1 a32765e3 2005-08-10 devnull /*	mpvecsub(mpdigit *a, int alen, mpdigit *b, int blen, mpdigit *diff) */
 2 a32765e3 2005-08-10 devnull /*		diff[0:alen-1] = a[0:alen-1] - b[0:blen-1] */
 3 a32765e3 2005-08-10 devnull /*	prereq: alen >= blen, diff has room for alen digits */
 4 a32765e3 2005-08-10 devnull /* (very old gnu assembler doesn't allow multiline comments) */
 5 a32765e3 2005-08-10 devnull 
 6 ac0e2db6 2004-04-21 devnull .text
 7 ac0e2db6 2004-04-21 devnull 
 8 ac0e2db6 2004-04-21 devnull .p2align 2,0x90
 9 ac0e2db6 2004-04-21 devnull .globl mpvecsub
10 ac0e2db6 2004-04-21 devnull mpvecsub:
11 ac0e2db6 2004-04-21 devnull 	/* Prelude */
12 39ce0d58 2006-03-22 devnull 	pushl %ebp		/* save on stack */
13 39ce0d58 2006-03-22 devnull 	pushl %ebx
14 39ce0d58 2006-03-22 devnull 	pushl %esi
15 39ce0d58 2006-03-22 devnull 	pushl %edi
16 ac0e2db6 2004-04-21 devnull 
17 39ce0d58 2006-03-22 devnull 	leal 20(%esp), %ebp		/* %ebp = FP for now */
18 39ce0d58 2006-03-22 devnull 	movl	0(%ebp), %esi		/* a */
19 39ce0d58 2006-03-22 devnull 	movl	8(%ebp), %ebx		/* b */
20 39ce0d58 2006-03-22 devnull 	movl	4(%ebp), %edx		/* alen */
21 39ce0d58 2006-03-22 devnull 	movl	12(%ebp), %ecx		/* blen */
22 39ce0d58 2006-03-22 devnull 	movl	16(%ebp), %edi		/* diff */
23 39ce0d58 2006-03-22 devnull 
24 ac0e2db6 2004-04-21 devnull 	subl	%ecx,%edx
25 ac0e2db6 2004-04-21 devnull 	xorl	%ebp,%ebp			/* this also sets carry to 0 */
26 ac0e2db6 2004-04-21 devnull 
27 ac0e2db6 2004-04-21 devnull 	/* skip subraction if b is zero */
28 ac0e2db6 2004-04-21 devnull 	testl	%ecx,%ecx
29 ac0e2db6 2004-04-21 devnull 	jz	_sub1
30 ac0e2db6 2004-04-21 devnull 
31 ac0e2db6 2004-04-21 devnull 	/* diff[0:blen-1],borrow = a[0:blen-1] - b[0:blen-1] */
32 ac0e2db6 2004-04-21 devnull _subloop1:
33 ac0e2db6 2004-04-21 devnull 	movl	(%esi, %ebp, 4), %eax
34 ac0e2db6 2004-04-21 devnull 	sbbl	(%ebx, %ebp, 4), %eax
35 ac0e2db6 2004-04-21 devnull 	movl	%eax, (%edi, %ebp, 4)
36 ac0e2db6 2004-04-21 devnull 	incl	%ebp
37 ac0e2db6 2004-04-21 devnull 	loop	_subloop1
38 ac0e2db6 2004-04-21 devnull 
39 ac0e2db6 2004-04-21 devnull _sub1:
40 ac0e2db6 2004-04-21 devnull 	incl	%edx
41 ac0e2db6 2004-04-21 devnull 	movl	%edx,%ecx
42 ac0e2db6 2004-04-21 devnull 	loop	_subloop2
43 ac0e2db6 2004-04-21 devnull 	jmp done
44 ac0e2db6 2004-04-21 devnull 
45 ac0e2db6 2004-04-21 devnull 	/* diff[blen:alen-1] = a[blen:alen-1] - 0 */
46 ac0e2db6 2004-04-21 devnull _subloop2:
47 ac0e2db6 2004-04-21 devnull 	movl	(%esi, %ebp, 4), %eax
48 ac0e2db6 2004-04-21 devnull 	sbbl	$0, %eax
49 ac0e2db6 2004-04-21 devnull 	movl	%eax, (%edi, %ebp, 4)
50 39ce0d58 2006-03-22 devnull 	incl	%ebp
51 39ce0d58 2006-03-22 devnull 	loop	_subloop2
52 ac0e2db6 2004-04-21 devnull 
53 ac0e2db6 2004-04-21 devnull done:
54 ac0e2db6 2004-04-21 devnull 	/* Postlude */
55 39ce0d58 2006-03-22 devnull 	popl %edi
56 39ce0d58 2006-03-22 devnull 	popl %esi
57 39ce0d58 2006-03-22 devnull 	popl %ebx
58 39ce0d58 2006-03-22 devnull 	popl %ebp
59 ac0e2db6 2004-04-21 devnull 	ret
60 ac0e2db6 2004-04-21 devnull