Re: Cross-compiler between machines with different floating pointformat

Re: Cross-compiler between machines with different floating pointformat

[Stephen L Moshier]

> Desmond Cheung <dycheung@cs.sfu.ca> writes:
>
>> Hi,
>> 
>> I have a very important question. The porting guide says
>> "Cross-compilers between machines wieh different floating point
>>  formats have not all be made to work.
>
>At present, this only applies when the target machine is running VMS.

Has there be a bug report about this?
What is the problem with VMS?  Which backend has the problem?

Re: Cross-compiler between machines with different floating pointformat

[Geoff Keating]

> Date: Sat, 26 Aug 2000 09:41:10 -0400 (EDT)
> From: Stephen L Moshier <moshier@mediaone.net>

> Has there be a bug report about this?

It's not a bug, it's a missing feature.

> What is the problem with VMS?  Which backend has the problem?

We don't have an emulator for the VMS floating-point format, so the
compiler can't do any arithmetic at compile time on such values.  All
VMS ports (which is I believe only VAX and Alpha at this point) are
affected.
-- 
- Geoffrey Keating <geoffk@cygnus.com>

Re: Cross-compiler between machines with different floating pointformat

[Stephen L Moshier]

On Sun, 27 Aug 2000, Geoff Keating wrote:
> We don't have an emulator for the VMS floating-point format, so the
> compiler can't do any arithmetic at compile time on such values.  All
> VMS ports (which is I believe only VAX and Alpha at this point) are
> affected.

Er, the DEC VAX format emulation has been available for years and it
works fine.

I think what you are seeing is the result of a desire to choose
between VAX and IEEE numbers by a run-time compiler switch.  Because
of the way some of the preprocesor macros are defined, it would not be
possible to switch the emulator format at run time without
considerable work.  You can easily build a compiler targeting VAX
format or a different one targeting IEEE format, but not one that does
both at the same time.  This first came up in connection with the
Convex port, which has a switch to choose between the two formats, as
does alpha-vms.