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_Optimizer.hpp"
aoqi@0: #include "c1/c1_ValueMap.hpp"
aoqi@0: #include "c1/c1_ValueSet.hpp"
aoqi@0: #include "c1/c1_ValueStack.hpp"
aoqi@0: #include "utilities/bitMap.inline.hpp"
aoqi@0: #include "compiler/compileLog.hpp"
aoqi@0: 
aoqi@0: define_array(ValueSetArray, ValueSet*);
aoqi@0: define_stack(ValueSetList, ValueSetArray);
aoqi@0: 
aoqi@0: 
aoqi@0: Optimizer::Optimizer(IR* ir) {
aoqi@0:   assert(ir->is_valid(), "IR must be valid");
aoqi@0:   _ir = ir;
aoqi@0: }
aoqi@0: 
aoqi@0: class CE_Eliminator: public BlockClosure {
aoqi@0:  private:
aoqi@0:   IR* _hir;
aoqi@0:   int _cee_count;                                // the number of CEs successfully eliminated
aoqi@0:   int _ifop_count;                               // the number of IfOps successfully simplified
aoqi@0:   int _has_substitution;
aoqi@0: 
aoqi@0:  public:
aoqi@0:   CE_Eliminator(IR* hir) : _cee_count(0), _ifop_count(0), _hir(hir) {
aoqi@0:     _has_substitution = false;
aoqi@0:     _hir->iterate_preorder(this);
aoqi@0:     if (_has_substitution) {
aoqi@0:       // substituted some ifops/phis, so resolve the substitution
aoqi@0:       SubstitutionResolver sr(_hir);
aoqi@0:     }
aoqi@0: 
aoqi@0:     CompileLog* log = _hir->compilation()->log();
aoqi@0:     if (log != NULL)
aoqi@0:       log->set_context("optimize name='cee'");
aoqi@0:   }
aoqi@0: 
aoqi@0:   ~CE_Eliminator() {
aoqi@0:     CompileLog* log = _hir->compilation()->log();
aoqi@0:     if (log != NULL)
aoqi@0:       log->clear_context(); // skip marker if nothing was printed
aoqi@0:   }
aoqi@0: 
aoqi@0:   int cee_count() const                          { return _cee_count; }
aoqi@0:   int ifop_count() const                         { return _ifop_count; }
aoqi@0: 
aoqi@0:   void adjust_exception_edges(BlockBegin* block, BlockBegin* sux) {
aoqi@0:     int e = sux->number_of_exception_handlers();
aoqi@0:     for (int i = 0; i < e; i++) {
aoqi@0:       BlockBegin* xhandler = sux->exception_handler_at(i);
aoqi@0:       block->add_exception_handler(xhandler);
aoqi@0: 
aoqi@0:       assert(xhandler->is_predecessor(sux), "missing predecessor");
aoqi@0:       if (sux->number_of_preds() == 0) {
aoqi@0:         // sux is disconnected from graph so disconnect from exception handlers
aoqi@0:         xhandler->remove_predecessor(sux);
aoqi@0:       }
aoqi@0:       if (!xhandler->is_predecessor(block)) {
aoqi@0:         xhandler->add_predecessor(block);
aoqi@0:       }
aoqi@0:     }
aoqi@0:   }
aoqi@0: 
aoqi@0:   virtual void block_do(BlockBegin* block);
aoqi@0: 
aoqi@0:  private:
aoqi@0:   Value make_ifop(Value x, Instruction::Condition cond, Value y, Value tval, Value fval);
aoqi@0: };
aoqi@0: 
aoqi@0: void CE_Eliminator::block_do(BlockBegin* block) {
aoqi@0:   // 1) find conditional expression
aoqi@0:   // check if block ends with an If
aoqi@0:   If* if_ = block->end()->as_If();
aoqi@0:   if (if_ == NULL) return;
aoqi@0: 
aoqi@0:   // check if If works on int or object types
aoqi@0:   // (we cannot handle If's working on long, float or doubles yet,
aoqi@0:   // since IfOp doesn't support them - these If's show up if cmp
aoqi@0:   // operations followed by If's are eliminated)
aoqi@0:   ValueType* if_type = if_->x()->type();
aoqi@0:   if (!if_type->is_int() && !if_type->is_object()) return;
aoqi@0: 
aoqi@0:   BlockBegin* t_block = if_->tsux();
aoqi@0:   BlockBegin* f_block = if_->fsux();
aoqi@0:   Instruction* t_cur = t_block->next();
aoqi@0:   Instruction* f_cur = f_block->next();
aoqi@0: 
aoqi@0:   // one Constant may be present between BlockBegin and BlockEnd
aoqi@0:   Value t_const = NULL;
aoqi@0:   Value f_const = NULL;
aoqi@0:   if (t_cur->as_Constant() != NULL && !t_cur->can_trap()) {
aoqi@0:     t_const = t_cur;
aoqi@0:     t_cur = t_cur->next();
aoqi@0:   }
aoqi@0:   if (f_cur->as_Constant() != NULL && !f_cur->can_trap()) {
aoqi@0:     f_const = f_cur;
aoqi@0:     f_cur = f_cur->next();
aoqi@0:   }
aoqi@0: 
aoqi@0:   // check if both branches end with a goto
aoqi@0:   Goto* t_goto = t_cur->as_Goto();
aoqi@0:   if (t_goto == NULL) return;
aoqi@0:   Goto* f_goto = f_cur->as_Goto();
aoqi@0:   if (f_goto == NULL) return;
aoqi@0: 
aoqi@0:   // check if both gotos merge into the same block
aoqi@0:   BlockBegin* sux = t_goto->default_sux();
aoqi@0:   if (sux != f_goto->default_sux()) return;
aoqi@0: 
aoqi@0:   // check if at least one word was pushed on sux_state
aoqi@0:   // inlining depths must match
aoqi@0:   ValueStack* if_state = if_->state();
aoqi@0:   ValueStack* sux_state = sux->state();
aoqi@0:   if (if_state->scope()->level() > sux_state->scope()->level()) {
aoqi@0:     while (sux_state->scope() != if_state->scope()) {
aoqi@0:       if_state = if_state->caller_state();
aoqi@0:       assert(if_state != NULL, "states do not match up");
aoqi@0:     }
aoqi@0:   } else if (if_state->scope()->level() < sux_state->scope()->level()) {
aoqi@0:     while (sux_state->scope() != if_state->scope()) {
aoqi@0:       sux_state = sux_state->caller_state();
aoqi@0:       assert(sux_state != NULL, "states do not match up");
aoqi@0:     }
aoqi@0:   }
aoqi@0: 
aoqi@0:   if (sux_state->stack_size() <= if_state->stack_size()) return;
aoqi@0: 
aoqi@0:   // check if phi function is present at end of successor stack and that
aoqi@0:   // only this phi was pushed on the stack
aoqi@0:   Value sux_phi = sux_state->stack_at(if_state->stack_size());
aoqi@0:   if (sux_phi == NULL || sux_phi->as_Phi() == NULL || sux_phi->as_Phi()->block() != sux) return;
aoqi@0:   if (sux_phi->type()->size() != sux_state->stack_size() - if_state->stack_size()) return;
aoqi@0: 
aoqi@0:   // get the values that were pushed in the true- and false-branch
aoqi@0:   Value t_value = t_goto->state()->stack_at(if_state->stack_size());
aoqi@0:   Value f_value = f_goto->state()->stack_at(if_state->stack_size());
aoqi@0: 
aoqi@0:   // backend does not support floats
aoqi@0:   assert(t_value->type()->base() == f_value->type()->base(), "incompatible types");
aoqi@0:   if (t_value->type()->is_float_kind()) return;
aoqi@0: 
aoqi@0:   // check that successor has no other phi functions but sux_phi
aoqi@0:   // this can happen when t_block or f_block contained additonal stores to local variables
aoqi@0:   // that are no longer represented by explicit instructions
aoqi@0:   for_each_phi_fun(sux, phi,
aoqi@0:                    if (phi != sux_phi) return;
aoqi@0:                    );
aoqi@0:   // true and false blocks can't have phis
aoqi@0:   for_each_phi_fun(t_block, phi, return; );
aoqi@0:   for_each_phi_fun(f_block, phi, return; );
aoqi@0: 
aoqi@0:   // 2) substitute conditional expression
aoqi@0:   //    with an IfOp followed by a Goto
aoqi@0:   // cut if_ away and get node before
aoqi@0:   Instruction* cur_end = if_->prev();
aoqi@0: 
