am 97288549: Merge "Let the compiler worry about implementing ffs(3)."
* commit '972885499255a9368e96332f9da0d28b2436d042': Let the compiler worry about implementing ffs(3).
This commit is contained in:
Elliott Hughes
Android Git Automerger
commit
4b83271437
@ -222,6 +222,7 @@ libc_bionic_src_files := \
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bionic/__errno.cpp \
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bionic/eventfd_read.cpp \
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bionic/eventfd_write.cpp \
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bionic/ffs.cpp \
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bionic/fork.cpp \
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bionic/futimens.cpp \
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bionic/getauxval.cpp \
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@ -4,7 +4,6 @@ _LIBC_ARCH_COMMON_SRC_FILES := \
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arch-arm/bionic/clone.S \
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arch-arm/bionic/eabi.c \
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arch-arm/bionic/_exit_with_stack_teardown.S \
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arch-arm/bionic/ffs.S \
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arch-arm/bionic/futex_arm.S \
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arch-arm/bionic/__get_sp.S \
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arch-arm/bionic/kill.S \
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@ -1,41 +0,0 @@
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/* $NetBSD: ffs.S,v 1.5 2003/04/05 23:08:52 bjh21 Exp $ */
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/*
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* Copyright (c) 2001 Christopher Gilbert
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. The name of the company nor the name of the author may be used to
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* endorse or promote products derived from this software without specific
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* prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
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* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <machine/asm.h>
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#include <machine/cpu-features.h>
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ENTRY(ffs)
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/* Standard trick to isolate bottom bit in r0 or 0 if r0 = 0 on entry */
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rsb r1, r0, #0
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ands r0, r0, r1
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clzne r0, r0
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rsbne r0, r0, #32
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bx lr
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END(ffs)
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@ -1,92 +0,0 @@
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/* $NetBSD: ffs.S,v 1.5 2003/04/05 23:08:52 bjh21 Exp $ */
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/*
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* Copyright (c) 2001 Christopher Gilbert
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. The name of the company nor the name of the author may be used to
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* endorse or promote products derived from this software without specific
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* prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
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* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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/*
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* ffs - find first set bit, this algorithm isolates the first set
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* bit, then multiplies the number by 0x0450fbaf which leaves the top
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* 6 bits as an index into the table. This algorithm should be a win
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* over the checking each bit in turn as per the C compiled version.
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*
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* This is the ffs algorithm devised by d.seal and posted to comp.sys.arm on
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* 16 Feb 1994.
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*/
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.text
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.ent ffs
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.type ffs, @function
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.global ffs
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.align 4
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.set noreorder
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ffs:
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#if (__mips==32)
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subu $t0,$0,$a0
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and $a0,$t0
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clz $t0,$a0
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li $v0,32
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j $ra
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subu $v0,$t0
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#else
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/* Size of the ffs routine in bytes
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* This is used to index .L_ffs_table from $t9
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* FIXME: there must be a better way to do this
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*/
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#define FFSSIZE 12*4
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subu $t0,$0,$a0
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and $a0,$t0
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/*
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* now a0 has at most one set bit, call this X
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* if X = 0, all further instructions are skipped
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*/
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sll $t0,$a0,4 /* t0 = X * 0x00000010 */
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or $a0,$t0 /* a0 = X * 0x00000011 */
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sll $t0,$a0,6 /* t0 = X * 0x00000440 */
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or $a0,$t0 /* a0 = X * 0x00000451 */
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sll $t0,$a0,16 /* t0 = X * 0x04510000 */
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subu $a0,$t0,$a0 /* a0 = X * 0x0450fbaf */
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/* now lookup in table indexed on top 6 bits of a0 */
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srl $a0,25
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addu $t9,$a0
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j $ra
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lbu $v0,FFSSIZE($t9)
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.L_ffs_table:
