duke@435: /*
xdono@1014:  * Copyright 1999-2009 Sun Microsystems, Inc.  All Rights Reserved.
duke@435:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@435:  *
duke@435:  * This code is free software; you can redistribute it and/or modify it
duke@435:  * under the terms of the GNU General Public License version 2 only, as
duke@435:  * published by the Free Software Foundation.
duke@435:  *
duke@435:  * This code is distributed in the hope that it will be useful, but WITHOUT
duke@435:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@435:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
duke@435:  * version 2 for more details (a copy is included in the LICENSE file that
duke@435:  * accompanied this code).
duke@435:  *
duke@435:  * You should have received a copy of the GNU General Public License version
duke@435:  * 2 along with this work; if not, write to the Free Software Foundation,
duke@435:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@435:  *
duke@435:  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
duke@435:  * CA 95054 USA or visit www.sun.com if you need additional information or
duke@435:  * have any questions.
duke@435:  *
duke@435:  */
duke@435: 
duke@435: #include "incls/_precompiled.incl"
duke@435: #include "incls/_c1_Optimizer.cpp.incl"
duke@435: 
duke@435: define_array(ValueSetArray, ValueSet*);
duke@435: define_stack(ValueSetList, ValueSetArray);
duke@435: 
duke@435: 
duke@435: Optimizer::Optimizer(IR* ir) {
duke@435:   assert(ir->is_valid(), "IR must be valid");
duke@435:   _ir = ir;
duke@435: }
duke@435: 
duke@435: class CE_Eliminator: public BlockClosure {
duke@435:  private:
duke@435:   IR* _hir;
duke@435:   int _cee_count;                                // the number of CEs successfully eliminated
duke@435:   int _has_substitution;
duke@435: 
duke@435:  public:
duke@435:   CE_Eliminator(IR* hir) : _cee_count(0), _hir(hir) {
duke@435:     _has_substitution = false;
duke@435:     _hir->iterate_preorder(this);
duke@435:     if (_has_substitution) {
duke@435:       // substituted some phis so resolve the substitution
duke@435:       SubstitutionResolver sr(_hir);
duke@435:     }
duke@435:   }
duke@435:   int cee_count() const                          { return _cee_count; }
duke@435: 
duke@435:   void adjust_exception_edges(BlockBegin* block, BlockBegin* sux) {
duke@435:     int e = sux->number_of_exception_handlers();
duke@435:     for (int i = 0; i < e; i++) {
duke@435:       BlockBegin* xhandler = sux->exception_handler_at(i);
duke@435:       block->add_exception_handler(xhandler);
duke@435: 
duke@435:       assert(xhandler->is_predecessor(sux), "missing predecessor");
duke@435:       if (sux->number_of_preds() == 0) {
duke@435:         // sux is disconnected from graph so disconnect from exception handlers
duke@435:         xhandler->remove_predecessor(sux);
duke@435:       }
duke@435:       if (!xhandler->is_predecessor(block)) {
duke@435:         xhandler->add_predecessor(block);
duke@435:       }
duke@435:     }
duke@435:   }
duke@435: 
duke@435:   virtual void block_do(BlockBegin* block) {
duke@435:     // 1) find conditional expression
duke@435:     // check if block ends with an If
duke@435:     If* if_ = block->end()->as_If();
duke@435:     if (if_ == NULL) return;
duke@435: 
duke@435:     // check if If works on int or object types
duke@435:     // (we cannot handle If's working on long, float or doubles yet,
duke@435:     // since IfOp doesn't support them - these If's show up if cmp
duke@435:     // operations followed by If's are eliminated)
duke@435:     ValueType* if_type = if_->x()->type();
duke@435:     if (!if_type->is_int() && !if_type->is_object()) return;
duke@435: 
duke@435:     BlockBegin* t_block = if_->tsux();
duke@435:     BlockBegin* f_block = if_->fsux();
duke@435:     Instruction* t_cur = t_block->next();
duke@435:     Instruction* f_cur = f_block->next();
duke@435: 
duke@435:     // one Constant may be present between BlockBegin and BlockEnd
duke@435:     Value t_const = NULL;
duke@435:     Value f_const = NULL;
duke@435:     if (t_cur->as_Constant() != NULL && !t_cur->can_trap()) {
duke@435:       t_const = t_cur;
duke@435:       t_cur = t_cur->next();
duke@435:     }
duke@435:     if (f_cur->as_Constant() != NULL && !f_cur->can_trap()) {
duke@435:       f_const = f_cur;
duke@435:       f_cur = f_cur->next();
duke@435:     }
duke@435: 
duke@435:     // check if both branches end with a goto
duke@435:     Goto* t_goto = t_cur->as_Goto();
duke@435:     if (t_goto == NULL) return;
duke@435:     Goto* f_goto = f_cur->as_Goto();
duke@435:     if (f_goto == NULL) return;
duke@435: 
duke@435:     // check if both gotos merge into the same block
duke@435:     BlockBegin* sux = t_goto->default_sux();
duke@435:     if (sux != f_goto->default_sux()) return;
duke@435: 
duke@435:     // check if at least one word was pushed on sux_state
duke@435:     ValueStack* sux_state = sux->state();
duke@435:     if (sux_state->stack_size() <= if_->state()->stack_size()) return;
duke@435: 
duke@435:     // check if phi function is present at end of successor stack and that
duke@435:     // only this phi was pushed on the stack
duke@435:     Value sux_phi = sux_state->stack_at(if_->state()->stack_size());
duke@435:     if (sux_phi == NULL || sux_phi->as_Phi() == NULL || sux_phi->as_Phi()->block() != sux) return;
duke@435:     if (sux_phi->type()->size() != sux_state->stack_size() - if_->state()->stack_size()) return;
duke@435: 
duke@435:     // get the values that were pushed in the true- and false-branch
duke@435:     Value t_value = t_goto->state()->stack_at(if_->state()->stack_size());
duke@435:     Value f_value = f_goto->state()->stack_at(if_->state()->stack_size());
duke@435: 
duke@435:     // backend does not support floats
duke@435:     assert(t_value->type()->base() == f_value->type()->base(), "incompatible types");
duke@435:     if (t_value->type()->is_float_kind()) return;
duke@435: 
duke@435:     // check that successor has no other phi functions but sux_phi
duke@435:     // this can happen when t_block or f_block contained additonal stores to local variables
duke@435:     // that are no longer represented by explicit instructions
duke@435:     for_each_phi_fun(sux, phi,
duke@435:                      if (phi != sux_phi) return;
duke@435:                      );
duke@435:     // true and false blocks can't have phis
duke@435:     for_each_phi_fun(t_block, phi, return; );
duke@435:     for_each_phi_fun(f_block, phi, return; );
duke@435: 
duke@435:     // 2) substitute conditional expression
duke@435:     //    with an IfOp followed by a Goto
duke@435:     // cut if_ away and get node before
duke@435:     Instruction* cur_end = if_->prev(block);
duke@435:     int bci = if_->bci();
duke@435: 
duke@435:     // append constants of true- and false-block if necessary
duke@435:     // clone constants because original block must not be destroyed
duke@435:     assert((t_value != f_const && f_value != t_const) || t_const == f_const, "mismatch");
duke@435:     if (t_value == t_const) {
duke@435:       t_value = new Constant(t_const->type());
duke@435:       cur_end = cur_end->set_next(t_value, bci);
duke@435:     }
duke@435:     if (f_value == f_const) {
duke@435:       f_value = new Constant(f_const->type());
duke@435:       cur_end = cur_end->set_next(f_value, bci);
duke@435:     }
duke@435: 
duke@435:     // it is very unlikely that the condition can be statically decided
duke@435:     // (this was checked previously by the Canonicalizer), so always
