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Date: Wed, 16 Jan 2019 13:21:50 -0500
From: "Emilio G. Cota" <cota@braap.org>
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Subject: Re: [Qemu-devel] [PATCH] include/fpu/softfloat: Fix compilation
 with Clang on s390x
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To: Thomas Huth <thuth@redhat.com>
Cc: Alex =?iso-8859-1?Q?Benn=E9e?= <alex.bennee@linaro.org>, Peter Maydell <peter.maydell@linaro.org>, Cornelia Huck <cohuck@redhat.com>, QEMU Developers <qemu-devel@nongnu.org>, qemu-s390x <qemu-s390x@nongnu.org>, Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= <philmd@redhat.com>, Aurelien Jarno <aurelien@aurel32.net>, Richard Henderson <rth@twiddle.net>

On Wed, Jan 16, 2019 at 07:33:28 +0100, Thomas Huth wrote:
> On 2019-01-15 21:05, Emilio G. Cota wrote:
> > On Tue, Jan 15, 2019 at 16:01:32 +0000, Alex Bennée wrote:
> >> Ahh I should have mentioned we already have the technology for this ;-)
> >>
> >> If you build the fpu/next tree on a s390x you can then run:
> >>
> >>   ./tests/fp/fp-bench f64_div
> >>
> >> with and without the CONFIG_128 path. To get an idea of the real world
> >> impact you can compile a foreign binary and run it on a s390x system
> >> with:
> >>
> >>   $QEMU ./tests/fp/fp-bench f64_div -t host
> >>
> >> And that will give you the peak performance assuming your program is
> >> doing nothing but f64_div operations. If the two QEMU's are basically in
> >> the same ballpark then it doesn't make enough difference. That said:
> > 
> > I think you mean here `tests/fp/fp-bench -o div -p double', otherwise
> > you'll get the default op (-o add).
> 
> I tried that now, too, and -o div -p double does not really seem to
> exercise this function at all.

You can check what is being called then with perf record/report.

		E.