Gentoo Archives: gentoo-amd64

From: "Hemmann
To: gentoo-amd64@l.g.o
Subject: Re: [gentoo-amd64] Old topic comes round again: -Ox optimizations.
Date: Thu, 03 Nov 2005 11:24:36
Message-Id: 200511031222.04016.volker.armin.hemmann@tu-clausthal.de
In Reply to: [gentoo-amd64] Old topic comes round again: -Ox optimizations. by Duncan <1i5t5.duncan@cox.net>
1 On Thursday 03 November 2005 09:47, Duncan wrote:
2
3
4 >
5 > So... certainly for kernel and probably for glibc stuff (tho I believe
6 > Gentoo kills -Os on glibc compiles unless you hack out that portion of the
7 > ebuild, in your own overlay or whatever), -Os is likely to be the best
8 > choice. For most of userland, -Os may be best, but to a smaller degree,
9 > and performance should be similar with -O2, trading size for medium speed
10 > optimizations in what amounts to a wash. The exceptions would likely be
11 > media encoders and the like, where the working set is large and in a data
12 > streaming environment, and -O3 may make sense. In the general case,
13 > however, -O3 likely does NOT make sense, because it's almost always so
14 > expensive in size that the gains in speed over -O2 are far outweighed.
15 >
16
17 AFAIR and so on.
18
19 Os is 'forbidden' for glibc, because there were some gcc bugs, that
20 miscompiled glibc with Os.
21
22 But with gentoo 1.2/1.4, I went for some time with Os in CFLAGS - and my
23 system was not faster than with O2. But it was a little faster with Os or O2
24 than O3 ;)
25 --
26 gentoo-amd64@g.o mailing list

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[gentoo-amd64] Re: Old topic comes round again: -Ox optimizations. Duncan <1i5t5.duncan@×××.net>