Which bitwise operations are used in SHA-256?
The functions used by SHA-2, called $Ch$ and $Maj$ are defined like this in the standard:

$$Ch(x, y, z)  = (x \land y) \oplus (\lnot x \land z)$$
$$Maj(x, y, z)  = (x \land y) \oplus (x \land z) \oplus (y \land z)$$

However, an equivalent way to define them replaces the XOR with OR, as the standard (pdf) states:


  Each of the algorithms include $Ch(x, y, z)$ and $Maj(x, y, z)$ functions; the exclusive-OR operation ($\oplus$) in these functions may be replaced by a bitwise OR operation ($\lor$) and produce identical results.


Of course, any functionally complete set of operators is sufficient to implement the functions, but at least some implementations (e.g. PyPy) do elect to use OR here.