diff options
Diffstat (limited to 'sys/lib/libkern/arch/sh/ffs.S')
| -rw-r--r-- | sys/lib/libkern/arch/sh/ffs.S | 103 |
1 files changed, 103 insertions, 0 deletions
diff --git a/sys/lib/libkern/arch/sh/ffs.S b/sys/lib/libkern/arch/sh/ffs.S new file mode 100644 index 00000000000..733694b6f80 --- /dev/null +++ b/sys/lib/libkern/arch/sh/ffs.S @@ -0,0 +1,103 @@ +/* $NetBSD: ffs.S,v 1.1 2005/12/20 19:28:50 christos Exp $ */ + +/*- + * Copyright (c) 2002 The NetBSD Foundation, Inc. + * All rights reserved. + * + * This code is derived from software contributed to The NetBSD Foundation + * by ITOH Yasufumi. + * + * 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. + * 3. All advertising materials mentioning features or use of this software + * must display the following acknowledgement: + * This product includes software developed by the NetBSD + * Foundation, Inc. and its contributors. + * 4. Neither the name of The NetBSD Foundation nor the names of its + * contributors may be used to endorse or promote products derived + * from this software without specific prior written permission. + * + * 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. + */ + +#include <machine/asm.h> + +#if defined(LIBC_SCCS) && !defined(lint) + RCSID("$NetBSD: ffs.S,v 1.1 2005/12/20 19:28:50 christos Exp $") +#endif + +/* + * ffs - find first bit set + * + * This code makes use of ``test 8bit'' and ``shift 8bit'' instructions. + * The remaining 8bit is tested in every 2bit. + */ + +ENTRY(ffs) + mov r4,r0 ! using r0 specific instructions + tst #0xff,r0 + bf/s L8bit + mov #0+1,r1 ! ret = 1..8 + + tst r0,r0 ! ffs(0) is 0 + bt Lzero ! testing here to accelerate ret=1..8 cases + + shlr8 r0 + tst #0xff,r0 + bf/s L8bit + mov #8+1,r1 ! ret = 9..16 + + shlr8 r0 + tst #0xff,r0 + bf/s L8bit + mov #16+1,r1 ! ret = 17..24 + + shlr8 r0 + mov #24+1,r1 ! ret = 25..32 + +L8bit: + tst #0x0f,r0 + bt 4f + + tst #0x03,r0 + bt 2f + tst #0x01,r0 ! not bit 0 -> T + mov #0,r0 + rts + addc r1,r0 ! 0 + r1 + T -> r0 + +2: tst #0x04,r0 + mov #2,r0 + rts + addc r1,r0 + +4: tst #0x30,r0 + bt 6f + tst #0x10,r0 + mov #4,r0 + rts + addc r1,r0 + +6: tst #0x40,r0 + mov #6,r0 + rts + addc r1,r0 + +Lzero: rts + nop |