duke@435:     // append IfOp
duke@435:     Value result = new IfOp(if_->x(), if_->cond(), if_->y(), t_value, f_value);
duke@435:     cur_end = cur_end->set_next(result, bci);
duke@435: 
duke@435:     // append Goto to successor
duke@435:     ValueStack* state_before = if_->is_safepoint() ? if_->state_before() : NULL;
duke@435:     Goto* goto_ = new Goto(sux, state_before, if_->is_safepoint() || t_goto->is_safepoint() || f_goto->is_safepoint());
duke@435: 
duke@435:     // prepare state for Goto
duke@435:     ValueStack* goto_state = if_->state();
duke@435:     while (sux_state->scope() != goto_state->scope()) {
duke@435:       goto_state = goto_state->pop_scope();
duke@435:       assert(goto_state != NULL, "states do not match up");
duke@435:     }
duke@435:     goto_state = goto_state->copy();
duke@435:     goto_state->push(result->type(), result);
duke@435:     assert(goto_state->is_same_across_scopes(sux_state), "states must match now");
duke@435:     goto_->set_state(goto_state);
duke@435: 
duke@435:     // Steal the bci for the goto from the sux
duke@435:     cur_end = cur_end->set_next(goto_, sux->bci());
duke@435: 
duke@435:     // Adjust control flow graph
duke@435:     BlockBegin::disconnect_edge(block, t_block);
duke@435:     BlockBegin::disconnect_edge(block, f_block);
duke@435:     if (t_block->number_of_preds() == 0) {
duke@435:       BlockBegin::disconnect_edge(t_block, sux);
duke@435:     }
duke@435:     adjust_exception_edges(block, t_block);
duke@435:     if (f_block->number_of_preds() == 0) {
duke@435:       BlockBegin::disconnect_edge(f_block, sux);
duke@435:     }
duke@435:     adjust_exception_edges(block, f_block);
duke@435: 
duke@435:     // update block end
duke@435:     block->set_end(goto_);
duke@435: 
duke@435:     // substitute the phi if possible
duke@435:     if (sux_phi->as_Phi()->operand_count() == 1) {
duke@435:       assert(sux_phi->as_Phi()->operand_at(0) == result, "screwed up phi");
duke@435:       sux_phi->set_subst(result);
duke@435:       _has_substitution = true;
duke@435:     }
duke@435: 
duke@435:     // 3) successfully eliminated a conditional expression
duke@435:     _cee_count++;
duke@435:     if (PrintCEE) {
duke@435:       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());
duke@435:     }
duke@435: 
duke@435:     _hir->verify();
duke@435:   }
duke@435: };
duke@435: 
duke@435: 
duke@435: void Optimizer::eliminate_conditional_expressions() {
duke@435:   // find conditional expressions & replace them with IfOps
duke@435:   CE_Eliminator ce(ir());
duke@435: }
duke@435: 
duke@435: 
duke@435: class BlockMerger: public BlockClosure {
duke@435:  private:
duke@435:   IR* _hir;
duke@435:   int _merge_count;              // the number of block pairs successfully merged
duke@435: 
duke@435:  public:
duke@435:   BlockMerger(IR* hir)
duke@435:   : _hir(hir)
duke@435:   , _merge_count(0)
duke@435:   {
duke@435:     _hir->iterate_preorder(this);
duke@435:   }
duke@435: 
duke@435:   bool try_merge(BlockBegin* block) {
duke@435:     BlockEnd* end = block->end();
duke@435:     if (end->as_Goto() != NULL) {
duke@435:       assert(end->number_of_sux() == 1, "end must have exactly one successor");
duke@435:       // Note: It would be sufficient to check for the number of successors (= 1)
duke@435:       //       in order to decide if this block can be merged potentially. That
duke@435:       //       would then also include switch statements w/ only a default case.
duke@435:       //       However, in that case we would need to make sure the switch tag
duke@435:       //       expression is executed if it can produce observable side effects.
duke@435:       //       We should probably have the canonicalizer simplifying such switch
duke@435:       //       statements and then we are sure we don't miss these merge opportunities
duke@435:       //       here (was bug - gri 7/7/99).
duke@435:       BlockBegin* sux = end->default_sux();
duke@435:       if (sux->number_of_preds() == 1 && !sux->is_entry_block() && !end->is_safepoint()) {
duke@435:         // merge the two blocks
duke@435: 
duke@435: #ifdef ASSERT
duke@435:         // verify that state at the end of block and at the beginning of sux are equal
duke@435:         // no phi functions must be present at beginning of sux
duke@435:         ValueStack* sux_state = sux->state();
duke@435:         ValueStack* end_state = end->state();
duke@435:         while (end_state->scope() != sux_state->scope()) {
duke@435:           // match up inlining level
duke@435:           end_state = end_state->pop_scope();
duke@435:         }
duke@435:         assert(end_state->stack_size() == sux_state->stack_size(), "stack not equal");
duke@435:         assert(end_state->locals_size() == sux_state->locals_size(), "locals not equal");
duke@435: 
duke@435:         int index;
duke@435:         Value sux_value;
duke@435:         for_each_stack_value(sux_state, index, sux_value) {
duke@435:           assert(sux_value == end_state->stack_at(index), "stack not equal");
duke@435:         }
duke@435:         for_each_local_value(sux_state, index, sux_value) {
duke@435:           assert(sux_value == end_state->local_at(index), "locals not equal");
duke@435:         }
duke@435:         assert(sux_state->caller_state() == end_state->caller_state(), "caller not equal");
duke@435: #endif
duke@435: 
duke@435:         // find instruction before end & append first instruction of sux block
duke@435:         Instruction* prev = end->prev(block);
duke@435:         Instruction* next = sux->next();
duke@435:         assert(prev->as_BlockEnd() == NULL, "must not be a BlockEnd");
duke@435:         prev->set_next(next, next->bci());
duke@435:         sux->disconnect_from_graph();
duke@435:         block->set_end(sux->end());
duke@435:         // add exception handlers of deleted block, if any
duke@435:         for (int k = 0; k < sux->number_of_exception_handlers(); k++) {
duke@435:           BlockBegin* xhandler = sux->exception_handler_at(k);
duke@435:           block->add_exception_handler(xhandler);
duke@435: 
duke@435:           // also substitute predecessor of exception handler
duke@435:           assert(xhandler->is_predecessor(sux), "missing predecessor");
duke@435:           xhandler->remove_predecessor(sux);
duke@435:           if (!xhandler->is_predecessor(block)) {
duke@435:             xhandler->add_predecessor(block);
duke@435:           }
duke@435:         }
duke@435: 
duke@435:         // debugging output
duke@435:         _merge_count++;
duke@435:         if (PrintBlockElimination) {
duke@435:           tty->print_cr("%d. merged B%d & B%d (stack size = %d)",
duke@435:                         _merge_count, block->block_id(), sux->block_id(), sux->state()->stack_size());
duke@435:         }
duke@435: 
duke@435:         _hir->verify();
duke@435: 
duke@435:         If* if_ = block->end()->as_If();
duke@435:         if (if_) {
duke@435:           IfOp* ifop    = if_->x()->as_IfOp();
duke@435:           Constant* con = if_->y()->as_Constant();
duke@435:           bool swapped = false;
duke@435:           if (!con || !ifop) {
duke@435:             ifop = if_->y()->as_IfOp();
duke@435:             con  = if_->x()->as_Constant();
duke@435:             swapped = true;
duke@435:           }
duke@435:           if (con && ifop) {
duke@435:             Constant* tval = ifop->tval()->as_Constant();
duke@435:             Constant* fval = ifop->fval()->as_Constant();
duke@435:             if (tval && fval) {
duke@435:               // Find the instruction before if_, starting with ifop.
