and copy to dst
209
210 bool borrow_reg = (tmp == noreg);
211 if (borrow_reg) {
212 // No free registers available. Make one useful.
213 tmp = rscratch1;
214 if (tmp == dst) {
215 tmp = rscratch2;
216 }
217 __ push(RegSet::of(tmp), sp);
218 }
219
220 assert_different_registers(tmp, dst);
221
222 Label done;
223 __ ldr(tmp, Address(dst, oopDesc::mark_offset_in_bytes()));
224 __ eon(tmp, tmp, zr);
225 __ ands(zr, tmp, markWord::lock_mask_in_place);
226 __ br(Assembler::NE, done);
227 __ orr(tmp, tmp, markWord::marked_value);
228 __ eon(dst, tmp, zr);
229 __ bind(done);
230
231 if (borrow_reg) {
232 __ pop(RegSet::of(tmp), sp);
233 }
234 }
235
236 void ShenandoahBarrierSetAssembler::load_reference_barrier(MacroAssembler* masm, Register dst, Address load_addr, DecoratorSet decorators) {
237 assert(ShenandoahLoadRefBarrier, "Should be enabled");
238 assert(dst != rscratch2, "need rscratch2");
239 assert_different_registers(load_addr.base(), load_addr.index(), rscratch1, rscratch2);
240
241 bool is_strong = ShenandoahBarrierSet::is_strong_access(decorators);
242 bool is_weak = ShenandoahBarrierSet::is_weak_access(decorators);
243 bool is_phantom = ShenandoahBarrierSet::is_phantom_access(decorators);
244 bool is_native = ShenandoahBarrierSet::is_native_access(decorators);
245 bool is_narrow = UseCompressedOops && !is_native;
246
247 Label heap_stable, not_cset;
248 __ enter();
249 Address gc_state(rthread, in_bytes(ShenandoahThreadLocalData::gc_state_offset()));
250 __ ldrb(rscratch2, gc_state);
251
252 // Check for heap stability
253 if (is_strong) {
254 __ tbz(rscratch2, ShenandoahHeap::HAS_FORWARDED_BITPOS, heap_stable);
255 } else {
256 Label lrb;
257 __ tbnz(rscratch2, ShenandoahHeap::WEAK_ROOTS_BITPOS, lrb);
258 __ tbz(rscratch2, ShenandoahHeap::HAS_FORWARDED_BITPOS, heap_stable);
259 __ bind(lrb);
260 }
261
262 // use r1 for load address
263 Register result_dst = dst;
264 if (dst == r1) {
265 __ mov(rscratch1, dst);
266 dst = rscratch1;
267 }
268
269 // Save r0 and r1, unless it is an output register
270 RegSet to_save = RegSet::of(r0, r1) - result_dst;
271 __ push(to_save, sp);
272 __ lea(r1, load_addr);
273 __ mov(r0, dst);
274
275 // Test for in-cset
276 if (is_strong) {
277 __ mov(rscratch2, ShenandoahHeap::in_cset_fast_test_addr());
278 __ lsr(rscratch1, r0, ShenandoahHeapRegion::region_size_bytes_shift_jint());
279 __ ldrb(rscratch2, Address(rscratch2, rscratch1));
280 __ tbz(rscratch2, 0, not_cset);
281 }
282
283 __ push_call_clobbered_registers();
284 if (is_strong) {
285 if (is_narrow) {
286 __ mov(lr, CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier_strong_narrow));
287 } else {
288 __ mov(lr, CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier_strong));
289 }
290 } else if (is_weak) {
291 if (is_narrow) {
292 __ mov(lr, CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier_weak_narrow));
293 } else {
294 __ mov(lr, CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier_weak));
295 }
296 } else {
297 assert(is_phantom, "only remaining strength");
298 assert(!is_narrow, "phantom access cannot be narrow");
299 __ mov(lr, CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier_phantom));
300 }
301 __ blr(lr);
302 __ mov(rscratch1, r0);
303 __ pop_call_clobbered_registers();
304 __ mov(r0, rscratch1);
305
306 __ bind(not_cset);
307
308 __ mov(result_dst, r0);
309 __ pop(to_save, sp);
310
311 __ bind(heap_stable);
312 __ leave();
313 }
314
315 void ShenandoahBarrierSetAssembler::iu_barrier(MacroAssembler* masm, Register dst, Register tmp) {
316 if (ShenandoahIUBarrier) {
317 __ push_call_clobbered_registers();
318 satb_write_barrier_pre(masm, noreg, dst, rthread, tmp, true, false);
