[Bug tree-optimization/54742] Switch elimination in FSM loop

[joey.ye at arm dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54742

--- Comment #3 from Joey Ye <joey.ye at arm dot com> 2012-10-10 07:37:15 UTC ---
Current jump-threading is too conservative to thread this case. Following
limits are what I observed by reading code:
1. It only thread around blocks that
  * Single entry
  * Multiple exit
  * No PHI nodes
  Even the simple case as forwarding block is excluded.

2. It only thread a block once. For blocks with more than one entries, it is
possible to be threaded more than one time too.