Re: [Mingw-w64-public] FPU exceptions not handled ?

[Kai T. <Kai...@on...>]

David Cournapeau <cou...@gm...> wrote on 23.02.2009 15:00:35:

> On Mon, Feb 23, 2009 at 6:08 PM, Kai Tietz <kti...@go...> 
wrote:
> > 2009/2/22 Erik de Castro Lopo <ml...@me...>:
> >> David Cournapeau wrote:
> >>
> >>> This goes into the invalid branch on linux and windows (32 bits), 
but
> >>> not with mingw-w64. Is this a bug, or is this expected ?
> >>
> >> David,
> >>
> >> This *may* be related to the fact the FP stuff on x86_64 is done in
> >> SSE instructions. Your problem could be related to issue like these:
> >>
> >>    http://www.flamingspork.com/blog/2009/02/18/fun-with-387/
> >>   
http://www.flamingspork.com/blog/2009/02/18/floating-point-is-not-fun/
> >>
> >> Cheers,
> >> Erik
> >> --
> >> -----------------------------------------------------------------
> >> Erik de Castro Lopo
> >> -----------------------------------------------------------------
> >> When aiming for the common denominator, be prepared for the
> >> occasional division by zero.
> >>
> >
> > Yes, this fpu functionality isn't working on SSE instruction. There
> > isn't any exception raised by the system for them. So you have to
> > check by __fpclassify, isfinite, isinf, etc.
> 
> I don't see the link between __fpclassify/isfinite/isinf and FPU
> exception: they are totally different features.
> 
> I tried the code from BSD for fesetexcept and fetestexcept, and it
> works when build with mingw-w64 - I am by no mean knowledgeable about
> assembly, but it looks like the main difference is indeed taking into
> account SSE FPU. It seems quite easy to adapt the mingw-w64 fenv code
> to fix this,
> 
> cheers,
> 
> David

Hi David,

thanks for reporting this. I adjusted our code to support SSE2, too. It is 
at the moment pretty experimental, therefore I would be happy, if you 
could test it a bit. (See trunk rev. 651).

Cheers,
Kai

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