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             : 
      15             : #ifdef __cplusplus
      16             : extern "C" {
      17             : #endif
      18             : 
      19             : /**
      20             :  *
      21             :  * @brief find most significant bit set in a 32-bit word
      22             :  *
      23             :  * This routine finds the first bit set starting from the most significant bit
      24             :  * in the argument passed in and returns the index of that bit.  Bits are
      25             :  * numbered starting at 1 from the least significant bit.  A return value of
      26             :  * zero indicates that the value passed is zero.
      27             :  *
      28             :  * @return most significant bit set, 0 if @a op is 0
      29             :  */
      30             : 
      31           1 : static ALWAYS_INLINE unsigned int find_msb_set(uint32_t op)
      32             : {
      33             :         if (op == 0) {
      34             :                 return 0;
      35             :         }
      36             : 
      37             :         return 32 - __builtin_clz(op);
      38             : }
      39             : 
      40             : 
      41             : /**
      42             :  *
      43             :  * @brief find least significant bit set in a 32-bit word
      44             :  *
      45             :  * This routine finds the first bit set starting from the least significant bit
      46             :  * in the argument passed in and returns the index of that bit.  Bits are
      47             :  * numbered starting at 1 from the least significant bit.  A return value of
      48             :  * zero indicates that the value passed is zero.
      49             :  *
      50             :  * @return least significant bit set, 0 if @a op is 0
      51             :  */
      52             : 
      53           1 : static ALWAYS_INLINE unsigned int find_lsb_set(uint32_t op)
      54             : {
      55             : #ifdef CONFIG_TOOLCHAIN_HAS_BUILTIN_FFS
      56             :         return __builtin_ffs(op);
      57             : 
      58             : #else
      59             :         /*
      60             :          * Toolchain does not have __builtin_ffs(). Leverage find_lsb_set()
      61             :          * by first clearing all but the lowest set bit.
      62             :          */
      63             : 
      64             :         op = op ^ (op & (op - 1));
      65             : 
      66             :         return find_msb_set(op);
      67             : #endif /* CONFIG_TOOLCHAIN_HAS_BUILTIN_FFS */
      68             : }
      69             : 
      70             : #ifdef __cplusplus
      71             : }
      72             : #endif
      73             : 
      74             : #endif /* _ASMLANGUAGE */
      75             : 
      76             : #endif /* ZEPHYR_INCLUDE_ARCH_COMMON_FFS_H_ */