[threads] Allow i31refs of mixed shareability to compare equal #6752
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Normally, values of different types can never compare equal to each other, but since i31refs are not actually allocations, `ref.eq` has no way to differentiate a shared i31ref and an unshared i31ref with the same value, so it will report them as equal. Update the implementation of value equality to reflect this correctly.
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How does the spec define this? I'm curious to understand what "not actually an allocation" translates to in spec-lese. |
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The spec uses syntactic equality on reference values, most of which are of the form |
tlively
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#6752)" Allowing Literals with different types to compare equal causes problems for passes that want equality to mean real equality, e.g. because they are using literals as map keys or because they otherwise need to use them interchangeably. At a minimum, we would need to differentiate a `refEq` operation where mixed-shareability i31refs can compare equal from physical equality on Literals, but there is also appetite to disallow mixed-shareability ref.eq at the spec level. See WebAssembly/shared-everything-threads#76.
tlively
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Jul 17, 2024
#6752)" (#6761) Allowing Literals with different types to compare equal causes problems for passes that want equality to mean real equality, e.g. because they are using literals as map keys or because they otherwise need to use them interchangeably. At a minimum, we would need to differentiate a `refEq` operation where mixed-shareability i31refs can compare equal from physical equality on Literals, but there is also appetite to disallow mixed-shareability ref.eq at the spec level. See WebAssembly/shared-everything-threads#76.
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Normally, values of different types can never compare equal to each
other, but since i31refs are not actually allocations,
ref.eqhas noway to differentiate a shared i31ref and an unshared i31ref with the
same value, so it will report them as equal. Update the implementation
of value equality to reflect this correctly.