aoqi@0: /*
aoqi@0:  * Copyright (c) 1999, 2013, Oracle and/or its affiliates. All rights reserved.
aoqi@0:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
aoqi@0:  *
aoqi@0:  * This code is free software; you can redistribute it and/or modify it
aoqi@0:  * under the terms of the GNU General Public License version 2 only, as
aoqi@0:  * published by the Free Software Foundation.
aoqi@0:  *
aoqi@0:  * This code is distributed in the hope that it will be useful, but WITHOUT
aoqi@0:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
aoqi@0:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
aoqi@0:  * version 2 for more details (a copy is included in the LICENSE file that
aoqi@0:  * accompanied this code).
aoqi@0:  *
aoqi@0:  * You should have received a copy of the GNU General Public License version
aoqi@0:  * 2 along with this work; if not, write to the Free Software Foundation,
aoqi@0:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
aoqi@0:  *
aoqi@0:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
aoqi@0:  * or visit www.oracle.com if you need additional information or have any
aoqi@0:  * questions.
aoqi@0:  *
aoqi@0:  */
aoqi@0: 
aoqi@0: #include "precompiled.hpp"
aoqi@0: #include "c1/c1_Canonicalizer.hpp"
aoqi@0: #include "c1/c1_IR.hpp"
aoqi@0: #include "c1/c1_ValueMap.hpp"
aoqi@0: #include "c1/c1_ValueStack.hpp"
aoqi@0: #include "utilities/bitMap.inline.hpp"
aoqi@0: 
aoqi@0: #ifndef PRODUCT
aoqi@0: 
aoqi@0:   int ValueMap::_number_of_finds = 0;
aoqi@0:   int ValueMap::_number_of_hits = 0;
aoqi@0:   int ValueMap::_number_of_kills = 0;
aoqi@0: 
aoqi@0:   #define TRACE_VALUE_NUMBERING(code) if (PrintValueNumbering) { code; }
aoqi@0: 
aoqi@0: #else
aoqi@0: 
aoqi@0:   #define TRACE_VALUE_NUMBERING(code)
aoqi@0: 
aoqi@0: #endif
aoqi@0: 
aoqi@0: 
aoqi@0: ValueMap::ValueMap()
aoqi@0:   : _nesting(0)
aoqi@0:   , _entries(ValueMapInitialSize, NULL)
aoqi@0:   , _killed_values()
aoqi@0:   , _entry_count(0)
aoqi@0: {
aoqi@0:   NOT_PRODUCT(reset_statistics());
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: ValueMap::ValueMap(ValueMap* old)
aoqi@0:   : _nesting(old->_nesting + 1)
aoqi@0:   , _entries(old->_entries.length())
aoqi@0:   , _killed_values()
aoqi@0:   , _entry_count(old->_entry_count)
aoqi@0: {
aoqi@0:   for (int i = size() - 1; i >= 0; i--) {
aoqi@0:     _entries.at_put(i, old->entry_at(i));
aoqi@0:   }
aoqi@0:   _killed_values.set_from(&old->_killed_values);
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: void ValueMap::increase_table_size() {
aoqi@0:   int old_size = size();
aoqi@0:   int new_size = old_size * 2 + 1;
aoqi@0: 
aoqi@0:   ValueMapEntryList worklist(8);
aoqi@0:   ValueMapEntryArray new_entries(new_size, NULL);
aoqi@0:   int new_entry_count = 0;
aoqi@0: 
aoqi@0:   TRACE_VALUE_NUMBERING(tty->print_cr("increasing table size from %d to %d", old_size, new_size));
aoqi@0: 
aoqi@0:   for (int i = old_size - 1; i >= 0; i--) {
aoqi@0:     ValueMapEntry* entry;
aoqi@0:     for (entry = entry_at(i); entry != NULL; entry = entry->next()) {
aoqi@0:       if (!is_killed(entry->value())) {
aoqi@0:         worklist.push(entry);
aoqi@0:       }
aoqi@0:     }
aoqi@0: 
aoqi@0:     while (!worklist.is_empty()) {
aoqi@0:       entry = worklist.pop();
aoqi@0:       int new_index = entry_index(entry->hash(), new_size);
aoqi@0: 
aoqi@0:       if (entry->nesting() != nesting() && new_entries.at(new_index) != entry->next()) {
aoqi@0:         // changing entries with a lower nesting than the current nesting of the table
aoqi@0:         // is not allowed because then the same entry is contained in multiple value maps.
