Refactor LSRA's heuristics selection #52832
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kunalspathak
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- summary docs - Removed DEFAULT_ORDER - Added order seq ID
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@dotnet/jit-contrib |
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jitstressregs failure is related to #52945 |
BruceForstall
requested changes
May 18, 2021
| // Apply a simple mask-based selection heuristic, and return 'true' if we now have a single candidate. | ||
| bool applySelection(int selectionScore, regMaskTP selectionCandidates DEBUG_ARG(RegisterScore* registerScore)) | ||
| // Perform register selection and update currentInterval or refPosition TODO: | ||
| FORCEINLINE regMaskTP select(Interval* currentInterval, |
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Are all the FORCEINLINE really necessary?
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allocateReg is a hot method and I didn't want to add function call cost to it so marked everything FORCEINLINE. Is there a downside that you see with it?
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I suppose it's ok if it's really necessary because it's known to be hot.
src/coreclr/jit/lsra.cpp
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I don't see the reference line of your comment. Can you copy/paste the text where you see the leftover TODO?
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I think all the ones I flagged had your alias, so just search for that.
BruceForstall
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May 19, 2021
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Refactor register selection
allocateReg()method so that the selection heuristics can be applied in different and dynamic order instead of hardcoded and sequential. SinceallocateReg()operates on local method variables, I had to writeRegisterSelectionclass that contains all the register selection related variables.select()method would do the register selection. Most of the changes are moving around the existing code inallocateReg()to its own separate methods ofRegisterSelectionclass.For now, the ordering is not changed, but in
DEBUG, I have included aCOMPlu_variable thatLsraOrderingthat will let the user set the ordering. It takes charactersAthruQand each character corresponds to a heuristics. InDEBUGthe heuristics will be applied based on the provided sequence toLsraOrdering.There are no asmdiffs with this change.
I did throughput analysis of this change using pin and do not see any impact. All the diffs are within the the error range.
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Contributes to #43318