1 /*
2 * Copyright (c) 1999, 2017, 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.inline.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, NULL)
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(), NULL)
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, NULL);
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 != NULL; 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(), NULL);
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 != NULL; 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() == NULL) {
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 = NULL; \
156 for (ValueMapEntry* entry = entry_at(i); entry != NULL; 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 == NULL) { \
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() != NULL || value->as_LoadIndexed() != NULL;
183
184 #define MUST_KILL_ARRAY(must_kill, entry, value) \
185 bool must_kill = value->as_LoadIndexed() != NULL \
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 != NULL \
192 && lf->field()->holder() == field->holder() \
193 && (all_offsets || lf->field()->offset() == field->offset());
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, NULL);
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) != NULL) {
230 tty->print(" %2d: ", i);
231 for (ValueMapEntry* entry = entry_at(i); entry != NULL; 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 >= 0 && 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 >= 0 && type < T_VOID, "Invalid type");
302 return _has_field_store[type];
303 }
304
305 bool has_indexed_store(BasicType type) {
306 assert(type >= 0 && 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 void set_invariant(Value v) const { _gvn->set_processed(v); }
322 bool is_invariant(Value v) const { return _gvn->is_processed(v); }
323
324 void process_block(BlockBegin* block);
325
326 public:
327 LoopInvariantCodeMotion(ShortLoopOptimizer *slo, GlobalValueNumbering* gvn, BlockBegin* loop_header, BlockList* loop_blocks);
328 };
329
330 LoopInvariantCodeMotion::LoopInvariantCodeMotion(ShortLoopOptimizer *slo, GlobalValueNumbering* gvn, BlockBegin* loop_header, BlockList* loop_blocks)
331 : _gvn(gvn), _short_loop_optimizer(slo) {
332
333 TRACE_VALUE_NUMBERING(tty->print_cr("using loop invariant code motion loop_header = %d", loop_header->block_id()));
334 TRACE_VALUE_NUMBERING(tty->print_cr("** loop invariant code motion for short loop B%d", loop_header->block_id()));
335
336 BlockBegin* insertion_block = loop_header->dominator();
337 if (insertion_block->number_of_preds() == 0) {
338 return; // only the entry block does not have a predecessor
339 }
340
341 assert(insertion_block->end()->as_Base() == NULL, "cannot insert into entry block");
342 _insertion_point = insertion_block->end()->prev();
343 _insert_is_pred = loop_header->is_predecessor(insertion_block);
344
345 BlockEnd *block_end = insertion_block->end();
346 _state = block_end->state_before();
347
348 if (!_state) {
349 // If, TableSwitch and LookupSwitch always have state_before when
350 // loop invariant code motion happens..
351 assert(block_end->as_Goto(), "Block has to be goto");
352 _state = block_end->state();
353 }
354
355 // the loop_blocks are filled by going backward from the loop header, so this processing order is best
356 assert(loop_blocks->at(0) == loop_header, "loop header must be first loop block");
357 process_block(loop_header);
358 for (int i = loop_blocks->length() - 1; i >= 1; i--) {
359 process_block(loop_blocks->at(i));
360 }
361 }
362
363 void LoopInvariantCodeMotion::process_block(BlockBegin* block) {
364 TRACE_VALUE_NUMBERING(tty->print_cr("processing block B%d", block->block_id()));
365
366 Instruction* prev = block;
367 Instruction* cur = block->next();
368
369 while (cur != NULL) {
370
371 // determine if cur instruction is loop invariant
372 // only selected instruction types are processed here
