[PATCH] D47509: [AMDGPU] Track occupancy in MFI

[Stanislav Mekhanoshin via Phabricator via llvm-commits]

rampitec created this revision.
rampitec added a reviewer: vpykhtin.
Herald added subscribers: javed.absar, t-tye, tpr, dstuttard, yaxunl, nhaehnle, wdng, kzhuravl, arsenm.

Keep track of achieved occupancy in SIMachineFunctionInfo.
At the moment we have a lot of duplicated or even missed code to
query and maintain occupancy info. Record it in the MFI and
query in a single call. Interfaces:

- getOccupancy() - returns current recorded achieved occupancy.
- getMinAllowedOccupancy() - returns lesser of the achieved occupancy

and the lowest occupancy we are ready to tolerate. For example if
a kernel is memory bound we are ready to tolerate 4 waves.

- limitOccupancy() - record occupancy level if we have to lower it.
- increaseOccupancy() - record occupancy if scheduler managed to

increase the occupancy.

MFI takes care of integrating different checks affecting occupancy,
including LDS use and waves-per-eu attribute. Note that scheduler
starts with not yet known register pressure, so has to record either
limit or increase in occupancy after it is done. Later passes can
just query a resulting value.

New interface is used in the active scheduler and NFC wrt its work.
Changes are also made to experimental schedulers to use it and record
an occupancy after they are done. Before the change waves-per-eu was
ignored by experimental schedulers and tolerance window for memory
bound kernels was not used.


https://reviews.llvm.org/D47509

Files:
  lib/Target/AMDGPU/GCNIterativeScheduler.cpp
  lib/Target/AMDGPU/GCNSchedStrategy.cpp
  lib/Target/AMDGPU/GCNSchedStrategy.h
  lib/Target/AMDGPU/SIISelLowering.cpp
  lib/Target/AMDGPU/SIMachineFunctionInfo.cpp
  lib/Target/AMDGPU/SIMachineFunctionInfo.h

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