aoqi@0:   // append constants of true- and false-block if necessary
aoqi@0:   // clone constants because original block must not be destroyed
aoqi@0:   assert((t_value != f_const && f_value != t_const) || t_const == f_const, "mismatch");
aoqi@0:   if (t_value == t_const) {
aoqi@0:     t_value = new Constant(t_const->type());
aoqi@0:     NOT_PRODUCT(t_value->set_printable_bci(if_->printable_bci()));
aoqi@0:     cur_end = cur_end->set_next(t_value);
aoqi@0:   }
aoqi@0:   if (f_value == f_const) {
aoqi@0:     f_value = new Constant(f_const->type());
aoqi@0:     NOT_PRODUCT(f_value->set_printable_bci(if_->printable_bci()));
aoqi@0:     cur_end = cur_end->set_next(f_value);
aoqi@0:   }
aoqi@0: 
aoqi@0:   Value result = make_ifop(if_->x(), if_->cond(), if_->y(), t_value, f_value);
aoqi@0:   assert(result != NULL, "make_ifop must return a non-null instruction");
aoqi@0:   if (!result->is_linked() && result->can_be_linked()) {
aoqi@0:     NOT_PRODUCT(result->set_printable_bci(if_->printable_bci()));
aoqi@0:     cur_end = cur_end->set_next(result);
aoqi@0:   }
aoqi@0: 
aoqi@0:   // append Goto to successor
aoqi@0:   ValueStack* state_before = if_->state_before();
aoqi@0:   Goto* goto_ = new Goto(sux, state_before, if_->is_safepoint() || t_goto->is_safepoint() || f_goto->is_safepoint());
aoqi@0: 
aoqi@0:   // prepare state for Goto
aoqi@0:   ValueStack* goto_state = if_state;
aoqi@0:   goto_state = goto_state->copy(ValueStack::StateAfter, goto_state->bci());
aoqi@0:   goto_state->push(result->type(), result);
aoqi@0:   assert(goto_state->is_same(sux_state), "states must match now");
aoqi@0:   goto_->set_state(goto_state);
aoqi@0: 
aoqi@0:   cur_end = cur_end->set_next(goto_, goto_state->bci());
aoqi@0: 
aoqi@0:   // Adjust control flow graph
aoqi@0:   BlockBegin::disconnect_edge(block, t_block);
aoqi@0:   BlockBegin::disconnect_edge(block, f_block);
aoqi@0:   if (t_block->number_of_preds() == 0) {
aoqi@0:     BlockBegin::disconnect_edge(t_block, sux);
aoqi@0:   }
aoqi@0:   adjust_exception_edges(block, t_block);
aoqi@0:   if (f_block->number_of_preds() == 0) {
aoqi@0:     BlockBegin::disconnect_edge(f_block, sux);
aoqi@0:   }
aoqi@0:   adjust_exception_edges(block, f_block);
aoqi@0: 
aoqi@0:   // update block end
aoqi@0:   block->set_end(goto_);
aoqi@0: 
aoqi@0:   // substitute the phi if possible
aoqi@0:   if (sux_phi->as_Phi()->operand_count() == 1) {
aoqi@0:     assert(sux_phi->as_Phi()->operand_at(0) == result, "screwed up phi");
aoqi@0:     sux_phi->set_subst(result);
aoqi@0:     _has_substitution = true;
aoqi@0:   }
aoqi@0: 
aoqi@0:   // 3) successfully eliminated a conditional expression
aoqi@0:   _cee_count++;
aoqi@0:   if (PrintCEE) {
aoqi@0:     tty->print_cr("%d. CEE in B%d (B%d B%d)", cee_count(), block->block_id(), t_block->block_id(), f_block->block_id());
aoqi@0:     tty->print_cr("%d. IfOp in B%d", ifop_count(), block->block_id());
aoqi@0:   }
aoqi@0: 
aoqi@0:   _hir->verify();
aoqi@0: }
aoqi@0: 
aoqi@0: Value CE_Eliminator::make_ifop(Value x, Instruction::Condition cond, Value y, Value tval, Value fval) {
aoqi@0:   if (!OptimizeIfOps) {
aoqi@0:     return new IfOp(x, cond, y, tval, fval);
aoqi@0:   }
aoqi@0: 
aoqi@0:   tval = tval->subst();
aoqi@0:   fval = fval->subst();
aoqi@0:   if (tval == fval) {
aoqi@0:     _ifop_count++;
aoqi@0:     return tval;
aoqi@0:   }
aoqi@0: 
aoqi@0:   x = x->subst();
aoqi@0:   y = y->subst();
aoqi@0: 
aoqi@0:   Constant* y_const = y->as_Constant();
aoqi@0:   if (y_const != NULL) {
aoqi@0:     IfOp* x_ifop = x->as_IfOp();
aoqi@0:     if (x_ifop != NULL) {                 // x is an ifop, y is a constant
aoqi@0:       Constant* x_tval_const = x_ifop->tval()->subst()->as_Constant();
aoqi@0:       Constant* x_fval_const = x_ifop->fval()->subst()->as_Constant();
aoqi@0: 
aoqi@0:       if (x_tval_const != NULL && x_fval_const != NULL) {
aoqi@0:         Instruction::Condition x_ifop_cond = x_ifop->cond();
aoqi@0: 
aoqi@0:         Constant::CompareResult t_compare_res = x_tval_const->compare(cond, y_const);
aoqi@0:         Constant::CompareResult f_compare_res = x_fval_const->compare(cond, y_const);
aoqi@0: 
aoqi@0:         // not_comparable here is a valid return in case we're comparing unloaded oop constants
aoqi@0:         if (t_compare_res != Constant::not_comparable && f_compare_res != Constant::not_comparable) {
aoqi@0:           Value new_tval = t_compare_res == Constant::cond_true ? tval : fval;
aoqi@0:           Value new_fval = f_compare_res == Constant::cond_true ? tval : fval;
aoqi@0: 
aoqi@0:           _ifop_count++;
aoqi@0:           if (new_tval == new_fval) {
aoqi@0:             return new_tval;
aoqi@0:           } else {
aoqi@0:             return new IfOp(x_ifop->x(), x_ifop_cond, x_ifop->y(), new_tval, new_fval);
aoqi@0:           }
aoqi@0:         }
aoqi@0:       }
aoqi@0:     } else {
aoqi@0:       Constant* x_const = x->as_Constant();
aoqi@0:       if (x_const != NULL) {         // x and y are constants
aoqi@0:         Constant::CompareResult x_compare_res = x_const->compare(cond, y_const);
aoqi@0:         // not_comparable here is a valid return in case we're comparing unloaded oop constants
aoqi@0:         if (x_compare_res != Constant::not_comparable) {
aoqi@0:           _ifop_count++;
aoqi@0:           return x_compare_res == Constant::cond_true ? tval : fval;
aoqi@0:         }
aoqi@0:       }
aoqi@0:     }
aoqi@0:   }
aoqi@0:   return new IfOp(x, cond, y, tval, fval);
aoqi@0: }
aoqi@0: 
aoqi@0: void Optimizer::eliminate_conditional_expressions() {
aoqi@0:   // find conditional expressions & replace them with IfOps
aoqi@0:   CE_Eliminator ce(ir());
aoqi@0: }
aoqi@0: 
aoqi@0: class BlockMerger: public BlockClosure {
aoqi@0:  private:
aoqi@0:   IR* _hir;
aoqi@0:   int _merge_count;              // the number of block pairs successfully merged
aoqi@0: 
aoqi@0:  public:
aoqi@0:   BlockMerger(IR* hir)
aoqi@0:   : _hir(hir)
aoqi@0:   , _merge_count(0)
aoqi@0:   {
aoqi@0:     _hir->iterate_preorder(this);
aoqi@0:     CompileLog* log = _hir->compilation()->log();
aoqi@0:     if (log != NULL)
aoqi@0:       log->set_context("optimize name='eliminate_blocks'");
aoqi@0:   }
aoqi@0: 
aoqi@0:   ~BlockMerger() {
aoqi@0:     CompileLog* log = _hir->compilation()->log();
aoqi@0:     if (log != NULL)
aoqi@0:       log->clear_context(); // skip marker if nothing was printed
aoqi@0:   }
aoqi@0: 
aoqi@0:   bool try_merge(BlockBegin* block) {
aoqi@0:     BlockEnd* end = block->end();
aoqi@0:     if (end->as_Goto() != NULL) {
aoqi@0:       assert(end->number_of_sux() == 1, "end must have exactly one successor");
aoqi@0:       // Note: It would be sufficient to check for the number of successors (= 1)
aoqi@0:       //       in order to decide if this block can be merged potentially. That
aoqi@0:       //       would then also include switch statements w/ only a default case.
