reg_split.cpp

/*
 * Copyright (c) 2000, 2012, 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 "libadt/vectset.hpp"
#include "memory/allocation.inline.hpp"
#include "opto/addnode.hpp"
#include "opto/c2compiler.hpp"
#include "opto/callnode.hpp"
#include "opto/cfgnode.hpp"
#include "opto/chaitin.hpp"
#include "opto/loopnode.hpp"
#include "opto/machnode.hpp"

//------------------------------Split--------------------------------------
// Walk the graph in RPO and for each lrg which spills, propagate reaching
// definitions.  During propagation, split the live range around regions of
// High Register Pressure (HRP).  If a Def is in a region of Low Register
// Pressure (LRP), it will not get spilled until we encounter a region of
// HRP between it and one of its uses.  We will spill at the transition
// point between LRP and HRP.  Uses in the HRP region will use the spilled
// Def.  The first Use outside the HRP region will generate a SpillCopy to
// hoist the live range back up into a register, and all subsequent uses
// will use that new Def until another HRP region is encountered.  Defs in
// HRP regions will get trailing SpillCopies to push the LRG down into the
// stack immediately.
//
// As a side effect, unlink from (hence make dead) coalesced copies.
//

static const char out_of_nodes[] = "out of nodes during split";

static bool contains_no_live_range_input(const Node* def) {
  for (uint i = 1; i < def->req(); ++i) {
    if (def->in(i) != NULL && def->in_RegMask(i).is_NotEmpty()) {
      return false;
    }
  }
  return true;
}

//------------------------------get_spillcopy_wide-----------------------------
// Get a SpillCopy node with wide-enough masks.  Use the 'wide-mask', the
// wide ideal-register spill-mask if possible.  If the 'wide-mask' does
// not cover the input (or output), use the input (or output) mask instead.
Node *PhaseChaitin::get_spillcopy_wide( Node *def, Node *use, uint uidx ) {
  // If ideal reg doesn't exist we've got a bad schedule happening
  // that is forcing us to spill something that isn't spillable.
  // Bail rather than abort
  int ireg = def->ideal_reg();
  if( ireg == 0 || ireg == Op_RegFlags ) {
    assert(false, "attempted to spill a non-spillable item");
    C->record_method_not_compilable("attempted to spill a non-spillable item");
    return NULL;
  }
  if (C->check_node_count(NodeLimitFudgeFactor, out_of_nodes)) {
    return NULL;
  }
  const RegMask *i_mask = &def->out_RegMask();
  const RegMask *w_mask = C->matcher()->idealreg2spillmask[ireg];
  const RegMask *o_mask = use ? &use->in_RegMask(uidx) : w_mask;
  const RegMask *w_i_mask = w_mask->overlap( *i_mask ) ? w_mask : i_mask;
  const RegMask *w_o_mask;

  int num_regs = RegMask::num_registers(ireg);
  bool is_vect = RegMask::is_vector(ireg);
  if( w_mask->overlap( *o_mask ) && // Overlap AND
      ((num_regs == 1) // Single use or aligned
        ||  is_vect    // or vector
        || !is_vect && o_mask->is_aligned_pairs()) ) {
    assert(!is_vect || o_mask->is_aligned_sets(num_regs), "vectors are aligned");
    // Don't come here for mis-aligned doubles
    w_o_mask = w_mask;
  } else {                      // wide ideal mask does not overlap with o_mask
    // Mis-aligned doubles come here and XMM->FPR moves on x86.
    w_o_mask = o_mask;          // Must target desired registers
    // Does the ideal-reg-mask overlap with o_mask?  I.e., can I use
    // a reg-reg move or do I need a trip across register classes
    // (and thus through memory)?
    if( !C->matcher()->idealreg2regmask[ireg]->overlap( *o_mask) && o_mask->is_UP() )
      // Here we assume a trip through memory is required.
      w_i_mask = &C->FIRST_STACK_mask();
  }
  return new (C) MachSpillCopyNode( def, *w_i_mask, *w_o_mask );
}

//------------------------------insert_proj------------------------------------
// Insert the spill at chosen location.  Skip over any intervening Proj's or
// Phis.  Skip over a CatchNode and projs, inserting in the fall-through block
// instead.  Update high-pressure indices.  Create a new live range.
void PhaseChaitin::insert_proj( Block *b, uint i, Node *spill, uint maxlrg ) {
  // Skip intervening ProjNodes.  Do not insert between a ProjNode and
  // its definer.
  while( i < b->number_of_nodes() &&
         (b->get_node(i)->is_Proj() ||
          b->get_node(i)->is_Phi() ) )
    i++;

  // Do not insert between a call and his Catch
  if( b->get_node(i)->is_Catch() ) {
    // Put the instruction at the top of the fall-thru block.
    // Find the fall-thru projection
    while( 1 ) {
      const CatchProjNode *cp = b->get_node(++i)->as_CatchProj();
      if( cp->_con == CatchProjNode::fall_through_index )
        break;
    }
    int sidx = i - b->end_idx()-1;
    b = b->_succs[sidx];        // Switch to successor block
    i = 1;                      // Right at start of block
  }

  b->insert_node(spill, i);    // Insert node in block
  _cfg.map_node_to_block(spill,  b); // Update node->block mapping to reflect
  // Adjust the point where we go hi-pressure
  if( i <= b->_ihrp_index ) b->_ihrp_index++;
  if( i <= b->_fhrp_index ) b->_fhrp_index++;

  // Assign a new Live Range Number to the SpillCopy and grow
  // the node->live range mapping.
  new_lrg(spill,maxlrg);
}

//------------------------------split_DEF--------------------------------------
// There are four categories of Split; UP/DOWN x DEF/USE
// Only three of these really occur as DOWN/USE will always color
// Any Split with a DEF cannot CISC-Spill now.  Thus we need
// two helper routines, one for Split DEFS (insert after instruction),
// one for Split USES (insert before instruction).  DEF insertion
// happens inside Split, where the Leaveblock array is updated.
uint PhaseChaitin::split_DEF( Node *def, Block *b, int loc, uint maxlrg, Node **Reachblock, Node **debug_defs, GrowableArray<uint> splits, int slidx ) {
#ifdef ASSERT
  // Increment the counter for this lrg
  splits.at_put(slidx, splits.at(slidx)+1);
#endif
  // If we are spilling the memory op for an implicit null check, at the
  // null check location (ie - null check is in HRP block) we need to do
  // the null-check first, then spill-down in the following block.
  // (The implicit_null_check function ensures the use is also dominated
  // by the branch-not-taken block.)
  Node *be = b->end();
  if( be->is_MachNullCheck() && be->in(1) == def && def == b->get_node(loc)) {
    // Spill goes in the branch-not-taken block
    b = b->_succs[b->get_node(b->end_idx()+1)->Opcode() == Op_IfTrue];
    loc = 0;                    // Just past the Region
  }
  assert( loc >= 0, "must insert past block head" );

  // Get a def-side SpillCopy
  Node *spill = get_spillcopy_wide(def,NULL,0);
  // Did we fail to split?, then bail
  if (!spill) {
    return 0;
  }

  // Insert the spill at chosen location
  insert_proj( b, loc+1, spill, maxlrg++);

  // Insert new node into Reaches array
  Reachblock[slidx] = spill;
  // Update debug list of reaching down definitions by adding this one
  debug_defs[slidx] = spill;

