linux-kernel - [PATCH v4 2/2] linux/bits.h: simplify GENMASK_INPUT

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Message-ID: <20241113172939.747686-6-mailhol.vincent@wanadoo.fr>
Date: Thu, 14 Nov 2024 02:18:33 +0900
From: Vincent Mailhol <mailhol.vincent@...adoo.fr>
To: Linus Torvalds <torvalds@...ux-foundation.org>,
	Yury Norov <yury.norov@...il.com>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Luc Van Oostenryck <luc.vanoostenryck@...il.com>
Cc: linux-kernel@...r.kernel.org,
	linux-sparse@...r.kernel.org,
	Rikard Falkeborn <rikard.falkeborn@...il.com>,
	Vincent Mailhol <mailhol.vincent@...adoo.fr>
Subject: [PATCH v4 2/2] linux/bits.h: simplify GENMASK_INPUT_CHECK()

In GENMASK_INPUT_CHECK(),

  __builtin_choose_expr(__is_constexpr((l) > (h)), (l) > (h), 0)

is the exact expansion of:

  const_true((l) > (h))

Apply const_true() to simplify GENMASK_INPUT_CHECK().

Signed-off-by: Vincent Mailhol <mailhol.vincent@...adoo.fr>
---
This change passes the unit tests from CONFIG_BITS_TEST, including the
extra negative tests provided under #ifdef TEST_GENMASK_FAILURES [1].

[1] commit 6d511020e13d ("lib/test_bits.c: add tests of GENMASK")
Link: https://git.kernel.org/torvalds/c/6d511020e13d
---
 include/linux/bits.h | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/include/linux/bits.h b/include/linux/bits.h
index 60044b608817..61a75d3f294b 100644
--- a/include/linux/bits.h
+++ b/include/linux/bits.h
@@ -20,9 +20,8 @@
  */
 #if !defined(__ASSEMBLY__)
 #include <linux/build_bug.h>
-#define GENMASK_INPUT_CHECK(h, l) \
-	(BUILD_BUG_ON_ZERO(__builtin_choose_expr( \
-		__is_constexpr((l) > (h)), (l) > (h), 0)))
+#include <linux/compiler.h>
+#define GENMASK_INPUT_CHECK(h, l) BUILD_BUG_ON_ZERO(const_true((l) > (h)))
 #else
 /*
  * BUILD_BUG_ON_ZERO is not available in h files included from asm files,
-- 
2.45.2