Re: [PATCH v2 13/15] tcg/arm: Implement TCG_TARGET_HAS_shv_vec

[Peter Maydell]

On Mon, 8 Feb 2021 at 03:28, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> The three vector shift by vector operations are all implemented via
> expansion.  Therefore do not actually set TCG_TARGET_HAS_shv_vec,
> as none of shlv_vec, shrv_vec, sarv_vec may actually appear in the
> instruction stream, and therefore also do not appear in tcg_target_op_def.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  tcg/arm/tcg-target.opc.h |  3 ++
>  tcg/arm/tcg-target.c.inc | 61 +++++++++++++++++++++++++++++++++++++++-
>  2 files changed, 63 insertions(+), 1 deletion(-)

> +    switch (opc) {
> +    case INDEX_op_shlv_vec:
> +        /*
> +         * Merely propagate shlv_vec to arm_ushl_vec.
> +         * In this way we don't set TCG_TARGET_HAS_shv_vec
> +         * because everything is done via expansion.
> +         */
> +        v2 = temp_tcgv_vec(arg_temp(a2));
> +        vec_gen_3(INDEX_op_arm_ushl_vec, type, vece, tcgv_vec_arg(v0),
> +                  tcgv_vec_arg(v1), tcgv_vec_arg(v2));
> +        break;

tcg/aarch64 seems to set TCG_TARGET_HAS_shv_vec and
only do the right-shifts via expand_op. Is there a difference
between the two that means Neon has to do it this way, or is it
just a "works either way" thing?

> +

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

thanks
-- PMM