2 * mpvecsub(mpdigit *a, int alen, mpdigit *b, int blen, mpdigit *diff)
4 * diff[0:alen-1] = a[0:alen-1] - b[0:blen-1]
6 * prereq: alen >= blen, diff has room for alen digits
12 .type mpvecsub, @function
16 movl %ebx, -4(%esp) /* save on stack */
20 movl 8(%esp), %esi /* a */
21 movl 16(%esp), %ebx /* b */
22 movl 12(%esp), %edx /* alen */
23 movl 20(%esp), %ecx /* blen */
24 movl 24(%esp), %edi /* diff */
26 xorl %ebp,%ebp /* this also sets carry to 0 */
28 /* skip subraction if b is zero */
32 /* diff[0:blen-1],borrow = a[0:blen-1] - b[0:blen-1] */
34 movl (%esi, %ebp, 4), %eax
35 sbbl (%ebx, %ebp, 4), %eax
36 movl %eax, (%edi, %ebp, 4)
46 /* diff[blen:alen-1] = a[blen:alen-1] - 0 */
48 movl (%esi, %ebp, 4), %eax
50 movl %eax, (%edi, %ebp, 4)
56 movl -4(%esp), %ebx /* restore from stack */