linux-kernel - [PATCH 3/4] log2: allow use of is_power_of

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Date:   Thu, 30 Mar 2023 13:42:42 +0300
From:   Jani Nikula <jani.nikula@...el.com>
To:     linux-kernel@...r.kernel.org
Cc:     intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        jani.nikula@...el.com, Andrew Morton <akpm@...ux-foundation.org>,
        Christian König <christian.koenig@....com>,
        David Gow <davidgow@...gle.com>
Subject: [PATCH 3/4] log2: allow use of is_power_of_2() in constant expressions

Even though the static inline functions are __attribute__((const)) you
can't use them in constant expressions. Make is_power_of_2() a constant
expression if possible.

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Christian König <christian.koenig@....com>
Cc: David Gow <davidgow@...gle.com>
Signed-off-by: Jani Nikula <jani.nikula@...el.com>
---
 include/linux/log2.h | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/include/linux/log2.h b/include/linux/log2.h
index 4027d1eecd7f..447a85102de0 100644
--- a/include/linux/log2.h
+++ b/include/linux/log2.h
@@ -56,9 +56,11 @@ bool __is_power_of_2(unsigned long n)
  * Return: true if @n is a power of 2, otherwise false.
  */
 #define is_power_of_2(n)						\
-	__builtin_choose_expr(sizeof(n) > sizeof(unsigned long),	\
-			      __is_power_of_2_ull(n),			\
-			      __is_power_of_2(n))
+	__builtin_choose_expr(__is_constexpr(n),			\
+			      __IS_POWER_OF_2(n),			\
+			      __builtin_choose_expr(sizeof(n) > sizeof(unsigned long), \
+						    __is_power_of_2_ull(n), \
+						    __is_power_of_2(n)))
 
 /**
  * __roundup_pow_of_two() - round up to nearest power of two
-- 
2.39.2