Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * Copyright (c) 2007, 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

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 #include "precompiled.hpp"

 #include "compiler/compileLog.hpp"

 #include "libadt/vectset.hpp"

 #include "memory/allocation.inline.hpp"

 #include "opto/addnode.hpp"

 #include "opto/callnode.hpp"

 #include "opto/divnode.hpp"

 #include "opto/matcher.hpp"

 #include "opto/memnode.hpp"

 #include "opto/mulnode.hpp"

 #include "opto/opcodes.hpp"

 #include "opto/superword.hpp"

 #include "opto/vectornode.hpp"

 //

 //                  S U P E R W O R D   T R A N S F O R M

 //=============================================================================

 //------------------------------SuperWord---------------------------

 SuperWord::SuperWord(PhaseIdealLoop* phase) :

   _phase(phase),

   _igvn(phase->_igvn),

   _arena(phase->C->comp_arena()),

   _packset(arena(), 8,  0, NULL),         // packs for the current block

   _bb_idx(arena(), (int)(1.10 * phase->C->unique()), 0, 0), // node idx to index in bb

   _block(arena(), 8,  0, NULL),           // nodes in current block

   _data_entry(arena(), 8,  0, NULL),      // nodes with all inputs from outside

   _mem_slice_head(arena(), 8,  0, NULL),  // memory slice heads

   _mem_slice_tail(arena(), 8,  0, NULL),  // memory slice tails

   _node_info(arena(), 8,  0, SWNodeInfo::initial), // info needed per node

   _align_to_ref(NULL),                    // memory reference to align vectors to

   _disjoint_ptrs(arena(), 8,  0, OrderedPair::initial), // runtime disambiguated pointer pairs

   _dg(_arena),                            // dependence graph

   _visited(arena()),                      // visited node set

   _post_visited(arena()),                 // post visited node set

   _n_idx_list(arena(), 8),                // scratch list of (node,index) pairs

   _stk(arena(), 8, 0, NULL),              // scratch stack of nodes

   _nlist(arena(), 8, 0, NULL),            // scratch list of nodes

   _lpt(NULL),                             // loop tree node

   _lp(NULL),                              // LoopNode

   _bb(NULL),                              // basic block

   _iv(NULL)                               // induction var

 {}

 //------------------------------transform_loop---------------------------

 void SuperWord::transform_loop(IdealLoopTree* lpt) {

   assert(lpt->_head->is_CountedLoop(), "must be");

   CountedLoopNode *cl = lpt->_head->as_CountedLoop();

   if (!cl->is_valid_counted_loop()) return; // skip malformed counted loop

   if (!cl->is_main_loop() ) return; // skip normal, pre, and post loops

   // Check for no control flow in body (other than exit)

   Node *cl_exit = cl->loopexit();

   if (cl_exit->in(0) != lpt->_head) return;

   // Make sure the are no extra control users of the loop backedge

   if (cl->back_control()->outcnt() != 1) {

     return;

   }

   // Check for pre-loop ending with CountedLoopEnd(Bool(Cmp(x,Opaque1(limit))))

   CountedLoopEndNode* pre_end = get_pre_loop_end(cl);

   if (pre_end == NULL) return;

   Node *pre_opaq1 = pre_end->limit();

   if (pre_opaq1->Opcode() != Op_Opaque1) return;

   // Do vectors exist on this architecture?

   if (vector_width_in_bytes() == 0) return;

   init(); // initialize data structures

   set_lpt(lpt);

   set_lp(cl);

  // For now, define one block which is the entire loop body

   set_bb(cl);

   assert(_packset.length() == 0, "packset must be empty");

   SLP_extract();

 }

 //------------------------------SLP_extract---------------------------

 // Extract the superword level parallelism

 //

 // 1) A reverse post-order of nodes in the block is constructed.  By scanning

 //    this list from first to last, all definitions are visited before their uses.

 //

 // 2) A point-to-point dependence graph is constructed between memory references.

 //    This simplies the upcoming "independence" checker.

 //

 // 3) The maximum depth in the node graph from the beginning of the block

 //    to each node is computed.  This is used to prune the graph search

 //    in the independence checker.

 //

 // 4) For integer types, the necessary bit width is propagated backwards

 //    from stores to allow packed operations on byte, char, and short

 //    integers.  This reverses the promotion to type "int" that javac

 //    did for operations like: char c1,c2,c3;  c1 = c2 + c3.

 //

 // 5) One of the memory references is picked to be an aligned vector reference.

 //    The pre-loop trip count is adjusted to align this reference in the

 //    unrolled body.

 //

 // 6) The initial set of pack pairs is seeded with memory references.

 //

 // 7) The set of pack pairs is extended by following use->def and def->use links.

 //

 // 8) The pairs are combined into vector sized packs.

 //

 // 9) Reorder the memory slices to co-locate members of the memory packs.

 //

 // 10) Generate ideal vector nodes for the final set of packs and where necessary,

 //    inserting scalar promotion, vector creation from multiple scalars, and

 //    extraction of scalar values from vectors.

 //

 void SuperWord::SLP_extract() {

   // Ready the block

   construct_bb();

   dependence_graph();

   compute_max_depth();

   compute_vector_element_type();

   // Attempt vectorization

   find_adjacent_refs();

   extend_packlist();

   combine_packs();

   construct_my_pack_map();

   filter_packs();

   schedule();

   output();

 }

 //------------------------------find_adjacent_refs---------------------------

 // Find the adjacent memory references and create pack pairs for them.

 // This is the initial set of packs that will then be extended by

 // following use->def and def->use links.  The align positions are

 // assigned relative to the reference "align_to_ref"

 void SuperWord::find_adjacent_refs() {

   // Get list of memory operations

   Node_List memops;

   for (int i = 0; i < _block.length(); i++) {

     Node* n = _block.at(i);

     if (n->is_Mem() && in_bb(n) &&

         is_java_primitive(n->as_Mem()->memory_type())) {

       int align = memory_alignment(n->as_Mem(), 0);

       if (align != bottom_align) {

         memops.push(n);

       }

     }

   }

   if (memops.size() == 0) return;

   // Find a memory reference to align to.  The pre-loop trip count

   // is modified to align this reference to a vector-aligned address

   find_align_to_ref(memops);

   if (align_to_ref() == NULL) return;

   SWPointer align_to_ref_p(align_to_ref(), this);

   int offset = align_to_ref_p.offset_in_bytes();

   int scale  = align_to_ref_p.scale_in_bytes();

   int vw              = vector_width_in_bytes();

   int stride_sign     = (scale * iv_stride()) > 0 ? 1 : -1;

   int iv_adjustment   = (stride_sign * vw - (offset % vw)) % vw;

 #ifndef PRODUCT

   if (TraceSuperWord)

     tty->print_cr("\noffset = %d iv_adjustment = %d  elt_align = %d scale = %d iv_stride = %d",

                   offset, iv_adjustment, align_to_ref_p.memory_size(), align_to_ref_p.scale_in_bytes(), iv_stride());

 #endif

   // Set alignment relative to "align_to_ref"

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

     MemNode* s = memops.at(i)->as_Mem();

     SWPointer p2(s, this);

     if (p2.comparable(align_to_ref_p)) {

       int align = memory_alignment(s, iv_adjustment);

       set_alignment(s, align);

     } else {

       memops.remove(i);

     }

   }

   // Create initial pack pairs of memory operations

   for (uint i = 0; i < memops.size(); i++) {

     Node* s1 = memops.at(i);

     for (uint j = 0; j < memops.size(); j++) {

       Node* s2 = memops.at(j);

       if (s1 != s2 && are_adjacent_refs(s1, s2)) {

         int align = alignment(s1);

         if (stmts_can_pack(s1, s2, align)) {

           Node_List* pair = new Node_List();

           pair->push(s1);

           pair->push(s2);

           _packset.append(pair);

         }

       }

     }

   }

 #ifndef PRODUCT

   if (TraceSuperWord) {

     tty->print_cr("\nAfter find_adjacent_refs");

     print_packset();

   }

 #endif

 }

 //------------------------------find_align_to_ref---------------------------

 // Find a memory reference to align the loop induction variable to.

 // Looks first at stores then at loads, looking for a memory reference

 // with the largest number of references similar to it.

 void SuperWord::find_align_to_ref(Node_List &memops) {

   GrowableArray<int> cmp_ct(arena(), memops.size(), memops.size(), 0);

   // Count number of comparable memory ops

   for (uint i = 0; i < memops.size(); i++) {

     MemNode* s1 = memops.at(i)->as_Mem();

     SWPointer p1(s1, this);

     // Discard if pre loop can't align this reference

     if (!ref_is_alignable(p1)) {

       *cmp_ct.adr_at(i) = 0;

       continue;

     }

     for (uint j = i+1; j < memops.size(); j++) {

       MemNode* s2 = memops.at(j)->as_Mem();

       if (isomorphic(s1, s2)) {

         SWPointer p2(s2, this);

         if (p1.comparable(p2)) {

           (*cmp_ct.adr_at(i))++;

           (*cmp_ct.adr_at(j))++;

         }

       }

     }

   }

   // Find Store (or Load) with the greatest number of "comparable" references

   int max_ct        = 0;

   int max_idx       = -1;

   int min_size      = max_jint;

   int min_iv_offset = max_jint;

   for (uint j = 0; j < memops.size(); j++) {

     MemNode* s = memops.at(j)->as_Mem();

     if (s->is_Store()) {

       SWPointer p(s, this);

       if (cmp_ct.at(j) > max_ct ||

           cmp_ct.at(j) == max_ct && (data_size(s) < min_size ||

                                      data_size(s) == min_size &&

                                         p.offset_in_bytes() < min_iv_offset)) {

         max_ct = cmp_ct.at(j);

         max_idx = j;

         min_size = data_size(s);

         min_iv_offset = p.offset_in_bytes();

