1 /*
2 * Copyright (c) 2018, 2022, 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/javaThread.hpp"
38 #include "runtime/sharedRuntime.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, rscratch1, 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 tmp1,
105 Register tmp2,
106 bool tosca_live,
107 bool expand_call) {
108 // If expand_call is true then we expand the call_VM_leaf macro
109 // directly to skip generating the check by
110 // InterpreterMacroAssembler::call_VM_leaf_base that checks _last_sp.
111
112 assert(thread == rthread, "must be");
113
114 Label done;
115 Label runtime;
116
117 assert_different_registers(obj, pre_val, tmp1, tmp2);
118 assert(pre_val != noreg && tmp1 != noreg && tmp2 != noreg, "expecting a register");
119
120 Address in_progress(thread, in_bytes(ShenandoahThreadLocalData::satb_mark_queue_active_offset()));
121 Address index(thread, in_bytes(ShenandoahThreadLocalData::satb_mark_queue_index_offset()));
122 Address buffer(thread, in_bytes(ShenandoahThreadLocalData::satb_mark_queue_buffer_offset()));
123
124 // Is marking active?
125 if (in_bytes(SATBMarkQueue::byte_width_of_active()) == 4) {
126 __ ldrw(tmp1, in_progress);
127 } else {
128 assert(in_bytes(SATBMarkQueue::byte_width_of_active()) == 1, "Assumption");
129 __ ldrb(tmp1, in_progress);
130 }
131 __ cbzw(tmp1, done);
132
133 // Do we need to load the previous value?
134 if (obj != noreg) {
135 __ load_heap_oop(pre_val, Address(obj, 0), noreg, noreg, AS_RAW);
136 }
137
138 // Is the previous value null?
139 __ cbz(pre_val, done);
140
141 // Can we store original value in the thread's buffer?
142 // Is index == 0?
143 // (The index field is typed as size_t.)
144
145 __ ldr(tmp1, index); // tmp := *index_adr
146 __ cbz(tmp1, runtime); // tmp == 0?
147 // If yes, goto runtime
148
149 __ sub(tmp1, tmp1, wordSize); // tmp := tmp - wordSize
150 __ str(tmp1, index); // *index_adr := tmp
151 __ ldr(tmp2, buffer);
152 __ add(tmp1, tmp1, tmp2); // tmp := tmp + *buffer_adr
153
154 // Record the previous value
155 __ str(pre_val, Address(tmp1, 0));
156 __ b(done);
157
158 __ bind(runtime);
159 // save the live input values
160 RegSet saved = RegSet::of(pre_val);
161 if (tosca_live) saved += RegSet::of(r0);
162 if (obj != noreg) saved += RegSet::of(obj);
163
164 __ push(saved, sp);
165
166 // Calling the runtime using the regular call_VM_leaf mechanism generates
167 // code (generated by InterpreterMacroAssember::call_VM_leaf_base)
168 // that checks that the *(rfp+frame::interpreter_frame_last_sp) == NULL.
169 //
170 // If we care generating the pre-barrier without a frame (e.g. in the
171 // intrinsified Reference.get() routine) then rfp might be pointing to
172 // the caller frame and so this check will most likely fail at runtime.
173 //
174 // Expanding the call directly bypasses the generation of the check.
175 // So when we do not have have a full interpreter frame on the stack
176 // expand_call should be passed true.
177
178 if (expand_call) {
179 assert(pre_val != c_rarg1, "smashed arg");
180 __ super_call_VM_leaf(CAST_FROM_FN_PTR(address, ShenandoahRuntime::write_ref_field_pre_entry), pre_val, thread);
181 } else {
182 __ call_VM_leaf(CAST_FROM_FN_PTR(address, ShenandoahRuntime::write_ref_field_pre_entry), pre_val, thread);
183 }
184
185 __ pop(saved, sp);
186
187 __ bind(done);
188 }
189
190 void ShenandoahBarrierSetAssembler::resolve_forward_pointer(MacroAssembler* masm, Register dst, Register tmp) {
191 assert(ShenandoahLoadRefBarrier || ShenandoahCASBarrier, "Should be enabled");
192 Label is_null;
193 __ cbz(dst, is_null);
194 resolve_forward_pointer_not_null(masm, dst, tmp);
195 __ bind(is_null);
196 }
197
198 // IMPORTANT: This must preserve all registers, even rscratch1 and rscratch2, except those explicitly
199 // passed in.
