xref: /openjdk10/hotspot/src/share/vm/opto/live.cpp

/*
 * Copyright 1997-2005 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/_live.cpp.incl"



//=============================================================================
//------------------------------PhaseLive--------------------------------------
// Compute live-in/live-out.  We use a totally incremental algorithm.  The LIVE
// problem is monotonic.  The steady-state solution looks like this: pull a
// block from the worklist.  It has a set of delta's - values which are newly
// live-in from the block.  Push these to the live-out sets of all predecessor
// blocks.  At each predecessor, the new live-out values are ANDed with what is
// already live-out (extra stuff is added to the live-out sets).  Then the
// remaining new live-out values are ANDed with what is locally defined.
// Leftover bits become the new live-in for the predecessor block, and the pred
// block is put on the worklist.
//   The locally live-in stuff is computed once and added to predecessor
// live-out sets.  This seperate compilation is done in the outer loop below.
PhaseLive::PhaseLive( const PhaseCFG &cfg, LRG_List &names, Arena *arena ) : Phase(LIVE), _cfg(cfg), _names(names), _arena(arena), _live(0) {
}

void PhaseLive::compute(uint maxlrg) {
  _maxlrg   = maxlrg;
  _worklist = new (_arena) Block_List();

  // Init the sparse live arrays.  This data is live on exit from here!
  // The _live info is the live-out info.
  _live = (IndexSet*)_arena->Amalloc(sizeof(IndexSet)*_cfg._num_blocks);
  uint i;
  for( i=0; i<_cfg._num_blocks; i++ ) {
    _live[i].initialize(_maxlrg);
  }

  // Init the sparse arrays for delta-sets.
  ResourceMark rm;              // Nuke temp storage on exit

  // Does the memory used by _defs and _deltas get reclaimed?  Does it matter?  TT

  // Array of values defined locally in blocks
  _defs = NEW_RESOURCE_ARRAY(IndexSet,_cfg._num_blocks);
  for( i=0; i<_cfg._num_blocks; i++ ) {
    _defs[i].initialize(_maxlrg);
  }

  // Array of delta-set pointers, indexed by block pre_order-1.
  _deltas = NEW_RESOURCE_ARRAY(IndexSet*,_cfg._num_blocks);
  memset( _deltas, 0, sizeof(IndexSet*)* _cfg._num_blocks);

  _free_IndexSet = NULL;

  // Blocks having done pass-1
  VectorSet first_pass(Thread::current()->resource_area());

  // Outer loop: must compute local live-in sets and push into predecessors.
  uint iters = _cfg._num_blocks;        // stat counters
  for( uint j=_cfg._num_blocks; j>0; j-- ) {
    Block *b = _cfg._blocks[j-1];

    // Compute the local live-in set.  Start with any new live-out bits.
    IndexSet *use = getset( b );
    IndexSet *def = &_defs[b->_pre_order-1];
    DEBUG_ONLY(IndexSet *def_outside = getfreeset();)
    uint i;
    for( i=b->_nodes.size(); i>1; i-- ) {
      Node *n = b->_nodes[i-1];
      if( n->is_Phi() ) break;

      uint r = _names[n->_idx];
      assert(!def_outside->member(r), "Use of external LRG overlaps the same LRG defined in this block");
      def->insert( r );
      use->remove( r );
      uint cnt = n->req();
      for( uint k=1; k<cnt; k++ ) {
        Node *nk = n->in(k);
        uint nkidx = nk->_idx;
        if( _cfg._bbs[nkidx] != b ) {
          uint u = _names[nkidx];
          use->insert( u );
          DEBUG_ONLY(def_outside->insert( u );)
        }
      }
    }
#ifdef ASSERT
    def_outside->set_next(_free_IndexSet);
    _free_IndexSet = def_outside;     // Drop onto free list
#endif
    // Remove anything defined by Phis and the block start instruction
    for( uint k=i; k>0; k-- ) {
      uint r = _names[b->_nodes[k-1]->_idx];
      def->insert( r );
      use->remove( r );
    }

