jdk8-mips64-public/hotspot: src/share/vm/opto/cfgnode.cpp@f90c822e73f8 (annotated)

src/share/vm/opto/cfgnode.cpp@f90c822e73f8 (annotated)

src/share/vm/opto/cfgnode.cpp

Wed, 27 Apr 2016 01:25:04 +0800

author: aoqi
date: Wed, 27 Apr 2016 01:25:04 +0800
changeset 0: f90c822e73f8
child 6876: 710a3c8b516e
permissions: -rw-r--r--

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http://hg.openjdk.java.net/jdk8u/jdk8u/hotspot/
changeset: 6782:28b50d07f6f8
tag: jdk8u25-b17

 /*
  * Copyright (c) 1997, 2013, 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 "classfile/systemDictionary.hpp"
 #include "memory/allocation.inline.hpp"
 #include "oops/objArrayKlass.hpp"
 #include "opto/addnode.hpp"
 #include "opto/cfgnode.hpp"
 #include "opto/connode.hpp"
 #include "opto/loopnode.hpp"
 #include "opto/machnode.hpp"
 #include "opto/mulnode.hpp"
 #include "opto/phaseX.hpp"
 #include "opto/regmask.hpp"
 #include "opto/runtime.hpp"
 #include "opto/subnode.hpp"
 // Portions of code courtesy of Clifford Click
 // Optimization - Graph Style
 //=============================================================================
 //------------------------------Value------------------------------------------
 // Compute the type of the RegionNode.
 const Type *RegionNode::Value( PhaseTransform *phase ) const {
   for( uint i=1; i<req(); ++i ) {       // For all paths in
     Node *n = in(i);            // Get Control source
     if( !n ) continue;          // Missing inputs are TOP
     if( phase->type(n) == Type::CONTROL )
       return Type::CONTROL;
   }
   return Type::TOP;             // All paths dead?  Then so are we
 }
 //------------------------------Identity---------------------------------------
 // Check for Region being Identity.
 Node *RegionNode::Identity( PhaseTransform *phase ) {
   // Cannot have Region be an identity, even if it has only 1 input.
   // Phi users cannot have their Region input folded away for them,
   // since they need to select the proper data input
   return this;
 }
 //------------------------------merge_region-----------------------------------
 // If a Region flows into a Region, merge into one big happy merge.  This is
 // hard to do if there is stuff that has to happen
 static Node *merge_region(RegionNode *region, PhaseGVN *phase) {
   if( region->Opcode() != Op_Region ) // Do not do to LoopNodes
     return NULL;
   Node *progress = NULL;        // Progress flag
   PhaseIterGVN *igvn = phase->is_IterGVN();
   uint rreq = region->req();
   for( uint i = 1; i < rreq; i++ ) {
     Node *r = region->in(i);
     if( r && r->Opcode() == Op_Region && // Found a region?
         r->in(0) == r &&        // Not already collapsed?
         r != region &&          // Avoid stupid situations
         r->outcnt() == 2 ) {    // Self user and 'region' user only?
       assert(!r->as_Region()->has_phi(), "no phi users");
       if( !progress ) {         // No progress
         if (region->has_phi()) {
           return NULL;        // Only flatten if no Phi users
           // igvn->hash_delete( phi );
         }
         igvn->hash_delete( region );
         progress = region;      // Making progress
       }
       igvn->hash_delete( r );
       // Append inputs to 'r' onto 'region'
       for( uint j = 1; j < r->req(); j++ ) {
         // Move an input from 'r' to 'region'
         region->add_req(r->in(j));
         r->set_req(j, phase->C->top());
         // Update phis of 'region'
         //for( uint k = 0; k < max; k++ ) {
         //  Node *phi = region->out(k);
         //  if( phi->is_Phi() ) {
         //    phi->add_req(phi->in(i));
         //  }
         //}
         rreq++;                 // One more input to Region
       } // Found a region to merge into Region
       // Clobber pointer to the now dead 'r'
       region->set_req(i, phase->C->top());
     }
   }
   return progress;
 }
 //--------------------------------has_phi--------------------------------------
 // Helper function: Return any PhiNode that uses this region or NULL
 PhiNode* RegionNode::has_phi() const {
   for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
     Node* phi = fast_out(i);
     if (phi->is_Phi()) {   // Check for Phi users
       assert(phi->in(0) == (Node*)this, "phi uses region only via in(0)");
       return phi->as_Phi();  // this one is good enough
     }
   }
   return NULL;
 }
 //-----------------------------has_unique_phi----------------------------------
 // Helper function: Return the only PhiNode that uses this region or NULL
 PhiNode* RegionNode::has_unique_phi() const {
   // Check that only one use is a Phi
   PhiNode* only_phi = NULL;
   for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
     Node* phi = fast_out(i);
     if (phi->is_Phi()) {   // Check for Phi users
       assert(phi->in(0) == (Node*)this, "phi uses region only via in(0)");
       if (only_phi == NULL) {
         only_phi = phi->as_Phi();
       } else {
         return NULL;  // multiple phis
       }
     }
   }
   return only_phi;
 }
 //------------------------------check_phi_clipping-----------------------------
 // Helper function for RegionNode's identification of FP clipping
 // Check inputs to the Phi
 static bool check_phi_clipping( PhiNode *phi, ConNode * &min, uint &min_idx, ConNode * &max, uint &max_idx, Node * &val, uint &val_idx ) {
   min     = NULL;
   max     = NULL;
   val     = NULL;
   min_idx = 0;
   max_idx = 0;
   val_idx = 0;
   uint  phi_max = phi->req();
   if( phi_max == 4 ) {
     for( uint j = 1; j < phi_max; ++j ) {
       Node *n = phi->in(j);
       int opcode = n->Opcode();
       switch( opcode ) {
       case Op_ConI:
         {
           if( min == NULL ) {
             min     = n->Opcode() == Op_ConI ? (ConNode*)n : NULL;
             min_idx = j;
           } else {
             max     = n->Opcode() == Op_ConI ? (ConNode*)n : NULL;
             max_idx = j;
             if( min->get_int() > max->get_int() ) {
               // Swap min and max
               ConNode *temp;
               uint     temp_idx;
               temp     = min;     min     = max;     max     = temp;
               temp_idx = min_idx; min_idx = max_idx; max_idx = temp_idx;
             }
           }
         }
         break;
       default:
         {
           val = n;
           val_idx = j;
         }
         break;
       }
     }
   }
   return ( min && max && val && (min->get_int() <= 0) && (max->get_int() >=0) );
 }
 //------------------------------check_if_clipping------------------------------
 // Helper function for RegionNode's identification of FP clipping
 // Check that inputs to Region come from two IfNodes,
 //
 //            If
 //      False    True
 //       If        |
 //  False  True    |
 //    |      |     |
 //  RegionNode_inputs
 //
 static bool check_if_clipping( const RegionNode *region, IfNode * &bot_if, IfNode * &top_if ) {
   top_if = NULL;
   bot_if = NULL;
   // Check control structure above RegionNode for (if  ( if  ) )
   Node *in1 = region->in(1);
   Node *in2 = region->in(2);
   Node *in3 = region->in(3);
   // Check that all inputs are projections
   if( in1->is_Proj() && in2->is_Proj() && in3->is_Proj() ) {
     Node *in10 = in1->in(0);
     Node *in20 = in2->in(0);
     Node *in30 = in3->in(0);
     // Check that #1 and #2 are ifTrue and ifFalse from same If
     if( in10 != NULL && in10->is_If() &&
         in20 != NULL && in20->is_If() &&
         in30 != NULL && in30->is_If() && in10 == in20 &&
         (in1->Opcode() != in2->Opcode()) ) {
       Node  *in100 = in10->in(0);
       Node *in1000 = (in100 != NULL && in100->is_Proj()) ? in100->in(0) : NULL;
       // Check that control for in10 comes from other branch of IF from in3
       if( in1000 != NULL && in1000->is_If() &&
           in30 == in1000 && (in3->Opcode() != in100->Opcode()) ) {
         // Control pattern checks
         top_if = (IfNode*)in1000;
         bot_if = (IfNode*)in10;
       }
     }
   }
   return (top_if != NULL);
 }
 //------------------------------check_convf2i_clipping-------------------------
 // Helper function for RegionNode's identification of FP clipping
 // Verify that the value input to the phi comes from "ConvF2I; LShift; RShift"
 static bool check_convf2i_clipping( PhiNode *phi, uint idx, ConvF2INode * &convf2i, Node *min, Node *max) {
   convf2i = NULL;
   // Check for the RShiftNode
   Node *rshift = phi->in(idx);
   assert( rshift, "Previous checks ensure phi input is present");
   if( rshift->Opcode() != Op_RShiftI )  { return false; }
   // Check for the LShiftNode
   Node *lshift = rshift->in(1);
   assert( lshift, "Previous checks ensure phi input is present");
   if( lshift->Opcode() != Op_LShiftI )  { return false; }
   // Check for the ConvF2INode
   Node *conv = lshift->in(1);
   if( conv->Opcode() != Op_ConvF2I ) { return false; }
   // Check that shift amounts are only to get sign bits set after F2I
   jint max_cutoff     = max->get_int();
   jint min_cutoff     = min->get_int();
   jint left_shift     = lshift->in(2)->get_int();
   jint right_shift    = rshift->in(2)->get_int();
   jint max_post_shift = nth_bit(BitsPerJavaInteger - left_shift - 1);
   if( left_shift != right_shift ||
 > left_shift || left_shift >= BitsPerJavaInteger ||
       max_post_shift < max_cutoff ||
       max_post_shift < -min_cutoff ) {
     // Shifts are necessary but current transformation eliminates them
     return false;
   }
   // OK to return the result of ConvF2I without shifting
   convf2i = (ConvF2INode*)conv;
   return true;
 }
 //------------------------------check_compare_clipping-------------------------
 // Helper function for RegionNode's identification of FP clipping
 static bool check_compare_clipping( bool less_than, IfNode *iff, ConNode *limit, Node * & input ) {
   Node *i1 = iff->in(1);
   if ( !i1->is_Bool() ) { return false; }
   BoolNode *bool1 = i1->as_Bool();
   if(       less_than && bool1->_test._test != BoolTest::le ) { return false; }
   else if( !less_than && bool1->_test._test != BoolTest::lt ) { return false; }
   const Node *cmpF = bool1->in(1);
   if( cmpF->Opcode() != Op_CmpF )      { return false; }
   // Test that the float value being compared against
   // is equivalent to the int value used as a limit
   Node *nodef = cmpF->in(2);
   if( nodef->Opcode() != Op_ConF ) { return false; }
   jfloat conf = nodef->getf();
   jint   coni = limit->get_int();
   if( ((int)conf) != coni )        { return false; }
   input = cmpF->in(1);
   return true;
 }
 //------------------------------is_unreachable_region--------------------------
 // Find if the Region node is reachable from the root.
 bool RegionNode::is_unreachable_region(PhaseGVN *phase) const {
   assert(req() == 2, "");
   // First, cut the simple case of fallthrough region when NONE of
   // region's phis references itself directly or through a data node.
   uint max = outcnt();
   uint i;
   for (i = 0; i < max; i++) {
     Node* phi = raw_out(i);
     if (phi != NULL && phi->is_Phi()) {
       assert(phase->eqv(phi->in(0), this) && phi->req() == 2, "");
       if (phi->outcnt() == 0)
         continue; // Safe case - no loops
       if (phi->outcnt() == 1) {
         Node* u = phi->raw_out(0);
         // Skip if only one use is an other Phi or Call or Uncommon trap.
