Subject: IEEE FP on VAX? [was Re: Trouble by compiling/configuring Perl5 on
To: NetBSD/Vax mailling liste <>
From: Brian Chase <>
List: port-vax
Date: 01/02/2001 13:02:58
On Mon, 1 Jan 2001, Sebastian Marius Kirsch wrote:
> On Sun, Dec 31, 2000 at 03:49:19PM +0100, Christophe wrote:

> > Perl5 configuration on pkgsrc got an error with the ieeefp.h include-file,
> > there is no /usr/include/machine/ieeefp.h.

> Since ieeefp.h tries to include a machine-specific header file, and
> there isn't one for the VAX since it doesn't have IEEE floats, I simply
> deleted ieeefp.h. Worked fine.
> I'm still trying to build GNU Emacs without float support, though ...

How would one go about doing an IEEE FP emulator for the VAX?  Obviously
this wouldn't be ideal in terms of performance but it would be useful.
Lots of FP dependent software assumes that you're using IEEE FP.  IMHO
this is more of a flaw in the software that makes that assumption.

Maybe emulation is the wrong approach.  Would it be better to provide a
compile time library for programs wich need IEEE FP support?

Given that we already have VAX FP instructions, I think that VAX based
IEEE support could be a lot faster in some cases than a purely integer
math based version.  You'd have to transform IEEE data into the VAX
format, run a VAX FP instruction, and then transform the result back into
IEEE.  I know it's more difficult than just that, but you should be able
leverage the existing FP support.