1 /*
2  * Copyright (c) 1999, 2013, 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
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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_ValueStack.hpp"
30 #include "utilities/bitMap.inline.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 
ValueMap()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 
ValueMap(ValueMap * old)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 
increase_table_size()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 
find_insert(Value x)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 
kill_memory()196 void ValueMap::kill_memory() {
197   GENERIC_KILL_VALUE(MUST_KILL_MEMORY);
198 }
199 
kill_array(ValueType * type)200 void ValueMap::kill_array(ValueType* type) {
201   GENERIC_KILL_VALUE(MUST_KILL_ARRAY);
202 }
203 
kill_field(ciField * field,bool all_offsets)204 void ValueMap::kill_field(ciField* field, bool all_offsets) {
205   GENERIC_KILL_VALUE(MUST_KILL_FIELD);
206 }
207 
kill_map(ValueMap * map)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 
kill_all()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 
print()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 
reset_statistics()244 void ValueMap::reset_statistics() {
245   _number_of_finds = 0;
246   _number_of_hits = 0;
247   _number_of_kills = 0;
248 }
249 
print_statistics()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_ARRAY + 1];
269   bool                  _has_indexed_store[T_ARRAY + 1];
270 
271   // simplified access to methods of GlobalValueNumbering
current_map()272   ValueMap* current_map()                        { return _gvn->current_map(); }
value_map_of(BlockBegin * block)273   ValueMap* value_map_of(BlockBegin* block)      { return _gvn->value_map_of(block); }
274 
275   // implementation for abstract methods of ValueNumberingVisitor
kill_memory()276   void      kill_memory()                                 { _too_complicated_loop = true; }
kill_field(ciField * field,bool all_offsets)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_ARRAY, "Invalid type");
280     _has_field_store[field->type()->basic_type()] = true;
281   }
kill_array(ValueType * type)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_ARRAY, "Invalid type");
285     _has_indexed_store[basic_type] = true;
286   }
287 
288  public:
ShortLoopOptimizer(GlobalValueNumbering * gvn)289   ShortLoopOptimizer(GlobalValueNumbering* gvn)
290     : _gvn(gvn)
291     , _loop_blocks(ValueMapMaxLoopSize)
292     , _too_complicated_loop(false)
293   {
294     for (int i=0; i<= T_ARRAY; i++){
295       _has_field_store[i] = false;
296       _has_indexed_store[i] = false;
297     }
298   }
299 
has_field_store(BasicType type)300   bool has_field_store(BasicType type) {
301     assert(type >= 0 && type <= T_ARRAY, "Invalid type");
302     return _has_field_store[type];
303   }
304 
has_indexed_store(BasicType type)305   bool has_indexed_store(BasicType type) {
306     assert(type >= 0 && type <= T_ARRAY, "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 
set_invariant(Value v) const321   void set_invariant(Value v) const    { _gvn->set_processed(v); }
is_invariant(Value v) const322   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 
LoopInvariantCodeMotion(ShortLoopOptimizer * slo,GlobalValueNumbering * gvn,BlockBegin * loop_header,BlockList * loop_blocks)330 LoopInvariantCodeMotion::LoopInvariantCodeMotion(ShortLoopOptimizer *slo, GlobalValueNumbering* gvn, BlockBegin* loop_header, BlockList* loop_blocks)
331   : _gvn(gvn), _short_loop_optimizer(slo), _insertion_point(NULL), _state(NULL), _insert_is_pred(false) {
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 
process_block(BlockBegin * block)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 
process(BlockBegin * loop_header)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 
GlobalValueNumbering(IR * ir)487 GlobalValueNumbering::GlobalValueNumbering(IR* ir)
488   : _current_map(NULL)
489   , _value_maps(ir->linear_scan_order()->length(), NULL)
490   , _compilation(ir->compilation())
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 
substitute(Instruction * instr)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 }
593