[PATCH v2] RISC-V: Use __builtin_ffs when zbb is enabled

[Xi Ruoyao]

On Sun, 2025-01-26 at 18:25 -0800, Khem Raj wrote:
> 
> 
> On Sun, Jan 26, 2025 at 6:19 PM Anton Blanchard <antonb@tenstorrent.com> wrote:
> > Using __builtin_ffs when zbb is enabled takes __ffs from 26
> > instructions to 5.
> > ---
> >  sysdeps/riscv/math-use-builtins-ffs.h | 7 +++++++
> >  1 file changed, 7 insertions(+)
> >  create mode 100644 sysdeps/riscv/math-use-builtins-ffs.h
> > 
> > diff --git a/sysdeps/riscv/math-use-builtins-ffs.h b/sysdeps/riscv/math-use-builtins-ffs.h
> > new file mode 100644
> > index 0000000000..836958565b
> > --- /dev/null
> > +++ b/sysdeps/riscv/math-use-builtins-ffs.h
> > @@ -0,0 +1,7 @@
> > +#if __GNUC_PREREQ (12, 0) && defined __riscv_zbb
> > 
> 
> 
> Do we need to check for gcc version ?
> It would be more portable if we did not have to 

https://godbolt.org/z/cKzG5Tb35


-- 
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University