1 /*
2 * Copyright (c) 1999, 2023, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "c1/c1_Canonicalizer.hpp"
27 #include "c1/c1_IR.hpp"
28 #include "c1/c1_ValueMap.hpp"
29 #include "c1/c1_ValueSet.hpp"
30 #include "c1/c1_ValueStack.hpp"
31
32 #ifndef PRODUCT
33
34 int ValueMap::_number_of_finds = 0;
35 int ValueMap::_number_of_hits = 0;
36 int ValueMap::_number_of_kills = 0;
37
38 #define TRACE_VALUE_NUMBERING(code) if (PrintValueNumbering) { code; }
39
40 #else
41
42 #define TRACE_VALUE_NUMBERING(code)
43
44 #endif
45
46
47 ValueMap::ValueMap()
48 : _nesting(0)
49 , _entries(ValueMapInitialSize, ValueMapInitialSize, nullptr)
50 , _killed_values()
51 , _entry_count(0)
52 {
53 NOT_PRODUCT(reset_statistics());
54 }
55
56
57 ValueMap::ValueMap(ValueMap* old)
58 : _nesting(old->_nesting + 1)
59 , _entries(old->_entries.length(), old->_entries.length(), nullptr)
60 , _killed_values()
61 , _entry_count(old->_entry_count)
62 {
63 for (int i = size() - 1; i >= 0; i--) {
64 _entries.at_put(i, old->entry_at(i));
65 }
66 _killed_values.set_from(&old->_killed_values);
67 }
68
69
70 void ValueMap::increase_table_size() {
71 int old_size = size();
72 int new_size = old_size * 2 + 1;
73
74 ValueMapEntryList worklist(8);
75 ValueMapEntryArray new_entries(new_size, new_size, nullptr);
76 int new_entry_count = 0;
77
78 TRACE_VALUE_NUMBERING(tty->print_cr("increasing table size from %d to %d", old_size, new_size));
79
80 for (int i = old_size - 1; i >= 0; i--) {
81 ValueMapEntry* entry;
82 for (entry = entry_at(i); entry != nullptr; entry = entry->next()) {
83 if (!is_killed(entry->value())) {
84 worklist.push(entry);
85 }
86 }
87
88 while (!worklist.is_empty()) {
89 entry = worklist.pop();
90 int new_index = entry_index(entry->hash(), new_size);
91
92 if (entry->nesting() != nesting() && new_entries.at(new_index) != entry->next()) {
93 // changing entries with a lower nesting than the current nesting of the table
94 // is not allowed because then the same entry is contained in multiple value maps.
95 // clone entry when next-pointer must be changed
96 entry = new ValueMapEntry(entry->hash(), entry->value(), entry->nesting(), nullptr);
97 }
98 entry->set_next(new_entries.at(new_index));
99 new_entries.at_put(new_index, entry);
100 new_entry_count++;
101 }
102 }
103
104 _entries = new_entries;
105 _entry_count = new_entry_count;
106 }
107
108
109 Value ValueMap::find_insert(Value x) {
110 const intx hash = x->hash();
111 if (hash != 0) {
112 // 0 hash means: exclude from value numbering
113 NOT_PRODUCT(_number_of_finds++);
114
115 for (ValueMapEntry* entry = entry_at(entry_index(hash, size())); entry != nullptr; entry = entry->next()) {
116 if (entry->hash() == hash) {
117 Value f = entry->value();
118
119 if (!is_killed(f) && f->is_equal(x)) {
120 NOT_PRODUCT(_number_of_hits++);
121 TRACE_VALUE_NUMBERING(tty->print_cr("Value Numbering: %s %c%d equal to %c%d (size %d, entries %d, nesting-diff %d)", x->name(), x->type()->tchar(), x->id(), f->type()->tchar(), f->id(), size(), entry_count(), nesting() - entry->nesting()));
122
123 if (entry->nesting() != nesting() && f->as_Constant() == nullptr) {
124 // non-constant values of of another block must be pinned,
125 // otherwise it is possible that they are not evaluated
126 f->pin(Instruction::PinGlobalValueNumbering);
127 }
128 assert(x->type()->tag() == f->type()->tag(), "should have same type");
129
130 return f;
131
132 }
133 }
134 }
135
136 // x not found, so insert it
137 if (entry_count() >= size_threshold()) {
138 increase_table_size();
139 }
140 int idx = entry_index(hash, size());
