1 /*
  2  * Copyright (c) 1999, 2020, 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, 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   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(NULL), _state(NULL), _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() == NULL, "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 void LoopInvariantCodeMotion::process_block(BlockBegin* block) {
363   TRACE_VALUE_NUMBERING(tty->print_cr("processing block B%d", block->block_id()));
364 
365   Instruction* prev = block;
366   Instruction* cur = block->next();
367 
368   while (cur != NULL) {
369     // determine if cur instruction is loop invariant
370     // only selected instruction types are processed here
371     bool cur_invariant = false;
372 
373     if (cur->as_Constant() != NULL) {
374       cur_invariant = !cur->can_trap();
375     } else if (cur->as_ArithmeticOp() != NULL || cur->as_LogicOp() != NULL || cur->as_ShiftOp() != NULL) {
376       assert(cur->as_Op2() != NULL, "must be Op2");
377       Op2* op2 = (Op2*)cur;
378       cur_invariant = !op2->can_trap() && is_invariant(op2->x()) && is_invariant(op2->y());
379     } else if (cur->as_LoadField() != NULL) {
380       LoadField* lf = (LoadField*)cur;
381       // deoptimizes on NullPointerException
382       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;
383     } else if (cur->as_ArrayLength() != NULL) {
384       ArrayLength *length = cur->as_ArrayLength();
385       cur_invariant = is_invariant(length->array());
386     } else if (cur->as_LoadIndexed() != NULL) {
387       LoadIndexed *li = (LoadIndexed *)cur->as_LoadIndexed();
388       cur_invariant = !_short_loop_optimizer->has_indexed_store(as_BasicType(cur->type())) && is_invariant(li->array()) && is_invariant(li->index()) && _insert_is_pred;
389     } else if (cur->as_NegateOp() != NULL) {
390       NegateOp* neg = (NegateOp*)cur->as_NegateOp();
391       cur_invariant = is_invariant(neg->x());
392     } else if (cur->as_Convert() != NULL) {
393       Convert* cvt = (Convert*)cur->as_Convert();
394       cur_invariant = is_invariant(cvt->value());
395     }
396 
397     if (cur_invariant) {
398       // perform value numbering and mark instruction as loop-invariant
399       _gvn->substitute(cur);
400 
401       if (cur->as_Constant() == NULL) {
402         // ensure that code for non-constant instructions is always generated
403         cur->pin();
404       }
405 
406       // remove cur instruction from loop block and append it to block before loop
407       Instruction* next = cur->next();
408       Instruction* in = _insertion_point->next();
409       _insertion_point = _insertion_point->set_next(cur);
410       cur->set_next(in);
411 
412       //  Deoptimize on exception
413       cur->set_flag(Instruction::DeoptimizeOnException, true);
414 
415       //  Clear exception handlers
416       cur->set_exception_handlers(NULL);
417 
418       TRACE_VALUE_NUMBERING(tty->print_cr("Instruction %c%d is loop invariant", cur->type()->tchar(), cur->id()));
419       TRACE_VALUE_NUMBERING(cur->print_line());
420 
421       if (cur->state_before() != NULL) {
422         cur->set_state_before(_state->copy());
423       }
424       if (cur->exception_state() != NULL) {
425         cur->set_exception_state(_state->copy());
426       }
427 
428       cur = prev->set_next(next);
429     } else {
430       prev = cur;
431       cur = cur->next();
432     }
433   }
434 }
435 
436 bool ShortLoopOptimizer::process(BlockBegin* loop_header) {
437   TRACE_VALUE_NUMBERING(tty->print_cr("** loop header block"));
438 
439   _too_complicated_loop = false;
440   _loop_blocks.clear();
441   _loop_blocks.append(loop_header);
442 
443   for (int i = 0; i < _loop_blocks.length(); i++) {
444     BlockBegin* block = _loop_blocks.at(i);
445     TRACE_VALUE_NUMBERING(tty->print_cr("processing loop block B%d", block->block_id()));
446 
447     if (block->is_set(BlockBegin::exception_entry_flag)) {
448       // this would be too complicated
449       return false;
450     }
451 
452     // add predecessors to worklist
453     for (int j = block->number_of_preds() - 1; j >= 0; j--) {
454       BlockBegin* pred = block->pred_at(j);
455 
456       if (pred->is_set(BlockBegin::osr_entry_flag)) {
457         return false;
458       }
459 
460       ValueMap* pred_map = value_map_of(pred);
461       if (pred_map != NULL) {
462         current_map()->kill_map(pred_map);
463       } else if (!_loop_blocks.contains(pred)) {
464         if (_loop_blocks.length() >= ValueMapMaxLoopSize) {
465           return false;
466         }
467         _loop_blocks.append(pred);
468       }
469     }
470 
471     // use the instruction visitor for killing values
472     for (Value instr = block->next(); instr != NULL; instr = instr->next()) {
473       instr->visit(this);
474       if (_too_complicated_loop) {
475         return false;
476       }
477     }
