On Mon, Jun 8, 2026 at 12:20 AM Richard Sandiford
<[email protected]> wrote:
>
> r17-899-g52d5a8870d2108 added a pattern with a nested vec_duplicate,
> but I think those should be folded down to a single vec_duplicate.
>
> The later:
>
> if (VECTOR_MODE_P (mode)
> && vec_duplicate_p (op, &elt)
> && code != VEC_DUPLICATE)
>
> handles only scalar elements, but this rule applies to vec_duplicates
> of vectors as well.
>
> A bit of scripting suggests that this was the only use of nested
> vec_duplicates in the md files.
>
> This is tested by gcc.target/aarch64/sve/vec_init_5.c.
>
> Tested on aarch64-linux-gnu, powerpc64le-linux-gnu and x86_64-linux-gnu.
> OK to install?
Ok.
>
> Richard
>
>
> gcc/
> * simplify-rtx.cc (simplify_context::simplify_unary_operation_1):
> Simplify vec_duplicates of vec_duplicates.
> * config/aarch64/aarch64.md
> (*aarch64_vec_duplicate_subvector<vconsv><vconq><mode>): Remove
> nested vec_duplicate.
> ---
> gcc/config/aarch64/aarch64-sve.md | 3 +--
> gcc/simplify-rtx.cc | 6 ++++++
> 2 files changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/gcc/config/aarch64/aarch64-sve.md
> b/gcc/config/aarch64/aarch64-sve.md
> index 585a587d8cf..723b8d6e6ec 100644
> --- a/gcc/config/aarch64/aarch64-sve.md
> +++ b/gcc/config/aarch64/aarch64-sve.md
> @@ -2895,8 +2895,7 @@
> (define_insn "*aarch64_vec_duplicate_subvector<vconsv><vconq><mode>"
> [(set (match_operand:<VCONSV> 0 "register_operand")
> (vec_duplicate:<VCONSV>
> - (vec_duplicate:<VCONQ>
> - (match_operand:VQDUP 1 "register_operand"))))]
> + (match_operand:VQDUP 1 "register_operand")))]
> "TARGET_SVE"
> {@ [ cons: =0 , 1 ]
> [ w , r ] mov\t%0.<single_type>, %<single_wx>1
> diff --git a/gcc/simplify-rtx.cc b/gcc/simplify-rtx.cc
> index c2d89641dfc..872ae032869 100644
> --- a/gcc/simplify-rtx.cc
> +++ b/gcc/simplify-rtx.cc
> @@ -1900,6 +1900,12 @@ simplify_context::simplify_unary_operation_1 (rtx_code
> code, machine_mode mode,
> #endif
> break;
>
> + case VEC_DUPLICATE:
> + if (GET_CODE (op) == VEC_DUPLICATE)
> + return simplify_gen_unary (VEC_DUPLICATE, mode, XEXP (op, 0),
> + GET_MODE (XEXP (op, 0)));
> + break;
> +
> default:
> break;
> }
> --
> 2.54.0
>
