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Re: Languages, languages ... (was: 754R and Reproducibility)
Guillaume Melquiond <guillaume.melquiond@xxxxxxxxxxx> wrote:
Le mercredi 11 juillet 2007 ` 03:59 -0400, Michel Hack a icrit :
It is true that a specification at the level I just described is not what
most programmers want (basically, an assembly-language level), but I claim
that it is necessary to enable a small group of programmers to provide the
conformance at the higher levels (basically, compiler writers). So I am
not at all opposed to providing clear conformance requirements at the
language level (which was missing in 754(1985)) -- what I'm complaining
about is dropping conformance discussions at the lower levels altogether.
I may be misunderstanding. But it seems like you would like to require a
set of floating-point operations to be available directly at
assembly-language level. I think this is a really drastic move.
For example, there are some DSP processors that have integer arithmetic
units only, yet the platforms they are embedded into provide a software
implementation of floating-point arithmetic (thanks to some help from
the processor, like the ability to count leading zeros, performances are
not as bad as one may expect). Such a platform could never claim
conformance with the standard, as absolutely nothing would be available
at assembly-language level.
Without speaking for Michel, that doesn't follow. Provided that the
standard doesn't say that the basic primitives have to be implemented
in hardware or as instructions, you can define a set of library calls
(or macros) for assembler just as easily as you can for any other
language. Mercury Machine Code had 'Quickies' (macros), and that is
going back a bit :-)
Regards,
Nick Maclaren,
University of Cambridge Computing Service,
New Museums Site, Pembroke Street, Cambridge CB2 3QH, England.
Email: nmm1@xxxxxxxxx
Tel.: +44 1223 334761 Fax: +44 1223 334679