Initially cloned from bcmp.S.

lib/libc/arch/m68k/string/memcmp.S

@@ -0,0 +1,100 @@
+/*-
+ * Copyright (c) 1990 The Regents of the University of California.
+ * All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * the Systems Programming Group of the University of Utah Computer
+ * Science Department.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ *	This product includes software developed by the University of
+ *	California, Berkeley and its contributors.
+ * 4. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#if defined(LIBC_SCCS) && !defined(lint)
+	.text
+	/*.asciz "from: @(#)bcmp.s	5.1 (Berkeley) 5/12/90"*/
+	.asciz "$Id: memcmp.S,v 1.1 1993/12/06 22:37:15 mycroft Exp $"
+#endif /* LIBC_SCCS and not lint */
+
+/* memcmp(s1, s2, n) */
+
+#include "DEFS.h"
+
+/*
+ * This is probably not the best we can do, but it is still 2-10 times
+ * faster than the C version in the portable gen directory.
+ *
+ * Things that might help:
+ *	- longword align when possible (only on the 68020)
+ *	- use nested DBcc instructions or use one and limit size to 64K
+ */
+ENTRY(memcmp)
+	movl	sp@(4),a0	/* string 1 */
+	movl	sp@(8),a1	/* string 2 */
+	movl	sp@(12),d0	/* length */
+	jeq	bcdone		/* if zero, nothing to do */
+	movl	a0,d1
+	btst	#0,d1		/* string 1 address odd? */
+	jeq	bceven		/* no, skip alignment */
+	cmpmb	a0@+,a1@+	/* yes, compare a byte */
+	jne	bcnoteq		/* not equal, return non-zero */
+	subql	#1,d0		/* adjust count */
+	jeq	bcdone		/* count 0, reutrn zero */
+bceven:
+	movl	a1,d1
+	btst	#0,d1		/* string 2 address odd? */
+	jne	bcbloop		/* yes, no hope for alignment, compare bytes */
+	movl	d0,d1		/* no, both even */
+	lsrl	#2,d1		/* convert count to longword count */
+	jeq	bcbloop		/* count 0, skip longword loop */
+bclloop:
+	cmpml	a0@+,a1@+	/* compare a longword */
+	jne	bcnoteql	/* not equal, return non-zero */
+	subql	#1,d1		/* adjust count */
+	jne	bclloop		/* still more, keep comparing */
+	andl	#3,d0		/* what remains */
+	jeq	bcdone		/* nothing, all done */
+bcbloop:
+	cmpmb	a0@+,a1@+	/* compare a byte */
+	jne	bcnoteq		/* not equal, return non-zero */
+	subql	#1,d0		/* adjust count */
+	jne	bcbloop		/* still more, keep going */
+	rts
+bcnoteql:
+	subql	#4,a0
+	subql	#4,a1
+	movl	#4,d0
+	jra	bcbloop
+bcnoteq:
+	clrl	d0
+	clrl	d1
+	movb	a0@-,d0
+	movb	a1@-,d1
+	subql	d1,d0
+bcdone:
+	rts