[PATCH] D36795: [SystemZ] Increase number of LOCRs emitted by passing regalloc hints

[Ulrich Weigand via Phabricator via llvm-commits]

uweigand added a comment.

Oh, and just comment on this:

> BTW, I don't quite understand the purpose of updateRegAllocHint(). It seems to be run during coalescing, but that's before getRegAllocationHints() has ever been called. So what is being updated?

I understand this is about something else: maintaining the MachineRegisterInfo set/getRegAllocationHint data.  It seems the ARM target sets up the MRI hints in a special pass ahead of time, and then *uses* the MRI hints in its implementation of getRegAllocationHints.  However, for this to be useful the MRI hints need to be updated for the effects of register coalescing; the updateRegAllocHint allows the target to do just that.

Since your implementation of getRegAllocationHints doesn't actually make any use of the MRI hints, you don't need to implement updateRegAllocHint either.


https://reviews.llvm.org/D36795