On Tue, 2005-08-23 at 16:44 +0200, Bernd Schmidt wrote:
> Andreas Krebbel wrote:
> 
> > Ok I understand that implementing the special lifeness analyzers in global 
> > alloc
> > using the df.c framework would ease reusing it somewhere else. But my 
> > question
> > was more basic.
> > So do you agree that using one lifeness analyzer for checking what
> > an optimizer step has done based on a second lifeness analyzers output
> > is wrong? If so what is the way to fix this? Going back to the normal 
> > analyzer to
> > be used in global alloc would make global alloc creating worse code. But on 
> > the other hand
> > using the global alloc lifeness analyzer everywhere else would be a change 
> > which nobody would agree with in the current development stage.
> 
> Jim Wilson once suggested we should just emit insns to make sure every 
> register is initialized and be done with it - problem solved.  
But doesn't this actually the information you get worse?

Partial liveness gives you an answer, which is "It's not really live
here, because it's not defined"

If you make them all defined, then it's going to be live where it wasn't
before, even though it's not really *used* over those paths.


> I had 
> started to work on that, if people think it's a good idea I can dig that 
> stuff out again.
> 
> 
> Bernd

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