373 bool cur_invariant = false;
374
375 if (cur->as_Constant() != NULL) {
376 cur_invariant = !cur->can_trap();
377 } else if (cur->as_ArithmeticOp() != NULL || cur->as_LogicOp() != NULL || cur->as_ShiftOp() != NULL) {
378 assert(cur->as_Op2() != NULL, "must be Op2");
379 Op2* op2 = (Op2*)cur;
380 cur_invariant = !op2->can_trap() && is_invariant(op2->x()) && is_invariant(op2->y());
381 } else if (cur->as_LoadField() != NULL) {
382 LoadField* lf = (LoadField*)cur;
383 // deoptimizes on NullPointerException
384 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;
385 } else if (cur->as_ArrayLength() != NULL) {
386 ArrayLength *length = cur->as_ArrayLength();
387 cur_invariant = is_invariant(length->array());
388 } else if (cur->as_LoadIndexed() != NULL) {
389 LoadIndexed *li = (LoadIndexed *)cur->as_LoadIndexed();
390 cur_invariant = !_short_loop_optimizer->has_indexed_store(as_BasicType(cur->type())) && is_invariant(li->array()) && is_invariant(li->index()) && _insert_is_pred;
391 }
392
393 if (cur_invariant) {
394 // perform value numbering and mark instruction as loop-invariant
395 _gvn->substitute(cur);
396
397 if (cur->as_Constant() == NULL) {
398 // ensure that code for non-constant instructions is always generated
399 cur->pin();
400 }
401
402 // remove cur instruction from loop block and append it to block before loop
403 Instruction* next = cur->next();
404 Instruction* in = _insertion_point->next();
405 _insertion_point = _insertion_point->set_next(cur);
406 cur->set_next(in);
407
408 // Deoptimize on exception
409 cur->set_flag(Instruction::DeoptimizeOnException, true);
410
411 // Clear exception handlers
412 cur->set_exception_handlers(NULL);
413
414 TRACE_VALUE_NUMBERING(tty->print_cr("Instruction %c%d is loop invariant", cur->type()->tchar(), cur->id()));
415
416 if (cur->state_before() != NULL) {
417 cur->set_state_before(_state->copy());
418 }
419 if (cur->exception_state() != NULL) {
420 cur->set_exception_state(_state->copy());
421 }
422
423 cur = prev->set_next(next);
424
425 } else {
426 prev = cur;
427 cur = cur->next();
428 }
429 }
430 }
431
432 bool ShortLoopOptimizer::process(BlockBegin* loop_header) {
433 TRACE_VALUE_NUMBERING(tty->print_cr("** loop header block"));
434
435 _too_complicated_loop = false;
436 _loop_blocks.clear();
437 _loop_blocks.append(loop_header);
438
439 for (int i = 0; i < _loop_blocks.length(); i++) {
440 BlockBegin* block = _loop_blocks.at(i);
441 TRACE_VALUE_NUMBERING(tty->print_cr("processing loop block B%d", block->block_id()));
442
443 if (block->is_set(BlockBegin::exception_entry_flag)) {
444 // this would be too complicated
445 return false;
446 }
447
448 // add predecessors to worklist
449 for (int j = block->number_of_preds() - 1; j >= 0; j--) {
450 BlockBegin* pred = block->pred_at(j);
451
452 if (pred->is_set(BlockBegin::osr_entry_flag)) {
453 return false;
454 }
455
456 ValueMap* pred_map = value_map_of(pred);
457 if (pred_map != NULL) {
458 current_map()->kill_map(pred_map);
459 } else if (!_loop_blocks.contains(pred)) {
460 if (_loop_blocks.length() >= ValueMapMaxLoopSize) {
461 return false;
462 }
463 _loop_blocks.append(pred);
464 }
465 }
466
467 // use the instruction visitor for killing values
468 for (Value instr = block->next(); instr != NULL; instr = instr->next()) {
469 instr->visit(this);
470 if (_too_complicated_loop) {
471 return false;
472 }
473 }
474 }
475
476 bool optimistic = this->_gvn->compilation()->is_optimistic();
477
478 if (UseLoopInvariantCodeMotion && optimistic) {
479 LoopInvariantCodeMotion code_motion(this, _gvn, loop_header, &_loop_blocks);
480 }
481
482 TRACE_VALUE_NUMBERING(tty->print_cr("** loop successfully optimized"));
483 return true;
484 }
485
486
487 GlobalValueNumbering::GlobalValueNumbering(IR* ir)
488 : _compilation(ir->compilation())
489 , _current_map(NULL)
490 , _value_maps(ir->linear_scan_order()->length(), ir->linear_scan_order()->length(), NULL)