aoqi@0:         // clone entry when next-pointer must be changed
aoqi@0:         entry = new ValueMapEntry(entry->hash(), entry->value(), entry->nesting(), NULL);
aoqi@0:       }
aoqi@0:       entry->set_next(new_entries.at(new_index));
aoqi@0:       new_entries.at_put(new_index, entry);
aoqi@0:       new_entry_count++;
aoqi@0:     }
aoqi@0:   }
aoqi@0: 
aoqi@0:   _entries = new_entries;
aoqi@0:   _entry_count = new_entry_count;
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: Value ValueMap::find_insert(Value x) {
aoqi@0:   const intx hash = x->hash();
aoqi@0:   if (hash != 0) {
aoqi@0:     // 0 hash means: exclude from value numbering
aoqi@0:     NOT_PRODUCT(_number_of_finds++);
aoqi@0: 
aoqi@0:     for (ValueMapEntry* entry = entry_at(entry_index(hash, size())); entry != NULL; entry = entry->next()) {
aoqi@0:       if (entry->hash() == hash) {
aoqi@0:         Value f = entry->value();
aoqi@0: 
aoqi@0:         if (!is_killed(f) && f->is_equal(x)) {
aoqi@0:           NOT_PRODUCT(_number_of_hits++);
aoqi@0:           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()));
aoqi@0: 
aoqi@0:           if (entry->nesting() != nesting() && f->as_Constant() == NULL) {
aoqi@0:             // non-constant values of of another block must be pinned,
aoqi@0:             // otherwise it is possible that they are not evaluated
aoqi@0:             f->pin(Instruction::PinGlobalValueNumbering);
aoqi@0:           }
aoqi@0:           assert(x->type()->tag() == f->type()->tag(), "should have same type");
aoqi@0: 
aoqi@0:           return f;
aoqi@0: 
aoqi@0:         }
aoqi@0:       }
aoqi@0:     }
aoqi@0: 
aoqi@0:     // x not found, so insert it
aoqi@0:     if (entry_count() >= size_threshold()) {
aoqi@0:       increase_table_size();
aoqi@0:     }
aoqi@0:     int idx = entry_index(hash, size());
aoqi@0:     _entries.at_put(idx, new ValueMapEntry(hash, x, nesting(), entry_at(idx)));
aoqi@0:     _entry_count++;
aoqi@0: 
aoqi@0:     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()));
aoqi@0:   }
aoqi@0: 
aoqi@0:   return x;
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: #define GENERIC_KILL_VALUE(must_kill_implementation)                                     \
aoqi@0:   NOT_PRODUCT(_number_of_kills++);                                                       \
aoqi@0:                                                                                          \
aoqi@0:   for (int i = size() - 1; i >= 0; i--) {                                                \
aoqi@0:     ValueMapEntry* prev_entry = NULL;                                                    \
aoqi@0:     for (ValueMapEntry* entry = entry_at(i); entry != NULL; entry = entry->next()) {     \
aoqi@0:       Value value = entry->value();                                                      \
aoqi@0:                                                                                          \
aoqi@0:       must_kill_implementation(must_kill, entry, value)                                  \
aoqi@0:                                                                                          \
aoqi@0:       if (must_kill) {                                                                   \
aoqi@0:         kill_value(value);                                                               \