aoqi@0:       //       However, in that case we would need to make sure the switch tag
aoqi@0:       //       expression is executed if it can produce observable side effects.
aoqi@0:       //       We should probably have the canonicalizer simplifying such switch
aoqi@0:       //       statements and then we are sure we don't miss these merge opportunities
aoqi@0:       //       here (was bug - gri 7/7/99).
aoqi@0:       BlockBegin* sux = end->default_sux();
aoqi@0:       if (sux->number_of_preds() == 1 && !sux->is_entry_block() && !end->is_safepoint()) {
aoqi@0:         // merge the two blocks
aoqi@0: 
aoqi@0: #ifdef ASSERT
aoqi@0:         // verify that state at the end of block and at the beginning of sux are equal
aoqi@0:         // no phi functions must be present at beginning of sux
aoqi@0:         ValueStack* sux_state = sux->state();
aoqi@0:         ValueStack* end_state = end->state();
aoqi@0: 
aoqi@0:         assert(end_state->scope() == sux_state->scope(), "scopes must match");
aoqi@0:         assert(end_state->stack_size() == sux_state->stack_size(), "stack not equal");
aoqi@0:         assert(end_state->locals_size() == sux_state->locals_size(), "locals not equal");
aoqi@0: 
aoqi@0:         int index;
aoqi@0:         Value sux_value;
aoqi@0:         for_each_stack_value(sux_state, index, sux_value) {
aoqi@0:           assert(sux_value == end_state->stack_at(index), "stack not equal");
aoqi@0:         }
aoqi@0:         for_each_local_value(sux_state, index, sux_value) {
aoqi@0:           assert(sux_value == end_state->local_at(index), "locals not equal");
aoqi@0:         }
aoqi@0:         assert(sux_state->caller_state() == end_state->caller_state(), "caller not equal");
aoqi@0: #endif
aoqi@0: 
aoqi@0:         // find instruction before end & append first instruction of sux block
aoqi@0:         Instruction* prev = end->prev();
aoqi@0:         Instruction* next = sux->next();
aoqi@0:         assert(prev->as_BlockEnd() == NULL, "must not be a BlockEnd");
aoqi@0:         prev->set_next(next);
aoqi@0:         prev->fixup_block_pointers();
aoqi@0:         sux->disconnect_from_graph();
aoqi@0:         block->set_end(sux->end());
aoqi@0:         // add exception handlers of deleted block, if any
aoqi@0:         for (int k = 0; k < sux->number_of_exception_handlers(); k++) {
aoqi@0:           BlockBegin* xhandler = sux->exception_handler_at(k);
aoqi@0:           block->add_exception_handler(xhandler);
aoqi@0: 
aoqi@0:           // also substitute predecessor of exception handler
aoqi@0:           assert(xhandler->is_predecessor(sux), "missing predecessor");
aoqi@0:           xhandler->remove_predecessor(sux);
aoqi@0:           if (!xhandler->is_predecessor(block)) {
aoqi@0:             xhandler->add_predecessor(block);
aoqi@0:           }
aoqi@0:         }
aoqi@0: 
aoqi@0:         // debugging output
aoqi@0:         _merge_count++;
aoqi@0:         if (PrintBlockElimination) {
aoqi@0:           tty->print_cr("%d. merged B%d & B%d (stack size = %d)",
aoqi@0:                         _merge_count, block->block_id(), sux->block_id(), sux->state()->stack_size());
aoqi@0:         }
aoqi@0: 
aoqi@0:         _hir->verify();
aoqi@0: 
aoqi@0:         If* if_ = block->end()->as_If();
aoqi@0:         if (if_) {
aoqi@0:           IfOp* ifop    = if_->x()->as_IfOp();
aoqi@0:           Constant* con = if_->y()->as_Constant();
aoqi@0:           bool swapped = false;
aoqi@0:           if (!con || !ifop) {
aoqi@0:             ifop = if_->y()->as_IfOp();
aoqi@0:             con  = if_->x()->as_Constant();
aoqi@0:             swapped = true;
aoqi@0:           }
aoqi@0:           if (con && ifop) {
aoqi@0:             Constant* tval = ifop->tval()->as_Constant();
aoqi@0:             Constant* fval = ifop->fval()->as_Constant();
aoqi@0:             if (tval && fval) {
aoqi@0:               // Find the instruction before if_, starting with ifop.
aoqi@0:               // When if_ and ifop are not in the same block, prev
aoqi@0:               // becomes NULL In such (rare) cases it is not
aoqi@0:               // profitable to perform the optimization.
aoqi@0:               Value prev = ifop;
aoqi@0:               while (prev != NULL && prev->next() != if_) {
aoqi@0:                 prev = prev->next();
aoqi@0:               }
aoqi@0: 
aoqi@0:               if (prev != NULL) {
aoqi@0:                 Instruction::Condition cond = if_->cond();
aoqi@0:                 BlockBegin* tsux = if_->tsux();
aoqi@0:                 BlockBegin* fsux = if_->fsux();
aoqi@0:                 if (swapped) {
aoqi@0:                   cond = Instruction::mirror(cond);
aoqi@0:                 }
aoqi@0: 
aoqi@0:                 BlockBegin* tblock = tval->compare(cond, con, tsux, fsux);
aoqi@0:                 BlockBegin* fblock = fval->compare(cond, con, tsux, fsux);
aoqi@0:                 if (tblock != fblock && !if_->is_safepoint()) {
aoqi@0:                   If* newif = new If(ifop->x(), ifop->cond(), false, ifop->y(),
aoqi@0:                                      tblock, fblock, if_->state_before(), if_->is_safepoint());
aoqi@0:                   newif->set_state(if_->state()->copy());
aoqi@0: 
aoqi@0:                   assert(prev->next() == if_, "must be guaranteed by above search");
aoqi@0:                   NOT_PRODUCT(newif->set_printable_bci(if_->printable_bci()));
aoqi@0:                   prev->set_next(newif);
aoqi@0:                   block->set_end(newif);
aoqi@0: 
aoqi@0:                   _merge_count++;
aoqi@0:                   if (PrintBlockElimination) {
aoqi@0:                     tty->print_cr("%d. replaced If and IfOp at end of B%d with single If", _merge_count, block->block_id());
aoqi@0:                   }
aoqi@0: 
aoqi@0:                   _hir->verify();
aoqi@0:                 }
aoqi@0:               }
aoqi@0:             }
aoqi@0:           }
aoqi@0:         }
aoqi@0: 
aoqi@0:         return true;
aoqi@0:       }
aoqi@0:     }
aoqi@0:     return false;
aoqi@0:   }
aoqi@0: 
aoqi@0:   virtual void block_do(BlockBegin* block) {
aoqi@0:     _hir->verify();
aoqi@0:     // repeat since the same block may merge again
aoqi@0:     while (try_merge(block)) {
aoqi@0:       _hir->verify();
aoqi@0:     }
aoqi@0:   }
aoqi@0: };
aoqi@0: 
aoqi@0: 
aoqi@0: void Optimizer::eliminate_blocks() {
aoqi@0:   // merge blocks if possible
aoqi@0:   BlockMerger bm(ir());
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: class NullCheckEliminator;
aoqi@0: class NullCheckVisitor: public InstructionVisitor {
aoqi@0: private:
aoqi@0:   NullCheckEliminator* _nce;
aoqi@0:   NullCheckEliminator* nce() { return _nce; }
aoqi@0: 
aoqi@0: public:
aoqi@0:   NullCheckVisitor() {}
aoqi@0: 
aoqi@0:   void set_eliminator(NullCheckEliminator* nce) { _nce = nce; }
aoqi@0: 
aoqi@0:   void do_Phi            (Phi*             x);
aoqi@0:   void do_Local          (Local*           x);
aoqi@0:   void do_Constant       (Constant*        x);
aoqi@0:   void do_LoadField      (LoadField*       x);
