commit 2deecf3cb4cf607ecf115093cc855ab411b82502
author Scott Todd <scotttodd@google.com> Fri Nov 18 13:06:13 2022 -0800
committer GitHub <noreply@github.com> Fri Nov 18 13:06:13 2022 -0800
tree 61b3de2b26ad0961eb2e597ed2d5f7da2cdbb43d
parent 1b95a2f285ac8d44e44f06de322abf5b315495bd

Initial iree_loop_t implementation for web browsers. (#11204)

This is the start of an implementation of the
[`iree_loop_t`](https://github.com/iree-org/iree/blob/main/runtime/src/iree/base/loop.h)
interface (added back in https://github.com/iree-org/iree/pull/8329) for
web browsers, using `setTimeout()`, Promises, and other JavaScript APIs
for working with asynchronous operations and the browser event loop.

This only handles `IREE_LOOP_COMMAND_CALL` for now, but I'd like some
feedback on the architecture / implementation style.

Some details that were tricky to figure out:
* This uses a JavaScript library that implements a C API:
https://emscripten.org/docs/porting/connecting_cpp_and_javascript/Interacting-with-code.html#implement-a-c-api-in-javascript.
We may end up with a few of these.
* The JavaScript library uses `dynCall_iiii` to call a provided C
function pointer (I haven't found any dedicated documentation on this,
so this was pieced together from reading through Emscripten's source
code)
* A new `iree_link_js_library` CMake function was added to pass
`--js-library` to `emcc` and set up the right dependency link between
.js files and binaries (tests/applications/etc.). We can also use
`--pre-js` and `--post-js` as needed.