On Fri, 18 Aug 2023, Richard Sandiford wrote:
> Richard Biener <rguent...@suse.de> writes:
> > The following avoids running into somehow flawed logic in fold_vec_perm
> > for non-VLA vectors.
> >
> > Bootstrap & regtest running on x86_64-unknown-linux-gnu.
> >
> > Richard.
> >
> > PR tree-optimization/111048
> > * fold-const.cc (fold_vec_perm_cst): Check for non-VLA
> > vectors first.
> >
> > * gcc.dg/torture/pr111048.c: New testcase.
>
> Please don't do this as a permanent thing. It was a deliberate choice
> to have the is_constant be the fallback, so that the "generic" (VLA+VLS)
> logic gets more coverage. Like you say, if something is wrong for VLS
> then the chances are that it's also wrong for VLA.
Sure, feel free to undo this change together with the fix for the
VLA case.
Richard.
> Thanks,
> Richard
>
>
> > ---
> > gcc/fold-const.cc | 12 ++++++------
> > gcc/testsuite/gcc.dg/torture/pr111048.c | 24 ++++++++++++++++++++++++
> > 2 files changed, 30 insertions(+), 6 deletions(-)
> > create mode 100644 gcc/testsuite/gcc.dg/torture/pr111048.c
> >
> > diff --git a/gcc/fold-const.cc b/gcc/fold-const.cc
> > index 5c51c9d91be..144fd7481b3 100644
> > --- a/gcc/fold-const.cc
> > +++ b/gcc/fold-const.cc
> > @@ -10625,6 +10625,11 @@ fold_vec_perm_cst (tree type, tree arg0, tree
> > arg1, const vec_perm_indices &sel,
> > unsigned res_npatterns, res_nelts_per_pattern;
> > unsigned HOST_WIDE_INT res_nelts;
> >
> > + if (TYPE_VECTOR_SUBPARTS (type).is_constant (&res_nelts))
> > + {
> > + res_npatterns = res_nelts;
> > + res_nelts_per_pattern = 1;
> > + }
> > /* (1) If SEL is a suitable mask as determined by
> > valid_mask_for_fold_vec_perm_cst_p, then:
> > res_npatterns = max of npatterns between ARG0, ARG1, and SEL
> > @@ -10634,7 +10639,7 @@ fold_vec_perm_cst (tree type, tree arg0, tree arg1,
> > const vec_perm_indices &sel,
> > res_npatterns = nelts in result vector.
> > res_nelts_per_pattern = 1.
> > This exception is made so that VLS ARG0, ARG1 and SEL work as before.
> > */
> > - if (valid_mask_for_fold_vec_perm_cst_p (arg0, arg1, sel, reason))
> > + else if (valid_mask_for_fold_vec_perm_cst_p (arg0, arg1, sel, reason))
> > {
> > res_npatterns
> > = std::max (VECTOR_CST_NPATTERNS (arg0),
> > @@ -10648,11 +10653,6 @@ fold_vec_perm_cst (tree type, tree arg0, tree
> > arg1, const vec_perm_indices &sel,
> >
> > res_nelts = res_npatterns * res_nelts_per_pattern;
> > }
> > - else if (TYPE_VECTOR_SUBPARTS (type).is_constant (&res_nelts))
> > - {
> > - res_npatterns = res_nelts;
> > - res_nelts_per_pattern = 1;
> > - }
> > else
> > return NULL_TREE;
> >
> > diff --git a/gcc/testsuite/gcc.dg/torture/pr111048.c
> > b/gcc/testsuite/gcc.dg/torture/pr111048.c
> > new file mode 100644
> > index 00000000000..475978aae2b
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/torture/pr111048.c
> > @@ -0,0 +1,24 @@
> > +/* { dg-do run } */
> > +/* { dg-additional-options "-mavx2" { target avx2_runtime } } */
> > +
> > +typedef unsigned char u8;
> > +
> > +__attribute__((noipa))
> > +static void check(const u8 * v) {
> > + if (*v != 15) __builtin_trap();
> > +}
> > +
> > +__attribute__((noipa))
> > +static void bug(void) {
> > + u8 in_lanes[32];
> > + for (unsigned i = 0; i < 32; i += 2) {
> > + in_lanes[i + 0] = 0;
> > + in_lanes[i + 1] = ((u8)0xff) >> (i & 7);
> > + }
> > +
> > + check(&in_lanes[13]);
> > + }
> > +
> > +int main() {
> > + bug();
> > +}
>
--
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)
