diff options
Diffstat (limited to 'libc/arch-arm/bionic/ffs.S')
| -rw-r--r-- | libc/arch-arm/bionic/ffs.S | 82 |
1 files changed, 0 insertions, 82 deletions
diff --git a/libc/arch-arm/bionic/ffs.S b/libc/arch-arm/bionic/ffs.S deleted file mode 100644 index f11141c..0000000 --- a/libc/arch-arm/bionic/ffs.S +++ /dev/null @@ -1,82 +0,0 @@ -/* $NetBSD: ffs.S,v 1.5 2003/04/05 23:08:52 bjh21 Exp $ */ -/* - * Copyright (c) 2001 Christopher Gilbert - * All rights reserved. - * - * 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. The name of the company nor the name of the author may be used to - * endorse or promote products derived from this software without specific - * prior written permission. - * - * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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> - -/* - * ffs - find first set bit, this algorithm isolates the first set - * bit, then multiplies the number by 0x0450fbaf which leaves the top - * 6 bits as an index into the table. This algorithm should be a win - * over the checking each bit in turn as per the C compiled version. - * - * under ARMv5 there's an instruction called CLZ (count leading Zero's) that - * could be used - * - * This is the ffs algorithm devised by d.seal and posted to comp.sys.arm on - * 16 Feb 1994. - */ - -ENTRY(ffs) - /* Standard trick to isolate bottom bit in r0 or 0 if r0 = 0 on entry */ - rsb r1, r0, #0 - ands r0, r0, r1 -#ifndef __ARM_ARCH_5__ - /* - * now r0 has at most one set bit, call this X - * if X = 0, all further instructions are skipped - */ - adrne r2, .L_ffs_table - orrne r0, r0, r0, lsl #4 /* r0 = X * 0x11 */ - orrne r0, r0, r0, lsl #6 /* r0 = X * 0x451 */ - rsbne r0, r0, r0, lsl #16 /* r0 = X * 0x0450fbaf */ - - /* now lookup in table indexed on top 6 bits of r0 */ - ldrneb r0, [ r2, r0, lsr #26 ] - - bx lr - -.text; -.type .L_ffs_table, _ASM_TYPE_OBJECT; -.L_ffs_table: -/* 0 1 2 3 4 5 6 7 */ - .byte 0, 1, 2, 13, 3, 7, 0, 14 /* 0- 7 */ - .byte 4, 0, 8, 0, 0, 0, 0, 15 /* 8-15 */ - .byte 11, 5, 0, 0, 9, 0, 0, 26 /* 16-23 */ - .byte 0, 0, 0, 0, 0, 22, 28, 16 /* 24-31 */ - .byte 32, 12, 6, 0, 0, 0, 0, 0 /* 32-39 */ - .byte 10, 0, 0, 25, 0, 0, 21, 27 /* 40-47 */ - .byte 31, 0, 0, 0, 0, 24, 0, 20 /* 48-55 */ - .byte 30, 0, 23, 19, 29, 18, 17, 0 /* 56-63 */ -#else - clzne r0, r0 - rsbne r0, r0, #32 - bx lr -#endif - |