2012/3/5 Andrey Belevantsev <a...@ispras.ru>:
> Hello,
>
> The PR is about selective scheduling not trying hard enough to find a
> neighbor block to stick the note list from an empty block being removed.
> Fixed by a) trying harder and b) making sure that if we fail to find the
> right place, we just drop the notes instead of asserting.
>
> Tested on x86-64 and ia64, approved by Alexander offline. No test as it has
> quite insane number of flags that would likely stop reproducing the core
> issue in a few weeks.
>
> Richard, Jakub, I can commit this to trunk today or to wait until the
> release. The patch is very safe and so can be committed in case we will
> need an RC2, if you want one bug less in a release, but I would feel equally
> happy to postpone it until 4.7.1 as the problematic situation is quite rare
> (and probably requires pipelining outer loops to trigger which is disabled
> with ia64/-O3).
Note that 4.7 has branched, so you can commit to trunk. As it's a
non-standard option please defer backport until after the release of 4.7.0.
Thanks,
Richard.
> Yours,
> Andrey
>
> 2012-03-05 Andrey Belevantsev <a...@ispras.ru>
>
> PR rtl-optimization/52250
> * sel-sched-ir.c (maybe_tidy_empty_bb): Try harder to find a bb
> to put note list into. Unconditionally call move_bb_info.
> (move_bb_info): Do not assert the blocks being in the same region,
> just drop the note list if they are not.
>
>
> diff --git a/gcc/sel-sched-ir.c b/gcc/sel-sched-ir.c
> index a93cd68..c53d2e1 100644
> --- a/gcc/sel-sched-ir.c
> +++ b/gcc/sel-sched-ir.c
> @@ -3658,7 +3658,7 @@ sel_recompute_toporder (void)
> static bool
> maybe_tidy_empty_bb (basic_block bb)
> {
> - basic_block succ_bb, pred_bb;
> + basic_block succ_bb, pred_bb, note_bb;
> VEC (basic_block, heap) *dom_bbs;
> edge e;
> edge_iterator ei;
> @@ -3697,6 +3697,17 @@ maybe_tidy_empty_bb (basic_block bb)
> pred_bb = NULL;
> dom_bbs = NULL;
>
> + /* Save a pred/succ from the current region to attach the notes to. */
> + note_bb = NULL;
> + FOR_EACH_EDGE (e, ei, bb->preds)
> + if (in_current_region_p (e->src))
> + {
> + note_bb = e->src;
> + break;
> + }
> + if (note_bb == NULL)
> + note_bb = succ_bb;
> +
> /* Redirect all non-fallthru edges to the next bb. */
> while (rescan_p)
> {
> @@ -3746,10 +3757,8 @@ maybe_tidy_empty_bb (basic_block bb)
> else
> {
> /* This is a block without fallthru predecessor. Just delete it. */
> - gcc_assert (pred_bb != NULL);
> -
> - if (in_current_region_p (pred_bb))
> - move_bb_info (pred_bb, bb);
> + gcc_assert (note_bb);
> + move_bb_info (note_bb, bb);
> remove_empty_bb (bb, true);
> }
>
> @@ -5231,10 +5240,9 @@ sel_remove_bb (basic_block bb, bool
> remove_from_cfg_p)
> static void
> move_bb_info (basic_block merge_bb, basic_block empty_bb)
> {
> - gcc_assert (in_current_region_p (merge_bb));
> -
> - concat_note_lists (BB_NOTE_LIST (empty_bb),
> - &BB_NOTE_LIST (merge_bb));
> + if (in_current_region_p (merge_bb))
> + concat_note_lists (BB_NOTE_LIST (empty_bb),
> + &BB_NOTE_LIST (merge_bb));
> BB_NOTE_LIST (empty_bb) = NULL_RTX;
>
> }
