Re: [Qemu-devel] [PATCH v2 25/67] target/arm: Implement SVE Integer Wide Immediate - Predicated Group

[Peter Maydell]

On 17 February 2018 at 18:22, Richard Henderson
<address@hidden> wrote:
> Signed-off-by: Richard Henderson <address@hidden>

> +/* Two operand predicated copy immediate with merge.  All valid immediates
> + * can fit within 17 signed bits in the simd_data field.
> + */
> +void HELPER(sve_cpy_m_b)(void *vd, void *vn, void *vg,
> +                         uint64_t mm, uint32_t desc)
> +{
> +    intptr_t i, opr_sz = simd_oprsz(desc) / 8;
> +    uint64_t *d = vd, *n = vn;
> +    uint8_t *pg = vg;
> +
> +    mm = (mm & 0xff) * (-1ull / 0xff);

What is this expression doing? I guess from context that it's
replicating the low 8 bits of mm across the 64-bit value,
but this is too obscure to do without a comment or wrapping
it in a helper function with a useful name, I think.


Otherwise
Reviewed-by: Peter Maydell <address@hidden>

thanks
-- PMM