| 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. |