aoqi@0:   void do_StoreField     (StoreField*      x);
aoqi@0:   void do_ArrayLength    (ArrayLength*     x);
aoqi@0:   void do_LoadIndexed    (LoadIndexed*     x);
aoqi@0:   void do_StoreIndexed   (StoreIndexed*    x);
aoqi@0:   void do_NegateOp       (NegateOp*        x);
aoqi@0:   void do_ArithmeticOp   (ArithmeticOp*    x);
aoqi@0:   void do_ShiftOp        (ShiftOp*         x);
aoqi@0:   void do_LogicOp        (LogicOp*         x);
aoqi@0:   void do_CompareOp      (CompareOp*       x);
aoqi@0:   void do_IfOp           (IfOp*            x);
aoqi@0:   void do_Convert        (Convert*         x);
aoqi@0:   void do_NullCheck      (NullCheck*       x);
aoqi@0:   void do_TypeCast       (TypeCast*        x);
aoqi@0:   void do_Invoke         (Invoke*          x);
aoqi@0:   void do_NewInstance    (NewInstance*     x);
aoqi@0:   void do_NewTypeArray   (NewTypeArray*    x);
aoqi@0:   void do_NewObjectArray (NewObjectArray*  x);
aoqi@0:   void do_NewMultiArray  (NewMultiArray*   x);
aoqi@0:   void do_CheckCast      (CheckCast*       x);
aoqi@0:   void do_InstanceOf     (InstanceOf*      x);
aoqi@0:   void do_MonitorEnter   (MonitorEnter*    x);
aoqi@0:   void do_MonitorExit    (MonitorExit*     x);
aoqi@0:   void do_Intrinsic      (Intrinsic*       x);
aoqi@0:   void do_BlockBegin     (BlockBegin*      x);
aoqi@0:   void do_Goto           (Goto*            x);
aoqi@0:   void do_If             (If*              x);
aoqi@0:   void do_IfInstanceOf   (IfInstanceOf*    x);
aoqi@0:   void do_TableSwitch    (TableSwitch*     x);
aoqi@0:   void do_LookupSwitch   (LookupSwitch*    x);
aoqi@0:   void do_Return         (Return*          x);
aoqi@0:   void do_Throw          (Throw*           x);
aoqi@0:   void do_Base           (Base*            x);
aoqi@0:   void do_OsrEntry       (OsrEntry*        x);
aoqi@0:   void do_ExceptionObject(ExceptionObject* x);
aoqi@0:   void do_RoundFP        (RoundFP*         x);
aoqi@0:   void do_UnsafeGetRaw   (UnsafeGetRaw*    x);
aoqi@0:   void do_UnsafePutRaw   (UnsafePutRaw*    x);
aoqi@0:   void do_UnsafeGetObject(UnsafeGetObject* x);
aoqi@0:   void do_UnsafePutObject(UnsafePutObject* x);
aoqi@0:   void do_UnsafeGetAndSetObject(UnsafeGetAndSetObject* x);
aoqi@0:   void do_UnsafePrefetchRead (UnsafePrefetchRead*  x);
aoqi@0:   void do_UnsafePrefetchWrite(UnsafePrefetchWrite* x);
aoqi@0:   void do_ProfileCall    (ProfileCall*     x);
aoqi@0:   void do_ProfileReturnType (ProfileReturnType*  x);
aoqi@0:   void do_ProfileInvoke  (ProfileInvoke*   x);
aoqi@0:   void do_RuntimeCall    (RuntimeCall*     x);
aoqi@0:   void do_MemBar         (MemBar*          x);
aoqi@0:   void do_RangeCheckPredicate(RangeCheckPredicate* x);
aoqi@0: #ifdef ASSERT
aoqi@0:   void do_Assert         (Assert*          x);
aoqi@0: #endif
aoqi@0: };
aoqi@0: 
aoqi@0: 
aoqi@0: // Because of a static contained within (for the purpose of iteration
aoqi@0: // over instructions), it is only valid to have one of these active at
aoqi@0: // a time
aoqi@0: class NullCheckEliminator: public ValueVisitor {
aoqi@0:  private:
aoqi@0:   Optimizer*        _opt;
aoqi@0: 
aoqi@0:   ValueSet*         _visitable_instructions;        // Visit each instruction only once per basic block
aoqi@0:   BlockList*        _work_list;                   // Basic blocks to visit
aoqi@0: 
aoqi@0:   bool visitable(Value x) {
aoqi@0:     assert(_visitable_instructions != NULL, "check");
aoqi@0:     return _visitable_instructions->contains(x);
aoqi@0:   }
aoqi@0:   void mark_visited(Value x) {
aoqi@0:     assert(_visitable_instructions != NULL, "check");
aoqi@0:     _visitable_instructions->remove(x);
aoqi@0:   }
aoqi@0:   void mark_visitable(Value x) {
aoqi@0:     assert(_visitable_instructions != NULL, "check");
aoqi@0:     _visitable_instructions->put(x);
aoqi@0:   }
aoqi@0:   void clear_visitable_state() {
aoqi@0:     assert(_visitable_instructions != NULL, "check");
aoqi@0:     _visitable_instructions->clear();
aoqi@0:   }
aoqi@0: 
aoqi@0:   ValueSet*         _set;                         // current state, propagated to subsequent BlockBegins
aoqi@0:   ValueSetList      _block_states;                // BlockBegin null-check states for all processed blocks
aoqi@0:   NullCheckVisitor  _visitor;
aoqi@0:   NullCheck*        _last_explicit_null_check;
aoqi@0: 
aoqi@0:   bool set_contains(Value x)                      { assert(_set != NULL, "check"); return _set->contains(x); }
aoqi@0:   void set_put     (Value x)                      { assert(_set != NULL, "check"); _set->put(x); }
aoqi@0:   void set_remove  (Value x)                      { assert(_set != NULL, "check"); _set->remove(x); }
aoqi@0: 
aoqi@0:   BlockList* work_list()                          { return _work_list; }
aoqi@0: 
aoqi@0:   void iterate_all();
aoqi@0:   void iterate_one(BlockBegin* block);
aoqi@0: 
aoqi@0:   ValueSet* state()                               { return _set; }
aoqi@0:   void      set_state_from (ValueSet* state)      { _set->set_from(state); }
aoqi@0:   ValueSet* state_for      (BlockBegin* block)    { return _block_states[block->block_id()]; }
aoqi@0:   void      set_state_for  (BlockBegin* block, ValueSet* stack) { _block_states[block->block_id()] = stack; }
aoqi@0:   // Returns true if caused a change in the block's state.
aoqi@0:   bool      merge_state_for(BlockBegin* block,
aoqi@0:                             ValueSet*   incoming_state);
aoqi@0: 
aoqi@0:  public:
aoqi@0:   // constructor
aoqi@0:   NullCheckEliminator(Optimizer* opt)
aoqi@0:     : _opt(opt)
aoqi@0:     , _set(new ValueSet())
aoqi@0:     , _last_explicit_null_check(NULL)
aoqi@0:     , _block_states(BlockBegin::number_of_blocks(), NULL)
aoqi@0:     , _work_list(new BlockList()) {
aoqi@0:     _visitable_instructions = new ValueSet();
aoqi@0:     _visitor.set_eliminator(this);
aoqi@0:     CompileLog* log = _opt->ir()->compilation()->log();
aoqi@0:     if (log != NULL)
aoqi@0:       log->set_context("optimize name='null_check_elimination'");
aoqi@0:   }
aoqi@0: 
aoqi@0:   ~NullCheckEliminator() {
aoqi@0:     CompileLog* log = _opt->ir()->compilation()->log();
aoqi@0:     if (log != NULL)
aoqi@0:       log->clear_context(); // skip marker if nothing was printed
aoqi@0:   }
aoqi@0: 
aoqi@0:   Optimizer*  opt()                               { return _opt; }
aoqi@0:   IR*         ir ()                               { return opt()->ir(); }
aoqi@0: 
aoqi@0:   // Process a graph
aoqi@0:   void iterate(BlockBegin* root);
aoqi@0: 
aoqi@0:   void visit(Value* f);
aoqi@0: 
aoqi@0:   // In some situations (like NullCheck(x); getfield(x)) the debug
aoqi@0:   // information from the explicit NullCheck can be used to populate
aoqi@0:   // the getfield, even if the two instructions are in different
aoqi@0:   // scopes; this allows implicit null checks to be used but the
aoqi@0:   // correct exception information to be generated. We must clear the
aoqi@0:   // last-traversed NullCheck when we reach a potentially-exception-
aoqi@0:   // throwing instruction, as well as in some other cases.