       }

     }

   }

   // If no stores, look at loads

   if (max_ct == 0) {

     for (uint j = 0; j < memops.size(); j++) {

       MemNode* s = memops.at(j)->as_Mem();

       if (s->is_Load()) {

         SWPointer p(s, this);

         if (cmp_ct.at(j) > max_ct ||

             cmp_ct.at(j) == max_ct && (data_size(s) < min_size ||

                                        data_size(s) == min_size &&

                                           p.offset_in_bytes() < min_iv_offset)) {

           max_ct = cmp_ct.at(j);

           max_idx = j;

           min_size = data_size(s);

           min_iv_offset = p.offset_in_bytes();

         }

       }

     }

   }

   if (max_ct > 0)

     set_align_to_ref(memops.at(max_idx)->as_Mem());

 #ifndef PRODUCT

   if (TraceSuperWord && Verbose) {

     tty->print_cr("\nVector memops after find_align_to_refs");

     for (uint i = 0; i < memops.size(); i++) {

       MemNode* s = memops.at(i)->as_Mem();

       s->dump();

     }

   }

 #endif

 }

 //------------------------------ref_is_alignable---------------------------

 // Can the preloop align the reference to position zero in the vector?

 bool SuperWord::ref_is_alignable(SWPointer& p) {

   if (!p.has_iv()) {

     return true;   // no induction variable

   }

   CountedLoopEndNode* pre_end = get_pre_loop_end(lp()->as_CountedLoop());

   assert(pre_end->stride_is_con(), "pre loop stride is constant");

   int preloop_stride = pre_end->stride_con();

   int span = preloop_stride * p.scale_in_bytes();

   // Stride one accesses are alignable.

   if (ABS(span) == p.memory_size())

     return true;

   // If initial offset from start of object is computable,

   // compute alignment within the vector.

   int vw = vector_width_in_bytes();

   if (vw % span == 0) {

     Node* init_nd = pre_end->init_trip();

     if (init_nd->is_Con() && p.invar() == NULL) {

       int init = init_nd->bottom_type()->is_int()->get_con();

       int init_offset = init * p.scale_in_bytes() + p.offset_in_bytes();

       assert(init_offset >= 0, "positive offset from object start");

       if (span > 0) {

         return (vw - (init_offset % vw)) % span == 0;

       } else {

         assert(span < 0, "nonzero stride * scale");

         return (init_offset % vw) % -span == 0;

       }

     }

   }

   return false;

 }

 //---------------------------dependence_graph---------------------------

 // Construct dependency graph.

 // Add dependence edges to load/store nodes for memory dependence

 //    A.out()->DependNode.in(1) and DependNode.out()->B.prec(x)

 void SuperWord::dependence_graph() {

   // First, assign a dependence node to each memory node

   for (int i = 0; i < _block.length(); i++ ) {

     Node *n = _block.at(i);

     if (n->is_Mem() || n->is_Phi() && n->bottom_type() == Type::MEMORY) {

       _dg.make_node(n);

     }

   }

   // For each memory slice, create the dependences

   for (int i = 0; i < _mem_slice_head.length(); i++) {

     Node* n      = _mem_slice_head.at(i);

     Node* n_tail = _mem_slice_tail.at(i);

     // Get slice in predecessor order (last is first)

     mem_slice_preds(n_tail, n, _nlist);

     // Make the slice dependent on the root

     DepMem* slice = _dg.dep(n);

     _dg.make_edge(_dg.root(), slice);

     // Create a sink for the slice

     DepMem* slice_sink = _dg.make_node(NULL);

     _dg.make_edge(slice_sink, _dg.tail());

     // Now visit each pair of memory ops, creating the edges

     for (int j = _nlist.length() - 1; j >= 0 ; j--) {

       Node* s1 = _nlist.at(j);

       // If no dependency yet, use slice

       if (_dg.dep(s1)->in_cnt() == 0) {

         _dg.make_edge(slice, s1);

       }

       SWPointer p1(s1->as_Mem(), this);

       bool sink_dependent = true;

       for (int k = j - 1; k >= 0; k--) {

         Node* s2 = _nlist.at(k);

         if (s1->is_Load() && s2->is_Load())

           continue;

         SWPointer p2(s2->as_Mem(), this);

         int cmp = p1.cmp(p2);

         if (SuperWordRTDepCheck &&

             p1.base() != p2.base() && p1.valid() && p2.valid()) {

           // Create a runtime check to disambiguate

           OrderedPair pp(p1.base(), p2.base());

           _disjoint_ptrs.append_if_missing(pp);

         } else if (!SWPointer::not_equal(cmp)) {

           // Possibly same address

           _dg.make_edge(s1, s2);

           sink_dependent = false;

         }

       }

       if (sink_dependent) {

         _dg.make_edge(s1, slice_sink);

       }

     }

 #ifndef PRODUCT

     if (TraceSuperWord) {

       tty->print_cr("\nDependence graph for slice: %d", n->_idx);

       for (int q = 0; q < _nlist.length(); q++) {

         _dg.print(_nlist.at(q));

       }

       tty->cr();

     }

 #endif

     _nlist.clear();

   }

 #ifndef PRODUCT

   if (TraceSuperWord) {

     tty->print_cr("\ndisjoint_ptrs: %s", _disjoint_ptrs.length() > 0 ? "" : "NONE");

     for (int r = 0; r < _disjoint_ptrs.length(); r++) {

       _disjoint_ptrs.at(r).print();

       tty->cr();

     }

     tty->cr();

   }

 #endif

 }

 //---------------------------mem_slice_preds---------------------------

 // Return a memory slice (node list) in predecessor order starting at "start"

 void SuperWord::mem_slice_preds(Node* start, Node* stop, GrowableArray<Node*> &preds) {

   assert(preds.length() == 0, "start empty");

   Node* n = start;

   Node* prev = NULL;

   while (true) {

     assert(in_bb(n), "must be in block");

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

       Node* out = n->fast_out(i);

       if (out->is_Load()) {

         if (in_bb(out)) {

           preds.push(out);

         }

       } else {

         // FIXME

         if (out->is_MergeMem() && !in_bb(out)) {

           // Either unrolling is causing a memory edge not to disappear,

           // or need to run igvn.optimize() again before SLP

         } else if (out->is_Phi() && out->bottom_type() == Type::MEMORY && !in_bb(out)) {

           // Ditto.  Not sure what else to check further.

         } else if (out->Opcode() == Op_StoreCM && out->in(MemNode::OopStore) == n) {

           // StoreCM has an input edge used as a precedence edge.

           // Maybe an issue when oop stores are vectorized.

         } else {

           assert(out == prev || prev == NULL, "no branches off of store slice");

         }

       }

     }

     if (n == stop) break;

     preds.push(n);

     prev = n;

     n = n->in(MemNode::Memory);

   }

 }

 //------------------------------stmts_can_pack---------------------------

 // Can s1 and s2 be in a pack with s1 immediately preceding s2 and

 // s1 aligned at "align"

 bool SuperWord::stmts_can_pack(Node* s1, Node* s2, int align) {

   // Do not use superword for non-primitives

   if((s1->is_Mem() && !is_java_primitive(s1->as_Mem()->memory_type())) ||

      (s2->is_Mem() && !is_java_primitive(s2->as_Mem()->memory_type())))

     return false;

   if (isomorphic(s1, s2)) {

     if (independent(s1, s2)) {

       if (!exists_at(s1, 0) && !exists_at(s2, 1)) {

         if (!s1->is_Mem() || are_adjacent_refs(s1, s2)) {

           int s1_align = alignment(s1);

           int s2_align = alignment(s2);

           if (s1_align == top_align || s1_align == align) {

             if (s2_align == top_align || s2_align == align + data_size(s1)) {

               return true;

             }

           }

         }

       }

     }

   }

   return false;

 }

 //------------------------------exists_at---------------------------

 // Does s exist in a pack at position pos?

 bool SuperWord::exists_at(Node* s, uint pos) {

   for (int i = 0; i < _packset.length(); i++) {

     Node_List* p = _packset.at(i);

     if (p->at(pos) == s) {

       return true;

     }

   }

   return false;

 }

 //------------------------------are_adjacent_refs---------------------------

 // Is s1 immediately before s2 in memory?

 bool SuperWord::are_adjacent_refs(Node* s1, Node* s2) {

   if (!s1->is_Mem() || !s2->is_Mem()) return false;

   if (!in_bb(s1)    || !in_bb(s2))    return false;

   // Do not use superword for non-primitives

   if (!is_java_primitive(s1->as_Mem()->memory_type()) ||

       !is_java_primitive(s2->as_Mem()->memory_type())) {

     return false;

   }

   // FIXME - co_locate_pack fails on Stores in different mem-slices, so

   // only pack memops that are in the same alias set until that's fixed.

   if (_phase->C->get_alias_index(s1->as_Mem()->adr_type()) !=

       _phase->C->get_alias_index(s2->as_Mem()->adr_type()))

     return false;

   SWPointer p1(s1->as_Mem(), this);

   SWPointer p2(s2->as_Mem(), this);

   if (p1.base() != p2.base() || !p1.comparable(p2)) return false;

   int diff = p2.offset_in_bytes() - p1.offset_in_bytes();

   return diff == data_size(s1);

 }

 //------------------------------isomorphic---------------------------

 // Are s1 and s2 similar?

 bool SuperWord::isomorphic(Node* s1, Node* s2) {

   if (s1->Opcode() != s2->Opcode()) return false;

   if (s1->req() != s2->req()) return false;

   if (s1->in(0) != s2->in(0)) return false;

   if (velt_type(s1) != velt_type(s2)) return false;

   return true;

 }

 //------------------------------independent---------------------------

 // Is there no data path from s1 to s2 or s2 to s1?

 bool SuperWord::independent(Node* s1, Node* s2) {

   //  assert(s1->Opcode() == s2->Opcode(), "check isomorphic first");

   int d1 = depth(s1);

   int d2 = depth(s2);

   if (d1 == d2) return s1 != s2;