         // It is safe to consider this case as fallthrough.
         if (u != NULL && (u->is_Phi() || u->is_CFG()))
           continue;
       }
       // Check when phi references itself directly or through an other node.
       if (phi->as_Phi()->simple_data_loop_check(phi->in(1)) >= PhiNode::Unsafe)
         break; // Found possible unsafe data loop.
     }
   }
   if (i >= max)
     return false; // An unsafe case was NOT found - don't need graph walk.
   // Unsafe case - check if the Region node is reachable from root.
   ResourceMark rm;
   Arena *a = Thread::current()->resource_area();
   Node_List nstack(a);
   VectorSet visited(a);
   // Mark all control nodes reachable from root outputs
   Node *n = (Node*)phase->C->root();
   nstack.push(n);
   visited.set(n->_idx);
   while (nstack.size() != 0) {
     n = nstack.pop();
     uint max = n->outcnt();
     for (uint i = 0; i < max; i++) {
       Node* m = n->raw_out(i);
       if (m != NULL && m->is_CFG()) {
         if (phase->eqv(m, this)) {
           return false; // We reached the Region node - it is not dead.
         }
         if (!visited.test_set(m->_idx))
           nstack.push(m);
       }
     }
   }
   return true; // The Region node is unreachable - it is dead.
 }
 bool RegionNode::try_clean_mem_phi(PhaseGVN *phase) {
   // Incremental inlining + PhaseStringOpts sometimes produce:
   //
   // cmpP with 1 top input
   //           |
   //          If
   //         /  \
   //   IfFalse  IfTrue  /- Some Node
   //         \  /      /    /
   //        Region    / /-MergeMem
   //             \---Phi
   //
   //
   // It's expected by PhaseStringOpts that the Region goes away and is
   // replaced by If's control input but because there's still a Phi,
   // the Region stays in the graph. The top input from the cmpP is
   // propagated forward and a subgraph that is useful goes away. The
   // code below replaces the Phi with the MergeMem so that the Region
   // is simplified.
   PhiNode* phi = has_unique_phi();
   if (phi && phi->type() == Type::MEMORY && req() == 3 && phi->is_diamond_phi(true)) {
     MergeMemNode* m = NULL;
     assert(phi->req() == 3, "same as region");
     for (uint i = 1; i < 3; ++i) {
       Node *mem = phi->in(i);
       if (mem && mem->is_MergeMem() && in(i)->outcnt() == 1) {
         // Nothing is control-dependent on path #i except the region itself.
         m = mem->as_MergeMem();
         uint j = 3 - i;
         Node* other = phi->in(j);
         if (other && other == m->base_memory()) {
           // m is a successor memory to other, and is not pinned inside the diamond, so push it out.
           // This will allow the diamond to collapse completely.
           phase->is_IterGVN()->replace_node(phi, m);
           return true;
         }
       }
     }
   }
   return false;
 }
 //------------------------------Ideal------------------------------------------
 // Return a node which is more "ideal" than the current node.  Must preserve
 // the CFG, but we can still strip out dead paths.
 Node *RegionNode::Ideal(PhaseGVN *phase, bool can_reshape) {
   if( !can_reshape && !in(0) ) return NULL;     // Already degraded to a Copy
   assert(!in(0) || !in(0)->is_Root(), "not a specially hidden merge");
   // Check for RegionNode with no Phi users and both inputs come from either
   // arm of the same IF.  If found, then the control-flow split is useless.
   bool has_phis = false;
   if (can_reshape) {            // Need DU info to check for Phi users
     has_phis = (has_phi() != NULL);       // Cache result
     if (has_phis && try_clean_mem_phi(phase)) {
       has_phis = false;
     }
     if (!has_phis) {            // No Phi users?  Nothing merging?
       for (uint i = 1; i < req()-1; i++) {
         Node *if1 = in(i);
         if( !if1 ) continue;
         Node *iff = if1->in(0);
         if( !iff || !iff->is_If() ) continue;
         for( uint j=i+1; j<req(); j++ ) {
           if( in(j) && in(j)->in(0) == iff &&
               if1->Opcode() != in(j)->Opcode() ) {
             // Add the IF Projections to the worklist. They (and the IF itself)
             // will be eliminated if dead.
             phase->is_IterGVN()->add_users_to_worklist(iff);
             set_req(i, iff->in(0));// Skip around the useless IF diamond
             set_req(j, NULL);
             return this;      // Record progress
           }
         }
       }
     }
   }
   // Remove TOP or NULL input paths. If only 1 input path remains, this Region
   // degrades to a copy.
   bool add_to_worklist = false;
   int cnt = 0;                  // Count of values merging
   DEBUG_ONLY( int cnt_orig = req(); ) // Save original inputs count
   int del_it = 0;               // The last input path we delete
   // For all inputs...
   for( uint i=1; i<req(); ++i ){// For all paths in
     Node *n = in(i);            // Get the input
     if( n != NULL ) {
       // Remove useless control copy inputs
       if( n->is_Region() && n->as_Region()->is_copy() ) {
         set_req(i, n->nonnull_req());
         i--;
         continue;
       }
       if( n->is_Proj() ) {      // Remove useless rethrows
         Node *call = n->in(0);
         if (call->is_Call() && call->as_Call()->entry_point() == OptoRuntime::rethrow_stub()) {
           set_req(i, call->in(0));
           i--;
           continue;
         }
       }
       if( phase->type(n) == Type::TOP ) {
         set_req(i, NULL);       // Ignore TOP inputs
         i--;
         continue;
       }
       cnt++;                    // One more value merging
     } else if (can_reshape) {   // Else found dead path with DU info
       PhaseIterGVN *igvn = phase->is_IterGVN();
       del_req(i);               // Yank path from self
       del_it = i;
       uint max = outcnt();
       DUIterator j;
       bool progress = true;
       while(progress) {         // Need to establish property over all users
         progress = false;
         for (j = outs(); has_out(j); j++) {
           Node *n = out(j);
           if( n->req() != req() && n->is_Phi() ) {
             assert( n->in(0) == this, "" );
             igvn->hash_delete(n); // Yank from hash before hacking edges
             n->set_req_X(i,NULL,igvn);// Correct DU info
             n->del_req(i);        // Yank path from Phis
             if( max != outcnt() ) {
               progress = true;
               j = refresh_out_pos(j);
               max = outcnt();
             }
           }
         }
       }
       add_to_worklist = true;
       i--;
     }
   }
   if (can_reshape && cnt == 1) {
     // Is it dead loop?
     // If it is LoopNopde it had 2 (+1 itself) inputs and
     // one of them was cut. The loop is dead if it was EntryContol.
     // Loop node may have only one input because entry path
     // is removed in PhaseIdealLoop::Dominators().
     assert(!this->is_Loop() || cnt_orig <= 3, "Loop node should have 3 or less inputs");
     if (this->is_Loop() && (del_it == LoopNode::EntryControl ||
                             del_it == 0 && is_unreachable_region(phase)) ||
        !this->is_Loop() && has_phis && is_unreachable_region(phase)) {
       // Yes,  the region will be removed during the next step below.
       // Cut the backedge input and remove phis since no data paths left.
       // We don't cut outputs to other nodes here since we need to put them
       // on the worklist.
       del_req(1);
       cnt = 0;
       assert( req() == 1, "no more inputs expected" );
       uint max = outcnt();
       bool progress = true;
       Node *top = phase->C->top();
       PhaseIterGVN *igvn = phase->is_IterGVN();
       DUIterator j;
       while(progress) {
         progress = false;
         for (j = outs(); has_out(j); j++) {
           Node *n = out(j);
           if( n->is_Phi() ) {
             assert( igvn->eqv(n->in(0), this), "" );
             assert( n->req() == 2 &&  n->in(1) != NULL, "Only one data input expected" );
             // Break dead loop data path.
             // Eagerly replace phis with top to avoid phis copies generation.
             igvn->replace_node(n, top);
             if( max != outcnt() ) {
               progress = true;
               j = refresh_out_pos(j);
               max = outcnt();
             }
           }
         }
       }
       add_to_worklist = true;
     }
   }
   if (add_to_worklist) {
     phase->is_IterGVN()->add_users_to_worklist(this); // Revisit collapsed Phis
   }
   if( cnt <= 1 ) {              // Only 1 path in?
     set_req(0, NULL);           // Null control input for region copy
     if( cnt == 0 && !can_reshape) { // Parse phase - leave the node as it is.
       // No inputs or all inputs are NULL.
       return NULL;
     } else if (can_reshape) {   // Optimization phase - remove the node
       PhaseIterGVN *igvn = phase->is_IterGVN();
       Node *parent_ctrl;
       if( cnt == 0 ) {
         assert( req() == 1, "no inputs expected" );
         // During IGVN phase such region will be subsumed by TOP node
         // so region's phis will have TOP as control node.
         // Kill phis here to avoid it. PhiNode::is_copy() will be always false.
         // Also set other user's input to top.
         parent_ctrl = phase->C->top();
       } else {
         // The fallthrough case since we already checked dead loops above.
         parent_ctrl = in(1);
         assert(parent_ctrl != NULL, "Region is a copy of some non-null control");
         assert(!igvn->eqv(parent_ctrl, this), "Close dead loop");
       }
       if (!add_to_worklist)
         igvn->add_users_to_worklist(this); // Check for further allowed opts
       for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
         Node* n = last_out(i);
         igvn->hash_delete(n); // Remove from worklist before modifying edges
         if( n->is_Phi() ) {   // Collapse all Phis
           // Eagerly replace phis to avoid copies generation.
