[PATCH] D34189: AMDGPU: Avoid saving/restoring reserved m0 register

[Matthias Braun via Phabricator via llvm-commits]

MatzeB added a comment.

In https://reviews.llvm.org/D34189#779880, @tstellar wrote:

> > This changes the code to assume that m0 is available since it is
> >  reserved so we shouldn't have any longer liveranges crossing potential
> >  spill/reload places.
>
> m0 could potentially be live for the whole program, so this assumption is not correct.


So you actually do you use the register before prolog/epilogue insertion? (Note that the register allocator will not use it at the moment as it is reserved, so it would need other AMDGPU code to explicitely use it).


Repository:
  rL LLVM

https://reviews.llvm.org/D34189