xref: /illumos-gate/usr/src/lib/libc/i386/gen/memchr.s (revision 9a70fc3b)
1/*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21/*
22 * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
23 * Use is subject to license terms.
24 */
25
26	.file	"memchr.s"
27
28/
29/ memchr(sptr, c1, n)
30/
31/ Returns the pointer in sptr at which the character c1 appears;
32/ or NULL if not found in chars; doesn't stop at \0.
33/
34/ Fast assembly language version of the following C-program memchr
35/ which represents the `standard' for the C-library.
36/
37/	void *
38/	memchr(const void *sptr, int c1, size_t n)
39/	{
40/		if (n != 0) {
41/			unsigned char	c = (unsigned char)c1;
42/			const unsigned char	*sp = sptr;
43/
44/			do {
45/				if (*sp++ == c)
46/					return ((void *)--sp);
47/			} while (--n != 0);
48/		}
49/		return (NULL);
50/	}
51/
52
53#include "SYS.h"
54
55	.globl	memchr
56	.align	4
57
58	ENTRY(memchr)
59	pushl	%edi		/ save register variable
60	movl	8(%esp), %eax	/ %eax = string address
61	movl	12(%esp), %ecx	/ %cl = byte that is sought
62	movl	16(%esp), %edi	/ %edi = number of bytes
63	cmpl	$4, %edi	/ if number of bytes < 4
64	jb	.L1		/ goto .L1
65	testl	$3, %eax	/ if %eax not word aligned
66	jnz	.L2		/ goto .L2
67	.align	4
68.L3:
69	movl	(%eax), %edx	/ move 1 word from (%eax) to %edx
70	cmpb	%dl, %cl	/ if the first byte is %cl
71	je	.L4		/ goto .L4 (found)
72	cmpb	%dh, %cl	/ if the second byte is %cl
73	je	.L5		/ goto .L5 (found)
74	shrl	$16, %edx	/ right shift 16-bit
75	cmpb	%dl, %cl	/ if the third byte is %cl
76	je	.L6		/ goto .L6 (found)
77	cmpb	%dh, %cl	/ if the fourth is %cl
78	je	.L7		/ goto .L7 (found)
79	subl	$4, %edi	/ decrement number of bytes by 4
80	addl	$4, %eax	/ next word
81	cmpl	$4, %edi	/ if number of bytes >= 4
82	jae	.L3		/ goto .L3
83.L1:
84	cmpl	$0, %edi	/ if number of bytes == 0
85	jz	.L8		/ goto .L8 (not found)
86	cmpb	(%eax), %cl	/ if a byte in (%eax) is %cl
87	je	.L4		/ goto .L4 (found)
88	decl	%edi		/ decrement number of bytes by 1
89	incl	%eax		/ next byte
90	jmp	.L1		/ goto .L1
91	.align	4
92.L8:
93	xorl	%eax, %eax	/ not found
94	popl	%edi		/ restore register
95	ret			/ return (0)
96	.align	4
97.L2:
98	cmpl	$0, %edi	/ if number of bytes == 0
99	jz	.L8		/ goto .L8 (not found)
100	cmpb	(%eax), %cl	/ if a byte in (%eax) is %cl
101	je	.L4		/ goto .L4 (found)
102	incl	%eax		/ next byte
103	decl	%edi		/ decrement number of bytes by 1
104	testl	$3, %eax	/ if %eax not word aligned
105	jnz	.L2		/ goto .L2
106	cmpl	$4, %edi	/ if number of bytes >= 4
107	jae	.L3		/ goto .L3 (word aligned)
108	jmp	.L1		/ goto .L1
109	.align	4
110.L7:
111	/ found at the fourth byte
112	incl	%eax
113.L6:
114	/ found at the third byte
115	incl	%eax
116.L5:
117	/ found at the second byte
118	incl	%eax
119.L4:
120	/ found at the first byte
121	popl	%edi		/ restore register variable
122	ret
123	SET_SIZE(memchr)
124