Explicitly enforce int4 bit representation with ignored high bits. #119
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The previous implementation using a bit-field leaves the exact representation implementation-defined, with some platforms storing bit-fields packed left-to-right, others right-to-left, and the masked bits unspecified. This complicates serialization and vectorized conversions. With this change, we now explicitly store the value in the lower 4 bits, and leave the upper 4 bits unspecified. The type is constructed in such a way that correctness is preserved regardless of the upper bit values. PiperOrigin-RevId: 578735344
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Explicitly enforce int4 bit representation with ignored high bits.
The previous implementation using a bit-field leaves the exact
representation implementation-defined, with some platforms storing
bit-fields packed left-to-right, others right-to-left, and the
masked bits unspecified. This complicates serialization and
vectorized conversions.
With this change, we now explicitly store the value in the lower
4 bits, and leave the upper 4 bits unspecified. The type is
constructed in such a way that correctness is preserved
regardless of the upper bit values.