duke@435:               // When if_ and ifop are not in the same block, prev
duke@435:               // becomes NULL In such (rare) cases it is not
duke@435:               // profitable to perform the optimization.
duke@435:               Value prev = ifop;
duke@435:               while (prev != NULL && prev->next() != if_) {
duke@435:                 prev = prev->next();
duke@435:               }
duke@435: 
duke@435:               if (prev != NULL) {
duke@435:                 Instruction::Condition cond = if_->cond();
duke@435:                 BlockBegin* tsux = if_->tsux();
duke@435:                 BlockBegin* fsux = if_->fsux();
duke@435:                 if (swapped) {
duke@435:                   cond = Instruction::mirror(cond);
duke@435:                 }
duke@435: 
duke@435:                 BlockBegin* tblock = tval->compare(cond, con, tsux, fsux);
duke@435:                 BlockBegin* fblock = fval->compare(cond, con, tsux, fsux);
duke@435:                 if (tblock != fblock && !if_->is_safepoint()) {
duke@435:                   If* newif = new If(ifop->x(), ifop->cond(), false, ifop->y(),
duke@435:                                      tblock, fblock, if_->state_before(), if_->is_safepoint());
duke@435:                   newif->set_state(if_->state()->copy());
duke@435: 
duke@435:                   assert(prev->next() == if_, "must be guaranteed by above search");
duke@435:                   prev->set_next(newif, if_->bci());
duke@435:                   block->set_end(newif);
duke@435: 
duke@435:                   _merge_count++;
duke@435:                   if (PrintBlockElimination) {
duke@435:                     tty->print_cr("%d. replaced If and IfOp at end of B%d with single If", _merge_count, block->block_id());
duke@435:                   }
duke@435: 
duke@435:                   _hir->verify();
duke@435:                 }
duke@435:               }
duke@435:             }
duke@435:           }
duke@435:         }
duke@435: 
duke@435:         return true;
duke@435:       }
duke@435:     }
duke@435:     return false;
duke@435:   }
duke@435: 
duke@435:   virtual void block_do(BlockBegin* block) {
duke@435:     _hir->verify();
duke@435:     // repeat since the same block may merge again
duke@435:     while (try_merge(block)) {
duke@435:       _hir->verify();
duke@435:     }
duke@435:   }
duke@435: };
duke@435: 
duke@435: 
duke@435: void Optimizer::eliminate_blocks() {
duke@435:   // merge blocks if possible
duke@435:   BlockMerger bm(ir());
duke@435: }
duke@435: 
duke@435: 
duke@435: class NullCheckEliminator;
duke@435: class NullCheckVisitor: public InstructionVisitor {
duke@435: private:
duke@435:   NullCheckEliminator* _nce;
duke@435:   NullCheckEliminator* nce() { return _nce; }
duke@435: 
duke@435: public:
duke@435:   NullCheckVisitor() {}
duke@435: 
duke@435:   void set_eliminator(NullCheckEliminator* nce) { _nce = nce; }
duke@435: 
duke@435:   void do_Phi            (Phi*             x);
duke@435:   void do_Local          (Local*           x);
duke@435:   void do_Constant       (Constant*        x);
duke@435:   void do_LoadField      (LoadField*       x);
duke@435:   void do_StoreField     (StoreField*      x);
duke@435:   void do_ArrayLength    (ArrayLength*     x);
duke@435:   void do_LoadIndexed    (LoadIndexed*     x);
duke@435:   void do_StoreIndexed   (StoreIndexed*    x);
duke@435:   void do_NegateOp       (NegateOp*        x);
duke@435:   void do_ArithmeticOp   (ArithmeticOp*    x);
duke@435:   void do_ShiftOp        (ShiftOp*         x);
duke@435:   void do_LogicOp        (LogicOp*         x);
duke@435:   void do_CompareOp      (CompareOp*       x);
duke@435:   void do_IfOp           (IfOp*            x);
duke@435:   void do_Convert        (Convert*         x);
duke@435:   void do_NullCheck      (NullCheck*       x);
duke@435:   void do_Invoke         (Invoke*          x);
duke@435:   void do_NewInstance    (NewInstance*     x);
duke@435:   void do_NewTypeArray   (NewTypeArray*    x);
duke@435:   void do_NewObjectArray (NewObjectArray*  x);
duke@435:   void do_NewMultiArray  (NewMultiArray*   x);
duke@435:   void do_CheckCast      (CheckCast*       x);
duke@435:   void do_InstanceOf     (InstanceOf*      x);
duke@435:   void do_MonitorEnter   (MonitorEnter*    x);
duke@435:   void do_MonitorExit    (MonitorExit*     x);
duke@435:   void do_Intrinsic      (Intrinsic*       x);
duke@435:   void do_BlockBegin     (BlockBegin*      x);
duke@435:   void do_Goto           (Goto*            x);
duke@435:   void do_If             (If*              x);
duke@435:   void do_IfInstanceOf   (IfInstanceOf*    x);
duke@435:   void do_TableSwitch    (TableSwitch*     x);
duke@435:   void do_LookupSwitch   (LookupSwitch*    x);
duke@435:   void do_Return         (Return*          x);
duke@435:   void do_Throw          (Throw*           x);
duke@435:   void do_Base           (Base*            x);
duke@435:   void do_OsrEntry       (OsrEntry*        x);
duke@435:   void do_ExceptionObject(ExceptionObject* x);
duke@435:   void do_RoundFP        (RoundFP*         x);
duke@435:   void do_UnsafeGetRaw   (UnsafeGetRaw*    x);
duke@435:   void do_UnsafePutRaw   (UnsafePutRaw*    x);
duke@435:   void do_UnsafeGetObject(UnsafeGetObject* x);
duke@435:   void do_UnsafePutObject(UnsafePutObject* x);
duke@435:   void do_UnsafePrefetchRead (UnsafePrefetchRead*  x);
duke@435:   void do_UnsafePrefetchWrite(UnsafePrefetchWrite* x);
duke@435:   void do_ProfileCall    (ProfileCall*     x);
