[IR] Handle NaN in StructuralEqual and StructuralHash #17249
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Prior to this commit, `NaN` values did not have any special handling in either `StructuralEqual` or `StructuralHash`. `StructuralEqual` checked whether the LHS and RHS were within some tolerance of each other. If the LHS and RHS are both `NaN`, this would evaluate to false. The updated `StructuralEqual` now checks for this case, and returns true if both sides are `NaN`. `StructuralHash` used the bit-pattern of a floating-point number to compute the hash. A `NaN` value may have any non-zero value in its mantissa, and so this could produce distinct hashes for ASTs that differ only by the choice of non-zero value. The updated `StructuralHash` uses the same `std::numeric_limits<double::quiet_NaN()` value for all `NaN` values. With these changes, `StructuralEqual` and `StructuralHash` can now compare two IR functions, even if they contain `NaN`. Closes apache#17247
tqchen
approved these changes
Aug 19, 2024
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Prior to this commit,
NaNvalues did not have any special handling in eitherStructuralEqualorStructuralHash.StructuralEqualchecked whether the LHS and RHS were within some tolerance of each other. If the LHS and RHS are bothNaN, this would evaluate to false. The updatedStructuralEqualnow checks for this case, and returns true if both sides areNaN.StructuralHashused the bit-pattern of a floating-point number to compute the hash. ANaNvalue may have any non-zero value in its mantissa, and so this could produce distinct hashes for ASTs that differ only by the choice of non-zero value. The updatedStructuralHashuses the samestd::numeric_limits<double::quiet_NaN()value for allNaNvalues.With these changes,
StructuralEqualandStructuralHashcan now compare two IR functions, even if they containNaN.Closes #17247