  // return updated count of live ranges
  return maxlrg;
}

//------------------------------split_USE--------------------------------------
// Splits at uses can involve redeffing the LRG, so no CISC Spilling there.
// Debug uses want to know if def is already stack enabled.
uint PhaseChaitin::split_USE( Node *def, Block *b, Node *use, uint useidx, uint maxlrg, bool def_down, bool cisc_sp, GrowableArray<uint> splits, int slidx ) {
#ifdef ASSERT
  // Increment the counter for this lrg
  splits.at_put(slidx, splits.at(slidx)+1);
#endif

  // Some setup stuff for handling debug node uses
  JVMState* jvms = use->jvms();
  uint debug_start = jvms ? jvms->debug_start() : 999999;
  uint debug_end   = jvms ? jvms->debug_end()   : 999999;

  //-------------------------------------------
  // Check for use of debug info
  if (useidx >= debug_start && useidx < debug_end) {
    // Actually it's perfectly legal for constant debug info to appear
    // just unlikely.  In this case the optimizer left a ConI of a 4
    // as both inputs to a Phi with only a debug use.  It's a single-def
    // live range of a rematerializable value.  The live range spills,
    // rematerializes and now the ConI directly feeds into the debug info.
    // assert(!def->is_Con(), "constant debug info already constructed directly");

    // Special split handling for Debug Info
    // If DEF is DOWN, just hook the edge and return
    // If DEF is UP, Split it DOWN for this USE.
    if( def->is_Mach() ) {
      if( def_down ) {
        // DEF is DOWN, so connect USE directly to the DEF
        use->set_req(useidx, def);
      } else {
        // Block and index where the use occurs.
        Block *b = _cfg.get_block_for_node(use);
        // Put the clone just prior to use
        int bindex = b->find_node(use);
        // DEF is UP, so must copy it DOWN and hook in USE
        // Insert SpillCopy before the USE, which uses DEF as its input,
        // and defs a new live range, which is used by this node.
        Node *spill = get_spillcopy_wide(def,use,useidx);
        // did we fail to split?
        if (!spill) {
          // Bail
          return 0;
        }
        // insert into basic block
        insert_proj( b, bindex, spill, maxlrg++ );
        // Use the new split
        use->set_req(useidx,spill);
      }
      // No further split handling needed for this use
      return maxlrg;
    }  // End special splitting for debug info live range
  }  // If debug info

  // CISC-SPILLING
  // Finally, check to see if USE is CISC-Spillable, and if so,
  // gather_lrg_masks will add the flags bit to its mask, and
  // no use side copy is needed.  This frees up the live range
  // register choices without causing copy coalescing, etc.
  if( UseCISCSpill && cisc_sp ) {
    int inp = use->cisc_operand();
    if( inp != AdlcVMDeps::Not_cisc_spillable )
      // Convert operand number to edge index number
      inp = use->as_Mach()->operand_index(inp);
    if( inp == (int)useidx ) {
      use->set_req(useidx, def);
#ifndef PRODUCT
      if( TraceCISCSpill ) {
        tty->print("  set_split: ");
        use->dump();
      }
#endif
      return maxlrg;
    }
  }

  //-------------------------------------------
  // Insert a Copy before the use

  // Block and index where the use occurs.
  int bindex;
  // Phi input spill-copys belong at the end of the prior block
  if( use->is_Phi() ) {
    b = _cfg.get_block_for_node(b->pred(useidx));
    bindex = b->end_idx();
  } else {
    // Put the clone just prior to use
    bindex = b->find_node(use);
  }

  Node *spill = get_spillcopy_wide( def, use, useidx );
  if( !spill ) return 0;        // Bailed out
  // Insert SpillCopy before the USE, which uses the reaching DEF as
  // its input, and defs a new live range, which is used by this node.
  insert_proj( b, bindex, spill, maxlrg++ );
  // Use the spill/clone
  use->set_req(useidx,spill);

  // return updated live range count
  return maxlrg;
}

//------------------------------clone_node----------------------------
// Clone node with anti dependence check.
Node* clone_node(Node* def, Block *b, Compile* C) {
  if (def->needs_anti_dependence_check()) {
#ifdef ASSERT
    if (Verbose) {
      tty->print_cr("RA attempts to clone node with anti_dependence:");
      def->dump(-1); tty->cr();
      tty->print_cr("into block:");
      b->dump();
    }
#endif
    if (C->subsume_loads() == true && !C->failing()) {
      // Retry with subsume_loads == false
      // If this is the first failure, the sentinel string will "stick"
      // to the Compile object, and the C2Compiler will see it and retry.
      C->record_failure(C2Compiler::retry_no_subsuming_loads());
    } else {
      // Bailout without retry
      C->record_method_not_compilable("RA Split failed: attempt to clone node with anti_dependence");
    }
    return 0;
  }
  return def->clone();
}

//------------------------------split_Rematerialize----------------------------
// Clone a local copy of the def.
Node *PhaseChaitin::split_Rematerialize( Node *def, Block *b, uint insidx, uint &maxlrg, GrowableArray<uint> splits, int slidx, uint *lrg2reach, Node **Reachblock, bool walkThru ) {
  // The input live ranges will be stretched to the site of the new
  // instruction.  They might be stretched past a def and will thus
  // have the old and new values of the same live range alive at the
  // same time - a definite no-no.  Split out private copies of
  // the inputs.
  if( def->req() > 1 ) {
    for( uint i = 1; i < def->req(); i++ ) {
      Node *in = def->in(i);
      // Check for single-def (LRG cannot redefined)
      uint lidx = _lrg_map.live_range_id(in);
      if (lidx >= _lrg_map.max_lrg_id()) {
        continue; // Value is a recent spill-copy
      }
      if (lrgs(lidx).is_singledef()) {
        continue;
      }

      Block *b_def = _cfg.get_block_for_node(def);
      int idx_def = b_def->find_node(def);
      Node *in_spill = get_spillcopy_wide( in, def, i );
      if( !in_spill ) return 0; // Bailed out
      insert_proj(b_def,idx_def,in_spill,maxlrg++);
      if( b_def == b )
        insidx++;
      def->set_req(i,in_spill);
    }
  }

  Node *spill = clone_node(def, b, C);
  if (spill == NULL || C->check_node_count(NodeLimitFudgeFactor, out_of_nodes)) {
    // Check when generating nodes
    return 0;
  }

  // See if any inputs are currently being spilled, and take the
  // latest copy of spilled inputs.
  if( spill->req() > 1 ) {
    for( uint i = 1; i < spill->req(); i++ ) {
      Node *in = spill->in(i);
      uint lidx = _lrg_map.find_id(in);

