Am 21.07.2011 10:57, schrieb Pandu Poluan: > -original message- > Subject: Re: [gentoo-user] New computer and Gentoo > From: Bill Kenworthy <bi...@iinet.net.au> > Date: 2011-07-21 12:54 > >> On Thu, 2011-07-21 at 06:26 +0100, Mick wrote: [...] >> Ive just stumbled on something weird with march=native: >> >> At some point I had march=prescott on a core2 E4600 running 32bit - >> worked well. Changed to march=native and did some upgrades with a few >> odd things like asterisk segfaulting in a glibc library afterwards, and >> some things not building. Then to add confusion, I changed to an >> pentium Duo E6600 (flies!) and added another stick of ram. More odd >> things happening such as reiserfs oopsing on shutdown. >> >> Last night the penny dropped and I looked the new processor up and >> changed to march=core2 and have mostly corrected (recompiled) the >> damage. >> >> So not sure about march=native now as it is only what was built with >> native thats been problematic. With 20-20 hindsight it was perhaps >> predictable ... > > IMO you're not supposed to compile part of the system with -march=<something> > and the rest with -march=native. The instructions (and optimizations) > emitted by -march=native might not be compatible with your previous > -march.
I'd like to see a reference for this claim. -march=native doesn't do more than set -march=core2 and some other optimizations for cache size etc. This should be no more troublesome than mixing code compiled with different specific -march settings. When you look at binary distributions (and especially precompiled packages from the developer instead of the distribution), this is pretty much normal. The compiler is not allowed to change the external interfaces of functions for optimization purposes (see [1]). Besides this, I can only think of alignment problems ([2]) but even this should be handled correctly by the compiler. Everything else is a compiler bug that should be reported. [1] http://en.wikipedia.org/wiki/Calling_convention [2] http://en.wikipedia.org/wiki/Data_alignment Regards, Florian Philipp
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