1 /*
2 * Copyright (c) 1999, 2005, 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 "incls/_precompiled.incl"
26 #include "incls/_c1_ValueMap.cpp.incl"
27
28
29 #ifndef PRODUCT
30
31 int ValueMap::_number_of_finds = 0;
32 int ValueMap::_number_of_hits = 0;
33 int ValueMap::_number_of_kills = 0;
34
35 #define TRACE_VALUE_NUMBERING(code) if (PrintValueNumbering) { code; }
36
37 #else
38
39 #define TRACE_VALUE_NUMBERING(code)
40
41 #endif
42
43
44 ValueMap::ValueMap()
45 : _nesting(0)
46 , _entries(ValueMapInitialSize, NULL)
47 , _killed_values()
48 , _entry_count(0)
49 {
50 NOT_PRODUCT(reset_statistics());
51 }
52
53
54 ValueMap::ValueMap(ValueMap* old)
55 : _nesting(old->_nesting + 1)
56 , _entries(old->_entries.length())
57 , _killed_values()
58 , _entry_count(old->_entry_count)
59 {
60 for (int i = size() - 1; i >= 0; i--) {
61 _entries.at_put(i, old->entry_at(i));
62 }
63 _killed_values.set_from(&old->_killed_values);
64 }
65
66
67 void ValueMap::increase_table_size() {
68 int old_size = size();
69 int new_size = old_size * 2 + 1;
70
71 ValueMapEntryList worklist(8);
72 ValueMapEntryArray new_entries(new_size, NULL);
73 int new_entry_count = 0;
74
75 TRACE_VALUE_NUMBERING(tty->print_cr("increasing table size from %d to %d", old_size, new_size));
76
77 for (int i = old_size - 1; i >= 0; i--) {
78 ValueMapEntry* entry;
79 for (entry = entry_at(i); entry != NULL; entry = entry->next()) {
80 if (!is_killed(entry->value())) {
81 worklist.push(entry);
82 }
83 }
84
85 while (!worklist.is_empty()) {
86 entry = worklist.pop();
87 int new_index = entry_index(entry->hash(), new_size);
88
89 if (entry->nesting() != nesting() && new_entries.at(new_index) != entry->next()) {
90 // changing entries with a lower nesting than the current nesting of the table
91 // is not allowed because then the same entry is contained in multiple value maps.
92 // clone entry when next-pointer must be changed
93 entry = new ValueMapEntry(entry->hash(), entry->value(), entry->nesting(), NULL);
94 }
95 entry->set_next(new_entries.at(new_index));
96 new_entries.at_put(new_index, entry);
97 new_entry_count++;
98 }
99 }
100
101 _entries = new_entries;
102 _entry_count = new_entry_count;
103 }
104
105
106 Value ValueMap::find_insert(Value x) {
107 const intx hash = x->hash();
108 if (hash != 0) {
109 // 0 hash means: exclude from value numbering
110 NOT_PRODUCT(_number_of_finds++);
111
112 for (ValueMapEntry* entry = entry_at(entry_index(hash, size())); entry != NULL; entry = entry->next()) {
113 if (entry->hash() == hash) {
114 Value f = entry->value();
115
116 if (!is_killed(f) && f->is_equal(x)) {
117 NOT_PRODUCT(_number_of_hits++);
118 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()));
119
120 if (entry->nesting() != nesting() && f->as_Constant() == NULL) {
121 // non-constant values of of another block must be pinned,
122 // otherwise it is possible that they are not evaluated
123 f->pin(Instruction::PinGlobalValueNumbering);
124 }
125
126 return f;
127
128 }
129 }
130 }
131
132 // x not found, so insert it
133 if (entry_count() >= size_threshold()) {
134 increase_table_size();
135 }
136 int idx = entry_index(hash, size());
137 _entries.at_put(idx, new ValueMapEntry(hash, x, nesting(), entry_at(idx)));
138 _entry_count++;
139
140 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()));
141 }
142
143 return x;
144 }
145
146
147 #define GENERIC_KILL_VALUE(must_kill_implementation) \
148 NOT_PRODUCT(_number_of_kills++); \
149 \
150 for (int i = size() - 1; i >= 0; i--) { \
151 ValueMapEntry* prev_entry = NULL; \
152 for (ValueMapEntry* entry = entry_at(i); entry != NULL; entry = entry->next()) { \
153 Value value = entry->value(); \
154 \
155 must_kill_implementation(must_kill, entry, value) \
156 \
157 if (must_kill) { \
158 kill_value(value); \
159 \
160 if (prev_entry == NULL) { \
161 _entries.at_put(i, entry->next()); \
162 _entry_count--; \
163 } else if (prev_entry->nesting() == nesting()) { \
164 prev_entry->set_next(entry->next()); \
165 _entry_count--; \
166 } else { \
167 prev_entry = entry; \
168 } \
169 \
170 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())); \
