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time: Allow gcc to fold constants when possible 

To allow constant folding in msecs_to_jiffies() conditionally calls
the HZ dependent _msecs_to_jiffies() helpers or, when gcc can not
figure out constant folding, __msecs_to_jiffies which is the renamed
original msecs_to_jiffies() function.

Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Cc: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Joe Perches <joe@perches.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Andrew Hunter <ahh@google.com>
Cc: Paul Turner <pjt@google.com>
Cc: Michal Marek <mmarek@suse.cz>
Link: http://lkml.kernel.org/r/1431951554-5563-3-git-send-email-hofrat@osadl.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Nicholas Mc Guire 2015-05-18 14:19:14 +02:00 committed by Thomas Gleixner
parent ca42aaf0c8
commit daa67b4b70
1 changed files with 15 additions and 3 deletions
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18
include/linux/jiffies.h
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@ -343,12 +343,24 @@ static inline unsigned long _msecs_to_jiffies(const unsigned int m)
* handling any 32-bit overflows.
* for the details see __msecs_to_jiffies()
*
* the HZ range specific helpers _msecs_to_jiffies() are called from
* __msecs_to_jiffies().
* msecs_to_jiffies() checks for the passed in value being a constant
* via __builtin_constant_p() allowing gcc to eliminate most of the
* code, __msecs_to_jiffies() is called if the value passed does not
* allow constant folding and the actual conversion must be done at
* runtime.
* the HZ range specific helpers _msecs_to_jiffies() are called both
* directly here and from __msecs_to_jiffies() in the case where
* constant folding is not possible.
*/
static inline unsigned long msecs_to_jiffies(const unsigned int m)
{
return __msecs_to_jiffies(m);
if (__builtin_constant_p(m)) {
if ((int)m < 0)
return MAX_JIFFY_OFFSET;
return _msecs_to_jiffies(m);
} else {
return __msecs_to_jiffies(m);
}
}
extern unsigned long usecs_to_jiffies(const unsigned int u);