File: [local] / OpenXM_contrib / gmp / mpn / s390 / Attic / README (download)
Revision 1.1.1.1 (vendor branch), Mon Aug 25 16:06:25 2003 UTC (20 years, 10 months ago) by ohara
Branch: GMP
CVS Tags: VERSION_4_1_2, RELEASE_1_2_3, RELEASE_1_2_2_KNOPPIX_b, RELEASE_1_2_2_KNOPPIX Changes since 1.1: +0 -0
lines
Import gmp 4.1.2
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All current (2001) S/390 and z/Architecture machines are single-issue,
but some newer machines have a deep pipeline. Software-pipelining is
therefore beneficial.
* mpn_add_n, mpn_sub_n: Use code along the lines below. Two-way unrolling
would be adequate.
mp_limb_t
mpn_add_n (mp_ptr rp, mp_srcptr up, mp_srcptr vp, mp_size_t n)
{
mp_limb_t a, b, r, cy;
mp_size_t i;
mp_limb_t mm = -1;
cy = 0;
up += n;
vp += n;
rp += n;
i = -n;
do
{
a = up[i];
b = vp[i];
r = a + b + cy;
rp[i] = r;
cy = (((a & b) | ((a | b) & (r ^ mm)))) >> 31;
i++;
}
while (i < 0);
return cy;
}
* mpn_lshift, mpn_rshift: Use SLDL/SRDL, and two-way unrolling.
* mpn_mul_1, mpn_addmul_1, mpn_submul_1: For machines with just signed
multiply (MR), use two loops, similar to the corresponding VAX or
POWER functions. Handle carry like for mpn_add_n.