Ciao,
Il 2019-08-27 16:35 t...@gmplib.org ha scritto:
I got something working. It runs quite well, and seems to beat the
Great!
static inline void
mpn_gcd_NN (mp_limb_t *rp, mp_limb_t *up, mp_limb_t *vp, size_t N)
I see that your idea is to obtain a N-loop-unrolled version...
if (UNLIKELY (cy))
mpn_neg (up, up, N);
This is an unlikely branch, but I'd really suggest
{mpn_neg (up, up, N -1); up[N-1] = 0;}
because mpn_neg is full of branches :-)
if (UNLIKELY (up[0] == 0))
{
This unlikely branch may end up with an odd up[0]...
}
int cnt;
count_trailing_zeros (cnt, up[0]);
mpn_rshift (up, up, N, cnt);
... and on some platform mpn_rshift may not support cnt==0.
Maybe (for the C version) we should duplicate the ctz/shift instruction,
both inside the UNLIKELY (*up == 0) branch (deciding whether to shift or
copy) and in an else (likely) branch.
m
--
http://bodrato.it/papers/
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