141 _entries.at_put(idx, new ValueMapEntry(hash, x, nesting(), entry_at(idx)));
142 _entry_count++;
143
144 TRACE_VALUE_NUMBERING(tty->print_cr("Value Numbering: insert %s %c%d (size %d, entries %d, nesting %d)", x->name(), x->type()->tchar(), x->id(), size(), entry_count(), nesting()));
145 }
146
147 return x;
148 }
149
150
151 #define GENERIC_KILL_VALUE(must_kill_implementation) \
152 NOT_PRODUCT(_number_of_kills++); \
153 \
154 for (int i = size() - 1; i >= 0; i--) { \
155 ValueMapEntry* prev_entry = nullptr; \
156 for (ValueMapEntry* entry = entry_at(i); entry != nullptr; entry = entry->next()) { \
157 Value value = entry->value(); \
158 \
159 must_kill_implementation(must_kill, entry, value) \
160 \
161 if (must_kill) { \
162 kill_value(value); \
163 \
164 if (prev_entry == nullptr) { \
165 _entries.at_put(i, entry->next()); \
166 _entry_count--; \
167 } else if (prev_entry->nesting() == nesting()) { \
168 prev_entry->set_next(entry->next()); \
169 _entry_count--; \
170 } else { \
171 prev_entry = entry; \
172 } \
173 \
174 TRACE_VALUE_NUMBERING(tty->print_cr("Value Numbering: killed %s %c%d (size %d, entries %d, nesting-diff %d)", value->name(), value->type()->tchar(), value->id(), size(), entry_count(), nesting() - entry->nesting())); \
175 } else { \
176 prev_entry = entry; \
177 } \
178 } \
179 } \
180
181 #define MUST_KILL_MEMORY(must_kill, entry, value) \
182 bool must_kill = value->as_LoadField() != nullptr || value->as_LoadIndexed() != nullptr;
183
184 #define MUST_KILL_ARRAY(must_kill, entry, value) \
185 bool must_kill = value->as_LoadIndexed() != nullptr \
186 && value->type()->tag() == type->tag();
187
188 #define MUST_KILL_FIELD(must_kill, entry, value) \
189 /* ciField's are not unique; must compare their contents */ \
190 LoadField* lf = value->as_LoadField(); \
191 bool must_kill = lf != nullptr \
192 && lf->field()->holder() == field->holder() \
193 && (all_offsets || lf->field()->offset_in_bytes() == field->offset_in_bytes());
194
195
196 void ValueMap::kill_memory() {
197 GENERIC_KILL_VALUE(MUST_KILL_MEMORY);
198 }
199
200 void ValueMap::kill_array(ValueType* type) {
201 GENERIC_KILL_VALUE(MUST_KILL_ARRAY);
202 }
203
204 void ValueMap::kill_field(ciField* field, bool all_offsets) {
205 GENERIC_KILL_VALUE(MUST_KILL_FIELD);
206 }
207
208 void ValueMap::kill_map(ValueMap* map) {
209 assert(is_global_value_numbering(), "only for global value numbering");
210 _killed_values.set_union(&map->_killed_values);
211 }
212
213 void ValueMap::kill_all() {
214 assert(is_local_value_numbering(), "only for local value numbering");
215 for (int i = size() - 1; i >= 0; i--) {
216 _entries.at_put(i, nullptr);
217 }
218 _entry_count = 0;
219 }
220
221
222 #ifndef PRODUCT
223
224 void ValueMap::print() {
225 tty->print_cr("(size %d, entries %d, nesting %d)", size(), entry_count(), nesting());
226
227 int entries = 0;
228 for (int i = 0; i < size(); i++) {
229 if (entry_at(i) != nullptr) {
230 tty->print(" %2d: ", i);
231 for (ValueMapEntry* entry = entry_at(i); entry != nullptr; entry = entry->next()) {
232 Value value = entry->value();
233 tty->print("%s %c%d (%s%d) -> ", value->name(), value->type()->tchar(), value->id(), is_killed(value) ? "x" : "", entry->nesting());
234 entries++;
235 }
236 tty->print_cr("null");
237 }
238 }
239
240 _killed_values.print();
241 assert(entry_count() == entries, "entry_count incorrect");
242 }
243
244 void ValueMap::reset_statistics() {
245 _number_of_finds = 0;
246 _number_of_hits = 0;
247 _number_of_kills = 0;
248 }
249
250 void ValueMap::print_statistics() {
251 float hit_rate = 0;
