linux-kernel - [PATCH 04/10] linux/bits.h: simplify GENMASK_INPUT_CHECK() by using is_const

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Message-Id: <20241203-is_constexpr-refactor-v1-4-4e4cbaecc216@wanadoo.fr>
Date: Tue, 03 Dec 2024 02:33:26 +0900
From: Vincent Mailhol via B4 Relay <devnull+mailhol.vincent.wanadoo.fr@...nel.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>, 
 David Laight <David.Laight@...lab.com>, 
 Luc Van Oostenryck <luc.vanoostenryck@...il.com>, 
 Nathan Chancellor <nathan@...nel.org>, 
 Nick Desaulniers <ndesaulniers@...gle.com>, 
 Bill Wendling <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>, 
 Yury Norov <yury.norov@...il.com>, 
 Rasmus Villemoes <linux@...musvillemoes.dk>, Kees Cook <kees@...nel.org>, 
 "Gustavo A. R. Silva" <gustavoars@...nel.org>, 
 Jani Nikula <jani.nikula@...ux.intel.com>, 
 Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>, 
 Rodrigo Vivi <rodrigo.vivi@...el.com>, 
 Tvrtko Ursulin <tursulin@...ulin.net>, David Airlie <airlied@...il.com>, 
 Simona Vetter <simona@...ll.ch>, Suzuki K Poulose <suzuki.poulose@....com>, 
 Mike Leach <mike.leach@...aro.org>, James Clark <james.clark@...aro.org>, 
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>, 
 Rikard Falkeborn <rikard.falkeborn@...il.com>, 
 Martin Uecker <Martin.Uecker@....uni-goettingen.de>
Cc: linux-sparse@...r.kernel.org, linux-kernel@...r.kernel.org, 
 llvm@...ts.linux.dev, linux-hardening@...r.kernel.org, 
 intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org, 
 coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org, 
 Vincent Mailhol <mailhol.vincent@...adoo.fr>
Subject: [PATCH 04/10] linux/bits.h: simplify GENMASK_INPUT_CHECK() by
 using is_const_true()

From: Vincent Mailhol <mailhol.vincent@...adoo.fr>

In GENMASK_INPUT_CHECK(),

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

is equivalent to:

  is_const_true((l) > (h))

Apply is_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 60044b6088172b3f26aa3f17cdaede9786863dae..ef0119e6179e1ca95345a3d4d3327ba19633028e 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(is_const_true((l) > (h)))
 #else
 /*
  * BUILD_BUG_ON_ZERO is not available in h files included from asm files,

-- 
2.45.2