478   }
479 
480   bool optimistic = this->_gvn->compilation()->is_optimistic();
481 
482   if (UseLoopInvariantCodeMotion && optimistic) {
483     LoopInvariantCodeMotion code_motion(this, _gvn, loop_header, &_loop_blocks);
484   }
485 
486   TRACE_VALUE_NUMBERING(tty->print_cr("** loop successfully optimized"));
487   return true;
488 }
489 
490 
491 GlobalValueNumbering::GlobalValueNumbering(IR* ir)
492   : _compilation(ir->compilation())
493   , _current_map(NULL)
494   , _value_maps(ir->linear_scan_order()->length(), ir->linear_scan_order()->length(), NULL)
495   , _has_substitutions(false)
496 {
497   TRACE_VALUE_NUMBERING(tty->print_cr("****** start of global value numbering"));
498 
499   ShortLoopOptimizer short_loop_optimizer(this);
500 
501   BlockList* blocks = ir->linear_scan_order();
502   int num_blocks = blocks->length();
503 
504   BlockBegin* start_block = blocks->at(0);
505   assert(start_block == ir->start() && start_block->number_of_preds() == 0 && start_block->dominator() == NULL, "must be start block");
506   assert(start_block->next()->as_Base() != NULL && start_block->next()->next() == NULL, "start block must not have instructions");
507 
508   // method parameters are not linked in instructions list, so process them separateley
509   for_each_state_value(start_block->state(), value,
510      assert(value->as_Local() != NULL, "only method parameters allowed");
511      set_processed(value);
512   );
513 
514   // initial, empty value map with nesting 0
515   set_value_map_of(start_block, new ValueMap());
516 
517   for (int i = 1; i < num_blocks; i++) {
518     BlockBegin* block = blocks->at(i);
519     TRACE_VALUE_NUMBERING(tty->print_cr("**** processing block B%d", block->block_id()));
520 
521     int num_preds = block->number_of_preds();
522     assert(num_preds > 0, "block must have predecessors");
523 
524     BlockBegin* dominator = block->dominator();
525     assert(dominator != NULL, "dominator must exist");
526     assert(value_map_of(dominator) != NULL, "value map of dominator must exist");
527 
528     // create new value map with increased nesting
529     _current_map = new ValueMap(value_map_of(dominator));
530 
531     if (num_preds == 1 && !block->is_set(BlockBegin::exception_entry_flag)) {
532       assert(dominator == block->pred_at(0), "dominator must be equal to predecessor");
533       // nothing to do here
534 
535     } else if (block->is_set(BlockBegin::linear_scan_loop_header_flag)) {
536       // block has incoming backward branches -> try to optimize short loops
537       if (!short_loop_optimizer.process(block)) {
538         // loop is too complicated, so kill all memory loads because there might be
539         // stores to them in the loop
540         current_map()->kill_memory();
541       }
542 
543     } else {
544       // only incoming forward branches that are already processed
545       for (int j = 0; j < num_preds; j++) {
546         BlockBegin* pred = block->pred_at(j);
547         ValueMap* pred_map = value_map_of(pred);
548 
549         if (pred_map != NULL) {
550           // propagate killed values of the predecessor to this block
551           current_map()->kill_map(value_map_of(pred));
552         } else {
553           // kill all memory loads because predecessor not yet processed
554           // (this can happen with non-natural loops and OSR-compiles)
555           current_map()->kill_memory();
556         }
557       }
558     }
559 
560     // phi functions are not linked in instructions list, so process them separateley
561     for_each_phi_fun(block, phi,
562       set_processed(phi);
563     );
564 
565     TRACE_VALUE_NUMBERING(tty->print("value map before processing block: "); current_map()->print());
566 
567     // visit all instructions of this block
568     for (Value instr = block->next(); instr != NULL; instr = instr->next()) {
569       // check if instruction kills any values
570       instr->visit(this);
571       // perform actual value numbering
572       substitute(instr);
573     }
574 
575     // remember value map for successors
576     set_value_map_of(block, current_map());
577   }
578 
579   if (_has_substitutions) {
580     SubstitutionResolver resolver(ir);
581   }
582 
583   TRACE_VALUE_NUMBERING(tty->print("****** end of global value numbering. "); ValueMap::print_statistics());
584 }
585 
586 void GlobalValueNumbering::substitute(Instruction* instr) {
587   assert(!instr->has_subst(), "substitution already set");
588   Value subst = current_map()->find_insert(instr);
589   if (subst != instr) {


590     assert(!subst->has_subst(), "can't have a substitution");
591 
592     TRACE_VALUE_NUMBERING(tty->print_cr("substitution for %c%d set to %c%d", instr->type()->tchar(), instr->id(), subst->type()->tchar(), subst->id()));
593     instr->set_subst(subst);
594     _has_substitutions = true;
595   }
596   set_processed(instr);
597 }
--- EOF ---