200 void ShenandoahBarrierSetAssembler::resolve_forward_pointer_not_null(MacroAssembler* masm, Register dst, Register tmp) {
201 assert(ShenandoahLoadRefBarrier || ShenandoahCASBarrier, "Should be enabled");
202 // The below loads the mark word, checks if the lowest two bits are
203 // set, and if so, clear the lowest two bits and copy the result
204 // to dst. Otherwise it leaves dst alone.
205 // Implementing this is surprisingly awkward. I do it here by:
206 // - Inverting the mark word
207 // - Test lowest two bits == 0
208 // - If so, set the lowest two bits
209 // - Invert the result back, and copy to dst
210
211 bool borrow_reg = (tmp == noreg);
212 if (borrow_reg) {
213 // No free registers available. Make one useful.
214 tmp = rscratch1;
215 if (tmp == dst) {
216 tmp = rscratch2;
217 }
218 __ push(RegSet::of(tmp), sp);
219 }
220
221 assert_different_registers(tmp, dst);
222
223 Label done;
224 __ ldr(tmp, Address(dst, oopDesc::mark_offset_in_bytes()));
225 __ eon(tmp, tmp, zr);
226 __ ands(zr, tmp, markWord::lock_mask_in_place);
227 __ br(Assembler::NE, done);
228 __ orr(tmp, tmp, markWord::marked_value);
229 __ eon(dst, tmp, zr);
230 __ bind(done);
231
232 if (borrow_reg) {
233 __ pop(RegSet::of(tmp), sp);
234 }
235 }
236
237 void ShenandoahBarrierSetAssembler::load_reference_barrier(MacroAssembler* masm, Register dst, Address load_addr, DecoratorSet decorators) {
238 assert(ShenandoahLoadRefBarrier, "Should be enabled");
239 assert(dst != rscratch2, "need rscratch2");
240 assert_different_registers(load_addr.base(), load_addr.index(), rscratch1, rscratch2);
241
242 bool is_strong = ShenandoahBarrierSet::is_strong_access(decorators);
243 bool is_weak = ShenandoahBarrierSet::is_weak_access(decorators);
244 bool is_phantom = ShenandoahBarrierSet::is_phantom_access(decorators);
245 bool is_native = ShenandoahBarrierSet::is_native_access(decorators);
246 bool is_narrow = UseCompressedOops && !is_native;
247
248 Label heap_stable, not_cset;
249 __ enter(/*strip_ret_addr*/true);
250 Address gc_state(rthread, in_bytes(ShenandoahThreadLocalData::gc_state_offset()));
251 __ ldrb(rscratch2, gc_state);
252
253 // Check for heap stability
254 if (is_strong) {
255 __ tbz(rscratch2, ShenandoahHeap::HAS_FORWARDED_BITPOS, heap_stable);
256 } else {
257 Label lrb;
258 __ tbnz(rscratch2, ShenandoahHeap::WEAK_ROOTS_BITPOS, lrb);
259 __ tbz(rscratch2, ShenandoahHeap::HAS_FORWARDED_BITPOS, heap_stable);
260 __ bind(lrb);
261 }
262
263 // use r1 for load address
264 Register result_dst = dst;
265 if (dst == r1) {
266 __ mov(rscratch1, dst);
267 dst = rscratch1;
268 }
269
270 // Save r0 and r1, unless it is an output register
271 RegSet to_save = RegSet::of(r0, r1) - result_dst;
272 __ push(to_save, sp);
273 __ lea(r1, load_addr);
274 __ mov(r0, dst);
275
276 // Test for in-cset
277 if (is_strong) {
278 __ mov(rscratch2, ShenandoahHeap::in_cset_fast_test_addr());
279 __ lsr(rscratch1, r0, ShenandoahHeapRegion::region_size_bytes_shift_jint());
280 __ ldrb(rscratch2, Address(rscratch2, rscratch1));
281 __ tbz(rscratch2, 0, not_cset);
282 }
283
284 __ push_call_clobbered_registers();
285 if (is_strong) {
286 if (is_narrow) {
