[Bug tree-optimization/59249] if-conversion doesn't handle basic-blocks with only critical predecessor edges

[bmei at broadcom dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59249

--- Comment #3 from Bingfeng Mei <bmei at broadcom dot com> ---
Richard, I am not sure I understand about how to split edge.

     BB4 
     / \
    /   \
  BB5    |
   |\    |
   | \   |
   |  \  |
   |   BB6
   |   /
   |  /
   BB7


Compiler (HEAD) complains "only critical predecessors of BB6" (its predcessor
BB5 has more than one successor). Do you suggest to split edge between BB5 &
BB6 and insert an empty BB? 

In the email thread, you blame poor implementation of tree-level if-conversion.
But RTL-level CE passes cannot handle that too.