xo-gc: refactor: move _deep_move_root() to GCObjectStore

src/gc/GCObjectStore.cpp

@@ -626,9 +626,54 @@ namespace xo {
         }
 
         void *
-        GCObjectStore::deep_move_interior(DX1Collector * gc,
-                                          void * from_src,
-                                          Generation upto)
+        GCObjectStore::_deep_move_root(DX1Collector * gc,
+                                       obj<AGCObject> from_src,
+                                       Generation upto)
+        {
+            // NOTE:
+            // Some roots are non-gc-owned nodes.
+            // GC must still visit immediate children of these nodes
+            // to move gc-owned children.
+            // This implements virtual root node feature,
+            // intended to mitigate mutation log churn.
+
+            scope log(XO_DEBUG(config_.debug_flag_));
+
+            if (!from_src)
+                return nullptr;
+
+            bool src_in_from_space = this->contains(role::from_space(),
+                                                    from_src.data());
+
+            if (src_in_from_space) {
+                return this->_deep_move_gc_owned(gc, from_src.data(), upto);
+            } else {
+                // we aren't moving from_src, it's not gc-owned.
+                // However weare moving all its gc-owned children
+
+                auto gc_obj = gc->ref<ACollector>();
+
+                GCMoveCheckpoint gray_lo_v
+                    = this->snap_move_checkpoint(upto);
+
+                from_src.forward_children(gc_obj);
+
+                // For each generation g:
+                //   traverse objects newer than gray_lo_v[g], to make sure children
+                //   are forwarded.  Fixpoint reached when gray_lo_v[g] doesn't change.
+                //   Remember that forwarding may promote objects to older generation,
+                //   so need multiple passes
+                //
+                this->_forward_children_until_fixpoint(gc, upto, gray_lo_v);
+
+                return from_src.data();
+            }
+        }
+
+        void *
+        GCObjectStore::_deep_move_interior(DX1Collector * gc,
+                                           void * from_src,
+                                           Generation upto)
         {
             scope log(XO_DEBUG(config_.debug_flag_));