Dynamically choosing a register

[Klaus D. Witzel]

On Thu, 26 Jul 2007 20:24:06 +0200, J J wrote:

>
>> From: bryce at kampjes.demon.co.uk> Date: Thu, 26 Jul 2007 11:43:43 +0100>  
>> To: exupery at lists.squeakfoundation.org> Subject: RE: Dynamically  
>> choosing a register> > > Do you mean for the cond to be evaluated at  
>> compile time in the> following?> >    (def store-to-register (reg  
>> val)>  	(cond (reg)>    	      ((number-that-means-eax) (store eax val)
> No, it can't be compile time since val will live in a field in instances  
> of MethodContext.  I can't know what val is until runtime.  What I  
> really want is a way to store in memory or another register some kind of  
> reference to a register so that I would have the option in my VM that a  
> caller can request the answer put right into the literal register of his  
> choice.

If you use some form of the traditional call/return sequence, have the  
caller reserve a #return slot at a fixed location (offset). There the  
callee can store its return value (you mentioned a way to store in  
memory). Then the caller can pop/move the value into any register it  
likes, dynamically and independent of the callee.

Cheers
Klaus

>> If so you could just generate:>    (mov t1 eax)> > Then the register  
>> allocator will try to allocate t1 in eax> and remove that move.> >  
>> BryceIs there any documentation on your mid and low level code  
>> generator?  I would like to make a lisp-like language that targets it.   
>> This way I wouldn't have to make a compiler for every processor type,  
>> but I would have full power of the CPU and no dependencies on C.
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