aoqi@0:                                                                                          \
aoqi@0:         if (prev_entry == NULL) {                                                        \
aoqi@0:           _entries.at_put(i, entry->next());                                             \
aoqi@0:           _entry_count--;                                                                \
aoqi@0:         } else if (prev_entry->nesting() == nesting()) {                                 \
aoqi@0:           prev_entry->set_next(entry->next());                                           \
aoqi@0:           _entry_count--;                                                                \
aoqi@0:         } else {                                                                         \
aoqi@0:           prev_entry = entry;                                                            \
aoqi@0:         }                                                                                \
aoqi@0:                                                                                          \
aoqi@0:         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()));   \
aoqi@0:       } else {                                                                           \
aoqi@0:         prev_entry = entry;                                                              \
aoqi@0:       }                                                                                  \
aoqi@0:     }                                                                                    \
aoqi@0:   }                                                                                      \
aoqi@0: 
aoqi@0: #define MUST_KILL_MEMORY(must_kill, entry, value)                                        \
aoqi@0:   bool must_kill = value->as_LoadField() != NULL || value->as_LoadIndexed() != NULL;
aoqi@0: 
aoqi@0: #define MUST_KILL_ARRAY(must_kill, entry, value)                                         \
aoqi@0:   bool must_kill = value->as_LoadIndexed() != NULL                                       \
aoqi@0:                    && value->type()->tag() == type->tag();
aoqi@0: 
aoqi@0: #define MUST_KILL_FIELD(must_kill, entry, value)                                         \
aoqi@0:   /* ciField's are not unique; must compare their contents */                            \
aoqi@0:   LoadField* lf = value->as_LoadField();                                                 \
aoqi@0:   bool must_kill = lf != NULL                                                            \
aoqi@0:                    && lf->field()->holder() == field->holder()                           \
aoqi@0:                    && (all_offsets || lf->field()->offset() == field->offset());
aoqi@0: 
aoqi@0: 
aoqi@0: void ValueMap::kill_memory() {
aoqi@0:   GENERIC_KILL_VALUE(MUST_KILL_MEMORY);
aoqi@0: }
aoqi@0: 
aoqi@0: void ValueMap::kill_array(ValueType* type) {
aoqi@0:   GENERIC_KILL_VALUE(MUST_KILL_ARRAY);
aoqi@0: }
aoqi@0: 
aoqi@0: void ValueMap::kill_field(ciField* field, bool all_offsets) {
aoqi@0:   GENERIC_KILL_VALUE(MUST_KILL_FIELD);
aoqi@0: }
aoqi@0: 
aoqi@0: void ValueMap::kill_map(ValueMap* map) {
aoqi@0:   assert(is_global_value_numbering(), "only for global value numbering");
aoqi@0:   _killed_values.set_union(&map->_killed_values);
