jdk8-mips64-public/hotspot: src/share/vm/opto/coalesce.cpp@98cb887364d3 (annotated)

src/share/vm/opto/coalesce.cpp@98cb887364d3 (annotated)

src/share/vm/opto/coalesce.cpp

Fri, 27 Feb 2009 13:27:09 -0800

author: twisti
date: Fri, 27 Feb 2009 13:27:09 -0800
changeset 1040: 98cb887364d3
parent 772: 9ee9cf798b59
child 1108: fbc12e71c476
permissions: -rw-r--r--

6810672: Comment typos
Summary: I have collected some typos I have found while looking at the code.
Reviewed-by: kvn, never

 /*
  * Copyright 1997-2008 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
  * CA 95054 USA or visit www.sun.com if you need additional information or
  * have any questions.
  *
  */
 #include "incls/_precompiled.incl"
 #include "incls/_coalesce.cpp.incl"
 //=============================================================================
 //------------------------------reset_uf_map-----------------------------------
 void PhaseChaitin::reset_uf_map( uint maxlrg ) {
   _maxlrg = maxlrg;
   // Force the Union-Find mapping to be at least this large
   _uf_map.extend(_maxlrg,0);
   // Initialize it to be the ID mapping.
   for( uint i=0; i<_maxlrg; i++ )
     _uf_map.map(i,i);
 }
 //------------------------------compress_uf_map--------------------------------
 // Make all Nodes map directly to their final live range; no need for
 // the Union-Find mapping after this call.
 void PhaseChaitin::compress_uf_map_for_nodes( ) {
   // For all Nodes, compress mapping
   uint unique = _names.Size();
   for( uint i=0; i<unique; i++ ) {
     uint lrg = _names[i];
     uint compressed_lrg = Find(lrg);
     if( lrg != compressed_lrg )
       _names.map(i,compressed_lrg);
   }
 }
 //------------------------------Find-------------------------------------------
 // Straight out of Tarjan's union-find algorithm
 uint PhaseChaitin::Find_compress( uint lrg ) {
   uint cur = lrg;
   uint next = _uf_map[cur];
   while( next != cur ) {        // Scan chain of equivalences
     assert( next < cur, "always union smaller" );
     cur = next;                 // until find a fixed-point
     next = _uf_map[cur];
   }
   // Core of union-find algorithm: update chain of
   // equivalences to be equal to the root.
   while( lrg != next ) {
     uint tmp = _uf_map[lrg];
     _uf_map.map(lrg, next);
     lrg = tmp;
   }
   return lrg;
 }
 //------------------------------Find-------------------------------------------
 // Straight out of Tarjan's union-find algorithm
 uint PhaseChaitin::Find_compress( const Node *n ) {
   uint lrg = Find_compress(_names[n->_idx]);
   _names.map(n->_idx,lrg);
   return lrg;
 }
 //------------------------------Find_const-------------------------------------
 // Like Find above, but no path compress, so bad asymptotic behavior
 uint PhaseChaitin::Find_const( uint lrg ) const {
   if( !lrg ) return lrg;        // Ignore the zero LRG
   // Off the end?  This happens during debugging dumps when you got
   // brand new live ranges but have not told the allocator yet.
   if( lrg >= _maxlrg ) return lrg;
   uint next = _uf_map[lrg];
   while( next != lrg ) {        // Scan chain of equivalences
     assert( next < lrg, "always union smaller" );
     lrg = next;                 // until find a fixed-point
     next = _uf_map[lrg];
   }
   return next;
 }
 //------------------------------Find-------------------------------------------
 // Like Find above, but no path compress, so bad asymptotic behavior
 uint PhaseChaitin::Find_const( const Node *n ) const {
   if( n->_idx >= _names.Size() ) return 0; // not mapped, usual for debug dump
   return Find_const( _names[n->_idx] );
 }
 //------------------------------Union------------------------------------------
 // union 2 sets together.
 void PhaseChaitin::Union( const Node *src_n, const Node *dst_n ) {
   uint src = Find(src_n);
   uint dst = Find(dst_n);
   assert( src, "" );
   assert( dst, "" );
   assert( src < _maxlrg, "oob" );
   assert( dst < _maxlrg, "oob" );
   assert( src < dst, "always union smaller" );
   _uf_map.map(dst,src);
 }
 //------------------------------new_lrg----------------------------------------
 void PhaseChaitin::new_lrg( const Node *x, uint lrg ) {
   // Make the Node->LRG mapping
   _names.extend(x->_idx,lrg);
   // Make the Union-Find mapping an identity function
   _uf_map.extend(lrg,lrg);
 }
 //------------------------------clone_projs------------------------------------
 // After cloning some rematerialized instruction, clone any MachProj's that
 // follow it.  Example: Intel zero is XOR, kills flags.  Sparc FP constants
 // use G3 as an address temp.
