1 /* mpvecsub(mpdigit *a, int alen, mpdigit *b, int blen, mpdigit *diff) */
2 /* diff[0:alen-1] = a[0:alen-1] - b[0:blen-1] */
3 /* prereq: alen >= blen, diff has room for alen digits */
4 /* (very old gnu assembler doesn't allow multiline comments) */
12 pushl %ebp /* save on stack */
17 leal 20(%esp), %ebp /* %ebp = FP for now */
18 movl 0(%ebp), %esi /* a */
19 movl 8(%ebp), %ebx /* b */
20 movl 4(%ebp), %edx /* alen */
21 movl 12(%ebp), %ecx /* blen */
22 movl 16(%ebp), %edi /* diff */
25 xorl %ebp,%ebp /* this also sets carry to 0 */
27 /* skip subraction if b is zero */
31 /* diff[0:blen-1],borrow = a[0:blen-1] - b[0:blen-1] */
33 movl (%esi, %ebp, 4), %eax
34 sbbl (%ebx, %ebp, 4), %eax
35 movl %eax, (%edi, %ebp, 4)
45 /* diff[blen:alen-1] = a[blen:alen-1] - 0 */
47 movl (%esi, %ebp, 4), %eax
49 movl %eax, (%edi, %ebp, 4)