On Wed, 4 Dec 2024, Tamar Christina wrote:
> Hi All,
>
> For architectures where the vector-length is a compile-time variable,
> rather representing a runtime constant, as is the case with SVE it is
> perfectly reasonable that such vector be made up of two (or more) subvector
> components of a compatible sub-length variable.
>
> One example of this would be the concatenation of two VNx4QI vectors
> into a single VNx8QI vector.
>
> This patch adds initial support for the enablement of this feature in
> the middle-end, removing the `.is_constant()' constraint on the vector's
> number of elements, instead making the constant no. of elements the
> multiple of the number of subvectors (which must then also be of
> variable length, such that their polynomial ratio then results in a
> compile-time constant) required to fill the vector.
>
> gcc/ChangeLog:
>
> PR target/96342
> * expr.cc (store_constructor): add support for variable-length
> vectors.
>
> Co-authored-by: Tamar Christina <tamar.christ...@arm.com>
>
> Bootstrapped Regtested on aarch64-none-linux-gnu,
> arm-none-linux-gnueabihf, x86_64-pc-linux-gnu
> -m32, -m64 and no issues.
>
> Ok for master?
>
> Thanks,
> Tamar
>
> ---
> diff --git a/gcc/expr.cc b/gcc/expr.cc
> index
> 2d90d7aac296077cc0bda8a1b4732b1cd44a610d..8bdec1cbf78ce338c135a6660bcb3abc75884c0c
> 100644
> --- a/gcc/expr.cc
> +++ b/gcc/expr.cc
> @@ -7962,11 +7962,11 @@ store_constructor (tree exp, rtx target, int cleared,
> poly_int64 size,
>
> n_elts = TYPE_VECTOR_SUBPARTS (type);
> if (REG_P (target)
> - && VECTOR_MODE_P (mode)
> - && n_elts.is_constant (&const_n_elts))
> + && VECTOR_MODE_P (mode))
> {
> machine_mode emode = eltmode;
> bool vector_typed_elts_p = false;
> + auto nunits = GET_MODE_NUNITS (emode);
>
> if (CONSTRUCTOR_NELTS (exp)
> && (TREE_CODE (TREE_TYPE (CONSTRUCTOR_ELT (exp, 0)->value))
> @@ -7976,22 +7976,30 @@ store_constructor (tree exp, rtx target, int cleared,
> poly_int64 size,
> gcc_assert (known_eq (CONSTRUCTOR_NELTS (exp)
> * TYPE_VECTOR_SUBPARTS (etype),
> n_elts));
> +
> emode = TYPE_MODE (etype);
> vector_typed_elts_p = true;
> + nunits = TYPE_VECTOR_SUBPARTS (etype);
> }
> - icode = convert_optab_handler (vec_init_optab, mode, emode);
> - if (icode != CODE_FOR_nothing)
> - {
> - unsigned int n = const_n_elts;
>
> - if (vector_typed_elts_p)
> + /* For a non-const type vector, we check it is made up of similarly
> + non-const type vectors. */
> + if (exact_div (n_elts, nunits).is_constant (&const_n_elts))
I think this is guaranteed by tree-cfg.cc:4767?
So I think we can simply set const_n_elts to CONSTRUCTOR_NELTS
for vector_typed_elts_p?
That said - by refactoring to separate the vector elt from scalar
elt case this might look more obvious (also no need to clear
RTVEC_ELT in that case)?
> + {
> + icode = convert_optab_handler (vec_init_optab, mode, emode);
> + if (icode != CODE_FOR_nothing)
> {
> - n = CONSTRUCTOR_NELTS (exp);
> - vec_vec_init_p = true;
> + unsigned int n = const_n_elts;
> +
> + if (vector_typed_elts_p)
> + {
> + n = CONSTRUCTOR_NELTS (exp);
> + vec_vec_init_p = true;
> + }
> + vector = rtvec_alloc (n);
> + for (unsigned int k = 0; k < n; k++)
> + RTVEC_ELT (vector, k) = CONST0_RTX (emode);
> }
> - vector = rtvec_alloc (n);
> - for (unsigned int k = 0; k < n; k++)
> - RTVEC_ELT (vector, k) = CONST0_RTX (emode);
> }
> }
>
>
>
>
>
>
--
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)
