src/hotspot/share/opto/split_if.cpp

rev 53952 : 8219448: split-if update_uses accesses stale idom data
Reviewed-by:

*** 521,531 ****
        new_true = ifpx;
      }
    }
    _igvn.remove_dead_node(new_iff);
    // Lazy replace IDOM info with the region's dominator
!   lazy_replace( iff, region_dom );
  
    // Now make the original merge point go dead, by handling all its uses.
    small_cache region_cache;
    // Preload some control flow in region-cache
    region_cache.lru_insert( new_false, new_false );
--- 521,533 ----
        new_true = ifpx;
      }
    }
    _igvn.remove_dead_node(new_iff);
    // Lazy replace IDOM info with the region's dominator
!   lazy_replace(iff, region_dom);
!   lazy_update(region, region_dom); // idom must be update before handle_uses, the replacement is done after
!   region->set_req(0, NULL);        // Break the self-cycle. Required for lazy_update to work on region
  
    // Now make the original merge point go dead, by handling all its uses.
    small_cache region_cache;
    // Preload some control flow in region-cache
    region_cache.lru_insert( new_false, new_false );
*** 564,575 ****
      // calling get_ctrl calling get_ctrl_no_update looking for dead
      // regions).  So roll back the DUIterator innards.
      --k;
    } // End of while merge point has phis
  
!   assert(region->outcnt() == 1, "Only self reference should remain"); // Just Self on the Region
!   region->set_req(0, NULL);       // Break the self-cycle
  
    // Any leftover bits in the splitting block must not have depended on local
    // Phi inputs (these have already been split-up).  Hence it's safe to hoist
    // these guys to the dominating point.
    lazy_replace( region, region_dom );
--- 566,576 ----
      // calling get_ctrl calling get_ctrl_no_update looking for dead
      // regions).  So roll back the DUIterator innards.
      --k;
    } // End of while merge point has phis
  
!   assert(region->outcnt() == 0, "Should be empty now");
  
    // Any leftover bits in the splitting block must not have depended on local
    // Phi inputs (these have already been split-up).  Hence it's safe to hoist
    // these guys to the dominating point.
    lazy_replace( region, region_dom );