What is the difference between wasm-as and wat2wasm?

[Evian-Zhang]

wasm-as is a tool in binaryen, and from README, its purpose is

wasm-as: Assembles WebAssembly in text format (currently S-Expression format) into binary format (going through Binaryen IR).

wat2wasm is a tool in wabt, and from README, its purpose is

wat2wasm: translate from WebAssembly text format to the WebAssembly binary format

In my understanding, both of tools translates text-format wat to binary-format wasm, and wasm-as will additionally experience a binaryen IR stage.

So in view of users, what is the difference between these two tools? And if I want to translates a hand-written wat file to wasm, what is the recommended tool to use? (MDN uses wabt toolchains)

[tlively]

WABT's wat2wasm translates directly to Wasm without modifying anything and supports the full standard text format. Binaryen's wasm-as does not support the full standard text format (although we are working on fixing that) and may modify instruction sequences that are not directly representable in Binaryen IR. If all you want to do is translate wat to Wasm, you're probably better off using wat2wasm as long as WABT supports all the Wasm features you're using. On the other hand, if you're developing a toolchain or optimization pipeline that uses Binaryen for other things, you might as well use wasm-as.