      // Walk backwards thru spill copy node intermediates
      if (walkThru) {
        while (in->is_SpillCopy() && lidx >= _lrg_map.max_lrg_id()) {
          in = in->in(1);
          lidx = _lrg_map.find_id(in);
        }

        if (lidx < _lrg_map.max_lrg_id() && lrgs(lidx).is_multidef()) {
          // walkThru found a multidef LRG, which is unsafe to use, so
          // just keep the original def used in the clone.
          in = spill->in(i);
          lidx = _lrg_map.find_id(in);
        }
      }

      if (lidx < _lrg_map.max_lrg_id() && lrgs(lidx).reg() >= LRG::SPILL_REG) {
        assert(Reachblock != NULL, "Reachblock must be non-NULL");
        Node *rdef = Reachblock[lrg2reach[lidx]];
        if (rdef) {
          spill->set_req(i, rdef);
        }
      }
    }
  }


  assert( spill->out_RegMask().is_UP(), "rematerialize to a reg" );
  // Rematerialized op is def->spilled+1
  set_was_spilled(spill);
  if( _spilled_once.test(def->_idx) )
    set_was_spilled(spill);

  insert_proj( b, insidx, spill, maxlrg++ );
#ifdef ASSERT
  // Increment the counter for this lrg
  splits.at_put(slidx, splits.at(slidx)+1);
#endif
  // See if the cloned def kills any flags, and copy those kills as well
  uint i = insidx+1;
  int found_projs = clone_projs( b, i, def, spill, maxlrg);
  if (found_projs > 0) {
    // Adjust the point where we go hi-pressure
    if (i <= b->_ihrp_index) {
      b->_ihrp_index += found_projs;
    }
    if (i <= b->_fhrp_index) {
      b->_fhrp_index += found_projs;
    }
  }

  return spill;
}

//------------------------------is_high_pressure-------------------------------
// Function to compute whether or not this live range is "high pressure"
// in this block - whether it spills eagerly or not.
bool PhaseChaitin::is_high_pressure( Block *b, LRG *lrg, uint insidx ) {
  if( lrg->_was_spilled1 ) return true;
  // Forced spilling due to conflict?  Then split only at binding uses
  // or defs, not for supposed capacity problems.
  // CNC - Turned off 7/8/99, causes too much spilling
  // if( lrg->_is_bound ) return false;

  // Use float pressure numbers for vectors.
  bool is_float_or_vector = lrg->_is_float || lrg->_is_vector;
  // Not yet reached the high-pressure cutoff point, so low pressure
  uint hrp_idx = is_float_or_vector ? b->_fhrp_index : b->_ihrp_index;
  if( insidx < hrp_idx ) return false;
  // Register pressure for the block as a whole depends on reg class
  int block_pres = is_float_or_vector ? b->_freg_pressure : b->_reg_pressure;
  // Bound live ranges will split at the binding points first;
  // Intermediate splits should assume the live range's register set
  // got "freed up" and that num_regs will become INT_PRESSURE.
  int bound_pres = is_float_or_vector ? FLOATPRESSURE : INTPRESSURE;
  // Effective register pressure limit.
  int lrg_pres = (lrg->get_invalid_mask_size() > lrg->num_regs())
    ? (lrg->get_invalid_mask_size() >> (lrg->num_regs()-1)) : bound_pres;
  // High pressure if block pressure requires more register freedom
  // than live range has.
  return block_pres >= lrg_pres;
}


//------------------------------prompt_use---------------------------------
// True if lidx is used before any real register is def'd in the block
bool PhaseChaitin::prompt_use( Block *b, uint lidx ) {
  if (lrgs(lidx)._was_spilled2) {
    return false;
  }

  // Scan block for 1st use.
  for( uint i = 1; i <= b->end_idx(); i++ ) {
    Node *n = b->get_node(i);
    // Ignore PHI use, these can be up or down
    if (n->is_Phi()) {
      continue;
    }
    for (uint j = 1; j < n->req(); j++) {
      if (_lrg_map.find_id(n->in(j)) == lidx) {
        return true;          // Found 1st use!
      }
    }
    if (n->out_RegMask().is_NotEmpty()) {
      return false;
    }
  }
  return false;
}

//------------------------------Split--------------------------------------
//----------Split Routine----------
// ***** NEW SPLITTING HEURISTIC *****
// DEFS: If the DEF is in a High Register Pressure(HRP) Block, split there.
//        Else, no split unless there is a HRP block between a DEF and
//        one of its uses, and then split at the HRP block.
//
// USES: If USE is in HRP, split at use to leave main LRG on stack.
//       Else, hoist LRG back up to register only (ie - split is also DEF)
// We will compute a new maxlrg as we go
uint PhaseChaitin::Split(uint maxlrg, ResourceArea* split_arena) {
  NOT_PRODUCT( Compile::TracePhase t3("regAllocSplit", &_t_regAllocSplit, TimeCompiler); )

  // Free thread local resources used by this method on exit.
  ResourceMark rm(split_arena);

  uint                 bidx, pidx, slidx, insidx, inpidx, twoidx;
  uint                 non_phi = 1, spill_cnt = 0;
  Node               **Reachblock;
  Node                *n1, *n2, *n3;
  Node_List           *defs,*phis;
  bool                *UPblock;
  bool                 u1, u2, u3;
  Block               *b, *pred;
  PhiNode             *phi;
  GrowableArray<uint>  lidxs(split_arena, maxlrg, 0, 0);

  // Array of counters to count splits per live range
  GrowableArray<uint>  splits(split_arena, maxlrg, 0, 0);

#define NEW_SPLIT_ARRAY(type, size)\
  (type*) split_arena->allocate_bytes((size) * sizeof(type))

  //----------Setup Code----------
  // Create a convenient mapping from lrg numbers to reaches/leaves indices
  uint *lrg2reach = NEW_SPLIT_ARRAY(uint, maxlrg);
  // Keep track of DEFS & Phis for later passes
  defs = new Node_List();
  phis = new Node_List();
  // Gather info on which LRG's are spilling, and build maps
  for (bidx = 1; bidx < maxlrg; bidx++) {
    if (lrgs(bidx).alive() && lrgs(bidx).reg() >= LRG::SPILL_REG) {
      assert(!lrgs(bidx).mask().is_AllStack(),"AllStack should color");
      lrg2reach[bidx] = spill_cnt;
      spill_cnt++;
      lidxs.append(bidx);
#ifdef ASSERT
      // Initialize the split counts to zero
      splits.append(0);
#endif
#ifndef PRODUCT
      if( PrintOpto && WizardMode && lrgs(bidx)._was_spilled1 )
        tty->print_cr("Warning, 2nd spill of L%d",bidx);
#endif
    }
  }

  // Create side arrays for propagating reaching defs info.
  // Each block needs a node pointer for each spilling live range for the
  // Def which is live into the block.  Phi nodes handle multiple input
  // Defs by querying the output of their predecessor blocks and resolving
  // them to a single Def at the phi.  The pointer is updated for each
  // Def in the block, and then becomes the output for the block when
  // processing of the block is complete.  We also need to track whether
  // a Def is UP or DOWN.  UP means that it should get a register (ie -
  // it is always in LRP regions), and DOWN means that it is probably
  // on the stack (ie - it crosses HRP regions).
  Node ***Reaches     = NEW_SPLIT_ARRAY( Node**, _cfg.number_of_blocks() + 1);
  bool  **UP          = NEW_SPLIT_ARRAY( bool*, _cfg.number_of_blocks() + 1);
  Node  **debug_defs  = NEW_SPLIT_ARRAY( Node*, spill_cnt );
  VectorSet **UP_entry= NEW_SPLIT_ARRAY( VectorSet*, spill_cnt );

