Re: porting GCC to a micro with a very limited addressing mode --- what to write in LEGITIMATE_ADDRESS, LEGITIMIZE_ADDRESS and micro.md ?!

[Jeff Law <law at redhat dot com>]

On 01/25/10 11:21, Sergio Ruocco wrote:
> Gabriel Paubert wrote:
>    
> > On Mon, Jan 25, 2010 at 01:34:09PM +0100, Sergio Ruocco wrote:
> >      
> > > Hi everyone,
> > >
> > > I am porting GCC to a custom 16-bit microcontroller with very limited
> > > addressing modes. Basically, it can only load/store using a (general
> > > purpose) register as the address, without any offset:
> > >
> > > 	LOAD (R2) R1	; load R1 from memory at address (R2)
> > > 	STORE R1 (R2)	; store R1 to memory at address (R2)
> > >
> > > As far as I can understand, this is more limited than the current
> > > architectures supported by GCC that I found in the current gcc/config/*.
> > >        
> > The Itanium (ia64) has the same limited choice of addressing modes.
> >
> > 	Gabriel
> >      
> Thanks Gabriel.
>
> I dived into the ia64 md, but it is still unclear to me how the various
> parts (macros, define_expand and define_insn in MD etc.) work together
> to force the computation of a source/dest address plus offset into a
> register... can anyone help me with this ?
>    
GO_IF_LEGITIMATE_ADDRESS is what you need to be looking at.

jeff