duke@435:   void do_ProfileCounter (ProfileCounter*  x);
duke@435: };
duke@435: 
duke@435: 
duke@435: // Because of a static contained within (for the purpose of iteration
duke@435: // over instructions), it is only valid to have one of these active at
duke@435: // a time
duke@435: class NullCheckEliminator {
duke@435:  private:
duke@435:   static NullCheckEliminator* _static_nce;
duke@435:   static void                 do_value(Value* vp);
duke@435: 
duke@435:   Optimizer*        _opt;
duke@435: 
duke@435:   ValueSet*         _visitable_instructions;        // Visit each instruction only once per basic block
duke@435:   BlockList*        _work_list;                   // Basic blocks to visit
duke@435: 
duke@435:   bool visitable(Value x) {
duke@435:     assert(_visitable_instructions != NULL, "check");
duke@435:     return _visitable_instructions->contains(x);
duke@435:   }
duke@435:   void mark_visited(Value x) {
duke@435:     assert(_visitable_instructions != NULL, "check");
duke@435:     _visitable_instructions->remove(x);
duke@435:   }
duke@435:   void mark_visitable(Value x) {
duke@435:     assert(_visitable_instructions != NULL, "check");
duke@435:     _visitable_instructions->put(x);
duke@435:   }
duke@435:   void clear_visitable_state() {
duke@435:     assert(_visitable_instructions != NULL, "check");
duke@435:     _visitable_instructions->clear();
duke@435:   }
duke@435: 
duke@435:   ValueSet*         _set;                         // current state, propagated to subsequent BlockBegins
duke@435:   ValueSetList      _block_states;                // BlockBegin null-check states for all processed blocks
duke@435:   NullCheckVisitor  _visitor;
duke@435:   NullCheck*        _last_explicit_null_check;
duke@435: 
duke@435:   bool set_contains(Value x)                      { assert(_set != NULL, "check"); return _set->contains(x); }
duke@435:   void set_put     (Value x)                      { assert(_set != NULL, "check"); _set->put(x); }
duke@435:   void set_remove  (Value x)                      { assert(_set != NULL, "check"); _set->remove(x); }
duke@435: 
duke@435:   BlockList* work_list()                          { return _work_list; }
duke@435: 
duke@435:   void iterate_all();
duke@435:   void iterate_one(BlockBegin* block);
duke@435: 
duke@435:   ValueSet* state()                               { return _set; }
duke@435:   void      set_state_from (ValueSet* state)      { _set->set_from(state); }
duke@435:   ValueSet* state_for      (BlockBegin* block)    { return _block_states[block->block_id()]; }
duke@435:   void      set_state_for  (BlockBegin* block, ValueSet* stack) { _block_states[block->block_id()] = stack; }
duke@435:   // Returns true if caused a change in the block's state.
duke@435:   bool      merge_state_for(BlockBegin* block,
duke@435:                             ValueSet*   incoming_state);
duke@435: 
duke@435:  public:
duke@435:   // constructor
duke@435:   NullCheckEliminator(Optimizer* opt)
duke@435:     : _opt(opt)
duke@435:     , _set(new ValueSet())
duke@435:     , _last_explicit_null_check(NULL)
duke@435:     , _block_states(BlockBegin::number_of_blocks(), NULL)
duke@435:     , _work_list(new BlockList()) {
duke@435:     _visitable_instructions = new ValueSet();
duke@435:     _visitor.set_eliminator(this);
duke@435:   }
duke@435: 
duke@435:   Optimizer*  opt()                               { return _opt; }
duke@435:   IR*         ir ()                               { return opt()->ir(); }
duke@435: 
duke@435:   // Process a graph
duke@435:   void iterate(BlockBegin* root);
duke@435: 
duke@435:   // In some situations (like NullCheck(x); getfield(x)) the debug
duke@435:   // information from the explicit NullCheck can be used to populate
duke@435:   // the getfield, even if the two instructions are in different
duke@435:   // scopes; this allows implicit null checks to be used but the
duke@435:   // correct exception information to be generated. We must clear the
duke@435:   // last-traversed NullCheck when we reach a potentially-exception-
duke@435:   // throwing instruction, as well as in some other cases.
duke@435:   void        set_last_explicit_null_check(NullCheck* check) { _last_explicit_null_check = check; }
duke@435:   NullCheck*  last_explicit_null_check()                     { return _last_explicit_null_check; }
duke@435:   Value       last_explicit_null_check_obj()                 { return (_last_explicit_null_check
duke@435:                                                                          ? _last_explicit_null_check->obj()
duke@435:                                                                          : NULL); }
duke@435:   NullCheck*  consume_last_explicit_null_check() {
duke@435:     _last_explicit_null_check->unpin(Instruction::PinExplicitNullCheck);
duke@435:     _last_explicit_null_check->set_can_trap(false);
duke@435:     return _last_explicit_null_check;
duke@435:   }
duke@435:   void        clear_last_explicit_null_check()               { _last_explicit_null_check = NULL; }
duke@435: 
duke@435:   // Handlers for relevant instructions
duke@435:   // (separated out from NullCheckVisitor for clarity)
duke@435: 
duke@435:   // The basic contract is that these must leave the instruction in
duke@435:   // the desired state; must not assume anything about the state of
duke@435:   // the instruction. We make multiple passes over some basic blocks
duke@435:   // and the last pass is the only one whose result is valid.