287 __ mov(lr, CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier_strong_narrow));
288 } else {
289 __ mov(lr, CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier_strong));
290 }
291 } else if (is_weak) {
292 if (is_narrow) {
293 __ mov(lr, CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier_weak_narrow));
294 } else {
295 __ mov(lr, CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier_weak));
296 }
297 } else {
298 assert(is_phantom, "only remaining strength");
299 assert(!is_narrow, "phantom access cannot be narrow");
300 __ mov(lr, CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier_phantom));
301 }
302 __ blr(lr);
303 __ mov(rscratch1, r0);
304 __ pop_call_clobbered_registers();
305 __ mov(r0, rscratch1);
306
307 __ bind(not_cset);
308
309 __ mov(result_dst, r0);
310 __ pop(to_save, sp);
311
312 __ bind(heap_stable);
313 __ leave();
314 }
315
316 void ShenandoahBarrierSetAssembler::iu_barrier(MacroAssembler* masm, Register dst, Register tmp) {
317 if (ShenandoahIUBarrier) {
318 __ push_call_clobbered_registers();
319 satb_write_barrier_pre(masm, noreg, dst, rthread, tmp, rscratch1, true, false);
320 __ pop_call_clobbered_registers();
321 }
322 }
323
324 //
325 // Arguments:
326 //
327 // Inputs:
328 // src: oop location to load from, might be clobbered
329 //
330 // Output:
331 // dst: oop loaded from src location
332 //
333 // Kill:
334 // rscratch1 (scratch reg)
335 //
336 // Alias:
337 // dst: rscratch1 (might use rscratch1 as temporary output register to avoid clobbering src)
338 //
339 void ShenandoahBarrierSetAssembler::load_at(MacroAssembler* masm, DecoratorSet decorators, BasicType type,
340 Register dst, Address src, Register tmp1, Register tmp2) {
341 // 1: non-reference load, no additional barrier is needed
342 if (!is_reference_type(type)) {
343 BarrierSetAssembler::load_at(masm, decorators, type, dst, src, tmp1, tmp2);
344 return;
345 }
346
347 // 2: load a reference from src location and apply LRB if needed
348 if (ShenandoahBarrierSet::need_load_reference_barrier(decorators, type)) {
349 Register result_dst = dst;
350
351 // Preserve src location for LRB
352 if (dst == src.base() || dst == src.index()) {
353 dst = rscratch1;
354 }
355 assert_different_registers(dst, src.base(), src.index());
356
357 BarrierSetAssembler::load_at(masm, decorators, type, dst, src, tmp1, tmp2);
358
359 load_reference_barrier(masm, dst, src, decorators);
360
361 if (dst != result_dst) {
362 __ mov(result_dst, dst);
363 dst = result_dst;
364 }
365 } else {
366 BarrierSetAssembler::load_at(masm, decorators, type, dst, src, tmp1, tmp2);
367 }
368
369 // 3: apply keep-alive barrier if needed
370 if (ShenandoahBarrierSet::need_keep_alive_barrier(decorators, type)) {
371 __ enter(/*strip_ret_addr*/true);
372 __ push_call_clobbered_registers();
373 satb_write_barrier_pre(masm /* masm */,
374 noreg /* obj */,
375 dst /* pre_val */,
376 rthread /* thread */,
377 tmp1 /* tmp1 */,
378 tmp2 /* tmp2 */,
379 true /* tosca_live */,
380 true /* expand_call */);
381 __ pop_call_clobbered_registers();
382 __ leave();
383 }
384 }
385
386 void ShenandoahBarrierSetAssembler::store_check(MacroAssembler* masm, Register obj) {
387 if (!ShenandoahHeap::heap()->mode()->is_generational()) {
