> -----Original Message-----
> From: Richard Biener <richard.guent...@gmail.com>
> Sent: Thursday, March 7, 2024 8:47 AM
> To: Robin Dapp <rdapp....@gmail.com>
> Cc: gcc-patches <gcc-patches@gcc.gnu.org>; Tamar Christina
> <tamar.christ...@arm.com>
> Subject: Re: [PATCH] vect: Do not peel epilogue for partial vectors
> [PR114196].
>
> On Wed, Mar 6, 2024 at 9:21 PM Robin Dapp <rdapp....@gmail.com> wrote:
> >
> > Hi,
> >
> > r14-7036-gcbf569486b2dec added an epilogue vectorization guard for early
> > break but PR114196 shows that we also run into the problem without early
> > break. Therefore remove early break from the conditions.
> >
> > gcc/ChangeLog:
> >
> > PR middle-end/114196
> >
> > * tree-vect-loop-manip.cc (vect_can_peel_nonlinear_iv_p): Remove
> > early break check from guards.
> >
> > gcc/testsuite/ChangeLog:
> >
> > * gcc.target/aarch64/pr114196.c: New test.
> > * gcc.target/riscv/rvv/autovec/pr114196.c: New test.
> > ---
> > gcc/testsuite/gcc.target/aarch64/pr114196.c | 19 +++++++++++++++++++
> > .../gcc.target/riscv/rvv/autovec/pr114196.c | 19 +++++++++++++++++++
> > gcc/tree-vect-loop-manip.cc | 6 +++---
> > 3 files changed, 41 insertions(+), 3 deletions(-)
> > create mode 100644 gcc/testsuite/gcc.target/aarch64/pr114196.c
> > create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/autovec/pr114196.c
> >
> > diff --git a/gcc/testsuite/gcc.target/aarch64/pr114196.c
> b/gcc/testsuite/gcc.target/aarch64/pr114196.c
> > new file mode 100644
> > index 00000000000..15e4b0e31b8
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/aarch64/pr114196.c
> > @@ -0,0 +1,19 @@
> > +/* { dg-do compile } */
> > +/* { dg-options { -O3 -fno-vect-cost-model -march=armv9-a -msve-vector-
> bits=256 } } */
> > +
> > +unsigned a;
> > +int b;
> > +long *c;
> > +
> > +int
> > +main ()
> > +{
> > + for (int d = 0; d < 22; d += 4) {
> > + b = ({
> > + int e = c[d];
> > + e;
> > + })
> > + ? 0 : -c[d];
> > + a *= 3;
> > + }
> > +}
> > diff --git a/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr114196.c
> b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr114196.c
> > new file mode 100644
> > index 00000000000..7ba9cbbed70
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr114196.c
> > @@ -0,0 +1,19 @@
> > +/* { dg-do compile } */
> > +/* { dg-options { -O3 -fno-vect-cost-model -march=rv64gcv_zvl256b -
> mabi=lp64d -mrvv-vector-bits=zvl } } */
> > +
> > +unsigned a;
> > +int b;
> > +long *c;
> > +
> > +int
> > +main ()
> > +{
> > + for (int d = 0; d < 22; d += 4) {
> > + b = ({
> > + int e = c[d];
> > + e;
> > + })
> > + ? 0 : -c[d];
> > + a *= 3;
> > + }
> > +}
> > diff --git a/gcc/tree-vect-loop-manip.cc b/gcc/tree-vect-loop-manip.cc
> > index f72da915103..c3cd20eef70 100644
> > --- a/gcc/tree-vect-loop-manip.cc
> > +++ b/gcc/tree-vect-loop-manip.cc
> > @@ -2183,9 +2183,9 @@ vect_can_peel_nonlinear_iv_p (loop_vec_info
> loop_vinfo,
> > perform the peeling. The below condition mirrors that of
> > vect_gen_vector_loop_niters where niters_vector_mult_vf_var then sets
> > step_vector to VF rather than 1. This is what creates the nonlinear
> > - IV. PR113163. */
> > - if (LOOP_VINFO_EARLY_BREAKS (loop_vinfo)
> > - && LOOP_VINFO_VECT_FACTOR (loop_vinfo).is_constant ()
> > + IV. PR113163.
> > + This also happens without early breaks, see PR114196. */
>
> Can you instead reword to not mention early breaks, maybe instead
> say PR113163 (with early breaks), PR114196 (without)?
>
> The dump message also needs adjustments, it mentions early breaks as
> well.
>
> The comment says it matches a condition in vect_gen_vector_loop_niters
> but I can't see what that means ... Tamar?
>
The comment was trying to say that this case is when you manage to get here:
https://github.com/gcc-mirror/gcc/blob/95b6ee96348041eaee9133f082b57f3e57ef0b11/gcc/tree-vect-loop-manip.cc#L2847
because that makes you fall into
https://github.com/gcc-mirror/gcc/blob/95b6ee96348041eaee9133f082b57f3e57ef0b11/gcc/tree-vect-loop-manip.cc#L3528
which creates the nonlinear IV variable.
The vect_step_op_neg exception is because vect_update_ivs_after_vectorizer can
deal with that case specifically
https://github.com/gcc-mirror/gcc/blob/95b6ee96348041eaee9133f082b57f3e57ef0b11/gcc/tree-vect-loop-manip.cc#L2398
which is what the previous check is also explaining
https://github.com/gcc-mirror/gcc/blob/95b6ee96348041eaee9133f082b57f3e57ef0b11/gcc/tree-vect-loop-manip.cc#L2133
If this also happens for non-early breaks it's just better to merge the check
into the earlier one at
github.com/gcc-mirror/gcc/blob/95b6ee96348041eaee9133f082b57f3e57ef0b11/gcc/tree-vect-loop-manip.cc#L2133
Tamar
> > + if (LOOP_VINFO_VECT_FACTOR (loop_vinfo).is_constant ()
> > && LOOP_VINFO_USING_PARTIAL_VECTORS_P (loop_vinfo)
> > && induction_type != vect_step_op_neg)
> > {
> > --
> > 2.43.2
