include/asm-i386/div64.h

   1 #ifndef __I386_DIV64
   2 #define __I386_DIV64
   3
   4 #include <linux/types.h>
   5
   6 /*
   7  * do_div() is NOT a C function. It wants to return
   8  * two values (the quotient and the remainder), but
   9  * since that doesn't work very well in C, what it
  10  * does is:
  11  *
  12  * - modifies the 64-bit dividend _in_place_
  13  * - returns the 32-bit remainder
  14  *
  15  * This ends up being the most efficient "calling
  16  * convention" on x86.
  17  */
  18 #define do_div(n,base) ({ \
  19         unsigned long __upper, __low, __high, __mod, __base; \
  20         __base = (base); \
  21         asm("":"=a" (__low), "=d" (__high):"A" (n)); \
  22         __upper = __high; \
  23         if (__high) { \
  24                 __upper = __high % (__base); \
  25                 __high = __high / (__base); \
  26         } \
  27         asm("divl %2":"=a" (__low), "=d" (__mod):"rm" (__base), "0" (__low), "1" (__upper)); \
  28         asm("":"=A" (n):"a" (__low),"d" (__high)); \
  29         __mod; \
  30 })
  31
  32 /*
  33  * (long)X = ((long long)divs) / (long)div
  34  * (long)rem = ((long long)divs) % (long)div
  35  *
  36  * Warning, this will do an exception if X overflows.
  37  */
  38 #define div_long_long_rem(a,b,c) div_ll_X_l_rem(a,b,c)
  39
  40 static inline long
  41 div_ll_X_l_rem(long long divs, long div, long *rem)
  42 {
  43         long dum2;
  44       __asm__("divl %2":"=a"(dum2), "=d"(*rem)
  45       : "rm"(div), "A"(divs));
  46
  47         return dum2;
  48
  49 }
  50
  51 extern uint64_t div64_64(uint64_t dividend, uint64_t divisor);
  52 #endif