  // Initialize Reaches & UP
  for (bidx = 0; bidx < _cfg.number_of_blocks() + 1; bidx++) {
    Reaches[bidx]     = NEW_SPLIT_ARRAY( Node*, spill_cnt );
    UP[bidx]          = NEW_SPLIT_ARRAY( bool, spill_cnt );
    Node **Reachblock = Reaches[bidx];
    bool *UPblock     = UP[bidx];
    for( slidx = 0; slidx < spill_cnt; slidx++ ) {
      UPblock[slidx] = true;     // Assume they start in registers
      Reachblock[slidx] = NULL;  // Assume that no def is present
    }
  }

#undef NEW_SPLIT_ARRAY

  // Initialize to array of empty vectorsets
  for( slidx = 0; slidx < spill_cnt; slidx++ )
    UP_entry[slidx] = new VectorSet(split_arena);

  //----------PASS 1----------
  //----------Propagation & Node Insertion Code----------
  // Walk the Blocks in RPO for DEF & USE info
  for( bidx = 0; bidx < _cfg.number_of_blocks(); bidx++ ) {

    if (C->check_node_count(spill_cnt, out_of_nodes)) {
      return 0;
    }

    b  = _cfg.get_block(bidx);
    // Reaches & UP arrays for this block
    Reachblock = Reaches[b->_pre_order];
    UPblock    = UP[b->_pre_order];
    // Reset counter of start of non-Phi nodes in block
    non_phi = 1;
    //----------Block Entry Handling----------
    // Check for need to insert a new phi
    // Cycle through this block's predecessors, collecting Reaches
    // info for each spilled LRG.  If they are identical, no phi is
    // needed.  If they differ, check for a phi, and insert if missing,
    // or update edges if present.  Set current block's Reaches set to
    // be either the phi's or the reaching def, as appropriate.
    // If no Phi is needed, check if the LRG needs to spill on entry
    // to the block due to HRP.
    for( slidx = 0; slidx < spill_cnt; slidx++ ) {
      // Grab the live range number
      uint lidx = lidxs.at(slidx);
      // Do not bother splitting or putting in Phis for single-def
      // rematerialized live ranges.  This happens alot to constants
      // with long live ranges.
      if( lrgs(lidx).is_singledef() &&
          lrgs(lidx)._def->rematerialize() ) {
        // reset the Reaches & UP entries
        Reachblock[slidx] = lrgs(lidx)._def;
        UPblock[slidx] = true;
        // Record following instruction in case 'n' rematerializes and
        // kills flags
        Block *pred1 = _cfg.get_block_for_node(b->pred(1));
        continue;
      }

      // Initialize needs_phi and needs_split
      bool needs_phi = false;
      bool needs_split = false;
      bool has_phi = false;
      // Walk the predecessor blocks to check inputs for that live range
      // Grab predecessor block header
      n1 = b->pred(1);
      // Grab the appropriate reaching def info for inpidx
      pred = _cfg.get_block_for_node(n1);
      pidx = pred->_pre_order;
      Node **Ltmp = Reaches[pidx];
      bool  *Utmp = UP[pidx];
      n1 = Ltmp[slidx];
      u1 = Utmp[slidx];
      // Initialize node for saving type info
      n3 = n1;
      u3 = u1;

      // Compare inputs to see if a Phi is needed
      for( inpidx = 2; inpidx < b->num_preds(); inpidx++ ) {
        // Grab predecessor block headers
        n2 = b->pred(inpidx);
        // Grab the appropriate reaching def info for inpidx
        pred = _cfg.get_block_for_node(n2);
        pidx = pred->_pre_order;
        Ltmp = Reaches[pidx];
        Utmp = UP[pidx];
        n2 = Ltmp[slidx];
        u2 = Utmp[slidx];
        // For each LRG, decide if a phi is necessary
        if( n1 != n2 ) {
          needs_phi = true;
        }
        // See if the phi has mismatched inputs, UP vs. DOWN
        if( n1 && n2 && (u1 != u2) ) {
          needs_split = true;
        }
        // Move n2/u2 to n1/u1 for next iteration
        n1 = n2;
        u1 = u2;
        // Preserve a non-NULL predecessor for later type referencing
        if( (n3 == NULL) && (n2 != NULL) ){
          n3 = n2;
          u3 = u2;
        }
      }  // End for all potential Phi inputs

      // check block for appropriate phinode & update edges
      for( insidx = 1; insidx <= b->end_idx(); insidx++ ) {
        n1 = b->get_node(insidx);
        // bail if this is not a phi
        phi = n1->is_Phi() ? n1->as_Phi() : NULL;
        if( phi == NULL ) {
          // Keep track of index of first non-PhiNode instruction in block
          non_phi = insidx;
          // break out of the for loop as we have handled all phi nodes
          break;
        }
        // must be looking at a phi
        if (_lrg_map.find_id(n1) == lidxs.at(slidx)) {
          // found the necessary phi
          needs_phi = false;
          has_phi = true;
          // initialize the Reaches entry for this LRG
          Reachblock[slidx] = phi;
          break;
        }  // end if found correct phi
      }  // end for all phi's

      // If a phi is needed or exist, check for it
      if( needs_phi || has_phi ) {
        // add new phinode if one not already found
        if( needs_phi ) {
          // create a new phi node and insert it into the block
          // type is taken from left over pointer to a predecessor
          assert(n3,"No non-NULL reaching DEF for a Phi");
          phi = new (C) PhiNode(b->head(), n3->bottom_type());
          // initialize the Reaches entry for this LRG
          Reachblock[slidx] = phi;

          // add node to block & node_to_block mapping
          insert_proj(b, insidx++, phi, maxlrg++);
          non_phi++;
          // Reset new phi's mapping to be the spilling live range
          _lrg_map.map(phi->_idx, lidx);
          assert(_lrg_map.find_id(phi) == lidx, "Bad update on Union-Find mapping");
        }  // end if not found correct phi
        // Here you have either found or created the Phi, so record it
        assert(phi != NULL,"Must have a Phi Node here");
        phis->push(phi);
        // PhiNodes should either force the LRG UP or DOWN depending
        // on its inputs and the register pressure in the Phi's block.
        UPblock[slidx] = true;  // Assume new DEF is UP
        // If entering a high-pressure area with no immediate use,
        // assume Phi is DOWN
        if( is_high_pressure( b, &lrgs(lidx), b->end_idx()) && !prompt_use(b,lidx) )
          UPblock[slidx] = false;
        // If we are not split up/down and all inputs are down, then we
        // are down
        if( !needs_split && !u3 )
          UPblock[slidx] = false;
      }  // end if phi is needed

      // Do not need a phi, so grab the reaching DEF
      else {
        // Grab predecessor block header
        n1 = b->pred(1);
        // Grab the appropriate reaching def info for k
        pred = _cfg.get_block_for_node(n1);
        pidx = pred->_pre_order;
        Node **Ltmp = Reaches[pidx];
        bool  *Utmp = UP[pidx];
        // reset the Reaches & UP entries
        Reachblock[slidx] = Ltmp[slidx];
        UPblock[slidx] = Utmp[slidx];
      }  // end else no Phi is needed
    }  // end for all spilling live ranges
    // DEBUG
#ifndef PRODUCT
    if(trace_spilling()) {
      tty->print("/`\nBlock %d: ", b->_pre_order);
      tty->print("Reaching Definitions after Phi handling\n");
      for( uint x = 0; x < spill_cnt; x++ ) {
        tty->print("Spill Idx %d: UP %d: Node\n",x,UPblock[x]);
        if( Reachblock[x] )
          Reachblock[x]->dump();
        else
          tty->print("Undefined\n");
      }
    }
#endif

    //----------Non-Phi Node Splitting----------
    // Since phi-nodes have now been handled, the Reachblock array for this
    // block is initialized with the correct starting value for the defs which
    // reach non-phi instructions in this block.  Thus, process non-phi
    // instructions normally, inserting SpillCopy nodes for all spill
    // locations.