319 __ pop_call_clobbered_registers();
320 }
321 }
322
323 //
324 // Arguments:
325 //
326 // Inputs:
327 // src: oop location to load from, might be clobbered
328 //
329 // Output:
330 // dst: oop loaded from src location
331 //
332 // Kill:
333 // rscratch1 (scratch reg)
334 //
335 // Alias:
336 // dst: rscratch1 (might use rscratch1 as temporary output register to avoid clobbering src)
337 //
338 void ShenandoahBarrierSetAssembler::load_at(MacroAssembler* masm, DecoratorSet decorators, BasicType type,
339 Register dst, Address src, Register tmp1, Register tmp_thread) {
340 // 1: non-reference load, no additional barrier is needed
341 if (!is_reference_type(type)) {
342 BarrierSetAssembler::load_at(masm, decorators, type, dst, src, tmp1, tmp_thread);
343 return;
344 }
345
346 // 2: load a reference from src location and apply LRB if needed
347 if (ShenandoahBarrierSet::need_load_reference_barrier(decorators, type)) {
348 Register result_dst = dst;
349
350 // Preserve src location for LRB
351 if (dst == src.base() || dst == src.index()) {
352 dst = rscratch1;
353 }
354 assert_different_registers(dst, src.base(), src.index());
355
356 BarrierSetAssembler::load_at(masm, decorators, type, dst, src, tmp1, tmp_thread);
357
358 load_reference_barrier(masm, dst, src, decorators);
359
360 if (dst != result_dst) {
361 __ mov(result_dst, dst);
362 dst = result_dst;
363 }
364 } else {
365 BarrierSetAssembler::load_at(masm, decorators, type, dst, src, tmp1, tmp_thread);
366 }
367
368 // 3: apply keep-alive barrier if needed
369 if (ShenandoahBarrierSet::need_keep_alive_barrier(decorators, type)) {
370 __ enter();
371 __ push_call_clobbered_registers();
372 satb_write_barrier_pre(masm /* masm */,
373 noreg /* obj */,
374 dst /* pre_val */,
375 rthread /* thread */,
376 tmp1 /* tmp */,
377 true /* tosca_live */,
378 true /* expand_call */);
379 __ pop_call_clobbered_registers();
380 __ leave();
381 }
382 }
383
384 void ShenandoahBarrierSetAssembler::store_check(MacroAssembler* masm, Register obj) {
385 if (!ShenandoahHeap::heap()->mode()->is_generational()) {
386 return;
387 }
388
389 ShenandoahBarrierSet* ctbs = ShenandoahBarrierSet::barrier_set();
390 CardTable* ct = ctbs->card_table();
391
392 __ lsr(obj, obj, CardTable::card_shift());
393
394 assert(CardTable::dirty_card_val() == 0, "must be");
395
396 __ load_byte_map_base(rscratch1);
397
398 if (UseCondCardMark) {
399 Label L_already_dirty;
400 __ ldrb(rscratch2, Address(obj, rscratch1));
401 __ cbz(rscratch2, L_already_dirty);
402 __ strb(zr, Address(obj, rscratch1));
403 __ bind(L_already_dirty);
404 } else {
405 __ strb(zr, Address(obj, rscratch1));
406 }
407 }
408
409 void ShenandoahBarrierSetAssembler::store_at(MacroAssembler* masm, DecoratorSet decorators, BasicType type,
410 Address dst, Register val, Register tmp1, Register tmp2) {
411 bool on_oop = is_reference_type(type);
412 if (!on_oop) {
413 BarrierSetAssembler::store_at(masm, decorators, type, dst, val, tmp1, tmp2);
414 return;
415 }
416
417 // flatten object address if needed
418 if (dst.index() == noreg && dst.offset() == 0) {
419 if (dst.base() != r3) {
420 __ mov(r3, dst.base());
421 }
422 } else {
423 __ lea(r3, dst);
424 }
425
426 shenandoah_write_barrier_pre(masm,
427 r3 /* obj */,
428 tmp2 /* pre_val */,
429 rthread /* thread */,
430 tmp1 /* tmp */,
431 val != noreg /* tosca_live */,
432 false /* expand_call */);
433
434 if (val == noreg) {
435 BarrierSetAssembler::store_at(masm, decorators, type, Address(r3, 0), noreg, noreg, noreg);
436 } else {
437 iu_barrier(masm, val, tmp1);
438 // G1 barrier needs uncompressed oop for region cross check.
