Re: New datatype addition to gcc

Michael Meissner wrote:


> Sriharsha <sriharsha.v@redpinesignals.com> writes:


>>My h/w personnel says that there will be TWO RAMs in the processor,
>>one is 8-bit addressible while the other is 16-bit addressible. If
>>the compiler has to do 8-bit data load/store, it uses the 8-bit RAM
>>and if it has something to do with 16-bit, it uses that RAM. This
>>sounded bizzare to me but, thats what they say (or atleast I've
>>never come across such stuff).


(snip)


> My take is you can't expect an ISO standard C implementation on such a
> machine using two address spaces, one for byte accesses and one for
> word, since structures can contain both types, and structures are
> required to have all members adjacent.


Structures are allowed to have padding for alignment. The only
restriction that I remember is that a pointer to the structure is
equivalent to a pointer to the first member. Past that, I don't know
about such restrictions. Casting pointers to a different type and
dereferencing them is not guaranteed to work, either.


It would seem to me that it might just work.


-- glen


> I suspect the best you can do is use just one address space, and
> issue multiple instructions, possibly adding a sop with attributes
> to declare static variables in the other address space. Note, once
> a pointer has been taken, GCC historically has lost all of the
> attribute information.

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