   Node* deep    = d1 > d2 ? s1 : s2;

   Node* shallow = d1 > d2 ? s2 : s1;

   visited_clear();

   return independent_path(shallow, deep);

 }

 //------------------------------independent_path------------------------------

 // Helper for independent

 bool SuperWord::independent_path(Node* shallow, Node* deep, uint dp) {

   if (dp >= 1000) return false; // stop deep recursion

   visited_set(deep);

   int shal_depth = depth(shallow);

   assert(shal_depth <= depth(deep), "must be");

   for (DepPreds preds(deep, _dg); !preds.done(); preds.next()) {

     Node* pred = preds.current();

     if (in_bb(pred) && !visited_test(pred)) {

       if (shallow == pred) {

         return false;

       }

       if (shal_depth < depth(pred) && !independent_path(shallow, pred, dp+1)) {

         return false;

       }

     }

   }

   return true;

 }

 //------------------------------set_alignment---------------------------

 void SuperWord::set_alignment(Node* s1, Node* s2, int align) {

   set_alignment(s1, align);

   set_alignment(s2, align + data_size(s1));

 }

 //------------------------------data_size---------------------------

 int SuperWord::data_size(Node* s) {

   const Type* t = velt_type(s);

   BasicType  bt = t->array_element_basic_type();

   int bsize = type2aelembytes(bt);

   assert(bsize != 0, "valid size");

   return bsize;

 }

 //------------------------------extend_packlist---------------------------

 // Extend packset by following use->def and def->use links from pack members.

 void SuperWord::extend_packlist() {

   bool changed;

   do {

     changed = false;

     for (int i = 0; i < _packset.length(); i++) {

       Node_List* p = _packset.at(i);

       changed |= follow_use_defs(p);

       changed |= follow_def_uses(p);

     }

   } while (changed);

 #ifndef PRODUCT

   if (TraceSuperWord) {

     tty->print_cr("\nAfter extend_packlist");

     print_packset();

   }

 #endif

 }

 //------------------------------follow_use_defs---------------------------

 // Extend the packset by visiting operand definitions of nodes in pack p

 bool SuperWord::follow_use_defs(Node_List* p) {

   Node* s1 = p->at(0);

   Node* s2 = p->at(1);

   assert(p->size() == 2, "just checking");

   assert(s1->req() == s2->req(), "just checking");

   assert(alignment(s1) + data_size(s1) == alignment(s2), "just checking");

   if (s1->is_Load()) return false;

   int align = alignment(s1);

   bool changed = false;

   int start = s1->is_Store() ? MemNode::ValueIn   : 1;

   int end   = s1->is_Store() ? MemNode::ValueIn+1 : s1->req();

   for (int j = start; j < end; j++) {

     Node* t1 = s1->in(j);

     Node* t2 = s2->in(j);

     if (!in_bb(t1) || !in_bb(t2))

       continue;

     if (stmts_can_pack(t1, t2, align)) {

       if (est_savings(t1, t2) >= 0) {

         Node_List* pair = new Node_List();

         pair->push(t1);

         pair->push(t2);

         _packset.append(pair);

         set_alignment(t1, t2, align);

         changed = true;

       }

     }

   }

   return changed;

 }

 //------------------------------follow_def_uses---------------------------

 // Extend the packset by visiting uses of nodes in pack p

 bool SuperWord::follow_def_uses(Node_List* p) {

   bool changed = false;

   Node* s1 = p->at(0);

   Node* s2 = p->at(1);

   assert(p->size() == 2, "just checking");

   assert(s1->req() == s2->req(), "just checking");

   assert(alignment(s1) + data_size(s1) == alignment(s2), "just checking");

   if (s1->is_Store()) return false;

   int align = alignment(s1);

   int savings = -1;

   Node* u1 = NULL;

   Node* u2 = NULL;

   for (DUIterator_Fast imax, i = s1->fast_outs(imax); i < imax; i++) {

     Node* t1 = s1->fast_out(i);

     if (!in_bb(t1)) continue;

     for (DUIterator_Fast jmax, j = s2->fast_outs(jmax); j < jmax; j++) {

       Node* t2 = s2->fast_out(j);

       if (!in_bb(t2)) continue;

       if (!opnd_positions_match(s1, t1, s2, t2))

         continue;

       if (stmts_can_pack(t1, t2, align)) {

         int my_savings = est_savings(t1, t2);

         if (my_savings > savings) {

           savings = my_savings;

           u1 = t1;

           u2 = t2;

         }

       }

     }

   }

   if (savings >= 0) {

     Node_List* pair = new Node_List();

     pair->push(u1);

     pair->push(u2);

     _packset.append(pair);

     set_alignment(u1, u2, align);

     changed = true;

   }

   return changed;

 }

 //---------------------------opnd_positions_match-------------------------

 // Is the use of d1 in u1 at the same operand position as d2 in u2?

 bool SuperWord::opnd_positions_match(Node* d1, Node* u1, Node* d2, Node* u2) {

   uint ct = u1->req();

   if (ct != u2->req()) return false;

   uint i1 = 0;

   uint i2 = 0;

   do {

     for (i1++; i1 < ct; i1++) if (u1->in(i1) == d1) break;

     for (i2++; i2 < ct; i2++) if (u2->in(i2) == d2) break;

     if (i1 != i2) {

       return false;

     }

   } while (i1 < ct);

   return true;

 }

 //------------------------------est_savings---------------------------

 // Estimate the savings from executing s1 and s2 as a pack

 int SuperWord::est_savings(Node* s1, Node* s2) {

   int save = 2 - 1; // 2 operations per instruction in packed form

   // inputs

   for (uint i = 1; i < s1->req(); i++) {

     Node* x1 = s1->in(i);

     Node* x2 = s2->in(i);

     if (x1 != x2) {

       if (are_adjacent_refs(x1, x2)) {

         save += adjacent_profit(x1, x2);

       } else if (!in_packset(x1, x2)) {

         save -= pack_cost(2);

       } else {

         save += unpack_cost(2);

       }

     }

   }

   // uses of result

   uint ct = 0;

   for (DUIterator_Fast imax, i = s1->fast_outs(imax); i < imax; i++) {

     Node* s1_use = s1->fast_out(i);

     for (int j = 0; j < _packset.length(); j++) {

       Node_List* p = _packset.at(j);

       if (p->at(0) == s1_use) {

         for (DUIterator_Fast kmax, k = s2->fast_outs(kmax); k < kmax; k++) {

           Node* s2_use = s2->fast_out(k);

           if (p->at(p->size()-1) == s2_use) {

             ct++;

             if (are_adjacent_refs(s1_use, s2_use)) {

               save += adjacent_profit(s1_use, s2_use);

             }

           }

         }

       }

     }

   }

   if (ct < s1->outcnt()) save += unpack_cost(1);

   if (ct < s2->outcnt()) save += unpack_cost(1);

   return save;

 }

 //------------------------------costs---------------------------

 int SuperWord::adjacent_profit(Node* s1, Node* s2) { return 2; }

 int SuperWord::pack_cost(int ct)   { return ct; }

 int SuperWord::unpack_cost(int ct) { return ct; }

 //------------------------------combine_packs---------------------------

 // Combine packs A and B with A.last == B.first into A.first..,A.last,B.second,..B.last

 void SuperWord::combine_packs() {

   bool changed;

   do {

     changed = false;

     for (int i = 0; i < _packset.length(); i++) {

       Node_List* p1 = _packset.at(i);

       if (p1 == NULL) continue;

       for (int j = 0; j < _packset.length(); j++) {

         Node_List* p2 = _packset.at(j);

         if (p2 == NULL) continue;

         if (p1->at(p1->size()-1) == p2->at(0)) {

           for (uint k = 1; k < p2->size(); k++) {

             p1->push(p2->at(k));

           }

           _packset.at_put(j, NULL);

           changed = true;

         }

       }

     }

   } while (changed);

   for (int i = _packset.length() - 1; i >= 0; i--) {

     Node_List* p1 = _packset.at(i);

     if (p1 == NULL) {

       _packset.remove_at(i);

     }

   }

 #ifndef PRODUCT

   if (TraceSuperWord) {

     tty->print_cr("\nAfter combine_packs");

     print_packset();

   }

 #endif

 }

 //-----------------------------construct_my_pack_map--------------------------

 // Construct the map from nodes to packs.  Only valid after the

 // point where a node is only in one pack (after combine_packs).

 void SuperWord::construct_my_pack_map() {

   Node_List* rslt = NULL;

   for (int i = 0; i < _packset.length(); i++) {

     Node_List* p = _packset.at(i);

     for (uint j = 0; j < p->size(); j++) {

       Node* s = p->at(j);

       assert(my_pack(s) == NULL, "only in one pack");

       set_my_pack(s, p);

     }

   }

 }

 //------------------------------filter_packs---------------------------

 // Remove packs that are not implemented or not profitable.

 void SuperWord::filter_packs() {

   // Remove packs that are not implemented

   for (int i = _packset.length() - 1; i >= 0; i--) {

     Node_List* pk = _packset.at(i);

     bool impl = implemented(pk);

     if (!impl) {

 #ifndef PRODUCT

       if (TraceSuperWord && Verbose) {

         tty->print_cr("Unimplemented");

         pk->at(0)->dump();

       }

 #endif

       remove_pack_at(i);

     }

   }

   // Remove packs that are not profitable

   bool changed;

   do {

     changed = false;

     for (int i = _packset.length() - 1; i >= 0; i--) {

       Node_List* pk = _packset.at(i);

       bool prof = profitable(pk);

       if (!prof) {

 #ifndef PRODUCT

         if (TraceSuperWord && Verbose) {

           tty->print_cr("Unprofitable");

           pk->at(0)->dump();

         }

 #endif

         remove_pack_at(i);

         changed = true;

       }

     }

   } while (changed);

 #ifndef PRODUCT

   if (TraceSuperWord) {

     tty->print_cr("\nAfter filter_packs");

     print_packset();

     tty->cr();

   }

 #endif

 }

 //------------------------------implemented---------------------------

 // Can code be generated for pack p?

 bool SuperWord::implemented(Node_List* p) {

   Node* p0 = p->at(0);

   int vopc = VectorNode::opcode(p0->Opcode(), p->size(), velt_type(p0));

   return vopc > 0 && Matcher::has_match_rule(vopc);

 }

 //------------------------------profitable---------------------------

 // For pack p, are all operands and all uses (with in the block) vector?

 bool SuperWord::profitable(Node_List* p) {

   Node* p0 = p->at(0);

   uint start, end;

   vector_opd_range(p0, &start, &end);

   // Return false if some input is not vector and inside block

   for (uint i = start; i < end; i++) {

     if (!is_vector_use(p0, i)) {

       // For now, return false if not scalar promotion case (inputs are the same.)