252 if (_number_of_finds != 0) {
253 hit_rate = (float)_number_of_hits / _number_of_finds;
254 }
255
256 tty->print_cr("finds:%3d hits:%3d kills:%3d hit rate: %1.4f", _number_of_finds, _number_of_hits, _number_of_kills, hit_rate);
257 }
258
259 #endif
260
261
262
263 class ShortLoopOptimizer : public ValueNumberingVisitor {
264 private:
265 GlobalValueNumbering* _gvn;
266 BlockList _loop_blocks;
267 bool _too_complicated_loop;
268 bool _has_field_store[T_VOID];
269 bool _has_indexed_store[T_VOID];
270
271 // simplified access to methods of GlobalValueNumbering
272 ValueMap* current_map() { return _gvn->current_map(); }
273 ValueMap* value_map_of(BlockBegin* block) { return _gvn->value_map_of(block); }
274
275 // implementation for abstract methods of ValueNumberingVisitor
276 void kill_memory() { _too_complicated_loop = true; }
277 void kill_field(ciField* field, bool all_offsets) {
278 current_map()->kill_field(field, all_offsets);
279 assert(field->type()->basic_type() >= 0 && field->type()->basic_type() < T_VOID, "Invalid type");
280 _has_field_store[field->type()->basic_type()] = true;
281 }
282 void kill_array(ValueType* type) {
283 current_map()->kill_array(type);
284 BasicType basic_type = as_BasicType(type); assert(basic_type < T_VOID, "Invalid type");
285 _has_indexed_store[basic_type] = true;
286 }
287
288 public:
289 ShortLoopOptimizer(GlobalValueNumbering* gvn)
290 : _gvn(gvn)
291 , _loop_blocks(ValueMapMaxLoopSize)
292 , _too_complicated_loop(false)
293 {
294 for (int i = 0; i < T_VOID; i++) {
295 _has_field_store[i] = false;
296 _has_indexed_store[i] = false;
297 }
298 }
299
300 bool has_field_store(BasicType type) {
301 assert(type < T_VOID, "Invalid type");
302 return _has_field_store[type];
303 }
304
305 bool has_indexed_store(BasicType type) {
306 assert(type < T_VOID, "Invalid type");
307 return _has_indexed_store[type];
308 }
309
310 bool process(BlockBegin* loop_header);
311 };
312
313 class LoopInvariantCodeMotion : public StackObj {
314 private:
315 GlobalValueNumbering* _gvn;
316 ShortLoopOptimizer* _short_loop_optimizer;
317 Instruction* _insertion_point;
318 ValueStack * _state;
319 bool _insert_is_pred;
320
321 bool is_invariant(Value v) const { return _gvn->is_processed(v); }
322
323 void process_block(BlockBegin* block);
324
325 public:
326 LoopInvariantCodeMotion(ShortLoopOptimizer *slo, GlobalValueNumbering* gvn, BlockBegin* loop_header, BlockList* loop_blocks);
327 };
328
329 LoopInvariantCodeMotion::LoopInvariantCodeMotion(ShortLoopOptimizer *slo, GlobalValueNumbering* gvn, BlockBegin* loop_header, BlockList* loop_blocks)
330 : _gvn(gvn), _short_loop_optimizer(slo), _insertion_point(nullptr), _state(nullptr), _insert_is_pred(false) {
331
332 TRACE_VALUE_NUMBERING(tty->print_cr("using loop invariant code motion loop_header = %d", loop_header->block_id()));
333 TRACE_VALUE_NUMBERING(tty->print_cr("** loop invariant code motion for short loop B%d", loop_header->block_id()));
334
335 BlockBegin* insertion_block = loop_header->dominator();
336 if (insertion_block->number_of_preds() == 0) {
337 return; // only the entry block does not have a predecessor
338 }
339
340 assert(insertion_block->end()->as_Base() == nullptr, "cannot insert into entry block");
341 _insertion_point = insertion_block->end()->prev();
342 _insert_is_pred = loop_header->is_predecessor(insertion_block);
343
344 BlockEnd *block_end = insertion_block->end();
345 _state = block_end->state_before();
346
347 if (!_state) {
348 // If, TableSwitch and LookupSwitch always have state_before when
349 // loop invariant code motion happens..
