Change the Literal class's operator== to be bitwise #1661
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…s Literals work properly in hashtables, fixing an infinite loop fuzz bug in the rse pass
dschuff
approved these changes
Aug 31, 2018
src/literal.h
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| bool bitwiseEqual(const Literal& other) const; | ||
| // Compare in a non-bitwise manner, which means for a nan a we have | ||
| // a != a | ||
| bool nonBitwiseEqual(const Literal& other) const; |
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This is just a little ambiguous whether the 'non' means 'not bitwise' or 'not equal'. Maybe 'typedEqual' or something like that would indicate what it is, rather than what it isn't?
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Good point, yeah.
I realized now that we don't need this function, actually - as the one place that needs it uses the existing .eq() calls (which have always been typed). So I removed this confusing function, and added comments to clarify how those other ones work.
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The change means that nan values will be compared bitwise when writing
A == B, and so the float rule of a nan is different from itself would not apply.I think this is a safer default. In particular this PR fixes a fuzz bug in the rse pass, which placed Literals in a hash table, and due to nan != nan, an infinite loop... Also, looks like we really want a bitwise comparison pretty much everywhere anyhow, as can be seen in the diff here. Really the single place we need a floaty comparison is in the intepreter where we implement f32.eq etc., and there the code was already using the proper code path anyhow.