Ordinary instructions are encoded with the WebAssembly mnemonics as listed at: https://github.com/WebAssembly/design/blob/master/BinaryEncoding.md.
Opcodes are written directly in the order in which they are encoded,
without going through an intermediate sexp-style expression as in the
was format.
For “typed” opcodes (block, if, etc.), the type of the block is
specified in square brackets following the opcode: if[i],
if[].