177       if (matrix->is_connected(from_idx, to_idx)) {
 178         num_incoming++;
 179       }
 180     }
 181     if (num_incoming < ShenandoahPartialInboundThreshold) {
 182       collection_set->add_region(region);
 183       _heap->set_region_in_collection_set(to_idx, true);
 184     }
 185   }
 186   // Second pass: find all root regions.
 187   uint num_cset = collection_set->count();
 188   for (uint idx = 0; idx < num_cset; idx++) {
 189     ShenandoahHeapRegion* region = collection_set->get(idx);
 190     uint to_idx = region->region_number();
 191     assert(! region->is_humongous() && ! region->is_empty() && ! region->is_pinned(), "sanity");
 192     assert(_heap->region_in_collection_set(to_idx), "more sanity");
 193     for (uint from_idx = 0; from_idx < num_regions; from_idx++) {
 194       if (matrix->is_connected(from_idx, to_idx)) {
 195         ShenandoahHeapRegion* r = regions->get(from_idx);
 196         if (! r->is_root() && ! _heap->region_in_collection_set(from_idx)) {
 197           // TODO: Implement support for humongous roots:
 198           // - quick impl: rewind to the head of the humongous object and use that
 199           // - better impl: support scanning of humongous continuation regions
 200           //   and potentially avoid scanning the whole obj
 201           guarantee(! r->is_humongous_continuation(), "unimplemented");
 202           _root_regions->add_region(r);
 203           r->set_root(true);
 204         }
 205       }
 206     }
 207   }
 208   // Final pass: free regions.
 209   for (uint to_idx = 0; to_idx < num_regions; to_idx++) {
 210     ShenandoahHeapRegion* region = regions->get(to_idx);
 211     if (! region->is_humongous() &&
 212         ! region->is_pinned() &&
 213         ! region->is_root() &&
 214         ! _heap->in_collection_set(region)) {
 215 
 216       free_set->add_region(region);
 217     }
 218   }
 219   log_debug(gc, ergo)("got "SIZE_FORMAT" cset regions", collection_set->count());
 220   log_debug(gc, ergo)("got "SIZE_FORMAT" root regions", _root_regions->count());
 221 }

 177       if (matrix->is_connected(from_idx, to_idx)) {
 178         num_incoming++;
 179       }
 180     }
 181     if (num_incoming < ShenandoahPartialInboundThreshold) {
 182       collection_set->add_region(region);
 183       _heap->set_region_in_collection_set(to_idx, true);
 184     }
 185   }
 186   // Second pass: find all root regions.
 187   uint num_cset = collection_set->count();
 188   for (uint idx = 0; idx < num_cset; idx++) {
 189     ShenandoahHeapRegion* region = collection_set->get(idx);
 190     uint to_idx = region->region_number();
 191     assert(! region->is_humongous() && ! region->is_empty() && ! region->is_pinned(), "sanity");
 192     assert(_heap->region_in_collection_set(to_idx), "more sanity");
 193     for (uint from_idx = 0; from_idx < num_regions; from_idx++) {
 194       if (matrix->is_connected(from_idx, to_idx)) {
 195         ShenandoahHeapRegion* r = regions->get(from_idx);
 196         if (! r->is_root() && ! _heap->region_in_collection_set(from_idx)) {





 197           _root_regions->add_region(r);
 198           r->set_root(true);
 199         }
 200       }
 201     }
 202   }
 203   // Final pass: free regions.
 204   for (uint to_idx = 0; to_idx < num_regions; to_idx++) {
 205     ShenandoahHeapRegion* region = regions->get(to_idx);
 206     if (! region->is_humongous() &&
 207         ! region->is_pinned() &&
 208         ! region->is_root() &&
 209         ! _heap->in_collection_set(region)) {
 210 
 211       free_set->add_region(region);
 212     }
 213   }
 214   log_debug(gc, ergo)("got "SIZE_FORMAT" cset regions", collection_set->count());
 215   log_debug(gc, ergo)("got "SIZE_FORMAT" root regions", _root_regions->count());
 216 }