388 return;
389 }
390
391 ShenandoahBarrierSet* ctbs = ShenandoahBarrierSet::barrier_set();
392 CardTable* ct = ctbs->card_table();
393
394 __ lsr(obj, obj, CardTable::card_shift());
395
396 assert(CardTable::dirty_card_val() == 0, "must be");
397
398 __ load_byte_map_base(rscratch1);
399
400 if (UseCondCardMark) {
401 Label L_already_dirty;
402 __ ldrb(rscratch2, Address(obj, rscratch1));
403 __ cbz(rscratch2, L_already_dirty);
404 __ strb(zr, Address(obj, rscratch1));
405 __ bind(L_already_dirty);
406 } else {
407 __ strb(zr, Address(obj, rscratch1));
408 }
409 }
410
411 void ShenandoahBarrierSetAssembler::store_at(MacroAssembler* masm, DecoratorSet decorators, BasicType type,
412 Address dst, Register val, Register tmp1, Register tmp2, Register tmp3) {
413 bool on_oop = is_reference_type(type);
414 if (!on_oop) {
415 BarrierSetAssembler::store_at(masm, decorators, type, dst, val, tmp1, tmp2, tmp3);
416 return;
417 }
418
419 // flatten object address if needed
420 if (dst.index() == noreg && dst.offset() == 0) {
421 if (dst.base() != tmp3) {
422 __ mov(tmp3, dst.base());
423 }
424 } else {
425 __ lea(tmp3, dst);
426 }
427
428 shenandoah_write_barrier_pre(masm,
429 tmp3 /* obj */,
430 tmp2 /* pre_val */,
431 rthread /* thread */,
432 tmp1 /* tmp */,
433 val != noreg /* tosca_live */,
434 false /* expand_call */);
435
436 if (val == noreg) {
437 BarrierSetAssembler::store_at(masm, decorators, type, Address(tmp3, 0), noreg, noreg, noreg, noreg);
438 } else {
439 iu_barrier(masm, val, tmp1);
440 // G1 barrier needs uncompressed oop for region cross check.
441 Register new_val = val;
442 if (UseCompressedOops) {
443 new_val = rscratch2;
444 __ mov(new_val, val);
445 }
446 BarrierSetAssembler::store_at(masm, decorators, type, Address(tmp3, 0), val, noreg, noreg, noreg);
447 store_check(masm, r3);
448 }
449
450 }
451
452 void ShenandoahBarrierSetAssembler::try_resolve_jobject_in_native(MacroAssembler* masm, Register jni_env,
453 Register obj, Register tmp, Label& slowpath) {
454 Label done;
455 // Resolve jobject
456 BarrierSetAssembler::try_resolve_jobject_in_native(masm, jni_env, obj, tmp, slowpath);
457
458 // Check for null.
459 __ cbz(obj, done);
460
461 assert(obj != rscratch2, "need rscratch2");
462 Address gc_state(jni_env, ShenandoahThreadLocalData::gc_state_offset() - JavaThread::jni_environment_offset());
463 __ lea(rscratch2, gc_state);
464 __ ldrb(rscratch2, Address(rscratch2));
465
466 // Check for heap in evacuation phase
467 __ tbnz(rscratch2, ShenandoahHeap::EVACUATION_BITPOS, slowpath);
468
469 __ bind(done);
470 }
471
472 // Special Shenandoah CAS implementation that handles false negatives due
473 // to concurrent evacuation. The service is more complex than a
474 // traditional CAS operation because the CAS operation is intended to
475 // succeed if the reference at addr exactly matches expected or if the
476 // reference at addr holds a pointer to a from-space object that has
477 // been relocated to the location named by expected. There are two
478 // races that must be addressed:
479 // a) A parallel thread may mutate the contents of addr so that it points
480 // to a different object. In this case, the CAS operation should fail.
