https://webassembly.github.io/spec/core/binary/instructions.html
Опкоды видны здесь: https://github.com/WebAssembly/design/blob/master/BinaryEncoding.md
Наглядно о распределении опкодов и стеке: https://medium.com/@CoinExChain/wasm-introduction-part-2-instruction-set-operand-stack-38e5171b52e6