Files
kernel/include/linux
Jakub Jelinek 2f78788b55 ilog2: improve ilog2 for constant arguments
As discussed in https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97445 the
const_ilog2 macro generates a lot of code which interferes badly with GCC
inlining heuristics, until it can be proven that the ilog2 argument can or
can't be simplified into a constant.

It can be expressed using __builtin_clzll builtin which is supported by
GCC 3.4 and later and when used only in the __builtin_constant_p guarded
code it ought to always fold back to a constant.  Other compilers support
the same builtin for many years too.

Other option would be to change the const_ilog2 macro, though as the
description says it is meant to be used also in C constant expressions,
and while GCC will fold it to constant with constant argument even in
those, perhaps it is better to avoid using extensions in that case.

[akpm@linux-foundation.org: coding style fixes]

Link: https://lkml.kernel.org/r/20201120125154.GB3040@hirez.programming.kicks-ass.net
Link: https://lkml.kernel.org/r/20201021132718.GB2176@tucnak
Signed-off-by: Jakub Jelinek <jakub@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-12-15 22:46:16 -08:00
..
2020-12-04 13:28:25 +01:00
2020-11-06 08:08:37 -08:00
2020-10-16 17:21:51 +02:00
2020-12-11 14:02:14 -08:00
2020-11-16 16:31:41 +01:00
2020-11-16 15:20:01 +01:00
2020-11-26 00:04:04 +01:00
2020-12-02 22:10:35 -08:00
2020-11-24 16:47:48 +01:00
2020-11-19 22:38:29 -05:00
2020-10-13 18:38:32 -07:00
2020-12-07 10:29:57 +01:00
2020-12-04 12:23:25 +01:00
2020-12-15 15:11:08 -06:00
2020-10-18 09:27:10 -07:00
2020-12-03 11:20:52 +01:00
2020-12-15 12:13:39 -08:00
2020-11-06 10:05:18 -08:00
2020-12-10 16:17:15 +01:00
2020-12-15 12:13:37 -08:00
2020-11-24 16:47:49 +01:00
2020-12-10 10:45:36 +01:00
2020-11-16 15:20:01 +01:00
2020-12-04 16:54:35 +01:00
2020-11-09 18:39:36 +01:00
2020-12-15 12:13:41 -08:00