> -----Original Message-----
> From: Richard Biener <rguent...@suse.de>
> Sent: Wednesday, December 6, 2023 8:18 AM
> To: Tamar Christina <tamar.christ...@arm.com>
> Cc: gcc-patches@gcc.gnu.org; nd <n...@arm.com>; j...@ventanamicro.com
> Subject: Re: [PATCH 13/21]middle-end: Update loop form analysis to support
> early
> break
>
> 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..f9483eff6e9606e835906fb991
> f07cd6052491d0 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?
No, only non-alias versioning. I don't believe we can alias in the current
implementation because it's restricted to statically known objects with
a fixed size.
Thanks,
Tamar
>
> Otherwise OK.
>
> Thanks,
> Richard.
