From: Gaurav Sharma <gauravs.2010@gmail.com>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: QEMU-DEVEL <qemu-devel@nongnu.org>
Subject: Re: [Qemu-devel] [ARM - FCVT inst] : Difference in calculated value
Date: Tue, 19 Aug 2014 02:34:45 +0530 [thread overview]
Message-ID: <CABiB5K41Da9D-HF3qBHOp4eO2Xs-OGUKBehqFcRNFz_E7f257Q@mail.gmail.com> (raw)
In-Reply-To: <CAFEAcA-+MvT89MoHd5tfTyeMRgy5HWEnJT6jU=E1dR_jL1SNYQ@mail.gmail.com>
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Hi Peter,
I cross checked it with a AFM model, and the results are indeed different.
The problem I think lies in how we treat de-normalized numbers which are
too small to represent in half precision.
In case of qemu
>> if(exp < -10)
>> return signed/unsigned zero.
However, in case rounding is set, we ignore and we return zero. This may
not be true and we may have a smallest possible denormalized number.
Thanks,
Gaurav
On Sun, Aug 17, 2014 at 1:14 AM, Peter Maydell <peter.maydell@linaro.org>
wrote:
> On 16 August 2014 20:06, Gaurav Sharma <gauravs.2010@gmail.com> wrote:
> > Can some one confirm is this is an issue with qemu implementation ?
>
> It's on my todo list to look at. If you want to confirm it as a QEMU
> bug your best bet is to write a short test program and compare
> the output on QEMU against running it on real hardware.
>
> -- PMM
>
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next prev parent reply other threads:[~2014-08-18 21:05 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-14 7:37 [Qemu-devel] [ARM - FCVT inst] : Difference in calculated value Gaurav Sharma
2014-08-16 19:06 ` Gaurav Sharma
2014-08-16 19:44 ` Peter Maydell
2014-08-18 21:04 ` Gaurav Sharma [this message]
2014-08-18 21:12 ` Peter Maydell
2014-08-19 12:39 ` Gaurav Sharma
2014-08-22 14:28 ` Peter Maydell
2014-08-22 16:27 ` Gaurav Sharma
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