171 } else { \
172 prev_entry = entry; \
173 } \
174 } \
175 } \
176
177 #define MUST_KILL_MEMORY(must_kill, entry, value) \
178 bool must_kill = value->as_LoadField() != NULL || value->as_LoadIndexed() != NULL;
179
180 #define MUST_KILL_ARRAY(must_kill, entry, value) \
181 bool must_kill = value->as_LoadIndexed() != NULL \
182 && value->type()->tag() == type->tag();
183
184 #define MUST_KILL_FIELD(must_kill, entry, value) \
185 /* ciField's are not unique; must compare their contents */ \
186 LoadField* lf = value->as_LoadField(); \
187 bool must_kill = lf != NULL \
188 && lf->field()->holder() == field->holder() \
189 && lf->field()->offset() == field->offset();
190
191 #define MUST_KILL_EXCEPTION(must_kill, entry, value) \
192 assert(entry->nesting() < nesting(), "must not find bigger nesting than current"); \
193 bool must_kill = (entry->nesting() == nesting() - 1);
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) {
205 GENERIC_KILL_VALUE(MUST_KILL_FIELD);
206 }
207
208 void ValueMap::kill_exception() {
209 GENERIC_KILL_VALUE(MUST_KILL_EXCEPTION);
210 }
211
212
213 void ValueMap::kill_map(ValueMap* map) {
214 assert(is_global_value_numbering(), "only for global value numbering");
215 _killed_values.set_union(&map->_killed_values);
216 }
217
218 void ValueMap::kill_all() {
219 assert(is_local_value_numbering(), "only for local value numbering");
220 for (int i = size() - 1; i >= 0; i--) {
221 _entries.at_put(i, NULL);
222 }
223 _entry_count = 0;
224 }
225
226
227 #ifndef PRODUCT
228
229 void ValueMap::print() {
230 tty->print_cr("(size %d, entries %d, nesting %d)", size(), entry_count(), nesting());
231
232 int entries = 0;
233 for (int i = 0; i < size(); i++) {
234 if (entry_at(i) != NULL) {
235 tty->print(" %2d: ", i);
236 for (ValueMapEntry* entry = entry_at(i); entry != NULL; entry = entry->next()) {
237 Value value = entry->value();
238 tty->print("%s %c%d (%s%d) -> ", value->name(), value->type()->tchar(), value->id(), is_killed(value) ? "x" : "", entry->nesting());
239 entries++;
240 }
241 tty->print_cr("NULL");
242 }
243 }
244
245 _killed_values.print();
246 assert(entry_count() == entries, "entry_count incorrect");
247 }
248
249 void ValueMap::reset_statistics() {
250 _number_of_finds = 0;
251 _number_of_hits = 0;
252 _number_of_kills = 0;
253 }
254
255 void ValueMap::print_statistics() {
256 float hit_rate = 0;
257 if (_number_of_finds != 0) {
258 hit_rate = (float)_number_of_hits / _number_of_finds;
259 }
260
261 tty->print_cr("finds:%3d hits:%3d kills:%3d hit rate: %1.4f", _number_of_finds, _number_of_hits, _number_of_kills, hit_rate);
262 }
263
264 #endif
265
266
267
268 class ShortLoopOptimizer : public ValueNumberingVisitor {
269 private:
270 GlobalValueNumbering* _gvn;
271 BlockList _loop_blocks;
272 bool _too_complicated_loop;
273
274 // simplified access to methods of GlobalValueNumbering
275 ValueMap* current_map() { return _gvn->current_map(); }
276 ValueMap* value_map_of(BlockBegin* block) { return _gvn->value_map_of(block); }
277
278 // implementation for abstract methods of ValueNumberingVisitor
279 void kill_memory() { _too_complicated_loop = true; }
280 void kill_field(ciField* field) { current_map()->kill_field(field); };
281 void kill_array(ValueType* type) { current_map()->kill_array(type); };
282
283 public:
284 ShortLoopOptimizer(GlobalValueNumbering* gvn)
285 : _gvn(gvn)
286 , _loop_blocks(ValueMapMaxLoopSize)
287 , _too_complicated_loop(false)
288 {
289 }
290
291 bool process(BlockBegin* loop_header);
292 };
293
294
295 bool ShortLoopOptimizer::process(BlockBegin* loop_header) {
296 TRACE_VALUE_NUMBERING(tty->print_cr("** loop header block"));
297
298 _too_complicated_loop = false;
299 _loop_blocks.clear();
300 _loop_blocks.append(loop_header);
301
302 for (int i = 0; i < _loop_blocks.length(); i++) {
303 BlockBegin* block = _loop_blocks.at(i);
304 TRACE_VALUE_NUMBERING(tty->print_cr("processing loop block B%d", block->block_id()));
305
306 if (block->is_set(BlockBegin::exception_entry_flag)) {
307 // this would be too complicated
308 return false;
309 }
310
311 // add predecessors to worklist
312 for (int j = block->number_of_preds() - 1; j >= 0; j--) {