       // Later, implement PackNode and allow differing, non-vector inputs

       // (maybe just the ones from outside the block.)

       Node* p0_def = p0->in(i);

       for (uint j = 1; j < p->size(); j++) {

         Node* use = p->at(j);

         Node* def = use->in(i);

         if (p0_def != def)

           return false;

       }

     }

   }

   if (!p0->is_Store()) {

     // For now, return false if not all uses are vector.

     // Later, implement ExtractNode and allow non-vector uses (maybe

     // just the ones outside the block.)

     for (uint i = 0; i < p->size(); i++) {

       Node* def = p->at(i);

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

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

         for (uint k = 0; k < use->req(); k++) {

           Node* n = use->in(k);

           if (def == n) {

             if (!is_vector_use(use, k)) {

               return false;

             }

           }

         }

       }

     }

   }

   return true;

 }

 //------------------------------schedule---------------------------

 // Adjust the memory graph for the packed operations

 void SuperWord::schedule() {

   // Co-locate in the memory graph the members of each memory pack

   for (int i = 0; i < _packset.length(); i++) {

     co_locate_pack(_packset.at(i));

   }

 }

 //-------------------------------remove_and_insert-------------------

 //remove "current" from its current position in the memory graph and insert

 //it after the appropriate insertion point (lip or uip)

 void SuperWord::remove_and_insert(MemNode *current, MemNode *prev, MemNode *lip,

                                   Node *uip, Unique_Node_List &sched_before) {

   Node* my_mem = current->in(MemNode::Memory);

   _igvn.hash_delete(current);

   _igvn.hash_delete(my_mem);

   //remove current_store from its current position in the memmory graph

   for (DUIterator i = current->outs(); current->has_out(i); i++) {

     Node* use = current->out(i);

     if (use->is_Mem()) {

       assert(use->in(MemNode::Memory) == current, "must be");

       _igvn.hash_delete(use);

       if (use == prev) { // connect prev to my_mem

         use->set_req(MemNode::Memory, my_mem);

       } else if (sched_before.member(use)) {

         _igvn.hash_delete(uip);

         use->set_req(MemNode::Memory, uip);

       } else {

         _igvn.hash_delete(lip);

         use->set_req(MemNode::Memory, lip);

       }

       _igvn._worklist.push(use);

       --i; //deleted this edge; rescan position

     }

   }

   bool sched_up = sched_before.member(current);

   Node *insert_pt =  sched_up ?  uip : lip;

   _igvn.hash_delete(insert_pt);

   // all uses of insert_pt's memory state should use current's instead

   for (DUIterator i = insert_pt->outs(); insert_pt->has_out(i); i++) {

     Node* use = insert_pt->out(i);

     if (use->is_Mem()) {

       assert(use->in(MemNode::Memory) == insert_pt, "must be");

       _igvn.hash_delete(use);

       use->set_req(MemNode::Memory, current);

       _igvn._worklist.push(use);

       --i; //deleted this edge; rescan position

     } else if (!sched_up && use->is_Phi() && use->bottom_type() == Type::MEMORY) {

       uint pos; //lip (lower insert point) must be the last one in the memory slice

       _igvn.hash_delete(use);

       for (pos=1; pos < use->req(); pos++) {

         if (use->in(pos) == insert_pt) break;

       }

       use->set_req(pos, current);

       _igvn._worklist.push(use);

       --i;

     }

   }

   //connect current to insert_pt

   current->set_req(MemNode::Memory, insert_pt);

   _igvn._worklist.push(current);

 }

 //------------------------------co_locate_pack----------------------------------

 // To schedule a store pack, we need to move any sandwiched memory ops either before

 // or after the pack, based upon dependence information:

 // (1) If any store in the pack depends on the sandwiched memory op, the

 //     sandwiched memory op must be scheduled BEFORE the pack;

 // (2) If a sandwiched memory op depends on any store in the pack, the

 //     sandwiched memory op must be scheduled AFTER the pack;

 // (3) If a sandwiched memory op (say, memA) depends on another sandwiched

 //     memory op (say memB), memB must be scheduled before memA. So, if memA is

 //     scheduled before the pack, memB must also be scheduled before the pack;

 // (4) If there is no dependence restriction for a sandwiched memory op, we simply

 //     schedule this store AFTER the pack

 // (5) We know there is no dependence cycle, so there in no other case;

 // (6) Finally, all memory ops in another single pack should be moved in the same direction.

 //

 // To schedule a load pack, we use the memory state of either the first or the last load in

 // the pack, based on the dependence constraint.

 void SuperWord::co_locate_pack(Node_List* pk) {

   if (pk->at(0)->is_Store()) {

     MemNode* first     = executed_first(pk)->as_Mem();

     MemNode* last      = executed_last(pk)->as_Mem();

     Unique_Node_List schedule_before_pack;

     Unique_Node_List memops;

     MemNode* current   = last->in(MemNode::Memory)->as_Mem();

     MemNode* previous  = last;

     while (true) {

       assert(in_bb(current), "stay in block");

       memops.push(previous);

       for (DUIterator i = current->outs(); current->has_out(i); i++) {

         Node* use = current->out(i);

         if (use->is_Mem() && use != previous)

           memops.push(use);

       }

       if(current == first) break;

       previous = current;

       current  = current->in(MemNode::Memory)->as_Mem();

     }

     // determine which memory operations should be scheduled before the pack

     for (uint i = 1; i < memops.size(); i++) {

       Node *s1 = memops.at(i);

       if (!in_pack(s1, pk) && !schedule_before_pack.member(s1)) {

         for (uint j = 0; j< i; j++) {

           Node *s2 = memops.at(j);

           if (!independent(s1, s2)) {

             if (in_pack(s2, pk) || schedule_before_pack.member(s2)) {

               schedule_before_pack.push(s1); //s1 must be scheduled before

               Node_List* mem_pk = my_pack(s1);

               if (mem_pk != NULL) {

                 for (uint ii = 0; ii < mem_pk->size(); ii++) {

                   Node* s = mem_pk->at(ii); // follow partner

                   if (memops.member(s) && !schedule_before_pack.member(s))

                     schedule_before_pack.push(s);

                 }

               }

             }

           }

         }

       }

     }

     MemNode* lower_insert_pt = last;

     Node*    upper_insert_pt = first->in(MemNode::Memory);

     previous                 = last; //previous store in pk

     current                  = last->in(MemNode::Memory)->as_Mem();

     //start scheduling from "last" to "first"

     while (true) {

       assert(in_bb(current), "stay in block");

       assert(in_pack(previous, pk), "previous stays in pack");

       Node* my_mem = current->in(MemNode::Memory);

       if (in_pack(current, pk)) {

         // Forward users of my memory state (except "previous) to my input memory state

         _igvn.hash_delete(current);

         for (DUIterator i = current->outs(); current->has_out(i); i++) {

           Node* use = current->out(i);

           if (use->is_Mem() && use != previous) {

             assert(use->in(MemNode::Memory) == current, "must be");

             _igvn.hash_delete(use);

             if (schedule_before_pack.member(use)) {

               _igvn.hash_delete(upper_insert_pt);

               use->set_req(MemNode::Memory, upper_insert_pt);

             } else {

               _igvn.hash_delete(lower_insert_pt);

               use->set_req(MemNode::Memory, lower_insert_pt);

             }

             _igvn._worklist.push(use);

             --i; // deleted this edge; rescan position

           }

         }

         previous = current;

       } else { // !in_pack(current, pk) ==> a sandwiched store

         remove_and_insert(current, previous, lower_insert_pt, upper_insert_pt, schedule_before_pack);

       }

       if (current == first) break;

       current = my_mem->as_Mem();

     } // end while

   } else if (pk->at(0)->is_Load()) { //load

     // all loads in the pack should have the same memory state. By default,

     // we use the memory state of the last load. However, if any load could

     // not be moved down due to the dependence constraint, we use the memory

     // state of the first load.

