On Mon, 6 Nov 2023, Tamar Christina wrote:
> Hi All,
>
> This sets LOOP_VINFO_EARLY_BREAKS and does some misc changes so the other
> patches are self contained.
>
> Bootstrapped Regtested on aarch64-none-linux-gnu and no issues.
>
> Ok for master?
>
> Thanks,
> Tamar
>
> gcc/ChangeLog:
>
> * tree-vect-loop.cc (vect_analyze_loop_form): Analyse all exits.
> (vect_create_loop_vinfo): Set LOOP_VINFO_EARLY_BREAKS.
> (vect_transform_loop): Use it.
>
> --- inline copy of patch --
> diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
> index
> 51a054c5b035ac80dfbbf3b5ba2f6da82fda91f6..f9483eff6e9606e835906fb991f07cd6052491d0
> 100644
> --- a/gcc/tree-vect-loop.cc
> +++ b/gcc/tree-vect-loop.cc
> @@ -1700,12 +1700,12 @@ vect_compute_single_scalar_iteration_cost
> (loop_vec_info loop_vinfo)
> loop_vinfo->scalar_costs->finish_cost (nullptr);
> }
>
> -
> /* Function vect_analyze_loop_form.
>
> Verify that certain CFG restrictions hold, including:
> - the loop has a pre-header
> - - the loop has a single entry and exit
> + - the loop has a single entry
> + - nested loops can have only a single exit.
> - the loop exit condition is simple enough
> - the number of iterations can be analyzed, i.e, a countable loop. The
> niter could be analyzed under some assumptions. */
> @@ -1841,10 +1841,14 @@ vect_analyze_loop_form (class loop *loop,
> vect_loop_form_info *info)
> "not vectorized: latch block not empty.\n");
>
> /* Make sure the exit is not abnormal. */
> - if (exit_e->flags & EDGE_ABNORMAL)
> - return opt_result::failure_at (vect_location,
> - "not vectorized:"
> - " abnormal loop exit edge.\n");
> + auto_vec<edge> exits = get_loop_exit_edges (loop);
> + for (edge e : exits)
Seeing this multiple times, this isn't the most efficient way to
iterate over all exits with LOOPS_HAVE_RECORDED_EXITS.
Note to myself: fix (add to) the API.
> + {
> + if (e->flags & EDGE_ABNORMAL)
> + return opt_result::failure_at (vect_location,
> + "not vectorized:"
> + " abnormal loop exit edge.\n");
> + }
>
> info->conds
> = vect_get_loop_niters (loop, exit_e, &info->assumptions,
> @@ -1920,6 +1924,10 @@ vect_create_loop_vinfo (class loop *loop,
> vec_info_shared *shared,
>
> LOOP_VINFO_IV_EXIT (loop_vinfo) = info->loop_exit;
>
> + /* Check to see if we're vectorizing multiple exits. */
> + LOOP_VINFO_EARLY_BREAKS (loop_vinfo)
> + = !LOOP_VINFO_LOOP_CONDS (loop_vinfo).is_empty ();
> +
Seeing this, s/LOOP_VINFO_LOOP_CONDS/LOOP_VINFO_LOOP_EXIT_CONDS/g
might be good, if we in future avoid if-conversion in a separate
pass we will have other CONDs as well.
> if (info->inner_loop_cond)
> {
> stmt_vec_info inner_loop_cond_info
> @@ -11577,7 +11585,7 @@ vect_transform_loop (loop_vec_info loop_vinfo, gimple
> *loop_vectorized_call)
> /* Make sure there exists a single-predecessor exit bb. Do this before
> versioning. */
> edge e = LOOP_VINFO_IV_EXIT (loop_vinfo);
> - if (! single_pred_p (e->dest))
> + if (! single_pred_p (e->dest) && !LOOP_VINFO_EARLY_BREAKS (loop_vinfo))
> {
> split_loop_exit_edge (e, true);
Note this splitting is done to fulfil versioning constraints on CFG
update. Do you have test coverage with alias versioning and early
breaks?
Otherwise OK.
Thanks,
Richard.
