[PATCH] D14719: Track pristine registers in terms of register units.

[Quentin Colombet via llvm-commits]

qcolombet added a comment.

For the record, I am kind of uncomfortable with Matthias’ suggestion because we slightly modify the output of the function. This is not wrong of course, but I believe that for most backend this is not needed because they already know what the output was and were doing the right thing. I.e., we add a compile time overhead for no benefit.

My concern is that this may have a significant impact on backend with a lot of registers (i.e., GPUs). I believe the effect would be mitigated by the fact that, those usually don’t have calls, i.e., they likely don’t have CSRs saved.

The bottom line is if we go with that change we should be aware of potentiel downside for everybody and we need to balance whether a target specific fix would be more appropriate.

That being said, Matthias seems fine with the suggested change, so we might just carry on.

Cheers,
-Quentin


Repository:
  rL LLVM

http://reviews.llvm.org/D14719