http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54520
Richard Guenther <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |ASSIGNED Last reconfirmed| |2012-09-10 AssignedTo|unassigned at gcc dot |rguenth at gcc dot gnu.org |gnu.org | Ever Confirmed|0 |1 --- Comment #3 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-09-10 10:51:23 UTC --- The (latent) bug is that when threading over a subloop /* Remove the new pre-header blocks from our loop. */ bblocks = XCNEWVEC (basic_block, loop->num_nodes); nblocks = dfs_enumerate_from (header, 0, def_split_header_continue_p, bblocks, loop->num_nodes, tgt_bb); for (i = 0; i < nblocks; i++) { remove_bb_from_loops (bblocks[i]); add_bb_to_loop (bblocks[i], loop_outer (loop)); } free (bblocks); does not remove properly all blocks from the loop. oldheader | \ | subloop | | | exit block | / new header | ... because the DFS walk stops at 'subloop'...