           Node* in;
           if( cnt == 0 ) {
             assert( n->req() == 1, "No data inputs expected" );
             in = parent_ctrl; // replaced by top
           } else {
             assert( n->req() == 2 &&  n->in(1) != NULL, "Only one data input expected" );
             in = n->in(1);               // replaced by unique input
             if( n->as_Phi()->is_unsafe_data_reference(in) )
               in = phase->C->top();      // replaced by top
           }
           igvn->replace_node(n, in);
         }
         else if( n->is_Region() ) { // Update all incoming edges
           assert( !igvn->eqv(n, this), "Must be removed from DefUse edges");
           uint uses_found = 0;
           for( uint k=1; k < n->req(); k++ ) {
             if( n->in(k) == this ) {
               n->set_req(k, parent_ctrl);
               uses_found++;
             }
           }
           if( uses_found > 1 ) { // (--i) done at the end of the loop.
             i -= (uses_found - 1);
           }
         }
         else {
           assert( igvn->eqv(n->in(0), this), "Expect RegionNode to be control parent");
           n->set_req(0, parent_ctrl);
         }
 #ifdef ASSERT
         for( uint k=0; k < n->req(); k++ ) {
           assert( !igvn->eqv(n->in(k), this), "All uses of RegionNode should be gone");
         }
 #endif
       }
       // Remove the RegionNode itself from DefUse info
       igvn->remove_dead_node(this);
       return NULL;
     }
     return this;                // Record progress
   }
   // If a Region flows into a Region, merge into one big happy merge.
   if (can_reshape) {
     Node *m = merge_region(this, phase);
     if (m != NULL)  return m;
   }
   // Check if this region is the root of a clipping idiom on floats
   if( ConvertFloat2IntClipping && can_reshape && req() == 4 ) {
     // Check that only one use is a Phi and that it simplifies to two constants +
     PhiNode* phi = has_unique_phi();
     if (phi != NULL) {          // One Phi user
       // Check inputs to the Phi
       ConNode *min;
       ConNode *max;
       Node    *val;
       uint     min_idx;
       uint     max_idx;
       uint     val_idx;
       if( check_phi_clipping( phi, min, min_idx, max, max_idx, val, val_idx )  ) {
         IfNode *top_if;
         IfNode *bot_if;
         if( check_if_clipping( this, bot_if, top_if ) ) {
           // Control pattern checks, now verify compares
           Node   *top_in = NULL;   // value being compared against
           Node   *bot_in = NULL;
           if( check_compare_clipping( true,  bot_if, min, bot_in ) &&
               check_compare_clipping( false, top_if, max, top_in ) ) {
             if( bot_in == top_in ) {
               PhaseIterGVN *gvn = phase->is_IterGVN();
               assert( gvn != NULL, "Only had DefUse info in IterGVN");
               // Only remaining check is that bot_in == top_in == (Phi's val + mods)
               // Check for the ConvF2INode
               ConvF2INode *convf2i;
               if( check_convf2i_clipping( phi, val_idx, convf2i, min, max ) &&
                 convf2i->in(1) == bot_in ) {
                 // Matched pattern, including LShiftI; RShiftI, replace with integer compares
                 // max test
                 Node *cmp   = gvn->register_new_node_with_optimizer(new (phase->C) CmpINode( convf2i, min ));
                 Node *boo   = gvn->register_new_node_with_optimizer(new (phase->C) BoolNode( cmp, BoolTest::lt ));
                 IfNode *iff = (IfNode*)gvn->register_new_node_with_optimizer(new (phase->C) IfNode( top_if->in(0), boo, PROB_UNLIKELY_MAG(5), top_if->_fcnt ));
                 Node *if_min= gvn->register_new_node_with_optimizer(new (phase->C) IfTrueNode (iff));
                 Node *ifF   = gvn->register_new_node_with_optimizer(new (phase->C) IfFalseNode(iff));
                 // min test
                 cmp         = gvn->register_new_node_with_optimizer(new (phase->C) CmpINode( convf2i, max ));
                 boo         = gvn->register_new_node_with_optimizer(new (phase->C) BoolNode( cmp, BoolTest::gt ));
                 iff         = (IfNode*)gvn->register_new_node_with_optimizer(new (phase->C) IfNode( ifF, boo, PROB_UNLIKELY_MAG(5), bot_if->_fcnt ));
                 Node *if_max= gvn->register_new_node_with_optimizer(new (phase->C) IfTrueNode (iff));
                 ifF         = gvn->register_new_node_with_optimizer(new (phase->C) IfFalseNode(iff));
                 // update input edges to region node
                 set_req_X( min_idx, if_min, gvn );
                 set_req_X( max_idx, if_max, gvn );
                 set_req_X( val_idx, ifF,    gvn );
                 // remove unnecessary 'LShiftI; RShiftI' idiom
                 gvn->hash_delete(phi);
                 phi->set_req_X( val_idx, convf2i, gvn );
                 gvn->hash_find_insert(phi);
                 // Return transformed region node
                 return this;
               }
             }
           }
         }
       }
     }
   }
   return NULL;
 }
 const RegMask &RegionNode::out_RegMask() const {
   return RegMask::Empty;
 }
 // Find the one non-null required input.  RegionNode only
 Node *Node::nonnull_req() const {
   assert( is_Region(), "" );
   for( uint i = 1; i < _cnt; i++ )
     if( in(i) )
       return in(i);
   ShouldNotReachHere();
   return NULL;
 }
 //=============================================================================
 // note that these functions assume that the _adr_type field is flattened
 uint PhiNode::hash() const {
   const Type* at = _adr_type;
   return TypeNode::hash() + (at ? at->hash() : 0);
 }
 uint PhiNode::cmp( const Node &n ) const {
   return TypeNode::cmp(n) && _adr_type == ((PhiNode&)n)._adr_type;
 }
 static inline
 const TypePtr* flatten_phi_adr_type(const TypePtr* at) {
   if (at == NULL || at == TypePtr::BOTTOM)  return at;
   return Compile::current()->alias_type(at)->adr_type();
 }
 //----------------------------make---------------------------------------------
 // create a new phi with edges matching r and set (initially) to x
 PhiNode* PhiNode::make(Node* r, Node* x, const Type *t, const TypePtr* at) {
   uint preds = r->req();   // Number of predecessor paths
   assert(t != Type::MEMORY || at == flatten_phi_adr_type(at), "flatten at");
   PhiNode* p = new (Compile::current()) PhiNode(r, t, at);
   for (uint j = 1; j < preds; j++) {
     // Fill in all inputs, except those which the region does not yet have
     if (r->in(j) != NULL)
       p->init_req(j, x);
   }
   return p;
 }
 PhiNode* PhiNode::make(Node* r, Node* x) {
   const Type*    t  = x->bottom_type();
   const TypePtr* at = NULL;
   if (t == Type::MEMORY)  at = flatten_phi_adr_type(x->adr_type());
   return make(r, x, t, at);
 }
 PhiNode* PhiNode::make_blank(Node* r, Node* x) {
   const Type*    t  = x->bottom_type();
   const TypePtr* at = NULL;
   if (t == Type::MEMORY)  at = flatten_phi_adr_type(x->adr_type());
   return new (Compile::current()) PhiNode(r, t, at);
 }
 //------------------------slice_memory-----------------------------------------
 // create a new phi with narrowed memory type
 PhiNode* PhiNode::slice_memory(const TypePtr* adr_type) const {
   PhiNode* mem = (PhiNode*) clone();
   *(const TypePtr**)&mem->_adr_type = adr_type;
   // convert self-loops, or else we get a bad graph
   for (uint i = 1; i < req(); i++) {
     if ((const Node*)in(i) == this)  mem->set_req(i, mem);
   }
   mem->verify_adr_type();
   return mem;
 }
 //------------------------split_out_instance-----------------------------------
 // Split out an instance type from a bottom phi.
 PhiNode* PhiNode::split_out_instance(const TypePtr* at, PhaseIterGVN *igvn) const {
   const TypeOopPtr *t_oop = at->isa_oopptr();
   assert(t_oop != NULL && t_oop->is_known_instance(), "expecting instance oopptr");
   const TypePtr *t = adr_type();
   assert(type() == Type::MEMORY &&
          (t == TypePtr::BOTTOM || t == TypeRawPtr::BOTTOM ||
           t->isa_oopptr() && !t->is_oopptr()->is_known_instance() &&
           t->is_oopptr()->cast_to_exactness(true)
            ->is_oopptr()->cast_to_ptr_type(t_oop->ptr())
            ->is_oopptr()->cast_to_instance_id(t_oop->instance_id()) == t_oop),
          "bottom or raw memory required");
   // Check if an appropriate node already exists.
   Node *region = in(0);
   for (DUIterator_Fast kmax, k = region->fast_outs(kmax); k < kmax; k++) {
     Node* use = region->fast_out(k);
     if( use->is_Phi()) {
       PhiNode *phi2 = use->as_Phi();
       if (phi2->type() == Type::MEMORY && phi2->adr_type() == at) {
         return phi2;
       }
     }
   }
   Compile *C = igvn->C;
   Arena *a = Thread::current()->resource_area();
   Node_Array node_map = new Node_Array(a);
   Node_Stack stack(a, C->unique() >> 4);
   PhiNode *nphi = slice_memory(at);
   igvn->register_new_node_with_optimizer( nphi );
   node_map.map(_idx, nphi);
   stack.push((Node *)this, 1);
   while(!stack.is_empty()) {
     PhiNode *ophi = stack.node()->as_Phi();
     uint i = stack.index();
     assert(i >= 1, "not control edge");
     stack.pop();
     nphi = node_map[ophi->_idx]->as_Phi();
     for (; i < ophi->req(); i++) {
       Node *in = ophi->in(i);
       if (in == NULL || igvn->type(in) == Type::TOP)
         continue;
       Node *opt = MemNode::optimize_simple_memory_chain(in, t_oop, NULL, igvn);
       PhiNode *optphi = opt->is_Phi() ? opt->as_Phi() : NULL;
       if (optphi != NULL && optphi->adr_type() == TypePtr::BOTTOM) {
         opt = node_map[optphi->_idx];
         if (opt == NULL) {
           stack.push(ophi, i);
           nphi = optphi->slice_memory(at);
           igvn->register_new_node_with_optimizer( nphi );
           node_map.map(optphi->_idx, nphi);
           ophi = optphi;
           i = 0; // will get incremented at top of loop
           continue;
         }
       }
       nphi->set_req(i, opt);
     }
   }
   return nphi;
 }
 //------------------------verify_adr_type--------------------------------------
 #ifdef ASSERT
 void PhiNode::verify_adr_type(VectorSet& visited, const TypePtr* at) const {
   if (visited.test_set(_idx))  return;  //already visited
   // recheck constructor invariants:
   verify_adr_type(false);
   // recheck local phi/phi consistency:
   assert(_adr_type == at || _adr_type == TypePtr::BOTTOM,
          "adr_type must be consistent across phi nest");
   // walk around
   for (uint i = 1; i < req(); i++) {
     Node* n = in(i);
     if (n == NULL)  continue;
     const Node* np = in(i);
     if (np->is_Phi()) {
       np->as_Phi()->verify_adr_type(visited, at);
     } else if (n->bottom_type() == Type::TOP
                || (n->is_Mem() && n->in(MemNode::Address)->bottom_type() == Type::TOP)) {
       // ignore top inputs
     } else {
       const TypePtr* nat = flatten_phi_adr_type(n->adr_type());
       // recheck phi/non-phi consistency at leaves:
       assert((nat != NULL) == (at != NULL), "");
       assert(nat == at || nat == TypePtr::BOTTOM,
              "adr_type must be consistent at leaves of phi nest");
     }
   }
 }
 // Verify a whole nest of phis rooted at this one.
 void PhiNode::verify_adr_type(bool recursive) const {
   if (is_error_reported())  return;  // muzzle asserts when debugging an error
   if (Node::in_dump())      return;  // muzzle asserts when printing
   assert((_type == Type::MEMORY) == (_adr_type != NULL), "adr_type for memory phis only");
   if (!VerifyAliases)       return;  // verify thoroughly only if requested
   assert(_adr_type == flatten_phi_adr_type(_adr_type),
          "Phi::adr_type must be pre-normalized");
   if (recursive) {
     VectorSet visited(Thread::current()->resource_area());
     verify_adr_type(visited, _adr_type);
   }
 }
 #endif
 //------------------------------Value------------------------------------------
 // Compute the type of the PhiNode
 const Type *PhiNode::Value( PhaseTransform *phase ) const {
   Node *r = in(0);              // RegionNode
   if( !r )                      // Copy or dead
     return in(1) ? phase->type(in(1)) : Type::TOP;
   // Note: During parsing, phis are often transformed before their regions.