350 assert(block_end->as_Goto(), "Block has to be goto");
351 _state = block_end->state();
352 }
353
354 // the loop_blocks are filled by going backward from the loop header, so this processing order is best
355 assert(loop_blocks->at(0) == loop_header, "loop header must be first loop block");
356 process_block(loop_header);
357 for (int i = loop_blocks->length() - 1; i >= 1; i--) {
358 process_block(loop_blocks->at(i));
359 }
360 }
361
362 class CheckInsertionPoint : public ValueVisitor {
363 private:
364 Value _insert;
365 bool _valid = true;
366
367 void visit(Value* vp) {
368 assert(*vp != nullptr, "value should not be null");
369 if (_insert->dominator_depth() < (*vp)->dominator_depth()) {
370 _valid = false;
371 }
372 }
373
374 public:
375 bool is_valid() { return _valid; }
376 CheckInsertionPoint(Value insert)
377 : _insert(insert) {
378 assert(insert != nullptr, "insertion point should not be null");
379 }
380 };
381
382 // Check that insertion point has higher dom depth than all inputs to cur
383 static bool is_dominated_by_inputs(Instruction* insertion_point, Instruction* cur) {
384 CheckInsertionPoint v(insertion_point);
385 cur->input_values_do(&v);
386 return v.is_valid();
387 }
388
389 void LoopInvariantCodeMotion::process_block(BlockBegin* block) {
390 TRACE_VALUE_NUMBERING(tty->print_cr("processing block B%d", block->block_id()));
391
392 Instruction* prev = block;
393 Instruction* cur = block->next();
394
395 while (cur != nullptr) {
396 // determine if cur instruction is loop invariant
397 // only selected instruction types are processed here
398 bool cur_invariant = false;
399
400 if (cur->as_Constant() != nullptr) {
401 cur_invariant = !cur->can_trap();
402 } else if (cur->as_ArithmeticOp() != nullptr || cur->as_LogicOp() != nullptr || cur->as_ShiftOp() != nullptr) {
403 assert(cur->as_Op2() != nullptr, "must be Op2");
404 Op2* op2 = (Op2*)cur;
405 cur_invariant = !op2->can_trap() && is_invariant(op2->x()) && is_invariant(op2->y());
406 } else if (cur->as_LoadField() != nullptr) {
407 LoadField* lf = (LoadField*)cur;
408 // deoptimizes on NullPointerException
409 cur_invariant = !lf->needs_patching() && !lf->field()->is_volatile() && !_short_loop_optimizer->has_field_store(lf->field()->type()->basic_type()) && is_invariant(lf->obj()) && _insert_is_pred;
410 } else if (cur->as_ArrayLength() != nullptr) {
411 ArrayLength *length = cur->as_ArrayLength();
412 cur_invariant = is_invariant(length->array());
413 } else if (cur->as_LoadIndexed() != nullptr) {
414 LoadIndexed *li = (LoadIndexed *)cur->as_LoadIndexed();
415 cur_invariant = !_short_loop_optimizer->has_indexed_store(as_BasicType(cur->type())) && is_invariant(li->array()) && is_invariant(li->index()) && _insert_is_pred;
416 } else if (cur->as_NegateOp() != nullptr) {
417 NegateOp* neg = (NegateOp*)cur->as_NegateOp();
418 cur_invariant = is_invariant(neg->x());
419 } else if (cur->as_Convert() != nullptr) {
420 Convert* cvt = (Convert*)cur->as_Convert();
421 cur_invariant = is_invariant(cvt->value());
422 }
423
424 if (cur_invariant && is_dominated_by_inputs(_insertion_point, cur)) {
425 // perform value numbering and mark instruction as loop-invariant
426 _gvn->substitute(cur);
427
428 if (cur->as_Constant() == nullptr) {
429 // ensure that code for non-constant instructions is always generated
430 cur->pin();
431 }
432