439 Register new_val = val;
440 if (UseCompressedOops) {
441 new_val = rscratch2;
442 __ mov(new_val, val);
443 }
444 BarrierSetAssembler::store_at(masm, decorators, type, Address(r3, 0), val, noreg, noreg);
445 store_check(masm, r3);
446 }
447
448 }
449
450 void ShenandoahBarrierSetAssembler::try_resolve_jobject_in_native(MacroAssembler* masm, Register jni_env,
451 Register obj, Register tmp, Label& slowpath) {
452 Label done;
453 // Resolve jobject
454 BarrierSetAssembler::try_resolve_jobject_in_native(masm, jni_env, obj, tmp, slowpath);
455
456 // Check for null.
457 __ cbz(obj, done);
458
459 assert(obj != rscratch2, "need rscratch2");
460 Address gc_state(jni_env, ShenandoahThreadLocalData::gc_state_offset() - JavaThread::jni_environment_offset());
461 __ lea(rscratch2, gc_state);
462 __ ldrb(rscratch2, Address(rscratch2));
463
464 // Check for heap in evacuation phase
465 __ tbnz(rscratch2, ShenandoahHeap::EVACUATION_BITPOS, slowpath);
466
467 __ bind(done);
468 }
469
470 // Special Shenandoah CAS implementation that handles false negatives due
471 // to concurrent evacuation. The service is more complex than a
472 // traditional CAS operation because the CAS operation is intended to
473 // succeed if the reference at addr exactly matches expected or if the
474 // reference at addr holds a pointer to a from-space object that has
475 // been relocated to the location named by expected. There are two
476 // races that must be addressed:
477 // a) A parallel thread may mutate the contents of addr so that it points
478 // to a different object. In this case, the CAS operation should fail.
479 // b) A parallel thread may heal the contents of addr, replacing a
480 // from-space pointer held in addr with the to-space pointer
481 // representing the new location of the object.
482 // Upon entry to cmpxchg_oop, it is assured that new_val equals NULL
483 // or it refers to an object that is not being evacuated out of
484 // from-space, or it refers to the to-space version of an object that
485 // is being evacuated out of from-space.
486 //
487 // By default the value held in the result register following execution
488 // of the generated code sequence is 0 to indicate failure of CAS,
489 // non-zero to indicate success. If is_cae, the result is the value most
490 // recently fetched from addr rather than a boolean success indicator.
491 //
492 // Clobbers rscratch1, rscratch2
493 void ShenandoahBarrierSetAssembler::cmpxchg_oop(MacroAssembler* masm,
494 Register addr,
495 Register expected,
496 Register new_val,
497 bool acquire, bool release,
498 bool is_cae,
499 Register result) {
500 Register tmp1 = rscratch1;
501 Register tmp2 = rscratch2;
502 bool is_narrow = UseCompressedOops;
503 Assembler::operand_size size = is_narrow ? Assembler::word : Assembler::xword;
504
505 assert_different_registers(addr, expected, tmp1, tmp2);
506 assert_different_registers(addr, new_val, tmp1, tmp2);
507
508 Label step4, done;
509
510 // There are two ways to reach this label. Initial entry into the
511 // cmpxchg_oop code expansion starts at step1 (which is equivalent
512 // to label step4). Additionally, in the rare case that four steps
513 // are required to perform the requested operation, the fourth step
514 // is the same as the first. On a second pass through step 1,
515 // control may flow through step 2 on its way to failure. It will
516 // not flow from step 2 to step 3 since we are assured that the
517 // memory at addr no longer holds a from-space pointer.
518 //
519 // The comments that immediately follow the step4 label apply only
520 // to the case in which control reaches this label by branch from
521 // step 3.
522
523 __ bind (step4);
524
525 // Step 4. CAS has failed because the value most recently fetched
526 // from addr is no longer the from-space pointer held in tmp2. If a
527 // different thread replaced the in-memory value with its equivalent
528 // to-space pointer, then CAS may still be able to succeed. The
529 // value held in the expected register has not changed.