 int PhaseChaitin::clone_projs( Block *b, uint idx, Node *con, Node *copy, uint &maxlrg ) {
   Block *bcon = _cfg._bbs[con->_idx];
   uint cindex = bcon->find_node(con);
   Node *con_next = bcon->_nodes[cindex+1];
   if( con_next->in(0) != con || con_next->Opcode() != Op_MachProj )
     return false;               // No MachProj's follow
   // Copy kills after the cloned constant
   Node *kills = con_next->clone();
   kills->set_req( 0, copy );
   b->_nodes.insert( idx, kills );
   _cfg._bbs.map( kills->_idx, b );
   new_lrg( kills, maxlrg++ );
   return true;
 }
 //------------------------------compact----------------------------------------
 // Renumber the live ranges to compact them.  Makes the IFG smaller.
 void PhaseChaitin::compact() {
   // Current the _uf_map contains a series of short chains which are headed
   // by a self-cycle.  All the chains run from big numbers to little numbers.
   // The Find() call chases the chains & shortens them for the next Find call.
   // We are going to change this structure slightly.  Numbers above a moving
   // wave 'i' are unchanged.  Numbers below 'j' point directly to their
   // compacted live range with no further chaining.  There are no chains or
   // cycles below 'i', so the Find call no longer works.
   uint j=1;
   uint i;
   for( i=1; i < _maxlrg; i++ ) {
     uint lr = _uf_map[i];
     // Ignore unallocated live ranges
     if( !lr ) continue;
     assert( lr <= i, "" );
     _uf_map.map(i, ( lr == i ) ? j++ : _uf_map[lr]);
   }
   if( false )                  // PrintOptoCompactLiveRanges
     printf("Compacted %d LRs from %d\n",i-j,i);
   // Now change the Node->LR mapping to reflect the compacted names
   uint unique = _names.Size();
   for( i=0; i<unique; i++ )
     _names.map(i,_uf_map[_names[i]]);
   // Reset the Union-Find mapping
   reset_uf_map(j);
 }
 //=============================================================================
 //------------------------------Dump-------------------------------------------
 #ifndef PRODUCT
 void PhaseCoalesce::dump( Node *n ) const {
   // Being a const function means I cannot use 'Find'
   uint r = _phc.Find(n);
   tty->print("L%d/N%d ",r,n->_idx);
 }
 //------------------------------dump-------------------------------------------
 void PhaseCoalesce::dump() const {
   // I know I have a block layout now, so I can print blocks in a loop
   for( uint i=0; i<_phc._cfg._num_blocks; i++ ) {
     uint j;
     Block *b = _phc._cfg._blocks[i];
     // Print a nice block header
     tty->print("B%d: ",b->_pre_order);
     for( j=1; j<b->num_preds(); j++ )
       tty->print("B%d ", _phc._cfg._bbs[b->pred(j)->_idx]->_pre_order);
     tty->print("-> ");
     for( j=0; j<b->_num_succs; j++ )
       tty->print("B%d ",b->_succs[j]->_pre_order);
     tty->print(" IDom: B%d/#%d\n", b->_idom ? b->_idom->_pre_order : 0, b->_dom_depth);
     uint cnt = b->_nodes.size();
     for( j=0; j<cnt; j++ ) {
       Node *n = b->_nodes[j];
       dump( n );
       tty->print("\t%s\t",n->Name());
       // Dump the inputs
       uint k;                   // Exit value of loop
       for( k=0; k<n->req(); k++ ) // For all required inputs
         if( n->in(k) ) dump( n->in(k) );
         else tty->print("_ ");
       int any_prec = 0;
       for( ; k<n->len(); k++ )          // For all precedence inputs
         if( n->in(k) ) {
           if( !any_prec++ ) tty->print(" |");
           dump( n->in(k) );
         }
       // Dump node-specific info
       n->dump_spec(tty);
       tty->print("\n");
     }
     tty->print("\n");
   }
 }
 #endif
 //------------------------------combine_these_two------------------------------
 // Combine the live ranges def'd by these 2 Nodes.  N2 is an input to N1.
 void PhaseCoalesce::combine_these_two( Node *n1, Node *n2 ) {
   uint lr1 = _phc.Find(n1);
   uint lr2 = _phc.Find(n2);
   if( lr1 != lr2 &&             // Different live ranges already AND
       !_phc._ifg->test_edge_sq( lr1, lr2 ) ) {  // Do not interfere
     LRG *lrg1 = &_phc.lrgs(lr1);
     LRG *lrg2 = &_phc.lrgs(lr2);
     // Not an oop->int cast; oop->oop, int->int, AND int->oop are OK.
     // Now, why is int->oop OK?  We end up declaring a raw-pointer as an oop
     // and in general that's a bad thing.  However, int->oop conversions only
     // happen at GC points, so the lifetime of the misclassified raw-pointer
     // is from the CheckCastPP (that converts it to an oop) backwards up
     // through a merge point and into the slow-path call, and around the
     // diamond up to the heap-top check and back down into the slow-path call.