481 // b) A parallel thread may heal the contents of addr, replacing a
482 // from-space pointer held in addr with the to-space pointer
483 // representing the new location of the object.
484 // Upon entry to cmpxchg_oop, it is assured that new_val equals NULL
485 // or it refers to an object that is not being evacuated out of
486 // from-space, or it refers to the to-space version of an object that
487 // is being evacuated out of from-space.
488 //
489 // By default the value held in the result register following execution
490 // of the generated code sequence is 0 to indicate failure of CAS,
491 // non-zero to indicate success. If is_cae, the result is the value most
492 // recently fetched from addr rather than a boolean success indicator.
493 //
494 // Clobbers rscratch1, rscratch2
495 void ShenandoahBarrierSetAssembler::cmpxchg_oop(MacroAssembler* masm,
496 Register addr,
497 Register expected,
498 Register new_val,
499 bool acquire, bool release,
500 bool is_cae,
501 Register result) {
502 Register tmp1 = rscratch1;
503 Register tmp2 = rscratch2;
504 bool is_narrow = UseCompressedOops;
505 Assembler::operand_size size = is_narrow ? Assembler::word : Assembler::xword;
506
507 assert_different_registers(addr, expected, tmp1, tmp2);
508 assert_different_registers(addr, new_val, tmp1, tmp2);
509
510 Label step4, done;
511
512 // There are two ways to reach this label. Initial entry into the
513 // cmpxchg_oop code expansion starts at step1 (which is equivalent
514 // to label step4). Additionally, in the rare case that four steps
515 // are required to perform the requested operation, the fourth step
516 // is the same as the first. On a second pass through step 1,
517 // control may flow through step 2 on its way to failure. It will
518 // not flow from step 2 to step 3 since we are assured that the
519 // memory at addr no longer holds a from-space pointer.
520 //
521 // The comments that immediately follow the step4 label apply only
522 // to the case in which control reaches this label by branch from
523 // step 3.
524
525 __ bind (step4);
526
527 // Step 4. CAS has failed because the value most recently fetched
528 // from addr is no longer the from-space pointer held in tmp2. If a
529 // different thread replaced the in-memory value with its equivalent
530 // to-space pointer, then CAS may still be able to succeed. The
531 // value held in the expected register has not changed.
532 //
533 // It is extremely rare we reach this point. For this reason, the
534 // implementation opts for smaller rather than potentially faster
535 // code. Ultimately, smaller code for this rare case most likely
536 // delivers higher overall throughput by enabling improved icache
537 // performance.
538
539 // Step 1. Fast-path.
540 //
541 // Try to CAS with given arguments. If successful, then we are done.
542 //
543 // No label required for step 1.
544
545 __ cmpxchg(addr, expected, new_val, size, acquire, release, false, tmp2);
546 // EQ flag set iff success. tmp2 holds value fetched.
547
548 // If expected equals null but tmp2 does not equal null, the
549 // following branches to done to report failure of CAS. If both
550 // expected and tmp2 equal null, the following branches to done to
551 // report success of CAS. There's no need for a special test of
552 // expected equal to null.
553
554 __ br(Assembler::EQ, done);
555 // if CAS failed, fall through to step 2
556
557 // Step 2. CAS has failed because the value held at addr does not
558 // match expected. This may be a false negative because the value fetched
559 // from addr (now held in tmp2) may be a from-space pointer to the
560 // original copy of same object referenced by to-space pointer expected.
