Add basic libmp support for the x86.

1 files changed, 62 insertions, 0 deletions

diff --git a/src/libmp/386/mpvecsub.s b/src/libmp/386/mpvecsub.s
new file mode 100644
index 00000000..a56b4968
--- /dev/null
+++ b/src/libmp/386/mpvecsub.s
@@ -0,0 +1,62 @@
+/*
+ *	mpvecsub(mpdigit *a, int alen, mpdigit *b, int blen, mpdigit *diff)
+ *
+ *		diff[0:alen-1] = a[0:alen-1] - b[0:blen-1]
+ *
+ *	prereq: alen >= blen, diff has room for alen digits
+ */
+.text
+
+.p2align 2,0x90
+.globl mpvecsub
+	.type mpvecsub, @function
+mpvecsub:
+	/* Prelude */
+	pushl %ebp
+	movl %ebx, -4(%esp)		/* save on stack */
+	movl %esi, -8(%esp)
+	movl %edi, -12(%esp)
+
+	movl	8(%esp), %esi		/* a */
+	movl	16(%esp), %ebx		/* b */
+	movl	12(%esp), %edx		/* alen */
+	movl	20(%esp), %ecx		/* blen */
+	movl	24(%esp), %edi		/* diff */
+	subl	%ecx,%edx
+	xorl	%ebp,%ebp			/* this also sets carry to 0 */
+
+	/* skip subraction if b is zero */
+	testl	%ecx,%ecx
+	jz	_sub1
+
+	/* diff[0:blen-1],borrow = a[0:blen-1] - b[0:blen-1] */
+_subloop1:
+	movl	(%esi, %ebp, 4), %eax
+	sbbl	(%ebx, %ebp, 4), %eax
+	movl	%eax, (%edi, %ebp, 4)
+	incl	%ebp
+	loop	_subloop1
+
+_sub1:
+	incl	%edx
+	movl	%edx,%ecx
+	loop	_subloop2
+	jmp done
+
+	/* diff[blen:alen-1] = a[blen:alen-1] - 0 */
+_subloop2:
+	movl	(%esi, %ebp, 4), %eax
+	sbbl	$0, %eax
+	movl	%eax, (%edi, %ebp, 4)
+	INCL	%ebp
+	LOOP	_subloop2
+
+done:
+	/* Postlude */
+	movl -4(%esp), %ebx		/* restore from stack */
+	movl -8(%esp), %esi
+	movl -12(%esp), %edi
+	movl %esp, %ebp
+	leave
+	ret
+