Module Name: src
Committed By: ad
Date: Thu Jan 16 09:23:43 UTC 2020
Modified Files:
src/common/lib/libc/arch/x86_64/string: memcmp.S
Log Message:
Back out previous, it's broken.
To generate a diff of this commit:
cvs rdiff -u -r1.4 -r1.5 src/common/lib/libc/arch/x86_64/string/memcmp.S
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/common/lib/libc/arch/x86_64/string/memcmp.S
diff -u src/common/lib/libc/arch/x86_64/string/memcmp.S:1.4 src/common/lib/libc/arch/x86_64/string/memcmp.S:1.5
--- src/common/lib/libc/arch/x86_64/string/memcmp.S:1.4 Wed Jan 15 10:56:49 2020
+++ src/common/lib/libc/arch/x86_64/string/memcmp.S Thu Jan 16 09:23:43 2020
@@ -1,34 +1,3 @@
-/* $NetBSD: memcmp.S,v 1.4 2020/01/15 10:56:49 ad Exp $ */
-
-/*-
- * Copyright (c) 2020 The NetBSD Foundation, Inc.
- * All rights reserved.
- *
- * This code is derived from software contributed to The NetBSD Foundation
- * by Andrew Doran.
- *
- * 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.
- *
- * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
- */
-
/*
* Written by J.T. Conklin <j...@netbsd.org>.
* Public domain.
@@ -38,39 +7,34 @@
#include <machine/asm.h>
#if defined(LIBC_SCCS)
- RCSID("$NetBSD: memcmp.S,v 1.4 2020/01/15 10:56:49 ad Exp $")
+ RCSID("$NetBSD: memcmp.S,v 1.5 2020/01/16 09:23:43 ad Exp $")
#endif
ENTRY(memcmp)
- movq %rdx, %rcx /* compare by longs, equality only */
- shrq $3, %rcx
- jz 2f
-1:
- movq (%rdi), %rax
- cmpq %rax, (%rsi)
- jne 6f
- decq %rcx
- leaq 8(%rdi), %rdi
- leaq 8(%rsi), %rsi
- jnz 1b
-2:
- andl $7, %edx
- jz 5f
-3:
- movb (%rdi), %al /* compare by chars, find difference */
- subb (%rsi), %al
- jne 4f
- decl %edx
- leaq 1(%rdi), %rdi
- leaq 1(%rsi), %rsi
- jnz 3b
-4:
- movsbl %al, %eax
+ movq %rdx,%rcx /* compare by longs */
+ shrq $3,%rcx
+ repe
+ cmpsq
+ jne L5 /* do we match so far? */
+
+ movq %rdx,%rcx /* compare remainder by bytes */
+ andq $7,%rcx
+ repe
+ cmpsb
+ jne L6 /* do we match? */
+
+ xorl %eax,%eax /* we match, return zero */
ret
-5:
- xorl %eax, %eax
+
+L5: movl $8,%ecx /* We know that one of the next */
+ subq %rcx,%rdi /* eight pairs of bytes do not */
+ subq %rcx,%rsi /* match. */
+ repe
+ cmpsb
+L6: xorl %eax,%eax /* Perform unsigned comparison */
+ movb -1(%rdi),%al
+ xorl %edx,%edx
+ movb -1(%rsi),%dl
+ subl %edx,%eax
ret
-6:
- movl $8, %edx
- jmp 3b
END(memcmp)
