include/asm-x86/div64.h

   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 /*
  37  * (long)X = ((long long)divs) / (long)div
  38  * (long)rem = ((long long)divs) % (long)div
  39  *
  40  * Warning, this will do an exception if X overflows.
  41  */
  42 #define div_long_long_rem(a, b, c) div_ll_X_l_rem(a, b, c)
  43
  44 static inline long div_ll_X_l_rem(long long divs, long div, long *rem)
  45 {
  46         long dum2;
  47         asm("divl %2":"=a"(dum2), "=d"(*rem)
  48             : "rm"(div), "A"(divs));
  49
  50         return dum2;
  51
  52 }
  53
  54 extern uint64_t div64_64(uint64_t dividend, uint64_t divisor);
  55
  56 #else
  57 # include <asm-generic/div64.h>
  58 #endif /* CONFIG_X86_32 */
  59
  60 #endif /* _ASM_X86_DIV64_H */