-----Original Message----- From: Brooks Davis <bro...@freebsd.org> Date: 2018-06-07, Thursday at 09:27 To: Ravi Pokala <rpok...@freebsd.org> Cc: "Jonathan T. Looney" <j...@freebsd.org>, Mateusz Guzik <mjgu...@gmail.com>, Mateusz Guzik <m...@freebsd.org>, src-committers <src-committ...@freebsd.org>, <svn-src-...@freebsd.org>, <svn-src-head@freebsd.org> Subject: Re: svn commit: r334702 - head/sys/sys
> On Thu, Jun 07, 2018 at 12:01:00AM -0400, Ravi Pokala wrote: >>> I believe the theory is that the compiler (remember, this is >>> __builtin_memset) can optimize away portions of the zeroing, or can >>> optimize zeroing for small sizes. >> >> Ahhh! I didn't consider that the compiler would be doing analysis of the >> larger context, and potentially skipping zeroing parts that are set >> immediately after the call. > > Clang does this. It does make for some quite interesting object code, > but the result is that zeroing with __builtin_memset() is basically free > for mostly-initialized structures. > > -- Brooks Yeah, it's a subtle but obvious optimization in hindsight. Thanks for the info. -Ravi (rpokala@) _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
