LXR linux/arch/x86/include/asm/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#include <linux/log2.h>
   8
   9/*
  10 * do_div() is NOT a C function. It wants to return
  11 * two values (the quotient and the remainder), but
  12 * since that doesn't work very well in C, what it
  13 * does is:
  14 *
  15 * - modifies the 64-bit dividend _in_place_
  16 * - returns the 32-bit remainder
  17 *
  18 * This ends up being the most efficient "calling
  19 * convention" on x86.
  20 */
  21#define do_div(n, base)                                         \
  22({                                                              \
  23        unsigned long __upper, __low, __high, __mod, __base;    \
  24        __base = (base);                                        \
  25        if (__builtin_constant_p(__base) && is_power_of_2(__base)) { \
  26                __mod = n & (__base - 1);                       \
  27                n >>= ilog2(__base);                            \
  28        } else {                                                \
  29                asm("" : "=a" (__low), "=d" (__high) : "A" (n));\
  30                __upper = __high;                               \
  31                if (__high) {                                   \
  32                        __upper = __high % (__base);            \
  33                        __high = __high / (__base);             \
  34                }                                               \
  35                asm("divl %2" : "=a" (__low), "=d" (__mod)      \
  36                        : "rm" (__base), "0" (__low), "1" (__upper));   \
  37                asm("" : "=A" (n) : "a" (__low), "d" (__high)); \
  38        }                                                       \
  39        __mod;                                                  \
  40})
  41
  42static inline u64 div_u64_rem(u64 dividend, u32 divisor, u32 *remainder)
  43{
  44        union {
  45                u64 v64;
  46                u32 v32[2];
  47        } d = { dividend };
  48        u32 upper;
  49
  50        upper = d.v32[1];
  51        d.v32[1] = 0;
  52        if (upper >= divisor) {
  53                d.v32[1] = upper / divisor;
  54                upper %= divisor;
  55        }
  56        asm ("divl %2" : "=a" (d.v32[0]), "=d" (*remainder) :
  57                "rm" (divisor), "0" (d.v32[0]), "1" (upper));
  58        return d.v64;
  59}
  60#define div_u64_rem     div_u64_rem
  61
  62static inline u64 mul_u32_u32(u32 a, u32 b)
  63{
  64        u32 high, low;
  65
  66        asm ("mull %[b]" : "=a" (low), "=d" (high)
  67                         : [a] "a" (a), [b] "rm" (b) );
  68
  69        return low | ((u64)high) << 32;
  70}
  71#define mul_u32_u32 mul_u32_u32
  72
  73#else
  74# include <asm-generic/div64.h>
  75#endif /* CONFIG_X86_32 */
  76
  77#endif /* _ASM_X86_DIV64_H */
  78