There are two main ways in which a value can be stored: "Direct", as it
will be operated on as an immediate value, and "indirect", as it is stored
in memory. Some types need a different representation here: Bools, for
example, are opaque in SPIR-V, and so these need to have a different
representation in memory. The bool operations are not easily interchangable
with integer operations, though, so they need to be OpTypeBool as
immediate value.