http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54838
--- Comment #15 from Marek Polacek <mpolacek at gcc dot gnu.org> 2012-12-14
16:12:48 UTC ---
The issue here is that we have a loop with header and two latches, and via
delete_basic_block we delete both latches (and all edges of those two latches).
So, we don't have a loop anymore, but the header has still loop_depth > 0,
merge_latch_edges of course ICEs on it, because there's an assert:
gcc_assert (latches.length () > 0);
but the latches are already gone. I think that in this case we want to just
set the loop->header to NULL (or cancel_loop_tree, or unloop, or...). What I
have in mind is basically something like:
--- a/gcc/cfghooks.c
+++ b/gcc/cfghooks.c
@@ -552,6 +552,23 @@ delete_basic_block (basic_block bb)
loops_state_set (LOOPS_NEED_FIXUP);
}
+ if (loop->header
+ && bb->loop_father != current_loops->tree_root)
+ {
+ edge_iterator ei;
+ edge e;
+ unsigned n_back_edges = 0;
+
+ FOR_EACH_EDGE (e, ei, loop->header->preds)
+ if (e->flags & EDGE_DFS_BACK)
+ n_back_edges++;
+
+ if (n_back_edges == 0)
+ {
+ loop->header = NULL;
+ loops_state_set (LOOPS_NEED_FIXUP);
+ }
+ }
remove_bb_from_loops (bb);
}
this fixes this ICE, but causes other ICEs.
I'd be really really grateful for any hints.
