[PATCH] D22718: MachineFunction: Remove AllVRegsAllocated property

[Matthias Braun via llvm-commits]

MatzeB added a comment.

In https://reviews.llvm.org/D22718#495247, @kparzysz wrote:

> In https://reviews.llvm.org/D22718#495216, @MatzeB wrote:
>
> > On the other hand I would find it very troubling if "AllVRegsAllocated" would just have an abstract meaning of a pass that runs after the register allocator. Why would is be important to run a certain place in the pass pipeline?
>
>
> For a pass, yes, altough there are passes that can run in both scenarios (MachineLICM, IIRC).  What I was thinking about were utility routines that can be called at various times.  In our internal Hexagon repo we have to maintain super-register liveness via implicit operands.  We have a function that updates those and it's called from places like, for example, loadRegFromStackSlot.  This function does not know where in the optimization pipleline it was called from.  Checking whether the destination register is physical or virtual is not sufficient, because we really only want to do this after RA has completed.


I find this a minor problem to solve if the function works fine before RA and is just unnecessary. There are so many other function preconditions that we do not explicitely test or that may not be possible to test. I'm not saying checking preconditions isn't useful but I don't find it a convincing argument in this case to keep the AllVRegsAllocated property around.


Repository:
  rL LLVM

https://reviews.llvm.org/D22718