    // Memoize any DOWN reaching definitions for use as DEBUG info
    for( insidx = 0; insidx < spill_cnt; insidx++ ) {
      debug_defs[insidx] = (UPblock[insidx]) ? NULL : Reachblock[insidx];
      if( UPblock[insidx] )     // Memoize UP decision at block start
        UP_entry[insidx]->set( b->_pre_order );
    }

    //----------Walk Instructions in the Block and Split----------
    // For all non-phi instructions in the block
    for( insidx = 1; insidx <= b->end_idx(); insidx++ ) {
      Node *n = b->get_node(insidx);
      // Find the defining Node's live range index
      uint defidx = _lrg_map.find_id(n);
      uint cnt = n->req();

      if (n->is_Phi()) {
        // Skip phi nodes after removing dead copies.
        if (defidx < _lrg_map.max_lrg_id()) {
          // Check for useless Phis.  These appear if we spill, then
          // coalesce away copies.  Dont touch Phis in spilling live
          // ranges; they are busy getting modifed in this pass.
          if( lrgs(defidx).reg() < LRG::SPILL_REG ) {
            uint i;
            Node *u = NULL;
            // Look for the Phi merging 2 unique inputs
            for( i = 1; i < cnt; i++ ) {
              // Ignore repeats and self
              if( n->in(i) != u && n->in(i) != n ) {
                // Found a unique input
                if( u != NULL ) // If it's the 2nd, bail out
                  break;
                u = n->in(i);   // Else record it
              }
            }
            assert( u, "at least 1 valid input expected" );
            if (i >= cnt) {    // Found one unique input
              assert(_lrg_map.find_id(n) == _lrg_map.find_id(u), "should be the same lrg");
              n->replace_by(u); // Then replace with unique input
              n->disconnect_inputs(NULL, C);
              b->remove_node(insidx);
              insidx--;
              b->_ihrp_index--;
              b->_fhrp_index--;
            }
          }
        }
        continue;
      }
      assert( insidx > b->_ihrp_index ||
              (b->_reg_pressure < (uint)INTPRESSURE) ||
              b->_ihrp_index > 4000000 ||
              b->_ihrp_index >= b->end_idx() ||
              !b->get_node(b->_ihrp_index)->is_Proj(), "" );
      assert( insidx > b->_fhrp_index ||
              (b->_freg_pressure < (uint)FLOATPRESSURE) ||
              b->_fhrp_index > 4000000 ||
              b->_fhrp_index >= b->end_idx() ||
              !b->get_node(b->_fhrp_index)->is_Proj(), "" );

      // ********** Handle Crossing HRP Boundry **********
      if( (insidx == b->_ihrp_index) || (insidx == b->_fhrp_index) ) {
        for( slidx = 0; slidx < spill_cnt; slidx++ ) {
          // Check for need to split at HRP boundary - split if UP
          n1 = Reachblock[slidx];
          // bail out if no reaching DEF
          if( n1 == NULL ) continue;
          // bail out if live range is 'isolated' around inner loop
          uint lidx = lidxs.at(slidx);
          // If live range is currently UP
          if( UPblock[slidx] ) {
            // set location to insert spills at
            // SPLIT DOWN HERE - NO CISC SPILL
            if( is_high_pressure( b, &lrgs(lidx), insidx ) &&
                !n1->rematerialize() ) {
              // If there is already a valid stack definition available, use it
              if( debug_defs[slidx] != NULL ) {
                Reachblock[slidx] = debug_defs[slidx];
              }
              else {
                // Insert point is just past last use or def in the block
                int insert_point = insidx-1;
                while( insert_point > 0 ) {
                  Node *n = b->get_node(insert_point);
                  // Hit top of block?  Quit going backwards
                  if (n->is_Phi()) {
                    break;
                  }
                  // Found a def?  Better split after it.
                  if (_lrg_map.live_range_id(n) == lidx) {
                    break;
                  }
                  // Look for a use
                  uint i;
                  for( i = 1; i < n->req(); i++ ) {
                    if (_lrg_map.live_range_id(n->in(i)) == lidx) {
                      break;
                    }
                  }
                  // Found a use?  Better split after it.
                  if (i < n->req()) {
                    break;
                  }
                  insert_point--;
                }
                uint orig_eidx = b->end_idx();
                maxlrg = split_DEF( n1, b, insert_point, maxlrg, Reachblock, debug_defs, splits, slidx);
                // If it wasn't split bail
                if (!maxlrg) {
                  return 0;
                }
                // Spill of NULL check mem op goes into the following block.
                if (b->end_idx() > orig_eidx) {
                  insidx++;
                }
              }
              // This is a new DEF, so update UP
              UPblock[slidx] = false;
#ifndef PRODUCT
              // DEBUG
              if( trace_spilling() ) {
                tty->print("\nNew Split DOWN DEF of Spill Idx ");
                tty->print("%d, UP %d:\n",slidx,false);
                n1->dump();
              }
#endif
            }
          }  // end if LRG is UP
        }  // end for all spilling live ranges
        assert( b->get_node(insidx) == n, "got insidx set incorrectly" );
      }  // end if crossing HRP Boundry

      // If the LRG index is oob, then this is a new spillcopy, skip it.
      if (defidx >= _lrg_map.max_lrg_id()) {
        continue;
      }
      LRG &deflrg = lrgs(defidx);
      uint copyidx = n->is_Copy();
      // Remove coalesced copy from CFG
      if (copyidx && defidx == _lrg_map.live_range_id(n->in(copyidx))) {
        n->replace_by( n->in(copyidx) );
        n->set_req( copyidx, NULL );
        b->remove_node(insidx--);
        b->_ihrp_index--; // Adjust the point where we go hi-pressure
        b->_fhrp_index--;
        continue;
      }

#define DERIVED 0

      // ********** Handle USES **********
      bool nullcheck = false;
      // Implicit null checks never use the spilled value
      if( n->is_MachNullCheck() )
        nullcheck = true;
      if( !nullcheck ) {
        // Search all inputs for a Spill-USE
        JVMState* jvms = n->jvms();
        uint oopoff = jvms ? jvms->oopoff() : cnt;
        uint old_last = cnt - 1;
        for( inpidx = 1; inpidx < cnt; inpidx++ ) {
          // Derived/base pairs may be added to our inputs during this loop.
          // If inpidx > old_last, then one of these new inputs is being
          // handled. Skip the derived part of the pair, but process
          // the base like any other input.
          if (inpidx > old_last && ((inpidx - oopoff) & 1) == DERIVED) {
            continue;  // skip derived_debug added below
          }
          // Get lidx of input
          uint useidx = _lrg_map.find_id(n->in(inpidx));
          // Not a brand-new split, and it is a spill use
          if (useidx < _lrg_map.max_lrg_id() && lrgs(useidx).reg() >= LRG::SPILL_REG) {
            // Check for valid reaching DEF
            slidx = lrg2reach[useidx];
            Node *def = Reachblock[slidx];
            assert( def != NULL, "Using Undefined Value in Split()\n");

