From: Aurelien Jarno <aurelien@aurel32.net>
To: Stefan Weil <sw@weilnetz.de>
Cc: Richard Henderson <rth@twiddle.net>,
qemu-stable@nongnu.org, qemu-devel <qemu-devel@nongnu.org>
Subject: Re: [Qemu-devel] [PATCH] tci: Add implementation of rotl_i64, rotr_i64
Date: Mon, 9 Sep 2013 18:47:51 +0200 [thread overview]
Message-ID: <20130909164750.GA32430@ohm.aurel32.net> (raw)
In-Reply-To: <522DF3EA.6060606@weilnetz.de>
On Mon, Sep 09, 2013 at 06:14:34PM +0200, Stefan Weil wrote:
> Am 09.09.2013 16:53, schrieb Aurelien Jarno:
> > On Wed, Sep 04, 2013 at 10:51:54PM +0200, Stefan Weil wrote:
> >> Am 04.09.2013 22:49, schrieb Stefan Weil:
> >>> It is used by qemu-ppc64 when running Debian's busybox-static.
> >>>
> >>> Signed-off-by: Stefan Weil <sw@weilnetz.de>
> >>> ---
> >>>
> >>> This patch is also useful for QEMU 1.6.
> >> ... so I should have added qemu-stable. Done now.
> >>
> > Why is it needed for qemu-stable? It should only improve performance, as
> > these two ops are not mandatory ops. In general I don't think we should
> > have performance improvements in a stable minor release (unless of course
> > it's a big regression from previous).
>
> Hi Aurelien,
>
> tci has always set TCG_TARGET_HAS_rot_i64, and target-ppc64 uses the
> rotl_i64 and rotr_i64 TCG opcodes.
>
> The old implementation just triggered a TODO assertion. That's how I
> implemented TCI: I started with TODO assertions for all opcodes and
> replaced them by real code as soon as I got a test case which used them.
> Now I have a test case :-)
Ok, so it might be a good idea to review the remaining non-implemented
optional ops and to disable them to avoid that in the future.
> => It's not a performance issue, but fixes a fatal assertion.
> => It should be used in 1.6.
>
It should probably also be used in older versions, as rotl and rotr have
been used by various targets for a few years (at least since version
0.10.0, probably even before).
--
Aurelien Jarno GPG: 1024D/F1BCDB73
aurelien@aurel32.net http://www.aurel32.net
next prev parent reply other threads:[~2013-09-09 16:48 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-04 20:49 [Qemu-devel] [PATCH] tci: Add implementation of rotl_i64, rotr_i64 Stefan Weil
2013-09-04 20:51 ` Stefan Weil
2013-09-09 14:53 ` Aurelien Jarno
2013-09-09 16:14 ` Stefan Weil
2013-09-09 16:47 ` Aurelien Jarno [this message]
2013-09-04 23:00 ` Richard Henderson
-- strict thread matches above, loose matches on Subject: below --
2013-09-05 12:00 Jay Foad
2013-09-05 20:17 ` Stefan Weil
2013-09-05 20:33 ` Richard Henderson
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