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From: David Hildenbrand <david@redhat.com>
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Date: Tue, 16 Apr 2019 10:40:52 +0200
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Subject: Re: [Qemu-devel] [PATCH v1 05/41] s390x/tcg: Implement VECTOR ADD
 WITH CARRY COMPUTE CARRY
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To: Richard Henderson <richard.henderson@linaro.org>, qemu-devel@nongnu.org
Cc: qemu-s390x@nongnu.org, Cornelia Huck <cohuck@redhat.com>, Thomas Huth <thuth@redhat.com>, Richard Henderson <rth@twiddle.net>

On 12.04.19 23:58, Richard Henderson wrote:
> On 4/11/19 12:08 AM, David Hildenbrand wrote:
>> +static DisasJumpType op_vaccc(DisasContext *s, DisasOps *o)
>> +{
>> +    if (get_field(s->fields, m5) != ES_128) {
>> +        gen_program_exception(s, PGM_SPECIFICATION);
>> +        return DISAS_NORETURN;
>> +    }
>> +
>> +    gen_gvec_4_ool(get_field(s->fields, v1), get_field(s->fields, v2),
>> +                   get_field(s->fields, v3), get_field(s->fields, v4), 0,
>> +                   gen_helper_gvec_vaccc128);
>> +    return DISAS_NEXT;
>> +}
> 
> An inline expansion could be
> 
> One possible expansion is
> 
>   tcg_gen_andi_i64(tl, cl, 1);
>   tcg_gen_add2_i64(tl, th, tl, zero, al, zero);
>   tcg_gen_add2_i64(tl, th, tl, th, bl, zero);
>   tcg_gen_add2_i64(tl, th, th, zero, ah, zero);
>   tcg_gen_add2_i64(tl, th, tl, th, bl, zero);
>   /* carry out in th */
> 
> This is 8 insns for the addition vs the hw optimal 6, but we're not exactly an
> optimizing compiler either.  ;-)
> 

Yes, very nice! Thanks!

> 
> r~
> 


-- 

Thanks,

David / dhildenb