aoqi@0: }
aoqi@0: 
aoqi@0: void ValueMap::kill_all() {
aoqi@0:   assert(is_local_value_numbering(), "only for local value numbering");
aoqi@0:   for (int i = size() - 1; i >= 0; i--) {
aoqi@0:     _entries.at_put(i, NULL);
aoqi@0:   }
aoqi@0:   _entry_count = 0;
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: #ifndef PRODUCT
aoqi@0: 
aoqi@0: void ValueMap::print() {
aoqi@0:   tty->print_cr("(size %d, entries %d, nesting %d)", size(), entry_count(), nesting());
aoqi@0: 
aoqi@0:   int entries = 0;
aoqi@0:   for (int i = 0; i < size(); i++) {
aoqi@0:     if (entry_at(i) != NULL) {
aoqi@0:       tty->print("  %2d: ", i);
aoqi@0:       for (ValueMapEntry* entry = entry_at(i); entry != NULL; entry = entry->next()) {
aoqi@0:         Value value = entry->value();
aoqi@0:         tty->print("%s %c%d (%s%d) -> ", value->name(), value->type()->tchar(), value->id(), is_killed(value) ? "x" : "", entry->nesting());
aoqi@0:         entries++;
aoqi@0:       }
aoqi@0:       tty->print_cr("NULL");
aoqi@0:     }
aoqi@0:   }
aoqi@0: 
aoqi@0:   _killed_values.print();
aoqi@0:   assert(entry_count() == entries, "entry_count incorrect");
aoqi@0: }
aoqi@0: 
aoqi@0: void ValueMap::reset_statistics() {
aoqi@0:   _number_of_finds = 0;
aoqi@0:   _number_of_hits = 0;
aoqi@0:   _number_of_kills = 0;
aoqi@0: }
aoqi@0: 
aoqi@0: void ValueMap::print_statistics() {
aoqi@0:   float hit_rate = 0;
aoqi@0:   if (_number_of_finds != 0) {
aoqi@0:     hit_rate = (float)_number_of_hits / _number_of_finds;
aoqi@0:   }
aoqi@0: 
aoqi@0:   tty->print_cr("finds:%3d  hits:%3d   kills:%3d  hit rate: %1.4f", _number_of_finds, _number_of_hits, _number_of_kills, hit_rate);
aoqi@0: }
aoqi@0: 
aoqi@0: #endif
aoqi@0: 
aoqi@0: 
aoqi@0: 
aoqi@0: class ShortLoopOptimizer : public ValueNumberingVisitor {
aoqi@0:  private:
aoqi@0:   GlobalValueNumbering* _gvn;
aoqi@0:   BlockList             _loop_blocks;
aoqi@0:   bool                  _too_complicated_loop;
aoqi@0:   bool                  _has_field_store[T_ARRAY + 1];
aoqi@0:   bool                  _has_indexed_store[T_ARRAY + 1];
aoqi@0: 
aoqi@0:   // simplified access to methods of GlobalValueNumbering
aoqi@0:   ValueMap* current_map()                        { return _gvn->current_map(); }
aoqi@0:   ValueMap* value_map_of(BlockBegin* block)      { return _gvn->value_map_of(block); }
aoqi@0: 
aoqi@0:   // implementation for abstract methods of ValueNumberingVisitor
aoqi@0:   void      kill_memory()                                 { _too_complicated_loop = true; }
aoqi@0:   void      kill_field(ciField* field, bool all_offsets)  {
aoqi@0:     current_map()->kill_field(field, all_offsets);
aoqi@0:     assert(field->type()->basic_type() >= 0 && field->type()->basic_type() <= T_ARRAY, "Invalid type");
aoqi@0:     _has_field_store[field->type()->basic_type()] = true;
aoqi@0:   }
aoqi@0:   void      kill_array(ValueType* type)                   {
aoqi@0:     current_map()->kill_array(type);
aoqi@0:     BasicType basic_type = as_BasicType(type); assert(basic_type >= 0 && basic_type <= T_ARRAY, "Invalid type");
aoqi@0:     _has_indexed_store[basic_type] = true;
aoqi@0:   }
aoqi@0: 
aoqi@0:  public:
aoqi@0:   ShortLoopOptimizer(GlobalValueNumbering* gvn)
aoqi@0:     : _gvn(gvn)