     // The misclassified raw pointer is NOT live across the slow-path call,
     // and so does not appear in any GC info, so the fact that it is
     // misclassified is OK.
     if( (lrg1->_is_oop || !lrg2->_is_oop) && // not an oop->int cast AND
         // Compatible final mask
         lrg1->mask().overlap( lrg2->mask() ) ) {
       // Merge larger into smaller.
       if( lr1 > lr2 ) {
         uint  tmp =  lr1;  lr1 =  lr2;  lr2 =  tmp;
         Node   *n =   n1;   n1 =   n2;   n2 =    n;
         LRG *ltmp = lrg1; lrg1 = lrg2; lrg2 = ltmp;
       }
       // Union lr2 into lr1
       _phc.Union( n1, n2 );
       if (lrg1->_maxfreq < lrg2->_maxfreq)
         lrg1->_maxfreq = lrg2->_maxfreq;
       // Merge in the IFG
       _phc._ifg->Union( lr1, lr2 );
       // Combine register restrictions
       lrg1->AND(lrg2->mask());
     }
   }
 }
 //------------------------------coalesce_driver--------------------------------
 // Copy coalescing
 void PhaseCoalesce::coalesce_driver( ) {
   verify();
   // Coalesce from high frequency to low
   for( uint i=0; i<_phc._cfg._num_blocks; i++ )
     coalesce( _phc._blks[i] );
 }
 //------------------------------insert_copy_with_overlap-----------------------
 // I am inserting copies to come out of SSA form.  In the general case, I am
 // doing a parallel renaming.  I'm in the Named world now, so I can't do a
 // general parallel renaming.  All the copies now use  "names" (live-ranges)
 // to carry values instead of the explicit use-def chains.  Suppose I need to
 // insert 2 copies into the same block.  They copy L161->L128 and L128->L132.
 // If I insert them in the wrong order then L128 will get clobbered before it
 // can get used by the second copy.  This cannot happen in the SSA model;
 // direct use-def chains get me the right value.  It DOES happen in the named
 // model so I have to handle the reordering of copies.
 //
 // In general, I need to topo-sort the placed copies to avoid conflicts.
 // Its possible to have a closed cycle of copies (e.g., recirculating the same
 // values around a loop).  In this case I need a temp to break the cycle.
 void PhaseAggressiveCoalesce::insert_copy_with_overlap( Block *b, Node *copy, uint dst_name, uint src_name ) {
   // Scan backwards for the locations of the last use of the dst_name.
   // I am about to clobber the dst_name, so the copy must be inserted
   // after the last use.  Last use is really first-use on a backwards scan.
   uint i = b->end_idx()-1;
   while( 1 ) {
     Node *n = b->_nodes[i];
     // Check for end of virtual copies; this is also the end of the
     // parallel renaming effort.
     if( n->_idx < _unique ) break;
     uint idx = n->is_Copy();
     assert( idx || n->is_Con() || n->Opcode() == Op_MachProj, "Only copies during parallel renaming" );
     if( idx && _phc.Find(n->in(idx)) == dst_name ) break;
     i--;
   }
   uint last_use_idx = i;
   // Also search for any kill of src_name that exits the block.
   // Since the copy uses src_name, I have to come before any kill.
   uint kill_src_idx = b->end_idx();
   // There can be only 1 kill that exits any block and that is
   // the last kill.  Thus it is the first kill on a backwards scan.
   i = b->end_idx()-1;
   while( 1 ) {
     Node *n = b->_nodes[i];
     // Check for end of virtual copies; this is also the end of the
     // parallel renaming effort.
     if( n->_idx < _unique ) break;
     assert( n->is_Copy() || n->is_Con() || n->Opcode() == Op_MachProj, "Only copies during parallel renaming" );
     if( _phc.Find(n) == src_name ) {
       kill_src_idx = i;
       break;
     }
     i--;
   }
   // Need a temp?  Last use of dst comes after the kill of src?
   if( last_use_idx >= kill_src_idx ) {
     // Need to break a cycle with a temp
     uint idx = copy->is_Copy();
     Node *tmp = copy->clone();
     _phc.new_lrg(tmp,_phc._maxlrg++);
     // Insert new temp between copy and source
     tmp ->set_req(idx,copy->in(idx));
     copy->set_req(idx,tmp);
     // Save source in temp early, before source is killed
     b->_nodes.insert(kill_src_idx,tmp);
     _phc._cfg._bbs.map( tmp->_idx, b );
     last_use_idx++;
   }
   // Insert just after last use
   b->_nodes.insert(last_use_idx+1,copy);
 }
 //------------------------------insert_copies----------------------------------
 void PhaseAggressiveCoalesce::insert_copies( Matcher &matcher ) {
   // We do LRGs compressing and fix a liveout data only here since the other
   // place in Split() is guarded by the assert which we never hit.
