Date: Thu, 19 Aug 1999 17:27:33 +1000 From: Bruce Evans <bde@zeta.org.au> To: cvs-all@FreeBSD.org, cvs-committers@FreeBSD.org, peter@FreeBSD.org Subject: Re: cvs commit: src/sys/i386/include cpufunc.h Message-ID: <199908190727.RAA14796@godzilla.zeta.org.au>
next in thread | raw e-mail | index | archive | help
> Modified files: > sys/i386/include cpufunc.h > Log: > Try using the builtin ffs() for egcs, it (by random inspection) > generates slightly better code and avoids the incl then subl when > using ffs(foo) - 1. The inline asm version of ffs(x) should be implemented as (x == 0 ? 0 : bsfl(x) + 1). The compiler can then perform all possible optimisations except ones that use the condition codes delivered by bsfl (these never seem to help). This gives slightly better code than the builtin. Bruce To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199908190727.RAA14796>