2 * mpvecdigmulsub(mpdigit *b, int n, mpdigit m, mpdigit *p)
14 * hi = DX - constrained by hardware
15 * lo = AX - constrained by hardware
16 * b = SI - can't be BP
17 * p = DI - can't be BP
19 * n = CX - constrained by LOOP instr
24 TEXT mpvecdigmulsub(SB),$0
32 MOVL (SI)(BP*4),AX /* lo = b[i] */
33 MULL BX /* hi, lo = b[i] * m */
34 ADDL R8,AX /* lo += oldhi */
35 ADCL $0, DX /* hi += carry */
37 ADCL $0, DX /* hi += carry */