561 //
562 // To resolve this, it suffices to find the forward pointer associated
563 // with fetched value. If this matches expected, retry CAS with new
564 // parameters. If this mismatches, then we have a legitimate
565 // failure, and we're done.
566 //
567 // No need for step2 label.
568
569 // overwrite tmp1 with from-space pointer fetched from memory
570 __ mov(tmp1, tmp2);
571
572 if (is_narrow) {
573 // Decode tmp1 in order to resolve its forward pointer
574 __ decode_heap_oop(tmp1, tmp1);
575 }
576 resolve_forward_pointer(masm, tmp1);
577 // Encode tmp1 to compare against expected.
578 __ encode_heap_oop(tmp1, tmp1);
579
580 // Does forwarded value of fetched from-space pointer match original
581 // value of expected? If tmp1 holds null, this comparison will fail
582 // because we know from step1 that expected is not null. There is
583 // no need for a separate test for tmp1 (the value originally held
584 // in memory) equal to null.
585 __ cmp(tmp1, expected);
586
587 // If not, then the failure was legitimate and we're done.
588 // Branching to done with NE condition denotes failure.
589 __ br(Assembler::NE, done);
590
591 // Fall through to step 3. No need for step3 label.
592
593 // Step 3. We've confirmed that the value originally held in memory
594 // (now held in tmp2) pointed to from-space version of original
595 // expected value. Try the CAS again with the from-space expected
596 // value. If it now succeeds, we're good.
597 //
598 // Note: tmp2 holds encoded from-space pointer that matches to-space
599 // object residing at expected. tmp2 is the new "expected".
600
601 // Note that macro implementation of __cmpxchg cannot use same register
602 // tmp2 for result and expected since it overwrites result before it
603 // compares result with expected.
604 __ cmpxchg(addr, tmp2, new_val, size, acquire, release, false, noreg);
605 // EQ flag set iff success. tmp2 holds value fetched, tmp1 (rscratch1) clobbered.
606
607 // If fetched value did not equal the new expected, this could
608 // still be a false negative because some other thread may have
609 // newly overwritten the memory value with its to-space equivalent.
610 __ br(Assembler::NE, step4);
611
612 if (is_cae) {
613 // We're falling through to done to indicate success. Success
614 // with is_cae is denoted by returning the value of expected as
615 // result.
616 __ mov(tmp2, expected);
617 }
618
619 __ bind(done);
620 // At entry to done, the Z (EQ) flag is on iff if the CAS
621 // operation was successful. Additionally, if is_cae, tmp2 holds
622 // the value most recently fetched from addr. In this case, success
623 // is denoted by tmp2 matching expected.
624
625 if (is_cae) {
626 __ mov(result, tmp2);
627 } else {
628 __ cset(result, Assembler::EQ);
629 }
630 }
631
632 void ShenandoahBarrierSetAssembler::gen_write_ref_array_post_barrier(MacroAssembler* masm, DecoratorSet decorators,
633 Register start, Register count, Register scratch, RegSet saved_regs) {
634 if (!ShenandoahHeap::heap()->mode()->is_generational()) {
635 return;
636 }
637
638 ShenandoahBarrierSet* bs = ShenandoahBarrierSet::barrier_set();
639 CardTable* ct = bs->card_table();
640
641 Label L_loop, L_done;
642 const Register end = count;
643
644 __ cbz(count, L_done); // zero count - nothing to do
645
646 __ lea(end, Address(start, count, Address::lsl(LogBytesPerHeapOop))); // end = start + count << LogBytesPerHeapOop
647 __ sub(end, end, BytesPerHeapOop); // last element address to make inclusive
648 __ lsr(start, start, CardTable::card_shift());
649 __ lsr(end, end, CardTable::card_shift());
650 __ sub(count, end, start); // number of bytes to copy
651
652 __ load_byte_map_base(scratch);
653 __ add(start, start, scratch);
654 __ bind(L_loop);
655 __ strb(zr, Address(start, count));
656 __ subs(count, count, 1);
657 __ br(Assembler::GE, L_loop);
658 __ bind(L_done);
659 }
660
661 #undef __
662
663 #ifdef COMPILER1
664
665 #define __ ce->masm()->
666
667 void ShenandoahBarrierSetAssembler::gen_pre_barrier_stub(LIR_Assembler* ce, ShenandoahPreBarrierStub* stub) {
668 ShenandoahBarrierSetC1* bs = (ShenandoahBarrierSetC1*)BarrierSet::barrier_set()->barrier_set_c1();
669 // At this point we know that marking is in progress.
