135 lines
4.6 KiB
ArmAsm
135 lines
4.6 KiB
ArmAsm
/* ffs.s - find first set bit APIs for IA-32 architecture */
|
|
|
|
/*
|
|
* Copyright (c) 2011-2014 Wind River Systems, Inc.
|
|
*
|
|
* 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) Neither the name of Wind River Systems 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 COPYRIGHT HOLDERS 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 COPYRIGHT HOLDER 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.
|
|
*/
|
|
|
|
/*
|
|
DESCRIPTION
|
|
This module implements the ffsMsb() and ffsLsb() functions for the IA-32
|
|
architecture.
|
|
|
|
INTERNAL
|
|
Inline versions of these APIs, find_last_set_inline() and find_first_set_inline(),
|
|
are defined in arch.h.
|
|
*/
|
|
|
|
#define _ASMLANGUAGE
|
|
|
|
#include <nanokernel/x86/asm.h>
|
|
#include <offsets.h> /* nanokernel structure offset definitions */
|
|
|
|
|
|
/* exports (public APIs) */
|
|
|
|
GTEXT(find_last_set)
|
|
GTEXT(find_first_set)
|
|
|
|
/*******************************************************************************
|
|
*
|
|
* find_first_set - find first set bit searching from the LSB
|
|
*
|
|
* This routine finds the first bit set in the passed argument and
|
|
* returns the index of that bit. Bits are numbered starting
|
|
* at 1 from the least significant bit to 32 for the most significant bit.
|
|
* A return value of zero indicates that the value passed is zero.
|
|
*
|
|
* RETURNS: bit position from 1 to 32, or 0 if the argument is zero.
|
|
*
|
|
* INTERNAL
|
|
* For Intel64 (x86_64) architectures, the 'cmovz' can be removed
|
|
* and leverage the fact that the 'bsrl' doesn't modify the destination operand
|
|
* when the source operand is zero. The "bitpos" variable can be preloaded
|
|
* into the destination register, and given the unconditional ++bitpos that
|
|
* is performed after the 'cmovz', the correct results are yielded.
|
|
*/
|
|
|
|
SECTION_FUNC(TEXT, find_first_set)
|
|
|
|
#if !defined(CONFIG_CMOV_UNSUPPORTED)
|
|
|
|
movl $0xffffffff, %ecx /* preload for 0 return value */
|
|
bsfl 0x4(%esp), %eax /* bit scan "forward" */
|
|
cmovz %ecx, %eax /* if operand == 0 then %ecx -> eax */
|
|
addl $1, %eax
|
|
ret
|
|
|
|
#else
|
|
|
|
bsfl 0x4(%esp), %eax /* bit scan "forward" */
|
|
jnz ffsLsb_argNotZero
|
|
xorl %eax, %eax /* return 0 when arg=0 */
|
|
ret
|
|
|
|
BRANCH_LABEL(ffsLsb_argNotZero) /* this label serves find_first_set() & find_last_set() */
|
|
addl $1, %eax
|
|
ret
|
|
|
|
#endif /* !CONFIG_CMOV_UNSUPPORTED */
|
|
|
|
|
|
/*******************************************************************************
|
|
*
|
|
* find_last_set - find first set bit searching from the MSB
|
|
*
|
|
* This routine finds the first bit set in the passed argument and
|
|
* returns the index of that bit. Bits are numbered starting
|
|
* at 1 from the least significant bit to 32 for the most significant bit.
|
|
* A return value of zero indicates that the value passed is zero.
|
|
*
|
|
* RETURNS: bit position from 1 to 32, or 0 if the argument is zero.
|
|
*
|
|
* INTERNAL
|
|
* For Intel64 (x86_64) architectures, the 'cmovz' can be removed
|
|
* and leverage the fact that the 'bsfl' doesn't modify the destination operand
|
|
* when the source operand is zero. The "bitpos" variable can be preloaded
|
|
* into the destination register, and given the unconditional ++bitpos that
|
|
* is performed after the 'cmovz', the correct results are yielded.
|
|
*/
|
|
|
|
SECTION_FUNC(TEXT, find_last_set)
|
|
|
|
#if !defined(CONFIG_CMOV_UNSUPPORTED)
|
|
|
|
movl $0xffffffff, %ecx /* preload for 0 return value */
|
|
bsrl 0x4(%esp), %eax /* bit scan "reverse" */
|
|
cmovz %ecx, %eax /* if operand == 0 then %ecx -> eax */
|
|
addl $1, %eax
|
|
ret
|
|
|
|
#else
|
|
|
|
bsrl 0x4(%esp), %eax /* bit scan "reverse" */
|
|
jnz ffsLsb_argNotZero
|
|
xorl %eax, %eax /* return 0 when arg=0 */
|
|
ret
|
|
|
|
#endif /* !CONFIG_CMOV_UNSUPPORTED */
|
|
|