RFC: split ColdFire from m68k backend

Bernardo Innocenti bernie@develer.com
Sat May 8 01:10:00 GMT 2004

Giovanni Bajo wrote:
> Andreas Schwab wrote:
>>>>I wouldn't mind having a modernized m68k backend. :-)
>>>  What things have to be changed to modernized the m68k backend?
>>One thing that would be nice to have is to convert the
>>prologue/epilogue to RTL.
> Also, m68k is the major cc0 target at the moment. Making it drop cc0 support
> would help cleaning up the compiler. You can ask Kazu Hirata, as he lately
> modified h8300 to drop cc0.

I agree with Giovanni about the need to move away from
cc0.  Another major cc0 target is the AVR, perhaps much
more popular than the m68k as of today.

I'd normally strongly oppose a change leading to
massive code duplication, but Peter's proposal of
splitting the m68k backend into old-m68k and ColdFire
is rather justified.

There's no chance Motorola will extend the m680x0
line of processors, therefore the m68k backend will
never require major enhancements and it will most
probably slowly become obsolescent.

On the other hand, the latest ColdFire processors
are becoming rather complex with FPU, MMU and MAC
units.  More instruction set extensions are to be
expected from next generation cores.

The M680x0 and MCF5xxx architectures were similar
but incompatible from the beginning, and they
*will* diverge even more in the future.

  // Bernardo Innocenti - Develer S.r.l., R&D dept.
\X/  http://www.develer.com/

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