aoqi@0:     , _loop_blocks(ValueMapMaxLoopSize)
aoqi@0:     , _too_complicated_loop(false)
aoqi@0:   {
aoqi@0:     for (int i=0; i<= T_ARRAY; i++){
aoqi@0:       _has_field_store[i] = false;
aoqi@0:       _has_indexed_store[i] = false;
aoqi@0:     }
aoqi@0:   }
aoqi@0: 
aoqi@0:   bool has_field_store(BasicType type) {
aoqi@0:     assert(type >= 0 && type <= T_ARRAY, "Invalid type");
aoqi@0:     return _has_field_store[type];
aoqi@0:   }
aoqi@0: 
aoqi@0:   bool has_indexed_store(BasicType type) {
aoqi@0:     assert(type >= 0 && type <= T_ARRAY, "Invalid type");
aoqi@0:     return _has_indexed_store[type];
aoqi@0:   }
aoqi@0: 
aoqi@0:   bool process(BlockBegin* loop_header);
aoqi@0: };
aoqi@0: 
aoqi@0: class LoopInvariantCodeMotion : public StackObj  {
aoqi@0:  private:
aoqi@0:   GlobalValueNumbering* _gvn;
aoqi@0:   ShortLoopOptimizer*   _short_loop_optimizer;
aoqi@0:   Instruction*          _insertion_point;
aoqi@0:   ValueStack *          _state;
aoqi@0:   bool                  _insert_is_pred;
aoqi@0: 
aoqi@0:   void set_invariant(Value v) const    { _gvn->set_processed(v); }
aoqi@0:   bool is_invariant(Value v) const     { return _gvn->is_processed(v); }
aoqi@0: 
aoqi@0:   void process_block(BlockBegin* block);
aoqi@0: 
aoqi@0:  public:
aoqi@0:   LoopInvariantCodeMotion(ShortLoopOptimizer *slo, GlobalValueNumbering* gvn, BlockBegin* loop_header, BlockList* loop_blocks);
aoqi@0: };
aoqi@0: 
aoqi@0: LoopInvariantCodeMotion::LoopInvariantCodeMotion(ShortLoopOptimizer *slo, GlobalValueNumbering* gvn, BlockBegin* loop_header, BlockList* loop_blocks)
aoqi@0:   : _gvn(gvn), _short_loop_optimizer(slo) {
aoqi@0: 
aoqi@0:   TRACE_VALUE_NUMBERING(tty->print_cr("using loop invariant code motion loop_header = %d", loop_header->block_id()));
aoqi@0:   TRACE_VALUE_NUMBERING(tty->print_cr("** loop invariant code motion for short loop B%d", loop_header->block_id()));
aoqi@0: 
aoqi@0:   BlockBegin* insertion_block = loop_header->dominator();
aoqi@0:   if (insertion_block->number_of_preds() == 0) {
aoqi@0:     return;  // only the entry block does not have a predecessor
aoqi@0:   }
aoqi@0: 
aoqi@0:   assert(insertion_block->end()->as_Base() == NULL, "cannot insert into entry block");
aoqi@0:   _insertion_point = insertion_block->end()->prev();
aoqi@0:   _insert_is_pred = loop_header->is_predecessor(insertion_block);
aoqi@0: 
aoqi@0:   BlockEnd *block_end = insertion_block->end();
aoqi@0:   _state = block_end->state_before();
aoqi@0: 
aoqi@0:   if (!_state) {
aoqi@0:     // If, TableSwitch and LookupSwitch always have state_before when
aoqi@0:     // loop invariant code motion happens..
aoqi@0:     assert(block_end->as_Goto(), "Block has to be goto");
aoqi@0:     _state = block_end->state();
aoqi@0:   }
aoqi@0: 
aoqi@0:   // the loop_blocks are filled by going backward from the loop header, so this processing order is best
aoqi@0:   assert(loop_blocks->at(0) == loop_header, "loop header must be first loop block");
aoqi@0:   process_block(loop_header);
aoqi@0:   for (int i = loop_blocks->length() - 1; i >= 1; i--) {
aoqi@0:     process_block(loop_blocks->at(i));
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: void LoopInvariantCodeMotion::process_block(BlockBegin* block) {
aoqi@0:   TRACE_VALUE_NUMBERING(tty->print_cr("processing block B%d", block->block_id()));
