Implementation of effects based on the Stack Switching proposal

[vouillon]

To generate Wasm code that makes use of the Stack Switching proposal, you first need to install the development version of Binaryen (or version 124 once it is released).

Then, you need to run wasm_of_ocaml with the --enable wasi flag:

wasm_of_ocaml --enable wasi foo.byte -o foo.js

This produces some Wasm code that can be directly executed by the Wizard engine:

wizeng.x86-64-linux -ext:stack-switching -ext:legacy-eh foo.assets/code.wasm

Note that we keep the same output convention, at least for now: a JavaScript file foo.js and a directory foo.assets containing the Wasm code. The JavaScript file should be useful to run the tests with node once it supports this extension. It is used at the moment in #1831 to test the WASI runtime.

[linxuanm]

Hi! We are working on Wizard's stack switching and would like to generate benchmarks with wasm_of_ocaml. I tried to build wasm_of_ocaml but it seems that it depends on binaryen-bin-1.19 while an external installation of binaryen-1.24 is needed. I was able to get around this by manually editing path but was wondering if there are any plans for removing the outdated binaryen-bin from dependency so that building wasm_of_ocaml wouldn't incorrectly use the outdated executables from opam path, or if there's a better way to streamline the installation for CI? Thank you!

[vouillon]

Hi!

This was done in #2134. I have rebased the PR.

We originally forced a source install because prebuilt versions of binaryen 1.24+ weren't available. Now that they are, that step isn't needed anymore.

For a long time we this faked the installation of binaryen on the CI with opam install --fake binaryen-bin.