   _phc.compress_uf_map_for_nodes();
   // Fix block's liveout data for compressed live ranges.
   for(uint lrg = 1; lrg < _phc._maxlrg; lrg++ ) {
     uint compressed_lrg = _phc.Find(lrg);
     if( lrg != compressed_lrg ) {
       for( uint bidx = 0; bidx < _phc._cfg._num_blocks; bidx++ ) {
         IndexSet *liveout = _phc._live->live(_phc._cfg._blocks[bidx]);
         if( liveout->member(lrg) ) {
           liveout->remove(lrg);
           liveout->insert(compressed_lrg);
         }
       }
     }
   }
   // All new nodes added are actual copies to replace virtual copies.
   // Nodes with index less than '_unique' are original, non-virtual Nodes.
   _unique = C->unique();
   for( uint i=0; i<_phc._cfg._num_blocks; i++ ) {
     Block *b = _phc._cfg._blocks[i];
     uint cnt = b->num_preds();  // Number of inputs to the Phi
     for( uint l = 1; l<b->_nodes.size(); l++ ) {
       Node *n = b->_nodes[l];
       // Do not use removed-copies, use copied value instead
       uint ncnt = n->req();
       for( uint k = 1; k<ncnt; k++ ) {
         Node *copy = n->in(k);
         uint cidx = copy->is_Copy();
         if( cidx ) {
           Node *def = copy->in(cidx);
           if( _phc.Find(copy) == _phc.Find(def) )
             n->set_req(k,def);
         }
       }
       // Remove any explicit copies that get coalesced.
       uint cidx = n->is_Copy();
       if( cidx ) {
         Node *def = n->in(cidx);
         if( _phc.Find(n) == _phc.Find(def) ) {
           n->replace_by(def);
           n->set_req(cidx,NULL);
           b->_nodes.remove(l);
           l--;
           continue;
         }
       }
       if( n->is_Phi() ) {
         // Get the chosen name for the Phi
         uint phi_name = _phc.Find( n );
         // Ignore the pre-allocated specials
         if( !phi_name ) continue;
         // Check for mismatch inputs to Phi
         for( uint j = 1; j<cnt; j++ ) {
           Node *m = n->in(j);
           uint src_name = _phc.Find(m);
           if( src_name != phi_name ) {
             Block *pred = _phc._cfg._bbs[b->pred(j)->_idx];
             Node *copy;
             assert(!m->is_Con() || m->is_Mach(), "all Con must be Mach");
             // Rematerialize constants instead of copying them
             if( m->is_Mach() && m->as_Mach()->is_Con() &&
                 m->as_Mach()->rematerialize() ) {
               copy = m->clone();
               // Insert the copy in the predecessor basic block
               pred->add_inst(copy);
               // Copy any flags as well
               _phc.clone_projs( pred, pred->end_idx(), m, copy, _phc._maxlrg );
             } else {
               const RegMask *rm = C->matcher()->idealreg2spillmask[m->ideal_reg()];
               copy = new (C) MachSpillCopyNode(m,*rm,*rm);
               // Find a good place to insert.  Kinda tricky, use a subroutine
               insert_copy_with_overlap(pred,copy,phi_name,src_name);
             }
             // Insert the copy in the use-def chain
             n->set_req( j, copy );
             _phc._cfg._bbs.map( copy->_idx, pred );
             // Extend ("register allocate") the names array for the copy.
             _phc._names.extend( copy->_idx, phi_name );
           } // End of if Phi names do not match
         } // End of for all inputs to Phi
       } else { // End of if Phi
         // Now check for 2-address instructions
         uint idx;
         if( n->is_Mach() && (idx=n->as_Mach()->two_adr()) ) {
           // Get the chosen name for the Node
           uint name = _phc.Find( n );
           assert( name, "no 2-address specials" );
           // Check for name mis-match on the 2-address input
           Node *m = n->in(idx);
           if( _phc.Find(m) != name ) {
             Node *copy;
             assert(!m->is_Con() || m->is_Mach(), "all Con must be Mach");
             // At this point it is unsafe to extend live ranges (6550579).
             // Rematerialize only constants as we do for Phi above.
             if( m->is_Mach() && m->as_Mach()->is_Con() &&
                 m->as_Mach()->rematerialize() ) {
               copy = m->clone();
               // Insert the copy in the basic block, just before us
               b->_nodes.insert( l++, copy );
               if( _phc.clone_projs( b, l, m, copy, _phc._maxlrg ) )
                 l++;
             } else {
               const RegMask *rm = C->matcher()->idealreg2spillmask[m->ideal_reg()];
               copy = new (C) MachSpillCopyNode( m, *rm, *rm );
               // Insert the copy in the basic block, just before us
               b->_nodes.insert( l++, copy );
             }
             // Insert the copy in the use-def chain
             n->set_req(idx, copy );
             // Extend ("register allocate") the names array for the copy.