aoqi@0: 
aoqi@0:   Instruction* prev = block;
aoqi@0:   Instruction* cur = block->next();
aoqi@0: 
aoqi@0:   while (cur != NULL) {
aoqi@0: 
aoqi@0:     // determine if cur instruction is loop invariant
aoqi@0:     // only selected instruction types are processed here
aoqi@0:     bool cur_invariant = false;
aoqi@0: 
aoqi@0:     if (cur->as_Constant() != NULL) {
aoqi@0:       cur_invariant = !cur->can_trap();
aoqi@0:     } else if (cur->as_ArithmeticOp() != NULL || cur->as_LogicOp() != NULL || cur->as_ShiftOp() != NULL) {
aoqi@0:       assert(cur->as_Op2() != NULL, "must be Op2");
aoqi@0:       Op2* op2 = (Op2*)cur;
aoqi@0:       cur_invariant = !op2->can_trap() && is_invariant(op2->x()) && is_invariant(op2->y());
aoqi@0:     } else if (cur->as_LoadField() != NULL) {
aoqi@0:       LoadField* lf = (LoadField*)cur;
aoqi@0:       // deoptimizes on NullPointerException
aoqi@0:       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;
aoqi@0:     } else if (cur->as_ArrayLength() != NULL) {
aoqi@0:       ArrayLength *length = cur->as_ArrayLength();
aoqi@0:       cur_invariant = is_invariant(length->array());
aoqi@0:     } else if (cur->as_LoadIndexed() != NULL) {
aoqi@0:       LoadIndexed *li = (LoadIndexed *)cur->as_LoadIndexed();
aoqi@0:       cur_invariant = !_short_loop_optimizer->has_indexed_store(as_BasicType(cur->type())) && is_invariant(li->array()) && is_invariant(li->index()) && _insert_is_pred;
aoqi@0:     }
aoqi@0: 
aoqi@0:     if (cur_invariant) {
aoqi@0:       // perform value numbering and mark instruction as loop-invariant
aoqi@0:       _gvn->substitute(cur);
aoqi@0: 
aoqi@0:       if (cur->as_Constant() == NULL) {
aoqi@0:         // ensure that code for non-constant instructions is always generated
aoqi@0:         cur->pin();
aoqi@0:       }
aoqi@0: 
aoqi@0:       // remove cur instruction from loop block and append it to block before loop
aoqi@0:       Instruction* next = cur->next();
aoqi@0:       Instruction* in = _insertion_point->next();
aoqi@0:       _insertion_point = _insertion_point->set_next(cur);
aoqi@0:       cur->set_next(in);
aoqi@0: 
aoqi@0:       //  Deoptimize on exception
aoqi@0:       cur->set_flag(Instruction::DeoptimizeOnException, true);
aoqi@0: 
aoqi@0:       //  Clear exception handlers
aoqi@0:       cur->set_exception_handlers(NULL);
aoqi@0: 
aoqi@0:       TRACE_VALUE_NUMBERING(tty->print_cr("Instruction %c%d is loop invariant", cur->type()->tchar(), cur->id()));
aoqi@0: 
aoqi@0:       if (cur->state_before() != NULL) {
aoqi@0:         cur->set_state_before(_state->copy());
aoqi@0:       }
aoqi@0:       if (cur->exception_state() != NULL) {
aoqi@0:         cur->set_exception_state(_state->copy());
aoqi@0:       }
aoqi@0: 
aoqi@0:       cur = prev->set_next(next);
aoqi@0: 
aoqi@0:     } else {
aoqi@0:       prev = cur;
aoqi@0:       cur = cur->next();
aoqi@0:     }
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: bool ShortLoopOptimizer::process(BlockBegin* loop_header) {
aoqi@0:   TRACE_VALUE_NUMBERING(tty->print_cr("** loop header block"));
aoqi@0: 
aoqi@0:   _too_complicated_loop = false;
aoqi@0:   _loop_blocks.clear();
aoqi@0:   _loop_blocks.append(loop_header);
aoqi@0: 
aoqi@0:   for (int i = 0; i < _loop_blocks.length(); i++) {
aoqi@0:     BlockBegin* block = _loop_blocks.at(i);
