SSA: Distinguish between has and controls branch edge. #19567
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| /** | ||
| * Holds if this guard evaluating to `branch` controls the control-flow | ||
| * branch edge from `bb1` to `bb2`. That is, following the edge from | ||
| * `bb1` to `bb2` implies that this guard evaluated to `branch`. |
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Perhaps add an example to illustrate how this can differ from hasBranchEdge.
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It's the general distinction between direct and indirect control. E.g. if (g) .. vs. b = g; .. if (b) ... I can of course elaborate the qldoc here, but I'm thinking perhaps just leaving it as-is, and then focusing on a more comprehensive elaboration in the upcoming shared Guards library - eventually these two predicates will simply be taken directly from that shared library.
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Yes, that is what I was thinking; simply add that example to the QL doc.
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Dca looks completely fine. This is technically a breaking change for any users of the SSA data flow integration module, so I've added a change note to the SSA qlpack. |
For languages without a guards implication logic,
hasBranchEdgeandcontrolsBranchEdgeis the same thing, but libraries like SSA should distinguish between them. This might theoretically improve barrier guards a bit for Java, but more importantly this prepares us a bit for the introduction of a shared Guards library.