duke@435:   void handle_AccessField     (AccessField* x);
duke@435:   void handle_ArrayLength     (ArrayLength* x);
duke@435:   void handle_LoadIndexed     (LoadIndexed* x);
duke@435:   void handle_StoreIndexed    (StoreIndexed* x);
duke@435:   void handle_NullCheck       (NullCheck* x);
duke@435:   void handle_Invoke          (Invoke* x);
duke@435:   void handle_NewInstance     (NewInstance* x);
duke@435:   void handle_NewArray        (NewArray* x);
duke@435:   void handle_AccessMonitor   (AccessMonitor* x);
duke@435:   void handle_Intrinsic       (Intrinsic* x);
duke@435:   void handle_ExceptionObject (ExceptionObject* x);
duke@435:   void handle_Phi             (Phi* x);
duke@435: };
duke@435: 
duke@435: 
duke@435: // NEEDS_CLEANUP
duke@435: // There may be other instructions which need to clear the last
duke@435: // explicit null check. Anything across which we can not hoist the
duke@435: // debug information for a NullCheck instruction must clear it. It
duke@435: // might be safer to pattern match "NullCheck ; {AccessField,
duke@435: // ArrayLength, LoadIndexed}" but it is more easily structured this way.
duke@435: // Should test to see performance hit of clearing it for all handlers
duke@435: // with empty bodies below. If it is negligible then we should leave
duke@435: // that in for safety, otherwise should think more about it.
duke@435: void NullCheckVisitor::do_Phi            (Phi*             x) { nce()->handle_Phi(x);      }
duke@435: void NullCheckVisitor::do_Local          (Local*           x) {}
duke@435: void NullCheckVisitor::do_Constant       (Constant*        x) { /* FIXME: handle object constants */ }
duke@435: void NullCheckVisitor::do_LoadField      (LoadField*       x) { nce()->handle_AccessField(x); }
duke@435: void NullCheckVisitor::do_StoreField     (StoreField*      x) { nce()->handle_AccessField(x); }
duke@435: void NullCheckVisitor::do_ArrayLength    (ArrayLength*     x) { nce()->handle_ArrayLength(x); }
duke@435: void NullCheckVisitor::do_LoadIndexed    (LoadIndexed*     x) { nce()->handle_LoadIndexed(x); }
duke@435: void NullCheckVisitor::do_StoreIndexed   (StoreIndexed*    x) { nce()->handle_StoreIndexed(x); }
duke@435: void NullCheckVisitor::do_NegateOp       (NegateOp*        x) {}
duke@435: void NullCheckVisitor::do_ArithmeticOp   (ArithmeticOp*    x) { if (x->can_trap()) nce()->clear_last_explicit_null_check(); }
duke@435: void NullCheckVisitor::do_ShiftOp        (ShiftOp*         x) {}
duke@435: void NullCheckVisitor::do_LogicOp        (LogicOp*         x) {}
duke@435: void NullCheckVisitor::do_CompareOp      (CompareOp*       x) {}
duke@435: void NullCheckVisitor::do_IfOp           (IfOp*            x) {}
duke@435: void NullCheckVisitor::do_Convert        (Convert*         x) {}
duke@435: void NullCheckVisitor::do_NullCheck      (NullCheck*       x) { nce()->handle_NullCheck(x); }
duke@435: void NullCheckVisitor::do_Invoke         (Invoke*          x) { nce()->handle_Invoke(x); }
duke@435: void NullCheckVisitor::do_NewInstance    (NewInstance*     x) { nce()->handle_NewInstance(x); }
duke@435: void NullCheckVisitor::do_NewTypeArray   (NewTypeArray*    x) { nce()->handle_NewArray(x); }
duke@435: void NullCheckVisitor::do_NewObjectArray (NewObjectArray*  x) { nce()->handle_NewArray(x); }
duke@435: void NullCheckVisitor::do_NewMultiArray  (NewMultiArray*   x) { nce()->handle_NewArray(x); }
duke@435: void NullCheckVisitor::do_CheckCast      (CheckCast*       x) {}
duke@435: void NullCheckVisitor::do_InstanceOf     (InstanceOf*      x) {}
duke@435: void NullCheckVisitor::do_MonitorEnter   (MonitorEnter*    x) { nce()->handle_AccessMonitor(x); }
duke@435: void NullCheckVisitor::do_MonitorExit    (MonitorExit*     x) { nce()->handle_AccessMonitor(x); }
duke@435: void NullCheckVisitor::do_Intrinsic      (Intrinsic*       x) { nce()->clear_last_explicit_null_check(); }
duke@435: void NullCheckVisitor::do_BlockBegin     (BlockBegin*      x) {}
duke@435: void NullCheckVisitor::do_Goto           (Goto*            x) {}
duke@435: void NullCheckVisitor::do_If             (If*              x) {}
duke@435: void NullCheckVisitor::do_IfInstanceOf   (IfInstanceOf*    x) {}
duke@435: void NullCheckVisitor::do_TableSwitch    (TableSwitch*     x) {}
duke@435: void NullCheckVisitor::do_LookupSwitch   (LookupSwitch*    x) {}
duke@435: void NullCheckVisitor::do_Return         (Return*          x) {}
duke@435: void NullCheckVisitor::do_Throw          (Throw*           x) { nce()->clear_last_explicit_null_check(); }
duke@435: void NullCheckVisitor::do_Base           (Base*            x) {}
duke@435: void NullCheckVisitor::do_OsrEntry       (OsrEntry*        x) {}
duke@435: void NullCheckVisitor::do_ExceptionObject(ExceptionObject* x) { nce()->handle_ExceptionObject(x); }
duke@435: void NullCheckVisitor::do_RoundFP        (RoundFP*         x) {}
duke@435: void NullCheckVisitor::do_UnsafeGetRaw   (UnsafeGetRaw*    x) {}
duke@435: void NullCheckVisitor::do_UnsafePutRaw   (UnsafePutRaw*    x) {}
duke@435: void NullCheckVisitor::do_UnsafeGetObject(UnsafeGetObject* x) {}
duke@435: void NullCheckVisitor::do_UnsafePutObject(UnsafePutObject* x) {}
duke@435: void NullCheckVisitor::do_UnsafePrefetchRead (UnsafePrefetchRead*  x) {}
duke@435: void NullCheckVisitor::do_UnsafePrefetchWrite(UnsafePrefetchWrite* x) {}
duke@435: void NullCheckVisitor::do_ProfileCall    (ProfileCall*     x) { nce()->clear_last_explicit_null_check(); }
duke@435: void NullCheckVisitor::do_ProfileCounter (ProfileCounter*  x) {}
duke@435: 
duke@435: 
duke@435: NullCheckEliminator* NullCheckEliminator::_static_nce = NULL;
duke@435: 
duke@435: 
duke@435: void NullCheckEliminator::do_value(Value* p) {
duke@435:   assert(*p != NULL, "should not find NULL instructions");
duke@435:   if (_static_nce->visitable(*p)) {
duke@435:     _static_nce->mark_visited(*p);
duke@435:     (*p)->visit(&_static_nce->_visitor);
duke@435:   }
duke@435: }
duke@435: 
duke@435: bool NullCheckEliminator::merge_state_for(BlockBegin* block, ValueSet* incoming_state) {
