LoopInvariantCodeMotion::LoopInvariantCodeMotion(ShortLoopOptimizer *slo, GlobalValueNumbering* gvn, BlockBegin* loop_header, BlockList* loop_blocks) : _gvn(gvn), _short_loop_optimizer(slo) { TRACE_VALUE_NUMBERING(tty->print_cr("using loop invariant code motion loop_header = %d", loop_header->block_id())); TRACE_VALUE_NUMBERING(tty->print_cr("** loop invariant code motion for short loop B%d", loop_header->block_id())); BlockBegin* insertion_block = loop_header->dominator(); if (insertion_block->number_of_preds() == 0) { return; // only the entry block does not have a predecessor } assert(insertion_block->end()->as_Base() == NULL, "cannot insert into entry block"); _insertion_point = insertion_block->end()->prev(); _insert_is_pred = loop_header->is_predecessor(insertion_block); BlockEnd *block_end = insertion_block->end(); _state = block_end->state_before(); if (!_state) { // If, TableSwitch and LookupSwitch always have state_before when // loop invariant code motion happens.. assert(block_end->as_Goto(), "Block has to be goto"); _state = block_end->state(); } // the loop_blocks are filled by going backward from the loop header, so this processing order is best assert(loop_blocks->at(0) == loop_header, "loop header must be first loop block"); process_block(loop_header); for (int i = loop_blocks->length() - 1; i >= 1; i--) { process_block(loop_blocks->at(i)); } }
bool ShortLoopOptimizer::process(BlockBegin* loop_header) { TRACE_VALUE_NUMBERING(tty->print_cr("** loop header block")); _too_complicated_loop = false; _loop_blocks.clear(); _loop_blocks.append(loop_header); for (int i = 0; i < _loop_blocks.length(); i++) { BlockBegin* block = _loop_blocks.at(i); TRACE_VALUE_NUMBERING(tty->print_cr("processing loop block B%d", block->block_id())); if (block->is_set(BlockBegin::exception_entry_flag)) { // this would be too complicated return false; } // add predecessors to worklist for (int j = block->number_of_preds() - 1; j >= 0; j--) { BlockBegin* pred = block->pred_at(j); if (pred->is_set(BlockBegin::osr_entry_flag)) { return false; } ValueMap* pred_map = value_map_of(pred); if (pred_map != NULL) { current_map()->kill_map(pred_map); } else if (!_loop_blocks.contains(pred)) { if (_loop_blocks.length() >= ValueMapMaxLoopSize) { return false; } _loop_blocks.append(pred); } } // use the instruction visitor for killing values for (Value instr = block->next(); instr != NULL; instr = instr->next()) { instr->visit(this); if (_too_complicated_loop) { return false; } } } bool optimistic = this->_gvn->compilation()->is_optimistic(); if (UseLoopInvariantCodeMotion && optimistic) { LoopInvariantCodeMotion code_motion(this, _gvn, loop_header, &_loop_blocks); } TRACE_VALUE_NUMBERING(tty->print_cr("** loop successfully optimized")); return true; }
Value ValueMap::find_insert(Value x) { const intx hash = x->hash(); if (hash != 0) { // 0 hash means: exclude from value numbering NOT_PRODUCT(_number_of_finds++); for (ValueMapEntry* entry = entry_at(entry_index(hash, size())); entry != NULL; entry = entry->next()) { if (entry->hash() == hash) { Value f = entry->value(); if (!is_killed(f) && f->is_equal(x)) { NOT_PRODUCT(_number_of_hits++); 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())); if (entry->nesting() != nesting() && f->as_Constant() == NULL) { // non-constant values of of another block must be pinned, // otherwise it is possible that they are not evaluated f->pin(Instruction::PinGlobalValueNumbering); } assert(x->type()->tag() == f->type()->tag(), "should have same type"); return f; } } } // x not found, so insert it if (entry_count() >= size_threshold()) { increase_table_size(); } int idx = entry_index(hash, size()); _entries.at_put(idx, new ValueMapEntry(hash, x, nesting(), entry_at(idx))); _entry_count++; 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())); } return x; }