aoqi@0:     TRACE_VALUE_NUMBERING(tty->print_cr("processing loop block B%d", block->block_id()));
aoqi@0: 
aoqi@0:     if (block->is_set(BlockBegin::exception_entry_flag)) {
aoqi@0:       // this would be too complicated
aoqi@0:       return false;
aoqi@0:     }
aoqi@0: 
aoqi@0:     // add predecessors to worklist
aoqi@0:     for (int j = block->number_of_preds() - 1; j >= 0; j--) {
aoqi@0:       BlockBegin* pred = block->pred_at(j);
aoqi@0: 
aoqi@0:       if (pred->is_set(BlockBegin::osr_entry_flag)) {
aoqi@0:         return false;
aoqi@0:       }
aoqi@0: 
aoqi@0:       ValueMap* pred_map = value_map_of(pred);
aoqi@0:       if (pred_map != NULL) {
aoqi@0:         current_map()->kill_map(pred_map);
aoqi@0:       } else if (!_loop_blocks.contains(pred)) {
aoqi@0:         if (_loop_blocks.length() >= ValueMapMaxLoopSize) {
aoqi@0:           return false;
aoqi@0:         }
aoqi@0:         _loop_blocks.append(pred);
aoqi@0:       }
aoqi@0:     }
aoqi@0: 
aoqi@0:     // use the instruction visitor for killing values
aoqi@0:     for (Value instr = block->next(); instr != NULL; instr = instr->next()) {
aoqi@0:       instr->visit(this);
aoqi@0:       if (_too_complicated_loop) {
aoqi@0:         return false;
aoqi@0:       }
aoqi@0:     }
aoqi@0:   }
aoqi@0: 
aoqi@0:   bool optimistic = this->_gvn->compilation()->is_optimistic();
aoqi@0: 
aoqi@0:   if (UseLoopInvariantCodeMotion && optimistic) {
aoqi@0:     LoopInvariantCodeMotion code_motion(this, _gvn, loop_header, &_loop_blocks);
aoqi@0:   }
aoqi@0: 
aoqi@0:   TRACE_VALUE_NUMBERING(tty->print_cr("** loop successfully optimized"));
aoqi@0:   return true;
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: GlobalValueNumbering::GlobalValueNumbering(IR* ir)
aoqi@0:   : _current_map(NULL)
aoqi@0:   , _value_maps(ir->linear_scan_order()->length(), NULL)
aoqi@0:   , _compilation(ir->compilation())
aoqi@0: {
aoqi@0:   TRACE_VALUE_NUMBERING(tty->print_cr("****** start of global value numbering"));
aoqi@0: 
aoqi@0:   ShortLoopOptimizer short_loop_optimizer(this);
aoqi@0: 
aoqi@0:   BlockList* blocks = ir->linear_scan_order();
aoqi@0:   int num_blocks = blocks->length();
aoqi@0: 
aoqi@0:   BlockBegin* start_block = blocks->at(0);
aoqi@0:   assert(start_block == ir->start() && start_block->number_of_preds() == 0 && start_block->dominator() == NULL, "must be start block");
aoqi@0:   assert(start_block->next()->as_Base() != NULL && start_block->next()->next() == NULL, "start block must not have instructions");
aoqi@0: 
aoqi@0:   // method parameters are not linked in instructions list, so process them separateley
aoqi@0:   for_each_state_value(start_block->state(), value,
aoqi@0:      assert(value->as_Local() != NULL, "only method parameters allowed");
aoqi@0:      set_processed(value);
aoqi@0:   );
aoqi@0: 
aoqi@0:   // initial, empty value map with nesting 0
aoqi@0:   set_value_map_of(start_block, new ValueMap());
aoqi@0: 
aoqi@0:   for (int i = 1; i < num_blocks; i++) {
aoqi@0:     BlockBegin* block = blocks->at(i);
aoqi@0:     TRACE_VALUE_NUMBERING(tty->print_cr("**** processing block B%d", block->block_id()));
aoqi@0: 
aoqi@0:     int num_preds = block->number_of_preds();
aoqi@0:     assert(num_preds > 0, "block must have predecessors");
aoqi@0: 