   // This means we have to use type_or_null to defend against untyped regions.
   if( phase->type_or_null(r) == Type::TOP )  // Dead code?
     return Type::TOP;
   // Check for trip-counted loop.  If so, be smarter.
   CountedLoopNode *l = r->is_CountedLoop() ? r->as_CountedLoop() : NULL;
   if( l && l->can_be_counted_loop(phase) &&
       ((const Node*)l->phi() == this) ) { // Trip counted loop!
     // protect against init_trip() or limit() returning NULL
     const Node *init   = l->init_trip();
     const Node *limit  = l->limit();
     if( init != NULL && limit != NULL && l->stride_is_con() ) {
       const TypeInt *lo = init ->bottom_type()->isa_int();
       const TypeInt *hi = limit->bottom_type()->isa_int();
       if( lo && hi ) {            // Dying loops might have TOP here
         int stride = l->stride_con();
         if( stride < 0 ) {          // Down-counter loop
           const TypeInt *tmp = lo; lo = hi; hi = tmp;
           stride = -stride;
         }
         if( lo->_hi < hi->_lo )     // Reversed endpoints are well defined :-(
           return TypeInt::make(lo->_lo,hi->_hi,3);
       }
     }
   }
   // Until we have harmony between classes and interfaces in the type
   // lattice, we must tread carefully around phis which implicitly
   // convert the one to the other.
   const TypePtr* ttp = _type->make_ptr();
   const TypeInstPtr* ttip = (ttp != NULL) ? ttp->isa_instptr() : NULL;
   const TypeKlassPtr* ttkp = (ttp != NULL) ? ttp->isa_klassptr() : NULL;
   bool is_intf = false;
   if (ttip != NULL) {
     ciKlass* k = ttip->klass();
     if (k->is_loaded() && k->is_interface())
       is_intf = true;
   }
   if (ttkp != NULL) {
     ciKlass* k = ttkp->klass();
     if (k->is_loaded() && k->is_interface())
       is_intf = true;
   }
   // Default case: merge all inputs
   const Type *t = Type::TOP;        // Merged type starting value
   for (uint i = 1; i < req(); ++i) {// For all paths in
     // Reachable control path?
     if (r->in(i) && phase->type(r->in(i)) == Type::CONTROL) {
       const Type* ti = phase->type(in(i));
       // We assume that each input of an interface-valued Phi is a true
       // subtype of that interface.  This might not be true of the meet
       // of all the input types.  The lattice is not distributive in
       // such cases.  Ward off asserts in type.cpp by refusing to do
       // meets between interfaces and proper classes.
       const TypePtr* tip = ti->make_ptr();
       const TypeInstPtr* tiip = (tip != NULL) ? tip->isa_instptr() : NULL;
       if (tiip) {
         bool ti_is_intf = false;
         ciKlass* k = tiip->klass();
         if (k->is_loaded() && k->is_interface())
           ti_is_intf = true;
         if (is_intf != ti_is_intf)
           { t = _type; break; }
       }
       t = t->meet_speculative(ti);
     }
   }
   // The worst-case type (from ciTypeFlow) should be consistent with "t".
   // That is, we expect that "t->higher_equal(_type)" holds true.
   // There are various exceptions:
   // - Inputs which are phis might in fact be widened unnecessarily.
   //   For example, an input might be a widened int while the phi is a short.
   // - Inputs might be BotPtrs but this phi is dependent on a null check,
   //   and postCCP has removed the cast which encodes the result of the check.
   // - The type of this phi is an interface, and the inputs are classes.
   // - Value calls on inputs might produce fuzzy results.
   //   (Occurrences of this case suggest improvements to Value methods.)
   //
   // It is not possible to see Type::BOTTOM values as phi inputs,
   // because the ciTypeFlow pre-pass produces verifier-quality types.
   const Type* ft = t->filter_speculative(_type);  // Worst case type
 #ifdef ASSERT
   // The following logic has been moved into TypeOopPtr::filter.
   const Type* jt = t->join_speculative(_type);
   if( jt->empty() ) {           // Emptied out???
     // Check for evil case of 't' being a class and '_type' expecting an
     // interface.  This can happen because the bytecodes do not contain
     // enough type info to distinguish a Java-level interface variable
     // from a Java-level object variable.  If we meet 2 classes which
     // both implement interface I, but their meet is at 'j/l/O' which
     // doesn't implement I, we have no way to tell if the result should
     // be 'I' or 'j/l/O'.  Thus we'll pick 'j/l/O'.  If this then flows
     // into a Phi which "knows" it's an Interface type we'll have to
     // uplift the type.
     if( !t->empty() && ttip && ttip->is_loaded() && ttip->klass()->is_interface() )
       { assert(ft == _type, ""); } // Uplift to interface
     else if( !t->empty() && ttkp && ttkp->is_loaded() && ttkp->klass()->is_interface() )
       { assert(ft == _type, ""); } // Uplift to interface
     // Otherwise it's something stupid like non-overlapping int ranges
     // found on dying counted loops.
     else
       { assert(ft == Type::TOP, ""); } // Canonical empty value
   }
   else {
     // If we have an interface-typed Phi and we narrow to a class type, the join
     // should report back the class.  However, if we have a J/L/Object
     // class-typed Phi and an interface flows in, it's possible that the meet &
     // join report an interface back out.  This isn't possible but happens
     // because the type system doesn't interact well with interfaces.
     const TypePtr *jtp = jt->make_ptr();
     const TypeInstPtr *jtip = (jtp != NULL) ? jtp->isa_instptr() : NULL;
     const TypeKlassPtr *jtkp = (jtp != NULL) ? jtp->isa_klassptr() : NULL;
     if( jtip && ttip ) {
       if( jtip->is_loaded() &&  jtip->klass()->is_interface() &&
           ttip->is_loaded() && !ttip->klass()->is_interface() ) {
         // Happens in a CTW of rt.jar, 320-341, no extra flags
         assert(ft == ttip->cast_to_ptr_type(jtip->ptr()) ||
                ft->isa_narrowoop() && ft->make_ptr() == ttip->cast_to_ptr_type(jtip->ptr()), "");
         jt = ft;
       }
     }
     if( jtkp && ttkp ) {
       if( jtkp->is_loaded() &&  jtkp->klass()->is_interface() &&
           !jtkp->klass_is_exact() && // Keep exact interface klass (6894807)
           ttkp->is_loaded() && !ttkp->klass()->is_interface() ) {
         assert(ft == ttkp->cast_to_ptr_type(jtkp->ptr()) ||
                ft->isa_narrowklass() && ft->make_ptr() == ttkp->cast_to_ptr_type(jtkp->ptr()), "");
         jt = ft;
       }
     }
     if (jt != ft && jt->base() == ft->base()) {
       if (jt->isa_int() &&
           jt->is_int()->_lo == ft->is_int()->_lo &&
           jt->is_int()->_hi == ft->is_int()->_hi)
         jt = ft;
       if (jt->isa_long() &&
           jt->is_long()->_lo == ft->is_long()->_lo &&
           jt->is_long()->_hi == ft->is_long()->_hi)
         jt = ft;
     }
     if (jt != ft) {
       tty->print("merge type:  "); t->dump(); tty->cr();
       tty->print("kill type:   "); _type->dump(); tty->cr();
       tty->print("join type:   "); jt->dump(); tty->cr();
       tty->print("filter type: "); ft->dump(); tty->cr();
     }
     assert(jt == ft, "");
   }
 #endif //ASSERT
   // Deal with conversion problems found in data loops.
   ft = phase->saturate(ft, phase->type_or_null(this), _type);
   return ft;
 }
 //------------------------------is_diamond_phi---------------------------------
 // Does this Phi represent a simple well-shaped diamond merge?  Return the
 // index of the true path or 0 otherwise.
 // If check_control_only is true, do not inspect the If node at the
 // top, and return -1 (not an edge number) on success.
 int PhiNode::is_diamond_phi(bool check_control_only) const {
   // Check for a 2-path merge
   Node *region = in(0);
   if( !region ) return 0;
   if( region->req() != 3 ) return 0;
   if(         req() != 3 ) return 0;
   // Check that both paths come from the same If
   Node *ifp1 = region->in(1);
   Node *ifp2 = region->in(2);
   if( !ifp1 || !ifp2 ) return 0;
   Node *iff = ifp1->in(0);
   if( !iff || !iff->is_If() ) return 0;
   if( iff != ifp2->in(0) ) return 0;
   if (check_control_only)  return -1;
   // Check for a proper bool/cmp
   const Node *b = iff->in(1);
   if( !b->is_Bool() ) return 0;
   const Node *cmp = b->in(1);
   if( !cmp->is_Cmp() ) return 0;
   // Check for branching opposite expected
   if( ifp2->Opcode() == Op_IfTrue ) {
     assert( ifp1->Opcode() == Op_IfFalse, "" );
     return 2;
   } else {
     assert( ifp1->Opcode() == Op_IfTrue, "" );
     return 1;
   }
 }
 //----------------------------check_cmove_id-----------------------------------
 // Check for CMove'ing a constant after comparing against the constant.
 // Happens all the time now, since if we compare equality vs a constant in
 // the parser, we "know" the variable is constant on one path and we force
 // it.  Thus code like "if( x==0 ) {/*EMPTY*/}" ends up inserting a
 // conditional move: "x = (x==0)?0:x;".  Yucko.  This fix is slightly more
 // general in that we don't need constants.  Since CMove's are only inserted
 // in very special circumstances, we do it here on generic Phi's.
