From: Segher Boessenkool <segher@kernel.crashing.org>
To: Simon Guo <wei.guo.simon@gmail.com>
Cc: linuxppc-dev@lists.ozlabs.org,
"Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>,
Cyril Bur <cyrilbur@gmail.com>
Subject: Re: [PATCH v6 2/4] powerpc/64: enhance memcmp() with VMX instruction for long bytes comparision
Date: Wed, 30 May 2018 03:35:40 -0500 [thread overview]
Message-ID: <20180530083540.GG17342@gate.crashing.org> (raw)
In-Reply-To: <20180530081402.GB5951@simonLocalRHEL7.x64>
On Wed, May 30, 2018 at 04:14:02PM +0800, Simon Guo wrote:
> Hi Segher,
> On Mon, May 28, 2018 at 06:05:59AM -0500, Segher Boessenkool wrote:
> > On Fri, May 25, 2018 at 12:07:34PM +0800, wei.guo.simon@gmail.com wrote:
> > > + /* save and restore cr0 */
> > > + mfocrf r5,64
> > > + EXIT_VMX_OPS
> > > + mtocrf 64,r5
> > > + b .LcmpAB_lightweight
> >
> > That's cr1, not cr0. You can use mcrf instead, it is cheaper (esp. if
> > you have it in a non-volatile CR field before so you need only one, if any).
> >
> You are right :) How about using mtcr/mfcr instead, I think they are
> fast as well and more readable.
Those are much worse than m[ft]ocrf.
You probably should just shuffle things around so that EXIT_VMX_OPS
does not clobber the CR field you need to keep.
Segher
next prev parent reply other threads:[~2018-05-30 8:35 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-25 4:07 [PATCH v6 0/4] powerpc/64: memcmp() optimization wei.guo.simon
2018-05-25 4:07 ` [PATCH v6 1/4] powerpc/64: Align bytes before fall back to .Lshort in powerpc64 memcmp() wei.guo.simon
2018-05-28 10:35 ` Segher Boessenkool
2018-05-30 8:11 ` Simon Guo
2018-05-30 8:27 ` Segher Boessenkool
2018-05-30 9:02 ` Simon Guo
2018-05-25 4:07 ` [PATCH v6 2/4] powerpc/64: enhance memcmp() with VMX instruction for long bytes comparision wei.guo.simon
2018-05-28 11:05 ` Segher Boessenkool
2018-05-30 8:14 ` Simon Guo
2018-05-30 8:35 ` Segher Boessenkool [this message]
2018-05-30 9:03 ` Simon Guo
2018-06-06 6:42 ` Simon Guo
2018-06-06 20:00 ` Segher Boessenkool
2018-05-28 11:59 ` Michael Ellerman
2018-05-30 8:15 ` Simon Guo
2018-05-25 4:07 ` [PATCH v6 3/4] powerpc/64: add 32 bytes prechecking before using VMX optimization on memcmp() wei.guo.simon
2018-05-25 4:07 ` [PATCH v6 4/4] powerpc:selftest update memcmp_64 selftest for VMX implementation wei.guo.simon
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