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Date: Mon, 10 Feb 2014 12:15:05 -0800
From: Richard Henderson <rth@twiddle.net>
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Subject: Re: [Qemu-devel] [PATCH 7/8] softfloat: Support halving the result
	of muladd operation
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To: Peter Maydell <peter.maydell@linaro.org>, qemu-devel@nongnu.org
Cc: Peter Crosthwaite <peter.crosthwaite@xilinx.com>, patches@linaro.org, Michael Matz <matz@suse.de>, Alexander Graf <agraf@suse.de>, Claudio Fontana <claudio.fontana@linaro.org>, Dirk Mueller <dmueller@suse.de>, Will Newton <will.newton@linaro.org>, Laurent Desnogues <laurent.desnogues@gmail.com>, =?ISO-8859-1?Q?Alex_Benn=E9e?= <alex.bennee@linaro.org>, kvmarm@lists.cs.columbia.edu, Christoffer Dall <christoffer.dall@linaro.org>

On 02/07/2014 01:49 PM, Peter Maydell wrote:
>          /* Zero plus something non-zero : just return the something */
> +        if (flags & float_muladd_halve_result) {
> +            if (cExp == 0) {
> +                shift32RightJamming(cSig, 1, &cSig);
> +            } else if (cExp == 1) {
> +                shift32RightJamming(cSig, 1, &cSig);
> +                cSig |= (1 << 22);
> +                cExp = 0;
> +            } else {
> +                cExp--;
> +            }

Surely better to just use roundAndPackFloat for this case.  Looks to me that
you're missing inexact and underflow exceptions at least.

> +        }
>          return packFloat32(cSign ^ signflip, cExp, cSig);
>      }


r~