Re: [avr-llvm-devel] Load / Store

[Weddington, E. <Eri...@at...>]

 

> -----Original Message-----
> From: John Myers [mailto:ato...@gm...] 
> Sent: Thursday, November 04, 2010 11:24 AM
> To: Borja Ferrer
> Cc: avr...@li...
> Subject: Re: [avr-llvm-devel] Load / Store
> 
> 
> 
> On Thu, Nov 4, 2010 at 7:52 AM, Borja Ferrer 
> <bor...@gm...> wrote:
> 
> 
> 	 As far as i know LLVM has address space identifiers in 
> its IR so in theory it's possible to do it, however i havent 
> looked yet how to implement this in the backend. Another 
> thing, i havent checked if clang supports named address 
> spaces, i know gcc does, but at the end we should end up 
> using only clang as the frontend?
> 	
> 	Can somebody clarify me if GCC has support for 24 bit 
> ptrs for largest devices and 8 bit ptrs for the smallests? 
> i'm only used to 16 bit ptrs so i dont what gcc does outside 
> this case.
> 	Implementing 24bit ptrs should be possible, same for 8bit.

AVR GCC currently only has 16-bit pointers. I don't know if it is possible in the generic parts of GCC to have 24-bit pointers. But I think in this case, avr-llvm should have 8, 16, and 24-bit pointers. Not sure about 32-bit pointers yet.


> If we want to have generic pointers (like Keil, SDCC...) we 
> will also need 32 bit pointer. Generic pointers allow the 
> user to create a pointer that can access all the address space's.

I'm not sure that something like that would ever be used effectively on the AVR. At the moment, I suggest avoiding generic pointers.