             _phc._names.extend( copy->_idx, name );
             _phc._cfg._bbs.map( copy->_idx, b );
           }
         } // End of is two-adr
         // Insert a copy at a debug use for a lrg which has high frequency
         if( (b->_freq < OPTO_DEBUG_SPLIT_FREQ) && n->is_MachSafePoint() ) {
           // Walk the debug inputs to the node and check for lrg freq
           JVMState* jvms = n->jvms();
           uint debug_start = jvms ? jvms->debug_start() : 999999;
           uint debug_end   = jvms ? jvms->debug_end()   : 999999;
           for(uint inpidx = debug_start; inpidx < debug_end; inpidx++) {
             // Do not split monitors; they are only needed for debug table
             // entries and need no code.
             if( jvms->is_monitor_use(inpidx) ) continue;
             Node *inp = n->in(inpidx);
             uint nidx = _phc.n2lidx(inp);
             LRG &lrg = lrgs(nidx);
             // If this lrg has a high frequency use/def
             if( lrg._maxfreq >= OPTO_LRG_HIGH_FREQ ) {
               // If the live range is also live out of this block (like it
               // would be for a fast/slow idiom), the normal spill mechanism
               // does an excellent job.  If it is not live out of this block
               // (like it would be for debug info to uncommon trap) splitting
               // the live range now allows a better allocation in the high
               // frequency blocks.
               //   Build_IFG_virtual has converted the live sets to
               // live-IN info, not live-OUT info.
               uint k;
               for( k=0; k < b->_num_succs; k++ )
                 if( _phc._live->live(b->_succs[k])->member( nidx ) )
                   break;      // Live in to some successor block?
               if( k < b->_num_succs )
                 continue;     // Live out; do not pre-split
               // Split the lrg at this use
               const RegMask *rm = C->matcher()->idealreg2spillmask[inp->ideal_reg()];
               Node *copy = new (C) MachSpillCopyNode( inp, *rm, *rm );
               // Insert the copy in the use-def chain
               n->set_req(inpidx, copy );
               // Insert the copy in the basic block, just before us
               b->_nodes.insert( l++, copy );
               // Extend ("register allocate") the names array for the copy.
               _phc.new_lrg( copy, _phc._maxlrg++ );
               _phc._cfg._bbs.map( copy->_idx, b );
               //tty->print_cr("Split a debug use in Aggressive Coalesce");
             }  // End of if high frequency use/def
           }  // End of for all debug inputs
         }  // End of if low frequency safepoint
       } // End of if Phi
     } // End of for all instructions
   } // End of for all blocks
 }
 //=============================================================================
 //------------------------------coalesce---------------------------------------
 // Aggressive (but pessimistic) copy coalescing of a single block
 // The following coalesce pass represents a single round of aggressive
 // pessimistic coalesce.  "Aggressive" means no attempt to preserve
 // colorability when coalescing.  This occasionally means more spills, but
 // it also means fewer rounds of coalescing for better code - and that means
 // faster compiles.
 // "Pessimistic" means we do not hit the fixed point in one pass (and we are
 // reaching for the least fixed point to boot).  This is typically solved
 // with a few more rounds of coalescing, but the compiler must run fast.  We
 // could optimistically coalescing everything touching PhiNodes together
 // into one big live range, then check for self-interference.  Everywhere
 // the live range interferes with self it would have to be split.  Finding
 // the right split points can be done with some heuristics (based on
 // expected frequency of edges in the live range).  In short, it's a real
 // research problem and the timeline is too short to allow such research.
 // Further thoughts: (1) build the LR in a pass, (2) find self-interference
 // in another pass, (3) per each self-conflict, split, (4) split by finding
 // the low-cost cut (min-cut) of the LR, (5) edges in the LR are weighted
 // according to the GCM algorithm (or just exec freq on CFG edges).
 void PhaseAggressiveCoalesce::coalesce( Block *b ) {
   // Copies are still "virtual" - meaning we have not made them explicitly
   // copies.  Instead, Phi functions of successor blocks have mis-matched
   // live-ranges.  If I fail to coalesce, I'll have to insert a copy to line
   // up the live-ranges.  Check for Phis in successor blocks.
   uint i;
   for( i=0; i<b->_num_succs; i++ ) {
     Block *bs = b->_succs[i];
     // Find index of 'b' in 'bs' predecessors
     uint j=1;
     while( _phc._cfg._bbs[bs->pred(j)->_idx] != b ) j++;
     // Visit all the Phis in successor block
     for( uint k = 1; k<bs->_nodes.size(); k++ ) {
       Node *n = bs->_nodes[k];
       if( !n->is_Phi() ) break;
       combine_these_two( n, n->in(j) );
     }
   } // End of for all successor blocks
   // Check _this_ block for 2-address instructions and copies.
