Create an account on web.autocad.com. Make your browser remember your login. If necessary, navigate into the webapp until you see a folder view with a folder "samples" but go no further.
Reopen the browser from the command line. The folder view should be displayed. In the terminal window you should see something like this:
Open the samples folder, and open a demo project, the "Drive Roller Assembly" project is suitably small. It should display after a few seconds.
Now go to about:config and enable j.o.wasm_optimizingjit and disable j.o.wasm_baselinejit. Close all tabs and quit.
Reopen the browser from the command line, etc. Observe that the line 'async compile succeeded' never appears (I waited 12 minutes at one point). If you open a process viewer or htop or somesuch, you will see that Firefox is pegging one core. If you open the samples and try to open a sample, it will never load.