On Feb 2, 2010, at 17:11, Gaetan Nadon wrote: > On Tue, 2010-02-02 at 14:00 -0800, Jeremy Huddleston wrote: > >> On Feb 2, 2010, at 13:18, Gaetan Nadon wrote: >> >>> I have not seen any compelling reasons to turn off this optimization. >>> Maybe 10 years ago when it was first introduced. I have seen reports of >>> large number of warnings, but from older gcc versions. As it is today, >>> we are losing some optimization that could be beneficial. >>> >>> This option has been there for so long (most likely copied along), I >>> doubt you will will get a clear answer for each of the 240 xorg modules. >>> It would take a few modules to try it out first. >> >> I see it in libX11 has historically used -fno-strict-aliasing: >> http://cgit.freedesktop.org/xorg/lib/libX11/commit/?id=db7c6fdeeaef9475458498e4cf09d6b1329e9aa3 >> >> but adding XORG_CWARNFLAGS to XORG_DEFAULT_OPTIONS has caused this to change >> for other modules. >> >> Looking at historic versions of modules, I see it present in: >> >> libICE >> libSM >> libX11 >> libXau >> libXfont >> libXft >> libXpm >> libXres >> xorg-server >> >> of course most of these seem to have just copied the entire GCC_WARNINGS >> block and probably didn't actually need -fno-strict-aliasing > > Of course. Whatever the reasons were, if anyone remembers, may not apply > anymore. Devising a plan for it's removal will not be an easy task. I > see 3 options: > > 1) take it out of macros, 1 patch
I sent that patch already. > 2) transfer it to all makefiles and then removing it gradually, that's > 2*240 +1 patches I don't think that's wise. If anything, you should just put it in the ones where it was prior to XORG_CWARNFLAGS (the 9 mentioned above). That being said, I also enabled the warning which should mention when it discovers code sensitive to the -fstrict-aliasing optimization, and none of the libs in the list above spewed such a warning. > 3) override in 'n' makefiles until proven safe. Then take it out macros. > That's 2*n +1 patches. We could do that for the 9 modules above. I'm fairly confident that the libs don't need it, but I haven't rebuilt all of the server to be confident it doesn't spew any warnings about strict-aliasing. _______________________________________________ xorg-devel mailing list xorg-devel@lists.x.org http://lists.x.org/mailman/listinfo/xorg-devel