GlobalValueNumbering::GlobalValueNumbering(IR* ir) : _current_map(NULL) , _value_maps(ir->linear_scan_order()->length(), NULL) , _compilation(ir->compilation()) { TRACE_VALUE_NUMBERING(tty->print_cr("****** start of global value numbering")); ShortLoopOptimizer short_loop_optimizer(this); BlockList* blocks = ir->linear_scan_order(); int num_blocks = blocks->length(); BlockBegin* start_block = blocks->at(0); assert(start_block == ir->start() && start_block->number_of_preds() == 0 && start_block->dominator() == NULL, "must be start block"); assert(start_block->next()->as_Base() != NULL && start_block->next()->next() == NULL, "start block must not have instructions"); // method parameters are not linked in instructions list, so process them separateley for_each_state_value(start_block->state(), value, assert(value->as_Local() != NULL, "only method parameters allowed"); set_processed(value); );
void ValueMap::increase_table_size() { int old_size = size(); int new_size = old_size * 2 + 1; ValueMapEntryList worklist(8); ValueMapEntryArray new_entries(new_size, NULL); int new_entry_count = 0; TRACE_VALUE_NUMBERING(tty->print_cr("increasing table size from %d to %d", old_size, new_size)); for (int i = old_size - 1; i >= 0; i--) { ValueMapEntry* entry; for (entry = entry_at(i); entry != NULL; entry = entry->next()) { if (!is_killed(entry->value())) { worklist.push(entry); } } while (!worklist.is_empty()) { entry = worklist.pop(); int new_index = entry_index(entry->hash(), new_size); if (entry->nesting() != nesting() && new_entries.at(new_index) != entry->next()) { // changing entries with a lower nesting than the current nesting of the table // is not allowed because then the same entry is contained in multiple value maps. // clone entry when next-pointer must be changed entry = new ValueMapEntry(entry->hash(), entry->value(), entry->nesting(), NULL); } entry->set_next(new_entries.at(new_index)); new_entries.at_put(new_index, entry); new_entry_count++; } } _entries = new_entries; _entry_count = new_entry_count; }
void LoopInvariantCodeMotion::process_block(BlockBegin* block) { TRACE_VALUE_NUMBERING(tty->print_cr("processing block B%d", block->block_id())); Instruction* prev = block; Instruction* cur = block->next(); while (cur != NULL) { // determine if cur instruction is loop invariant // only selected instruction types are processed here bool cur_invariant = false; if (cur->as_Constant() != NULL) { cur_invariant = !cur->can_trap(); } else if (cur->as_ArithmeticOp() != NULL || cur->as_LogicOp() != NULL || cur->as_ShiftOp() != NULL) { assert(cur->as_Op2() != NULL, "must be Op2"); Op2* op2 = (Op2*)cur; cur_invariant = !op2->can_trap() && is_invariant(op2->x()) && is_invariant(op2->y()); } else if (cur->as_LoadField() != NULL) { LoadField* lf = (LoadField*)cur; // deoptimizes on NullPointerException 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; } else if (cur->as_ArrayLength() != NULL) { ArrayLength *length = cur->as_ArrayLength(); cur_invariant = is_invariant(length->array()); } else if (cur->as_LoadIndexed() != NULL) { LoadIndexed *li = (LoadIndexed *)cur->as_LoadIndexed(); cur_invariant = !