duke@435:   ValueSet* state = state_for(block);
duke@435:   if (state == NULL) {
duke@435:     state = incoming_state->copy();
duke@435:     set_state_for(block, state);
duke@435:     return true;
duke@435:   } else {
duke@435:     bool changed = state->set_intersect(incoming_state);
duke@435:     if (PrintNullCheckElimination && changed) {
duke@435:       tty->print_cr("Block %d's null check state changed", block->block_id());
duke@435:     }
duke@435:     return changed;
duke@435:   }
duke@435: }
duke@435: 
duke@435: 
duke@435: void NullCheckEliminator::iterate_all() {
duke@435:   while (work_list()->length() > 0) {
duke@435:     iterate_one(work_list()->pop());
duke@435:   }
duke@435: }
duke@435: 
duke@435: 
duke@435: void NullCheckEliminator::iterate_one(BlockBegin* block) {
duke@435:   _static_nce = this;
duke@435:   clear_visitable_state();
duke@435:   // clear out an old explicit null checks
duke@435:   set_last_explicit_null_check(NULL);
duke@435: 
duke@435:   if (PrintNullCheckElimination) {
duke@435:     tty->print_cr(" ...iterating block %d in null check elimination for %s::%s%s",
duke@435:                   block->block_id(),
duke@435:                   ir()->method()->holder()->name()->as_utf8(),
duke@435:                   ir()->method()->name()->as_utf8(),
duke@435:                   ir()->method()->signature()->as_symbol()->as_utf8());
duke@435:   }
duke@435: 
duke@435:   // Create new state if none present (only happens at root)
duke@435:   if (state_for(block) == NULL) {
duke@435:     ValueSet* tmp_state = new ValueSet();
duke@435:     set_state_for(block, tmp_state);
duke@435:     // Initial state is that local 0 (receiver) is non-null for
duke@435:     // non-static methods
duke@435:     ValueStack* stack  = block->state();
duke@435:     IRScope*    scope  = stack->scope();
duke@435:     ciMethod*   method = scope->method();
duke@435:     if (!method->is_static()) {
duke@435:       Local* local0 = stack->local_at(0)->as_Local();
duke@435:       assert(local0 != NULL, "must be");
duke@435:       assert(local0->type() == objectType, "invalid type of receiver");
duke@435: 
duke@435:       if (local0 != NULL) {
duke@435:         // Local 0 is used in this scope
duke@435:         tmp_state->put(local0);
duke@435:         if (PrintNullCheckElimination) {
duke@435:           tty->print_cr("Local 0 (value %d) proven non-null upon entry", local0->id());
duke@435:         }
duke@435:       }
duke@435:     }
duke@435:   }
duke@435: 
duke@435:   // Must copy block's state to avoid mutating it during iteration
duke@435:   // through the block -- otherwise "not-null" states can accidentally
duke@435:   // propagate "up" through the block during processing of backward
duke@435:   // branches and algorithm is incorrect (and does not converge)
duke@435:   set_state_from(state_for(block));
duke@435: 
duke@435:   // allow visiting of Phis belonging to this block
duke@435:   for_each_phi_fun(block, phi,
duke@435:                    mark_visitable(phi);
duke@435:                    );
duke@435: 
duke@435:   BlockEnd* e = block->end();
duke@435:   assert(e != NULL, "incomplete graph");
duke@435:   int i;
duke@435: 
duke@435:   // Propagate the state before this block into the exception
duke@435:   // handlers.  They aren't true successors since we aren't guaranteed
duke@435:   // to execute the whole block before executing them.  Also putting
duke@435:   // them on first seems to help reduce the amount of iteration to
duke@435:   // reach a fixed point.
duke@435:   for (i = 0; i < block->number_of_exception_handlers(); i++) {
duke@435:     BlockBegin* next = block->exception_handler_at(i);
duke@435:     if (merge_state_for(next, state())) {
duke@435:       if (!work_list()->contains(next)) {
duke@435:         work_list()->push(next);
duke@435:       }
duke@435:     }
duke@435:   }
duke@435: 
duke@435:   // Iterate through block, updating state.
duke@435:   for (Instruction* instr = block; instr != NULL; instr = instr->next()) {
duke@435:     // Mark instructions in this block as visitable as they are seen
duke@435:     // in the instruction list.  This keeps the iteration from
duke@435:     // visiting instructions which are references in other blocks or
duke@435:     // visiting instructions more than once.
duke@435:     mark_visitable(instr);
duke@435:     if (instr->is_root() || instr->can_trap() || (instr->as_NullCheck() != NULL)) {
duke@435:       mark_visited(instr);
duke@435:       instr->input_values_do(&NullCheckEliminator::do_value);
duke@435:       instr->visit(&_visitor);
duke@435:     }
duke@435:   }
duke@435: 
duke@435:   // Propagate state to successors if necessary
duke@435:   for (i = 0; i < e->number_of_sux(); i++) {
duke@435:     BlockBegin* next = e->sux_at(i);
duke@435:     if (merge_state_for(next, state())) {
duke@435:       if (!work_list()->contains(next)) {
duke@435:         work_list()->push(next);
duke@435:       }
duke@435:     }
duke@435:   }
duke@435: }
duke@435: 
duke@435: 
duke@435: void NullCheckEliminator::iterate(BlockBegin* block) {
duke@435:   work_list()->push(block);
duke@435:   iterate_all();
duke@435: }
duke@435: 
duke@435: void NullCheckEliminator::handle_AccessField(AccessField* x) {
duke@435:   if (x->is_static()) {
duke@435:     if (x->as_LoadField() != NULL) {
duke@435:       // If the field is a non-null static final object field (as is
duke@435:       // often the case for sun.misc.Unsafe), put this LoadField into
duke@435:       // the non-null map
duke@435:       ciField* field = x->field();
duke@435:       if (field->is_constant()) {
duke@435:         ciConstant field_val = field->constant_value();
duke@435:         BasicType field_type = field_val.basic_type();
duke@435:         if (field_type == T_OBJECT || field_type == T_ARRAY) {
duke@435:           ciObject* obj_val = field_val.as_object();
duke@435:           if (!obj_val->is_null_object()) {
duke@435:             if (PrintNullCheckElimination) {
duke@435:               tty->print_cr("AccessField %d proven non-null by static final non-null oop check",
