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Re: Identify IEE
- From: "N.M. Maclaren" <nmm1 at cam dot ac dot uk>
- To: Uros Bizjak <ubizjak at gmail dot com>
- Cc: FX <fxcoudert at gmail dot com>, GCC Development <gcc at gcc dot gnu dot org>, Fortran List <fortran at gcc dot gnu dot org>
- Date: 03 Jul 2014 09:28:50 +0100
- Subject: Re: Identify IEE
- Authentication-results: sourceware.org; auth=none
- References: <4ACBAD61-A346-46EE-9387-266D5B378A56 at gmail dot com> <CAFULd4Y-eHeiZ4UhO5=Eh_2CUj=NtZy54EJut1wnEwOhG7hxsA at mail dot gmail dot com> <CAFULd4avGpzXV=oV8mEag9HA1a6RqP89AKctEQOGNjBkm6FKvQ at mail dot gmail dot com>
On Jul 3 2014, Uros Bizjak wrote:
Maybe a new hook should be introduced instead: TARGET_IEEE_FORMAT_P
(mode). For some targets, even soft-fp supports required rounding
modes and can generate exceptions.
Before doing anything, it would be a good idea to decide on what IEEE
conformance means. The 1984 standard was very much an assembler-level
one, and the 2008 one isn't much better. Until recently, even at the
hardware level, the support for it was very patchy. Among gcc targets,
there have been at least the following possibilities:
Absolutely none
The representation, excluding many of the exceptional values
The representation in full, but not the semantics
The semantics, but not the mode settings
The semantics and mode settings, but not the trapping
And those are only the ones that I have seen! Real gcc experts could
probably add to them.
Regards,
Nick Maclaren.