Commit-ID: daa67b4b70568a07fef3cffacb2055891bf42ddb Gitweb: http://git.kernel.org/tip/daa67b4b70568a07fef3cffacb2055891bf42ddb Author: Nicholas Mc Guire <[email protected]> AuthorDate: Mon, 18 May 2015 14:19:14 +0200 Committer: Thomas Gleixner <[email protected]> CommitDate: Tue, 19 May 2015 15:14:16 +0200
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 <[email protected]> Cc: Masahiro Yamada <[email protected]> Cc: Sam Ravnborg <[email protected]> Cc: Joe Perches <[email protected]> Cc: John Stultz <[email protected]> Cc: Andrew Hunter <[email protected]> Cc: Paul Turner <[email protected]> Cc: Michal Marek <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Thomas Gleixner <[email protected]> --- include/linux/jiffies.h | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) diff --git a/include/linux/jiffies.h b/include/linux/jiffies.h index 9527ddb..5e75af6 100644 --- a/include/linux/jiffies.h +++ b/include/linux/jiffies.h @@ -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); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
