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Date: Wed, 6 Aug 2014 08:53:51 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v3 for-2.2 0/8] don't use Yoda conditions
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To: Eric Blake <eblake@redhat.com>
Cc: peter.maydell@linaro.org, peter.crosthwaite@xilinx.com, weidong.huang@huawei.com, stefanha@redhat.com, marcel.a@redhat.com, qemu-trivial@nongnu.org, luonengjun@huawei.com, qemu-devel@nongnu.org, armbru@redhat.com, arei.gonglei@huawei.com, av1474@comtv.ru, kraxel@redhat.com, aliguori@amazon.com, imammedo@redhat.com, dmitry@daynix.com, pbonzini@redhat.com, peter.huangpeng@huawei.com, lcapitulino@redhat.com, afaerber@suse.de, dgilbert@redhat.com

On Tue, Aug 05, 2014 at 07:53:51PM -0600, Eric Blake wrote:
> On 08/05/2014 08:02 AM, Michael S. Tsirkin wrote:
> > On Fri, Aug 01, 2014 at 03:46:08PM +0800, arei.gonglei@huawei.com wrote:
> >> From: Gonglei <arei.gonglei@huawei.com>
> >>
> >> $WHATEVER: don't use 'Yoda conditions'
> >>
> >> 'Yoda conditions' are not part of idiomatic QEMU coding
> >> style, so rewrite them in the more usual order.
> > 
> > 
> > OK but why stop at these files? How about this
> > instead?
> > 
> 
> > @ disable commeq @
> > expression E;
> > constant C;
> > @@
> > - C == E
> > + E == C
> > @ disable commeq @
> > expression E;
> > constant C;
> > @@
> > - C == E
> > + E == C
> 
> Why is this listed twice?
> 
> > @ disable gtr_lss @
> > expression E;
> > constant C;
> > @@
> > - C > E
> > + E < C
> 
> This is wrong for floating point (think NaN); you'd have to audit the
> results to make sure only integers are commuted.

I did, take a look at the results :)

> > @ disable gtr_lss_eq @
> > expression E;
> > constant C;
> > @@
> > - C >= E
> > + E <= C
> 
> Ditto.
> 
> > 
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> 
> The idea seems okay to me, but I haven't closely reviewed the patch yet.
> 
> -- 
> Eric Blake   eblake redhat com    +1-919-301-3266
> Libvirt virtualization library http://libvirt.org
>