mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2026-09-22 09:34:56 +02:00
Kuan-Wei Chiu
36e2241687
The binary GCD implementation uses FFS (find first set), which benefits from hardware support for the ctz instruction, provided by the Zbb extension on RISC-V. Without Zbb, this results in slower software-emulated behavior. Previously, RISC-V always used the binary GCD, regardless of actual hardware support. This patch improves runtime efficiency by disabling the efficient_ffs_key static branch when Zbb is either not enabled in the kernel (config) or not supported on the executing CPU. This selects the odd-even GCD implementation, which is faster in the absence of efficient FFS. This change ensures the most suitable GCD algorithm is chosen dynamically based on actual hardware capabilities. Link: https://lkml.kernel.org/r/20250606134758.1308400-4-visitorckw@gmail.com Co-developed-by: Yu-Chun Lin <eleanor15x@gmail.com> Signed-off-by: Yu-Chun Lin <eleanor15x@gmail.com> Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com> Acked-by: Alexandre Ghiti <alexghiti@rivosinc.com> Cc: Albert Ou <aou@eecs.berkeley.edu> Cc: Ching-Chun (Jim) Huang <jserv@ccns.ncku.edu.tw> Cc: Palmer Dabbelt <palmer@dabbelt.com> Cc: Paul Walmsley <paul.walmsley@sifive.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.