It doesn't actually try to undo anything, it just translates Wasm instructions 1:1 (they're in your link at lines 205-221). wasm-decompile does try to "undo" so

It doesn't actually try to undo anything, it just translates Wasm instructions 1:1 (they're in your link at lines 205-221). wasm-decompile does try to "undo" some thing, but it is generally impossible given LLVM's optimized output and how low-level Wasm is (see also article).