diff options
| -rw-r--r-- | arch/x86/include/asm/div64.h | 22 |
1 files changed, 14 insertions, 8 deletions
diff --git a/arch/x86/include/asm/div64.h b/arch/x86/include/asm/div64.h index 9a2d644c08ef..ced283ac79df 100644 --- a/arch/x86/include/asm/div64.h +++ b/arch/x86/include/asm/div64.h @@ -4,6 +4,7 @@ #ifdef CONFIG_X86_32 #include <linux/types.h> +#include <linux/log2.h> /* * do_div() is NOT a C function. It wants to return @@ -21,15 +22,20 @@ ({ \ unsigned long __upper, __low, __high, __mod, __base; \ __base = (base); \ - asm("":"=a" (__low), "=d" (__high) : "A" (n)); \ - __upper = __high; \ - if (__high) { \ - __upper = __high % (__base); \ - __high = __high / (__base); \ + if (__builtin_constant_p(__base) && is_power_of_2(__base)) { \ + __mod = n & (__base - 1); \ + n >>= ilog2(__base); \ + } else { \ + asm("" : "=a" (__low), "=d" (__high) : "A" (n));\ + __upper = __high; \ + if (__high) { \ + __upper = __high % (__base); \ + __high = __high / (__base); \ + } \ + asm("divl %2" : "=a" (__low), "=d" (__mod) \ + : "rm" (__base), "0" (__low), "1" (__upper)); \ + asm("" : "=A" (n) : "a" (__low), "d" (__high)); \ } \ - asm("divl %2":"=a" (__low), "=d" (__mod) \ - : "rm" (__base), "0" (__low), "1" (__upper)); \ - asm("":"=A" (n) : "a" (__low), "d" (__high)); \ __mod; \ }) |