From: Scott Wood <scottwood@freescale.com>
To: David Laight <David.Laight@ACULAB.COM>
Cc: 'Christophe Leroy' <christophe.leroy@c-s.fr>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
"Michael Ellerman" <mpe@ellerman.id.au>,
"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 2/2] powerpc: add support for csum_add()
Date: Tue, 26 May 2015 14:42:35 -0500 [thread overview]
Message-ID: <1432669355.7862.16.camel@freescale.com> (raw)
In-Reply-To: <063D6719AE5E284EB5DD2968C1650D6D1CB3EB5F@AcuExch.aculab.com>
On Tue, 2015-05-26 at 13:57 +0000, David Laight wrote:
> From: Scott Wood ...
> > > I'd also have thought that the 64bit C version above would be
> > > generally 'good'.
> >
> > It doesn't generate the addc/addze sequence. At least with GCC
> > 4.8.2,
> > it does something like:
> >
> > mr tmp0, csum
> > li tmp1, 0
> > li tmp2, 0
> > addc tmp3, addend, tmp0
> > adde csum, tmp2, tmp1
> > add csum, csum, tmp3
>
> I was thinking of all 64bit targets, not 32bit ones.
Oh, you mean move it out of arch/powerpc? Sounds reasonable, but
someone should probably check what the resulting code looks like on
other common arches. OTOH, if we're going to modify non-arch code,
that might be a good opportunity to implement Segher's suggestion and
move to a 64-bit accumulator.
-Scott
next prev parent reply other threads:[~2015-05-26 19:42 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-19 15:18 [PATCH v3 0/2] Optimise some IP checksum functions Christophe Leroy
2015-05-19 15:18 ` [PATCH v3 1/2] powerpc: put csum_tcpudp_magic inline Christophe Leroy
2015-05-19 15:18 ` [PATCH v3 2/2] powerpc: add support for csum_add() Christophe Leroy
2015-05-22 15:57 ` David Laight
2015-05-22 19:32 ` Scott Wood
2015-05-22 21:39 ` Segher Boessenkool
2015-05-22 21:54 ` Scott Wood
2015-05-26 13:57 ` David Laight
2015-05-26 19:42 ` Scott Wood [this message]
2015-05-27 8:41 ` David Laight
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