   uint cnt = b->end_idx();
   for( i = 1; i<cnt; i++ ) {
     Node *n = b->_nodes[i];
     uint idx;
     // 2-address instructions have a virtual Copy matching their input
     // to their output
     if( n->is_Mach() && (idx = n->as_Mach()->two_adr()) ) {
       MachNode *mach = n->as_Mach();
       combine_these_two( mach, mach->in(idx) );
     }
   } // End of for all instructions in block
 }
 //=============================================================================
 //------------------------------PhaseConservativeCoalesce----------------------
 PhaseConservativeCoalesce::PhaseConservativeCoalesce( PhaseChaitin &chaitin ) : PhaseCoalesce(chaitin) {
   _ulr.initialize(_phc._maxlrg);
 }
 //------------------------------verify-----------------------------------------
 void PhaseConservativeCoalesce::verify() {
 #ifdef ASSERT
   _phc.set_was_low();
 #endif
 }
 //------------------------------union_helper-----------------------------------
 void PhaseConservativeCoalesce::union_helper( Node *lr1_node, Node *lr2_node, uint lr1, uint lr2, Node *src_def, Node *dst_copy, Node *src_copy, Block *b, uint bindex ) {
   // Join live ranges.  Merge larger into smaller.  Union lr2 into lr1 in the
   // union-find tree
   _phc.Union( lr1_node, lr2_node );
   // Single-def live range ONLY if both live ranges are single-def.
   // If both are single def, then src_def powers one live range
   // and def_copy powers the other.  After merging, src_def powers
   // the combined live range.
   lrgs(lr1)._def = (lrgs(lr1).is_multidef() ||
                         lrgs(lr2).is_multidef() )
     ? NodeSentinel : src_def;
   lrgs(lr2)._def = NULL;    // No def for lrg 2
   lrgs(lr2).Clear();        // Force empty mask for LRG 2
   //lrgs(lr2)._size = 0;      // Live-range 2 goes dead
   lrgs(lr1)._is_oop |= lrgs(lr2)._is_oop;
   lrgs(lr2)._is_oop = 0;    // In particular, not an oop for GC info
   if (lrgs(lr1)._maxfreq < lrgs(lr2)._maxfreq)
     lrgs(lr1)._maxfreq = lrgs(lr2)._maxfreq;
   // Copy original value instead.  Intermediate copies go dead, and
   // the dst_copy becomes useless.
   int didx = dst_copy->is_Copy();
   dst_copy->set_req( didx, src_def );
   // Add copy to free list
   // _phc.free_spillcopy(b->_nodes[bindex]);
   assert( b->_nodes[bindex] == dst_copy, "" );
   dst_copy->replace_by( dst_copy->in(didx) );
   dst_copy->set_req( didx, NULL);
   b->_nodes.remove(bindex);
   if( bindex < b->_ihrp_index ) b->_ihrp_index--;
   if( bindex < b->_fhrp_index ) b->_fhrp_index--;
   // Stretched lr1; add it to liveness of intermediate blocks
   Block *b2 = _phc._cfg._bbs[src_copy->_idx];
   while( b != b2 ) {
     b = _phc._cfg._bbs[b->pred(1)->_idx];
     _phc._live->live(b)->insert(lr1);
   }
 }
 //------------------------------compute_separating_interferences---------------
 // Factored code from copy_copy that computes extra interferences from
 // lengthening a live range by double-coalescing.
 uint PhaseConservativeCoalesce::compute_separating_interferences(Node *dst_copy, Node *src_copy, Block *b, uint bindex, RegMask &rm, uint reg_degree, uint rm_size, uint lr1, uint lr2 ) {
   assert(!lrgs(lr1)._fat_proj, "cannot coalesce fat_proj");
   assert(!lrgs(lr2)._fat_proj, "cannot coalesce fat_proj");
   Node *prev_copy = dst_copy->in(dst_copy->is_Copy());
   Block *b2 = b;
   uint bindex2 = bindex;
   while( 1 ) {
     // Find previous instruction
     bindex2--;                  // Chain backwards 1 instruction
     while( bindex2 == 0 ) {     // At block start, find prior block
       assert( b2->num_preds() == 2, "cannot double coalesce across c-flow" );
       b2 = _phc._cfg._bbs[b2->pred(1)->_idx];
       bindex2 = b2->end_idx()-1;
     }
     // Get prior instruction
     assert(bindex2 < b2->_nodes.size(), "index out of bounds");
     Node *x = b2->_nodes[bindex2];
     if( x == prev_copy ) {      // Previous copy in copy chain?
       if( prev_copy == src_copy)// Found end of chain and all interferences
         break;                  // So break out of loop
       // Else work back one in copy chain
       prev_copy = prev_copy->in(prev_copy->is_Copy());
     } else {                    // Else collect interferences
       uint lidx = _phc.Find(x);
       // Found another def of live-range being stretched?
       if( lidx == lr1 ) return max_juint;
       if( lidx == lr2 ) return max_juint;
       // If we attempt to coalesce across a bound def
       if( lrgs(lidx).is_bound() ) {
         // Do not let the coalesced LRG expect to get the bound color
         rm.SUBTRACT( lrgs(lidx).mask() );
         // Recompute rm_size
         rm_size = rm.Size();
         //if( rm._flags ) rm_size += 1000000;
         if( reg_degree >= rm_size ) return max_juint;
       }
       if( rm.overlap(lrgs(lidx).mask()) ) {
         // Insert lidx into union LRG; returns TRUE if actually inserted
         if( _ulr.insert(lidx) ) {
           // Infinite-stack neighbors do not alter colorability, as they
           // can always color to some other color.
