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Java example source code file (live.cpp)

This example Java source code file (live.cpp) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

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Java - Java tags/keywords

actually, assert, bad, block, drop, end, indexset, node, not, null, product, resourcearea, vectorset

The live.cpp Java example source code

/*
 * Copyright (c) 1997, 2013, 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 "memory/allocation.inline.hpp"
#include "opto/callnode.hpp"
#include "opto/chaitin.hpp"
#include "opto/live.hpp"
#include "opto/machnode.hpp"


// 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 separate compilation is done in the outer loop below.
PhaseLive::PhaseLive( const PhaseCFG &cfg, const 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.number_of_blocks());
  uint i;
  for (i = 0; i < _cfg.number_of_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.number_of_blocks());
  for (i = 0; i < _cfg.number_of_blocks(); i++) {
    _defs[i].initialize(_maxlrg);
  }

  // Array of delta-set pointers, indexed by block pre_order-1.
  _deltas = NEW_RESOURCE_ARRAY(IndexSet*,_cfg.number_of_blocks());
  memset( _deltas, 0, sizeof(IndexSet*)* _cfg.number_of_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.
  for (uint j = _cfg.number_of_blocks(); j > 0; j--) {
    Block* block = _cfg.get_block(j - 1);

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

      uint r = _names.at(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.get_block_for_node(nk) != block) {
          uint u = _names.at(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.at(block->get_node(k - 1)->_idx);
      def->insert(r);
      use->remove(r);
    }

    // Push these live-in things to predecessors
    for (uint l = 1; l < block->num_preds(); l++) {
      Block* p = _cfg.get_block_for_node(block->pred(l));
      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.at(block->get_node(k-1)->in(l)->_idx), first_pass);
      }
    }
    freeset(block);
    first_pass.set(block->_pre_order);

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

      // Add new-live-in to predecessors live-out sets
      for (uint l = 1; l < block->num_preds(); l++) {
        Block* predecessor = _cfg.get_block_for_node(block->pred(l));
        add_liveout(predecessor, delta, first_pass);
      }

      freeset(block);
    } // 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.number_of_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();
  }

}

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

// 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
}

// 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;
}

// 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 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 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 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->number_of_nodes();
  for( uint i=0; i<cnt; i++ ) {
    tty->print("L%d/", _names.at(b->get_node(i)->_idx));
    b->get_node(i)->dump();
  }
  tty->print("\n");
}

// Verify that base pointers and derived pointers are still sane.
void PhaseChaitin::verify_base_ptrs( ResourceArea *a ) const {
#ifdef ASSERT
  Unique_Node_List worklist(a);
  for (uint i = 0; i < _cfg.number_of_blocks(); i++) {
    Block* block = _cfg.get_block(i);
    for (uint j = block->end_idx() + 1; j > 1; j--) {
      Node* n = block->get_node(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++) {
              Node *check = sfpt->in(idx);
              bool is_derived = ((idx - jvms->oopoff()) & 1) == 0;
              // search upwards through spills and spill phis for AddP
              worklist.clear();
              worklist.push(check);
              uint k = 0;
              while( k < worklist.size() ) {
                check = worklist.at(k);
                assert(check,"Bad base or derived pointer");
                // See PhaseChaitin::find_base_for_derived() for all cases.
                int isc = check->is_Copy();
                if( isc ) {
                  worklist.push(check->in(isc));
                } else if( check->is_Phi() ) {
                  for (uint m = 1; m < check->req(); m++)
                    worklist.push(check->in(m));
                } else if( check->is_Con() ) {
                  if (is_derived) {
                    // Derived is NULL+offset
                    assert(!is_derived || check->bottom_type()->is_ptr()->ptr() == TypePtr::Null,"Bad derived pointer");
                  } else {
                    assert(check->bottom_type()->is_ptr()->_offset == 0,"Bad base pointer");
                    // Base either ConP(NULL) or loadConP
                    if (check->is_Mach()) {
                      assert(check->as_Mach()->ideal_Opcode() == Op_ConP,"Bad base pointer");
                    } else {
                      assert(check->Opcode() == Op_ConP &&
                             check->bottom_type()->is_ptr()->ptr() == TypePtr::Null,"Bad base pointer");
                    }
                  }
                } else if( check->bottom_type()->is_ptr()->_offset == 0 ) {
                  if(check->is_Proj() || check->is_Mach() &&
                     (check->as_Mach()->ideal_Opcode() == Op_CreateEx ||
                      check->as_Mach()->ideal_Opcode() == Op_ThreadLocal ||
                      check->as_Mach()->ideal_Opcode() == Op_CMoveP ||
                      check->as_Mach()->ideal_Opcode() == Op_CheckCastPP ||
#ifdef _LP64
                      UseCompressedOops && check->as_Mach()->ideal_Opcode() == Op_CastPP ||
                      UseCompressedOops && check->as_Mach()->ideal_Opcode() == Op_DecodeN ||
                      UseCompressedClassPointers && check->as_Mach()->ideal_Opcode() == Op_DecodeNKlass ||
#endif
                      check->as_Mach()->ideal_Opcode() == Op_LoadP ||
                      check->as_Mach()->ideal_Opcode() == Op_LoadKlass)) {
                    // Valid nodes
                  } else {
                    check->dump();
                    assert(false,"Bad base or derived pointer");
                  }
                } else {
                  assert(is_derived,"Bad base pointer");
                  assert(check->is_Mach() && check->as_Mach()->ideal_Opcode() == Op_AddP,"Bad derived pointer");
                }
                k++;
                assert(k < 100000,"Derived pointer checking in infinite loop");
              } // End while
            }
          } // 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
}

// Verify that graphs and base pointers are still sane.
void PhaseChaitin::verify( ResourceArea *a, bool verify_ifg ) const {
#ifdef ASSERT
  if( VerifyOpto || VerifyRegisterAllocator ) {
    _cfg.verify();
    verify_base_ptrs(a);
    if(verify_ifg)
      _ifg->verify(this);
  }
#endif
}

#endif

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