aoqi@0:   void        set_last_explicit_null_check(NullCheck* check) { _last_explicit_null_check = check; }
aoqi@0:   NullCheck*  last_explicit_null_check()                     { return _last_explicit_null_check; }
aoqi@0:   Value       last_explicit_null_check_obj()                 { return (_last_explicit_null_check
aoqi@0:                                                                          ? _last_explicit_null_check->obj()
aoqi@0:                                                                          : NULL); }
aoqi@0:   NullCheck*  consume_last_explicit_null_check() {
aoqi@0:     _last_explicit_null_check->unpin(Instruction::PinExplicitNullCheck);
aoqi@0:     _last_explicit_null_check->set_can_trap(false);
aoqi@0:     return _last_explicit_null_check;
aoqi@0:   }
aoqi@0:   void        clear_last_explicit_null_check()               { _last_explicit_null_check = NULL; }
aoqi@0: 
aoqi@0:   // Handlers for relevant instructions
aoqi@0:   // (separated out from NullCheckVisitor for clarity)
aoqi@0: 
aoqi@0:   // The basic contract is that these must leave the instruction in
aoqi@0:   // the desired state; must not assume anything about the state of
aoqi@0:   // the instruction. We make multiple passes over some basic blocks
aoqi@0:   // and the last pass is the only one whose result is valid.
aoqi@0:   void handle_AccessField     (AccessField* x);
aoqi@0:   void handle_ArrayLength     (ArrayLength* x);
aoqi@0:   void handle_LoadIndexed     (LoadIndexed* x);
aoqi@0:   void handle_StoreIndexed    (StoreIndexed* x);
aoqi@0:   void handle_NullCheck       (NullCheck* x);
aoqi@0:   void handle_Invoke          (Invoke* x);
aoqi@0:   void handle_NewInstance     (NewInstance* x);
aoqi@0:   void handle_NewArray        (NewArray* x);
aoqi@0:   void handle_AccessMonitor   (AccessMonitor* x);
aoqi@0:   void handle_Intrinsic       (Intrinsic* x);
aoqi@0:   void handle_ExceptionObject (ExceptionObject* x);
aoqi@0:   void handle_Phi             (Phi* x);
aoqi@0:   void handle_ProfileCall     (ProfileCall* x);
aoqi@0:   void handle_ProfileReturnType (ProfileReturnType* x);
aoqi@0: };
aoqi@0: 
aoqi@0: 
aoqi@0: // NEEDS_CLEANUP
aoqi@0: // There may be other instructions which need to clear the last
aoqi@0: // explicit null check. Anything across which we can not hoist the
aoqi@0: // debug information for a NullCheck instruction must clear it. It
aoqi@0: // might be safer to pattern match "NullCheck ; {AccessField,
aoqi@0: // ArrayLength, LoadIndexed}" but it is more easily structured this way.
aoqi@0: // Should test to see performance hit of clearing it for all handlers
aoqi@0: // with empty bodies below. If it is negligible then we should leave
aoqi@0: // that in for safety, otherwise should think more about it.
aoqi@0: void NullCheckVisitor::do_Phi            (Phi*             x) { nce()->handle_Phi(x);      }
aoqi@0: void NullCheckVisitor::do_Local          (Local*           x) {}
aoqi@0: void NullCheckVisitor::do_Constant       (Constant*        x) { /* FIXME: handle object constants */ }
aoqi@0: void NullCheckVisitor::do_LoadField      (LoadField*       x) { nce()->handle_AccessField(x); }
aoqi@0: void NullCheckVisitor::do_StoreField     (StoreField*      x) { nce()->handle_AccessField(x); }
aoqi@0: void NullCheckVisitor::do_ArrayLength    (ArrayLength*     x) { nce()->handle_ArrayLength(x); }
aoqi@0: void NullCheckVisitor::do_LoadIndexed    (LoadIndexed*     x) { nce()->handle_LoadIndexed(x); }
aoqi@0: void NullCheckVisitor::do_StoreIndexed   (StoreIndexed*    x) { nce()->handle_StoreIndexed(x); }
aoqi@0: void NullCheckVisitor::do_NegateOp       (NegateOp*        x) {}
aoqi@0: void NullCheckVisitor::do_ArithmeticOp   (ArithmeticOp*    x) { if (x->can_trap()) nce()->clear_last_explicit_null_check(); }
aoqi@0: void NullCheckVisitor::do_ShiftOp        (ShiftOp*         x) {}
aoqi@0: void NullCheckVisitor::do_LogicOp        (LogicOp*         x) {}
aoqi@0: void NullCheckVisitor::do_CompareOp      (CompareOp*       x) {}
aoqi@0: void NullCheckVisitor::do_IfOp           (IfOp*            x) {}
aoqi@0: void NullCheckVisitor::do_Convert        (Convert*         x) {}
aoqi@0: void NullCheckVisitor::do_NullCheck      (NullCheck*       x) { nce()->handle_NullCheck(x); }
aoqi@0: void NullCheckVisitor::do_TypeCast       (TypeCast*        x) {}
aoqi@0: void NullCheckVisitor::do_Invoke         (Invoke*          x) { nce()->handle_Invoke(x); }
aoqi@0: void NullCheckVisitor::do_NewInstance    (NewInstance*     x) { nce()->handle_NewInstance(x); }
aoqi@0: void NullCheckVisitor::do_NewTypeArray   (NewTypeArray*    x) { nce()->handle_NewArray(x); }
aoqi@0: void NullCheckVisitor::do_NewObjectArray (NewObjectArray*  x) { nce()->handle_NewArray(x); }
aoqi@0: void NullCheckVisitor::do_NewMultiArray  (NewMultiArray*   x) { nce()->handle_NewArray(x); }
aoqi@0: void NullCheckVisitor::do_CheckCast      (CheckCast*       x) { nce()->clear_last_explicit_null_check(); }
aoqi@0: void NullCheckVisitor::do_InstanceOf     (InstanceOf*      x) {}
aoqi@0: void NullCheckVisitor::do_MonitorEnter   (MonitorEnter*    x) { nce()->handle_AccessMonitor(x); }
aoqi@0: void NullCheckVisitor::do_MonitorExit    (MonitorExit*     x) { nce()->handle_AccessMonitor(x); }
aoqi@0: void NullCheckVisitor::do_Intrinsic      (Intrinsic*       x) { nce()->handle_Intrinsic(x);     }
aoqi@0: void NullCheckVisitor::do_BlockBegin     (BlockBegin*      x) {}
aoqi@0: void NullCheckVisitor::do_Goto           (Goto*            x) {}
aoqi@0: void NullCheckVisitor::do_If             (If*              x) {}
aoqi@0: void NullCheckVisitor::do_IfInstanceOf   (IfInstanceOf*    x) {}
aoqi@0: void NullCheckVisitor::do_TableSwitch    (TableSwitch*     x) {}
aoqi@0: void NullCheckVisitor::do_LookupSwitch   (LookupSwitch*    x) {}
aoqi@0: void NullCheckVisitor::do_Return         (Return*          x) {}
aoqi@0: void NullCheckVisitor::do_Throw          (Throw*           x) { nce()->clear_last_explicit_null_check(); }
aoqi@0: void NullCheckVisitor::do_Base           (Base*            x) {}
