Python: exclude loops from varBlockStep#14446
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yoff wants to merge 2 commits intogithub:mainfrom
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I tracked the "flow to self" to be in "use to next use", specifically `adjacentUseUseSameVar` can hold when `use1` = `use2`. This because `adjacentVarRefs` can in its second conjunct when `varBlockStep` holds for a loop.
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Closed in favour of #14644 |
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I tracked the "flow to self" to be in "use to next use", specifically
adjacentUseUseSameVarcan hold whenuse1=use2.This because second conjunct (the non-base case with non-consecutive basic blocks) of
adjacentVarRefscan become true whenvarBlockStepholds for a loop.Changes on tests all look good. I would like to understand why this break is not necessary for other languages, though. Do they have other assumptions that we violate?
Edit: I did find this similar restriction in C#, but they do it on the dataflow level. So the question is perhaps more, where the restriction should best be put.
Edit2: Reached out to other language teams, and likely the restriction should be on the dataflow level. The reason is that we actually want to preserve self-loops on the SSA level, since a self loop from
xtoxshould lead to a dataflow step from[post] xtox(but not to a dataflow step fromxtox). I will pursue this solution in a different PR.