Line data    Source code

       1            0 : /*
       2              :  * Copyright (c) 2015, Wind River Systems, Inc.
       3              :  * Copyright (c) 2017, Oticon A/S
       4              :  *
       5              :  * SPDX-License-Identifier: Apache-2.0
       6              :  */
       7              : 
       8              : #ifndef ZEPHYR_INCLUDE_ARCH_COMMON_FFS_H_
       9              : #define ZEPHYR_INCLUDE_ARCH_COMMON_FFS_H_
      10              : 
      11              : #ifndef _ASMLANGUAGE
      12              : 
      13              : #include <zephyr/types.h>
      14              : #include <zephyr/toolchain.h>
      15              : 
      16              : #ifdef __cplusplus
      17              : extern "C" {
      18              : #endif
      19              : 
      20              : /**
      21              :  *
      22              :  * @brief find most significant bit set in a 32-bit word
      23              :  *
      24              :  * This routine finds the first bit set starting from the most significant bit
      25              :  * in the argument passed in and returns the index of that bit.  Bits are
      26              :  * numbered starting at 1 from the least significant bit.  A return value of
      27              :  * zero indicates that the value passed is zero.
      28              :  *
      29              :  * @return most significant bit set, 0 if @a op is 0
      30              :  */
      31              : 
      32            1 : static ALWAYS_INLINE unsigned int find_msb_set(uint32_t op)
      33              : {
      34              :         if (op == 0) {
      35              :                 return 0;
      36              :         }
      37              : 
      38              :         return 32 - __builtin_clz(op);
      39              : }
      40              : 
      41              : 
      42              : /**
      43              :  *
      44              :  * @brief find least significant bit set in a 32-bit word
      45              :  *
      46              :  * This routine finds the first bit set starting from the least significant bit
      47              :  * in the argument passed in and returns the index of that bit.  Bits are
      48              :  * numbered starting at 1 from the least significant bit.  A return value of
      49              :  * zero indicates that the value passed is zero.
      50              :  *
      51              :  * @return least significant bit set, 0 if @a op is 0
      52              :  */
      53              : 
      54            1 : static ALWAYS_INLINE unsigned int find_lsb_set(uint32_t op)
      55              : {
      56              : #ifdef CONFIG_TOOLCHAIN_HAS_BUILTIN_FFS
      57              :         return __builtin_ffs(op);
      58              : 
      59              : #else
      60              :         /*
      61              :          * Toolchain does not have __builtin_ffs(). Leverage find_lsb_set()
      62              :          * by first clearing all but the lowest set bit.
      63              :          */
      64              : 
      65              :         op = op ^ (op & (op - 1));
      66              : 
      67              :         return find_msb_set(op);
      68              : #endif /* CONFIG_TOOLCHAIN_HAS_BUILTIN_FFS */
      69              : }
      70              : 
      71              : #ifdef __cplusplus
      72              : }
      73              : #endif
      74              : 
      75              : #endif /* _ASMLANGUAGE */
      76              : 
      77              : #endif /* ZEPHYR_INCLUDE_ARCH_COMMON_FFS_H_ */