/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

        .file   "strrchr.s"

/
/ strrchr(sp, c)
/
/ Returns the pointer in sp at which the character c last
/ appears; NULL if no found
/
/ Fast assembly language version of the following C-program strrchr
/ which represents the `standard' for the C-library.
/
/       char *
/       strrchr(const char *sp, int c)
/       {
/               char    *r = NULL;
/
/               do {
/                       if (*sp == (char)c)
/                               r = (char *)sp;
/               } while (*sp++);
/
/               return (r);
/       }
/

#include "SYS.h"

        ENTRY(strrchr)          /* (char *s, int c) */
        movl    $0, %eax        / %rax = NULL (current occurrence)
        movl    %esi, %ecx      / %cl == char to search for
        testq   $3, %rdi        / if %rdi not word aligned
        jnz     .L1             / goto .L1
        .align  4
.L3:
        movl    (%rdi), %edx    / move 1 word from (%rdi) to %edx
        cmpb    %cl, %dl        / if the fist byte is not %cl
        jne     .L4             / goto .L4
        movq    %rdi, %rax      / save this address to %rax
.L4:
        cmpb    $0, %dl         / if a null termination
        je      .L8             / goto .L8

        cmpb    %cl, %dh        / if the second byte is not %cl
        jne     .L5             / goto .L5
        leaq    1(%rdi), %rax   / save this address to %rax
.L5:
        cmpb    $0, %dh         / if a null termination
        je      .L8             / goto .L8

        shrl    $16, %edx       / right shift 16-bit
        cmpb    %cl, %dl        / if the third byte is not %cl
        jne     .L6             / goto .L6
        leaq    2(%rdi), %rax   / save this address to %rax
.L6:
        cmpb    $0, %dl         / if a null termination
        je      .L8             / goto .L8

        cmpb    %cl, %dh        / if the fourth byte is not %cl
        jne     .L7             / goto .L7
        leaq    3(%rdi), %rax   / save this address to %rax
.L7:
        cmpb    $0, %dh         / if a null termination
        je      .L8             / goto .L8

        addq    $4, %rdi        / next word
        jmp     .L3             / goto .L3
        .align  4
.L1:
        movb    (%rdi), %dl     / move 1 byte from (%rdi) to %dl
        cmpb    %cl, %dl        / if %dl is not %cl
        jne     .L2             / goto .L2
        movq    %rdi, %rax      / save this address to %rax
.L2:
        cmpb    $0, %dl         / if a null termination
        je      .L8             / goto .L8

        incq    %rdi            / next byte
        testq   $3, %rdi        / if %rdi not word aligned
        jnz     .L1             / goto .L1
        jmp     .L3             / goto .L3 (word aligned)
        .align  4
.L8:
        ret                     / %rax points to the last occurrence or NULL
        SET_SIZE(strrchr)