     Node* last_mem  = executed_last(pk)->in(MemNode::Memory);

     Node* first_mem = executed_first(pk)->in(MemNode::Memory);

     bool schedule_last = true;

     for (uint i = 0; i < pk->size(); i++) {

       Node* ld = pk->at(i);

       for (Node* current = last_mem; current != ld->in(MemNode::Memory);

            current=current->in(MemNode::Memory)) {

         assert(current != first_mem, "corrupted memory graph");

         if(current->is_Mem() && !independent(current, ld)){

           schedule_last = false; // a later store depends on this load

           break;

         }

       }

     }

     Node* mem_input = schedule_last ? last_mem : first_mem;

     _igvn.hash_delete(mem_input);

     // Give each load the same memory state

     for (uint i = 0; i < pk->size(); i++) {

       LoadNode* ld = pk->at(i)->as_Load();

       _igvn.hash_delete(ld);

       ld->set_req(MemNode::Memory, mem_input);

       _igvn._worklist.push(ld);

     }

   }

 }

 //------------------------------output---------------------------

 // Convert packs into vector node operations

 void SuperWord::output() {

   if (_packset.length() == 0) return;

 #ifndef PRODUCT

   if (TraceLoopOpts) {

     tty->print("SuperWord    ");

     lpt()->dump_head();

   }

 #endif

   // MUST ENSURE main loop's initial value is properly aligned:

   //  (iv_initial_value + min_iv_offset) % vector_width_in_bytes() == 0

   align_initial_loop_index(align_to_ref());

   // Insert extract (unpack) operations for scalar uses

   for (int i = 0; i < _packset.length(); i++) {

     insert_extracts(_packset.at(i));

   }

   for (int i = 0; i < _block.length(); i++) {

     Node* n = _block.at(i);

     Node_List* p = my_pack(n);

     if (p && n == executed_last(p)) {

       uint vlen = p->size();

       Node* vn = NULL;

       Node* low_adr = p->at(0);

       Node* first   = executed_first(p);

       if (n->is_Load()) {

         int   opc = n->Opcode();

         Node* ctl = n->in(MemNode::Control);

         Node* mem = first->in(MemNode::Memory);

         Node* adr = low_adr->in(MemNode::Address);

         const TypePtr* atyp = n->adr_type();

         vn = VectorLoadNode::make(_phase->C, opc, ctl, mem, adr, atyp, vlen);

       } else if (n->is_Store()) {

         // Promote value to be stored to vector

         Node* val = vector_opd(p, MemNode::ValueIn);

         int   opc = n->Opcode();

         Node* ctl = n->in(MemNode::Control);

         Node* mem = first->in(MemNode::Memory);

         Node* adr = low_adr->in(MemNode::Address);

         const TypePtr* atyp = n->adr_type();

         vn = VectorStoreNode::make(_phase->C, opc, ctl, mem, adr, atyp, val, vlen);

       } else if (n->req() == 3) {

         // Promote operands to vector

         Node* in1 = vector_opd(p, 1);

         Node* in2 = vector_opd(p, 2);

         vn = VectorNode::make(_phase->C, n->Opcode(), in1, in2, vlen, velt_type(n));

       } else {

         ShouldNotReachHere();

       }

       _phase->_igvn.register_new_node_with_optimizer(vn);

       _phase->set_ctrl(vn, _phase->get_ctrl(p->at(0)));

       for (uint j = 0; j < p->size(); j++) {

         Node* pm = p->at(j);

         _igvn.replace_node(pm, vn);

       }

       _igvn._worklist.push(vn);

     }

   }

 }

 //------------------------------vector_opd---------------------------

 // Create a vector operand for the nodes in pack p for operand: in(opd_idx)

 Node* SuperWord::vector_opd(Node_List* p, int opd_idx) {

   Node* p0 = p->at(0);

   uint vlen = p->size();

   Node* opd = p0->in(opd_idx);

   bool same_opd = true;

   for (uint i = 1; i < vlen; i++) {

     Node* pi = p->at(i);

     Node* in = pi->in(opd_idx);

     if (opd != in) {

       same_opd = false;

       break;

     }

   }

   if (same_opd) {

     if (opd->is_Vector() || opd->is_VectorLoad()) {

       return opd; // input is matching vector

     }

     assert(!opd->is_VectorStore(), "such vector is not expected here");

     // Convert scalar input to vector. Use p0's type because it's container

     // maybe smaller than the operand's container.

     const Type* opd_t = velt_type(!in_bb(opd) ? p0 : opd);

     const Type* p0_t  = velt_type(p0);

     if (p0_t->higher_equal(opd_t)) opd_t = p0_t;

     VectorNode* vn    = VectorNode::scalar2vector(_phase->C, opd, vlen, opd_t);

     _phase->_igvn.register_new_node_with_optimizer(vn);

     _phase->set_ctrl(vn, _phase->get_ctrl(opd));

     return vn;

   }

   // Insert pack operation

   const Type* opd_t = velt_type(!in_bb(opd) ? p0 : opd);

   PackNode* pk = PackNode::make(_phase->C, opd, opd_t);

   for (uint i = 1; i < vlen; i++) {

     Node* pi = p->at(i);

     Node* in = pi->in(opd_idx);

     assert(my_pack(in) == NULL, "Should already have been unpacked");

     assert(opd_t == velt_type(!in_bb(in) ? pi : in), "all same type");

     pk->add_opd(in);

   }

   _phase->_igvn.register_new_node_with_optimizer(pk);

   _phase->set_ctrl(pk, _phase->get_ctrl(opd));

   return pk;

 }

 //------------------------------insert_extracts---------------------------

 // If a use of pack p is not a vector use, then replace the

 // use with an extract operation.

 void SuperWord::insert_extracts(Node_List* p) {

   if (p->at(0)->is_Store()) return;

   assert(_n_idx_list.is_empty(), "empty (node,index) list");

   // Inspect each use of each pack member.  For each use that is

   // not a vector use, replace the use with an extract operation.

   for (uint i = 0; i < p->size(); i++) {

     Node* def = p->at(i);

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

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

       for (uint k = 0; k < use->req(); k++) {

         Node* n = use->in(k);

         if (def == n) {

           if (!is_vector_use(use, k)) {

             _n_idx_list.push(use, k);

           }

         }

       }

     }

   }

   while (_n_idx_list.is_nonempty()) {

     Node* use = _n_idx_list.node();

     int   idx = _n_idx_list.index();

     _n_idx_list.pop();

     Node* def = use->in(idx);

     // Insert extract operation

     _igvn.hash_delete(def);

     _igvn.hash_delete(use);

     int def_pos = alignment(def) / data_size(def);

     const Type* def_t = velt_type(def);

     Node* ex = ExtractNode::make(_phase->C, def, def_pos, def_t);

     _phase->_igvn.register_new_node_with_optimizer(ex);

     _phase->set_ctrl(ex, _phase->get_ctrl(def));

     use->set_req(idx, ex);

     _igvn._worklist.push(def);

     _igvn._worklist.push(use);

     bb_insert_after(ex, bb_idx(def));

     set_velt_type(ex, def_t);

   }

 }

 //------------------------------is_vector_use---------------------------

 // Is use->in(u_idx) a vector use?

 bool SuperWord::is_vector_use(Node* use, int u_idx) {

   Node_List* u_pk = my_pack(use);

   if (u_pk == NULL) return false;

   Node* def = use->in(u_idx);

   Node_List* d_pk = my_pack(def);

   if (d_pk == NULL) {

     // check for scalar promotion

     Node* n = u_pk->at(0)->in(u_idx);

     for (uint i = 1; i < u_pk->size(); i++) {

       if (u_pk->at(i)->in(u_idx) != n) return false;

     }

     return true;

   }

   if (u_pk->size() != d_pk->size())

     return false;

   for (uint i = 0; i < u_pk->size(); i++) {

     Node* ui = u_pk->at(i);

     Node* di = d_pk->at(i);

     if (ui->in(u_idx) != di || alignment(ui) != alignment(di))

       return false;

   }

   return true;

 }

 //------------------------------construct_bb---------------------------

 // Construct reverse postorder list of block members

 void SuperWord::construct_bb() {

   Node* entry = bb();

   assert(_stk.length() == 0,            "stk is empty");

   assert(_block.length() == 0,          "block is empty");

   assert(_data_entry.length() == 0,     "data_entry is empty");

   assert(_mem_slice_head.length() == 0, "mem_slice_head is empty");

   assert(_mem_slice_tail.length() == 0, "mem_slice_tail is empty");

   // Find non-control nodes with no inputs from within block,

   // create a temporary map from node _idx to bb_idx for use

   // by the visited and post_visited sets,

   // and count number of nodes in block.

   int bb_ct = 0;

   for (uint i = 0; i < lpt()->_body.size(); i++ ) {

     Node *n = lpt()->_body.at(i);

     set_bb_idx(n, i); // Create a temporary map

     if (in_bb(n)) {

       bb_ct++;

       if (!n->is_CFG()) {

         bool found = false;

         for (uint j = 0; j < n->req(); j++) {

           Node* def = n->in(j);

           if (def && in_bb(def)) {

             found = true;

             break;

           }

         }

         if (!found) {

           assert(n != entry, "can't be entry");

           _data_entry.push(n);

         }

       }

     }

   }

   // Find memory slices (head and tail)

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

     Node *n = lp()->fast_out(i);

     if (in_bb(n) && (n->is_Phi() && n->bottom_type() == Type::MEMORY)) {

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

       if (n_tail != n->in(LoopNode::EntryControl)) {

         _mem_slice_head.push(n);

         _mem_slice_tail.push(n_tail);

       }

     }

   }

   // Create an RPO list of nodes in block

   visited_clear();

   post_visited_clear();

   // Push all non-control nodes with no inputs from within block, then control entry

   for (int j = 0; j < _data_entry.length(); j++) {

     Node* n = _data_entry.at(j);

     visited_set(n);

     _stk.push(n);

   }

   visited_set(entry);

   _stk.push(entry);

   // Do a depth first walk over out edges

   int rpo_idx = bb_ct - 1;

   int size;

   while ((size = _stk.length()) > 0) {

     Node* n = _stk.top(); // Leave node on stack

     if (!visited_test_set(n)) {

       // forward arc in graph

     } else if (!post_visited_test(n)) {

       // cross or back arc

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

         Node *use = n->fast_out(i);

         if (in_bb(use) && !visited_test(use) &&

             // Don't go around backedge

             (!use->is_Phi() || n == entry)) {

           _stk.push(use);

         }

       }

       if (_stk.length() == size) {

         // There were no additional uses, post visit node now

         _stk.pop(); // Remove node from stack

         assert(rpo_idx >= 0, "");

         _block.at_put_grow(rpo_idx, n);

         rpo_idx--;

         post_visited_set(n);

         assert(rpo_idx >= 0 || _stk.is_empty(), "");

       }

     } else {

       _stk.pop(); // Remove post-visited node from stack

     }

   }

   // Create real map of block indices for nodes

   for (int j = 0; j < _block.length(); j++) {

     Node* n = _block.at(j);

     set_bb_idx(n, j);

   }

   initialize_bb(); // Ensure extra info is allocated.

