1 4e3a81b9 2006-04-21 devnull /*	mpvecsub(mpdigit *a, int alen, mpdigit *b, int blen, mpdigit *diff) */
 2 4e3a81b9 2006-04-21 devnull /*		diff[0:alen-1] = a[0:alen-1] - b[0:blen-1] */
 3 4e3a81b9 2006-04-21 devnull /*	prereq: alen >= blen, diff has room for alen digits */
 4 4e3a81b9 2006-04-21 devnull /* (very old gnu assembler doesn't allow multiline comments) */
 5 4e3a81b9 2006-04-21 devnull 
 6 4e3a81b9 2006-04-21 devnull .text
 7 4e3a81b9 2006-04-21 devnull 
 8 4e3a81b9 2006-04-21 devnull .p2align 2,0x90
 9 4e3a81b9 2006-04-21 devnull .globl _mpvecsub
10 4e3a81b9 2006-04-21 devnull _mpvecsub:
11 4e3a81b9 2006-04-21 devnull 	/* Prelude */
12 4e3a81b9 2006-04-21 devnull 	pushl %ebp		/* save on stack */
13 4e3a81b9 2006-04-21 devnull 	pushl %ebx
14 4e3a81b9 2006-04-21 devnull 	pushl %esi
15 4e3a81b9 2006-04-21 devnull 	pushl %edi
16 4e3a81b9 2006-04-21 devnull 
17 4e3a81b9 2006-04-21 devnull 	leal 20(%esp), %ebp		/* %ebp = FP for now */
18 4e3a81b9 2006-04-21 devnull 	movl	0(%ebp), %esi		/* a */
19 4e3a81b9 2006-04-21 devnull 	movl	8(%ebp), %ebx		/* b */
20 4e3a81b9 2006-04-21 devnull 	movl	4(%ebp), %edx		/* alen */
21 4e3a81b9 2006-04-21 devnull 	movl	12(%ebp), %ecx		/* blen */
22 4e3a81b9 2006-04-21 devnull 	movl	16(%ebp), %edi		/* diff */
23 4e3a81b9 2006-04-21 devnull 
24 4e3a81b9 2006-04-21 devnull 	subl	%ecx,%edx
25 4e3a81b9 2006-04-21 devnull 	xorl	%ebp,%ebp			/* this also sets carry to 0 */
26 4e3a81b9 2006-04-21 devnull 
27 4e3a81b9 2006-04-21 devnull 	/* skip subraction if b is zero */
28 4e3a81b9 2006-04-21 devnull 	testl	%ecx,%ecx
29 4e3a81b9 2006-04-21 devnull 	jz	_sub1
30 4e3a81b9 2006-04-21 devnull 
31 4e3a81b9 2006-04-21 devnull 	/* diff[0:blen-1],borrow = a[0:blen-1] - b[0:blen-1] */
32 4e3a81b9 2006-04-21 devnull _subloop1:
33 4e3a81b9 2006-04-21 devnull 	movl	(%esi, %ebp, 4), %eax
34 4e3a81b9 2006-04-21 devnull 	sbbl	(%ebx, %ebp, 4), %eax
35 4e3a81b9 2006-04-21 devnull 	movl	%eax, (%edi, %ebp, 4)
36 4e3a81b9 2006-04-21 devnull 	incl	%ebp
37 4e3a81b9 2006-04-21 devnull 	loop	_subloop1
38 4e3a81b9 2006-04-21 devnull 
39 4e3a81b9 2006-04-21 devnull _sub1:
40 4e3a81b9 2006-04-21 devnull 	incl	%edx
41 4e3a81b9 2006-04-21 devnull 	movl	%edx,%ecx
42 4e3a81b9 2006-04-21 devnull 	loop	_subloop2
43 4e3a81b9 2006-04-21 devnull 	jmp done
44 4e3a81b9 2006-04-21 devnull 
45 4e3a81b9 2006-04-21 devnull 	/* diff[blen:alen-1] = a[blen:alen-1] - 0 */
46 4e3a81b9 2006-04-21 devnull _subloop2:
47 4e3a81b9 2006-04-21 devnull 	movl	(%esi, %ebp, 4), %eax
48 4e3a81b9 2006-04-21 devnull 	sbbl	$0, %eax
49 4e3a81b9 2006-04-21 devnull 	movl	%eax, (%edi, %ebp, 4)
50 4e3a81b9 2006-04-21 devnull 	incl	%ebp
51 4e3a81b9 2006-04-21 devnull 	loop	_subloop2
52 4e3a81b9 2006-04-21 devnull 
53 4e3a81b9 2006-04-21 devnull done:
54 4e3a81b9 2006-04-21 devnull 	/* Postlude */
55 4e3a81b9 2006-04-21 devnull 	popl %edi
56 4e3a81b9 2006-04-21 devnull 	popl %esi
57 4e3a81b9 2006-04-21 devnull 	popl %ebx
58 4e3a81b9 2006-04-21 devnull 	popl %ebp
59 4e3a81b9 2006-04-21 devnull 	ret
60 4e3a81b9 2006-04-21 devnull