jdk8-mips64-public/hotspot: src/share/vm/opto/reg_split.cpp@006050192a5a (annotated)

src/share/vm/opto/reg_split.cpp@006050192a5a (annotated)

src/share/vm/opto/reg_split.cpp

Mon, 20 Aug 2012 09:07:21 -0700

author: kvn
date: Mon, 20 Aug 2012 09:07:21 -0700
changeset 4001: 006050192a5a
parent 3882: 8c92982cbbc4
child 4019: a1c7f6472621
permissions: -rw-r--r--

6340864: Implement vectorization optimizations in hotspot-server
Summary: Added asm encoding and mach nodes for vector arithmetic instructions on x86.
Reviewed-by: roland

 /*
  * 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
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  *
  */
 #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";
 //------------------------------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->_nodes.size() &&
          (b->_nodes[i]->is_Proj() ||
           b->_nodes[i]->is_Phi() ) )
     i++;
   // Do not insert between a call and his Catch
   if( b->_nodes[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->_nodes[++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->_nodes.insert(i,spill);    // Insert node in block
   _cfg._bbs.map(spill->_idx,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->_nodes[loc] ) {
     // Spill goes in the branch-not-taken block
     b = b->_succs[b->_nodes[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._bbs[use->_idx];
         // 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._bbs[b->pred(useidx)->_idx];
     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 = n2lidx(in);
       if( lidx >= _maxlrg ) continue; // Value is a recent spill-copy
       if (lrgs(lidx).is_singledef()) continue;
       Block *b_def = _cfg._bbs[def->_idx];
       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 = Find_id(in);
       // Walk backwards thru spill copy node intermediates
       if (walkThru) {
         while ( in->is_SpillCopy() && lidx >= _maxlrg ) {
           in = in->in(1);
           lidx = Find_id(in);
         }
         if (lidx < _maxlrg && 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 = Find_id(in);
         }
       }
       if( lidx < _maxlrg && lrgs(lidx).reg() >= LRG::SPILL_REG ) {
         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;
   if( clone_projs( b, i, def, spill, maxlrg ) ) {
     // Adjust the point where we go hi-pressure
     if( i <= b->_ihrp_index ) b->_ihrp_index++;
     if( i <= b->_fhrp_index ) b->_fhrp_index++;
   }
   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->_nodes[i];
     // Ignore PHI use, these can be up or down
     if( n->is_Phi() ) continue;
     for( uint j = 1; j < n->req(); j++ )
       if( 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 ) {
   NOT_PRODUCT( Compile::TracePhase t3("regAllocSplit", &_t_regAllocSplit, TimeCompiler); )
   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;
   // Array of counters to count splits per live range
   GrowableArray<uint>  splits;
   //----------Setup Code----------
   // Create a convenient mapping from lrg numbers to reaches/leaves indices
   uint *lrg2reach = NEW_RESOURCE_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_RESOURCE_ARRAY( Node**, _cfg._num_blocks+1 );
   bool  **UP          = NEW_RESOURCE_ARRAY( bool*, _cfg._num_blocks+1 );
   Node  **debug_defs  = NEW_RESOURCE_ARRAY( Node*, spill_cnt );
   VectorSet **UP_entry= NEW_RESOURCE_ARRAY( VectorSet*, spill_cnt );
   // Initialize Reaches & UP
   for( bidx = 0; bidx < _cfg._num_blocks+1; bidx++ ) {
     Reaches[bidx]     = NEW_RESOURCE_ARRAY( Node*, spill_cnt );
     UP[bidx]          = NEW_RESOURCE_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
     }
   }
   // Initialize to array of empty vectorsets
   for( slidx = 0; slidx < spill_cnt; slidx++ )
     UP_entry[slidx] = new VectorSet(Thread::current()->resource_area());
   //----------PASS 1----------
   //----------Propagation & Node Insertion Code----------
   // Walk the Blocks in RPO for DEF & USE info
   for( bidx = 0; bidx < _cfg._num_blocks; bidx++ ) {
     if (C->check_node_count(spill_cnt, out_of_nodes)) {
       return 0;
     }
     b  = _cfg._blocks[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._bbs[b->pred(1)->_idx];
         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._bbs[n1->_idx];
       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._bbs[n2->_idx];
         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->_nodes[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( 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, b->num_preds()) 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
           _names.map(phi->_idx, lidx);
           assert(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._bbs[n1->_idx];
         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->_nodes[insidx];
       // Find the defining Node's live range index
       uint defidx = Find_id(n);
       uint cnt = n->req();
       if( n->is_Phi() ) {
         // Skip phi nodes after removing dead copies.
         if( defidx < _maxlrg ) {
           // 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(Find_id(n) == Find_id(u), "should be the same lrg");
               n->replace_by(u); // Then replace with unique input
               n->disconnect_inputs(NULL);
               b->_nodes.remove(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->_nodes[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->_nodes[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->_nodes[insert_point];
                   // Hit top of block?  Quit going backwards
                   if( n->is_Phi() ) break;
                   // Found a def?  Better split after it.
                   if( n2lidx(n) == lidx ) break;
                   // Look for a use
                   uint i;
                   for( i = 1; i < n->req(); i++ )
                     if( n2lidx(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->_nodes[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 >= _maxlrg ) {
         continue;
       }
       LRG &deflrg = lrgs(defidx);
       uint copyidx = n->is_Copy();
       // Remove coalesced copy from CFG
       if( copyidx && defidx == n2lidx(n->in(copyidx)) ) {
         n->replace_by( n->in(copyidx) );
         n->set_req( copyidx, NULL );
         b->_nodes.remove(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 = Find_id(n->in(inpidx));
           // Not a brand-new split, and it is a spill use
           if( useidx < _maxlrg && 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;
               }
               _names.extend(def->_idx,0);
               _cfg._bbs.map(def->_idx,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->_nodes.size();
               def = split_Rematerialize( def, b, insidx, maxlrg, splits, slidx, lrg2reach, Reachblock, true );
               if( !def ) return 0; // Bail out
               insidx += b->_nodes.size()-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 = Find_id(use);
         if( useidx < _maxlrg &&       // 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 = Matcher::base2reg[n->bottom_type()->base()];
             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 != 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._bbs[phi->_idx];
     // Grab the live range number
     uint lidx = 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._bbs[b->pred(i)->_idx];
       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() ) {
         // 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->_nodes[insert - 1]->is_SpillCopy() &&
                Find(pred->_nodes[insert - 1]) >= lrgs_before_phi_split) {
           insert--;
         }
         def = split_Rematerialize( def, pred, insert, maxlrg, splits, slidx, lrg2reach, Reachblock, 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
   _maxlrg = 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, "" );
       uint lidx = Find(n);
       uint pidx = 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( Find(n1->in(twoidx)) < maxlrg,"Assigning bad live range index");
       // Union the input and output live ranges
       uint lr1 = Find(n1);
       uint lr2 = 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._num_blocks; bidx++ ) {
     b  = _cfg._blocks[bidx];
     for( insidx = 0; insidx <= b->end_idx(); insidx++ ) {
       Node *n = b->_nodes[insidx];
       uint defidx = Find(n);
       assert(defidx < _maxlrg,"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;
 }

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/opto/reg_split.cpp@006050192a5a (annotated)

src/share/vm/opto/reg_split.cpp