[Bug target/110181] longlong.h for RISCV should define count_leading_zeros and count_trailing_zeros and COUNT_LEADING_ZEROS_0 when ZBB is enabled

[cvs-commit at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110181

--- Comment #4 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jeff Law <l...@gcc.gnu.org>:

https://gcc.gnu.org/g:e08ef05e4da86d34223118092bbb857b8dd5d002

commit r16-1584-ge08ef05e4da86d34223118092bbb857b8dd5d002
Author: Sosutha Sethuramapandian <ssethuram...@marvell.com>
Date:   Thu Jun 19 20:53:56 2025 -0600

    [PATCH] RISC-V: Use builtin clz/ctz when count_leading_zeros and
count_trailing_zeros is used

    longlong.h for RISCV should define count_leading_zeros and
    count_trailing_zeros and COUNT_LEADING_ZEROS_0 when ZBB is enabled.

    The following patch patch fixes the bug reported in,
    https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110181

    The divdi3 on riscv32 with zbb extension generates __clz_tab
    instead of genearating  __builtin_clzll/__builtin_clz which is
    not efficient since lookup table is emitted.

    Updating longlong.h to use this __builtin_clzll/__builtin_clz
    generates optimized code for the instruction.

            PR target/110181

    include/ChangeLog

            * longlong.h  [__riscv] (count_leading_zeros): Define.
            [__riscv] (count_trailing_zeros): Likewise.
            [__riscv] (COUNT_LEADING_ZEROS_0): Likewise.