530 //
531 // It is extremely rare we reach this point. For this reason, the
532 // implementation opts for smaller rather than potentially faster
533 // code. Ultimately, smaller code for this rare case most likely
534 // delivers higher overall throughput by enabling improved icache
535 // performance.
536
537 // Step 1. Fast-path.
538 //
539 // Try to CAS with given arguments. If successful, then we are done.
540 //
541 // No label required for step 1.
542
543 __ cmpxchg(addr, expected, new_val, size, acquire, release, false, tmp2);
544 // EQ flag set iff success. tmp2 holds value fetched.
545
546 // If expected equals null but tmp2 does not equal null, the
547 // following branches to done to report failure of CAS. If both
548 // expected and tmp2 equal null, the following branches to done to
549 // report success of CAS. There's no need for a special test of
550 // expected equal to null.
551
552 __ br(Assembler::EQ, done);
553 // if CAS failed, fall through to step 2
554
555 // Step 2. CAS has failed because the value held at addr does not
556 // match expected. This may be a false negative because the value fetched
557 // from addr (now held in tmp2) may be a from-space pointer to the
558 // original copy of same object referenced by to-space pointer expected.
559 //
560 // To resolve this, it suffices to find the forward pointer associated
561 // with fetched value. If this matches expected, retry CAS with new
562 // parameters. If this mismatches, then we have a legitimate
563 // failure, and we're done.
564 //
565 // No need for step2 label.
566
567 // overwrite tmp1 with from-space pointer fetched from memory
568 __ mov(tmp1, tmp2);
569
570 if (is_narrow) {
571 // Decode tmp1 in order to resolve its forward pointer
572 __ decode_heap_oop(tmp1, tmp1);
573 }
574 resolve_forward_pointer(masm, tmp1);
575 // Encode tmp1 to compare against expected.
576 __ encode_heap_oop(tmp1, tmp1);
577
578 // Does forwarded value of fetched from-space pointer match original
579 // value of expected? If tmp1 holds null, this comparison will fail
580 // because we know from step1 that expected is not null. There is
581 // no need for a separate test for tmp1 (the value originally held
582 // in memory) equal to null.
583 __ cmp(tmp1, expected);
584
585 // If not, then the failure was legitimate and we're done.
586 // Branching to done with NE condition denotes failure.
587 __ br(Assembler::NE, done);
588
589 // Fall through to step 3. No need for step3 label.
590
591 // Step 3. We've confirmed that the value originally held in memory
592 // (now held in tmp2) pointed to from-space version of original
593 // expected value. Try the CAS again with the from-space expected
594 // value. If it now succeeds, we're good.
595 //
596 // Note: tmp2 holds encoded from-space pointer that matches to-space
597 // object residing at expected. tmp2 is the new "expected".
598
599 // Note that macro implementation of __cmpxchg cannot use same register
600 // tmp2 for result and expected since it overwrites result before it
601 // compares result with expected.
602 __ cmpxchg(addr, tmp2, new_val, size, acquire, release, false, noreg);
603 // EQ flag set iff success. tmp2 holds value fetched, tmp1 (rscratch1) clobbered.
604
605 // If fetched value did not equal the new expected, this could
606 // still be a false negative because some other thread may have
607 // newly overwritten the memory value with its to-space equivalent.
608 __ br(Assembler::NE, step4);
609
610 if (is_cae) {
611 // We're falling through to done to indicate success. Success
612 // with is_cae is denoted by returning the value of expected as
613 // result.
614 __ mov(tmp2, expected);
615 }
616
617 __ bind(done);
618 // At entry to done, the Z (EQ) flag is on iff if the CAS
619 // operation was successful. Additionally, if is_cae, tmp2 holds
620 // the value most recently fetched from addr. In this case, success
621 // is denoted by tmp2 matching expected.
