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

[Jonas Paulsson via Phabricator via llvm-commits]

jonpa added a comment.

In https://reviews.llvm.org/D36795#844373, @uweigand wrote:

> 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.


Ah, I see - thanks for explaining.


https://reviews.llvm.org/D36795