           if( !lrgs(lidx).mask().is_AllStack() ) {
             // If this coalesce will make any new neighbor uncolorable,
             // do not coalesce.
             if( lrgs(lidx).just_lo_degree() )
               return max_juint;
             // Bump our degree
             if( ++reg_degree >= rm_size )
               return max_juint;
           } // End of if not infinite-stack neighbor
         } // End of if actually inserted
       } // End of if live range overlaps
     } // End of else collect interferences for 1 node
   } // End of while forever, scan back for interferences
   return reg_degree;
 }
 //------------------------------update_ifg-------------------------------------
 void PhaseConservativeCoalesce::update_ifg(uint lr1, uint lr2, IndexSet *n_lr1, IndexSet *n_lr2) {
   // Some original neighbors of lr1 might have gone away
   // because the constrained register mask prevented them.
   // Remove lr1 from such neighbors.
   IndexSetIterator one(n_lr1);
   uint neighbor;
   LRG &lrg1 = lrgs(lr1);
   while ((neighbor = one.next()) != 0)
     if( !_ulr.member(neighbor) )
       if( _phc._ifg->neighbors(neighbor)->remove(lr1) )
         lrgs(neighbor).inc_degree( -lrg1.compute_degree(lrgs(neighbor)) );
   // lr2 is now called (coalesced into) lr1.
   // Remove lr2 from the IFG.
   IndexSetIterator two(n_lr2);
   LRG &lrg2 = lrgs(lr2);
   while ((neighbor = two.next()) != 0)
     if( _phc._ifg->neighbors(neighbor)->remove(lr2) )
       lrgs(neighbor).inc_degree( -lrg2.compute_degree(lrgs(neighbor)) );
   // Some neighbors of intermediate copies now interfere with the
   // combined live range.
   IndexSetIterator three(&_ulr);
   while ((neighbor = three.next()) != 0)
     if( _phc._ifg->neighbors(neighbor)->insert(lr1) )
       lrgs(neighbor).inc_degree( lrg1.compute_degree(lrgs(neighbor)) );
 }
 //------------------------------record_bias------------------------------------
 static void record_bias( const PhaseIFG *ifg, int lr1, int lr2 ) {
   // Tag copy bias here
   if( !ifg->lrgs(lr1)._copy_bias )
     ifg->lrgs(lr1)._copy_bias = lr2;
   if( !ifg->lrgs(lr2)._copy_bias )
     ifg->lrgs(lr2)._copy_bias = lr1;
 }
 //------------------------------copy_copy--------------------------------------
 // See if I can coalesce a series of multiple copies together.  I need the
 // final dest copy and the original src copy.  They can be the same Node.
 // Compute the compatible register masks.
 bool PhaseConservativeCoalesce::copy_copy( Node *dst_copy, Node *src_copy, Block *b, uint bindex ) {
   if( !dst_copy->is_SpillCopy() ) return false;
   if( !src_copy->is_SpillCopy() ) return false;
   Node *src_def = src_copy->in(src_copy->is_Copy());
   uint lr1 = _phc.Find(dst_copy);
   uint lr2 = _phc.Find(src_def );
   // Same live ranges already?
   if( lr1 == lr2 ) return false;
   // Interfere?
   if( _phc._ifg->test_edge_sq( lr1, lr2 ) ) return false;
   // Not an oop->int cast; oop->oop, int->int, AND int->oop are OK.
   if( !lrgs(lr1)._is_oop && lrgs(lr2)._is_oop ) // not an oop->int cast
     return false;
   // Coalescing between an aligned live range and a mis-aligned live range?
   // No, no!  Alignment changes how we count degree.
   if( lrgs(lr1)._fat_proj != lrgs(lr2)._fat_proj )
     return false;
   // Sort; use smaller live-range number
   Node *lr1_node = dst_copy;
   Node *lr2_node = src_def;
   if( lr1 > lr2 ) {
     uint tmp = lr1; lr1 = lr2; lr2 = tmp;
     lr1_node = src_def;  lr2_node = dst_copy;
   }
   // Check for compatibility of the 2 live ranges by
   // intersecting their allowed register sets.
   RegMask rm = lrgs(lr1).mask();
   rm.AND(lrgs(lr2).mask());
   // Number of bits free
   uint rm_size = rm.Size();
   // If we can use any stack slot, then effective size is infinite
   if( rm.is_AllStack() ) rm_size += 1000000;
   // Incompatible masks, no way to coalesce
   if( rm_size == 0 ) return false;
   // Another early bail-out test is when we are double-coalescing and the
   // 2 copies are separated by some control flow.
   if( dst_copy != src_copy ) {
     Block *src_b = _phc._cfg._bbs[src_copy->_idx];
     Block *b2 = b;
     while( b2 != src_b ) {
       if( b2->num_preds() > 2 ){// Found merge-point
         _phc._lost_opp_cflow_coalesce++;
         // extra record_bias commented out because Chris believes it is not
         // productive.  Since we can record only 1 bias, we want to choose one
         // that stands a chance of working and this one probably does not.
