1 /*
2 * Copyright (c) 1999, 2010, 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 "utilities/bitMap.inline.hpp"
30
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, 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())
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, 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
129 return f;
130
131 }
132 }
133 }
134
135 // x not found, so insert it
136 if (entry_count() >= size_threshold()) {
137 increase_table_size();
138 }
139 int idx = entry_index(hash, size());
140 _entries.at_put(idx, new ValueMapEntry(hash, x, nesting(), entry_at(idx)));
141 _entry_count++;
142
143 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()));
144 }
145
146 return x;
147 }
148
149
150 #define GENERIC_KILL_VALUE(must_kill_implementation) \
151 NOT_PRODUCT(_number_of_kills++); \
152 \
153 for (int i = size() - 1; i >= 0; i--) { \
154 ValueMapEntry* prev_entry = NULL; \
155 for (ValueMapEntry* entry = entry_at(i); entry != NULL; entry = entry->next()) { \
156 Value value = entry->value(); \
157 \
158 must_kill_implementation(must_kill, entry, value) \
159 \
160 if (must_kill) { \
161 kill_value(value); \
162 \
163 if (prev_entry == NULL) { \
164 _entries.at_put(i, entry->next()); \
165 _entry_count--; \
166 } else if (prev_entry->nesting() == nesting()) { \
167 prev_entry->set_next(entry->next()); \
168 _entry_count--; \
169 } else { \
170 prev_entry = entry; \
171 } \
172 \
173 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())); \
174 } else { \
175 prev_entry = entry; \
176 } \
177 } \
178 } \
179
180 #define MUST_KILL_MEMORY(must_kill, entry, value) \
181 bool must_kill = value->as_LoadField() != NULL || value->as_LoadIndexed() != NULL;
182
183 #define MUST_KILL_ARRAY(must_kill, entry, value) \
184 bool must_kill = value->as_LoadIndexed() != NULL \
185 && value->type()->tag() == type->tag();
186
187 #define MUST_KILL_FIELD(must_kill, entry, value) \
188 /* ciField's are not unique; must compare their contents */ \
189 LoadField* lf = value->as_LoadField(); \
190 bool must_kill = lf != NULL \
191 && lf->field()->holder() == field->holder() \
192 && lf->field()->offset() == field->offset();
193
194 #define MUST_KILL_EXCEPTION(must_kill, entry, value) \
195 assert(entry->nesting() < nesting(), "must not find bigger nesting than current"); \
196 bool must_kill = (entry->nesting() == nesting() - 1);
197
198
199 void ValueMap::kill_memory() {
200 GENERIC_KILL_VALUE(MUST_KILL_MEMORY);
201 }
202
203 void ValueMap::kill_array(ValueType* type) {
204 GENERIC_KILL_VALUE(MUST_KILL_ARRAY);
205 }
206
207 void ValueMap::kill_field(ciField* field) {
208 GENERIC_KILL_VALUE(MUST_KILL_FIELD);
209 }
210
211 void ValueMap::kill_exception() {
212 GENERIC_KILL_VALUE(MUST_KILL_EXCEPTION);
213 }
214
215
216 void ValueMap::kill_map(ValueMap* map) {
217 assert(is_global_value_numbering(), "only for global value numbering");
218 _killed_values.set_union(&map->_killed_values);
219 }
220
221 void ValueMap::kill_all() {
222 assert(is_local_value_numbering(), "only for local value numbering");
223 for (int i = size() - 1; i >= 0; i--) {
224 _entries.at_put(i, NULL);
225 }
226 _entry_count = 0;
227 }
228
229
230 #ifndef PRODUCT
231
232 void ValueMap::print() {
233 tty->print_cr("(size %d, entries %d, nesting %d)", size(), entry_count(), nesting());
234
235 int entries = 0;
236 for (int i = 0; i < size(); i++) {
237 if (entry_at(i) != NULL) {
238 tty->print(" %2d: ", i);
239 for (ValueMapEntry* entry = entry_at(i); entry != NULL; entry = entry->next()) {
240 Value value = entry->value();
241 tty->print("%s %c%d (%s%d) -> ", value->name(), value->type()->tchar(), value->id(), is_killed(value) ? "x" : "", entry->nesting());
242 entries++;
243 }
244 tty->print_cr("NULL");
245 }
246 }
247
248 _killed_values.print();
249 assert(entry_count() == entries, "entry_count incorrect");
250 }
251
252 void ValueMap::reset_statistics() {
253 _number_of_finds = 0;
254 _number_of_hits = 0;
255 _number_of_kills = 0;
256 }
257
258 void ValueMap::print_statistics() {
259 float hit_rate = 0;
260 if (_number_of_finds != 0) {
261 hit_rate = (float)_number_of_hits / _number_of_finds;
262 }
263
264 tty->print_cr("finds:%3d hits:%3d kills:%3d hit rate: %1.4f", _number_of_finds, _number_of_hits, _number_of_kills, hit_rate);
265 }
266
267 #endif
268
269
270
271 class ShortLoopOptimizer : public ValueNumberingVisitor {
272 private:
273 GlobalValueNumbering* _gvn;
274 BlockList _loop_blocks;
275 bool _too_complicated_loop;
276
277 // simplified access to methods of GlobalValueNumbering
278 ValueMap* current_map() { return _gvn->current_map(); }
279 ValueMap* value_map_of(BlockBegin* block) { return _gvn->value_map_of(block); }
280
281 // implementation for abstract methods of ValueNumberingVisitor
282 void kill_memory() { _too_complicated_loop = true; }
283 void kill_field(ciField* field) { current_map()->kill_field(field); };
284 void kill_array(ValueType* type) { current_map()->kill_array(type); };
285
