C#: Get rid of negative parameter/argument data-flow positions #7658
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| newtype TArgumentPosition = | ||
| TPositionalArgumentPosition(int i) { i = any(Parameter p).getPosition() } or | ||
| TQualifierArgumentPosition() or | ||
| TImplicitCapturedArgumentPosition(SsaCapturedEntryDefinition def) |
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This looks risky! This might introduce virtual-dispatch-sized blowups in any part of the dataflow lib that work with an argument without having joined that to a call target.
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Or is this a case where the call-callee relation is 1-1?
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Performance-wise this should be no different from before, where we translated each SsaCapturedEntryDefinition into a magic number (using equivalenceRelation), and used that magic number as both parameter and argument positions.
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But now that I think about it, this can probably be made a bit nicer (and smaller) by simply using the variable that is captured as the positions.
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I guess the bad case requires some sort of convoluted setup where a single call might dispatch to many different lambdas (or other kinds of closures) that each capture some variable, and that this single call somehow provides a value in the corresponding argument-position(s). I don't know if such a construction is even possible - it depends on how these arguments are recognised.
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This PR makes use of #7260 to get rid of negative parameter/argument positions. Negative indices were used in two places:
-1: representing qualifiers/thisparameters.-2 ..: used to model flow through captured variables.The former are used in flow summaries, which means that
Argument[Qualifier]replacesArgument[-1]. The latter are only used internally, but getting rid of those as well means that we can remove some hackyequivalenceRelation-based ranking.