[PATCH v2 1/5] arch: select HAVE_ARCH_BITREVERSE conditionally on BITREVERSE

[Yury Norov]

Ping?

On Wed, May 06, 2026 at 01:52:02PM -0400, Yury Norov wrote:
> Architectures may have bit reversal instructions, but if the API not
> needed, the corresponding option should not be selected because it may
> lead to generating the unneeded code.
> 
> Signed-off-by: Yury Norov <ynorov at nvidia.com>
> ---
>  arch/arm/Kconfig       | 2 +-
>  arch/arm64/Kconfig     | 2 +-
>  arch/loongarch/Kconfig | 2 +-
>  arch/mips/Kconfig      | 2 +-
>  lib/Kconfig            | 1 +
>  5 files changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 71fc5dd4123f..0e963e54fe06 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -83,7 +83,7 @@ config ARM
>  	select HARDIRQS_SW_RESEND
>  	select HAS_IOPORT
>  	select HAVE_ARCH_AUDITSYSCALL if AEABI && !OABI_COMPAT
> -	select HAVE_ARCH_BITREVERSE if (CPU_32v7M || CPU_32v7) && !CPU_32v6
> +	select HAVE_ARCH_BITREVERSE if (CPU_32v7M || CPU_32v7) && !CPU_32v6 && BITREVERSE
>  	select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL && !CPU_ENDIAN_BE32 && MMU && (!PREEMPT_RT || !SMP)
>  	select HAVE_ARCH_KFENCE if MMU && !XIP_KERNEL
>  	select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32 && MMU
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index fe60738e5943..f5bb62c2ba9c 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -150,7 +150,7 @@ config ARM64
>  	select HAVE_ACPI_APEI if (ACPI && EFI)
>  	select HAVE_ALIGNED_STRUCT_PAGE
>  	select HAVE_ARCH_AUDITSYSCALL
> -	select HAVE_ARCH_BITREVERSE
> +	select HAVE_ARCH_BITREVERSE if BITREVERSE
>  	select HAVE_ARCH_COMPILER_H
>  	select HAVE_ARCH_HUGE_VMALLOC
>  	select HAVE_ARCH_HUGE_VMAP
> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> index 3b042dbb2c41..6c3444e31c0e 100644
> --- a/arch/loongarch/Kconfig
> +++ b/arch/loongarch/Kconfig
> @@ -115,7 +115,7 @@ config LOONGARCH
>  	select HAS_IOPORT
>  	select HAVE_ALIGNED_STRUCT_PAGE if 64BIT
>  	select HAVE_ARCH_AUDITSYSCALL
> -	select HAVE_ARCH_BITREVERSE if 64BIT
> +	select HAVE_ARCH_BITREVERSE if 64BIT && BITREVERSE
>  	select HAVE_ARCH_JUMP_LABEL
>  	select HAVE_ARCH_JUMP_LABEL_RELATIVE
>  	select HAVE_ARCH_KASAN if 64BIT
> diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
> index 4364f3dba688..7e1494e0dbfa 100644
> --- a/arch/mips/Kconfig
> +++ b/arch/mips/Kconfig
> @@ -2026,7 +2026,7 @@ config CPU_MIPSR6
>  	default y if CPU_MIPS32_R6 || CPU_MIPS64_R6
>  	select CPU_HAS_RIXI
>  	select CPU_HAS_DIEI if !CPU_DIEI_BROKEN
> -	select HAVE_ARCH_BITREVERSE
> +	select HAVE_ARCH_BITREVERSE if BITREVERSE
>  	select MIPS_ASID_BITS_VARIABLE
>  	select MIPS_SPRAM
>  
> diff --git a/lib/Kconfig b/lib/Kconfig
> index 00a9509636c1..d8e7e89ae320 100644
> --- a/lib/Kconfig
> +++ b/lib/Kconfig
> @@ -58,6 +58,7 @@ config BITREVERSE
>  config HAVE_ARCH_BITREVERSE
>  	bool
>  	default n
> +	depends on BITREVERSE
>  	help
>  	  This option enables the use of hardware bit-reversal instructions on
>  	  architectures which support such operations.
> -- 
> 2.51.0