Subject: Re: IEEE FP on VAX? [was Re: Trouble by compiling/configuring Perl5
To: Brian Chase <>
From: David Brownlee <>
List: port-vax
Date: 01/02/2001 18:22:22
On Tue, 2 Jan 2001, Brian Chase wrote:

> 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.

	I imagine most of the work would be handling the underflow /
	overflow conditions 'correctly' according to the IEEE spec.

		David/absolute		-- No hype required --