Re: [rfc] Add some more floatformat types ....

Mark Kettenis
2001-08-16T16:55:00Z

Andrew Cagney <ac131313@cygnus.com> writes:

> > The attached adds the floatformats:
> >
> > floatformat_i387_ext80;
> > floatformat_i387_ext96;
> >
> > Explicitly sized x86 float formats.
> >
> > Depending on where/how it is stored,
> > an i386 extended could use 80 (10 bytes)
> > or 96 (12 bytes).

Andrew, I thought I (implicitly) raised some objections to this
change. See

http://sources.redhat.com/ml/gdb/2001-07/msg00401.html

To clarify things a bit: The ISA (that stands for Istruction Set
Architecture doesn't it) defines a single 80-bit extended floating
point format. On top of that floating point format most ABI's build a
a 96-bit extended floating point type (e.g. GCC's `long double'). I'd
like GDB to somehow maintain this concept, by *not* introducing the
floatformat_i387_ext80 and floatformat_i387_ext96 types you propose.
Instead we should make the distinction at the builtin_type_* level.
By making the 80-bit and 96-bit builtin_type_* variants share the same
underlying floatformat_* variable, we can easiliy check whether two
floating point formats on the ABI level share the same encoding on the
ISA level.

Something similar might hold for IA-64.

The other two fixes seem obvious to me.

Mark