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

Kevin Buettner
2001-08-17T11:12:00Z

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