From: Arnd Bergmann <arnd@arndb•de>
To: Segher Boessenkool <segher@kernel•crashing.org>
Cc: linuxppc-dev@ozlabs•org, cbe-oss-dev@ozlabs•org
Subject: Re: [Cbe-oss-dev] [RFC, PATCH] selection of CPU optimization
Date: Fri, 13 Apr 2007 02:10:47 +0200 [thread overview]
Message-ID: <200704130210.48508.arnd@arndb.de> (raw)
In-Reply-To: <e5b10849669a764f002d1926838edc76@kernel.crashing.org>
On Thursday 12 April 2007, Segher Boessenkool wrote:
> > What would be the right options to pass on e200 and on
> > pa6t?
>=20
> The best thing would be to add GCC -mcpu=3D options. =A0For
> now, you're probably best of with -mcpu=3Dpowerpc and
> -mcpu=3Dpowerpc64 resp., i.e. the "blended models". =A0This
> is a good option for multiplatform kernels too; add -mtune=3D
> to optimise for a specific core, but it will *work* on
> the whole family.
We already have makefile magic to test if gcc supports a flag
and fall back to some other one if not.
After looking at rs6000.c, I found that we can probably
reduce the number of different -mcpu=3D options to 16 and only
have separate -mtune=3D options for each specific cpu.
My understanding at this point is that we can always fall back
to -mcpu=3Dpowerpc or -mcpu=3Dpowerpc64, and also
(401, 505, power, power2, rsc) -> not supported
403 -> -mcpu=3D403
(405, 440) -> -mcpu=3D405
(e500, 85xx) -> -mcpu=3D8540
601 -> -mcpu=3D601
(6xx, g3, g4, e300, e600) -> -mcpu=3D603
(ec603e, e200, 82xx) -> -mcpu=3Dec603e
(8xx) -> -mcpu=3D860
(power3, rs64) -> -mcpu=3Dpower3
power4 -> -mcpu=3Dpower4 >> -mcpu=3Dpower3
970 -> -mcpu=3D970 >> -mcpu=3Dpower4
cell -> -mcpu=3Dcell >> -mcpu=3D970
power5 -> -mcpu=3Dpower5 >> -mcpu=3Dpower4
power5+ -> -mcpu=3Dpower5+ >> -mcpu=3Dpower5
power6 -> -mcpu=3Dpower6 >> -mcpu=3Dpower5+
power6x -> -mcpu=3Dpower6x >> -mcpu=3Dpower6
pa6t -> -mcpu=3Dpa6t >> (???)
So if we select e.g. power6 and cell, it needs to fall back to power4,
which is the common subset. Selecting both 403 and 405 would result
in falling back to -mcpu=3Dpowerpc, because they don't have any larger
subset.
I'm not sure what the right fallback fo pa6t should be. I would guess
that it's a superset of power6x and 970 when considering the kernel,
but it's not entirely clear what the fallback should be.
Arnd <><
next prev parent reply other threads:[~2007-04-13 0:10 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-04-10 11:15 [patch 3/3] cell: prevent alignment interrupt on local store Akinobu Mita
2007-04-10 12:52 ` Segher Boessenkool
2007-04-11 3:06 ` Akinobu Mita
2007-04-10 21:22 ` Benjamin Herrenschmidt
2007-04-11 2:56 ` Akinobu Mita
2007-04-11 3:30 ` Benjamin Herrenschmidt
2007-04-11 21:03 ` Segher Boessenkool
2007-04-12 4:23 ` Olaf Hering
2007-04-12 5:26 ` Benjamin Herrenschmidt
2007-04-12 6:33 ` Olaf Hering
2007-04-12 6:38 ` Benjamin Herrenschmidt
2007-04-12 8:31 ` Gabriel Paubert
2007-04-12 8:48 ` Benjamin Herrenschmidt
2007-04-12 6:50 ` Segher Boessenkool
2007-04-12 6:57 ` [Cbe-oss-dev] " Michael Ellerman
2007-04-12 7:07 ` Segher Boessenkool
2007-04-12 18:43 ` Arnd Bergmann
2007-04-12 18:55 ` Arnd Bergmann
2007-04-12 19:57 ` Segher Boessenkool
2007-04-12 19:52 ` Segher Boessenkool
2007-04-12 13:01 ` [RFC, PATCH] selection of CPU optimization Arnd Bergmann
2007-04-12 16:45 ` Kumar Gala
2007-04-12 17:26 ` [Cbe-oss-dev] " Arnd Bergmann
2007-04-12 18:17 ` Kumar Gala
2007-04-12 19:25 ` Arnd Bergmann
2007-04-12 20:04 ` Olof Johansson
2007-04-12 20:01 ` Segher Boessenkool
2007-04-12 20:22 ` Olof Johansson
2007-04-12 20:22 ` Segher Boessenkool
2007-04-12 19:50 ` Segher Boessenkool
2007-04-13 0:10 ` Arnd Bergmann [this message]
2007-04-13 2:03 ` Olof Johansson
2007-04-13 18:43 ` Segher Boessenkool
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=200704130210.48508.arnd@arndb.de \
--to=arnd@arndb$(echo .)de \
--cc=cbe-oss-dev@ozlabs$(echo .)org \
--cc=linuxppc-dev@ozlabs$(echo .)org \
--cc=segher@kernel$(echo .)crashing.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox