Re: [PATCH v2 0/4] s390: Fix and optimize __flogr() inline assembly

Alexander Gordeev
2025-09-18T14:19:30Z

On Tue, Sep 16, 2025 at 03:47:59PM +0200, Heiko Carstens wrote:
> A recent optimization of the s390 specific ffs() and ffs64()
> implementations leads to a new compiler warning. Instead of reverting the
> optimization address this with the rather new assume attribute, which
> generates even better code, if supported by compilers.
>
> Since the assume attribute may be useful for others as well, add the
> __assume macro to compiler attributes, so it is kernel wide available,
> instead of adding an s390 specific optimization.
>
> Heiko Carstens (4):
> s390/bitops: Limit return value range of __flogr()
> compiler_types: Add __assume macro
> s390/bitops: Use __assume() for __flogr() inline assembly return value
> s390/bitops: Cleanup __flogr()
>
> arch/s390/include/asm/bitops.h | 21 ++++++++++++++-------
> include/linux/compiler_types.h | 23 +++++++++++++++++++++++
> init/Kconfig | 10 ++++++++++
> 3 files changed, 47 insertions(+), 7 deletions(-)

Applied, thanks!