    // Push these live-in things to predecessors
    for( uint l=1; l<b->num_preds(); l++ ) {
      Block *p = _cfg._bbs[b->pred(l)->_idx];
      add_liveout( p, use, first_pass );

      // PhiNode uses go in the live-out set of prior blocks.
      for( uint k=i; k>0; k-- )
        add_liveout( p, _names[b->_nodes[k-1]->in(l)->_idx], first_pass );
    }
    freeset( b );
    first_pass.set(b->_pre_order);

    // Inner loop: blocks that picked up new live-out values to be propagated
    while( _worklist->size() ) {
        // !!!!!
// #ifdef ASSERT
      iters++;
// #endif
      Block *b = _worklist->pop();
      IndexSet *delta = getset(b);
      assert( delta->count(), "missing delta set" );

      // Add new-live-in to predecessors live-out sets
      for( uint l=1; l<b->num_preds(); l++ )
        add_liveout( _cfg._bbs[b->pred(l)->_idx], delta, first_pass );

      freeset(b);
    } // End of while-worklist-not-empty

  } // End of for-all-blocks-outer-loop

  // We explicitly clear all of the IndexSets which we are about to release.
  // This allows us to recycle their internal memory into IndexSet's free list.

  for( i=0; i<_cfg._num_blocks; i++ ) {
    _defs[i].clear();
    if (_deltas[i]) {
      // Is this always true?
      _deltas[i]->clear();
    }
  }
  IndexSet *free = _free_IndexSet;
  while (free != NULL) {
    IndexSet *temp = free;
    free = free->next();
    temp->clear();
  }

}

//------------------------------stats------------------------------------------
#ifndef PRODUCT
void PhaseLive::stats(uint iters) const {
}
#endif

//------------------------------getset-----------------------------------------
// Get an IndexSet for a block.  Return existing one, if any.  Make a new
// empty one if a prior one does not exist.
IndexSet *PhaseLive::getset( Block *p ) {
  IndexSet *delta = _deltas[p->_pre_order-1];
  if( !delta )                  // Not on worklist?
    // Get a free set; flag as being on worklist
    delta = _deltas[p->_pre_order-1] = getfreeset();
  return delta;                 // Return set of new live-out items
}

//------------------------------getfreeset-------------------------------------
// Pull from free list, or allocate.  Internal allocation on the returned set
// is always from thread local storage.
IndexSet *PhaseLive::getfreeset( ) {
  IndexSet *f = _free_IndexSet;
  if( !f ) {
    f = new IndexSet;
//    f->set_arena(Thread::current()->resource_area());
    f->initialize(_maxlrg, Thread::current()->resource_area());
  } else {
    // Pull from free list
    _free_IndexSet = f->next();
  //f->_cnt = 0;                        // Reset to empty
//    f->set_arena(Thread::current()->resource_area());
    f->initialize(_maxlrg, Thread::current()->resource_area());
  }
  return f;
}

//------------------------------freeset----------------------------------------
// Free an IndexSet from a block.
void PhaseLive::freeset( const Block *p ) {
  IndexSet *f = _deltas[p->_pre_order-1];
  f->set_next(_free_IndexSet);
  _free_IndexSet = f;           // Drop onto free list
  _deltas[p->_pre_order-1] = NULL;
}

//------------------------------add_liveout------------------------------------
// Add a live-out value to a given blocks live-out set.  If it is new, then
// also add it to the delta set and stick the block on the worklist.
void PhaseLive::add_liveout( Block *p, uint r, VectorSet &first_pass ) {
  IndexSet *live = &_live[p->_pre_order-1];
  if( live->insert(r) ) {       // If actually inserted...
    // We extended the live-out set.  See if the value is generated locally.
    // If it is not, then we must extend the live-in set.
    if( !_defs[p->_pre_order-1].member( r ) ) {
      if( !_deltas[p->_pre_order-1] && // Not on worklist?
          first_pass.test(p->_pre_order) )
        _worklist->push(p);     // Actually go on worklist if already 1st pass
      getset(p)->insert(r);
    }
  }
}


