[LLVMdev] Regalloc Refactoring

Chris Lattner sabre at nondot.org
Mon Apr 16 09:01:05 PDT 2007

On Mon, 16 Apr 2007, David Greene wrote:
> Chris Lattner wrote:
>>> Doesn't that last statement actually do the rewrite?
>> Hrm, yes, yes it appears so.  Question is: doesn't this make the r2r map
>> dead?  Does something else fill it in?  My memory is hazy here :).  If it
>> is dead, we should rip it out (actually, we should make it private to the
>> coallescer function).
> I'm trying an experiment to eliminate the r2r map altogether.  Is there
> an efficient way to replace all references to a virtual register?  That
> is, given a virtual register number, is there an easy way to get a list
> of all Instructions and/or Operands that reference it?

No there isn't, unfortunately.  I'd suggest building up/maintaining the 
r2r map inside the coallescer.  Once the coallescer is done with the 
entire function, do a single pass over the function rewriting all the 
coallesced vregs.



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