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Commit daa67b4b authored by Nicholas Mc Guire's avatar Nicholas Mc Guire Committed by Thomas Gleixner
Browse files

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: default avatarNicholas 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: default avatarThomas Gleixner <tglx@linutronix.de>
parent ca42aaf0

include/linux/jiffies.h

+15 −3
Original line number Original line Diff line number Diff line
@@ -343,13 +343,25 @@ static inline unsigned long _msecs_to_jiffies(const unsigned int m) 
 *   handling any 32-bit overflows.

 *   handling any 32-bit overflows.

 *   for the details see __msecs_to_jiffies()

 *   for the details see __msecs_to_jiffies()

 *

 *

 * the HZ range specific helpers _msecs_to_jiffies() are called from

 * msecs_to_jiffies() checks for the passed in value being a constant

 * __msecs_to_jiffies().

 * 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)

static inline unsigned long msecs_to_jiffies(const unsigned int 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);

		return __msecs_to_jiffies(m);

	}

	}

}





extern unsigned long usecs_to_jiffies(const unsigned int u);

extern unsigned long usecs_to_jiffies(const unsigned int u);

extern unsigned long timespec_to_jiffies(const struct timespec *value);

extern unsigned long timespec_to_jiffies(const struct timespec *value);