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Date: Wed, 21 Mar 2018 16:16:51 -0400
From: "Emilio G. Cota" <cota@braap.org>
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	<20180220210137.18018-1-alex.bennee@linaro.org>
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In-Reply-To: <20180220210137.18018-1-alex.bennee@linaro.org>
Subject: Re: [Qemu-devel] [PATCH] fpu/softfloat: use hardware sqrt if we can
 (EXPERIMENT!)
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To: Alex =?iso-8859-1?Q?Benn=E9e?= <alex.bennee@linaro.org>
Cc: peter.maydell@linaro.org, richard.henderson@linaro.org, Peter Crosthwaite <crosthwaite.peter@gmail.com>, Riku Voipio <riku.voipio@iki.fi>, qemu-devel@nongnu.org, Laurent Vivier <laurent@vivier.eu>, "open list:ARM" <qemu-arm@nongnu.org>, Paolo Bonzini <pbonzini@redhat.com>, Aurelien Jarno <aurelien@aurel32.net>, Richard Henderson <rth@twiddle.net>

On Tue, Feb 20, 2018 at 21:01:37 +0000, Alex Bennée wrote:
> This is an attempt to save some of the cost of sqrt by using the
> inbuilt support of the host hardware. The idea is assuming we start
> with a valid input we can use the hardware. If any tininess issues
> occur this will trip and FPU exception where:
> 
>   - we turn off cpu->use_host_fpu
>   - mask the FPU exceptions
>   - return to what we were doing

Please see this thread for an alternative approach:

  [Qemu-devel] [PATCH v1 00/14] fp-test + hostfloat
  https://lists.gnu.org/archive/html/qemu-devel/2018-03/msg05908.html

		Emilio