[BUG] (firefox) CompileError: wasm validation error: at offset 10160270: unrecognized opcode: 12 0

[JasonGross]

Describe the bug

wasm_of_ocaml generates wasm that's only valid in Chrome but fails in Firefox with "unrecognized opcode: 12 0"
Here is the source code: fiat-html.tar.gz
If you unpack the tar.gz, run python -m http.server 8000 in the fiat-html directory, and then navigate to http://localhost:8000/?argv=%5B%22-h%22%5D&interactive&wasm, you'll get a page that works fine in chrome but fails in firefox (open the console) with "Uncaught (in promise) CompileError: wasm validation error: at offset 9925682: unrecognized opcode: 15 0" or similar (not sure why I get different validation errors sometimes).

The .tar.gz contains the standalone wasm_fiat_crypto.ml used to generate the wasm with -package unix -w -20 -g -package js_of_ocaml -linkpkg and then wasm_of_ocaml --source-map --no-inline.

Expected behavior
The generated code should work in both Chrome and Firefox

Versions
Firefox: 120.0 (64-bit)
ocaml-option-fp.1,ocaml-variants.4.14.1+options

$ wasm_of_ocaml --version
5.3.0+git-f517bbca-dirty
$ ocamlc --version
4.14.1

[vouillon]

Tail-calls have not been enabled by default in the stable version of Firefox 120, unfortunately.
You can set javascript.options.wasm_tail_calls to true in about:config to enable them. Or you can try with Firefox Beta.