akshaytayal opened a new issue, #13439:
URL: https://github.com/apache/gluten/issues/13439

   Part of #13181 (sub-theme #13176). Found while re-enabling the Spark 4.2 UTs 
disabled in #13163.
   
   ### Problem
   Spark 4.2 (SPARK-54918) normalizes `-0.0`/NaN for `array_distinct`, 
`array_union`, `array_intersect` (and except/overlap). On Gluten the result 
keeps `-0.0`. 7 tests are disabled in `GlutenDataFrameFunctionsSuite` 
(`SPARK-54918: array_distinct / array_intersect / array_union normalizes -0.0 
to +0.0` [+ `- literals`], `SPARK-54918: array set ops normalize -0.0 and NaN 
via VALUES inline table`).
   
   ### Root cause
   - Spark 4.2 does this in the optimizer: `NormalizeFloatingNumbers` rewrites 
e.g. `array_distinct(a)` to 
`array_distinct(knownfloatingpointnormalized(transform(a, x -> 
normalizenanandzero(x))))`.
   - Gluten offloads that plan, but `ExpressionConverter` converts 
`NormalizeNaNAndZero` as a pass-through (`ChildTransformer`) because Velox has 
no normalization function, so the normalization is silently dropped. Velox 
`array_distinct`/`array_intersect`/`array_union` then keep the first-seen 
`-0.0`.
   
   ### Proposed fix
   - Velox: register a Spark scalar `normalize_nan_and_zero(REAL|DOUBLE)` 
returning `0.0` for `-0.0` and the canonical NaN for any NaN (Spark 
`DOUBLE_NORMALIZER`/`FLOAT_NORMALIZER`).
   - Gluten (after the bump): map `NormalizeNaNAndZero` to it via 
`ExpressionMappings` instead of the pass-through; keep 
`KnownFloatingPointNormalized` as a pass-through. Measure join/grouping-key 
cost (Spark also inserts `NormalizeNaNAndZero` there).
   


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