Return to ffs.S CVS log

Up to [local] / sys / lib / libkern / arch / sh

Annotation of sys/lib/libkern/arch/sh/ffs.S, Revision 1.1

1.1     ! nbrk        1: /*     $NetBSD: ffs.S,v 1.1 2005/12/20 19:28:50 christos Exp $ */
        !             2:
        !             3: /*-
        !             4:  * Copyright (c) 2002 The NetBSD Foundation, Inc.
        !             5:  * All rights reserved.
        !             6:  *
        !             7:  * This code is derived from software contributed to The NetBSD Foundation
        !             8:  * by ITOH Yasufumi.
        !             9:  *
        !            10:  * Redistribution and use in source and binary forms, with or without
        !            11:  * modification, are permitted provided that the following conditions
        !            12:  * are met:
        !            13:  * 1. Redistributions of source code must retain the above copyright
        !            14:  *    notice, this list of conditions and the following disclaimer.
        !            15:  * 2. Redistributions in binary form must reproduce the above copyright
        !            16:  *    notice, this list of conditions and the following disclaimer in the
        !            17:  *    documentation and/or other materials provided with the distribution.
        !            18:  * 3. All advertising materials mentioning features or use of this software
        !            19:  *    must display the following acknowledgement:
        !            20:  *     This product includes software developed by the NetBSD
        !            21:  *     Foundation, Inc. and its contributors.
        !            22:  * 4. Neither the name of The NetBSD Foundation nor the names of its
        !            23:  *    contributors may be used to endorse or promote products derived
        !            24:  *    from this software without specific prior written permission.
        !            25:  *
        !            26:  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
        !            27:  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
        !            28:  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
        !            29:  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
        !            30:  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
        !            31:  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
        !            32:  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
        !            33:  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
        !            34:  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
        !            35:  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
        !            36:  * POSSIBILITY OF SUCH DAMAGE.
        !            37:  */
        !            38:
        !            39: #include <machine/asm.h>
        !            40:
        !            41: #if defined(LIBC_SCCS) && !defined(lint)
        !            42:        RCSID("$NetBSD: ffs.S,v 1.1 2005/12/20 19:28:50 christos Exp $")
        !            43: #endif
        !            44:
        !            45: /*
        !            46:  * ffs - find first bit set
        !            47:  *
        !            48:  * This code makes use of ``test 8bit'' and ``shift 8bit'' instructions.
        !            49:  * The remaining 8bit is tested in every 2bit.
        !            50:  */
        !            51:
        !            52: ENTRY(ffs)
        !            53:        mov     r4,r0           ! using r0 specific instructions
        !            54:        tst     #0xff,r0
        !            55:        bf/s    L8bit
        !            56:        mov     #0+1,r1         ! ret = 1..8
        !            57:
        !            58:        tst     r0,r0           ! ffs(0) is 0
        !            59:        bt      Lzero           ! testing here to accelerate ret=1..8 cases
        !            60:
        !            61:        shlr8   r0
        !            62:        tst     #0xff,r0
        !            63:        bf/s    L8bit
        !            64:        mov     #8+1,r1         ! ret = 9..16
        !            65:
        !            66:        shlr8   r0
        !            67:        tst     #0xff,r0
        !            68:        bf/s    L8bit
        !            69:        mov     #16+1,r1        ! ret = 17..24
        !            70:
        !            71:        shlr8   r0
        !            72:        mov     #24+1,r1        ! ret = 25..32
        !            73:
        !            74: L8bit:
        !            75:        tst     #0x0f,r0
        !            76:        bt      4f
        !            77:
        !            78:        tst     #0x03,r0
        !            79:        bt      2f
        !            80:        tst     #0x01,r0        ! not bit 0 -> T
        !            81:        mov     #0,r0
        !            82:        rts
        !            83:         addc   r1,r0           ! 0 + r1 + T -> r0
        !            84:
        !            85: 2:     tst     #0x04,r0
        !            86:        mov     #2,r0
        !            87:        rts
        !            88:         addc   r1,r0
        !            89:
        !            90: 4:     tst     #0x30,r0
        !            91:        bt      6f
        !            92:        tst     #0x10,r0
        !            93:        mov     #4,r0
        !            94:        rts
        !            95:         addc   r1,r0
        !            96:
        !            97: 6:     tst     #0x40,r0
        !            98:        mov     #6,r0
        !            99:        rts
        !           100:         addc   r1,r0
        !           101:
        !           102: Lzero: rts
        !           103:         nop