         //record_bias( _phc._lrgs, lr1, lr2 );
         return false;           // To hard to find all interferences
       }
       b2 = _phc._cfg._bbs[b2->pred(1)->_idx];
     }
   }
   // Union the two interference sets together into '_ulr'
   uint reg_degree = _ulr.lrg_union( lr1, lr2, rm_size, _phc._ifg, rm );
   if( reg_degree >= rm_size ) {
     record_bias( _phc._ifg, lr1, lr2 );
     return false;
   }
   // Now I need to compute all the interferences between dst_copy and
   // src_copy.  I'm not willing visit the entire interference graph, so
   // I limit my search to things in dst_copy's block or in a straight
   // line of previous blocks.  I give up at merge points or when I get
   // more interferences than my degree.  I can stop when I find src_copy.
   if( dst_copy != src_copy ) {
     reg_degree = compute_separating_interferences(dst_copy, src_copy, b, bindex, rm, rm_size, reg_degree, lr1, lr2 );
     if( reg_degree == max_juint ) {
       record_bias( _phc._ifg, lr1, lr2 );
       return false;
     }
   } // End of if dst_copy & src_copy are different
   // ---- THE COMBINED LRG IS COLORABLE ----
   // YEAH - Now coalesce this copy away
   assert( lrgs(lr1).num_regs() == lrgs(lr2).num_regs(),   "" );
   IndexSet *n_lr1 = _phc._ifg->neighbors(lr1);
   IndexSet *n_lr2 = _phc._ifg->neighbors(lr2);
   // Update the interference graph
   update_ifg(lr1, lr2, n_lr1, n_lr2);
   _ulr.remove(lr1);
   // Uncomment the following code to trace Coalescing in great detail.
   //
   //if (false) {
   //  tty->cr();
   //  tty->print_cr("#######################################");
   //  tty->print_cr("union %d and %d", lr1, lr2);
   //  n_lr1->dump();
   //  n_lr2->dump();
   //  tty->print_cr("resulting set is");
   //  _ulr.dump();
   //}
   // Replace n_lr1 with the new combined live range.  _ulr will use
   // n_lr1's old memory on the next iteration.  n_lr2 is cleared to
   // send its internal memory to the free list.
   _ulr.swap(n_lr1);
   _ulr.clear();
   n_lr2->clear();
   lrgs(lr1).set_degree( _phc._ifg->effective_degree(lr1) );
   lrgs(lr2).set_degree( 0 );
   // Join live ranges.  Merge larger into smaller.  Union lr2 into lr1 in the
   // union-find tree
   union_helper( lr1_node, lr2_node, lr1, lr2, src_def, dst_copy, src_copy, b, bindex );
   // Combine register restrictions
   lrgs(lr1).set_mask(rm);
   lrgs(lr1).compute_set_mask_size();
   lrgs(lr1)._cost += lrgs(lr2)._cost;
   lrgs(lr1)._area += lrgs(lr2)._area;
   // While its uncommon to successfully coalesce live ranges that started out
   // being not-lo-degree, it can happen.  In any case the combined coalesced
   // live range better Simplify nicely.
   lrgs(lr1)._was_lo = 1;
   // kinda expensive to do all the time
   //tty->print_cr("warning: slow verify happening");
   //_phc._ifg->verify( &_phc );
   return true;
 }
 //------------------------------coalesce---------------------------------------
 // Conservative (but pessimistic) copy coalescing of a single block
 void PhaseConservativeCoalesce::coalesce( Block *b ) {
   // Bail out on infrequent blocks
   if( b->is_uncommon(_phc._cfg._bbs) )
     return;
   // Check this block for copies.
   for( uint i = 1; i<b->end_idx(); i++ ) {
     // Check for actual copies on inputs.  Coalesce a copy into its
     // input if use and copy's input are compatible.
     Node *copy1 = b->_nodes[i];
     uint idx1 = copy1->is_Copy();
     if( !idx1 ) continue;       // Not a copy
     if( copy_copy(copy1,copy1,b,i) ) {
       i--;                      // Retry, same location in block
       PhaseChaitin::_conserv_coalesce++;  // Collect stats on success
       continue;
     }
     /* do not attempt pairs.  About 1/2 of all pairs can be removed by
        post-alloc.  The other set are too few to bother.
     Node *copy2 = copy1->in(idx1);
     uint idx2 = copy2->is_Copy();
     if( !idx2 ) continue;
     if( copy_copy(copy1,copy2,b,i) ) {
       i--;                      // Retry, same location in block
       PhaseChaitin::_conserv_coalesce_pair++; // Collect stats on success
       continue;
     }
     */
   }
 }

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/opto/coalesce.cpp@98cb887364d3 (annotated)

src/share/vm/opto/coalesce.cpp