_short_loop_optimizer->has_indexed_store(as_BasicType(cur->type())) && is_invariant(li->array()) && is_invariant(li->index()) && _insert_is_pred; } if (cur_invariant) { // perform value numbering and mark instruction as loop-invariant _gvn->substitute(cur); if (cur->as_Constant() == NULL) { // ensure that code for non-constant instructions is always generated cur->pin(); } // remove cur instruction from loop block and append it to block before loop Instruction* next = cur->next(); Instruction* in = _insertion_point->next(); _insertion_point = _insertion_point->set_next(cur); cur->set_next(in); // Deoptimize on exception cur->set_flag(Instruction::DeoptimizeOnException, true); // Clear exception handlers cur->set_exception_handlers(NULL); TRACE_VALUE_NUMBERING(tty->print_cr("Instruction %c%d is loop invariant", cur->type()->tchar(), cur->id())); if (cur->state_before() != NULL) { cur->set_state_before(_state->copy()); } if (cur->exception_state() != NULL) { cur->set_exception_state(_state->copy()); } cur = prev->set_next(next); } else { prev = cur; cur = cur->next(); } } }
GlobalValueNumbering::GlobalValueNumbering(IR* ir) : _current_map(NULL) , _value_maps(ir->linear_scan_order()->length(), NULL) { TRACE_VALUE_NUMBERING(tty->print_cr("****** start of global value numbering")); ShortLoopOptimizer short_loop_optimizer(this); int subst_count = 0; BlockList* blocks = ir->linear_scan_order(); int num_blocks = blocks->length(); BlockBegin* start_block = blocks->at(0); assert(start_block == ir->start() && start_block->number_of_preds() == 0 && start_block->dominator() == NULL, "must be start block"); assert(start_block->next()->as_Base() != NULL && start_block->next()->next() == NULL, "start block must not have instructions"); // initial, empty value map with nesting 0 set_value_map_of(start_block, new ValueMap()); for (int i = 1; i < num_blocks; i++) { BlockBegin* block = blocks->at(i); TRACE_VALUE_NUMBERING(tty->print_cr("**** processing block B%d", block->block_id())); int num_preds = block->number_of_preds(); assert(num_preds > 0, "block must have predecessors"); BlockBegin* dominator = block->dominator(); assert(dominator != NULL, "dominator must exist"); assert(value_map_of(dominator) != NULL, "value map of dominator must exist"); // create new value map with increased nesting _current_map = new ValueMap(value_map_of(dominator)); if (num_preds == 1) { assert(dominator == block->pred_at(0), "dominator must be equal to predecessor"); // nothing to do here } else if (block->is_set(BlockBegin::linear_scan_loop_header_flag)) { // block has incoming backward branches -> try to optimize short loops if (!short_loop_optimizer.process(block)) { // loop is too complicated, so kill all memory loads because there might be // stores to them in the loop current_map()->kill_memory(); } } else { // only incoming forward branches that are already processed for (int j = 0; j < num_preds; j++) { BlockBegin* pred = block->pred_at(j); ValueMap* pred_map = value_map_of(pred); if (pred_map != NULL) { // propagate killed values of the predecessor to this block current_map()->kill_map(value_map_of(pred)); } else { // kill all memory loads because predecessor not yet processed // (this can happen with non-natural loops and OSR-compiles) current_map()->kill_memory(); } } } if (block->is_set(BlockBegin::exception_entry_flag)) { current_map()->kill_exception(); } TRACE_VALUE_NUMBERING(tty->print("value map before processing block: "); current_map()->print()); // visit all instructions of this block for (Value instr = block->next(); instr != NULL; instr = instr->next()) { assert(!instr->has_subst(), "substitution already set"); // check if instruction kills any values instr->visit(this); if (instr->hash() != 0) { Value f = current_map()->find_insert(instr); if (f != instr) { assert(!f->has_subst(), "can't have a substitution"); instr->set_subst(f); subst_count++; } } } // remember value map for successors set_value_map_of(block, current_map()); } if (subst_count != 0) { SubstitutionResolver resolver(ir); } TRACE_VALUE_NUMBERING(tty->print("****** end of global value numbering. "); ValueMap::print_statistics()); }