aoqi@0: void NullCheckVisitor::do_OsrEntry       (OsrEntry*        x) {}
aoqi@0: void NullCheckVisitor::do_ExceptionObject(ExceptionObject* x) { nce()->handle_ExceptionObject(x); }
aoqi@0: void NullCheckVisitor::do_RoundFP        (RoundFP*         x) {}
aoqi@0: void NullCheckVisitor::do_UnsafeGetRaw   (UnsafeGetRaw*    x) {}
aoqi@0: void NullCheckVisitor::do_UnsafePutRaw   (UnsafePutRaw*    x) {}
aoqi@0: void NullCheckVisitor::do_UnsafeGetObject(UnsafeGetObject* x) {}
aoqi@0: void NullCheckVisitor::do_UnsafePutObject(UnsafePutObject* x) {}
aoqi@0: void NullCheckVisitor::do_UnsafeGetAndSetObject(UnsafeGetAndSetObject* x) {}
aoqi@0: void NullCheckVisitor::do_UnsafePrefetchRead (UnsafePrefetchRead*  x) {}
aoqi@0: void NullCheckVisitor::do_UnsafePrefetchWrite(UnsafePrefetchWrite* x) {}
aoqi@0: void NullCheckVisitor::do_ProfileCall    (ProfileCall*     x) { nce()->clear_last_explicit_null_check();
aoqi@0:                                                                 nce()->handle_ProfileCall(x); }
aoqi@0: void NullCheckVisitor::do_ProfileReturnType (ProfileReturnType* x) { nce()->handle_ProfileReturnType(x); }
aoqi@0: void NullCheckVisitor::do_ProfileInvoke  (ProfileInvoke*   x) {}
aoqi@0: void NullCheckVisitor::do_RuntimeCall    (RuntimeCall*     x) {}
aoqi@0: void NullCheckVisitor::do_MemBar         (MemBar*          x) {}
aoqi@0: void NullCheckVisitor::do_RangeCheckPredicate(RangeCheckPredicate* x) {}
aoqi@0: #ifdef ASSERT
aoqi@0: void NullCheckVisitor::do_Assert         (Assert*          x) {}
aoqi@0: #endif
aoqi@0: 
aoqi@0: void NullCheckEliminator::visit(Value* p) {
aoqi@0:   assert(*p != NULL, "should not find NULL instructions");
aoqi@0:   if (visitable(*p)) {
aoqi@0:     mark_visited(*p);
aoqi@0:     (*p)->visit(&_visitor);
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: bool NullCheckEliminator::merge_state_for(BlockBegin* block, ValueSet* incoming_state) {
aoqi@0:   ValueSet* state = state_for(block);
aoqi@0:   if (state == NULL) {
aoqi@0:     state = incoming_state->copy();
aoqi@0:     set_state_for(block, state);
aoqi@0:     return true;
aoqi@0:   } else {
aoqi@0:     bool changed = state->set_intersect(incoming_state);
aoqi@0:     if (PrintNullCheckElimination && changed) {
aoqi@0:       tty->print_cr("Block %d's null check state changed", block->block_id());
aoqi@0:     }
aoqi@0:     return changed;
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: void NullCheckEliminator::iterate_all() {
aoqi@0:   while (work_list()->length() > 0) {
aoqi@0:     iterate_one(work_list()->pop());
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: void NullCheckEliminator::iterate_one(BlockBegin* block) {
aoqi@0:   clear_visitable_state();
aoqi@0:   // clear out an old explicit null checks
aoqi@0:   set_last_explicit_null_check(NULL);
aoqi@0: 
aoqi@0:   if (PrintNullCheckElimination) {
aoqi@0:     tty->print_cr(" ...iterating block %d in null check elimination for %s::%s%s",
aoqi@0:                   block->block_id(),
aoqi@0:                   ir()->method()->holder()->name()->as_utf8(),
aoqi@0:                   ir()->method()->name()->as_utf8(),
aoqi@0:                   ir()->method()->signature()->as_symbol()->as_utf8());
aoqi@0:   }
aoqi@0: 
aoqi@0:   // Create new state if none present (only happens at root)
aoqi@0:   if (state_for(block) == NULL) {
aoqi@0:     ValueSet* tmp_state = new ValueSet();
aoqi@0:     set_state_for(block, tmp_state);
aoqi@0:     // Initial state is that local 0 (receiver) is non-null for
aoqi@0:     // non-static methods
aoqi@0:     ValueStack* stack  = block->state();
aoqi@0:     IRScope*    scope  = stack->scope();
aoqi@0:     ciMethod*   method = scope->method();
aoqi@0:     if (!method->is_static()) {
aoqi@0:       Local* local0 = stack->local_at(0)->as_Local();
aoqi@0:       assert(local0 != NULL, "must be");
aoqi@0:       assert(local0->type() == objectType, "invalid type of receiver");
aoqi@0: 
aoqi@0:       if (local0 != NULL) {
aoqi@0:         // Local 0 is used in this scope
aoqi@0:         tmp_state->put(local0);
aoqi@0:         if (PrintNullCheckElimination) {
aoqi@0:           tty->print_cr("Local 0 (value %d) proven non-null upon entry", local0->id());
aoqi@0:         }
aoqi@0:       }
aoqi@0:     }
aoqi@0:   }
aoqi@0: 
aoqi@0:   // Must copy block's state to avoid mutating it during iteration
aoqi@0:   // through the block -- otherwise "not-null" states can accidentally
aoqi@0:   // propagate "up" through the block during processing of backward
aoqi@0:   // branches and algorithm is incorrect (and does not converge)
aoqi@0:   set_state_from(state_for(block));
aoqi@0: 
aoqi@0:   // allow visiting of Phis belonging to this block
aoqi@0:   for_each_phi_fun(block, phi,
aoqi@0:                    mark_visitable(phi);
aoqi@0:                    );
aoqi@0: 
aoqi@0:   BlockEnd* e = block->end();
aoqi@0:   assert(e != NULL, "incomplete graph");
aoqi@0:   int i;
aoqi@0: 
aoqi@0:   // Propagate the state before this block into the exception
aoqi@0:   // handlers.  They aren't true successors since we aren't guaranteed
aoqi@0:   // to execute the whole block before executing them.  Also putting
aoqi@0:   // them on first seems to help reduce the amount of iteration to
aoqi@0:   // reach a fixed point.
aoqi@0:   for (i = 0; i < block->number_of_exception_handlers(); i++) {
aoqi@0:     BlockBegin* next = block->exception_handler_at(i);
aoqi@0:     if (merge_state_for(next, state())) {
aoqi@0:       if (!work_list()->contains(next)) {
aoqi@0:         work_list()->push(next);
aoqi@0:       }
aoqi@0:     }
aoqi@0:   }
aoqi@0: 
aoqi@0:   // Iterate through block, updating state.
aoqi@0:   for (Instruction* instr = block; instr != NULL; instr = instr->next()) {
aoqi@0:     // Mark instructions in this block as visitable as they are seen
aoqi@0:     // in the instruction list.  This keeps the iteration from
aoqi@0:     // visiting instructions which are references in other blocks or
aoqi@0:     // visiting instructions more than once.
