Re: [Qemu-devel] [PATCH for-2.13] tcg: Allow wider vectors for cmp and mul

[Peter Maydell <peter.maydell@linaro.org>]

On 19 April 2018 at 18:32, Richard Henderson
<richard.henderson@linaro.org> wrote:
> On 04/19/2018 12:17 AM, Peter Maydell wrote:
>> On 17 April 2018 at 23:12, Richard Henderson
>> <richard.henderson@linaro.org> wrote:
>>> In db432672, we allow wide inputs for operations such as add.
>>> However, in 212be173 and 3774030a we didn't do the same for
>>> compare and multiply.
>>>
>>> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
>>
>> Can we hit these asserts in the uses of tcg_gen_mul_vec
>> and tcg_gen_cmp_vec currently in the aarch64 frontend, or
>> is this only a problem for the not-yet-landed SVE code?
>
> Only sve code -- it requires a VQ that is not a power of 2, e.g. 3.
>
>> I notice that do_shifti() also has a
>>     tcg_debug_assert(at->base_type == type);
>> Is that assert correct, or should it also be changed to >= ?
>
> I think that one is correct.  This assert is hit for something like
>
>         mul     z3, z2, z1[0]
>
> where we dup the scalar to our widest host vector width and then multiply.  In
> the case of VQ=3, the dup might be to v256, one v256 multiply, and one v128
> multiply.

Cool. In that case

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

thanks
-- PMM