 #ifndef PRODUCT

   if (TraceSuperWord) {

     print_bb();

     tty->print_cr("\ndata entry nodes: %s", _data_entry.length() > 0 ? "" : "NONE");

     for (int m = 0; m < _data_entry.length(); m++) {

       tty->print("%3d ", m);

       _data_entry.at(m)->dump();

     }

     tty->print_cr("\nmemory slices: %s", _mem_slice_head.length() > 0 ? "" : "NONE");

     for (int m = 0; m < _mem_slice_head.length(); m++) {

       tty->print("%3d ", m); _mem_slice_head.at(m)->dump();

       tty->print("    ");    _mem_slice_tail.at(m)->dump();

     }

   }

 #endif

   assert(rpo_idx == -1 && bb_ct == _block.length(), "all block members found");

 }

 //------------------------------initialize_bb---------------------------

 // Initialize per node info

 void SuperWord::initialize_bb() {

   Node* last = _block.at(_block.length() - 1);

   grow_node_info(bb_idx(last));

 }

 //------------------------------bb_insert_after---------------------------

 // Insert n into block after pos

 void SuperWord::bb_insert_after(Node* n, int pos) {

   int n_pos = pos + 1;

   // Make room

   for (int i = _block.length() - 1; i >= n_pos; i--) {

     _block.at_put_grow(i+1, _block.at(i));

   }

   for (int j = _node_info.length() - 1; j >= n_pos; j--) {

     _node_info.at_put_grow(j+1, _node_info.at(j));

   }

   // Set value

   _block.at_put_grow(n_pos, n);

   _node_info.at_put_grow(n_pos, SWNodeInfo::initial);

   // Adjust map from node->_idx to _block index

   for (int i = n_pos; i < _block.length(); i++) {

     set_bb_idx(_block.at(i), i);

   }

 }

 //------------------------------compute_max_depth---------------------------

 // Compute max depth for expressions from beginning of block

 // Use to prune search paths during test for independence.

 void SuperWord::compute_max_depth() {

   int ct = 0;

   bool again;

   do {

     again = false;

     for (int i = 0; i < _block.length(); i++) {

       Node* n = _block.at(i);

       if (!n->is_Phi()) {

         int d_orig = depth(n);

         int d_in   = 0;

         for (DepPreds preds(n, _dg); !preds.done(); preds.next()) {

           Node* pred = preds.current();

           if (in_bb(pred)) {

             d_in = MAX2(d_in, depth(pred));

           }

         }

         if (d_in + 1 != d_orig) {

           set_depth(n, d_in + 1);

           again = true;

         }

       }

     }

     ct++;

   } while (again);

 #ifndef PRODUCT

   if (TraceSuperWord && Verbose)

     tty->print_cr("compute_max_depth iterated: %d times", ct);

 #endif

 }

 //-------------------------compute_vector_element_type-----------------------

 // Compute necessary vector element type for expressions

 // This propagates backwards a narrower integer type when the

 // upper bits of the value are not needed.

 // Example:  char a,b,c;  a = b + c;

 // Normally the type of the add is integer, but for packed character

 // operations the type of the add needs to be char.

 void SuperWord::compute_vector_element_type() {

 #ifndef PRODUCT

   if (TraceSuperWord && Verbose)

     tty->print_cr("\ncompute_velt_type:");

 #endif

   // Initial type

   for (int i = 0; i < _block.length(); i++) {

     Node* n = _block.at(i);

     const Type* t  = n->is_Mem() ? Type::get_const_basic_type(n->as_Mem()->memory_type())

                                  : _igvn.type(n);

     const Type* vt = container_type(t);

     set_velt_type(n, vt);

   }

   // Propagate narrowed type backwards through operations

   // that don't depend on higher order bits

   for (int i = _block.length() - 1; i >= 0; i--) {

     Node* n = _block.at(i);

     // Only integer types need be examined

     if (n->bottom_type()->isa_int()) {

       uint start, end;

       vector_opd_range(n, &start, &end);

       const Type* vt = velt_type(n);

       for (uint j = start; j < end; j++) {

         Node* in  = n->in(j);

         // Don't propagate through a type conversion

         if (n->bottom_type() != in->bottom_type())

           continue;

         switch(in->Opcode()) {

         case Op_AddI:    case Op_AddL:

         case Op_SubI:    case Op_SubL:

         case Op_MulI:    case Op_MulL:

         case Op_AndI:    case Op_AndL:

         case Op_OrI:     case Op_OrL:

         case Op_XorI:    case Op_XorL:

         case Op_LShiftI: case Op_LShiftL:

         case Op_CMoveI:  case Op_CMoveL:

           if (in_bb(in)) {

             bool same_type = true;

             for (DUIterator_Fast kmax, k = in->fast_outs(kmax); k < kmax; k++) {

               Node *use = in->fast_out(k);

               if (!in_bb(use) || velt_type(use) != vt) {

                 same_type = false;

                 break;

               }

             }

             if (same_type) {

               set_velt_type(in, vt);

             }

           }

         }

       }

     }

   }

 #ifndef PRODUCT

   if (TraceSuperWord && Verbose) {

     for (int i = 0; i < _block.length(); i++) {

       Node* n = _block.at(i);

       velt_type(n)->dump();

       tty->print("\t");

       n->dump();

     }

   }

 #endif

 }

 //------------------------------memory_alignment---------------------------

 // Alignment within a vector memory reference

 int SuperWord::memory_alignment(MemNode* s, int iv_adjust_in_bytes) {

   SWPointer p(s, this);

   if (!p.valid()) {

     return bottom_align;

   }

   int offset  = p.offset_in_bytes();

   offset     += iv_adjust_in_bytes;

   int off_rem = offset % vector_width_in_bytes();

   int off_mod = off_rem >= 0 ? off_rem : off_rem + vector_width_in_bytes();

   return off_mod;

 }

 //---------------------------container_type---------------------------

 // Smallest type containing range of values

 const Type* SuperWord::container_type(const Type* t) {

   const Type* tp = t->make_ptr();

   if (tp && tp->isa_aryptr()) {

     t = tp->is_aryptr()->elem();

   }

   if (t->basic_type() == T_INT) {

     if (t->higher_equal(TypeInt::BOOL))  return TypeInt::BOOL;

     if (t->higher_equal(TypeInt::BYTE))  return TypeInt::BYTE;

     if (t->higher_equal(TypeInt::CHAR))  return TypeInt::CHAR;

     if (t->higher_equal(TypeInt::SHORT)) return TypeInt::SHORT;

     return TypeInt::INT;

   }

   return t;

 }

 //-------------------------vector_opd_range-----------------------

 // (Start, end] half-open range defining which operands are vector

 void SuperWord::vector_opd_range(Node* n, uint* start, uint* end) {

   switch (n->Opcode()) {

   case Op_LoadB:   case Op_LoadUS:

   case Op_LoadI:   case Op_LoadL:

   case Op_LoadF:   case Op_LoadD:

   case Op_LoadP:

     *start = 0;

     *end   = 0;

     return;

   case Op_StoreB:  case Op_StoreC:

   case Op_StoreI:  case Op_StoreL:

   case Op_StoreF:  case Op_StoreD:

   case Op_StoreP:

     *start = MemNode::ValueIn;

     *end   = *start + 1;

     return;

   case Op_LShiftI: case Op_LShiftL:

     *start = 1;

     *end   = 2;

     return;

   case Op_CMoveI:  case Op_CMoveL:  case Op_CMoveF:  case Op_CMoveD:

     *start = 2;

     *end   = n->req();

     return;

   }

   *start = 1;

   *end   = n->req(); // default is all operands

 }

 //------------------------------in_packset---------------------------

 // Are s1 and s2 in a pack pair and ordered as s1,s2?

 bool SuperWord::in_packset(Node* s1, Node* s2) {

   for (int i = 0; i < _packset.length(); i++) {

     Node_List* p = _packset.at(i);

     assert(p->size() == 2, "must be");

     if (p->at(0) == s1 && p->at(p->size()-1) == s2) {

       return true;

     }

   }

   return false;

 }

 //------------------------------in_pack---------------------------

 // Is s in pack p?

 Node_List* SuperWord::in_pack(Node* s, Node_List* p) {

   for (uint i = 0; i < p->size(); i++) {

     if (p->at(i) == s) {

       return p;

     }

   }

   return NULL;

 }

 //------------------------------remove_pack_at---------------------------

 // Remove the pack at position pos in the packset

 void SuperWord::remove_pack_at(int pos) {

   Node_List* p = _packset.at(pos);

   for (uint i = 0; i < p->size(); i++) {

     Node* s = p->at(i);

     set_my_pack(s, NULL);

   }

   _packset.remove_at(pos);

 }

 //------------------------------executed_first---------------------------

 // Return the node executed first in pack p.  Uses the RPO block list

 // to determine order.

 Node* SuperWord::executed_first(Node_List* p) {

   Node* n = p->at(0);

   int n_rpo = bb_idx(n);

   for (uint i = 1; i < p->size(); i++) {

     Node* s = p->at(i);

     int s_rpo = bb_idx(s);

     if (s_rpo < n_rpo) {

       n = s;

       n_rpo = s_rpo;

     }

   }

   return n;

 }

 //------------------------------executed_last---------------------------

 // Return the node executed last in pack p.

