--enable-threads does not enable shared memory support

[RReverser]

I'm using Wasmtime 0.16.0.

I've noticed that, even with, --enable-threads, Wasmtime fails to parse modules defining shared memories, e.g.: https://github.com/GoogleChromeLabs/wasm-feature-detect/blob/master/src/detectors/threads/module.wat

(module
  (memory 1 1 shared)
  (func
    i32.const 0
    i32.atomic.load
    drop
  )
)

results in:

Caused by:
    0: failed directive on C:\Users\rreverser\Projects\wasm-feature-detect\src\detectors\threads\module.wat:5:1
    1: WebAssembly failed to compile
    2: WebAssembly translation error
    3: Unsupported feature: shared memories

While I know this feature is experimental and currently not very useful in Wasmtime, it seems unexpected because the comment for enable_threads suggests this should work at this flag enables shared memory and atomics:

wasmtime/crates/api/src/runtime.rs

Lines 145 to 147 in c284ffe

	/// This feature gates items such as shared memories and atomic
	/// instructions. Note that enabling the threads feature will
	/// also enable the bulk memory feature.

[bjorn3]

Atomics are not implemented by Cranelift at all.

[programmerjake]

Atomics are not implemented by Cranelift at all.

they've since been implemented. #1059 (comment)

[alexcrichton]

I'm going to close this in favor of #888 since it's otherwise a duplicate of that in that we're just missing big pieces of the threads proposal right now

[abrown]

Just FYI: I'm working on this at the moment.