aoqi@0:     BlockBegin* dominator = block->dominator();
aoqi@0:     assert(dominator != NULL, "dominator must exist");
aoqi@0:     assert(value_map_of(dominator) != NULL, "value map of dominator must exist");
aoqi@0: 
aoqi@0:     // create new value map with increased nesting
aoqi@0:     _current_map = new ValueMap(value_map_of(dominator));
aoqi@0: 
aoqi@0:     if (num_preds == 1 && !block->is_set(BlockBegin::exception_entry_flag)) {
aoqi@0:       assert(dominator == block->pred_at(0), "dominator must be equal to predecessor");
aoqi@0:       // nothing to do here
aoqi@0: 
aoqi@0:     } else if (block->is_set(BlockBegin::linear_scan_loop_header_flag)) {
aoqi@0:       // block has incoming backward branches -> try to optimize short loops
aoqi@0:       if (!short_loop_optimizer.process(block)) {
aoqi@0:         // loop is too complicated, so kill all memory loads because there might be
aoqi@0:         // stores to them in the loop
aoqi@0:         current_map()->kill_memory();
aoqi@0:       }
aoqi@0: 
aoqi@0:     } else {
aoqi@0:       // only incoming forward branches that are already processed
aoqi@0:       for (int j = 0; j < num_preds; j++) {
aoqi@0:         BlockBegin* pred = block->pred_at(j);
aoqi@0:         ValueMap* pred_map = value_map_of(pred);
aoqi@0: 
aoqi@0:         if (pred_map != NULL) {
aoqi@0:           // propagate killed values of the predecessor to this block
aoqi@0:           current_map()->kill_map(value_map_of(pred));
aoqi@0:         } else {
aoqi@0:           // kill all memory loads because predecessor not yet processed
aoqi@0:           // (this can happen with non-natural loops and OSR-compiles)
aoqi@0:           current_map()->kill_memory();
aoqi@0:         }
aoqi@0:       }
aoqi@0:     }
aoqi@0: 
aoqi@0:     // phi functions are not linked in instructions list, so process them separateley
aoqi@0:     for_each_phi_fun(block, phi,
aoqi@0:       set_processed(phi);
aoqi@0:     );
aoqi@0: 
aoqi@0:     TRACE_VALUE_NUMBERING(tty->print("value map before processing block: "); current_map()->print());
aoqi@0: 
aoqi@0:     // visit all instructions of this block
aoqi@0:     for (Value instr = block->next(); instr != NULL; instr = instr->next()) {
aoqi@0:       // check if instruction kills any values
aoqi@0:       instr->visit(this);
aoqi@0:       // perform actual value numbering
aoqi@0:       substitute(instr);
aoqi@0:     }
aoqi@0: 
aoqi@0:     // remember value map for successors
aoqi@0:     set_value_map_of(block, current_map());
aoqi@0:   }
aoqi@0: 
aoqi@0:   if (_has_substitutions) {
aoqi@0:     SubstitutionResolver resolver(ir);
aoqi@0:   }
aoqi@0: 
aoqi@0:   TRACE_VALUE_NUMBERING(tty->print("****** end of global value numbering. "); ValueMap::print_statistics());
aoqi@0: }
aoqi@0: 
aoqi@0: void GlobalValueNumbering::substitute(Instruction* instr) {
aoqi@0:   assert(!instr->has_subst(), "substitution already set");
aoqi@0:   Value subst = current_map()->find_insert(instr);
aoqi@0:   if (subst != instr) {
aoqi@0:     assert(!subst->has_subst(), "can't have a substitution");
aoqi@0: 
aoqi@0:     TRACE_VALUE_NUMBERING(tty->print_cr("substitution for %d set to %d", instr->id(), subst->id()));
aoqi@0:     instr->set_subst(subst);
aoqi@0:     _has_substitutions = true;
aoqi@0:   }
aoqi@0:   set_processed(instr);
aoqi@0: }