Re: [PATCH 05/17] powerpc: Add __attribute_const__ to ffs()-family implementations

Segher Boessenkool <[email protected]> Fri, 15 Aug 2025 11:41:59 -0500

Newsgroups	gmane.linux.ports.ppc.embedded,gmane.linux.kernel.cross-arch,gmane.linux.kernel,gmane.linux.ports.alpha,gmane.linux.ports.hexagon,gmane.linux.ports.m68k,gmane.linux.ports.mips,gmane.linux.ports.parisc,gmane.linux.ports.riscv,gmane.linux.ports.sh.devel,gmane.linux.ports.sparc
Message-ID	<aJ9jV80oYG6rPN1o@gate>

On Fri, Aug 15, 2025 at 11:34:56AM -0500, Segher Boessenkool wrote:
> On Thu, Aug 07, 2025 at 03:16:35PM +0530, Madhavan Srinivasan wrote:
> > making them eligible for compiler optimization.
> 
> You can instead use GCC for this.  __builtin_ffs () exists since 2003,

Erm, 1992 actually, but stuff has moved around since then :-)

> and has this attribute built-in, as well as tens of other optimisations
> that the kernel thing misses.
> 
> Of course using existing stuff instead of cobbling together something
> half working prevents you from having a lot of fun ;-)


Segher