On Mon, 7 Jul 2025, Tamar Christina wrote:
> > -----Original Message-----
> > From: Richard Biener <rguent...@suse.de>
> > Sent: Monday, July 7, 2025 12:30 PM
> > To: gcc-patches@gcc.gnu.org
> > Cc: Tamar Christina <tamar.christ...@arm.com>
> > Subject: [PATCH] tree-optimization/120817 - bogus DSE of .MASK_STORE
> >
> > DSE used ao_ref_init_from_ptr_and_size for .MASK_STORE but
> > alias-analysis will use the specified size to disambiguate
> > against smaller objects. For .MASK_STORE we instead have to
> > make the access size unspecified but we can still constrain
> > the access extent based on the maximum size possible.
> >
> > Bootstrapped and tested on x86_64-unknown-linux-gnu.
> >
> > No testcase, I'd appreciate a runtime one.
>
> Tested locally:
>
> /* { dg-require-effective-target vect_int } */
> /* { dg-additional-options "-mcpu=neoverse-n2 -O1 -ftree-loop-vectorize" {
> target aarch64*-*-* } */
>
> #include "tree-vect.h"
>
> typedef struct {
> int _M_current;
> } __normal_iterator;
>
> typedef struct {
> char _M_elems[5];
> } array_5;
>
> __normal_iterator __trans_tmp_1 = {-5};
>
> __attribute__((noipa))
> array_5 copySourceIntoTarget() {
> array_5 target;
> char* target_it = target._M_elems;
>
> while (__trans_tmp_1._M_current != 0) {
> *target_it = 1;
> __trans_tmp_1._M_current++;
> target_it++;
> }
>
> return target;
> }
>
> int main ()
> {
>
> check_vect ();
>
> array_5 res = copySourceIntoTarget();
>
> #pragma GCC novector
> for (int i = 0; i < 5; i++)
> if (res._M_elems[i] != 1)
> __builtin_abort ();
> }
Thanks - I added the testcase and pushed the change.
Richard.
>
> >
> > PR tree-optimization/120817
> > * tree-ssa-dse.cc (initialize_ao_ref_for_dse): Use
> > ao_ref_init_from_ptr_and_range with unknown size for
> > .MASK_STORE and .MASK_LEN_STORE.
> > ---
> > gcc/tree-ssa-dse.cc | 8 ++++----
> > 1 file changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/gcc/tree-ssa-dse.cc b/gcc/tree-ssa-dse.cc
> > index 5ac4280ee36..51a572316cd 100644
> > --- a/gcc/tree-ssa-dse.cc
> > +++ b/gcc/tree-ssa-dse.cc
> > @@ -181,10 +181,10 @@ initialize_ao_ref_for_dse (gimple *stmt, ao_ref
> > *write,
> > bool may_def_ok = false)
> > can provide a may-def variant. */
> > if (may_def_ok)
> > {
> > - ao_ref_init_from_ptr_and_size (
> > - write, gimple_call_arg (stmt, 0),
> > - TYPE_SIZE_UNIT (
> > - TREE_TYPE (gimple_call_arg (stmt, stored_value_index))));
> > + ao_ref_init_from_ptr_and_range (
> > + write, gimple_call_arg (stmt, 0), true, 0, -1,
> > + tree_to_poly_int64 (TYPE_SIZE (
> > + TREE_TYPE (gimple_call_arg (stmt, stored_value_index)))));
> > return true;
> > }
> > break;
> > --
> > 2.43.0
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)
