Multi-thread in wasm is extremly poor performance and broken status-% w ResourceLoader

[Nicklas-Holmgren]

Tested versions

• Reproducible in: 4.6.dev-4
  Used version is found here: https://godotengine.org/article/dev-snapshot-godot-4-6-dev-4/

System information

Windows 11 - Godot v4.6.dev4 - Vulkan (Forward+) - dedicated NVIDIA GeForce RTX 3090

Issue description

When ticking Thread checkbox in web export:

1st of all. progress bar is not working. ResourceLoader.load_threaded_get_status(path: String, progress: Array = []) function never returns any progress amount.

2nd. Game runs insanely poorly compared to when running same project without ticking the checkbox.

(Tested browser FireFox)

It is basically just better to export the game in non-threaded.

Steps to reproduce

Create some 3d game project.

1. Make some thread.
2. Load resource via thread
3. Report status and set a ProgressBar value
4. Status will remain 0 as value never changes.

Game will have insanely poor performance unless you remove the THREAD tick-box.

Minimal reproduction project (MRP)

I will upload a small project later today... But until then, maybe the C# has the same issue? #34506

[AThousandShips]

For the loaded percentage with FireFox see here:

• ResourceLoader.load_threaded_get_status progress stuck at 0 for Firefox when Thread Support On #101325

[Nicklas-Holmgren]

I can confirm loading % also is broken in BRAVE browser.