670 // If do_load() is true then we have to emit the
671 // load of the previous value; otherwise it has already
672 // been loaded into _pre_val.
673
674 __ bind(*stub->entry());
675
676 assert(stub->pre_val()->is_register(), "Precondition.");
677
678 Register pre_val_reg = stub->pre_val()->as_register();
679
680 if (stub->do_load()) {
681 ce->mem2reg(stub->addr(), stub->pre_val(), T_OBJECT, stub->patch_code(), stub->info(), false /*wide*/);
682 }
683 __ cbz(pre_val_reg, *stub->continuation());
684 ce->store_parameter(stub->pre_val()->as_register(), 0);
685 __ far_call(RuntimeAddress(bs->pre_barrier_c1_runtime_code_blob()->code_begin()));
686 __ b(*stub->continuation());
687 }
688
689 void ShenandoahBarrierSetAssembler::gen_load_reference_barrier_stub(LIR_Assembler* ce, ShenandoahLoadReferenceBarrierStub* stub) {
690 ShenandoahBarrierSetC1* bs = (ShenandoahBarrierSetC1*)BarrierSet::barrier_set()->barrier_set_c1();
691 __ bind(*stub->entry());
692
693 DecoratorSet decorators = stub->decorators();
694 bool is_strong = ShenandoahBarrierSet::is_strong_access(decorators);
695 bool is_weak = ShenandoahBarrierSet::is_weak_access(decorators);
696 bool is_phantom = ShenandoahBarrierSet::is_phantom_access(decorators);
697 bool is_native = ShenandoahBarrierSet::is_native_access(decorators);
698
699 Register obj = stub->obj()->as_register();
700 Register res = stub->result()->as_register();
701 Register addr = stub->addr()->as_pointer_register();
702 Register tmp1 = stub->tmp1()->as_register();
703 Register tmp2 = stub->tmp2()->as_register();
704
705 assert(res == r0, "result must arrive in r0");
706
707 if (res != obj) {
708 __ mov(res, obj);
709 }
710
711 if (is_strong) {
712 // Check for object in cset.
713 __ mov(tmp2, ShenandoahHeap::in_cset_fast_test_addr());
714 __ lsr(tmp1, res, ShenandoahHeapRegion::region_size_bytes_shift_jint());
715 __ ldrb(tmp2, Address(tmp2, tmp1));
716 __ cbz(tmp2, *stub->continuation());
717 }
718
719 ce->store_parameter(res, 0);
720 ce->store_parameter(addr, 1);
721 if (is_strong) {
722 if (is_native) {
723 __ far_call(RuntimeAddress(bs->load_reference_barrier_strong_native_rt_code_blob()->code_begin()));
724 } else {
725 __ far_call(RuntimeAddress(bs->load_reference_barrier_strong_rt_code_blob()->code_begin()));
726 }
727 } else if (is_weak) {
728 __ far_call(RuntimeAddress(bs->load_reference_barrier_weak_rt_code_blob()->code_begin()));
729 } else {
730 assert(is_phantom, "only remaining strength");
731 __ far_call(RuntimeAddress(bs->load_reference_barrier_phantom_rt_code_blob()->code_begin()));
732 }
733
734 __ b(*stub->continuation());
735 }
736
737 #undef __
738
739 #define __ sasm->
740
741 void ShenandoahBarrierSetAssembler::generate_c1_pre_barrier_runtime_stub(StubAssembler* sasm) {
742 __ prologue("shenandoah_pre_barrier", false);
743
744 // arg0 : previous value of memory
745
746 BarrierSet* bs = BarrierSet::barrier_set();
747
748 const Register pre_val = r0;
749 const Register thread = rthread;
750 const Register tmp = rscratch1;
751
752 Address queue_index(thread, in_bytes(ShenandoahThreadLocalData::satb_mark_queue_index_offset()));
753 Address buffer(thread, in_bytes(ShenandoahThreadLocalData::satb_mark_queue_buffer_offset()));
754
755 Label done;
756 Label runtime;
757
758 // Is marking still active?
