diff options
Diffstat (limited to 'lib/math/gcd.c')
| -rw-r--r-- | lib/math/gcd.c | 27 |
1 files changed, 15 insertions, 12 deletions
diff --git a/lib/math/gcd.c b/lib/math/gcd.c index e3b042214d1b..62efca6787ae 100644 --- a/lib/math/gcd.c +++ b/lib/math/gcd.c @@ -11,22 +11,16 @@ * has decent hardware division. */ +DEFINE_STATIC_KEY_TRUE(efficient_ffs_key); + #if !defined(CONFIG_CPU_NO_EFFICIENT_FFS) /* If __ffs is available, the even/odd algorithm benchmarks slower. */ -/** - * gcd - calculate and return the greatest common divisor of 2 unsigned longs - * @a: first value - * @b: second value - */ -unsigned long gcd(unsigned long a, unsigned long b) +static unsigned long binary_gcd(unsigned long a, unsigned long b) { unsigned long r = a | b; - if (!a || !b) - return r; - b >>= __ffs(b); if (b == 1) return r & -r; @@ -44,9 +38,15 @@ unsigned long gcd(unsigned long a, unsigned long b) } } -#else +#endif /* If normalization is done by loops, the even/odd algorithm is a win. */ + +/** + * gcd - calculate and return the greatest common divisor of 2 unsigned longs + * @a: first value + * @b: second value + */ unsigned long gcd(unsigned long a, unsigned long b) { unsigned long r = a | b; @@ -54,6 +54,11 @@ unsigned long gcd(unsigned long a, unsigned long b) if (!a || !b) return r; +#if !defined(CONFIG_CPU_NO_EFFICIENT_FFS) + if (static_branch_likely(&efficient_ffs_key)) + return binary_gcd(a, b); +#endif + /* Isolate lsbit of r */ r &= -r; @@ -80,6 +85,4 @@ unsigned long gcd(unsigned long a, unsigned long b) } } -#endif - EXPORT_SYMBOL_GPL(gcd); |