In GENMASK_INPUT_CHECK(),
__builtin_choose_expr(__is_constexpr((l) > (h)), (l) > (h), 0)
is the exact expansion of:
_statically_true((l) > (h))
Apply _statically_true() to simplify GENMASK_INPUT_CHECK().
Signed-off-by: Vincent Mailhol <mailhol.vincent@xxxxxxxxxx>
---
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
** Changelog **
v2 -> v3:
- split the single patch into a series of two patches.
- add greater explanation of why _statically_true() is needed in
addition of the existing statically_true(). Explain the pros and
cons of both.
- use __builtin_choose_expr() in _statically_true(). The
_statically_true() of the v2 works perfectly fine when used in
conjunction with BUILD_BUG_ON_ZERO() but fails if used in arrays
or in static_assert()
- update the patch description accordingly
Link: https://lore.kernel.org/all/20241111164743.339117-2-mailhol.vincent@xxxxxxxxxx/
v1 -> v2:
- introduce _statically_true(), taking inspiration from
statically_true() as introduced in commit 22f546873149 ("minmax:
improve macro expansion and type checking").
Link: https://lore.kernel.org/all/20240609073513.256179-1-mailhol.vincent@xxxxxxxxxx/
---
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..01713e1eda56 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(_statically_true((l) > (h)))
#else
/*
* BUILD_BUG_ON_ZERO is not available in h files included from asm files,
--
2.45.2