 Node* SuperWord::executed_last(Node_List* p) {

   Node* n = p->at(0);

   int n_rpo = bb_idx(n);

   for (uint i = 1; i < p->size(); i++) {

     Node* s = p->at(i);

     int s_rpo = bb_idx(s);

     if (s_rpo > n_rpo) {

       n = s;

       n_rpo = s_rpo;

     }

   }

   return n;

 }

 //----------------------------align_initial_loop_index---------------------------

 // Adjust pre-loop limit so that in main loop, a load/store reference

 // to align_to_ref will be a position zero in the vector.

 //   (iv + k) mod vector_align == 0

 void SuperWord::align_initial_loop_index(MemNode* align_to_ref) {

   CountedLoopNode *main_head = lp()->as_CountedLoop();

   assert(main_head->is_main_loop(), "");

   CountedLoopEndNode* pre_end = get_pre_loop_end(main_head);

   assert(pre_end != NULL, "");

   Node *pre_opaq1 = pre_end->limit();

   assert(pre_opaq1->Opcode() == Op_Opaque1, "");

   Opaque1Node *pre_opaq = (Opaque1Node*)pre_opaq1;

   Node *lim0 = pre_opaq->in(1);

   // Where we put new limit calculations

   Node *pre_ctrl = pre_end->loopnode()->in(LoopNode::EntryControl);

   // Ensure the original loop limit is available from the

   // pre-loop Opaque1 node.

   Node *orig_limit = pre_opaq->original_loop_limit();

   assert(orig_limit != NULL && _igvn.type(orig_limit) != Type::TOP, "");

   SWPointer align_to_ref_p(align_to_ref, this);

   // Given:

   //     lim0 == original pre loop limit

   //     V == v_align (power of 2)

   //     invar == extra invariant piece of the address expression

   //     e == k [ +/- invar ]

   //

   // When reassociating expressions involving '%' the basic rules are:

   //     (a - b) % k == 0   =>  a % k == b % k

   // and:

   //     (a + b) % k == 0   =>  a % k == (k - b) % k

   //

   // For stride > 0 && scale > 0,

   //   Derive the new pre-loop limit "lim" such that the two constraints:

   //     (1) lim = lim0 + N           (where N is some positive integer < V)

   //     (2) (e + lim) % V == 0

   //   are true.

   //

   //   Substituting (1) into (2),

   //     (e + lim0 + N) % V == 0

   //   solve for N:

   //     N = (V - (e + lim0)) % V

   //   substitute back into (1), so that new limit

   //     lim = lim0 + (V - (e + lim0)) % V

   //

   // For stride > 0 && scale < 0

   //   Constraints:

   //     lim = lim0 + N

   //     (e - lim) % V == 0

   //   Solving for lim:

   //     (e - lim0 - N) % V == 0

   //     N = (e - lim0) % V

   //     lim = lim0 + (e - lim0) % V

   //

   // For stride < 0 && scale > 0

   //   Constraints:

   //     lim = lim0 - N

   //     (e + lim) % V == 0

   //   Solving for lim:

   //     (e + lim0 - N) % V == 0

   //     N = (e + lim0) % V

   //     lim = lim0 - (e + lim0) % V

   //

   // For stride < 0 && scale < 0

   //   Constraints:

   //     lim = lim0 - N

   //     (e - lim) % V == 0

   //   Solving for lim:

   //     (e - lim0 + N) % V == 0

   //     N = (V - (e - lim0)) % V

   //     lim = lim0 - (V - (e - lim0)) % V

   int stride   = iv_stride();

   int scale    = align_to_ref_p.scale_in_bytes();

   int elt_size = align_to_ref_p.memory_size();

   int v_align  = vector_width_in_bytes() / elt_size;

   int k        = align_to_ref_p.offset_in_bytes() / elt_size;

   Node *kn   = _igvn.intcon(k);

   Node *e = kn;

   if (align_to_ref_p.invar() != NULL) {

     // incorporate any extra invariant piece producing k +/- invar >>> log2(elt)

     Node* log2_elt = _igvn.intcon(exact_log2(elt_size));

     Node* aref     = new (_phase->C, 3) URShiftINode(align_to_ref_p.invar(), log2_elt);

     _phase->_igvn.register_new_node_with_optimizer(aref);

     _phase->set_ctrl(aref, pre_ctrl);

     if (align_to_ref_p.negate_invar()) {

       e = new (_phase->C, 3) SubINode(e, aref);

     } else {

       e = new (_phase->C, 3) AddINode(e, aref);

     }

     _phase->_igvn.register_new_node_with_optimizer(e);

     _phase->set_ctrl(e, pre_ctrl);

   }

   // compute e +/- lim0

   if (scale < 0) {

     e = new (_phase->C, 3) SubINode(e, lim0);

   } else {

     e = new (_phase->C, 3) AddINode(e, lim0);

   }

   _phase->_igvn.register_new_node_with_optimizer(e);

   _phase->set_ctrl(e, pre_ctrl);

   if (stride * scale > 0) {

     // compute V - (e +/- lim0)

     Node* va  = _igvn.intcon(v_align);

     e = new (_phase->C, 3) SubINode(va, e);

     _phase->_igvn.register_new_node_with_optimizer(e);

     _phase->set_ctrl(e, pre_ctrl);

   }

   // compute N = (exp) % V

   Node* va_msk = _igvn.intcon(v_align - 1);

   Node* N = new (_phase->C, 3) AndINode(e, va_msk);

   _phase->_igvn.register_new_node_with_optimizer(N);

   _phase->set_ctrl(N, pre_ctrl);

   //   substitute back into (1), so that new limit

   //     lim = lim0 + N

   Node* lim;

   if (stride < 0) {

     lim = new (_phase->C, 3) SubINode(lim0, N);

   } else {

     lim = new (_phase->C, 3) AddINode(lim0, N);

   }

   _phase->_igvn.register_new_node_with_optimizer(lim);

   _phase->set_ctrl(lim, pre_ctrl);

   Node* constrained =

     (stride > 0) ? (Node*) new (_phase->C,3) MinINode(lim, orig_limit)

                  : (Node*) new (_phase->C,3) MaxINode(lim, orig_limit);

   _phase->_igvn.register_new_node_with_optimizer(constrained);

   _phase->set_ctrl(constrained, pre_ctrl);

   _igvn.hash_delete(pre_opaq);

   pre_opaq->set_req(1, constrained);

 }

 //----------------------------get_pre_loop_end---------------------------

 // Find pre loop end from main loop.  Returns null if none.

 CountedLoopEndNode* SuperWord::get_pre_loop_end(CountedLoopNode *cl) {

   Node *ctrl = cl->in(LoopNode::EntryControl);

   if (!ctrl->is_IfTrue() && !ctrl->is_IfFalse()) return NULL;

   Node *iffm = ctrl->in(0);

   if (!iffm->is_If()) return NULL;

   Node *p_f = iffm->in(0);

   if (!p_f->is_IfFalse()) return NULL;

   if (!p_f->in(0)->is_CountedLoopEnd()) return NULL;

   CountedLoopEndNode *pre_end = p_f->in(0)->as_CountedLoopEnd();

   if (!pre_end->loopnode()->is_pre_loop()) return NULL;

   return pre_end;

 }

 //------------------------------init---------------------------

 void SuperWord::init() {

   _dg.init();

   _packset.clear();

   _disjoint_ptrs.clear();

   _block.clear();

   _data_entry.clear();

   _mem_slice_head.clear();

   _mem_slice_tail.clear();

   _node_info.clear();

   _align_to_ref = NULL;

   _lpt = NULL;

   _lp = NULL;

   _bb = NULL;

   _iv = NULL;

 }

 //------------------------------print_packset---------------------------

 void SuperWord::print_packset() {

 #ifndef PRODUCT

   tty->print_cr("packset");

   for (int i = 0; i < _packset.length(); i++) {

     tty->print_cr("Pack: %d", i);

     Node_List* p = _packset.at(i);

     print_pack(p);

   }

 #endif

 }

 //------------------------------print_pack---------------------------

 void SuperWord::print_pack(Node_List* p) {

   for (uint i = 0; i < p->size(); i++) {

     print_stmt(p->at(i));

   }

 }

 //------------------------------print_bb---------------------------

 void SuperWord::print_bb() {

 #ifndef PRODUCT

   tty->print_cr("\nBlock");

   for (int i = 0; i < _block.length(); i++) {

     Node* n = _block.at(i);

     tty->print("%d ", i);

     if (n) {

       n->dump();

     }

   }

 #endif

 }

 //------------------------------print_stmt---------------------------

 void SuperWord::print_stmt(Node* s) {

 #ifndef PRODUCT

   tty->print(" align: %d \t", alignment(s));

   s->dump();

 #endif

 }

 //------------------------------blank---------------------------

 char* SuperWord::blank(uint depth) {

   static char blanks[101];

   assert(depth < 101, "too deep");

   for (uint i = 0; i < depth; i++) blanks[i] = ' ';

   blanks[depth] = '\0';

   return blanks;

 }

 //==============================SWPointer===========================

 //----------------------------SWPointer------------------------

 SWPointer::SWPointer(MemNode* mem, SuperWord* slp) :

   _mem(mem), _slp(slp),  _base(NULL),  _adr(NULL),

   _scale(0), _offset(0), _invar(NULL), _negate_invar(false) {

   Node* adr = mem->in(MemNode::Address);

   if (!adr->is_AddP()) {

     assert(!valid(), "too complex");

     return;

   }

   // Match AddP(base, AddP(ptr, k*iv [+ invariant]), constant)

   Node* base = adr->in(AddPNode::Base);

   //unsafe reference could not be aligned appropriately without runtime checking

   if (base == NULL || base->bottom_type() == Type::TOP) {

     assert(!valid(), "unsafe access");

     return;

   }

   for (int i = 0; i < 3; i++) {

     if (!scaled_iv_plus_offset(adr->in(AddPNode::Offset))) {

       assert(!valid(), "too complex");

       return;

     }

     adr = adr->in(AddPNode::Address);

     if (base == adr || !adr->is_AddP()) {

       break; // stop looking at addp's

     }

   }

   _base = base;

   _adr  = adr;

   assert(valid(), "Usable");

 }

 // Following is used to create a temporary object during

 // the pattern match of an address expression.