duke@435:                             x->id());
duke@435:             }
duke@435:             set_put(x);
duke@435:           }
duke@435:         }
duke@435:       }
duke@435:     }
duke@435:     // Be conservative
duke@435:     clear_last_explicit_null_check();
duke@435:     return;
duke@435:   }
duke@435: 
duke@435:   Value obj = x->obj();
duke@435:   if (set_contains(obj)) {
duke@435:     // Value is non-null => update AccessField
duke@435:     if (last_explicit_null_check_obj() == obj && !x->needs_patching()) {
duke@435:       x->set_explicit_null_check(consume_last_explicit_null_check());
duke@435:       x->set_needs_null_check(true);
duke@435:       if (PrintNullCheckElimination) {
duke@435:         tty->print_cr("Folded NullCheck %d into AccessField %d's null check for value %d",
duke@435:                       x->explicit_null_check()->id(), x->id(), obj->id());
duke@435:       }
duke@435:     } else {
duke@435:       x->set_explicit_null_check(NULL);
duke@435:       x->set_needs_null_check(false);
duke@435:       if (PrintNullCheckElimination) {
duke@435:         tty->print_cr("Eliminated AccessField %d's null check for value %d", x->id(), obj->id());
duke@435:       }
duke@435:     }
duke@435:   } else {
duke@435:     set_put(obj);
duke@435:     if (PrintNullCheckElimination) {
duke@435:       tty->print_cr("AccessField %d of value %d proves value to be non-null", x->id(), obj->id());
duke@435:     }
duke@435:     // Ensure previous passes do not cause wrong state
duke@435:     x->set_needs_null_check(true);
duke@435:     x->set_explicit_null_check(NULL);
duke@435:   }
duke@435:   clear_last_explicit_null_check();
duke@435: }
duke@435: 
duke@435: 
duke@435: void NullCheckEliminator::handle_ArrayLength(ArrayLength* x) {
duke@435:   Value array = x->array();
duke@435:   if (set_contains(array)) {
duke@435:     // Value is non-null => update AccessArray
duke@435:     if (last_explicit_null_check_obj() == array) {
duke@435:       x->set_explicit_null_check(consume_last_explicit_null_check());
duke@435:       x->set_needs_null_check(true);
duke@435:       if (PrintNullCheckElimination) {
duke@435:         tty->print_cr("Folded NullCheck %d into ArrayLength %d's null check for value %d",
duke@435:                       x->explicit_null_check()->id(), x->id(), array->id());
duke@435:       }
duke@435:     } else {
duke@435:       x->set_explicit_null_check(NULL);
duke@435:       x->set_needs_null_check(false);
duke@435:       if (PrintNullCheckElimination) {
duke@435:         tty->print_cr("Eliminated ArrayLength %d's null check for value %d", x->id(), array->id());
duke@435:       }
duke@435:     }
duke@435:   } else {
duke@435:     set_put(array);
duke@435:     if (PrintNullCheckElimination) {
duke@435:       tty->print_cr("ArrayLength %d of value %d proves value to be non-null", x->id(), array->id());
duke@435:     }
duke@435:     // Ensure previous passes do not cause wrong state
duke@435:     x->set_needs_null_check(true);
duke@435:     x->set_explicit_null_check(NULL);
duke@435:   }
duke@435:   clear_last_explicit_null_check();
duke@435: }
duke@435: 
duke@435: 
duke@435: void NullCheckEliminator::handle_LoadIndexed(LoadIndexed* x) {
duke@435:   Value array = x->array();
duke@435:   if (set_contains(array)) {
duke@435:     // Value is non-null => update AccessArray
duke@435:     if (last_explicit_null_check_obj() == array) {
duke@435:       x->set_explicit_null_check(consume_last_explicit_null_check());
duke@435:       x->set_needs_null_check(true);
duke@435:       if (PrintNullCheckElimination) {
duke@435:         tty->print_cr("Folded NullCheck %d into LoadIndexed %d's null check for value %d",
duke@435:                       x->explicit_null_check()->id(), x->id(), array->id());
duke@435:       }
duke@435:     } else {
duke@435:       x->set_explicit_null_check(NULL);
duke@435:       x->set_needs_null_check(false);
duke@435:       if (PrintNullCheckElimination) {
duke@435:         tty->print_cr("Eliminated LoadIndexed %d's null check for value %d", x->id(), array->id());
duke@435:       }
duke@435:     }
duke@435:   } else {
duke@435:     set_put(array);
duke@435:     if (PrintNullCheckElimination) {
duke@435:       tty->print_cr("LoadIndexed %d of value %d proves value to be non-null", x->id(), array->id());
duke@435:     }
duke@435:     // Ensure previous passes do not cause wrong state
duke@435:     x->set_needs_null_check(true);
duke@435:     x->set_explicit_null_check(NULL);
duke@435:   }
duke@435:   clear_last_explicit_null_check();
duke@435: }
duke@435: 
duke@435: 
duke@435: void NullCheckEliminator::handle_StoreIndexed(StoreIndexed* x) {
duke@435:   Value array = x->array();
duke@435:   if (set_contains(array)) {
duke@435:     // Value is non-null => update AccessArray
duke@435:     if (PrintNullCheckElimination) {
duke@435:       tty->print_cr("Eliminated StoreIndexed %d's null check for value %d", x->id(), array->id());
duke@435:     }
duke@435:     x->set_needs_null_check(false);
duke@435:   } else {
duke@435:     set_put(array);
duke@435:     if (PrintNullCheckElimination) {
duke@435:       tty->print_cr("StoreIndexed %d of value %d proves value to be non-null", x->id(), array->id());
duke@435:     }
duke@435:     // Ensure previous passes do not cause wrong state
duke@435:     x->set_needs_null_check(true);
duke@435:   }
duke@435:   clear_last_explicit_null_check();
duke@435: }
duke@435: 
duke@435: 
duke@435: void NullCheckEliminator::handle_NullCheck(NullCheck* x) {
duke@435:   Value obj = x->obj();
duke@435:   if (set_contains(obj)) {
duke@435:     // Already proven to be non-null => this NullCheck is useless
duke@435:     if (PrintNullCheckElimination) {
duke@435:       tty->print_cr("Eliminated NullCheck %d for value %d", x->id(), obj->id());
duke@435:     }
duke@435:     // Don't unpin since that may shrink obj's live range and make it unavailable for debug info.
duke@435:     // The code generator won't emit LIR for a NullCheck that cannot trap.