 Node* PhiNode::is_cmove_id(PhaseTransform* phase, int true_path) {
   assert(true_path !=0, "only diamond shape graph expected");
   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
   // phi->region->if_proj->ifnode->bool->cmp
   Node*     region = in(0);
   Node*     iff    = region->in(1)->in(0);
   BoolNode* b      = iff->in(1)->as_Bool();
   Node*     cmp    = b->in(1);
   Node*     tval   = in(true_path);
   Node*     fval   = in(3-true_path);
   Node*     id     = CMoveNode::is_cmove_id(phase, cmp, tval, fval, b);
   if (id == NULL)
     return NULL;
   // Either value might be a cast that depends on a branch of 'iff'.
   // Since the 'id' value will float free of the diamond, either
   // decast or return failure.
   Node* ctl = id->in(0);
   if (ctl != NULL && ctl->in(0) == iff) {
     if (id->is_ConstraintCast()) {
       return id->in(1);
     } else {
       // Don't know how to disentangle this value.
       return NULL;
     }
   }
   return id;
 }
 //------------------------------Identity---------------------------------------
 // Check for Region being Identity.
 Node *PhiNode::Identity( PhaseTransform *phase ) {
   // Check for no merging going on
   // (There used to be special-case code here when this->region->is_Loop.
   // It would check for a tributary phi on the backedge that the main phi
   // trivially, perhaps with a single cast.  The unique_input method
   // does all this and more, by reducing such tributaries to 'this'.)
   Node* uin = unique_input(phase);
   if (uin != NULL) {
     return uin;
   }
   int true_path = is_diamond_phi();
   if (true_path != 0) {
     Node* id = is_cmove_id(phase, true_path);
     if (id != NULL)  return id;
   }
   return this;                     // No identity
 }
 //-----------------------------unique_input------------------------------------
 // Find the unique value, discounting top, self-loops, and casts.
 // Return top if there are no inputs, and self if there are multiple.
 Node* PhiNode::unique_input(PhaseTransform* phase) {
   //  1) One unique direct input, or
   //  2) some of the inputs have an intervening ConstraintCast and
   //     the type of input is the same or sharper (more specific)
   //     than the phi's type.
   //  3) an input is a self loop
   //
   //  1) input   or   2) input     or   3) input __
   //     /   \           /   \               \  /  \
   //     \   /          |    cast             phi  cast
   //      phi            \   /               /  \  /
   //                      phi               /    --
   Node* r = in(0);                      // RegionNode
   if (r == NULL)  return in(1);         // Already degraded to a Copy
   Node* uncasted_input = NULL; // The unique uncasted input (ConstraintCasts removed)
   Node* direct_input   = NULL; // The unique direct input
   for (uint i = 1, cnt = req(); i < cnt; ++i) {
     Node* rc = r->in(i);
     if (rc == NULL || phase->type(rc) == Type::TOP)
       continue;                 // ignore unreachable control path
     Node* n = in(i);
     if (n == NULL)
       continue;
     Node* un = n->uncast();
     if (un == NULL || un == this || phase->type(un) == Type::TOP) {
       continue; // ignore if top, or in(i) and "this" are in a data cycle
     }
     // Check for a unique uncasted input
     if (uncasted_input == NULL) {
       uncasted_input = un;
     } else if (uncasted_input != un) {
       uncasted_input = NodeSentinel; // no unique uncasted input
     }
     // Check for a unique direct input
     if (direct_input == NULL) {
       direct_input = n;
     } else if (direct_input != n) {
       direct_input = NodeSentinel; // no unique direct input
     }
   }
   if (direct_input == NULL) {
     return phase->C->top();        // no inputs
   }
   assert(uncasted_input != NULL,"");
   if (direct_input != NodeSentinel) {
     return direct_input;           // one unique direct input
   }
   if (uncasted_input != NodeSentinel &&
       phase->type(uncasted_input)->higher_equal(type())) {
     return uncasted_input;         // one unique uncasted input
   }
   // Nothing.
   return NULL;
 }
 //------------------------------is_x2logic-------------------------------------
 // Check for simple convert-to-boolean pattern
 // If:(C Bool) Region:(IfF IfT) Phi:(Region 0 1)
 // Convert Phi to an ConvIB.
 static Node *is_x2logic( PhaseGVN *phase, PhiNode *phi, int true_path ) {
   assert(true_path !=0, "only diamond shape graph expected");
   // Convert the true/false index into an expected 0/1 return.
   // Map 2->0 and 1->1.
   int flipped = 2-true_path;
   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
   // phi->region->if_proj->ifnode->bool->cmp
   Node *region = phi->in(0);
   Node *iff = region->in(1)->in(0);
   BoolNode *b = (BoolNode*)iff->in(1);
   const CmpNode *cmp = (CmpNode*)b->in(1);
   Node *zero = phi->in(1);
   Node *one  = phi->in(2);
   const Type *tzero = phase->type( zero );
   const Type *tone  = phase->type( one  );
   // Check for compare vs 0
   const Type *tcmp = phase->type(cmp->in(2));
   if( tcmp != TypeInt::ZERO && tcmp != TypePtr::NULL_PTR ) {
     // Allow cmp-vs-1 if the other input is bounded by 0-1
     if( !(tcmp == TypeInt::ONE && phase->type(cmp->in(1)) == TypeInt::BOOL) )
       return NULL;
     flipped = 1-flipped;        // Test is vs 1 instead of 0!
   }
   // Check for setting zero/one opposite expected
   if( tzero == TypeInt::ZERO ) {
     if( tone == TypeInt::ONE ) {
     } else return NULL;
   } else if( tzero == TypeInt::ONE ) {
     if( tone == TypeInt::ZERO ) {
       flipped = 1-flipped;
     } else return NULL;
   } else return NULL;
   // Check for boolean test backwards
   if( b->_test._test == BoolTest::ne ) {
   } else if( b->_test._test == BoolTest::eq ) {
     flipped = 1-flipped;
   } else return NULL;
   // Build int->bool conversion
   Node *n = new (phase->C) Conv2BNode( cmp->in(1) );
   if( flipped )
     n = new (phase->C) XorINode( phase->transform(n), phase->intcon(1) );
   return n;
 }
 //------------------------------is_cond_add------------------------------------
 // Check for simple conditional add pattern:  "(P < Q) ? X+Y : X;"
 // To be profitable the control flow has to disappear; there can be no other
 // values merging here.  We replace the test-and-branch with:
 // "(sgn(P-Q))&Y) + X".  Basically, convert "(P < Q)" into 0 or -1 by
 // moving the carry bit from (P-Q) into a register with 'sbb EAX,EAX'.
 // Then convert Y to 0-or-Y and finally add.
 // This is a key transform for SpecJava _201_compress.
 static Node* is_cond_add(PhaseGVN *phase, PhiNode *phi, int true_path) {
   assert(true_path !=0, "only diamond shape graph expected");
   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
   // phi->region->if_proj->ifnode->bool->cmp
   RegionNode *region = (RegionNode*)phi->in(0);
   Node *iff = region->in(1)->in(0);
   BoolNode* b = iff->in(1)->as_Bool();
   const CmpNode *cmp = (CmpNode*)b->in(1);
   // Make sure only merging this one phi here
   if (region->has_unique_phi() != phi)  return NULL;
   // Make sure each arm of the diamond has exactly one output, which we assume
   // is the region.  Otherwise, the control flow won't disappear.
   if (region->in(1)->outcnt() != 1) return NULL;
   if (region->in(2)->outcnt() != 1) return NULL;
   // Check for "(P < Q)" of type signed int
   if (b->_test._test != BoolTest::lt)  return NULL;
   if (cmp->Opcode() != Op_CmpI)        return NULL;
   Node *p = cmp->in(1);
   Node *q = cmp->in(2);
   Node *n1 = phi->in(  true_path);
   Node *n2 = phi->in(3-true_path);
   int op = n1->Opcode();
   if( op != Op_AddI           // Need zero as additive identity
       /*&&op != Op_SubI &&
       op != Op_AddP &&
       op != Op_XorI &&
       op != Op_OrI*/ )
     return NULL;
   Node *x = n2;
   Node *y = NULL;
   if( x == n1->in(1) ) {
     y = n1->in(2);
   } else if( x == n1->in(2) ) {
     y = n1->in(1);
   } else return NULL;
   // Not so profitable if compare and add are constants
   if( q->is_Con() && phase->type(q) != TypeInt::ZERO && y->is_Con() )
     return NULL;
   Node *cmplt = phase->transform( new (phase->C) CmpLTMaskNode(p,q) );
   Node *j_and   = phase->transform( new (phase->C) AndINode(cmplt,y) );
   return new (phase->C) AddINode(j_and,x);
 }
 //------------------------------is_absolute------------------------------------
 // Check for absolute value.
 static Node* is_absolute( PhaseGVN *phase, PhiNode *phi_root, int true_path) {
   assert(true_path !=0, "only diamond shape graph expected");
   int  cmp_zero_idx = 0;        // Index of compare input where to look for zero
   int  phi_x_idx = 0;           // Index of phi input where to find naked x
   // ABS ends with the merge of 2 control flow paths.
   // Find the false path from the true path. With only 2 inputs, 3 - x works nicely.
   int false_path = 3 - true_path;
   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
   // phi->region->if_proj->ifnode->bool->cmp
   BoolNode *bol = phi_root->in(0)->in(1)->in(0)->in(1)->as_Bool();
   // Check bool sense
   switch( bol->_test._test ) {
   case BoolTest::lt: cmp_zero_idx = 1; phi_x_idx = true_path;  break;
   case BoolTest::le: cmp_zero_idx = 2; phi_x_idx = false_path; break;
   case BoolTest::gt: cmp_zero_idx = 2; phi_x_idx = true_path;  break;
   case BoolTest::ge: cmp_zero_idx = 1; phi_x_idx = false_path; break;
   default:           return NULL;                              break;
   }
   // Test is next
   Node *cmp = bol->in(1);
   const Type *tzero = NULL;
   switch( cmp->Opcode() ) {
   case Op_CmpF:    tzero = TypeF::ZERO; break; // Float ABS
   case Op_CmpD:    tzero = TypeD::ZERO; break; // Double ABS
   default: return NULL;
   }
   // Find zero input of compare; the other input is being abs'd
   Node *x = NULL;
   bool flip = false;
   if( phase->type(cmp->in(cmp_zero_idx)) == tzero ) {
     x = cmp->in(3 - cmp_zero_idx);
   } else if( phase->type(cmp->in(3 - cmp_zero_idx)) == tzero ) {
     // The test is inverted, we should invert the result...
     x = cmp->in(cmp_zero_idx);
     flip = true;
   } else {
     return NULL;
   }
   // Next get the 2 pieces being selected, one is the original value
   // and the other is the negated value.
   if( phi_root->in(phi_x_idx) != x ) return NULL;
   // Check other phi input for subtract node
   Node *sub = phi_root->in(3 - phi_x_idx);
   // Allow only Sub(0,X) and fail out for all others; Neg is not OK
   if( tzero == TypeF::ZERO ) {
     if( sub->Opcode() != Op_SubF ||
         sub->in(2) != x ||
         phase->type(sub->in(1)) != tzero ) return NULL;
     x = new (phase->C) AbsFNode(x);
     if (flip) {
       x = new (phase->C) SubFNode(sub->in(1), phase->transform(x));
     }
   } else {
     if( sub->Opcode() != Op_SubD ||
         sub->in(2) != x ||
         phase->type(sub->in(1)) != tzero ) return NULL;
     x = new (phase->C) AbsDNode(x);
     if (flip) {
       x = new (phase->C) SubDNode(sub->in(1), phase->transform(x));
     }
   }
   return x;
 }
 //------------------------------split_once-------------------------------------
 // Helper for split_flow_path
 static void split_once(PhaseIterGVN *igvn, Node *phi, Node *val, Node *n, Node *newn) {
   igvn->hash_delete(n);         // Remove from hash before hacking edges
   uint j = 1;
   for (uint i = phi->req()-1; i > 0; i--) {
     if (phi->in(i) == val) {   // Found a path with val?
