> From: Michel =?ISO-8859-1?Q?D=E4nzer?= <[email protected]> > Date: Mon, 01 Nov 2010 08:18:51 +0100 > > On Son, 2010-10-31 at 15:54 -0700, Jeremy Huddleston wrote: > > Resurrecting this thread as I just realized it was never actually fixed. > > > > I propose we actually follow up on these changes. We should remove > > -fno-strict-aliasing from XORG_CWARNFLAGS and only add them to the > > modules that actually require it. We can start out consercatively by > > adding it to the modules listed in the email below (as well as the > > xf86-* drivers that historically had the flag which I didn't check at > > the time of the first email... I know intel needs it) > > I still haven't seen any measurements showing any benefits from making > this change. Are there any?
I think Michael is asking a very good question here. The strict aliasing rules introduced in C99 have always been somewhat controversial. They get in the way for lots of low-level programming tasks such as protocol decoding and frame buffer manipulations. And at least in my opinion the rules are simply hard to understand; I need to read up on the issue again every time it pops up. I may be somewhat overcautious, but I would keep -fno-strict-aliasing as a default. And I'd only enable -fstrict-aliasing for particular bits of code where it has a significant performance benefit, and people have done a careful analysis of the code to see if it is free of aliasing issues. _______________________________________________ [email protected]: X.Org development Archives: http://lists.x.org/archives/xorg-devel Info: http://lists.x.org/mailman/listinfo/xorg-devel