            // (+++) %%%% remove this in favor of pre-pass in matcher.cpp
            // monitor references do not care where they live, so just hook
            if ( jvms && jvms->is_monitor_use(inpidx) ) {
              // The effect of this clone is to drop the node out of the block,
              // so that the allocator does not see it anymore, and therefore
              // does not attempt to assign it a register.
              def = clone_node(def, b, C);
              if (def == NULL || C->check_node_count(NodeLimitFudgeFactor, out_of_nodes)) {
                return 0;
              }
              _lrg_map.extend(def->_idx, 0);
              _cfg.map_node_to_block(def, b);
              n->set_req(inpidx, def);
              continue;
            }

            // Rematerializable?  Then clone def at use site instead
            // of store/load
            if( def->rematerialize() ) {
              int old_size = b->number_of_nodes();
              def = split_Rematerialize( def, b, insidx, maxlrg, splits, slidx, lrg2reach, Reachblock, true );
              if( !def ) return 0; // Bail out
              insidx += b->number_of_nodes()-old_size;
            }

            MachNode *mach = n->is_Mach() ? n->as_Mach() : NULL;
            // Base pointers and oopmap references do not care where they live.
            if ((inpidx >= oopoff) ||
                (mach && mach->ideal_Opcode() == Op_AddP && inpidx == AddPNode::Base)) {
              if (def->rematerialize() && lrgs(useidx)._was_spilled2) {
                // This def has been rematerialized a couple of times without
                // progress. It doesn't care if it lives UP or DOWN, so
                // spill it down now.
                maxlrg = split_USE(def,b,n,inpidx,maxlrg,false,false,splits,slidx);
                // If it wasn't split bail
                if (!maxlrg) {
                  return 0;
                }
                insidx++;  // Reset iterator to skip USE side split
              } else {
                // Just hook the def edge
                n->set_req(inpidx, def);
              }

              if (inpidx >= oopoff) {
                // After oopoff, we have derived/base pairs.  We must mention all
                // derived pointers here as derived/base pairs for GC.  If the
                // derived value is spilling and we have a copy both in Reachblock
                // (called here 'def') and debug_defs[slidx] we need to mention
                // both in derived/base pairs or kill one.
                Node *derived_debug = debug_defs[slidx];
                if( ((inpidx - oopoff) & 1) == DERIVED && // derived vs base?
                    mach && mach->ideal_Opcode() != Op_Halt &&
                    derived_debug != NULL &&
                    derived_debug != def ) { // Actual 2nd value appears
                  // We have already set 'def' as a derived value.
                  // Also set debug_defs[slidx] as a derived value.
                  uint k;
                  for( k = oopoff; k < cnt; k += 2 )
                    if( n->in(k) == derived_debug )
                      break;      // Found an instance of debug derived
                  if( k == cnt ) {// No instance of debug_defs[slidx]
                    // Add a derived/base pair to cover the debug info.
                    // We have to process the added base later since it is not
                    // handled yet at this point but skip derived part.
                    assert(((n->req() - oopoff) & 1) == DERIVED,
                           "must match skip condition above");
                    n->add_req( derived_debug );   // this will be skipped above
                    n->add_req( n->in(inpidx+1) ); // this will be processed
                    // Increment cnt to handle added input edges on
                    // subsequent iterations.
                    cnt += 2;
                  }
                }
              }
              continue;
            }
            // Special logic for DEBUG info
            if( jvms && b->_freq > BLOCK_FREQUENCY(0.5) ) {
              uint debug_start = jvms->debug_start();
              // If this is debug info use & there is a reaching DOWN def
              if ((debug_start <= inpidx) && (debug_defs[slidx] != NULL)) {
                assert(inpidx < oopoff, "handle only debug info here");
                // Just hook it in & move on
                n->set_req(inpidx, debug_defs[slidx]);
                // (Note that this can make two sides of a split live at the
                // same time: The debug def on stack, and another def in a
                // register.  The GC needs to know about both of them, but any
                // derived pointers after oopoff will refer to only one of the
                // two defs and the GC would therefore miss the other.  Thus
                // this hack is only allowed for debug info which is Java state
                // and therefore never a derived pointer.)
                continue;
              }
            }
            // Grab register mask info
            const RegMask &dmask = def->out_RegMask();
            const RegMask &umask = n->in_RegMask(inpidx);
            bool is_vect = RegMask::is_vector(def->ideal_reg());
            assert(inpidx < oopoff, "cannot use-split oop map info");

            bool dup = UPblock[slidx];
            bool uup = umask.is_UP();

            // Need special logic to handle bound USES. Insert a split at this
            // bound use if we can't rematerialize the def, or if we need the
            // split to form a misaligned pair.
            if( !umask.is_AllStack() &&
                (int)umask.Size() <= lrgs(useidx).num_regs() &&
                (!def->rematerialize() ||
                 !is_vect && umask.is_misaligned_pair())) {
              // These need a Split regardless of overlap or pressure
              // SPLIT - NO DEF - NO CISC SPILL
              maxlrg = split_USE(def,b,n,inpidx,maxlrg,dup,false, splits,slidx);
              // If it wasn't split bail
              if (!maxlrg) {
                return 0;
              }
              insidx++;  // Reset iterator to skip USE side split
              continue;
            }

            if (UseFPUForSpilling && n->is_MachCall() && !uup && !dup ) {
              // The use at the call can force the def down so insert
              // a split before the use to allow the def more freedom.
              maxlrg = split_USE(def,b,n,inpidx,maxlrg,dup,false, splits,slidx);
              // If it wasn't split bail
              if (!maxlrg) {
                return 0;
              }
              insidx++;  // Reset iterator to skip USE side split
              continue;
            }

