Supporting decimal float on additional platforms

[Rainer Orth]

I've recently looked into what it takes to support decimal float on
additional platforms (like Solaris, IRIX, and Tru64 UNIX in my case).
I've found no documentation, and while I could figure out some things
myself, I'd like to get some advice before continuing down that road.

I found that --enable-decimal-float alone is not enough.  One at least
needs to add config/t-dfprules to config.gcc, too.  In addition, the
platform <target>_scalar_mode_supported_p function needs to be augmented
accordingly.  (I haven't tried this yet; it's just from code
inspection.)

Even if this works, I now think this won't be enough and probably not
even remotely useful (if only to pass parts of the testsuite) without
libc support for the new *printf/*scanf formats, which certainly won't
be added on legacy platforms like IRIX and Tru64 UNIX, and even on
Solaris probably won't show up until DFP is fully standardized.

Comments?

        Rainer

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Rainer Orth, Center for Biotechnology, Bielefeld University