* some instructions are not implemented yet
 * fix off-by-1 in Air.getMainBody
 * Compilation: use `@import("builtin")` rather than `std.builtin`
   for the values that are different for different build configurations.
 * Sema: avoid calling `addType` in between
   air_instructions.ensureUnusedCapacity and corresponding
   appendAssumeCapacity because it can possibly add an instruction.
 * Value: functions print their names