622
623 if (is_cae) {
624 __ mov(result, tmp2);
625 } else {
626 __ cset(result, Assembler::EQ);
627 }
628 }
629
630 void ShenandoahBarrierSetAssembler::gen_write_ref_array_post_barrier(MacroAssembler* masm, DecoratorSet decorators,
631 Register start, Register count, Register scratch, RegSet saved_regs) {
632 if (!ShenandoahHeap::heap()->mode()->is_generational()) {
633 return;
634 }
635
636 ShenandoahBarrierSet* bs = ShenandoahBarrierSet::barrier_set();
637 CardTable* ct = bs->card_table();
638
639 Label L_loop, L_done;
640 const Register end = count;
641
642 __ cbz(count, L_done); // zero count - nothing to do
643
644 __ lea(end, Address(start, count, Address::lsl(LogBytesPerHeapOop))); // end = start + count << LogBytesPerHeapOop
645 __ sub(end, end, BytesPerHeapOop); // last element address to make inclusive
646 __ lsr(start, start, CardTable::card_shift());
647 __ lsr(end, end, CardTable::card_shift());
648 __ sub(count, end, start); // number of bytes to copy
649
650 __ load_byte_map_base(scratch);
651 __ add(start, start, scratch);
652 __ bind(L_loop);
653 __ strb(zr, Address(start, count));
654 __ subs(count, count, 1);
655 __ br(Assembler::GE, L_loop);
656 __ bind(L_done);
657 }
658
659 #undef __
660
661 #ifdef COMPILER1
662
663 #define __ ce->masm()->
664
665 void ShenandoahBarrierSetAssembler::gen_pre_barrier_stub(LIR_Assembler* ce, ShenandoahPreBarrierStub* stub) {
666 ShenandoahBarrierSetC1* bs = (ShenandoahBarrierSetC1*)BarrierSet::barrier_set()->barrier_set_c1();
667 // At this point we know that marking is in progress.
668 // If do_load() is true then we have to emit the
669 // load of the previous value; otherwise it has already
670 // been loaded into _pre_val.
671
672 __ bind(*stub->entry());
673
674 assert(stub->pre_val()->is_register(), "Precondition.");
675
676 Register pre_val_reg = stub->pre_val()->as_register();
677
678 if (stub->do_load()) {
679 ce->mem2reg(stub->addr(), stub->pre_val(), T_OBJECT, stub->patch_code(), stub->info(), false /*wide*/);
680 }
681 __ cbz(pre_val_reg, *stub->continuation());
682 ce->store_parameter(stub->pre_val()->as_register(), 0);
683 __ far_call(RuntimeAddress(bs->pre_barrier_c1_runtime_code_blob()->code_begin()));
684 __ b(*stub->continuation());
685 }
686
687 void ShenandoahBarrierSetAssembler::gen_load_reference_barrier_stub(LIR_Assembler* ce, ShenandoahLoadReferenceBarrierStub* stub) {
688 ShenandoahBarrierSetC1* bs = (ShenandoahBarrierSetC1*)BarrierSet::barrier_set()->barrier_set_c1();
689 __ bind(*stub->entry());
690
691 DecoratorSet decorators = stub->decorators();
692 bool is_strong = ShenandoahBarrierSet::is_strong_access(decorators);
693 bool is_weak = ShenandoahBarrierSet::is_weak_access(decorators);
694 bool is_phantom = ShenandoahBarrierSet::is_phantom_access(decorators);
695 bool is_native = ShenandoahBarrierSet::is_native_access(decorators);
696
697 Register obj = stub->obj()->as_register();
698 Register res = stub->result()->as_register();
699 Register addr = stub->addr()->as_pointer_register();
700 Register tmp1 = stub->tmp1()->as_register();
701 Register tmp2 = stub->tmp2()->as_register();
702
703 assert(res == r0, "result must arrive in r0");
704
705 if (res != obj) {
706 __ mov(res, obj);
707 }
708
709 if (is_strong) {
710 // Check for object in cset.
