It's https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119181
On Fri, May 16, 2025 at 10:02 AM liuhongt <hongtao....@intel.com> wrote:
>
> The patch tries to solve miss vectorization for below case.
>
> void
> foo (int* a, int* restrict b)
> {
> b[0] = a[0] * a[64];
> b[1] = a[65] * a[1];
> b[2] = a[2] * a[66];
> b[3] = a[67] * a[3];
> b[4] = a[68] * a[4];
> b[5] = a[69] * a[5];
> b[6] = a[6] * a[70];
> b[7] = a[7] * a[71];
> }
>
> In vect_analyze_data_ref_accesses, a[0], a[1], .. a[7], a[64], ...,
> a[71] are in same group with size of 71. It caused vectorization
> unprofitable.
>
> Bootstrapped and regtested on x86_64-pc-linux-gnu{-m32,}.
> Ok for trunk?
>
> gcc/ChangeLog:
>
> * tree-vect-data-refs.cc (vect_analyze_data_ref_accesses):
> Split datarefs when there's a gap bigger than
> MAX_BITSIZE_MODE_ANY_MODE.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.dg/vect/bb-slp-pr119181.c: New test.
> ---
> gcc/testsuite/gcc.dg/vect/bb-slp-pr119181.c | 15 +++++++++++++++
> gcc/tree-vect-data-refs.cc | 6 ++++++
> 2 files changed, 21 insertions(+)
> create mode 100644 gcc/testsuite/gcc.dg/vect/bb-slp-pr119181.c
>
> diff --git a/gcc/testsuite/gcc.dg/vect/bb-slp-pr119181.c
> b/gcc/testsuite/gcc.dg/vect/bb-slp-pr119181.c
> new file mode 100644
> index 00000000000..b0d3e5a3cb8
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/vect/bb-slp-pr119181.c
> @@ -0,0 +1,15 @@
> +/* { dg-do compile } */
> +void
> +foo (int* a, int* restrict b)
> +{
> + b[0] = a[0] * a[64];
> + b[1] = a[65] * a[1];
> + b[2] = a[2] * a[66];
> + b[3] = a[67] * a[3];
> + b[4] = a[68] * a[4];
> + b[5] = a[69] * a[5];
> + b[6] = a[6] * a[70];
> + b[7] = a[7] * a[71];
> +}
> +
> +/* { dg-final { scan-tree-dump-times "optimized: basic block" 1 "slp2" {
> target vect_int_mult } } } */
> diff --git a/gcc/tree-vect-data-refs.cc b/gcc/tree-vect-data-refs.cc
> index 9fd1ef29650..387e8ac8b61 100644
> --- a/gcc/tree-vect-data-refs.cc
> +++ b/gcc/tree-vect-data-refs.cc
> @@ -3657,6 +3657,12 @@ vect_analyze_data_ref_accesses (vec_info *vinfo,
> && init_a <= init_prev
> && init_prev <= init_b);
>
> + /* For datarefs with big gap, it's better to split them into
> different
> + groups.
> + .i.e a[0], a[1], a[2], .. a[7], a[100], a[101],..., a[107] */
> + if ((unsigned HOST_WIDE_INT)(init_b - init_prev) * tree_to_uhwi
> (szb)
> + > MAX_BITSIZE_MODE_ANY_MODE / BITS_PER_UNIT)
> + break;
> /* Do not place the same access in the interleaving chain twice. */
> if (init_b == init_prev)
> {
> --
> 2.34.1
>
--
BR,
Hongtao
