GCC port

David Brown david@westcontrol.com
Fri Nov 22 11:52:00 GMT 2013


On 21/11/13 17:02, Jeff Law wrote:
> On 11/21/13 03:56, Brian Drummond wrote:
>> On Thu, 2013-11-21 at 11:23 +0100, David Brown wrote:
>>> On 21/11/13 09:22, eljedi . wrote:
>>>> Thank you guys for the answers.
>>>> Now I have a lot to read and learn.
>>>>
>>>>
>>>> On Wed, Nov 20, 2013 at 8:17 PM, Oleg Endo <oleg.endo@t-online.de>
>>>> wrote:
>>>>> On Wed, 2013-11-20 at 19:25 +0100, eljedi . wrote:
>>>>>> Thank you Jonathan for the quick reply.
>>
>>> The AVR is in fact an 8-bit cpu - I think it is the only 8-bit target
>>> that is supported by gcc mainline.
>>>
>>> For a 16-bit cpu, look at the msp430 port.  It has just recently been
>>> added to mainline - previously it was developed outside the main gcc
>>> tree.  But being a new port, or at least a newly cleaned up port, it
>>> should be a good example to start with.
>>
>> Excellent news! Which release version includes (or will include) the
>> MSP430?
> Good grief, no.  Not the msp430 which has odd sized pointers.  If you're
> going to do a 16 bit port, do a pure one.  Anything with PSImode should
> be avoided as a learning experience.
> 
> For someone trying to learn, I'd stick with one of the simple 32bit
> embeded riscy processors.  v850 for example.
> 

The 20-bit pointers are only used for some msp430 devices, and even then
only in "large" memory models.  I haven't looked at the port code at
all, but I am sure it will be possible to gloss over the 20-bit stuff
when reading the code for learning purposes.  Apart from the 20-bit
support, the msp430 should be a pretty nice example as it has a mostly
orthogonal ISA with 16 16-bit registers.  And since it was updated and
contributed to mainline recently by gcc experts, I expect it to be a
good, modern gcc port.

I have no idea about the v850, however - it may be more appropriate,
despite being 32-bit rather than 16-bit.  Almost certainly, it would be
useful for the OP to look at more than one architecture anyway.





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