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

[Kevin Buettner <kevinb@cygnus.com>]

On Aug 17,  1:12pm, Andrew Cagney wrote:

> > The fly in the ointment is that the IA-64 also has a quad precision
> > real type whose width is 128 bits (1 bit sign, 15 bit exponent,
> > 112 bit significand).
> 
> Ulgh!  So we now need two IA-64 floating point types, any suggestion for 
> a name? Does:
> 
> 	ia64_ext
> 	ia64_quad
> 
> look ok (and please no one look at the VAX :-).

Well, actually, there are a total of seven data types that the IA-64
supports.  (However, two of them are integer types.) From section 5.1
of the Intel IA-64 Architecture Software Developer's Manual; Volume 1: 
IA-64 Application Architecture:

    Six data types are supported directly:  single, double,
    double-extended real (IEEE real types); 64-bit signed integer,
    64-bit unsigned integer, and the 82-bit floating point register
    format.  A "Parallel FP" format where a pair of IEEE single
    precision values occupy a floating point registers significand is
    also supported.  A seventh data type, IEEE-style quad-precision,
    is supported in software routines.  A future architecture
    extension may include additional support for the quad-precision
    real type.

Anyway, my objection to using ``ia64_ext'' for the 82-bit register
type stems from the fact that this name would probably be more
appropriate for the 80-bit double-extended type.  Especially since
this is the convention already used for x86.  How 'bout this instead?

    ia64_ext	- 80-bit double-extended
    ia64_reg	- 82-bit fp register
    ia64_quad	- 128-bit quad-precision

Online documentation on the IA-64 floating point formats may be found at:

    http://devresource.hp.com/devresource/Docs/Refs/IA64ISA/fp_program4.html 

Roughly the same material may also be found in chapter 5 of the
following PDF file:

    ftp://download.intel.com/design/IA-64/Downloads/24531702s.pdf

Kevin