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| author | Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> | 2008-06-12 10:47:56 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2008-06-12 10:47:56 +0200 |
| commit | f595ec964daf7f99668039d7303ddedd09a75142 (patch) | |
| tree | 4ee6679105f0437995ff200f10885598921ae1cd /include | |
| parent | 5e70b7f3c24468bb1635b295945edb48ecd9656a (diff) | |
| download | linux-stable-f595ec964daf7f99668039d7303ddedd09a75142.tar.gz linux-stable-f595ec964daf7f99668039d7303ddedd09a75142.tar.bz2 linux-stable-f595ec964daf7f99668039d7303ddedd09a75142.zip | |
common implementation of iterative div/mod
We have a few instances of the open-coded iterative div/mod loop, used
when we don't expcet the dividend to be much bigger than the divisor.
Unfortunately modern gcc's have the tendency to strength "reduce" this
into a full mod operation, which isn't necessarily any faster, and
even if it were, doesn't exist if gcc implements it in libgcc.
The workaround is to put a dummy asm statement in the loop to prevent
gcc from performing the transformation.
This patch creates a single implementation of this loop, and uses it
to replace the open-coded versions I know about.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Segher Boessenkool <segher@kernel.crashing.org>
Cc: Christian Kujau <lists@nerdbynature.de>
Cc: Robert Hancock <hancockr@shaw.ca>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/math64.h | 2 | ||||
| -rw-r--r-- | include/linux/time.h | 11 |
2 files changed, 4 insertions, 9 deletions
diff --git a/include/linux/math64.h b/include/linux/math64.h index c1a5f81501ff..177785e1e4a3 100644 --- a/include/linux/math64.h +++ b/include/linux/math64.h @@ -81,4 +81,6 @@ static inline s64 div_s64(s64 dividend, s32 divisor) } #endif +u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder); + #endif /* _LINUX_MATH64_H */ diff --git a/include/linux/time.h b/include/linux/time.h index d32ef0ad4c0a..05f9517a8ed1 100644 --- a/include/linux/time.h +++ b/include/linux/time.h @@ -6,6 +6,7 @@ #ifdef __KERNEL__ # include <linux/cache.h> # include <linux/seqlock.h> +# include <linux/math64.h> #endif #ifndef _STRUCT_TIMESPEC @@ -172,15 +173,7 @@ extern struct timeval ns_to_timeval(const s64 nsec); */ static inline void timespec_add_ns(struct timespec *a, u64 ns) { - ns += a->tv_nsec; - while(unlikely(ns >= NSEC_PER_SEC)) { - /* The following asm() prevents the compiler from - * optimising this loop into a modulo operation. */ - asm("" : "+r"(ns)); - - ns -= NSEC_PER_SEC; - a->tv_sec++; - } + a->tv_sec += iter_div_u64_rem(a->tv_nsec + ns, NSEC_PER_SEC, &ns); a->tv_nsec = ns; } #endif /* __KERNEL__ */ |