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

[Richard Henderson]

On 2/8/21 12:50 PM, Peter Maydell wrote:
> 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?

It's a works either way thing.


r~

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