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Re: Correct RTL representation of reg-stack registers


On Tue, Apr 06, 1999 at 05:27:44PM -0700, Richard Henderson wrote:
> On Wed, Apr 07, 1999 at 01:42:19AM +0200, Jan Hubicka wrote:
> > Well, I always believe that one of the RTL invariants is that all used
> > and set registers are explicitly mentioned in the insn representation,
> > so I would consider this as broken rtl in the samy way as the previous.
> 
> Perhaps.  I don't think it is _so_ wrong -- its concise, and does
> not suffer from note lossage during splitting.
> 
> > BTW whats about modelig it little bit like "normal stack" in alternate
> > adressing mode (so create some new "fp stack pointer" and implement pushing
> > and popping instruction by incrementing and decrementing this pointer).
> > The register references can be then something like
> > (reg (plus (reg <stack pointer>) 4))
> 
> This was also discussed once upon a time.  I think the outer
What was the result?
> reference had been named INDREG -- reusing MEM seemed dangerous.
Maybe we can even keep the normal registers and define, that
stack register = <stack pointer> - REGNO (register) 

All instruction can be parallers using, incrementing or decrementing the
stack pointer.
We can emit EQUAL_TO notes (or note the exact value of stack pointer somewhere
in the rtls) to allow generating of insns.

With such solution we might stay with old RTL codes....

Honza
> 
> 
> r~

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