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      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) /* (void *s, uchar_t c, size_t n) */
     59 	movl	%esi, %eax	/ move "c" to %eax
     60 	cmpq	$4, %rdx	/ if number of bytes < 4
     61 	jb	.L1		/ goto .L1
     62 	testq	$3, %rdi	/ if %rdi not word aligned
     63 	jnz	.L2		/ goto .L2
     64 	.align	4
     65 .L3:
     66 	movl	(%rdi), %ecx	/ move 1 word from (%rdi) to %ecx
     67 	cmpb	%cl, %al	/ if the first byte is %al
     68 	je	.L4		/ goto .L4 (found)
     69 	cmpb	%ch, %al	/ if the second byte is %al
     70 	je	.L5		/ goto .L5 (found)
     71 	shrl	$16, %ecx	/ right shift 16-bit
     72 	cmpb	%cl, %al	/ if the third byte is %al
     73 	je	.L6		/ goto .L6 (found)
     74 	cmpb	%ch, %al	/ if the fourth is %al
     75 	je	.L7		/ goto .L7 (found)
     76 	subq	$4, %rdx	/ decrement number of bytes by 4
     77 	addq	$4, %rdi	/ next word
     78 	cmpq	$4, %rdx	/ if number of bytes >= 4
     79 	jae	.L3		/ goto .L3
     80 .L1:
     81 	cmpq	$0, %rdx	/ if number of bytes == 0
     82 	jz	.L8		/ goto .L8 (not found)
     83 	cmpb	(%rdi), %al	/ if a byte in (%rdi) is %al
     84 	je	.L4		/ goto .L4 (found)
     85 	decq	%rdx		/ decrement number of bytes by 1
     86 	incq	%rdi		/ next byte
     87 	jmp	.L1		/ goto .L1
     88 	.align	4
     89 .L8:
     90 	xorl	%eax, %eax	/ not found
     91 	ret			/ return (0)
     92 	.align	4
     93 .L2:
     94 	cmpq	$0, %rdx	/ if number of bytes == 0
     95 	jz	.L8		/ goto .L8 (not found)
     96 	cmpb	(%rdi), %al	/ if a byte in (%rdi) is %al
     97 	je	.L4		/ goto .L4 (found)
     98 	incq	%rdi		/ next byte
     99 	decq	%rdx		/ decrement number of bytes by 1
    100 	testq	$3, %rdi	/ if %rdi not word aligned
    101 	jnz	.L2		/ goto .L2
    102 	cmpq	$4, %rdx	/ if number of bytes >= 4
    103 	jae	.L3		/ goto .L3 (word aligned)
    104 	jmp	.L1		/ goto .L1
    105 	.align	4
    106 .L7:
    107 	/ found at the fourth byte
    108 	incq	%rdi
    109 .L6:
    110 	/ found at the third byte
    111 	incq	%rdi
    112 .L5:
    113 	/ found at the second byte
    114 	incq	%rdi
    115 .L4:
    116 	/ found at the first byte
    117 	movq	%rdi,%rax
    118 	ret
    119 	SET_SIZE(memchr)
    120