[Bug tree-optimization/55191] [4.8 Regression] ICE in compute_antic at tree-ssa-pre.c:2511

[steven at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55191



--- Comment #5 from Steven Bosscher <steven at gcc dot gnu.org> 2012-11-05 
20:23:55 UTC ---

Ugliness in cfganal.c, it depends on the block ordering for the DFS it

performs on the reverse CFG. The following patch should fix the issue.



Index: cfganal.c

===================================================================

--- cfganal.c    (revision 193181)

+++ cfganal.c    (working copy)

@@ -452,6 +452,7 @@ void

 connect_infinite_loops_to_exit (void)

 {

   basic_block unvisited_block = EXIT_BLOCK_PTR;

+  basic_block deadend_block;

   struct depth_first_search_dsS dfs_ds;



   /* Perform depth-first search in the reverse graph to find nodes

@@ -467,8 +468,9 @@ connect_infinite_loops_to_exit (void)

       if (!unvisited_block)

     break;



-      make_edge (unvisited_block, EXIT_BLOCK_PTR, EDGE_FAKE);

-      flow_dfs_compute_reverse_add_bb (&dfs_ds, unvisited_block);

+      deadend_block = dfs_find_deadend (unvisited_block);

+      make_edge (deadend_block, EXIT_BLOCK_PTR, EDGE_FAKE);

+      flow_dfs_compute_reverse_add_bb (&dfs_ds, deadend_block);

     }



   flow_dfs_compute_reverse_finish (&dfs_ds);

@@ -958,7 +960,7 @@ flow_dfs_compute_reverse_execute (depth_

   /* Determine if there are unvisited basic blocks.  */

   FOR_BB_BETWEEN (bb, last_unvisited, NULL, prev_bb)

     if (!bitmap_bit_p (data->visited_blocks, bb->index))

-      return dfs_find_deadend (bb);

+      return bb;



   return NULL;

 }