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 /*

  * Copyright (c) 2006, 2010, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

  * questions.

  *

  */

 #include "precompiled.hpp"

 #include "memory/allocation.inline.hpp"

 #include "opto/connode.hpp"

 #include "opto/loopnode.hpp"

 #include "opto/rootnode.hpp"

 //================= Loop Unswitching =====================

 //

 // orig:                       transformed:

 //                               if (invariant-test) then

 //  loop                           loop

 //    stmt1                          stmt1

 //    if (invariant-test) then       stmt2

 //      stmt2                        stmt4

 //    else                         endloop

 //      stmt3                    else

 //    endif                        loop [clone]

 //    stmt4                          stmt1 [clone]

 //  endloop                          stmt3

 //                                   stmt4 [clone]

 //                                 endloop

 //                               endif

 //

 // Note: the "else" clause may be empty

 //------------------------------policy_unswitching-----------------------------

 // Return TRUE or FALSE if the loop should be unswitched

 // (ie. clone loop with an invariant test that does not exit the loop)

 bool IdealLoopTree::policy_unswitching( PhaseIdealLoop *phase ) const {

   if( !LoopUnswitching ) {

     return false;

   }

   if (!_head->is_Loop()) {

     return false;

   }

   uint nodes_left = MaxNodeLimit - phase->C->unique();

   if (2 * _body.size() > nodes_left) {

     return false; // Too speculative if running low on nodes.

   }

   LoopNode* head = _head->as_Loop();

   if (head->unswitch_count() + 1 > head->unswitch_max()) {

     return false;

   }

   return phase->find_unswitching_candidate(this) != NULL;

 }

 //------------------------------find_unswitching_candidate-----------------------------

 // Find candidate "if" for unswitching

 IfNode* PhaseIdealLoop::find_unswitching_candidate(const IdealLoopTree *loop) const {

   // Find first invariant test that doesn't exit the loop

   LoopNode *head = loop->_head->as_Loop();

   IfNode* unswitch_iff = NULL;

   Node* n = head->in(LoopNode::LoopBackControl);

   while (n != head) {

     Node* n_dom = idom(n);

     if (n->is_Region()) {

       if (n_dom->is_If()) {

         IfNode* iff = n_dom->as_If();

         if (iff->in(1)->is_Bool()) {

           BoolNode* bol = iff->in(1)->as_Bool();

           if (bol->in(1)->is_Cmp()) {

             // If condition is invariant and not a loop exit,

             // then found reason to unswitch.

             if (loop->is_invariant(bol) && !loop->is_loop_exit(iff)) {

               unswitch_iff = iff;

             }

           }

         }

       }

     }

     n = n_dom;

   }

   return unswitch_iff;

 }

 //------------------------------do_unswitching-----------------------------

 // Clone loop with an invariant test (that does not exit) and

 // insert a clone of the test that selects which version to

 // execute.

 void PhaseIdealLoop::do_unswitching (IdealLoopTree *loop, Node_List &old_new) {

   // Find first invariant test that doesn't exit the loop

   LoopNode *head = loop->_head->as_Loop();

   IfNode* unswitch_iff = find_unswitching_candidate((const IdealLoopTree *)loop);

   assert(unswitch_iff != NULL, "should be at least one");

 #ifndef PRODUCT

   if (TraceLoopOpts) {

     tty->print("Unswitch   %d ", head->unswitch_count()+1);

     loop->dump_head();

   }

 #endif

   // Need to revert back to normal loop

   if (head->is_CountedLoop() && !head->as_CountedLoop()->is_normal_loop()) {

     head->as_CountedLoop()->set_normal_loop();

   }

   ProjNode* proj_true = create_slow_version_of_loop(loop, old_new);

   assert(proj_true->is_IfTrue() && proj_true->unique_ctrl_out() == head, "by construction");

   // Increment unswitch count

   LoopNode* head_clone = old_new[head->_idx]->as_Loop();

   int nct = head->unswitch_count() + 1;

   head->set_unswitch_count(nct);

   head_clone->set_unswitch_count(nct);

   // Add test to new "if" outside of loop

   IfNode* invar_iff   = proj_true->in(0)->as_If();

   Node* invar_iff_c   = invar_iff->in(0);

   BoolNode* bol       = unswitch_iff->in(1)->as_Bool();

   invar_iff->set_req(1, bol);

   invar_iff->_prob    = unswitch_iff->_prob;

   ProjNode* proj_false = invar_iff->proj_out(0)->as_Proj();

   // Hoist invariant casts out of each loop to the appropriate

   // control projection.