//------------------------------add_liveout------------------------------------
// Add a vector of live-out values to a given blocks live-out set.
void PhaseLive::add_liveout( Block *p, IndexSet *lo, VectorSet &first_pass ) {
  IndexSet *live = &_live[p->_pre_order-1];
  IndexSet *defs = &_defs[p->_pre_order-1];
  IndexSet *on_worklist = _deltas[p->_pre_order-1];
  IndexSet *delta = on_worklist ? on_worklist : getfreeset();

  IndexSetIterator elements(lo);
  uint r;
  while ((r = elements.next()) != 0) {
    if( live->insert(r) &&      // If actually inserted...
        !defs->member( r ) )    // and not defined locally
      delta->insert(r);         // Then add to live-in set
  }

  if( delta->count() ) {                // If actually added things
    _deltas[p->_pre_order-1] = delta; // Flag as on worklist now
    if( !on_worklist &&         // Not on worklist?
        first_pass.test(p->_pre_order) )
      _worklist->push(p);       // Actually go on worklist if already 1st pass
  } else {                      // Nothing there; just free it
    delta->set_next(_free_IndexSet);
    _free_IndexSet = delta;     // Drop onto free list
  }
}

#ifndef PRODUCT
//------------------------------dump-------------------------------------------
// Dump the live-out set for a block
void PhaseLive::dump( const Block *b ) const {
  tty->print("Block %d: ",b->_pre_order);
  tty->print("LiveOut: ");  _live[b->_pre_order-1].dump();
  uint cnt = b->_nodes.size();
  for( uint i=0; i<cnt; i++ ) {
    tty->print("L%d/", _names[b->_nodes[i]->_idx] );
    b->_nodes[i]->dump();
  }
  tty->print("\n");
}

//------------------------------verify_base_ptrs-------------------------------
// Verify that base pointers and derived pointers are still sane.
// Basically, if a derived pointer is live at a safepoint, then its
// base pointer must be live also.
void PhaseChaitin::verify_base_ptrs( ResourceArea *a ) const {
  for( uint i = 0; i < _cfg._num_blocks; i++ ) {
    Block *b = _cfg._blocks[i];
    for( uint j = b->end_idx() + 1; j > 1; j-- ) {
      Node *n = b->_nodes[j-1];
      if( n->is_Phi() ) break;
      // Found a safepoint?
      if( n->is_MachSafePoint() ) {
        MachSafePointNode *sfpt = n->as_MachSafePoint();
        JVMState* jvms = sfpt->jvms();
        if (jvms != NULL) {
          // Now scan for a live derived pointer
          if (jvms->oopoff() < sfpt->req()) {
            // Check each derived/base pair
            for (uint idx = jvms->oopoff(); idx < sfpt->req(); idx += 2) {
              Node *check = sfpt->in(idx);
              uint j = 0;
              // search upwards through spills and spill phis for AddP
              while(true) {
                if( !check ) break;
                int idx = check->is_Copy();
                if( idx ) {
                  check = check->in(idx);
                } else if( check->is_Phi() && check->_idx >= _oldphi ) {
                  check = check->in(1);
                } else
                  break;
                j++;
                assert(j < 100000,"Derived pointer checking in infinite loop");
              } // End while
              assert(check->is_Mach() && check->as_Mach()->ideal_Opcode() == Op_AddP,"Bad derived pointer")
            }
          } // End of check for derived pointers
        } // End of Kcheck for debug info
      } // End of if found a safepoint
    } // End of forall instructions in block
  } // End of forall blocks
}
#endif