[Bug fortran/31114] Consistent floating point arithmetic model option
------- Comment #4 from terry at chem dot gu dot se 2007-03-09 21:29 -------
It seems the "x86 is stupid, see bug 323" blinkers have come down.
I'm not asking for anyone to alter any gcc code generation. I specifically
don't want the FP in software mentioned by kargl. The fact that gcc supports
many more architectures than <insert compiler here> is exactly the point.
A number of the architectures supported by gcc have floating point arithmetic
models that differ from the accepted norm amongst all the rest. There are
architecture-specific options that make the floating point model on those
architectures closer to the norm, improving the consistency across
architectures. When shifting architectures, having to go digging for
architecture-specific options to give the same result is silly. What I'm
asking for is a global option that works as a meta switch for these options in
an architecture-independent manner.
To use karlg's F2003 IEEE 754 example: When that intrinsic module becomes
available in gfortran, how it works will by necessity target-dependent. But
would you expect accessing that module to be target dependent? I certainly
wouldn't. The architecture dependence should be, by default, hidden from the
user.
To quote Eljay: <http://gcc.gnu.org/ml/gcc-help/2007-03/msg00137.html>
> I imagine such a flag would have these guarantees:
> + behind the scenes, specifies the processor-specific option to insure floating-point portability
> + may impose severe performance penalties (one-to-two orders of magnitude) on some platforms
> + may cause the compile to fail if the floating-point constraint cannot be fulfilled (which is probably a good thing)
Yes, yes and yes.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31114
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