Gentoo Archives: gentoo-user

From: Hans-Werner Hilse <hilse@×××.de>
To: gentoo-user@l.g.o
Subject: Re: gcc optimization levels (was: Re: [gentoo-user] mplayer compilation)
Date: Tue, 21 Nov 2006 09:58:59
Message-Id: 20061121105406.7d5461db.hilse@web.de
In Reply to: gcc optimization levels (was: Re: [gentoo-user] mplayer compilation) by "Boyd Stephen Smith Jr."
1 Hi,
2
3 On Mon, 20 Nov 2006 23:42:06 -0600 "Boyd Stephen Smith Jr."
4 <bss03@××××××××××.net> wrote:
5
6 > On Monday 20 November 2006 15:13, Daniel Iliev <danny@××××××××.com>
7 > wrote about 'Re: [gentoo-user] mplayer compilation':
8 > > I don't think there is such an option for gcc "-O4". AFAIK the
9 > > shorthand optimization options are -O, -O0, -O1, -O2, -O3 and -Os"
10 >
11 > In addition to -Os, -O will accept any non-negative integer as an
12 > argument. Currently, anything above 3 does nothing extra. From what
13 > I understand, there have been undocumented levels up to 6, but they
14 > have always been considered unstable (which is why they never
15 > appeared in documentation).
16
17 Hm, I don't know if they we're considerend unstable, but I think they
18 were too much of a moving target to actually document them. The -O
19 parameters are passed to gcc's code modules.
20
21 > The quickest way to recognize a Gentoo ricer is someone that
22 > has -O4, -O6, -O99 or something else equally stupid in their CFLAGS.
23 > -O3 is defensible, as it is at least *supposed to be* stable;
24 > anything higher is just stupid.
25
26 OK, I agree that this might be an indication that the person just
27 c&p'ed a part of a wannabee-howto from the forums...
28
29 In this case, however, it's the default setting (at least on my
30 machine) that mplayer choses when it does its own recognizing of the
31 best settings (and ignores Gentoo's CFLAGS). And I've yet to see it
32 break... Myself, I would never care about spending my CPU power beyond
33 anything than -O2, where -O1 is mostly absolutely sufficient. I've seen
34 broken compile runs for -Os and -O3, but -O2 is the safe thing.
35
36 -hwh
37 --
38 gentoo-user@g.o mailing list