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Re: GCC floating point usage


>>>>> Mark Mitchell writes:


>> I am reserving final judgment until I see a complete definition of
>> the semantics and an implementation

Mark> If maintainers take the attitude that they will not make a judgement
Mark> about semantics before seeing an implementation, the bar has been set
Mark> too high.

Mark> There is no reason that a contributor should have to actually implement
Mark> something before we decide if we want it.  We should say "yes, that
Mark> is a feature we want" or "no, it is not".  Obviously, we don't want it
Mark> at any cost; if it is a ten-thousand line horribly ugly patch for a
Mark> not-terribly-desirable feature, it's not a winner.  But, we should be
Mark> able to say "yes, that feature is a good one; if the patch is small and
Mark> clean we'll take it."

	How about whether the patch is safe and correct?  For this
feature, the next level of semantics are tied up with the details of the
eventual implementation.  In the best of all worlds, the compiler should
be able to generate optimal code avoiding FPRs without a commandline
option to promote lazy FP context switching.

	What you described as the general concept for improved code
generation is a good goal.  I do not know whether that concept can be
implemented safely, correctly, and cleanly.  If the FPRs are available and
the compiler is not smart enough to avoid them optimally, it is better to
use them.

Mark> Will you accept a patch to implement those semantics?

	I would like to, but it depends on the details of the patch.

David


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