On Mon, 6 Nov 2023, Tamar Christina wrote:
> Hi All,
>
> This has loop versioning use the vectorizer's IV exit edge when it's available
> since single_exit (..) fails with multiple exits.
>
> Bootstrapped Regtested on aarch64-none-linux-gnu and no issues.
>
> Ok for master?
>
> Thanks,
> Tamar
>
> gcc/ChangeLog:
>
> * tree-vect-loop-manip.cc (vect_loop_versioning): Support multiple
> exits.
>
> --- inline copy of patch --
> diff --git a/gcc/tree-vect-loop-manip.cc b/gcc/tree-vect-loop-manip.cc
> index
> 3d59119787d6afdc5a6465a547d1ea2d3d940373..58b4b9c11d8b844ee86156cdfcba7f838030a7c2
> 100644
> --- a/gcc/tree-vect-loop-manip.cc
> +++ b/gcc/tree-vect-loop-manip.cc
> @@ -4180,12 +4180,24 @@ vect_loop_versioning (loop_vec_info loop_vinfo,
> If loop versioning wasn't done from loop, but scalar_loop instead,
> merge_bb will have already just a single successor. */
>
> - merge_bb = single_exit (loop_to_version)->dest;
> + /* Due to the single_exit check above we should only get here when
> + loop == loop_to_version, that means we can use loop_vinfo to get the
> + exits. */
You mean LOOP_VINFO_EARLY_BREAKS can only ever version the loop
itself? That's correct. All inner loops of loop_to_version have
a single exit unless it's loop itself.
Please reword a bit and instead do
edge exit_edge;
if (loop_to_version == loop)
exit_edge = LOOP_VINFO_IV_EXIT (loop_vinfo);
else
exit_edge = single_exit (loop_to_version);
OK with that change.
Richard.
> + edge exit_edge = single_exit (loop_to_version);
> + if (LOOP_VINFO_EARLY_BREAKS (loop_vinfo))
> + {
> + /* In early exits the main exit will fail into the merge block of the
> + alternative exits. So we need the single successor of the main
> + exit here to find the merge block. */
> + exit_edge = LOOP_VINFO_IV_EXIT (loop_vinfo);
> + }
> + gcc_assert (exit_edge);
> + merge_bb = exit_edge->dest;
> if (EDGE_COUNT (merge_bb->preds) >= 2)
> {
> gcc_assert (EDGE_COUNT (merge_bb->preds) >= 2);
> - new_exit_bb = split_edge (single_exit (loop_to_version));
> - new_exit_e = single_exit (loop_to_version);
> + new_exit_bb = split_edge (exit_edge);
> + new_exit_e = exit_edge;
> e = EDGE_SUCC (new_exit_bb, 0);
>
> for (gsi = gsi_start_phis (merge_bb); !gsi_end_p (gsi);