duke@435:     x->set_can_trap(false);
duke@435:   } else {
duke@435:     // May be null => add to map and set last explicit NullCheck
duke@435:     x->set_can_trap(true);
duke@435:     // make sure it's pinned if it can trap
duke@435:     x->pin(Instruction::PinExplicitNullCheck);
duke@435:     set_put(obj);
duke@435:     set_last_explicit_null_check(x);
duke@435:     if (PrintNullCheckElimination) {
duke@435:       tty->print_cr("NullCheck %d of value %d proves value to be non-null", x->id(), obj->id());
duke@435:     }
duke@435:   }
duke@435: }
duke@435: 
duke@435: 
duke@435: void NullCheckEliminator::handle_Invoke(Invoke* x) {
duke@435:   if (!x->has_receiver()) {
duke@435:     // Be conservative
duke@435:     clear_last_explicit_null_check();
duke@435:     return;
duke@435:   }
duke@435: 
duke@435:   Value recv = x->receiver();
duke@435:   if (!set_contains(recv)) {
duke@435:     set_put(recv);
duke@435:     if (PrintNullCheckElimination) {
duke@435:       tty->print_cr("Invoke %d of value %d proves value to be non-null", x->id(), recv->id());
duke@435:     }
duke@435:   }
duke@435:   clear_last_explicit_null_check();
duke@435: }
duke@435: 
duke@435: 
duke@435: void NullCheckEliminator::handle_NewInstance(NewInstance* x) {
duke@435:   set_put(x);
duke@435:   if (PrintNullCheckElimination) {
duke@435:     tty->print_cr("NewInstance %d is non-null", x->id());
duke@435:   }
duke@435: }
duke@435: 
duke@435: 
duke@435: void NullCheckEliminator::handle_NewArray(NewArray* x) {
duke@435:   set_put(x);
duke@435:   if (PrintNullCheckElimination) {
duke@435:     tty->print_cr("NewArray %d is non-null", x->id());
duke@435:   }
duke@435: }
duke@435: 
duke@435: 
duke@435: void NullCheckEliminator::handle_ExceptionObject(ExceptionObject* x) {
duke@435:   set_put(x);
duke@435:   if (PrintNullCheckElimination) {
duke@435:     tty->print_cr("ExceptionObject %d is non-null", x->id());
duke@435:   }
duke@435: }
duke@435: 
duke@435: 
duke@435: void NullCheckEliminator::handle_AccessMonitor(AccessMonitor* x) {
duke@435:   Value obj = x->obj();
duke@435:   if (set_contains(obj)) {
duke@435:     // Value is non-null => update AccessMonitor
duke@435:     if (PrintNullCheckElimination) {
duke@435:       tty->print_cr("Eliminated AccessMonitor %d's null check for value %d", x->id(), obj->id());
duke@435:     }
duke@435:     x->set_needs_null_check(false);
duke@435:   } else {
duke@435:     set_put(obj);
duke@435:     if (PrintNullCheckElimination) {
duke@435:       tty->print_cr("AccessMonitor %d of value %d proves value to be non-null", x->id(), obj->id());
duke@435:     }
duke@435:     // Ensure previous passes do not cause wrong state
duke@435:     x->set_needs_null_check(true);
duke@435:   }
duke@435:   clear_last_explicit_null_check();
duke@435: }
duke@435: 
duke@435: 
duke@435: void NullCheckEliminator::handle_Intrinsic(Intrinsic* x) {
duke@435:   if (!x->has_receiver()) {
duke@435:     // Be conservative
duke@435:     clear_last_explicit_null_check();
duke@435:     return;
duke@435:   }
duke@435: 
duke@435:   Value recv = x->receiver();
duke@435:   if (set_contains(recv)) {
duke@435:     // Value is non-null => update Intrinsic
duke@435:     if (PrintNullCheckElimination) {
duke@435:       tty->print_cr("Eliminated Intrinsic %d's null check for value %d", x->id(), recv->id());
duke@435:     }
duke@435:     x->set_needs_null_check(false);
duke@435:   } else {
duke@435:     set_put(recv);
duke@435:     if (PrintNullCheckElimination) {
duke@435:       tty->print_cr("Intrinsic %d of value %d proves value to be non-null", x->id(), recv->id());
duke@435:     }
duke@435:     // Ensure previous passes do not cause wrong state
duke@435:     x->set_needs_null_check(true);
duke@435:   }
duke@435:   clear_last_explicit_null_check();
duke@435: }
duke@435: 
duke@435: 
duke@435: void NullCheckEliminator::handle_Phi(Phi* x) {
duke@435:   int i;
duke@435:   bool all_non_null = true;
duke@435:   if (x->is_illegal()) {
duke@435:     all_non_null = false;
duke@435:   } else {
duke@435:     for (i = 0; i < x->operand_count(); i++) {
duke@435:       Value input = x->operand_at(i);
duke@435:       if (!set_contains(input)) {
duke@435:         all_non_null = false;
duke@435:       }
duke@435:     }
duke@435:   }
duke@435: 
duke@435:   if (all_non_null) {
duke@435:     // Value is non-null => update Phi
duke@435:     if (PrintNullCheckElimination) {
duke@435:       tty->print_cr("Eliminated Phi %d's null check for phifun because all inputs are non-null", x->id());
duke@435:     }
duke@435:     x->set_needs_null_check(false);
duke@435:   } else if (set_contains(x)) {
duke@435:     set_remove(x);
duke@435:   }
duke@435: }
duke@435: 
duke@435: 
duke@435: void Optimizer::eliminate_null_checks() {
duke@435:   ResourceMark rm;
duke@435: 
duke@435:   NullCheckEliminator nce(this);
duke@435: 
duke@435:   if (PrintNullCheckElimination) {
duke@435:     tty->print_cr("Starting null check elimination for method %s::%s%s",
duke@435:                   ir()->method()->holder()->name()->as_utf8(),
duke@435:                   ir()->method()->name()->as_utf8(),
duke@435:                   ir()->method()->signature()->as_symbol()->as_utf8());
duke@435:   }
duke@435: 
duke@435:   // Apply to graph
duke@435:   nce.iterate(ir()->start());
duke@435: 
duke@435:   // walk over the graph looking for exception
duke@435:   // handlers and iterate over them as well
duke@435:   int nblocks = BlockBegin::number_of_blocks();
duke@435:   BlockList blocks(nblocks);
duke@435:   boolArray visited_block(nblocks, false);
duke@435: 
duke@435:   blocks.push(ir()->start());
duke@435:   visited_block[ir()->start()->block_id()] = true;
duke@435:   for (int i = 0; i < blocks.length(); i++) {
duke@435:     BlockBegin* b = blocks[i];
duke@435:     // exception handlers need to be treated as additional roots
duke@435:     for (int e = b->number_of_exception_handlers(); e-- > 0; ) {
duke@435:       BlockBegin* excp = b->exception_handler_at(e);
duke@435:       int id = excp->block_id();
duke@435:       if (!visited_block[id]) {
duke@435:         blocks.push(excp);
duke@435:         visited_block[id] = true;
duke@435:         nce.iterate(excp);
duke@435:       }
duke@435:     }
duke@435:     // traverse successors
duke@435:     BlockEnd *end = b->end();
duke@435:     for (int s = end->number_of_sux(); s-- > 0; ) {
duke@435:       BlockBegin* next = end->sux_at(s);
duke@435:       int id = next->block_id();
duke@435:       if (!visited_block[id]) {
duke@435:         blocks.push(next);
duke@435:         visited_block[id] = true;
duke@435:       }
duke@435:     }
duke@435:   }
duke@435: 
duke@435: 
duke@435:   if (PrintNullCheckElimination) {
duke@435:     tty->print_cr("Done with null check elimination for method %s::%s%s",
duke@435:                   ir()->method()->holder()->name()->as_utf8(),
duke@435:                   ir()->method()->name()->as_utf8(),
duke@435:                   ir()->method()->signature()->as_symbol()->as_utf8());
duke@435:   }
duke@435: }