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List Archive: gentoo-amd64
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To: gentoo-amd64@g.o
From: Duncan <1i5t5.duncan@...>
Subject: Re: Old topic comes round again: -Ox optimizations.
Date: Thu, 03 Nov 2005 08:27:34 -0700
Hemmann, Volker Armin posted
<200511031222.04016.volker.armin.hemmann@...>, excerpted
below,  on Thu, 03 Nov 2005 12:22:03 +0100:

> Os is 'forbidden' for glibc, because there were some gcc bugs, that 
> miscompiled glibc with Os.

I've actually run an -Os compiled glibc here (hacked the ebuild to
remove the filterflags/replaceflags/stripflags calls) for some time, no
noticed issues (tho I haven't tried it with gcc-4.x yet).

However, it's unsupported, and because glibc is linked by virtually
everything, I couldn't be sure whether problems I might have were due to
it or not.  The thing that switched me back was attempting to trace down
why xorg had quite responding to CTRL-ALT-Fx VT-switch commands.  I later
found out it was a known issue with that version on some configs, fixed in
a later version, but glibc is too big a compile (expecially when it's
compiled twice, once for 32-bit and once for 64-bit, up to four times for
those poor folks running nptl without nptl-only, just the two compiles
here, with a dual Opteron, is long, can't imagine four compiles on a
single CPU...) to be worth fighting with all the time, I decided.

Note that for something as universally used as glibc, I'd definitely
recommend having a backup root partition with an untouched copy, if you
start fooling with removing the strip-flags type stuff.

Anyway, I expect the -Os problems for glibc were on x86, not amd64. 
That's apparently been the case in most cases where flags are simply
removed without regard for arch, assuming everything else is as broken as
32-bit x86, when that's not necessarily the case.  Not saying that
problems won't occur on amd64, only that I actually expected issues from
it and didn't see any.

As I said, however, I'm done with my -Os fiddling for glibc, for the time
being, if only because the hacking to get it and constant wondering if
that's the problem any time something strange happens, isn't worth the
trouble, for me.

If folks wish to try it, however, and have a well tested backup boot
method in case glibc fails /entirely/, making the existing install
entirely unbootable, understand the risks, and have the time to do the
compiles, I'd say if you're the type that won't be satisfied until you at
least try it and get it out of your blood, so to speak, you might as well
do so.  It's not as fatal as the dire warnings seem to make it out to be.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman in
http://www.linuxdevcenter.com/pub/a/linux/2004/12/22/rms_interview.html


-- 
gentoo-amd64@g.o mailing list


Replies:
Re: Re: Old topic comes round again: -Ox optimizations.
-- Hemmann, Volker Armin
References:
Old topic comes round again: -Ox optimizations.
-- Duncan
Re: Old topic comes round again: -Ox optimizations.
-- Hemmann, Volker Armin
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Updated Jun 17, 2009

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