1 #ifndef _ASM_X86_DIV64_H 2 #define _ASM_X86_DIV64_H 3 4 #ifdef CONFIG_X86_32 5 6 #include <linux/types.h> 7 #include <linux/log2.h> 8 9 /* 10 * do_div() is NOT a C function. It wants to return 11 * two values (the quotient and the remainder), but 12 * since that doesn't work very well in C, what it 13 * does is: 14 * 15 * - modifies the 64-bit dividend _in_place_ 16 * - returns the 32-bit remainder 17 * 18 * This ends up being the most efficient "calling 19 * convention" on x86. 20 */ 21 #define do_div(n, base) \ 22 ({ \ 23 unsigned long __upper, __low, __high, __mod, __base; \ 24 __base = (base); \ 25 if (__builtin_constant_p(__base) && is_power_of_2(__base)) { \ 26 __mod = n & (__base - 1); \ 27 n >>= ilog2(__base); \ 28 } else { \ 29 asm("" : "=a" (__low), "=d" (__high) : "A" (n));\ 30 __upper = __high; \ 31 if (__high) { \ 32 __upper = __high % (__base); \ 33 __high = __high / (__base); \ 34 } \ 35 asm("divl %2" : "=a" (__low), "=d" (__mod) \ 36 : "rm" (__base), "0" (__low), "1" (__upper)); \ 37 asm("" : "=A" (n) : "a" (__low), "d" (__high)); \ 38 } \ 39 __mod; \ 40 }) 41 42 static inline u64 div_u64_rem(u64 dividend, u32 divisor, u32 *remainder) 43 { 44 union { 45 u64 v64; 46 u32 v32[2]; 47 } d = { dividend }; 48 u32 upper; 49 50 upper = d.v32[1]; 51 d.v32[1] = 0; 52 if (upper >= divisor) { 53 d.v32[1] = upper / divisor; 54 upper %= divisor; 55 } 56 asm ("divl %2" : "=a" (d.v32[0]), "=d" (*remainder) : 57 "rm" (divisor), "0" (d.v32[0]), "1" (upper)); 58 return d.v64; 59 } 60 #define div_u64_rem div_u64_rem 61 62 #else 63 # include <asm-generic/div64.h> 64 #endif /* CONFIG_X86_32 */ 65 66 #endif /* _ASM_X86_DIV64_H */ 67