Use global invariant for dead branch detection #525
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michael-schwarz
approved these changes
Jan 19, 2022
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While debugging other incremental issues, I realized that some dead branch warnings go missing. This was because dead branch detection used global hashtables in the
Deadcodemodule to accomplish its job.This PR replaces that with the general global invariant mechanism. While doing so, it switches from using locations to nodes, making it even more robust for the incremental case.
A useful side effect of the latter is that now dead branch warnings are also given for subexpressions of short-circuting conditions (e.g.
a && b). Previously this was broken since both branching nodes had the same location, which quietly broke the location-based hashtable.This PR is on top of #391. On master the incremental problem doesn't appear because postsolving isn't done incrementally, so all the dead branch warnings get recreated anyway.
TODO