diff options
Diffstat (limited to 'include/linux/log2.h')
| -rw-r--r-- | include/linux/log2.h | 89 |
1 files changed, 54 insertions, 35 deletions
diff --git a/include/linux/log2.h b/include/linux/log2.h index 36519e3aa3..2af7f77866 100644 --- a/include/linux/log2.h +++ b/include/linux/log2.h @@ -16,12 +16,6 @@ #include <linux/bitops.h> /* - * deal with unrepresentable constant logarithms - */ -extern __attribute__((const, noreturn)) -int ____ilog2_NaN(void); - -/* * non-constant log of base 2 calculators * - the arch may override these in asm/bitops.h if they can be implemented * more efficiently than using fls() and fls64() @@ -43,28 +37,33 @@ int __ilog2_u64(u64 n) } #endif -/* - * Determine whether some value is a power of two, where zero is +/** + * is_power_of_2() - check if a value is a power of two + * @n: the value to check + * + * Determine whether some value is a power of two, where zero is * *not* considered a power of two. + * Return: true if @n is a power of 2, otherwise false. */ - static inline __attribute__((const)) bool is_power_of_2(unsigned long n) { return (n != 0 && ((n & (n - 1)) == 0)); } -/* - * round up to nearest power of two +/** + * __roundup_pow_of_two() - round up to nearest power of two + * @n: value to round up */ static inline __attribute__((const)) unsigned long __roundup_pow_of_two(unsigned long n) { - return 1UL << fls(n - 1); + return 1UL << fls_long(n - 1); } -/* - * round down to nearest power of two +/** + * __rounddown_pow_of_two() - round down to nearest power of two + * @n: value to round down */ static inline __attribute__((const)) unsigned long __rounddown_pow_of_two(unsigned long n) @@ -73,19 +72,16 @@ unsigned long __rounddown_pow_of_two(unsigned long n) } /** - * ilog2 - log of base 2 of 32-bit or a 64-bit unsigned value - * @n - parameter - * - * constant-capable log of base 2 calculation - * - this can be used to initialise global variables from constant data, hence - * the massive ternary operator construction + * const_ilog2 - log base 2 of 32-bit or a 64-bit constant unsigned value + * @n: parameter * - * selects the appropriately-sized optimised version depending on sizeof(n) + * Use this where sparse expects a true constant expression, e.g. for array + * indices. */ -#define ilog2(n) \ +#define const_ilog2(n) \ ( \ __builtin_constant_p(n) ? ( \ - (n) < 1 ? ____ilog2_NaN() : \ + (n) < 2 ? 0 : \ (n) & (1ULL << 63) ? 63 : \ (n) & (1ULL << 62) ? 62 : \ (n) & (1ULL << 61) ? 61 : \ @@ -148,18 +144,31 @@ unsigned long __rounddown_pow_of_two(unsigned long n) (n) & (1ULL << 4) ? 4 : \ (n) & (1ULL << 3) ? 3 : \ (n) & (1ULL << 2) ? 2 : \ - (n) & (1ULL << 1) ? 1 : \ - (n) & (1ULL << 0) ? 0 : \ - ____ilog2_NaN() \ - ) : \ - (sizeof(n) <= 4) ? \ - __ilog2_u32(n) : \ - __ilog2_u64(n) \ + 1) : \ + -1) + +/** + * ilog2 - log base 2 of 32-bit or a 64-bit unsigned value + * @n: parameter + * + * constant-capable log of base 2 calculation + * - this can be used to initialise global variables from constant data, hence + * the massive ternary operator construction + * + * selects the appropriately-sized optimised version depending on sizeof(n) + */ +#define ilog2(n) \ +( \ + __builtin_constant_p(n) ? \ + const_ilog2(n) : \ + (sizeof(n) <= 4) ? \ + __ilog2_u32(n) : \ + __ilog2_u64(n) \ ) /** * roundup_pow_of_two - round the given value up to nearest power of two - * @n - parameter + * @n: parameter * * round the given value up to the nearest power of two * - the result is undefined when n == 0 @@ -176,7 +185,7 @@ unsigned long __rounddown_pow_of_two(unsigned long n) /** * rounddown_pow_of_two - round the given value down to nearest power of two - * @n - parameter + * @n: parameter * * round the given value down to the nearest power of two * - the result is undefined when n == 0 @@ -189,6 +198,12 @@ unsigned long __rounddown_pow_of_two(unsigned long n) __rounddown_pow_of_two(n) \ ) +static inline __attribute_const__ +int __order_base_2(unsigned long n) +{ + return n > 1 ? ilog2(n - 1) + 1 : 0; +} + /** * order_base_2 - calculate the (rounded up) base 2 order of the argument * @n: parameter @@ -202,7 +217,11 @@ unsigned long __rounddown_pow_of_two(unsigned long n) * ob2(5) = 3 * ... and so on. */ - -#define order_base_2(n) ilog2(roundup_pow_of_two(n)) - +#define order_base_2(n) \ +( \ + __builtin_constant_p(n) ? ( \ + ((n) == 0 || (n) == 1) ? 0 : \ + ilog2((n) - 1) + 1) : \ + __order_base_2(n) \ +) #endif /* _LINUX_LOG2_H */ |