aoqi@0:     mark_visitable(instr);
aoqi@0:     if (instr->is_pinned() || instr->can_trap() || (instr->as_NullCheck() != NULL)) {
aoqi@0:       mark_visited(instr);
aoqi@0:       instr->input_values_do(this);
aoqi@0:       instr->visit(&_visitor);
aoqi@0:     }
aoqi@0:   }
aoqi@0: 
aoqi@0:   // Propagate state to successors if necessary
aoqi@0:   for (i = 0; i < e->number_of_sux(); i++) {
aoqi@0:     BlockBegin* next = e->sux_at(i);
aoqi@0:     if (merge_state_for(next, state())) {
aoqi@0:       if (!work_list()->contains(next)) {
aoqi@0:         work_list()->push(next);
aoqi@0:       }
aoqi@0:     }
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: void NullCheckEliminator::iterate(BlockBegin* block) {
aoqi@0:   work_list()->push(block);
aoqi@0:   iterate_all();
aoqi@0: }
aoqi@0: 
aoqi@0: void NullCheckEliminator::handle_AccessField(AccessField* x) {
aoqi@0:   if (x->is_static()) {
aoqi@0:     if (x->as_LoadField() != NULL) {
aoqi@0:       // If the field is a non-null static final object field (as is
aoqi@0:       // often the case for sun.misc.Unsafe), put this LoadField into
aoqi@0:       // the non-null map
aoqi@0:       ciField* field = x->field();
aoqi@0:       if (field->is_constant()) {
aoqi@0:         ciConstant field_val = field->constant_value();
aoqi@0:         BasicType field_type = field_val.basic_type();
aoqi@0:         if (field_type == T_OBJECT || field_type == T_ARRAY) {
aoqi@0:           ciObject* obj_val = field_val.as_object();
aoqi@0:           if (!obj_val->is_null_object()) {
aoqi@0:             if (PrintNullCheckElimination) {
aoqi@0:               tty->print_cr("AccessField %d proven non-null by static final non-null oop check",
aoqi@0:                             x->id());
aoqi@0:             }
aoqi@0:             set_put(x);
aoqi@0:           }
aoqi@0:         }
aoqi@0:       }
aoqi@0:     }
aoqi@0:     // Be conservative
aoqi@0:     clear_last_explicit_null_check();
aoqi@0:     return;
aoqi@0:   }
aoqi@0: 
aoqi@0:   Value obj = x->obj();
aoqi@0:   if (set_contains(obj)) {
aoqi@0:     // Value is non-null => update AccessField
aoqi@0:     if (last_explicit_null_check_obj() == obj && !x->needs_patching()) {
aoqi@0:       x->set_explicit_null_check(consume_last_explicit_null_check());
aoqi@0:       x->set_needs_null_check(true);
aoqi@0:       if (PrintNullCheckElimination) {
aoqi@0:         tty->print_cr("Folded NullCheck %d into AccessField %d's null check for value %d",
aoqi@0:                       x->explicit_null_check()->id(), x->id(), obj->id());
aoqi@0:       }
aoqi@0:     } else {
aoqi@0:       x->set_explicit_null_check(NULL);
aoqi@0:       x->set_needs_null_check(false);
aoqi@0:       if (PrintNullCheckElimination) {
aoqi@0:         tty->print_cr("Eliminated AccessField %d's null check for value %d", x->id(), obj->id());
aoqi@0:       }
aoqi@0:     }
aoqi@0:   } else {
aoqi@0:     set_put(obj);
aoqi@0:     if (PrintNullCheckElimination) {
aoqi@0:       tty->print_cr("AccessField %d of value %d proves value to be non-null", x->id(), obj->id());
aoqi@0:     }
aoqi@0:     // Ensure previous passes do not cause wrong state
aoqi@0:     x->set_needs_null_check(true);
aoqi@0:     x->set_explicit_null_check(NULL);
aoqi@0:   }
aoqi@0:   clear_last_explicit_null_check();
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: void NullCheckEliminator::handle_ArrayLength(ArrayLength* x) {
aoqi@0:   Value array = x->array();
aoqi@0:   if (set_contains(array)) {
aoqi@0:     // Value is non-null => update AccessArray
aoqi@0:     if (last_explicit_null_check_obj() == array) {
aoqi@0:       x->set_explicit_null_check(consume_last_explicit_null_check());
aoqi@0:       x->set_needs_null_check(true);
aoqi@0:       if (PrintNullCheckElimination) {
aoqi@0:         tty->print_cr("Folded NullCheck %d into ArrayLength %d's null check for value %d",
aoqi@0:                       x->explicit_null_check()->id(), x->id(), array->id());
aoqi@0:       }
aoqi@0:     } else {
aoqi@0:       x->set_explicit_null_check(NULL);
aoqi@0:       x->set_needs_null_check(false);
aoqi@0:       if (PrintNullCheckElimination) {
aoqi@0:         tty->print_cr("Eliminated ArrayLength %d's null check for value %d", x->id(), array->id());
aoqi@0:       }
aoqi@0:     }
aoqi@0:   } else {
aoqi@0:     set_put(array);
aoqi@0:     if (PrintNullCheckElimination) {
aoqi@0:       tty->print_cr("ArrayLength %d of value %d proves value to be non-null", x->id(), array->id());
aoqi@0:     }
aoqi@0:     // Ensure previous passes do not cause wrong state
aoqi@0:     x->set_needs_null_check(true);
aoqi@0:     x->set_explicit_null_check(NULL);
aoqi@0:   }
aoqi@0:   clear_last_explicit_null_check();
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: void NullCheckEliminator::handle_LoadIndexed(LoadIndexed* x) {
aoqi@0:   Value array = x->array();
aoqi@0:   if (set_contains(array)) {
aoqi@0:     // Value is non-null => update AccessArray
aoqi@0:     if (last_explicit_null_check_obj() == array) {
aoqi@0:       x->set_explicit_null_check(consume_last_explicit_null_check());
aoqi@0:       x->set_needs_null_check(true);
aoqi@0:       if (PrintNullCheckElimination) {
aoqi@0:         tty->print_cr("Folded NullCheck %d into LoadIndexed %d's null check for value %d",
aoqi@0:                       x->explicit_null_check()->id(), x->id(), array->id());
aoqi@0:       }
aoqi@0:     } else {
aoqi@0:       x->set_explicit_null_check(NULL);
aoqi@0:       x->set_needs_null_check(false);
aoqi@0:       if (PrintNullCheckElimination) {
aoqi@0:         tty->print_cr("Eliminated LoadIndexed %d's null check for value %d", x->id(), array->id());
aoqi@0:       }
aoqi@0:     }
aoqi@0:   } else {
aoqi@0:     set_put(array);
aoqi@0:     if (PrintNullCheckElimination) {
aoqi@0:       tty->print_cr("LoadIndexed %d of value %d proves value to be non-null", x->id(), array->id());
aoqi@0:     }
aoqi@0:     // Ensure previous passes do not cause wrong state
aoqi@0:     x->set_needs_null_check(true);
aoqi@0:     x->set_explicit_null_check(NULL);
aoqi@0:   }
aoqi@0:   clear_last_explicit_null_check();
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: void NullCheckEliminator::handle_StoreIndexed(StoreIndexed* x) {
aoqi@0:   Value array = x->array();
aoqi@0:   if (set_contains(array)) {
aoqi@0:     // Value is non-null => update AccessArray
aoqi@0:     if (PrintNullCheckElimination) {
aoqi@0:       tty->print_cr("Eliminated StoreIndexed %d's null check for value %d", x->id(), array->id());
aoqi@0:     }
aoqi@0:     x->set_needs_null_check(false);
aoqi@0:   } else {
aoqi@0:     set_put(array);
aoqi@0:     if (PrintNullCheckElimination) {
aoqi@0:       tty->print_cr("StoreIndexed %d of value %d proves value to be non-null", x->id(), array->id());
aoqi@0:     }
aoqi@0:     // Ensure previous passes do not cause wrong state
aoqi@0:     x->set_needs_null_check(true);
aoqi@0:   }
aoqi@0:   clear_last_explicit_null_check();
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: void NullCheckEliminator::handle_NullCheck(NullCheck* x) {
aoqi@0:   Value obj = x->obj();
aoqi@0:   if (set_contains(obj)) {
aoqi@0:     // Already proven to be non-null => this NullCheck is useless
aoqi@0:     if (PrintNullCheckElimination) {
aoqi@0:       tty->print_cr("Eliminated NullCheck %d for value %d", x->id(), obj->id());
aoqi@0:     }
aoqi@0:     // Don't unpin since that may shrink obj's live range and make it unavailable for debug info.
aoqi@0:     // The code generator won't emit LIR for a NullCheck that cannot trap.
