Ad hoc compilation strategies

[robrix]

• Depends on Compilation #158.

With #158, we will be able to compile well-typed programs to well-typed LLVM. However, the general compilation strategy may not be very efficient, e.g. for datatypes, which are encoded as functions.

Any ad hoc compilation strategy which preserves the semantics is well-formed, and some of them may be vastly more efficient.

Therefore, we should be able to select a different compilation strategy for some (sub-)programs, e.g.:

• Boolean → 1-bit integer.
• Maybe → pointer w/ 0 representing the nothing case.
• Maybe Boolean → 2-bit integer.
• List Boolean → bitfield.