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