[NFC] Refactor GUFA's NullLocation and CaughtExnRefLocation into RootLocation#7822
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kripken merged 7 commits intoWebAssembly:mainfrom Aug 13, 2025
Merged
[NFC] Refactor GUFA's NullLocation and CaughtExnRefLocation into RootLocation#7822kripken merged 7 commits intoWebAssembly:mainfrom
kripken merged 7 commits intoWebAssembly:mainfrom
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tlively
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Aug 13, 2025
src/ir/possible-contents.h
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| // exnref from a catch etc. - in all these cases, all we know is the type and | ||
| // nothing more, so these are simple typed roots in the graph. |
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For the default local value and default struct field value, we know the values (zero) in addition to the types. Why are they lumped in with things like caught exceptions, for which we really don't know the value?
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They are both roots in the graph, hence the shared name for them. They are fixed points in the graph that we will never learn anything more about, with fixed values (one value is null, the other is "anything of this type", but that's the only difference).
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RootLocation, added in #7822, was overly-ambitious in how much it simplified. It turns out that there are situations where we need the same type for both a null and an "unknown" of that type, and a single RootLocation is therefore not enough (the specific situation the fuzzer found involves exnref, but perhaps others are possible too). To fix this, refactor back to two locations, NullLocation and TypeLocation, where the latter is at least shared by exn and cont as a place with an unknown value of a type.
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Both locations are just roots in the graph: sources of info that we will only
ever know the type of, and nothing more precise. It is simpler to have a
single RootLocation for them both, and will simplify adding Continuations
later.