Dataflow: Simplify revFlowThrough #18355
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Observations: * revFlowThrough can be much larger than the other reverse-flow predicates, presumably when there are many different innerReturnAps. * It is only ever used in conjunction with flowThroughIntoCall, which can therefore be pushed in, and several of its parameters can thereby be dropped in exchange for exposing `arg`. * `revFlowThroughArg` can then be trivially inlined. Result: on repository `go-gitea/gitea` with PR github#17701 producing a wider selection of access paths than are seen on `main`, `revFlowThrough` drops in size from ~120m tuples to ~4m, and the runtime of the reverse-flow computation for dataflow stage 4 goes from dominating the forward-flow cost to relatively insignificant. Overall runtime falls from 3 minutes to 2 with substantial ram available, and presumably falls much more under GHA-style memory pressure.
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hvitved
approved these changes
Dec 21, 2024
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Observations:
arg.revFlowThroughArgcan then be trivially inlined.Result: on repository
go-gitea/giteawith PR #17701 producing a wider selection of access paths than are seen onmain,revFlowThroughdrops in size from ~120m tuples to ~4m, and the runtime of the reverse-flow computation for dataflow stage 4 goes from dominating the forward-flow cost to relatively insignificant. Overall runtime falls from 3 minutes to 2 with substantial ram available, and presumably falls much more under GHA-style memory pressure.