759 Address gc_state(thread, in_bytes(ShenandoahThreadLocalData::gc_state_offset()));
760 __ ldrb(tmp, gc_state);
761 if (!ShenandoahHeap::heap()->mode()->is_generational()) {
762 __ tbz(tmp, ShenandoahHeap::YOUNG_MARKING_BITPOS, done);
763 } else {
764 __ mov(rscratch2, ShenandoahHeap::YOUNG_MARKING | ShenandoahHeap::OLD_MARKING);
765 __ tst(tmp, rscratch2);
766 __ br(Assembler::EQ, done);
767 }
768
769 // Can we store original value in the thread's buffer?
770 __ ldr(tmp, queue_index);
771 __ cbz(tmp, runtime);
772
773 __ sub(tmp, tmp, wordSize);
774 __ str(tmp, queue_index);
775 __ ldr(rscratch2, buffer);
776 __ add(tmp, tmp, rscratch2);
777 __ load_parameter(0, rscratch2);
778 __ str(rscratch2, Address(tmp, 0));
779 __ b(done);
780
781 __ bind(runtime);
782 __ push_call_clobbered_registers();
783 __ load_parameter(0, pre_val);
784 __ call_VM_leaf(CAST_FROM_FN_PTR(address, ShenandoahRuntime::write_ref_field_pre_entry), pre_val, thread);
785 __ pop_call_clobbered_registers();
786 __ bind(done);
787
788 __ epilogue();
789 }
790
791 void ShenandoahBarrierSetAssembler::generate_c1_load_reference_barrier_runtime_stub(StubAssembler* sasm, DecoratorSet decorators) {
792 __ prologue("shenandoah_load_reference_barrier", false);
793 // arg0 : object to be resolved
794
795 __ push_call_clobbered_registers();
796 __ load_parameter(0, r0);
797 __ load_parameter(1, r1);
798
799 bool is_strong = ShenandoahBarrierSet::is_strong_access(decorators);
800 bool is_weak = ShenandoahBarrierSet::is_weak_access(decorators);
801 bool is_phantom = ShenandoahBarrierSet::is_phantom_access(decorators);
802 bool is_native = ShenandoahBarrierSet::is_native_access(decorators);
803 if (is_strong) {
804 if (is_native) {
805 __ mov(lr, CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier_strong));
806 } else {
807 if (UseCompressedOops) {
808 __ mov(lr, CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier_strong_narrow));
809 } else {
810 __ mov(lr, CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier_strong));
811 }
812 }
813 } else if (is_weak) {
814 assert(!is_native, "weak must not be called off-heap");
815 if (UseCompressedOops) {
816 __ mov(lr, CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier_weak_narrow));
817 } else {
818 __ mov(lr, CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier_weak));
819 }
820 } else {
821 assert(is_phantom, "only remaining strength");
822 assert(is_native, "phantom must only be called off-heap");
823 __ mov(lr, CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier_phantom));
824 }
825 __ blr(lr);
826 __ mov(rscratch1, r0);
827 __ pop_call_clobbered_registers();
828 __ mov(r0, rscratch1);
829
830 __ epilogue();
831 }
832
833 #undef __
834
835 #endif // COMPILER1