[PATCH] Allow the RegisterCoalescer to remove copies to reserved registers

[hfinkel at anl.gov]

In http://reviews.llvm.org/D6978#108879, @qcolombet wrote:

> > Perhaps we should restrict to the case of a reserved physical register?
>
>
> Reserved registers are a different story and in that case, by all means, this is a good idea :).


Good, will do :)

One more thing, I had asked:

> One thing that is not clear to me: Do I need to do anything special to update the 'dead def' live range corresponding to the updated PHYSREG?


Do you know if I need to do anything specific here, or will the register replacement code that already exists take care of this in a sufficient way?

Thanks again!

> 

> 

> > I can certainly try that if you don't like my suggestion above.

> 

> 

> I like your suggestion, the copy propagation improvement is just another angle of attack I was envisioning. It may be generally useful, but if we do not have motivating example, I would leave that for later.

> 

> Thanks,

> -Quentin



http://reviews.llvm.org/D6978

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