433 // remove cur instruction from loop block and append it to block before loop
434 Instruction* next = cur->next();
435 Instruction* in = _insertion_point->next();
436 _insertion_point = _insertion_point->set_next(cur);
437 cur->set_next(in);
438
439 // Deoptimize on exception
440 cur->set_flag(Instruction::DeoptimizeOnException, true);
441
442 // Clear exception handlers
443 cur->set_exception_handlers(nullptr);
444
445 TRACE_VALUE_NUMBERING(tty->print_cr("Instruction %c%d is loop invariant", cur->type()->tchar(), cur->id()));
446 TRACE_VALUE_NUMBERING(cur->print_line());
447
448 if (cur->state_before() != nullptr) {
449 cur->set_state_before(_state->copy());
450 }
451 if (cur->exception_state() != nullptr) {
452 cur->set_exception_state(_state->copy());
453 }
454
455 cur = prev->set_next(next);
456 } else {
457 prev = cur;
458 cur = cur->next();
459 }
460 }
461 }
462
463 bool ShortLoopOptimizer::process(BlockBegin* loop_header) {
464 TRACE_VALUE_NUMBERING(tty->print_cr("** loop header block"));
465
466 _too_complicated_loop = false;
467 _loop_blocks.clear();
468 _loop_blocks.append(loop_header);
469
470 for (int i = 0; i < _loop_blocks.length(); i++) {
471 BlockBegin* block = _loop_blocks.at(i);
472 TRACE_VALUE_NUMBERING(tty->print_cr("processing loop block B%d", block->block_id()));
473
474 if (block->is_set(BlockBegin::exception_entry_flag)) {
475 // this would be too complicated
476 return false;
477 }
478
479 // add predecessors to worklist
480 for (int j = block->number_of_preds() - 1; j >= 0; j--) {
481 BlockBegin* pred = block->pred_at(j);
482
483 if (pred->is_set(BlockBegin::osr_entry_flag)) {
484 return false;
485 }
486
487 ValueMap* pred_map = value_map_of(pred);
488 if (pred_map != nullptr) {
489 current_map()->kill_map(pred_map);
490 } else if (!_loop_blocks.contains(pred)) {
491 if (_loop_blocks.length() >= ValueMapMaxLoopSize) {
492 return false;
493 }
494 _loop_blocks.append(pred);
495 }
496 }
497
498 // use the instruction visitor for killing values
499 for (Value instr = block->next(); instr != nullptr; instr = instr->next()) {
500 instr->visit(this);
501 if (_too_complicated_loop) {
502 return false;
503 }
504 }
505 }
506
507 bool optimistic = this->_gvn->compilation()->is_optimistic();
508
509 if (UseLoopInvariantCodeMotion && optimistic) {
510 LoopInvariantCodeMotion code_motion(this, _gvn, loop_header, &_loop_blocks);
511 }
512
513 TRACE_VALUE_NUMBERING(tty->print_cr("** loop successfully optimized"));
514 return true;
515 }
516
517
518 GlobalValueNumbering::GlobalValueNumbering(IR* ir)
519 : _compilation(ir->compilation())
520 , _current_map(nullptr)
521 , _value_maps(ir->linear_scan_order()->length(), ir->linear_scan_order()->length(), nullptr)
522 , _has_substitutions(false)
523 {
524 TRACE_VALUE_NUMBERING(tty->print_cr("****** start of global value numbering"));
525
526 ShortLoopOptimizer short_loop_optimizer(this);
527
528 BlockList* blocks = ir->linear_scan_order();
529 int num_blocks = blocks->length();
530
531 BlockBegin* start_block = blocks->at(0);
532 assert(start_block == ir->start() && start_block->number_of_preds() == 0 && start_block->dominator() == nullptr, "must be start block");
533 assert(start_block->next()->as_Base() != nullptr && start_block->next()->next() == nullptr, "start block must not have instructions");
534
