Target ABIs with 16bit ints.

Target ABIs with 16bit ints.

[Nathan Sidwell]

Hi,
Something's just popped concerning targets with 16bit ints. Paul Koning
reminds me that the pdp11 target has such. This conflicts with the gcc
& gnu coding standards.

doc/portability.texi says
'The main goal of GCC was to make a good, fast compiler for machines in
the class that the GNU system aims to run on: 32-bit machines that address
8-bit bytes and have several general registers.'

the gnu coding standards additionally say
'However, don't make any effort to cater to the possibility that an
@code{int} will be less than 32 bits.  We don't support 16-bit machines
in GNU.'

How many 16bit int abi targets do we have?
How important are they now? (Yes, I know the pdp11 /was/ important :)
Should we deprecate them?

nathan
-- 
Dr Nathan Sidwell   ::   http://www.codesourcery.com   ::   CodeSourcery LLC
          'But that's a lie.' - 'Yes it is. What's your point?'
nathan@codesourcery.com : http://www.cs.bris.ac.uk/~nathan/ : nathan@acm.org

Re: Target ABIs with 16bit ints.

[DJ Delorie]

> doc/portability.texi says
> 'The main goal of GCC was to make a good, fast compiler for machines in
> the class that the GNU system aims to run on: 32-bit machines that address
> 8-bit bytes and have several general registers.'

There's a big difference between "run on" and "target".  The *host*
must have 32 bit ints.  The target doesn't need to.

Re: Target ABIs with 16bit ints.

[Nathan Sidwell]

DJ Delorie wrote:
>>doc/portability.texi says
>>'The main goal of GCC was to make a good, fast compiler for machines in
>>the class that the GNU system aims to run on: 32-bit machines that address
>>8-bit bytes and have several general registers.'
> 
> 
> There's a big difference between "run on" and "target".  The *host*
> must have 32 bit ints.  The target doesn't need to.
yes, but this needs to be made much clearer. Some parts of gcc source
(libgcc) do then need to target smaller machines. And some parts of
gcc will not support those ABIs or not be language conforming
(C++ & its stl, c99 mode, java? at least)

nathan

-- 
Dr Nathan Sidwell   ::   http://www.codesourcery.com   ::   CodeSourcery LLC
          'But that's a lie.' - 'Yes it is. What's your point?'
nathan@codesourcery.com : http://www.cs.bris.ac.uk/~nathan/ : nathan@acm.org

Re: Target ABIs with 16bit ints.

[Michael Matz]

Hi,

On Mon, 14 Oct 2002, Nathan Sidwell wrote:

> doc/portability.texi says
> 'The main goal of GCC was to make a good, fast compiler for machines in
> the class that the GNU system aims to run on: 32-bit machines that address
> 8-bit bytes and have several general registers.'

This statement doesn't conflict with anything.  First it's only stating an
intent not any state, and second it even only talks about the past.

> 'However, don't make any effort to cater to the possibility that an
> @code{int} will be less than 32 bits.  We don't support 16-bit machines
> in GNU.'

And this general guideline in the GNU coding standards also doesn't
necessarily apply to the compiler itself.  Sure, people who want to have
it working on funny architectures need to do the work on their own, but
that doesn't mean we should prevent them from doing so by discouraging
that.

> How many 16bit int abi targets do we have?

avr is 8bit or 16bit (command line).  m68k is 16 or 32 bit, dsp16xxx is 16
bit, mn10200 is 16 bit, m68hc11 is 16 or 32 bit, stormy16 is 16 bit, ip2k
is 8 bit.

> How important are they now? (Yes, I know the pdp11 /was/ important :)
> Should we deprecate them?

I don't think so.


Ciao,
Michael.

Re: Target ABIs with 16bit ints.

[Michael Matz]

Hi again,

On Mon, 14 Oct 2002, Michael Matz wrote:

> avr is 8bit or 16bit (command line).  m68k is 16 or 32 bit, dsp16xxx is 16
> bit, mn10200 is 16 bit, m68hc11 is 16 or 32 bit, stormy16 is 16 bit, ip2k
> is 8 bit.

Grrr.  h8300 also is 16 or 32 bit.


Ciao,
Michael.

Re: Target ABIs with 16bit ints.

[Mike Laman]

I'm also working on a cross compiler port to a 16 bit compiler.

Please let use small/old CPUs too!

Thanks,
Mike
----- Original Message -----
From: "Michael Matz" <matz@suse.de>
To: "Nathan Sidwell" <nathan@codesourcery.com>
Cc: <gcc@gcc.gnu.org>
Sent: Monday, October 14, 2002 2:18 PM
Subject: Re: Target ABIs with 16bit ints.


> Hi again,
>
> On Mon, 14 Oct 2002, Michael Matz wrote:
>
> > avr is 8bit or 16bit (command line).  m68k is 16 or 32 bit, dsp16xxx is
16
> > bit, mn10200 is 16 bit, m68hc11 is 16 or 32 bit, stormy16 is 16 bit,
ip2k
> > is 8 bit.
>
> Grrr.  h8300 also is 16 or 32 bit.
>
>
> Ciao,
> Michael.
>
>