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/*
* Copyright (c) 2006-2021, RT-Thread Development Team
*
* SPDX-License-Identifier: Apache-2.0
*
* Change Logs:
* Date Author Notes
* 2024-06-21 Zhangyan first version
*/
#include <rthw.h>
#include <rtthread.h>
#include <board.h>
#ifdef RT_USING_CPU_FFS
/**
* This function finds the first bit set (beginning with the least significant bit)
* in value and return the index of that bit.
*
* Bits are numbered starting at 1 (the least significant bit). A return value of
* zero from any of these functions means that the argument was zero.
*
* @return return the index of the first bit set. If value is 0, then this function
* shall return 0.
*/
int __rt_ffs(int value)
{
#ifdef __GNUC__
return __builtin_ffs(value);
#else
__asm__ volatile (
"rbit w1, %w0\n"
"cmp %w0, 0\n"
"clz w1, w1\n"
"csinc %w0, wzr, w1, eq\n"
: "=r"(value)
: "0"(value)
);
return value;
#endif
}
unsigned long __rt_ffsl(unsigned long value)
{
#ifdef __GNUC__
return __builtin_ffsl(value);
#else
if (!value)
{
return 0;
}
__asm__ volatile ("rbit %0, %0" : "+r" (value));
return __rt_clz(value);
#endif
}
unsigned long __rt_clz(unsigned long value)
{
#ifdef __GNUC__
return __builtin_clz(value);
#else
unsigned long val;
__asm__ volatile ("clz %0, %1"
:"=r"(val)
:"r"(value));
return val;
#endif
}
#endif /* RT_USING_CPU_FFS */
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