711 __ mov(tmp2, ShenandoahHeap::in_cset_fast_test_addr());
712 __ lsr(tmp1, res, ShenandoahHeapRegion::region_size_bytes_shift_jint());
713 __ ldrb(tmp2, Address(tmp2, tmp1));
714 __ cbz(tmp2, *stub->continuation());
715 }
716
717 ce->store_parameter(res, 0);
718 ce->store_parameter(addr, 1);
719 if (is_strong) {
720 if (is_native) {
721 __ far_call(RuntimeAddress(bs->load_reference_barrier_strong_native_rt_code_blob()->code_begin()));
722 } else {
723 __ far_call(RuntimeAddress(bs->load_reference_barrier_strong_rt_code_blob()->code_begin()));
724 }
725 } else if (is_weak) {
726 __ far_call(RuntimeAddress(bs->load_reference_barrier_weak_rt_code_blob()->code_begin()));
727 } else {
728 assert(is_phantom, "only remaining strength");
729 __ far_call(RuntimeAddress(bs->load_reference_barrier_phantom_rt_code_blob()->code_begin()));
730 }
731
732 __ b(*stub->continuation());
733 }
734
735 #undef __
736
737 #define __ sasm->
738
739 void ShenandoahBarrierSetAssembler::generate_c1_pre_barrier_runtime_stub(StubAssembler* sasm) {
740 __ prologue("shenandoah_pre_barrier", false);
741
742 // arg0 : previous value of memory
743
744 BarrierSet* bs = BarrierSet::barrier_set();
745
746 const Register pre_val = r0;
747 const Register thread = rthread;
748 const Register tmp = rscratch1;
749
750 Address queue_index(thread, in_bytes(ShenandoahThreadLocalData::satb_mark_queue_index_offset()));
751 Address buffer(thread, in_bytes(ShenandoahThreadLocalData::satb_mark_queue_buffer_offset()));
752
753 Label done;
754 Label runtime;
755
756 // Is marking still active?
757 Address gc_state(thread, in_bytes(ShenandoahThreadLocalData::gc_state_offset()));
758 __ ldrb(tmp, gc_state);
759 if (!ShenandoahHeap::heap()->mode()->is_generational()) {
760 __ tbz(tmp, ShenandoahHeap::YOUNG_MARKING_BITPOS, done);
761 } else {
762 __ mov(rscratch2, ShenandoahHeap::YOUNG_MARKING | ShenandoahHeap::OLD_MARKING);
763 __ tst(tmp, rscratch2);
764 __ br(Assembler::EQ, done);
765 }
766
767 // Can we store original value in the thread's buffer?
768 __ ldr(tmp, queue_index);
769 __ cbz(tmp, runtime);
770
771 __ sub(tmp, tmp, wordSize);
772 __ str(tmp, queue_index);
773 __ ldr(rscratch2, buffer);
774 __ add(tmp, tmp, rscratch2);
775 __ load_parameter(0, rscratch2);
776 __ str(rscratch2, Address(tmp, 0));
777 __ b(done);
778
779 __ bind(runtime);
780 __ push_call_clobbered_registers();
781 __ load_parameter(0, pre_val);
782 __ call_VM_leaf(CAST_FROM_FN_PTR(address, ShenandoahRuntime::write_ref_field_pre_entry), pre_val, thread);
783 __ pop_call_clobbered_registers();
784 __ bind(done);
785
786 __ epilogue();
787 }
788
789 void ShenandoahBarrierSetAssembler::generate_c1_load_reference_barrier_runtime_stub(StubAssembler* sasm, DecoratorSet decorators) {
790 __ prologue("shenandoah_load_reference_barrier", false);
791 // arg0 : object to be resolved
792
793 __ push_call_clobbered_registers();
794 __ load_parameter(0, r0);
795 __ load_parameter(1, r1);
796
797 bool is_strong = ShenandoahBarrierSet::is_strong_access(decorators);
798 bool is_weak = ShenandoahBarrierSet::is_weak_access(decorators);
799 bool is_phantom = ShenandoahBarrierSet::is_phantom_access(decorators);
800 bool is_native = ShenandoahBarrierSet::is_native_access(decorators);
801 if (is_strong) {
802 if (is_native) {
803 __ mov(lr, CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier_strong));
804 } else {
805 if (UseCompressedOops) {
806 __ mov(lr, CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier_strong_narrow));
807 } else {
808 __ mov(lr, CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier_strong));
809 }
810 }
811 } else if (is_weak) {
812 assert(!is_native, "weak must not be called off-heap");
813 if (UseCompressedOops) {
814 __ mov(lr, CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier_weak_narrow));
815 } else {
816 __ mov(lr, CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier_weak));
817 }
818 } else {
819 assert(is_phantom, "only remaining strength");
820 assert(is_native, "phantom must only be called off-heap");
821 __ mov(lr, CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier_phantom));
822 }
823 __ blr(lr);
824 __ mov(rscratch1, r0);
825 __ pop_call_clobbered_registers();
826 __ mov(r0, rscratch1);
827
828 __ epilogue();
829 }
830
831 #undef __
832
833 #endif // COMPILER1