Re: weird optimization in sin+cos, x86 backend

[Vincent Lefevre <vincent+gcc at vinc17 dot org>]

On 2012-02-03 16:51:22 -0500, Robert Dewar wrote:
> All machines that implement IEEE arithmetic :-) As we know only too well
> from the universe of machines on which we implement GNAT, this is not
> all machines :-)

But I think that machines with no IEEE support will tend to disappear
(and already tends to disappear). IEEE support has even been introduced
in GPU's. And users who need a good arithmetic will run their code on
machines capable of providing one.

Concerning the sincos problem here, this is just a bug in the library,
which doesn't follow Intel's spec. Note that the glibc manual says
that sincos is implemented on the x86_64 with a maximum error of 1 ulp
(Section 19.7 Known Maximum Errors in Math Functions), so that the code
clearly doesn't follow the documentation.

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Vincent Lefèvre <vincent@vinc17.net> - Web: <http://www.vinc17.net/>
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