286 public:
287 ShortLoopOptimizer(GlobalValueNumbering* gvn)
288 : _gvn(gvn)
289 , _loop_blocks(ValueMapMaxLoopSize)
290 , _too_complicated_loop(false)
291 {
292 }
293
294 bool process(BlockBegin* loop_header);
295 };
296
297
298 bool ShortLoopOptimizer::process(BlockBegin* loop_header) {
299 TRACE_VALUE_NUMBERING(tty->print_cr("** loop header block"));
300
301 _too_complicated_loop = false;
302 _loop_blocks.clear();
303 _loop_blocks.append(loop_header);
304
305 for (int i = 0; i < _loop_blocks.length(); i++) {
306 BlockBegin* block = _loop_blocks.at(i);
307 TRACE_VALUE_NUMBERING(tty->print_cr("processing loop block B%d", block->block_id()));
308
309 if (block->is_set(BlockBegin::exception_entry_flag)) {
310 // this would be too complicated
311 return false;
312 }
313
314 // add predecessors to worklist
315 for (int j = block->number_of_preds() - 1; j >= 0; j--) {
316 BlockBegin* pred = block->pred_at(j);
317
318 ValueMap* pred_map = value_map_of(pred);
319 if (pred_map != NULL) {
320 current_map()->kill_map(pred_map);
321 } else if (!_loop_blocks.contains(pred)) {
322 if (_loop_blocks.length() >= ValueMapMaxLoopSize) {
323 return false;
324 }
325 _loop_blocks.append(pred);
326 }
327 }
328
329 // use the instruction visitor for killing values
330 for (Value instr = block->next(); instr != NULL; instr = instr->next()) {
331 instr->visit(this);
332 if (_too_complicated_loop) {
333 return false;
334 }
335 }
336 }
337
338 TRACE_VALUE_NUMBERING(tty->print_cr("** loop successfully optimized"));
339 return true;
340 }
341
342
343 GlobalValueNumbering::GlobalValueNumbering(IR* ir)
344 : _current_map(NULL)
345 , _value_maps(ir->linear_scan_order()->length(), NULL)
346 {
347 TRACE_VALUE_NUMBERING(tty->print_cr("****** start of global value numbering"));
348
349 ShortLoopOptimizer short_loop_optimizer(this);
350 int subst_count = 0;
351
352 BlockList* blocks = ir->linear_scan_order();
353 int num_blocks = blocks->length();
354
355 BlockBegin* start_block = blocks->at(0);
356 assert(start_block == ir->start() && start_block->number_of_preds() == 0 && start_block->dominator() == NULL, "must be start block");
357 assert(start_block->next()->as_Base() != NULL && start_block->next()->next() == NULL, "start block must not have instructions");
358
359 // initial, empty value map with nesting 0
360 set_value_map_of(start_block, new ValueMap());
361
362 for (int i = 1; i < num_blocks; i++) {
363 BlockBegin* block = blocks->at(i);
364 TRACE_VALUE_NUMBERING(tty->print_cr("**** processing block B%d", block->block_id()));
365
366 int num_preds = block->number_of_preds();
367 assert(num_preds > 0, "block must have predecessors");
368
369 BlockBegin* dominator = block->dominator();
370 assert(dominator != NULL, "dominator must exist");
371 assert(value_map_of(dominator) != NULL, "value map of dominator must exist");
372
373 // create new value map with increased nesting
374 _current_map = new ValueMap(value_map_of(dominator));
375
376 if (num_preds == 1) {
377 assert(dominator == block->pred_at(0), "dominator must be equal to predecessor");
378 // nothing to do here
379
380 } else if (block->is_set(BlockBegin::linear_scan_loop_header_flag)) {
381 // block has incoming backward branches -> try to optimize short loops
382 if (!short_loop_optimizer.process(block)) {
383 // loop is too complicated, so kill all memory loads because there might be
384 // stores to them in the loop
385 current_map()->kill_memory();
386 }
387
388 } else {
389 // only incoming forward branches that are already processed
390 for (int j = 0; j < num_preds; j++) {
391 BlockBegin* pred = block->pred_at(j);
392 ValueMap* pred_map = value_map_of(pred);
393
394 if (pred_map != NULL) {
395 // propagate killed values of the predecessor to this block
396 current_map()->kill_map(value_map_of(pred));
397 } else {
398 // kill all memory loads because predecessor not yet processed
399 // (this can happen with non-natural loops and OSR-compiles)
400 current_map()->kill_memory();
401 }
402 }
403 }
404
405 if (block->is_set(BlockBegin::exception_entry_flag)) {
406 current_map()->kill_exception();
407 }
408
409 TRACE_VALUE_NUMBERING(tty->print("value map before processing block: "); current_map()->print());
410
411 // visit all instructions of this block
412 for (Value instr = block->next(); instr != NULL; instr = instr->next()) {
413 assert(!instr->has_subst(), "substitution already set");
414
415 // check if instruction kills any values
416 instr->visit(this);
417
418 if (instr->hash() != 0) {
419 Value f = current_map()->find_insert(instr);
420 if (f != instr) {
421 assert(!f->has_subst(), "can't have a substitution");
422 instr->set_subst(f);
423 subst_count++;
424 }
425 }
426 }
427
428 // remember value map for successors
429 set_value_map_of(block, current_map());
430 }
431
432 if (subst_count != 0) {
433 SubstitutionResolver resolver(ir);
434 }
435
436 TRACE_VALUE_NUMBERING(tty->print("****** end of global value numbering. "); ValueMap::print_statistics());
437 }