       // Add to NEW Region/Phi, no DU info
       newn->set_req( j++, n->in(i) );
       // Remove from OLD Region/Phi
       n->del_req(i);
     }
   }
   // Register the new node but do not transform it.  Cannot transform until the
   // entire Region/Phi conglomerate has been hacked as a single huge transform.
   igvn->register_new_node_with_optimizer( newn );
   // Now I can point to the new node.
   n->add_req(newn);
   igvn->_worklist.push(n);
 }
 //------------------------------split_flow_path--------------------------------
 // Check for merging identical values and split flow paths
 static Node* split_flow_path(PhaseGVN *phase, PhiNode *phi) {
   BasicType bt = phi->type()->basic_type();
   if( bt == T_ILLEGAL || type2size[bt] <= 0 )
     return NULL;                // Bail out on funny non-value stuff
   if( phi->req() <= 3 )         // Need at least 2 matched inputs and a
     return NULL;                // third unequal input to be worth doing
   // Scan for a constant
   uint i;
   for( i = 1; i < phi->req()-1; i++ ) {
     Node *n = phi->in(i);
     if( !n ) return NULL;
     if( phase->type(n) == Type::TOP ) return NULL;
     if( n->Opcode() == Op_ConP || n->Opcode() == Op_ConN || n->Opcode() == Op_ConNKlass )
       break;
   }
   if( i >= phi->req() )         // Only split for constants
     return NULL;
   Node *val = phi->in(i);       // Constant to split for
   uint hit = 0;                 // Number of times it occurs
   Node *r = phi->region();
   for( ; i < phi->req(); i++ ){ // Count occurrences of constant
     Node *n = phi->in(i);
     if( !n ) return NULL;
     if( phase->type(n) == Type::TOP ) return NULL;
     if( phi->in(i) == val ) {
       hit++;
       if (PhaseIdealLoop::find_predicate(r->in(i)) != NULL) {
         return NULL;            // don't split loop entry path
       }
     }
   }
   if( hit <= 1 ||               // Make sure we find 2 or more
       hit == phi->req()-1 )     // and not ALL the same value
     return NULL;
   // Now start splitting out the flow paths that merge the same value.
   // Split first the RegionNode.
   PhaseIterGVN *igvn = phase->is_IterGVN();
   RegionNode *newr = new (phase->C) RegionNode(hit+1);
   split_once(igvn, phi, val, r, newr);
   // Now split all other Phis than this one
   for (DUIterator_Fast kmax, k = r->fast_outs(kmax); k < kmax; k++) {
     Node* phi2 = r->fast_out(k);
     if( phi2->is_Phi() && phi2->as_Phi() != phi ) {
       PhiNode *newphi = PhiNode::make_blank(newr, phi2);
       split_once(igvn, phi, val, phi2, newphi);
     }
   }
   // Clean up this guy
   igvn->hash_delete(phi);
   for( i = phi->req()-1; i > 0; i-- ) {
     if( phi->in(i) == val ) {
       phi->del_req(i);
     }
   }
   phi->add_req(val);
   return phi;
 }
 //=============================================================================
 //------------------------------simple_data_loop_check-------------------------
 //  Try to determining if the phi node in a simple safe/unsafe data loop.
 //  Returns:
 // enum LoopSafety { Safe = 0, Unsafe, UnsafeLoop };
 // Safe       - safe case when the phi and it's inputs reference only safe data
 //              nodes;
 // Unsafe     - the phi and it's inputs reference unsafe data nodes but there
 //              is no reference back to the phi - need a graph walk
 //              to determine if it is in a loop;
 // UnsafeLoop - unsafe case when the phi references itself directly or through
 //              unsafe data node.
 //  Note: a safe data node is a node which could/never reference itself during
 //  GVN transformations. For now it is Con, Proj, Phi, CastPP, CheckCastPP.
 //  I mark Phi nodes as safe node not only because they can reference itself
 //  but also to prevent mistaking the fallthrough case inside an outer loop
 //  as dead loop when the phi references itselfs through an other phi.
 PhiNode::LoopSafety PhiNode::simple_data_loop_check(Node *in) const {
   // It is unsafe loop if the phi node references itself directly.
   if (in == (Node*)this)
     return UnsafeLoop; // Unsafe loop
   // Unsafe loop if the phi node references itself through an unsafe data node.
   // Exclude cases with null inputs or data nodes which could reference
   // itself (safe for dead loops).
   if (in != NULL && !in->is_dead_loop_safe()) {
     // Check inputs of phi's inputs also.
     // It is much less expensive then full graph walk.
     uint cnt = in->req();
     uint i = (in->is_Proj() && !in->is_CFG())  ? 0 : 1;
     for (; i < cnt; ++i) {
       Node* m = in->in(i);
       if (m == (Node*)this)
         return UnsafeLoop; // Unsafe loop
       if (m != NULL && !m->is_dead_loop_safe()) {
         // Check the most common case (about 30% of all cases):
         // phi->Load/Store->AddP->(ConP ConP Con)/(Parm Parm Con).
         Node *m1 = (m->is_AddP() && m->req() > 3) ? m->in(1) : NULL;
         if (m1 == (Node*)this)
           return UnsafeLoop; // Unsafe loop
         if (m1 != NULL && m1 == m->in(2) &&
             m1->is_dead_loop_safe() && m->in(3)->is_Con()) {
           continue; // Safe case
         }
         // The phi references an unsafe node - need full analysis.
         return Unsafe;
       }
     }
   }
   return Safe; // Safe case - we can optimize the phi node.
 }
 //------------------------------is_unsafe_data_reference-----------------------
 // If phi can be reached through the data input - it is data loop.
 bool PhiNode::is_unsafe_data_reference(Node *in) const {
   assert(req() > 1, "");
   // First, check simple cases when phi references itself directly or
   // through an other node.
   LoopSafety safety = simple_data_loop_check(in);
   if (safety == UnsafeLoop)
     return true;  // phi references itself - unsafe loop
   else if (safety == Safe)
     return false; // Safe case - phi could be replaced with the unique input.
   // Unsafe case when we should go through data graph to determine
   // if the phi references itself.
   ResourceMark rm;
   Arena *a = Thread::current()->resource_area();
   Node_List nstack(a);
   VectorSet visited(a);
   nstack.push(in); // Start with unique input.
   visited.set(in->_idx);
   while (nstack.size() != 0) {
     Node* n = nstack.pop();
     uint cnt = n->req();
     uint i = (n->is_Proj() && !n->is_CFG()) ? 0 : 1;
     for (; i < cnt; i++) {
       Node* m = n->in(i);
       if (m == (Node*)this) {
         return true;    // Data loop
       }
       if (m != NULL && !m->is_dead_loop_safe()) { // Only look for unsafe cases.
         if (!visited.test_set(m->_idx))
           nstack.push(m);
       }
     }
   }
   return false; // The phi is not reachable from its inputs
 }
 //------------------------------Ideal------------------------------------------
 // Return a node which is more "ideal" than the current node.  Must preserve
 // the CFG, but we can still strip out dead paths.
 Node *PhiNode::Ideal(PhaseGVN *phase, bool can_reshape) {
   // The next should never happen after 6297035 fix.
   if( is_copy() )               // Already degraded to a Copy ?
     return NULL;                // No change
   Node *r = in(0);              // RegionNode
   assert(r->in(0) == NULL || !r->in(0)->is_Root(), "not a specially hidden merge");
   // Note: During parsing, phis are often transformed before their regions.
   // This means we have to use type_or_null to defend against untyped regions.
   if( phase->type_or_null(r) == Type::TOP ) // Dead code?
     return NULL;                // No change
   Node *top = phase->C->top();
   bool new_phi = (outcnt() == 0); // transforming new Phi
   // No change for igvn if new phi is not hooked
   if (new_phi && can_reshape)
     return NULL;
   // The are 2 situations when only one valid phi's input is left
   // (in addition to Region input).
   // One: region is not loop - replace phi with this input.
   // Two: region is loop - replace phi with top since this data path is dead
   //                       and we need to break the dead data loop.
   Node* progress = NULL;        // Record if any progress made
   for( uint j = 1; j < req(); ++j ){ // For all paths in
     // Check unreachable control paths
     Node* rc = r->in(j);
     Node* n = in(j);            // Get the input
     if (rc == NULL || phase->type(rc) == Type::TOP) {
       if (n != top) {           // Not already top?
         PhaseIterGVN *igvn = phase->is_IterGVN();
         if (can_reshape && igvn != NULL) {
           igvn->_worklist.push(r);
         }
         set_req(j, top);        // Nuke it down
         progress = this;        // Record progress
       }
     }
   }
   if (can_reshape && outcnt() == 0) {
     // set_req() above may kill outputs if Phi is referenced
     // only by itself on the dead (top) control path.
     return top;
   }
   Node* uin = unique_input(phase);
   if (uin == top) {             // Simplest case: no alive inputs.
     if (can_reshape)            // IGVN transformation
       return top;
     else
       return NULL;              // Identity will return TOP
   } else if (uin != NULL) {
     // Only one not-NULL unique input path is left.
     // Determine if this input is backedge of a loop.
     // (Skip new phis which have no uses and dead regions).
     if (outcnt() > 0 && r->in(0) != NULL) {
       // First, take the short cut when we know it is a loop and
       // the EntryControl data path is dead.
