Re: [PATCH 21/31] target/arm: Implement SVE2 integer absolute difference and accumulate long

[Laurent Desnogues]

On Tue, Apr 14, 2020 at 1:19 AM Richard Henderson
<address@hidden> wrote:
>
> On 4/13/20 9:15 AM, Laurent Desnogues wrote:
> > On Fri, Mar 27, 2020 at 12:18 AM Richard Henderson
> > <address@hidden> wrote:
> > [...]
> >> diff --git a/target/arm/sve_helper.c b/target/arm/sve_helper.c
> >> index a3653007ac..a0995d95c7 100644
> >> --- a/target/arm/sve_helper.c
> >> +++ b/target/arm/sve_helper.c
> >> @@ -1216,6 +1216,30 @@ DO_ZZZ_NTB(sve2_eoril_d, uint64_t,     , DO_EOR)
> >>
> >>  #undef DO_ZZZ_NTB
> >>
> >> +#define DO_ABAL(NAME, TYPE, TYPEN) \
> >> +void HELPER(NAME)(void *vd, void *va, void *vn, void *vm, uint32_t desc) \
> >> +{                                                              \
> >> +    intptr_t i, opr_sz = simd_oprsz(desc);                     \
> >> +    int sel1 = (simd_data(desc) & 1) * sizeof(TYPE);           \
> >> +    int sel2 = (simd_data(desc) & 2) * (sizeof(TYPE) / 2);     \
> >> +    for (i = 0; i < opr_sz; i += sizeof(TYPE)) {               \
> >> +        TYPE nn = (TYPEN)(*(TYPE *)(vn + i) >> sel1);          \
> >> +        TYPE mm = (TYPEN)(*(TYPE *)(vm + i) >> sel2);          \
> >> +        TYPE aa = *(TYPE *)(va + i);                           \
> >> +        *(TYPE *)(vd + i) = DO_ABD(nn, mm) + aa;               \
> >> +    }                                                          \
> >> +}
> >
> > ABAL is either top or bottom not a mix of two.  So only sel1 is needed
> > and its multiplicand should be the number of bits of TYPEN.
>
> Yep.
>
> > vd is both a source and a destination so a temporary should be used.
>
> In what way am I not?  Both sources are read before the write.  The operands
> are all in columns of the wide type (unlike the addp case you pointed out).

You're right, sorry.

Laurent