XC8 C Compiler
D.10.4 The order of allocation of bit-fields within an int (22.214.171.124)
The first bit-field defined in a structure is allocated the LSb position in the
storage unit. Subsequent bit-fields are allocated higher-order bits.
D.10.5 Whether a bit-field can straddle a storage-unit boundary (126.96.36.199)
A bit-field cannot straddle a storage unit. Any bit-field that would straddle a
storage unit will be allocated to the LSb position in a new storage unit.