Re: [1/4] powerpc: Discard ffs()/__ffs() function and use builtin functions instead

[Michael Ellerman]

On Fri, 2017-04-21 at 11:18:46 UTC, Christophe Leroy wrote:
> With the ffs() function as defined in arch/powerpc/include/asm/bitops.h
> GCC will not optimise the code in case of constant parameter, as shown
> by the small exemple below.
...
> 
> In addition, when reading the generated vmlinux, we can observe
> that with the builtin functions, GCC sometimes efficiently spreads
> the instructions within the generated functions while the inline
> assembly force them to remain grouped together.
> 
> __builtin_ffs() is already used in arch/powerpc/include/asm/page_32.h
> 
> Those builtins have been in GCC since at least 3.4.6 (see
> https://gcc.gnu.org/onlinedocs/gcc-3.4.6/gcc/Other-Builtins.html )
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>

Series applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/f83647d642270f6b9d75736817fb5a

cheers