       // Loop node may have only one input because entry path
       // is removed in PhaseIdealLoop::Dominators().
       assert(!r->is_Loop() || r->req() <= 3, "Loop node should have 3 or less inputs");
       bool is_loop = (r->is_Loop() && r->req() == 3);
       // Then, check if there is a data loop when phi references itself directly
       // or through other data nodes.
       if (is_loop && !uin->eqv_uncast(in(LoopNode::EntryControl)) ||
          !is_loop && is_unsafe_data_reference(uin)) {
         // Break this data loop to avoid creation of a dead loop.
         if (can_reshape) {
           return top;
         } else {
           // We can't return top if we are in Parse phase - cut inputs only
           // let Identity to handle the case.
           replace_edge(uin, top);
           return NULL;
         }
       }
     }
     // One unique input.
     debug_only(Node* ident = Identity(phase));
     // The unique input must eventually be detected by the Identity call.
 #ifdef ASSERT
     if (ident != uin && !ident->is_top()) {
       // print this output before failing assert
       r->dump(3);
       this->dump(3);
       ident->dump();
       uin->dump();
     }
 #endif
     assert(ident == uin || ident->is_top(), "Identity must clean this up");
     return NULL;
   }
   Node* opt = NULL;
   int true_path = is_diamond_phi();
   if( true_path != 0 ) {
     // Check for CMove'ing identity. If it would be unsafe,
     // handle it here. In the safe case, let Identity handle it.
     Node* unsafe_id = is_cmove_id(phase, true_path);
     if( unsafe_id != NULL && is_unsafe_data_reference(unsafe_id) )
       opt = unsafe_id;
     // Check for simple convert-to-boolean pattern
     if( opt == NULL )
       opt = is_x2logic(phase, this, true_path);
     // Check for absolute value
     if( opt == NULL )
       opt = is_absolute(phase, this, true_path);
     // Check for conditional add
     if( opt == NULL && can_reshape )
       opt = is_cond_add(phase, this, true_path);
     // These 4 optimizations could subsume the phi:
     // have to check for a dead data loop creation.
     if( opt != NULL ) {
       if( opt == unsafe_id || is_unsafe_data_reference(opt) ) {
         // Found dead loop.
         if( can_reshape )
           return top;
         // We can't return top if we are in Parse phase - cut inputs only
         // to stop further optimizations for this phi. Identity will return TOP.
         assert(req() == 3, "only diamond merge phi here");
         set_req(1, top);
         set_req(2, top);
         return NULL;
       } else {
         return opt;
       }
     }
   }
   // Check for merging identical values and split flow paths
   if (can_reshape) {
     opt = split_flow_path(phase, this);
     // This optimization only modifies phi - don't need to check for dead loop.
     assert(opt == NULL || phase->eqv(opt, this), "do not elide phi");
     if (opt != NULL)  return opt;
   }
   if (in(1) != NULL && in(1)->Opcode() == Op_AddP && can_reshape) {
     // Try to undo Phi of AddP:
     // (Phi (AddP base base y) (AddP base2 base2 y))
     // becomes:
     // newbase := (Phi base base2)
     // (AddP newbase newbase y)
     //
     // This occurs as a result of unsuccessful split_thru_phi and
     // interferes with taking advantage of addressing modes. See the
     // clone_shift_expressions code in matcher.cpp
     Node* addp = in(1);
     const Type* type = addp->in(AddPNode::Base)->bottom_type();
     Node* y = addp->in(AddPNode::Offset);
     if (y != NULL && addp->in(AddPNode::Base) == addp->in(AddPNode::Address)) {
       // make sure that all the inputs are similar to the first one,
       // i.e. AddP with base == address and same offset as first AddP
       bool doit = true;
       for (uint i = 2; i < req(); i++) {
         if (in(i) == NULL ||
             in(i)->Opcode() != Op_AddP ||
             in(i)->in(AddPNode::Base) != in(i)->in(AddPNode::Address) ||
             in(i)->in(AddPNode::Offset) != y) {
           doit = false;
           break;
         }
         // Accumulate type for resulting Phi
         type = type->meet_speculative(in(i)->in(AddPNode::Base)->bottom_type());
       }
       Node* base = NULL;
       if (doit) {
         // Check for neighboring AddP nodes in a tree.
         // If they have a base, use that it.
         for (DUIterator_Fast kmax, k = this->fast_outs(kmax); k < kmax; k++) {
           Node* u = this->fast_out(k);
           if (u->is_AddP()) {
             Node* base2 = u->in(AddPNode::Base);
             if (base2 != NULL && !base2->is_top()) {
               if (base == NULL)
                 base = base2;
               else if (base != base2)
                 { doit = false; break; }
             }
           }
         }
       }
       if (doit) {
         if (base == NULL) {
           base = new (phase->C) PhiNode(in(0), type, NULL);
           for (uint i = 1; i < req(); i++) {
             base->init_req(i, in(i)->in(AddPNode::Base));
           }
           phase->is_IterGVN()->register_new_node_with_optimizer(base);
         }
         return new (phase->C) AddPNode(base, base, y);
       }
     }
   }
   // Split phis through memory merges, so that the memory merges will go away.
   // Piggy-back this transformation on the search for a unique input....
   // It will be as if the merged memory is the unique value of the phi.
   // (Do not attempt this optimization unless parsing is complete.
   // It would make the parser's memory-merge logic sick.)
   // (MergeMemNode is not dead_loop_safe - need to check for dead loop.)
   if (progress == NULL && can_reshape && type() == Type::MEMORY) {
     // see if this phi should be sliced
     uint merge_width = 0;
     bool saw_self = false;
     for( uint i=1; i<req(); ++i ) {// For all paths in
       Node *ii = in(i);
       if (ii->is_MergeMem()) {
         MergeMemNode* n = ii->as_MergeMem();
         merge_width = MAX2(merge_width, n->req());
         saw_self = saw_self || phase->eqv(n->base_memory(), this);
       }
     }
     // This restriction is temporarily necessary to ensure termination:
     if (!saw_self && adr_type() == TypePtr::BOTTOM)  merge_width = 0;
     if (merge_width > Compile::AliasIdxRaw) {
       // found at least one non-empty MergeMem
       const TypePtr* at = adr_type();
       if (at != TypePtr::BOTTOM) {
         // Patch the existing phi to select an input from the merge:
         // Phi:AT1(...MergeMem(m0, m1, m2)...) into
         //     Phi:AT1(...m1...)
         int alias_idx = phase->C->get_alias_index(at);
         for (uint i=1; i<req(); ++i) {
           Node *ii = in(i);
           if (ii->is_MergeMem()) {
             MergeMemNode* n = ii->as_MergeMem();
             // compress paths and change unreachable cycles to TOP
             // If not, we can update the input infinitely along a MergeMem cycle
             // Equivalent code is in MemNode::Ideal_common
             Node *m  = phase->transform(n);
             if (outcnt() == 0) {  // Above transform() may kill us!
               return top;
             }
             // If transformed to a MergeMem, get the desired slice
             // Otherwise the returned node represents memory for every slice
             Node *new_mem = (m->is_MergeMem()) ?
                              m->as_MergeMem()->memory_at(alias_idx) : m;
             // Update input if it is progress over what we have now
             if (new_mem != ii) {
               set_req(i, new_mem);
               progress = this;
             }
           }
         }
       } else {
         // We know that at least one MergeMem->base_memory() == this
         // (saw_self == true). If all other inputs also references this phi
         // (directly or through data nodes) - it is dead loop.
         bool saw_safe_input = false;
         for (uint j = 1; j < req(); ++j) {
           Node *n = in(j);
           if (n->is_MergeMem() && n->as_MergeMem()->base_memory() == this)
             continue;              // skip known cases
           if (!is_unsafe_data_reference(n)) {
             saw_safe_input = true; // found safe input
             break;
           }
         }
         if (!saw_safe_input)
           return top; // all inputs reference back to this phi - dead loop
         // Phi(...MergeMem(m0, m1:AT1, m2:AT2)...) into
         //     MergeMem(Phi(...m0...), Phi:AT1(...m1...), Phi:AT2(...m2...))
         PhaseIterGVN *igvn = phase->is_IterGVN();
         Node* hook = new (phase->C) Node(1);
         PhiNode* new_base = (PhiNode*) clone();
         // Must eagerly register phis, since they participate in loops.
         if (igvn) {
           igvn->register_new_node_with_optimizer(new_base);
           hook->add_req(new_base);
         }
         MergeMemNode* result = MergeMemNode::make(phase->C, new_base);
         for (uint i = 1; i < req(); ++i) {
           Node *ii = in(i);
           if (ii->is_MergeMem()) {
             MergeMemNode* n = ii->as_MergeMem();
             for (MergeMemStream mms(result, n); mms.next_non_empty2(); ) {
               // If we have not seen this slice yet, make a phi for it.
               bool made_new_phi = false;
               if (mms.is_empty()) {
                 Node* new_phi = new_base->slice_memory(mms.adr_type(phase->C));
                 made_new_phi = true;
                 if (igvn) {
                   igvn->register_new_node_with_optimizer(new_phi);
                   hook->add_req(new_phi);
                 }
                 mms.set_memory(new_phi);
               }
               Node* phi = mms.memory();
               assert(made_new_phi || phi->in(i) == n, "replace the i-th merge by a slice");
               phi->set_req(i, mms.memory2());
             }
           }
         }
         // Distribute all self-loops.
         { // (Extra braces to hide mms.)
           for (MergeMemStream mms(result); mms.next_non_empty(); ) {
             Node* phi = mms.memory();
             for (uint i = 1; i < req(); ++i) {
               if (phi->in(i) == this)  phi->set_req(i, phi);
             }
           }
         }
         // now transform the new nodes, and return the mergemem
         for (MergeMemStream mms(result); mms.next_non_empty(); ) {
           Node* phi = mms.memory();
           mms.set_memory(phase->transform(phi));
         }
         if (igvn) { // Unhook.
           igvn->hash_delete(hook);
           for (uint i = 1; i < hook->req(); i++) {
             hook->set_req(i, NULL);
           }
         }
         // Replace self with the result.
         return result;
       }
     }
     //
     // Other optimizations on the memory chain
     //
     const TypePtr* at = adr_type();
     for( uint i=1; i<req(); ++i ) {// For all paths in
       Node *ii = in(i);
       Node *new_in = MemNode::optimize_memory_chain(ii, at, NULL, phase);
       if (ii != new_in ) {
         set_req(i, new_in);
         progress = this;
       }
     }
   }
 #ifdef _LP64
   // Push DecodeN/DecodeNKlass down through phi.
