RE: [PATCH 04/10] linux/bits.h: simplify GENMASK_INPUT_CHECK() by using is_const_true()

[David Laight]

From: Vincent Mailhol
> Sent: 02 December 2024 17:33
> 
>   __builtin_choose_expr(__is_constexpr((l) > (h)), (l) > (h), 0)
> 
> is equivalent to:
> 
>   is_const_true((l) > (h))

Change it to BUILD_BUG_ON_MSG(statically_true((l) < (h)), "error message")

and then fix all the fallout :-)

	David

> 
> Apply is_const_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
> ---
>  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
> 

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)