On 2021/11/23 13:51, Xionghu Luo wrote:
> r12-4526 cancelled jump thread path rotates loop. It exposes a issue in
> profile-estimate when predict_extra_loop_exits, outer loop's exit edge
> is marked as inner loop's extra loop exit and set with incorrect
> prediction, then a hot inner loop will become cold loop finally through
> optimizations, this patch ignores the EDGE_DFS_BACK edge when searching
> extra exit edges to avoid unexpected predict_edge.
>
> gcc/ChangeLog:
>
> PR middle-end/103270
> * predict.c (predict_extra_loop_exits): Ignore EDGE_DFS_BACK edge.
>
> gcc/ChangeLog:
>
> PR middle-end/103270
> * predict.c (predict_extra_loop_exits): New.
> ---
> gcc/predict.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/gcc/predict.c b/gcc/predict.c
> index 68b11135680..1ae8ccff72c 100644
> --- a/gcc/predict.c
> +++ b/gcc/predict.c
> @@ -1910,6 +1910,10 @@ predict_extra_loop_exits (edge exit_edge)
> continue;
> if ((check_value_one ^ integer_onep (val)) == 1)
> continue;
> + if (e->flags & EDGE_DFS_BACK)
> + continue;
Sorry, made a mistake before send the patch, #if 0 #endif should be
removed...
> if (EDGE_COUNT (e->src->succs) != 1)
> {
> predict_paths_leading_to_edge (e, PRED_LOOP_EXTRA_EXIT, NOT_TAKEN);
>
--
Thanks,
Xionghu
