darawin

1 files changed, 60 insertions, 0 deletions

diff --git a/src/libmp/386/mpvecsub-Darwin.s b/src/libmp/386/mpvecsub-Darwin.s
new file mode 100644
index 00000000..dcda49bf
--- /dev/null
+++ b/src/libmp/386/mpvecsub-Darwin.s
@@ -0,0 +1,60 @@
+/*	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 */
+/* (very old gnu assembler doesn't allow multiline comments) */
+
+.text
+
+.p2align 2,0x90
+.globl _mpvecsub
+_mpvecsub:
+	/* Prelude */
+	pushl %ebp		/* save on stack */
+	pushl %ebx
+	pushl %esi
+	pushl %edi
+
+	leal 20(%esp), %ebp		/* %ebp = FP for now */
+	movl	0(%ebp), %esi		/* a */
+	movl	8(%ebp), %ebx		/* b */
+	movl	4(%ebp), %edx		/* alen */
+	movl	12(%ebp), %ecx		/* blen */
+	movl	16(%ebp), %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 */
+	popl %edi
+	popl %esi
+	popl %ebx
+	popl %ebp
+	ret
+