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         unsigned long __upper, __low, __high, __mod, __base; \
  22         __base = (base); \
  23         asm("":"=a" (__low), "=d" (__high):"A" (n)); \
  24         __upper = __high; \
  25         if (__high) { \
  26                 __upper = __high % (__base); \
  27                 __high = __high / (__base); \
  28         } \
  29         asm("divl %2":"=a" (__low), "=d" (__mod):"rm" (__base), "0" (__low), "1" (__upper)); \
  30         asm("":"=A" (n):"a" (__low),"d" (__high)); \
  31         __mod; \
  32 })
  33
  34 /*
  35  * (long)X = ((long long)divs) / (long)div
  36  * (long)rem = ((long long)divs) % (long)div
  37  *
  38  * Warning, this will do an exception if X overflows.
  39  */
  40 #define div_long_long_rem(a,b,c) div_ll_X_l_rem(a,b,c)
  41
  42 static inline long
  43 div_ll_X_l_rem(long long divs, long div, long *rem)
  44 {
  45         long dum2;
  46       __asm__("divl %2":"=a"(dum2), "=d"(*rem)
  47       : "rm"(div), "A"(divs));
  48
  49         return dum2;
  50
  51 }
  52
  53 extern uint64_t div64_64(uint64_t dividend, uint64_t divisor);
  54
  55 #else
  56 # include <asm-generic/div64.h>
  57 #endif /* CONFIG_X86_32 */
  58
  59 #endif /* _ASM_X86_DIV64_H */