 SWPointer::SWPointer(SWPointer* p) :

   _mem(p->_mem), _slp(p->_slp),  _base(NULL),  _adr(NULL),

   _scale(0), _offset(0), _invar(NULL), _negate_invar(false) {}

 //------------------------scaled_iv_plus_offset--------------------

 // Match: k*iv + offset

 // where: k is a constant that maybe zero, and

 //        offset is (k2 [+/- invariant]) where k2 maybe zero and invariant is optional

 bool SWPointer::scaled_iv_plus_offset(Node* n) {

   if (scaled_iv(n)) {

     return true;

   }

   if (offset_plus_k(n)) {

     return true;

   }

   int opc = n->Opcode();

   if (opc == Op_AddI) {

     if (scaled_iv(n->in(1)) && offset_plus_k(n->in(2))) {

       return true;

     }

     if (scaled_iv(n->in(2)) && offset_plus_k(n->in(1))) {

       return true;

     }

   } else if (opc == Op_SubI) {

     if (scaled_iv(n->in(1)) && offset_plus_k(n->in(2), true)) {

       return true;

     }

     if (scaled_iv(n->in(2)) && offset_plus_k(n->in(1))) {

       _scale *= -1;

       return true;

     }

   }

   return false;

 }

 //----------------------------scaled_iv------------------------

 // Match: k*iv where k is a constant that's not zero

 bool SWPointer::scaled_iv(Node* n) {

   if (_scale != 0) {

     return false;  // already found a scale

   }

   if (n == iv()) {

     _scale = 1;

     return true;

   }

   int opc = n->Opcode();

   if (opc == Op_MulI) {

     if (n->in(1) == iv() && n->in(2)->is_Con()) {

       _scale = n->in(2)->get_int();

       return true;

     } else if (n->in(2) == iv() && n->in(1)->is_Con()) {

       _scale = n->in(1)->get_int();

       return true;

     }

   } else if (opc == Op_LShiftI) {

     if (n->in(1) == iv() && n->in(2)->is_Con()) {

       _scale = 1 << n->in(2)->get_int();

       return true;

     }

   } else if (opc == Op_ConvI2L) {

     if (scaled_iv_plus_offset(n->in(1))) {

       return true;

     }

   } else if (opc == Op_LShiftL) {

     if (!has_iv() && _invar == NULL) {

       // Need to preserve the current _offset value, so

       // create a temporary object for this expression subtree.

       // Hacky, so should re-engineer the address pattern match.

       SWPointer tmp(this);

       if (tmp.scaled_iv_plus_offset(n->in(1))) {

         if (tmp._invar == NULL) {

           int mult = 1 << n->in(2)->get_int();

           _scale   = tmp._scale  * mult;

           _offset += tmp._offset * mult;

           return true;

         }

       }

     }

   }

   return false;

 }

 //----------------------------offset_plus_k------------------------

 // Match: offset is (k [+/- invariant])

 // where k maybe zero and invariant is optional, but not both.

 bool SWPointer::offset_plus_k(Node* n, bool negate) {

   int opc = n->Opcode();

   if (opc == Op_ConI) {

     _offset += negate ? -(n->get_int()) : n->get_int();

     return true;

   } else if (opc == Op_ConL) {

     // Okay if value fits into an int

     const TypeLong* t = n->find_long_type();

     if (t->higher_equal(TypeLong::INT)) {

       jlong loff = n->get_long();

       jint  off  = (jint)loff;

       _offset += negate ? -off : loff;

       return true;

     }

     return false;

   }

   if (_invar != NULL) return false; // already have an invariant

   if (opc == Op_AddI) {

     if (n->in(2)->is_Con() && invariant(n->in(1))) {

       _negate_invar = negate;

       _invar = n->in(1);

       _offset += negate ? -(n->in(2)->get_int()) : n->in(2)->get_int();

       return true;

     } else if (n->in(1)->is_Con() && invariant(n->in(2))) {

       _offset += negate ? -(n->in(1)->get_int()) : n->in(1)->get_int();

       _negate_invar = negate;

       _invar = n->in(2);

       return true;

     }

   }

   if (opc == Op_SubI) {

     if (n->in(2)->is_Con() && invariant(n->in(1))) {

       _negate_invar = negate;

       _invar = n->in(1);

       _offset += !negate ? -(n->in(2)->get_int()) : n->in(2)->get_int();

       return true;

     } else if (n->in(1)->is_Con() && invariant(n->in(2))) {

       _offset += negate ? -(n->in(1)->get_int()) : n->in(1)->get_int();

       _negate_invar = !negate;

       _invar = n->in(2);

       return true;

     }

   }

   if (invariant(n)) {

     _negate_invar = negate;

     _invar = n;

     return true;

   }

   return false;

 }

 //----------------------------print------------------------

 void SWPointer::print() {

 #ifndef PRODUCT

   tty->print("base: %d  adr: %d  scale: %d  offset: %d  invar: %c%d\n",

              _base != NULL ? _base->_idx : 0,

              _adr  != NULL ? _adr->_idx  : 0,

              _scale, _offset,

              _negate_invar?'-':'+',

              _invar != NULL ? _invar->_idx : 0);

 #endif

 }

 // ========================= OrderedPair =====================

 const OrderedPair OrderedPair::initial;

 // ========================= SWNodeInfo =====================

 const SWNodeInfo SWNodeInfo::initial;

 // ============================ DepGraph ===========================

 //------------------------------make_node---------------------------

 // Make a new dependence graph node for an ideal node.

 DepMem* DepGraph::make_node(Node* node) {

   DepMem* m = new (_arena) DepMem(node);

   if (node != NULL) {

     assert(_map.at_grow(node->_idx) == NULL, "one init only");

     _map.at_put_grow(node->_idx, m);

   }

   return m;

 }

 //------------------------------make_edge---------------------------

 // Make a new dependence graph edge from dpred -> dsucc

 DepEdge* DepGraph::make_edge(DepMem* dpred, DepMem* dsucc) {

   DepEdge* e = new (_arena) DepEdge(dpred, dsucc, dsucc->in_head(), dpred->out_head());

   dpred->set_out_head(e);

   dsucc->set_in_head(e);

   return e;

 }

 // ========================== DepMem ========================

 //------------------------------in_cnt---------------------------

 int DepMem::in_cnt() {

   int ct = 0;

   for (DepEdge* e = _in_head; e != NULL; e = e->next_in()) ct++;

   return ct;

 }

 //------------------------------out_cnt---------------------------

 int DepMem::out_cnt() {

   int ct = 0;

   for (DepEdge* e = _out_head; e != NULL; e = e->next_out()) ct++;

   return ct;

 }

 //------------------------------print-----------------------------

 void DepMem::print() {

 #ifndef PRODUCT

   tty->print("  DepNode %d (", _node->_idx);

   for (DepEdge* p = _in_head; p != NULL; p = p->next_in()) {

     Node* pred = p->pred()->node();

     tty->print(" %d", pred != NULL ? pred->_idx : 0);

   }

   tty->print(") [");

   for (DepEdge* s = _out_head; s != NULL; s = s->next_out()) {

     Node* succ = s->succ()->node();

     tty->print(" %d", succ != NULL ? succ->_idx : 0);

   }

   tty->print_cr(" ]");

 #endif

 }

 // =========================== DepEdge =========================

 //------------------------------DepPreds---------------------------

 void DepEdge::print() {

 #ifndef PRODUCT

   tty->print_cr("DepEdge: %d [ %d ]", _pred->node()->_idx, _succ->node()->_idx);

 #endif

 }

 // =========================== DepPreds =========================

 // Iterator over predecessor edges in the dependence graph.

 //------------------------------DepPreds---------------------------

 DepPreds::DepPreds(Node* n, DepGraph& dg) {

   _n = n;

   _done = false;

   if (_n->is_Store() || _n->is_Load()) {

     _next_idx = MemNode::Address;

     _end_idx  = n->req();

     _dep_next = dg.dep(_n)->in_head();

   } else if (_n->is_Mem()) {

     _next_idx = 0;

     _end_idx  = 0;

     _dep_next = dg.dep(_n)->in_head();

   } else {

     _next_idx = 1;

     _end_idx  = _n->req();

     _dep_next = NULL;

   }

   next();

 }

 //------------------------------next---------------------------

 void DepPreds::next() {

   if (_dep_next != NULL) {

     _current  = _dep_next->pred()->node();

     _dep_next = _dep_next->next_in();

   } else if (_next_idx < _end_idx) {

     _current  = _n->in(_next_idx++);

   } else {

     _done = true;

   }

 }

 // =========================== DepSuccs =========================

 // Iterator over successor edges in the dependence graph.

 //------------------------------DepSuccs---------------------------

 DepSuccs::DepSuccs(Node* n, DepGraph& dg) {

   _n = n;

   _done = false;

   if (_n->is_Load()) {

     _next_idx = 0;

     _end_idx  = _n->outcnt();

     _dep_next = dg.dep(_n)->out_head();

   } else if (_n->is_Mem() || _n->is_Phi() && _n->bottom_type() == Type::MEMORY) {

     _next_idx = 0;

     _end_idx  = 0;

     _dep_next = dg.dep(_n)->out_head();

   } else {

     _next_idx = 0;

     _end_idx  = _n->outcnt();

     _dep_next = NULL;

   }

   next();

 }

 //-------------------------------next---------------------------

 void DepSuccs::next() {

   if (_dep_next != NULL) {

     _current  = _dep_next->succ()->node();

     _dep_next = _dep_next->next_out();

   } else if (_next_idx < _end_idx) {

     _current  = _n->raw_out(_next_idx++);

   } else {

     _done = true;

   }

 }