[PATCH] D46870: [MachineScheduler] Don't enforce some hazard checks pre-RA.

[Jonas Paulsson via Phabricator via llvm-commits]

jonpa added inline comments.


================
Comment at: lib/CodeGen/MachineScheduler.cpp:2257
 
   // Bump the cycle count for issue group constraints.
   // This must be done after NextCycle has been adjust for all other stalls.
----------------
javed.absar wrote:
> Probably the comment here needs updating if we are going to change behaviour. 
> There is another problem - 
> "Single Issue " relies on BeginGroup/EndGroup and that is not just PostRA related.
So, with our abstract machine as a model, what specifically does "Single Issue" imply? Is this on a particular target?

To me this sounds like such an instruction should have a doubled value of NumMicroOps, which then pushes CurrCycle further. Per the basic premise of this patch, I would have hoped this is good enough pre-RA. Why not?

Would it help to also guard this change so that only targets that do post-RA scheduling is affected?



https://reviews.llvm.org/D46870