[Bug c/53999] New: failure in selective scheduler

[aturjan at yahoo dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53999

             Bug #: 53999
           Summary: failure in selective scheduler
    Classification: Unclassified
           Product: gcc
           Version: 4.5.0
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: c
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: aturjan@yahoo.com


I get an assert failure during a run of the selective scheduler.
The problem is due to the implementation of maybe_tidy_empty_bb.
Inside of it I see the following piece of code:

 /* If it is possible - merge BB with its predecessor.  */
  if (can_merge_blocks_p (bb->prev_bb, bb))
    sel_merge_blocks (bb->prev_bb, bb);


During my compiler run I reach the situation in which bb->prev_bb is not in the
scheduling scope BUT can_merge_blocks_p (bb->prev_bb, bb) returns true.

As a consequence inside sel_remove_empty_bb I hit on the following assert:
gcc_assert (in_current_region_p (merge_bb));

The backtrace from the assert is: 
#0  move_bb_info 
#1 sel_remove_empty_bb
#2  sel_merge_blocks
#3  maybe_tidy_empty_bb 

Perhaps one way to solve the problem is to replace:
if (can_merge_blocks_p (bb->prev_bb, bb))
with
if (can_merge_blocks_p (bb->prev_bb, bb) && in_current_region_p (bb->prev_bb))

Can somebody comment on this?