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.
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();
> +}