491 {
492 TRACE_VALUE_NUMBERING(tty->print_cr("****** start of global value numbering"));
493
494 ShortLoopOptimizer short_loop_optimizer(this);
495
496 BlockList* blocks = ir->linear_scan_order();
497 int num_blocks = blocks->length();
498
499 BlockBegin* start_block = blocks->at(0);
500 assert(start_block == ir->start() && start_block->number_of_preds() == 0 && start_block->dominator() == NULL, "must be start block");
501 assert(start_block->next()->as_Base() != NULL && start_block->next()->next() == NULL, "start block must not have instructions");
502
503 // method parameters are not linked in instructions list, so process them separateley
504 for_each_state_value(start_block->state(), value,
505 assert(value->as_Local() != NULL, "only method parameters allowed");
506 set_processed(value);
507 );
508
509 // initial, empty value map with nesting 0
510 set_value_map_of(start_block, new ValueMap());
511
512 for (int i = 1; i < num_blocks; i++) {
513 BlockBegin* block = blocks->at(i);
514 TRACE_VALUE_NUMBERING(tty->print_cr("**** processing block B%d", block->block_id()));
515
516 int num_preds = block->number_of_preds();
517 assert(num_preds > 0, "block must have predecessors");
518
519 BlockBegin* dominator = block->dominator();
520 assert(dominator != NULL, "dominator must exist");
521 assert(value_map_of(dominator) != NULL, "value map of dominator must exist");
522
523 // create new value map with increased nesting
524 _current_map = new ValueMap(value_map_of(dominator));
525
526 if (num_preds == 1 && !block->is_set(BlockBegin::exception_entry_flag)) {
527 assert(dominator == block->pred_at(0), "dominator must be equal to predecessor");
528 // nothing to do here
529
530 } else if (block->is_set(BlockBegin::linear_scan_loop_header_flag)) {
531 // block has incoming backward branches -> try to optimize short loops
532 if (!short_loop_optimizer.process(block)) {
533 // loop is too complicated, so kill all memory loads because there might be
534 // stores to them in the loop
535 current_map()->kill_memory();
536 }
537
538 } else {
539 // only incoming forward branches that are already processed
540 for (int j = 0; j < num_preds; j++) {
541 BlockBegin* pred = block->pred_at(j);
542 ValueMap* pred_map = value_map_of(pred);
543
544 if (pred_map != NULL) {
545 // propagate killed values of the predecessor to this block
546 current_map()->kill_map(value_map_of(pred));
547 } else {
548 // kill all memory loads because predecessor not yet processed
549 // (this can happen with non-natural loops and OSR-compiles)
550 current_map()->kill_memory();
551 }
552 }
553 }
554
555 // phi functions are not linked in instructions list, so process them separateley
556 for_each_phi_fun(block, phi,
557 set_processed(phi);
558 );
559
560 TRACE_VALUE_NUMBERING(tty->print("value map before processing block: "); current_map()->print());
561
562 // visit all instructions of this block
563 for (Value instr = block->next(); instr != NULL; instr = instr->next()) {
564 // check if instruction kills any values
565 instr->visit(this);
566 // perform actual value numbering
567 substitute(instr);
568 }
569
570 // remember value map for successors
571 set_value_map_of(block, current_map());
572 }
573
574 if (_has_substitutions) {
575 SubstitutionResolver resolver(ir);
576 }
577
578 TRACE_VALUE_NUMBERING(tty->print("****** end of global value numbering. "); ValueMap::print_statistics());
579 }
580
581 void GlobalValueNumbering::substitute(Instruction* instr) {
582 assert(!instr->has_subst(), "substitution already set");
583 Value subst = current_map()->find_insert(instr);
584 if (subst != instr) {
585 assert(!subst->has_subst(), "can't have a substitution");
586
587 TRACE_VALUE_NUMBERING(tty->print_cr("substitution for %d set to %d", instr->id(), subst->id()));
588 instr->set_subst(subst);
589 _has_substitutions = true;
590 }
591 set_processed(instr);
592 }