To add a plain instruction with a fixed number of parameters (which is the
case of most instructions) which do not require any kind of type variables
(such as ref.as_non_null), one needs to modify the following
files:
Val/instruction-types.sch to add the type of the
instruction to the validation pass, Asm/opcodes.sch to add the opcode of the instruction, if
the opcode depends on the argument it has to be added in an ad-hoc way to
Asm/binary.scm.
The format in which all these additions have to be made is described in each file individually and the already present instructions serve as examples.
For other instructions, the files Val/validate.scm
and Asm/binary.scm will have to be modified, for validation and
assembly. To replace the need of type variables, instructions can be
validated by the adhoc-instr function of
the Val/validate.scm. There they can rely on the stack for
their validation. For instance, ref.as_non_null will be of
type (ref null ht) -> (ref ht) where ht is the
heap type corresponding to the reference type on top of the stack.
The file `Ast/node.scm` should also be modified to record new kinds of instructions such as new blocks.
Each optimisation pass should be modified to take the new instructions into
account (roughly everything in Opt/). Depending on the
instruction and the pass their could be no necessary modification.