On Fri, 7 Aug 2026, Alfie Richards wrote:
> This is required for HSSR where the IV increment is not available until the
> end
> of the loop body.
So ...
> gcc/ChangeLog:
>
> * tree-vect-loop-manip.cc (vect_set_loop_controls_directly):
> Change IV increment position when peeled.
> * tree-vect-loop.cc
> (vect_update_ivs_after_vectorizer_for_early_breaks):
> Change IV increment position.
> ---
> gcc/tree-vect-loop-manip.cc | 20 ++++++++++++++++----
> gcc/tree-vect-loop.cc | 3 +--
> 2 files changed, 17 insertions(+), 6 deletions(-)
>
> diff --git a/gcc/tree-vect-loop-manip.cc b/gcc/tree-vect-loop-manip.cc
> index 96c10340efd..cee3779e37f 100644
> --- a/gcc/tree-vect-loop-manip.cc
> +++ b/gcc/tree-vect-loop-manip.cc
> @@ -574,7 +574,10 @@ vect_set_loop_controls_directly (class loop *loop,
> loop_vec_info loop_vinfo,
> gimple_stmt_iterator incr_gsi;
> bool insert_after;
> edge exit_e = LOOP_VINFO_MAIN_EXIT (loop_vinfo);
> - vect_iv_increment_position (exit_e, &incr_gsi, &insert_after);
> + if (!LOOP_VINFO_EARLY_BREAKS_VECT_PEELED (loop_vinfo))
> + vect_iv_increment_position (exit_e, &incr_gsi, &insert_after);
> + else
> + standard_iv_increment_position (loop, &incr_gsi, &insert_after);
... this assumes the main exit exits based on the not updated IV value,
correct? Is that always true? If so why did we need the
vect_iv_increment_position in the first place? Also for
!LOOP_VINFO_EARLY_BREAKS_VECT_PEELED both should be the same
positions, no?
That is, I'm curious why we shouldn't simply always use
standard_iv_increment_position, like we do when !early-break?
> if (LOOP_VINFO_USING_DECREMENTING_IV_P (loop_vinfo))
> {
> /* Create an IV that counts down from niters_total and whose step
> @@ -723,7 +726,10 @@ vect_set_loop_controls_directly (class loop *loop,
> loop_vec_info loop_vinfo,
> a demotion). */
> gimple_seq test_seq = NULL;
> test_index = gimple_convert (&test_seq, compare_type, test_index);
> - gsi_insert_seq_before (test_gsi, test_seq, GSI_SAME_STMT);
> + if (!LOOP_VINFO_EARLY_BREAKS_VECT_PEELED (loop_vinfo))
> + gsi_insert_seq_before (test_gsi, test_seq, GSI_SAME_STMT);
> + else
> + gsi_insert_seq_after (&incr_gsi, test_seq, GSI_NEW_STMT);
>
> /* Provide a definition of each control in the group. */
> tree next_ctrl = NULL_TREE;
> @@ -832,14 +838,20 @@ vect_set_loop_controls_directly (class loop *loop,
> loop_vec_info loop_vinfo,
> gimple_seq stmts = NULL;
> next_ctrl = vect_gen_while (&stmts, ctrl_type, test_index,
> this_test_limit, "next_mask");
> - gsi_insert_seq_before (test_gsi, stmts, GSI_SAME_STMT);
> + if (!LOOP_VINFO_EARLY_BREAKS_VECT_PEELED (loop_vinfo))
> + gsi_insert_seq_before (test_gsi, stmts, GSI_SAME_STMT);
> + else
> + gsi_insert_seq_after (&incr_gsi, stmts, GSI_SAME_STMT);
> }
> else
> {
> next_ctrl = make_temp_ssa_name (compare_type, NULL, "next_len");
> gimple_seq seq = vect_gen_len (next_ctrl, test_index, this_test_limit,
> length_limit);
> - gsi_insert_seq_before (test_gsi, seq, GSI_SAME_STMT);
> + if (!LOOP_VINFO_EARLY_BREAKS_VECT_PEELED (loop_vinfo))
> + gsi_insert_seq_before (test_gsi, seq, GSI_SAME_STMT);
> + else
> + gsi_insert_seq_after (&incr_gsi, seq, GSI_SAME_STMT);
> }
>
> vect_set_loop_control (loop, ctrl, init_ctrl, next_ctrl);
> diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
> index 0a09ce8bd85..42843d17be8 100644
> --- a/gcc/tree-vect-loop.cc
> +++ b/gcc/tree-vect-loop.cc
> @@ -11202,8 +11202,7 @@ vect_update_ivs_after_vectorizer_for_early_breaks
> (loop_vec_info loop_vinfo)
> /* Write the adjustments at the end of the iv increment. */
> bool insert_after;
> gimple_stmt_iterator incr_gsi;
> - vect_iv_increment_position (LOOP_VINFO_MAIN_EXIT (loop_vinfo), &incr_gsi,
> - &insert_after);
> + standard_iv_increment_position (loop, &incr_gsi, &insert_after);
>
> if (insert_after)
> gsi_insert_seq_after (&incr_gsi, stmts, GSI_NEW_STMT);
>
--
Richard Biener <[email protected]>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Jochen Jaser, Andrew McDonald, Abhinav Puri; (HRB 36809, AG Nuernberg)