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/* 0 1 2 3 4 5 6 7 */
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.byte 0, 1, 2, 13, 3, 7, 0, 14 /* 0- 7 */
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.byte 4, 0, 8, 0, 0, 0, 0, 15 /* 8-15 */
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.byte 11, 5, 0, 0, 9, 0, 0, 26 /* 16-23 */
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.byte 0, 0, 0, 0, 0, 22, 28, 16 /* 24-31 */
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.byte 32, 12, 6, 0, 0, 0, 0, 0 /* 32-39 */
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.byte 10, 0, 0, 25, 0, 0, 21, 27 /* 40-47 */
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.byte 31, 0, 0, 0, 0, 24, 0, 20 /* 48-55 */
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.byte 30, 0, 23, 19, 29, 18, 17, 0 /* 56-63 */
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#endif
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.end ffs
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@ -1,20 +1,19 @@
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_LIBC_ARCH_COMMON_SRC_FILES := \
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arch-mips/bionic/__get_sp.S \
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arch-mips/bionic/__set_tls.c \
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arch-mips/bionic/_exit_with_stack_teardown.S \
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arch-mips/bionic/_setjmp.S \
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arch-mips/bionic/futex_mips.S \
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arch-mips/bionic/bzero.S \
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arch-mips/bionic/cacheflush.cpp \
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arch-mips/bionic/clone.S \
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arch-mips/bionic/ffs.S \
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arch-mips/bionic/_exit_with_stack_teardown.S \
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arch-mips/bionic/futex_mips.S \
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arch-mips/bionic/__get_sp.S \
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arch-mips/bionic/memcmp16.S \
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arch-mips/bionic/memmove.c \
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arch-mips/bionic/_setjmp.S \
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arch-mips/bionic/setjmp.S \
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arch-mips/bionic/__set_tls.c \
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arch-mips/bionic/sigsetjmp.S \
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arch-mips/bionic/vfork.S \
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arch-mips/string/memset.S \
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arch-mips/string/memcpy.S \
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arch-mips/string/memset.S \
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arch-mips/string/mips_strlen.c \
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_LIBC_ARCH_STATIC_SRC_FILES := \
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@ -1,18 +0,0 @@
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/* $OpenBSD: ffs.S,v 1.3 2005/08/07 11:30:38 espie Exp $ */
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/*
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* Written by J.T. Conklin <jtc@netbsd.org>.
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* Public domain.
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*/
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#include <machine/asm.h>
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ENTRY(ffs)
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bsfl 4(%esp),%eax
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jz L1 /* ZF is set if all bits are 0 */
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incl %eax /* bits numbered from 1, not 0 */
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ret
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.align 2
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L1: xorl %eax,%eax /* clear result */
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ret
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END(ffs)
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@ -9,7 +9,6 @@ _LIBC_ARCH_COMMON_SRC_FILES := \
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arch-x86/bionic/sigsetjmp.S \
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arch-x86/bionic/syscall.S \
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arch-x86/bionic/vfork.S \
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arch-x86/string/ffs.S
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ifeq ($(ARCH_X86_HAVE_SSSE3),true)
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_LIBC_ARCH_COMMON_SRC_FILES += \
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@ -1,18 +0,0 @@
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/* $OpenBSD: ffs.S,v 1.1 2004/01/28 01:44:45 mickey Exp $ */
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/*
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* Written by J.T. Conklin <jtc@netbsd.org>.
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* Public domain.
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* Adapted for NetBSD/x86_64 by Frank van der Linden <fvdl@wasabisystems.com>
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*/
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#include <machine/asm.h>
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ENTRY(ffs)
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bsfl %edi,%eax
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jz L1 /* ZF is set if all bits are 0 */
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incl %eax /* bits numbered from 1, not 0 */
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ret
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_ALIGN_TEXT
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L1: xorl %eax,%eax /* clear result */
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ret
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@ -10,7 +10,6 @@ _LIBC_ARCH_COMMON_SRC_FILES := \
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arch-x86_64/bionic/sigsetjmp.S \
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arch-x86_64/bionic/syscall.S \
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arch-x86_64/bionic/vfork.S \
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arch-x86_64/string/ffs.S \
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string/memcmp16.c \
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_LIBC_ARCH_STATIC_SRC_FILES := \
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33
libc/bionic/ffs.cpp
Normal file
33
libc/bionic/ffs.cpp
Normal file
@ -0,0 +1,33 @@
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/*
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* Copyright (C) 2013 The Android Open Source Project
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <strings.h>
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int ffs(int x) {
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return __builtin_ffs(x);
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}
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