include/asm-i386/div64.h

   1 #ifndef __I386_DIV64
   2 #define __I386_DIV64
   3
   4 /*
   5  * do_div() is NOT a C function. It wants to return
   6  * two values (the quotient and the remainder), but
   7  * since that doesn't work very well in C, what it
   8  * does is:
   9  *
  10  * - modifies the 64-bit dividend _in_place_
  11  * - returns the 32-bit remainder
  12  *
  13  * This ends up being the most efficient "calling
  14  * convention" on x86.
  15  */
  16 #define do_div(n,base) ({ \
  17         unsigned long __upper, __low, __high, __mod, __base; \
  18         __base = (base); \
  19         asm("":"=a" (__low), "=d" (__high):"A" (n)); \
  20         __upper = __high; \
  21         if (__high) { \
  22                 __upper = __high % (__base); \
  23                 __high = __high / (__base); \
  24         } \
  25         asm("divl %2":"=a" (__low), "=d" (__mod):"rm" (__base), "0" (__low), "1" (__upper)); \
  26         asm("":"=A" (n):"a" (__low),"d" (__high)); \
  27         __mod; \
  28 })
  29
  30 /*
  31  * (long)X = ((long long)divs) / (long)div
  32  * (long)rem = ((long long)divs) % (long)div
  33  *
  34  * Warning, this will do an exception if X overflows.
  35  */
  36 #define div_long_long_rem(a,b,c) div_ll_X_l_rem(a,b,c)
  37
  38 extern inline long
  39 div_ll_X_l_rem(long long divs, long div, long *rem)
  40 {
  41         long dum2;
  42       __asm__("divl %2":"=a"(dum2), "=d"(*rem)
  43       : "rm"(div), "A"(divs));
  44
  45         return dum2;
  46
  47 }
  48 #endif