            // Here is the logic chart which describes USE Splitting:
            // 0 = false or DOWN, 1 = true or UP
            //
            // Overlap | DEF | USE | Action
            //-------------------------------------------------------
            //    0    |  0  |  0  | Copy - mem -> mem
            //    0    |  0  |  1  | Split-UP - Check HRP
            //    0    |  1  |  0  | Split-DOWN - Debug Info?
            //    0    |  1  |  1  | Copy - reg -> reg
            //    1    |  0  |  0  | Reset Input Edge (no Split)
            //    1    |  0  |  1  | Split-UP - Check HRP
            //    1    |  1  |  0  | Split-DOWN - Debug Info?
            //    1    |  1  |  1  | Reset Input Edge (no Split)
            //
            // So, if (dup == uup), then overlap test determines action,
            // with true being no split, and false being copy. Else,
            // if DEF is DOWN, Split-UP, and check HRP to decide on
            // resetting DEF. Finally if DEF is UP, Split-DOWN, with
            // special handling for Debug Info.
            if( dup == uup ) {
              if( dmask.overlap(umask) ) {
                // Both are either up or down, and there is overlap, No Split
                n->set_req(inpidx, def);
              }
              else {  // Both are either up or down, and there is no overlap
                if( dup ) {  // If UP, reg->reg copy
                  // COPY ACROSS HERE - NO DEF - NO CISC SPILL
                  maxlrg = split_USE(def,b,n,inpidx,maxlrg,false,false, splits,slidx);
                  // If it wasn't split bail
                  if (!maxlrg) {
                    return 0;
                  }
                  insidx++;  // Reset iterator to skip USE side split
                }
                else {       // DOWN, mem->mem copy
                  // COPY UP & DOWN HERE - NO DEF - NO CISC SPILL
                  // First Split-UP to move value into Register
                  uint def_ideal = def->ideal_reg();
                  const RegMask* tmp_rm = Matcher::idealreg2regmask[def_ideal];
                  Node *spill = new (C) MachSpillCopyNode(def, dmask, *tmp_rm);
                  insert_proj( b, insidx, spill, maxlrg );
                  // Then Split-DOWN as if previous Split was DEF
                  maxlrg = split_USE(spill,b,n,inpidx,maxlrg,false,false, splits,slidx);
                  // If it wasn't split bail
                  if (!maxlrg) {
                    return 0;
                  }
                  insidx += 2;  // Reset iterator to skip USE side splits
                }
              }  // End else no overlap
            }  // End if dup == uup
            // dup != uup, so check dup for direction of Split
            else {
              if( dup ) {  // If UP, Split-DOWN and check Debug Info
                // If this node is already a SpillCopy, just patch the edge
                // except the case of spilling to stack.
                if( n->is_SpillCopy() ) {
                  RegMask tmp_rm(umask);
                  tmp_rm.SUBTRACT(Matcher::STACK_ONLY_mask);
                  if( dmask.overlap(tmp_rm) ) {
                    if( def != n->in(inpidx) ) {
                      n->set_req(inpidx, def);
                    }
                    continue;
                  }
                }
                // COPY DOWN HERE - NO DEF - NO CISC SPILL
                maxlrg = split_USE(def,b,n,inpidx,maxlrg,false,false, splits,slidx);
                // If it wasn't split bail
                if (!maxlrg) {
                  return 0;
                }
                insidx++;  // Reset iterator to skip USE side split
                // Check for debug-info split.  Capture it for later
                // debug splits of the same value
                if (jvms && jvms->debug_start() <= inpidx && inpidx < oopoff)
                  debug_defs[slidx] = n->in(inpidx);

              }
              else {       // DOWN, Split-UP and check register pressure
                if( is_high_pressure( b, &lrgs(useidx), insidx ) ) {
                  // COPY UP HERE - NO DEF - CISC SPILL
                  maxlrg = split_USE(def,b,n,inpidx,maxlrg,true,true, splits,slidx);
                  // If it wasn't split bail
                  if (!maxlrg) {
                    return 0;
                  }
                  insidx++;  // Reset iterator to skip USE side split
                } else {                          // LRP
                  // COPY UP HERE - WITH DEF - NO CISC SPILL
                  maxlrg = split_USE(def,b,n,inpidx,maxlrg,true,false, splits,slidx);
                  // If it wasn't split bail
                  if (!maxlrg) {
                    return 0;
                  }
                  // Flag this lift-up in a low-pressure block as
                  // already-spilled, so if it spills again it will
                  // spill hard (instead of not spilling hard and
                  // coalescing away).
                  set_was_spilled(n->in(inpidx));
                  // Since this is a new DEF, update Reachblock & UP
                  Reachblock[slidx] = n->in(inpidx);
                  UPblock[slidx] = true;
                  insidx++;  // Reset iterator to skip USE side split
                }
              }  // End else DOWN
            }  // End dup != uup
          }  // End if Spill USE
        }  // End For All Inputs
      }  // End If not nullcheck

      // ********** Handle DEFS **********
      // DEFS either Split DOWN in HRP regions or when the LRG is bound, or
      // just reset the Reaches info in LRP regions.  DEFS must always update
      // UP info.
      if( deflrg.reg() >= LRG::SPILL_REG ) {    // Spilled?
        uint slidx = lrg2reach[defidx];
        // Add to defs list for later assignment of new live range number
        defs->push(n);
        // Set a flag on the Node indicating it has already spilled.
        // Only do it for capacity spills not conflict spills.
        if( !deflrg._direct_conflict )
          set_was_spilled(n);
        assert(!n->is_Phi(),"Cannot insert Phi into DEFS list");
        // Grab UP info for DEF
        const RegMask &dmask = n->out_RegMask();
        bool defup = dmask.is_UP();
        int ireg = n->ideal_reg();
        bool is_vect = RegMask::is_vector(ireg);
        // Only split at Def if this is a HRP block or bound (and spilled once)
        if( !n->rematerialize() &&
            (((dmask.is_bound(ireg) || !is_vect && dmask.is_misaligned_pair()) &&
              (deflrg._direct_conflict || deflrg._must_spill)) ||
             // Check for LRG being up in a register and we are inside a high
             // pressure area.  Spill it down immediately.
             (defup && is_high_pressure(b,&deflrg,insidx))) ) {
          assert( !n->rematerialize(), "" );
          assert( !n->is_SpillCopy(), "" );
          // Do a split at the def site.
          maxlrg = split_DEF( n, b, insidx, maxlrg, Reachblock, debug_defs, splits, slidx );
          // If it wasn't split bail
          if (!maxlrg) {
            return 0;
          }
          // Split DEF's Down
          UPblock[slidx] = 0;
#ifndef PRODUCT
          // DEBUG
          if( trace_spilling() ) {
            tty->print("\nNew Split DOWN DEF of Spill Idx ");
            tty->print("%d, UP %d:\n",slidx,false);
            n->dump();
          }
#endif
        }
        else {                  // Neither bound nor HRP, must be LRP
          // otherwise, just record the def
          Reachblock[slidx] = n;
          // UP should come from the outRegmask() of the DEF
          UPblock[slidx] = defup;
          // Update debug list of reaching down definitions, kill if DEF is UP
          debug_defs[slidx] = defup ? NULL : n;
#ifndef PRODUCT
          // DEBUG
          if( trace_spilling() ) {
            tty->print("\nNew DEF of Spill Idx ");
            tty->print("%d, UP %d:\n",slidx,defup);
            n->dump();
          }
#endif
        }  // End else LRP
      }  // End if spill def

      // ********** Split Left Over Mem-Mem Moves **********
      // Check for mem-mem copies and split them now.  Do not do this
      // to copies about to be spilled; they will be Split shortly.
      if (copyidx) {
        Node *use = n->in(copyidx);
        uint useidx = _lrg_map.find_id(use);
        if (useidx < _lrg_map.max_lrg_id() &&       // This is not a new split
            OptoReg::is_stack(deflrg.reg()) &&
            deflrg.reg() < LRG::SPILL_REG ) { // And DEF is from stack
          LRG &uselrg = lrgs(useidx);
          if( OptoReg::is_stack(uselrg.reg()) &&
              uselrg.reg() < LRG::SPILL_REG && // USE is from stack
              deflrg.reg() != uselrg.reg() ) { // Not trivially removed
            uint def_ideal_reg = n->bottom_type()->ideal_reg();
            const RegMask &def_rm = *Matcher::idealreg2regmask[def_ideal_reg];
            const RegMask &use_rm = n->in_RegMask(copyidx);
            if( def_rm.overlap(use_rm) && n->is_SpillCopy() ) {  // Bug 4707800, 'n' may be a storeSSL
              if (C->check_node_count(NodeLimitFudgeFactor, out_of_nodes)) {  // Check when generating nodes
                return 0;
              }
              Node *spill = new (C) MachSpillCopyNode(use,use_rm,def_rm);
              n->set_req(copyidx,spill);
              n->as_MachSpillCopy()->set_in_RegMask(def_rm);
              // Put the spill just before the copy
              insert_proj( b, insidx++, spill, maxlrg++ );
            }
          }
        }
      }
    }  // End For All Instructions in Block - Non-PHI Pass