535 // method parameters are not linked in instructions list, so process them separately
536 for_each_state_value(start_block->state(), value,
537 assert(value->as_Local() != nullptr, "only method parameters allowed");
538 set_processed(value);
539 );
540
541 // initial, empty value map with nesting 0
542 set_value_map_of(start_block, new ValueMap());
543
544 for (int i = 1; i < num_blocks; i++) {
545 BlockBegin* block = blocks->at(i);
546 TRACE_VALUE_NUMBERING(tty->print_cr("**** processing block B%d", block->block_id()));
547
548 int num_preds = block->number_of_preds();
549 assert(num_preds > 0, "block must have predecessors");
550
551 BlockBegin* dominator = block->dominator();
552 assert(dominator != nullptr, "dominator must exist");
553 assert(value_map_of(dominator) != nullptr, "value map of dominator must exist");
554
555 // create new value map with increased nesting
556 _current_map = new ValueMap(value_map_of(dominator));
557
558 if (num_preds == 1 && !block->is_set(BlockBegin::exception_entry_flag)) {
559 assert(dominator == block->pred_at(0), "dominator must be equal to predecessor");
560 // nothing to do here
561
562 } else if (block->is_set(BlockBegin::linear_scan_loop_header_flag)) {
563 // block has incoming backward branches -> try to optimize short loops
564 if (!short_loop_optimizer.process(block)) {
565 // loop is too complicated, so kill all memory loads because there might be
566 // stores to them in the loop
567 current_map()->kill_memory();
568 }
569
570 } else {
571 // only incoming forward branches that are already processed
572 for (int j = 0; j < num_preds; j++) {
573 BlockBegin* pred = block->pred_at(j);
574 ValueMap* pred_map = value_map_of(pred);
575
576 if (pred_map != nullptr) {
577 // propagate killed values of the predecessor to this block
578 current_map()->kill_map(value_map_of(pred));
579 } else {
580 // kill all memory loads because predecessor not yet processed
581 // (this can happen with non-natural loops and OSR-compiles)
582 current_map()->kill_memory();
583 }
584 }
585 }
586
587 // phi functions are not linked in instructions list, so process them separateley
588 for_each_phi_fun(block, phi,
589 set_processed(phi);
590 );
591
592 TRACE_VALUE_NUMBERING(tty->print("value map before processing block: "); current_map()->print());
593
594 // visit all instructions of this block
595 for (Value instr = block->next(); instr != nullptr; instr = instr->next()) {
596 // check if instruction kills any values
597 instr->visit(this);
598 // perform actual value numbering
599 substitute(instr);
600 }
601
602 // remember value map for successors
603 set_value_map_of(block, current_map());
604 }
605
606 if (_has_substitutions) {
607 SubstitutionResolver resolver(ir);
608 }
609
610 TRACE_VALUE_NUMBERING(tty->print("****** end of global value numbering. "); ValueMap::print_statistics());
611 }
612
613 void GlobalValueNumbering::substitute(Instruction* instr) {
614 assert(!instr->has_subst(), "substitution already set");
615 Value subst = current_map()->find_insert(instr);
616 if (subst != instr) {
617 assert(!subst->has_subst(), "can't have a substitution");
618
619 TRACE_VALUE_NUMBERING(tty->print_cr("substitution for %c%d set to %c%d", instr->type()->tchar(), instr->id(), subst->type()->tchar(), subst->id()));
620 instr->set_subst(subst);
621 _has_substitutions = true;
622 }
623 set_processed(instr);
624 }