   // The rest of phi graph will transform by split EncodeP node though phis up.
   if ((UseCompressedOops || UseCompressedClassPointers) && can_reshape && progress == NULL) {
     bool may_push = true;
     bool has_decodeN = false;
     bool is_decodeN = false;
     for (uint i=1; i<req(); ++i) {// For all paths in
       Node *ii = in(i);
       if (ii->is_DecodeNarrowPtr() && ii->bottom_type() == bottom_type()) {
         // Do optimization if a non dead path exist.
         if (ii->in(1)->bottom_type() != Type::TOP) {
           has_decodeN = true;
           is_decodeN = ii->is_DecodeN();
         }
       } else if (!ii->is_Phi()) {
         may_push = false;
       }
     }
     if (has_decodeN && may_push) {
       PhaseIterGVN *igvn = phase->is_IterGVN();
       // Make narrow type for new phi.
       const Type* narrow_t;
       if (is_decodeN) {
         narrow_t = TypeNarrowOop::make(this->bottom_type()->is_ptr());
       } else {
         narrow_t = TypeNarrowKlass::make(this->bottom_type()->is_ptr());
       }
       PhiNode* new_phi = new (phase->C) PhiNode(r, narrow_t);
       uint orig_cnt = req();
       for (uint i=1; i<req(); ++i) {// For all paths in
         Node *ii = in(i);
         Node* new_ii = NULL;
         if (ii->is_DecodeNarrowPtr()) {
           assert(ii->bottom_type() == bottom_type(), "sanity");
           new_ii = ii->in(1);
         } else {
           assert(ii->is_Phi(), "sanity");
           if (ii->as_Phi() == this) {
             new_ii = new_phi;
           } else {
             if (is_decodeN) {
               new_ii = new (phase->C) EncodePNode(ii, narrow_t);
             } else {
               new_ii = new (phase->C) EncodePKlassNode(ii, narrow_t);
             }
             igvn->register_new_node_with_optimizer(new_ii);
           }
         }
         new_phi->set_req(i, new_ii);
       }
       igvn->register_new_node_with_optimizer(new_phi, this);
       if (is_decodeN) {
         progress = new (phase->C) DecodeNNode(new_phi, bottom_type());
       } else {
         progress = new (phase->C) DecodeNKlassNode(new_phi, bottom_type());
       }
     }
   }
 #endif
   return progress;              // Return any progress
 }
 //------------------------------is_tripcount-----------------------------------
 bool PhiNode::is_tripcount() const {
   return (in(0) != NULL && in(0)->is_CountedLoop() &&
           in(0)->as_CountedLoop()->phi() == this);
 }
 //------------------------------out_RegMask------------------------------------
 const RegMask &PhiNode::in_RegMask(uint i) const {
   return i ? out_RegMask() : RegMask::Empty;
 }
 const RegMask &PhiNode::out_RegMask() const {
   uint ideal_reg = _type->ideal_reg();
   assert( ideal_reg != Node::NotAMachineReg, "invalid type at Phi" );
   if( ideal_reg == 0 ) return RegMask::Empty;
   return *(Compile::current()->matcher()->idealreg2spillmask[ideal_reg]);
 }
 #ifndef PRODUCT
 void PhiNode::dump_spec(outputStream *st) const {
   TypeNode::dump_spec(st);
   if (is_tripcount()) {
     st->print(" #tripcount");
   }
 }
 #endif
 //=============================================================================
 const Type *GotoNode::Value( PhaseTransform *phase ) const {
   // If the input is reachable, then we are executed.
   // If the input is not reachable, then we are not executed.
   return phase->type(in(0));
 }
 Node *GotoNode::Identity( PhaseTransform *phase ) {
   return in(0);                // Simple copy of incoming control
 }
 const RegMask &GotoNode::out_RegMask() const {
   return RegMask::Empty;
 }
 //=============================================================================
 const RegMask &JumpNode::out_RegMask() const {
   return RegMask::Empty;
 }
 //=============================================================================
 const RegMask &JProjNode::out_RegMask() const {
   return RegMask::Empty;
 }
 //=============================================================================
 const RegMask &CProjNode::out_RegMask() const {
   return RegMask::Empty;
 }
 //=============================================================================
 uint PCTableNode::hash() const { return Node::hash() + _size; }
 uint PCTableNode::cmp( const Node &n ) const
 { return _size == ((PCTableNode&)n)._size; }
 const Type *PCTableNode::bottom_type() const {
   const Type** f = TypeTuple::fields(_size);
   for( uint i = 0; i < _size; i++ ) f[i] = Type::CONTROL;
   return TypeTuple::make(_size, f);
 }
 //------------------------------Value------------------------------------------
 // Compute the type of the PCTableNode.  If reachable it is a tuple of
 // Control, otherwise the table targets are not reachable
 const Type *PCTableNode::Value( PhaseTransform *phase ) const {
   if( phase->type(in(0)) == Type::CONTROL )
     return bottom_type();
   return Type::TOP;             // All paths dead?  Then so are we
 }
 //------------------------------Ideal------------------------------------------
 // Return a node which is more "ideal" than the current node.  Strip out
 // control copies
 Node *PCTableNode::Ideal(PhaseGVN *phase, bool can_reshape) {
   return remove_dead_region(phase, can_reshape) ? this : NULL;
 }
 //=============================================================================
 uint JumpProjNode::hash() const {
   return Node::hash() + _dest_bci;
 }
 uint JumpProjNode::cmp( const Node &n ) const {
   return ProjNode::cmp(n) &&
     _dest_bci == ((JumpProjNode&)n)._dest_bci;
 }
 #ifndef PRODUCT
 void JumpProjNode::dump_spec(outputStream *st) const {
   ProjNode::dump_spec(st);
    st->print("@bci %d ",_dest_bci);
 }
 #endif
 //=============================================================================
 //------------------------------Value------------------------------------------
 // Check for being unreachable, or for coming from a Rethrow.  Rethrow's cannot
 // have the default "fall_through_index" path.
 const Type *CatchNode::Value( PhaseTransform *phase ) const {
   // Unreachable?  Then so are all paths from here.
   if( phase->type(in(0)) == Type::TOP ) return Type::TOP;
   // First assume all paths are reachable
   const Type** f = TypeTuple::fields(_size);
   for( uint i = 0; i < _size; i++ ) f[i] = Type::CONTROL;
   // Identify cases that will always throw an exception
   // () rethrow call
   // () virtual or interface call with NULL receiver
   // () call is a check cast with incompatible arguments
   if( in(1)->is_Proj() ) {
     Node *i10 = in(1)->in(0);
     if( i10->is_Call() ) {
       CallNode *call = i10->as_Call();
       // Rethrows always throw exceptions, never return
       if (call->entry_point() == OptoRuntime::rethrow_stub()) {
         f[CatchProjNode::fall_through_index] = Type::TOP;
       } else if( call->req() > TypeFunc::Parms ) {
         const Type *arg0 = phase->type( call->in(TypeFunc::Parms) );
         // Check for null receiver to virtual or interface calls
         if( call->is_CallDynamicJava() &&
             arg0->higher_equal(TypePtr::NULL_PTR) ) {
           f[CatchProjNode::fall_through_index] = Type::TOP;
         }
       } // End of if not a runtime stub
     } // End of if have call above me
   } // End of slot 1 is not a projection
   return TypeTuple::make(_size, f);
 }
 //=============================================================================
 uint CatchProjNode::hash() const {
   return Node::hash() + _handler_bci;
 }
 uint CatchProjNode::cmp( const Node &n ) const {
   return ProjNode::cmp(n) &&
     _handler_bci == ((CatchProjNode&)n)._handler_bci;
 }
 //------------------------------Identity---------------------------------------
 // If only 1 target is possible, choose it if it is the main control
 Node *CatchProjNode::Identity( PhaseTransform *phase ) {
   // If my value is control and no other value is, then treat as ID
   const TypeTuple *t = phase->type(in(0))->is_tuple();
   if (t->field_at(_con) != Type::CONTROL)  return this;
   // If we remove the last CatchProj and elide the Catch/CatchProj, then we
   // also remove any exception table entry.  Thus we must know the call
   // feeding the Catch will not really throw an exception.  This is ok for
   // the main fall-thru control (happens when we know a call can never throw
   // an exception) or for "rethrow", because a further optimization will
   // yank the rethrow (happens when we inline a function that can throw an
   // exception and the caller has no handler).  Not legal, e.g., for passing
   // a NULL receiver to a v-call, or passing bad types to a slow-check-cast.
   // These cases MUST throw an exception via the runtime system, so the VM
   // will be looking for a table entry.
   Node *proj = in(0)->in(1);    // Expect a proj feeding CatchNode
   CallNode *call;
   if (_con != TypeFunc::Control && // Bail out if not the main control.
       !(proj->is_Proj() &&      // AND NOT a rethrow
         proj->in(0)->is_Call() &&
         (call = proj->in(0)->as_Call()) &&
         call->entry_point() == OptoRuntime::rethrow_stub()))
     return this;
   // Search for any other path being control
   for (uint i = 0; i < t->cnt(); i++) {
     if (i != _con && t->field_at(i) == Type::CONTROL)
       return this;
   }
   // Only my path is possible; I am identity on control to the jump
   return in(0)->in(0);
 }
 #ifndef PRODUCT
 void CatchProjNode::dump_spec(outputStream *st) const {
   ProjNode::dump_spec(st);
   st->print("@bci %d ",_handler_bci);
 }
 #endif
 //=============================================================================
 //------------------------------Identity---------------------------------------
 // Check for CreateEx being Identity.
 Node *CreateExNode::Identity( PhaseTransform *phase ) {
   if( phase->type(in(1)) == Type::TOP ) return in(1);
   if( phase->type(in(0)) == Type::TOP ) return in(0);
   // We only come from CatchProj, unless the CatchProj goes away.
   // If the CatchProj is optimized away, then we just carry the
   // exception oop through.
   CallNode *call = in(1)->in(0)->as_Call();
   return ( in(0)->is_CatchProj() && in(0)->in(0)->in(1) == in(1) )
     ? this
     : call->in(TypeFunc::Parms);
 }
 //=============================================================================
 //------------------------------Value------------------------------------------
 // Check for being unreachable.
 const Type *NeverBranchNode::Value( PhaseTransform *phase ) const {
   if (!in(0) || in(0)->is_top()) return Type::TOP;
   return bottom_type();
 }
 //------------------------------Ideal------------------------------------------
 // Check for no longer being part of a loop
 Node *NeverBranchNode::Ideal(PhaseGVN *phase, bool can_reshape) {
   if (can_reshape && !in(0)->is_Loop()) {
     // Dead code elimination can sometimes delete this projection so
     // if it's not there, there's nothing to do.
     Node* fallthru = proj_out(0);
     if (fallthru != NULL) {
       phase->is_IterGVN()->replace_node(fallthru, in(0));
     }
     return phase->C->top();
   }
   return NULL;
 }
 #ifndef PRODUCT
 void NeverBranchNode::format( PhaseRegAlloc *ra_, outputStream *st) const {
   st->print("%s", Name());
 }
 #endif

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/opto/cfgnode.cpp@f90c822e73f8 (annotated)

src/share/vm/opto/cfgnode.cpp