aoqi@0:     x->set_can_trap(false);
aoqi@0:   } else {
aoqi@0:     // May be null => add to map and set last explicit NullCheck
aoqi@0:     x->set_can_trap(true);
aoqi@0:     // make sure it's pinned if it can trap
aoqi@0:     x->pin(Instruction::PinExplicitNullCheck);
aoqi@0:     set_put(obj);
aoqi@0:     set_last_explicit_null_check(x);
aoqi@0:     if (PrintNullCheckElimination) {
aoqi@0:       tty->print_cr("NullCheck %d of value %d proves value to be non-null", x->id(), obj->id());
aoqi@0:     }
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: void NullCheckEliminator::handle_Invoke(Invoke* x) {
aoqi@0:   if (!x->has_receiver()) {
aoqi@0:     // Be conservative
aoqi@0:     clear_last_explicit_null_check();
aoqi@0:     return;
aoqi@0:   }
aoqi@0: 
aoqi@0:   Value recv = x->receiver();
aoqi@0:   if (!set_contains(recv)) {
aoqi@0:     set_put(recv);
aoqi@0:     if (PrintNullCheckElimination) {
aoqi@0:       tty->print_cr("Invoke %d of value %d proves value to be non-null", x->id(), recv->id());
aoqi@0:     }
aoqi@0:   }
aoqi@0:   clear_last_explicit_null_check();
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: void NullCheckEliminator::handle_NewInstance(NewInstance* x) {
aoqi@0:   set_put(x);
aoqi@0:   if (PrintNullCheckElimination) {
aoqi@0:     tty->print_cr("NewInstance %d is non-null", x->id());
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: void NullCheckEliminator::handle_NewArray(NewArray* x) {
aoqi@0:   set_put(x);
aoqi@0:   if (PrintNullCheckElimination) {
aoqi@0:     tty->print_cr("NewArray %d is non-null", x->id());
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: void NullCheckEliminator::handle_ExceptionObject(ExceptionObject* x) {
aoqi@0:   set_put(x);
aoqi@0:   if (PrintNullCheckElimination) {
aoqi@0:     tty->print_cr("ExceptionObject %d is non-null", x->id());
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: void NullCheckEliminator::handle_AccessMonitor(AccessMonitor* x) {
aoqi@0:   Value obj = x->obj();
aoqi@0:   if (set_contains(obj)) {
aoqi@0:     // Value is non-null => update AccessMonitor
aoqi@0:     if (PrintNullCheckElimination) {
aoqi@0:       tty->print_cr("Eliminated AccessMonitor %d's null check for value %d", x->id(), obj->id());
aoqi@0:     }
aoqi@0:     x->set_needs_null_check(false);
aoqi@0:   } else {
aoqi@0:     set_put(obj);
aoqi@0:     if (PrintNullCheckElimination) {
aoqi@0:       tty->print_cr("AccessMonitor %d of value %d proves value to be non-null", x->id(), obj->id());
aoqi@0:     }
aoqi@0:     // Ensure previous passes do not cause wrong state
aoqi@0:     x->set_needs_null_check(true);
aoqi@0:   }
aoqi@0:   clear_last_explicit_null_check();
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: void NullCheckEliminator::handle_Intrinsic(Intrinsic* x) {
aoqi@0:   if (!x->has_receiver()) {
aoqi@0:     if (x->id() == vmIntrinsics::_arraycopy) {
aoqi@0:       for (int i = 0; i < x->number_of_arguments(); i++) {
aoqi@0:         x->set_arg_needs_null_check(i, !set_contains(x->argument_at(i)));
aoqi@0:       }
aoqi@0:     }
aoqi@0: 
aoqi@0:     // Be conservative
aoqi@0:     clear_last_explicit_null_check();
aoqi@0:     return;
aoqi@0:   }
aoqi@0: 
aoqi@0:   Value recv = x->receiver();
aoqi@0:   if (set_contains(recv)) {
aoqi@0:     // Value is non-null => update Intrinsic
aoqi@0:     if (PrintNullCheckElimination) {
aoqi@0:       tty->print_cr("Eliminated Intrinsic %d's null check for value %d", x->id(), recv->id());
aoqi@0:     }
aoqi@0:     x->set_needs_null_check(false);
aoqi@0:   } else {
aoqi@0:     set_put(recv);
aoqi@0:     if (PrintNullCheckElimination) {
aoqi@0:       tty->print_cr("Intrinsic %d of value %d proves value to be non-null", x->id(), recv->id());
aoqi@0:     }
aoqi@0:     // Ensure previous passes do not cause wrong state
aoqi@0:     x->set_needs_null_check(true);
aoqi@0:   }
aoqi@0:   clear_last_explicit_null_check();
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: void NullCheckEliminator::handle_Phi(Phi* x) {
aoqi@0:   int i;
aoqi@0:   bool all_non_null = true;
aoqi@0:   if (x->is_illegal()) {
aoqi@0:     all_non_null = false;
aoqi@0:   } else {
aoqi@0:     for (i = 0; i < x->operand_count(); i++) {
aoqi@0:       Value input = x->operand_at(i);
aoqi@0:       if (!set_contains(input)) {
aoqi@0:         all_non_null = false;
aoqi@0:       }
aoqi@0:     }
aoqi@0:   }
aoqi@0: 
aoqi@0:   if (all_non_null) {
aoqi@0:     // Value is non-null => update Phi
aoqi@0:     if (PrintNullCheckElimination) {
aoqi@0:       tty->print_cr("Eliminated Phi %d's null check for phifun because all inputs are non-null", x->id());
aoqi@0:     }
aoqi@0:     x->set_needs_null_check(false);
aoqi@0:   } else if (set_contains(x)) {
aoqi@0:     set_remove(x);
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: void NullCheckEliminator::handle_ProfileCall(ProfileCall* x) {
aoqi@0:   for (int i = 0; i < x->nb_profiled_args(); i++) {
aoqi@0:     x->set_arg_needs_null_check(i, !set_contains(x->profiled_arg_at(i)));
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: void NullCheckEliminator::handle_ProfileReturnType(ProfileReturnType* x) {
aoqi@0:   x->set_needs_null_check(!set_contains(x->ret()));
aoqi@0: }
aoqi@0: 
aoqi@0: void Optimizer::eliminate_null_checks() {
aoqi@0:   ResourceMark rm;
aoqi@0: 
aoqi@0:   NullCheckEliminator nce(this);
aoqi@0: 
aoqi@0:   if (PrintNullCheckElimination) {
aoqi@0:     tty->print_cr("Starting null check elimination for method %s::%s%s",
aoqi@0:                   ir()->method()->holder()->name()->as_utf8(),
aoqi@0:                   ir()->method()->name()->as_utf8(),
aoqi@0:                   ir()->method()->signature()->as_symbol()->as_utf8());
aoqi@0:   }
aoqi@0: 
aoqi@0:   // Apply to graph
aoqi@0:   nce.iterate(ir()->start());
aoqi@0: 
aoqi@0:   // walk over the graph looking for exception
aoqi@0:   // handlers and iterate over them as well
aoqi@0:   int nblocks = BlockBegin::number_of_blocks();
aoqi@0:   BlockList blocks(nblocks);
aoqi@0:   boolArray visited_block(nblocks, false);
aoqi@0: 
aoqi@0:   blocks.push(ir()->start());
aoqi@0:   visited_block[ir()->start()->block_id()] = true;
aoqi@0:   for (int i = 0; i < blocks.length(); i++) {
aoqi@0:     BlockBegin* b = blocks[i];
aoqi@0:     // exception handlers need to be treated as additional roots
aoqi@0:     for (int e = b->number_of_exception_handlers(); e-- > 0; ) {
aoqi@0:       BlockBegin* excp = b->exception_handler_at(e);
aoqi@0:       int id = excp->block_id();
aoqi@0:       if (!visited_block[id]) {
aoqi@0:         blocks.push(excp);
aoqi@0:         visited_block[id] = true;
aoqi@0:         nce.iterate(excp);
aoqi@0:       }
aoqi@0:     }
aoqi@0:     // traverse successors
aoqi@0:     BlockEnd *end = b->end();
aoqi@0:     for (int s = end->number_of_sux(); s-- > 0; ) {
aoqi@0:       BlockBegin* next = end->sux_at(s);
aoqi@0:       int id = next->block_id();
aoqi@0:       if (!visited_block[id]) {
aoqi@0:         blocks.push(next);
aoqi@0:         visited_block[id] = true;
aoqi@0:       }
aoqi@0:     }
aoqi@0:   }
aoqi@0: 
aoqi@0: 
aoqi@0:   if (PrintNullCheckElimination) {
aoqi@0:     tty->print_cr("Done with null check elimination for method %s::%s%s",
aoqi@0:                   ir()->method()->holder()->name()->as_utf8(),
aoqi@0:                   ir()->method()->name()->as_utf8(),
aoqi@0:                   ir()->method()->signature()->as_symbol()->as_utf8());
aoqi@0:   }
aoqi@0: }