   Node_List worklist;

   for (DUIterator_Fast imax, i = unswitch_iff->fast_outs(imax); i < imax; i++) {

     ProjNode* proj= unswitch_iff->fast_out(i)->as_Proj();

     // Copy to a worklist for easier manipulation

     for (DUIterator_Fast jmax, j = proj->fast_outs(jmax); j < jmax; j++) {

       Node* use = proj->fast_out(j);

       if (use->Opcode() == Op_CheckCastPP && loop->is_invariant(use->in(1))) {

         worklist.push(use);

       }

     }

     ProjNode* invar_proj = invar_iff->proj_out(proj->_con)->as_Proj();

     while (worklist.size() > 0) {

       Node* use = worklist.pop();

       Node* nuse = use->clone();

       nuse->set_req(0, invar_proj);

       _igvn.hash_delete(use);

       use->set_req(1, nuse);

       _igvn._worklist.push(use);

       register_new_node(nuse, invar_proj);

       // Same for the clone

       Node* use_clone = old_new[use->_idx];

       _igvn.hash_delete(use_clone);

       use_clone->set_req(1, nuse);

       _igvn._worklist.push(use_clone);

     }

   }

   // Hardwire the control paths in the loops into if(true) and if(false)

   _igvn.hash_delete(unswitch_iff);

   short_circuit_if(unswitch_iff, proj_true);

   _igvn._worklist.push(unswitch_iff);

   IfNode* unswitch_iff_clone = old_new[unswitch_iff->_idx]->as_If();

   _igvn.hash_delete(unswitch_iff_clone);

   short_circuit_if(unswitch_iff_clone, proj_false);

   _igvn._worklist.push(unswitch_iff_clone);

   // Reoptimize loops

   loop->record_for_igvn();

   for(int i = loop->_body.size() - 1; i >= 0 ; i--) {

     Node *n = loop->_body[i];

     Node *n_clone = old_new[n->_idx];

     _igvn._worklist.push(n_clone);

   }

 #ifndef PRODUCT

   if (TraceLoopUnswitching) {

     tty->print_cr("Loop unswitching orig: %d @ %d  new: %d @ %d",

                   head->_idx,                unswitch_iff->_idx,

                   old_new[head->_idx]->_idx, unswitch_iff_clone->_idx);

   }

 #endif

   C->set_major_progress();

 }

 //-------------------------create_slow_version_of_loop------------------------

 // Create a slow version of the loop by cloning the loop

 // and inserting an if to select fast-slow versions.

 // Return control projection of the entry to the fast version.

 ProjNode* PhaseIdealLoop::create_slow_version_of_loop(IdealLoopTree *loop,

                                                       Node_List &old_new) {

   LoopNode* head  = loop->_head->as_Loop();

   Node*     entry = head->in(LoopNode::EntryControl);

   _igvn.hash_delete(entry);

   _igvn._worklist.push(entry);

   IdealLoopTree* outer_loop = loop->_parent;

   Node *cont      = _igvn.intcon(1);

   set_ctrl(cont, C->root());

   Node* opq       = new (C, 2) Opaque1Node(C, cont);

   register_node(opq, outer_loop, entry, dom_depth(entry));

   Node *bol       = new (C, 2) Conv2BNode(opq);

   register_node(bol, outer_loop, entry, dom_depth(entry));

   IfNode* iff = new (C, 2) IfNode(entry, bol, PROB_MAX, COUNT_UNKNOWN);

   register_node(iff, outer_loop, entry, dom_depth(entry));

   ProjNode* iffast = new (C, 1) IfTrueNode(iff);

   register_node(iffast, outer_loop, iff, dom_depth(iff));

   ProjNode* ifslow = new (C, 1) IfFalseNode(iff);

   register_node(ifslow, outer_loop, iff, dom_depth(iff));

   // Clone the loop body.  The clone becomes the fast loop.  The

   // original pre-header will (illegally) have 2 control users (old & new loops).

   clone_loop(loop, old_new, dom_depth(head), iff);

   assert(old_new[head->_idx]->is_Loop(), "" );

   // Fast (true) control

   _igvn.hash_delete(head);

   head->set_req(LoopNode::EntryControl, iffast);

   set_idom(head, iffast, dom_depth(head));

   _igvn._worklist.push(head);

   // Slow (false) control

   LoopNode* slow_head = old_new[head->_idx]->as_Loop();

   _igvn.hash_delete(slow_head);

   slow_head->set_req(LoopNode::EntryControl, ifslow);

   set_idom(slow_head, ifslow, dom_depth(slow_head));

   _igvn._worklist.push(slow_head);

   recompute_dom_depth();

   return iffast;

 }