    // Check if each LRG is live out of this block so as not to propagate
    // beyond the last use of a LRG.
    for( slidx = 0; slidx < spill_cnt; slidx++ ) {
      uint defidx = lidxs.at(slidx);
      IndexSet *liveout = _live->live(b);
      if( !liveout->member(defidx) ) {
#ifdef ASSERT
        // The index defidx is not live.  Check the liveout array to ensure that
        // it contains no members which compress to defidx.  Finding such an
        // instance may be a case to add liveout adjustment in compress_uf_map().
        // See 5063219.
        uint member;
        IndexSetIterator isi(liveout);
        while ((member = isi.next()) != 0) {
          assert(defidx != _lrg_map.find_const(member), "Live out member has not been compressed");
        }
#endif
        Reachblock[slidx] = NULL;
      } else {
        assert(Reachblock[slidx] != NULL,"No reaching definition for liveout value");
      }
    }
#ifndef PRODUCT
    if( trace_spilling() )
      b->dump();
#endif
  }  // End For All Blocks

  //----------PASS 2----------
  // Reset all DEF live range numbers here
  for( insidx = 0; insidx < defs->size(); insidx++ ) {
    // Grab the def
    n1 = defs->at(insidx);
    // Set new lidx for DEF
    new_lrg(n1, maxlrg++);
  }
  //----------Phi Node Splitting----------
  // Clean up a phi here, and assign a new live range number
  // Cycle through this block's predecessors, collecting Reaches
  // info for each spilled LRG and update edges.
  // Walk the phis list to patch inputs, split phis, and name phis
  uint lrgs_before_phi_split = maxlrg;
  for( insidx = 0; insidx < phis->size(); insidx++ ) {
    Node *phi = phis->at(insidx);
    assert(phi->is_Phi(),"This list must only contain Phi Nodes");
    Block *b = _cfg.get_block_for_node(phi);
    // Grab the live range number
    uint lidx = _lrg_map.find_id(phi);
    uint slidx = lrg2reach[lidx];
    // Update node to lidx map
    new_lrg(phi, maxlrg++);
    // Get PASS1's up/down decision for the block.
    int phi_up = !!UP_entry[slidx]->test(b->_pre_order);

    // Force down if double-spilling live range
    if( lrgs(lidx)._was_spilled1 )
      phi_up = false;

    // When splitting a Phi we an split it normal or "inverted".
    // An inverted split makes the splits target the Phi's UP/DOWN
    // sense inverted; then the Phi is followed by a final def-side
    // split to invert back.  It changes which blocks the spill code
    // goes in.

    // Walk the predecessor blocks and assign the reaching def to the Phi.
    // Split Phi nodes by placing USE side splits wherever the reaching
    // DEF has the wrong UP/DOWN value.
    for( uint i = 1; i < b->num_preds(); i++ ) {
      // Get predecessor block pre-order number
      Block *pred = _cfg.get_block_for_node(b->pred(i));
      pidx = pred->_pre_order;
      // Grab reaching def
      Node *def = Reaches[pidx][slidx];
      assert( def, "must have reaching def" );
      // If input up/down sense and reg-pressure DISagree
      if (def->rematerialize() && contains_no_live_range_input(def)) {
        // Place the rematerialized node above any MSCs created during
        // phi node splitting.  end_idx points at the insertion point
        // so look at the node before it.
        int insert = pred->end_idx();
        while (insert >= 1 &&
               pred->get_node(insert - 1)->is_SpillCopy() &&
               _lrg_map.find(pred->get_node(insert - 1)) >= lrgs_before_phi_split) {
          insert--;
        }
        // since the def cannot contain any live range input, we can pass in NULL as Reachlock parameter
        def = split_Rematerialize(def, pred, insert, maxlrg, splits, slidx, lrg2reach, NULL, false);
        if (!def) {
          return 0;    // Bail out
        }
      }
      // Update the Phi's input edge array
      phi->set_req(i,def);
      // Grab the UP/DOWN sense for the input
      u1 = UP[pidx][slidx];
      if( u1 != (phi_up != 0)) {
        maxlrg = split_USE(def, b, phi, i, maxlrg, !u1, false, splits,slidx);
        // If it wasn't split bail
        if (!maxlrg) {
          return 0;
        }
      }
    }  // End for all inputs to the Phi
  }  // End for all Phi Nodes
  // Update _maxlrg to save Union asserts
  _lrg_map.set_max_lrg_id(maxlrg);


  //----------PASS 3----------
  // Pass over all Phi's to union the live ranges
  for( insidx = 0; insidx < phis->size(); insidx++ ) {
    Node *phi = phis->at(insidx);
    assert(phi->is_Phi(),"This list must only contain Phi Nodes");
    // Walk all inputs to Phi and Union input live range with Phi live range
    for( uint i = 1; i < phi->req(); i++ ) {
      // Grab the input node
      Node *n = phi->in(i);
      assert(n, "node should exist");
      uint lidx = _lrg_map.find(n);
      uint pidx = _lrg_map.find(phi);
      if (lidx < pidx) {
        Union(n, phi);
      }
      else if(lidx > pidx) {
        Union(phi, n);
      }
    }  // End for all inputs to the Phi Node
  }  // End for all Phi Nodes
  // Now union all two address instructions
  for (insidx = 0; insidx < defs->size(); insidx++) {
    // Grab the def
    n1 = defs->at(insidx);
    // Set new lidx for DEF & handle 2-addr instructions
    if (n1->is_Mach() && ((twoidx = n1->as_Mach()->two_adr()) != 0)) {
      assert(_lrg_map.find(n1->in(twoidx)) < maxlrg,"Assigning bad live range index");
      // Union the input and output live ranges
      uint lr1 = _lrg_map.find(n1);
      uint lr2 = _lrg_map.find(n1->in(twoidx));
      if (lr1 < lr2) {
        Union(n1, n1->in(twoidx));
      }
      else if (lr1 > lr2) {
        Union(n1->in(twoidx), n1);
      }
    }  // End if two address
  }  // End for all defs
  // DEBUG
#ifdef ASSERT
  // Validate all live range index assignments
  for (bidx = 0; bidx < _cfg.number_of_blocks(); bidx++) {
    b  = _cfg.get_block(bidx);
    for (insidx = 0; insidx <= b->end_idx(); insidx++) {
      Node *n = b->get_node(insidx);
      uint defidx = _lrg_map.find(n);
      assert(defidx < _lrg_map.max_lrg_id(), "Bad live range index in Split");
      assert(defidx < maxlrg,"Bad live range index in Split");
    }
  }
  // Issue a warning if splitting made no progress
  int noprogress = 0;
  for (slidx = 0; slidx < spill_cnt; slidx++) {
    if (PrintOpto && WizardMode && splits.at(slidx) == 0) {
      tty->print_cr("Failed to split live range %d", lidxs.at(slidx));
      //BREAKPOINT;
    }
    else {
      noprogress++;
    }
  }
  if(!noprogress) {
    tty->print_cr("Failed to make progress in Split");
    //BREAKPOINT;
  }
#endif
  // Return updated count of live ranges
  return maxlrg;
}