313 BlockBegin* pred = block->pred_at(j);
314
315 ValueMap* pred_map = value_map_of(pred);
316 if (pred_map != NULL) {
317 current_map()->kill_map(pred_map);
318 } else if (!_loop_blocks.contains(pred)) {
319 if (_loop_blocks.length() >= ValueMapMaxLoopSize) {
320 return false;
321 }
322 _loop_blocks.append(pred);
323 }
324 }
325
326 // use the instruction visitor for killing values
327 for (Value instr = block->next(); instr != NULL; instr = instr->next()) {
328 instr->visit(this);
329 if (_too_complicated_loop) {
330 return false;
331 }
332 }
333 }
334
335 TRACE_VALUE_NUMBERING(tty->print_cr("** loop successfully optimized"));
336 return true;
337 }
338
339
340 GlobalValueNumbering::GlobalValueNumbering(IR* ir)
341 : _current_map(NULL)
342 , _value_maps(ir->linear_scan_order()->length(), NULL)
343 {
344 TRACE_VALUE_NUMBERING(tty->print_cr("****** start of global value numbering"));
345
346 ShortLoopOptimizer short_loop_optimizer(this);
347 int subst_count = 0;
348
349 BlockList* blocks = ir->linear_scan_order();
350 int num_blocks = blocks->length();
351
352 BlockBegin* start_block = blocks->at(0);
353 assert(start_block == ir->start() && start_block->number_of_preds() == 0 && start_block->dominator() == NULL, "must be start block");
354 assert(start_block->next()->as_Base() != NULL && start_block->next()->next() == NULL, "start block must not have instructions");
355
356 // initial, empty value map with nesting 0
357 set_value_map_of(start_block, new ValueMap());
358
359 for (int i = 1; i < num_blocks; i++) {
360 BlockBegin* block = blocks->at(i);
361 TRACE_VALUE_NUMBERING(tty->print_cr("**** processing block B%d", block->block_id()));
362
363 int num_preds = block->number_of_preds();
364 assert(num_preds > 0, "block must have predecessors");
365
366 BlockBegin* dominator = block->dominator();
367 assert(dominator != NULL, "dominator must exist");
368 assert(value_map_of(dominator) != NULL, "value map of dominator must exist");
369
370 // create new value map with increased nesting
371 _current_map = new ValueMap(value_map_of(dominator));
372
373 if (num_preds == 1) {
374 assert(dominator == block->pred_at(0), "dominator must be equal to predecessor");
375 // nothing to do here
376
377 } else if (block->is_set(BlockBegin::linear_scan_loop_header_flag)) {
378 // block has incoming backward branches -> try to optimize short loops
379 if (!short_loop_optimizer.process(block)) {
380 // loop is too complicated, so kill all memory loads because there might be
381 // stores to them in the loop
382 current_map()->kill_memory();
383 }
384
385 } else {
386 // only incoming forward branches that are already processed
387 for (int j = 0; j < num_preds; j++) {
388 BlockBegin* pred = block->pred_at(j);
389 ValueMap* pred_map = value_map_of(pred);
390
391 if (pred_map != NULL) {
392 // propagate killed values of the predecessor to this block
393 current_map()->kill_map(value_map_of(pred));
394 } else {
395 // kill all memory loads because predecessor not yet processed
396 // (this can happen with non-natural loops and OSR-compiles)
397 current_map()->kill_memory();
398 }
399 }
400 }
401
402 if (block->is_set(BlockBegin::exception_entry_flag)) {
403 current_map()->kill_exception();
404 }
405
406 TRACE_VALUE_NUMBERING(tty->print("value map before processing block: "); current_map()->print());
407
408 // visit all instructions of this block
409 for (Value instr = block->next(); instr != NULL; instr = instr->next()) {
410 assert(!instr->has_subst(), "substitution already set");
411
412 // check if instruction kills any values
413 instr->visit(this);
414
415 if (instr->hash() != 0) {
416 Value f = current_map()->find_insert(instr);
417 if (f != instr) {
418 assert(!f->has_subst(), "can't have a substitution");
419 instr->set_subst(f);
420 subst_count++;
421 }
422 }
423 }
424
425 // remember value map for successors
426 set_value_map_of(block, current_map());
427 }
428
429 if (subst_count != 0) {
430 SubstitutionResolver resolver(ir);
431 }
432
433 TRACE_VALUE_NUMBERING(tty->print("****** end of global value numbering. "); ValueMap::print_statistics());
434 }