linux-stable/include/linux/math64.h
Peter Zijlstra be5e610c0f math64: Add mul_u64_u32_shr()
Introduce mul_u64_u32_shr() as proposed by Andy a while back; it
allows using 64x64->128 muls on 64bit archs and recent GCC
which defines __SIZEOF_INT128__ and __int128.

(This new method will be used by the scheduler.)

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: fweisbec@gmail.com
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/n/tip-hxjoeuzmrcaumR0uZwjpe2pv@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2013-12-11 15:52:34 +01:00

166 lines
3.4 KiB
C

#ifndef _LINUX_MATH64_H
#define _LINUX_MATH64_H
#include <linux/types.h>
#include <asm/div64.h>
#if BITS_PER_LONG == 64
#define div64_long(x, y) div64_s64((x), (y))
#define div64_ul(x, y) div64_u64((x), (y))
/**
* div_u64_rem - unsigned 64bit divide with 32bit divisor with remainder
*
* This is commonly provided by 32bit archs to provide an optimized 64bit
* divide.
*/
static inline u64 div_u64_rem(u64 dividend, u32 divisor, u32 *remainder)
{
*remainder = dividend % divisor;
return dividend / divisor;
}
/**
* div_s64_rem - signed 64bit divide with 32bit divisor with remainder
*/
static inline s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder)
{
*remainder = dividend % divisor;
return dividend / divisor;
}
/**
* div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder
*/
static inline u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder)
{
*remainder = dividend % divisor;
return dividend / divisor;
}
/**
* div64_u64 - unsigned 64bit divide with 64bit divisor
*/
static inline u64 div64_u64(u64 dividend, u64 divisor)
{
return dividend / divisor;
}
/**
* div64_s64 - signed 64bit divide with 64bit divisor
*/
static inline s64 div64_s64(s64 dividend, s64 divisor)
{
return dividend / divisor;
}
#elif BITS_PER_LONG == 32
#define div64_long(x, y) div_s64((x), (y))
#define div64_ul(x, y) div_u64((x), (y))
#ifndef div_u64_rem
static inline u64 div_u64_rem(u64 dividend, u32 divisor, u32 *remainder)
{
*remainder = do_div(dividend, divisor);
return dividend;
}
#endif
#ifndef div_s64_rem
extern s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder);
#endif
#ifndef div64_u64_rem
extern u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder);
#endif
#ifndef div64_u64
extern u64 div64_u64(u64 dividend, u64 divisor);
#endif
#ifndef div64_s64
extern s64 div64_s64(s64 dividend, s64 divisor);
#endif
#endif /* BITS_PER_LONG */
/**
* div_u64 - unsigned 64bit divide with 32bit divisor
*
* This is the most common 64bit divide and should be used if possible,
* as many 32bit archs can optimize this variant better than a full 64bit
* divide.
*/
#ifndef div_u64
static inline u64 div_u64(u64 dividend, u32 divisor)
{
u32 remainder;
return div_u64_rem(dividend, divisor, &remainder);
}
#endif
/**
* div_s64 - signed 64bit divide with 32bit divisor
*/
#ifndef div_s64
static inline s64 div_s64(s64 dividend, s32 divisor)
{
s32 remainder;
return div_s64_rem(dividend, divisor, &remainder);
}
#endif
u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder);
static __always_inline u32
__iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
{
u32 ret = 0;
while (dividend >= divisor) {
/* The following asm() prevents the compiler from
optimising this loop into a modulo operation. */
asm("" : "+rm"(dividend));
dividend -= divisor;
ret++;
}
*remainder = dividend;
return ret;
}
#if defined(CONFIG_ARCH_SUPPORTS_INT128) && defined(__SIZEOF_INT128__)
#ifndef mul_u64_u32_shr
static inline u64 mul_u64_u32_shr(u64 a, u32 mul, unsigned int shift)
{
return (u64)(((unsigned __int128)a * mul) >> shift);
}
#endif /* mul_u64_u32_shr */
#else
#ifndef mul_u64_u32_shr
static inline u64 mul_u64_u32_shr(u64 a, u32 mul, unsigned int shift)
{
u32 ah, al;
u64 ret;
al = a;
ah = a >> 32;
ret = ((u64)al * mul) >> shift;
if (ah)
ret += ((u64)ah * mul) << (32 - shift);
return ret;
}
#endif /* mul_u64_u32_shr */
#endif
#endif /* _LINUX_MATH64_H */