Gentoo Archives: gentoo-dev

From: Christopher Head <chead@×××××.ca>
To: gentoo-dev@l.g.o
Subject: Re: [gentoo-dev] Moving CPU flags into USE_EXPAND
Date: Tue, 20 Jan 2015 20:26:28
Message-Id: C2F820D3-CA1D-452F-879D-164D9A467B20@chead.ca
In Reply to: Re: [gentoo-dev] Moving CPU flags into USE_EXPAND by Alexis Ballier
1 On January 20, 2015 12:47:03 AM PST, Alexis Ballier <aballier@g.o> wrote:
2 >So, you're telling me that if you have a list of 90 cpu extensions, you
3 >will from time to time open that list to see if there is a 91st one
4 >added ? I think most people won't even notice, at best they'll look for
5 >the changelog.
6
7 No, actually, I’m advocating the exact opposite. I’m saying that, as long as the list file is kept up to date, then I will look at those 90 flags when I first install and never again. If a 91st flag appears some day, then as long as the file was maintained as I described in an earlier message (i.e. flags are added as soon as manufacturers announce features), I already know I can reliably ignore the new flag. After all, if the flag didn’t exist when I installed the system, then my CPU must necessarily not have that feature—unless CPUs are in the habit of sprouting new instructions after you buy them!
8
9 >Isn't it better to have a script, e.g. in gentoo-x86/scripts (that
10 >would be the first of this kind here I think), that would
11 >"parse" /proc/cpuinfo and output 'CPU_FLAGS_...="..."' so that for a
12 >first install you can simply send its output to make.conf and, if you
13 >are paranoid, can use it to check if this has changed in a postsync
14 >hook ?
15
16 I see having a script to select flag values as orthogonal to when the flag values need to be looked at. I also agree that having a script would be a good thing.
17
18 --
19 Christopher Head

Replies

Subject Author
Re: [gentoo-dev] Moving CPU flags into USE_EXPAND Andrew Savchenko <bircoph@g.o>
Re: [gentoo-dev] Moving CPU flags into USE_EXPAND Gordon Pettey <petteyg359@×××××.com>