On Fri, Oct 12, 2012 at 6:16 AM, Vladimir Makarov wrote: > On 12-10-11 4:17 PM, Steven Bosscher wrote: >> >> Hello, >> >> IRA uses record_loop_exits() to cache the loop exit edges, but due to >> a code ordering bug the edges are not actually recorded. >> record_loop_exits() starts with: >> >> if (!current_loops) >> return; > > I have no idea why record_loop_exits is here. Loop exits are not used in > IRA. I think it should be removed.
Actually they are used alright: $ grep -n get_loop_exit_edges ira* ira-build.c:169: edges = get_loop_exit_edges (loop); ira-build.c:1774: edges = get_loop_exit_edges (loop_node->loop); ira-build.c:1972: edges = get_loop_exit_edges (loop); ira-color.c:2023: edges = get_loop_exit_edges (loop_node->loop); Especially the last one, in ira_loop_edge_freq, seems to be called frequently enough to justify caching loop exit edges. >> So ira.c should set current_loops before calling record_loop_exits. >> With the current order, the exists are not actually recorded. Also, >> ira.c should release recorded exits and loops, this releases a >> considerable amount of GC memory that can be re-used in the next IRA >> iteration. >> >> It's not clear to me why IRA has to re-compute the cfgloop tree from >> scratch, though, so I've added a "???" comment for that. > > I am not a specialist in cfgloop code. I did not find how to update it > incrementally. So I just rebuild it. > > My be you can advice how to do this. IRA can generate insns on the BB > edges, it results in creation of new BBs on the region exits/enters. AFAIU this mostly happens automatically for simple edge splitting operations, and for more complex transformations there is fix_loop_structure. But I'm not sure, perhaps Richi can give some advice. Ciao! Steven
