This commit restructures some of the internals of `wasm-gc` now that
I've actually got a better grasp on the wasm format and what all the
ownership edges look like. This shouldn't actually result in any
user-facing changes, but should make us be a bit more compatible with
operations in the future.
Memories/tables/elements/segments are no longer considered automatic
roots but rather need to be rooted by something else to prevent a gc.
For example an element section is gc'd along with a table if the table
is never referenced, along with data segments as well if the memory
isn't referenced.
Additionally all index sets now don't contained offseted indices, but
rather everything is always stored relative to the "index space" to
ensure consistency.
This should make it a bit easier to add future items to gc!
While technically correct the current implementation sort of made it
only roundaboutedly so. Tweak the logic a bit and the associated comment
to ensure that stack values are never dropped and the global constants
are all skipped.
Previously whenever a future readiness notification came in we would
immediately start polling a future. This ends up having two downsides,
however:
* First, the stack depth may run a risk of getting blown. There's no
recursion limit to defer execution to later, which means that if
futures are always ready we'll keep making the stack deeper.
* Second, and more worrisome in the near term, apparently future
adapaters in the `futures` crate (namely the unsync oneshot channel)
doesn't actually work if you immediately poll on readiness. This may
or may not be a bug in the `futures` crate but it's good to fix it
here anyway.
As a result whenever a future is ready to get polled again we defer its
polling to the next turn of the event loop. This should ensure that the
current call stack is always drained and we're effectively enqueueing
the future to be polled in the near future.
... and add a parallel raytracing demo!
This commit adds enough support to `wasm-bindgen` to produce a workable
wasm binary *today* with the experimental WebAssembly threads support
implemented in Firefox Nightly. I've tried to comment what's going on in
the commits and such, but at a high level the changes made here are:
* A new transformation, living in a new `wasm-bindgen-threads-xform`
crate, prepares a wasm module for parallel execution. This performs a
number of mundane tasks which I hope to detail in a blog post later on.
* The `--no-modules` output is enhanced with more support for when
shared memory is enabled, allowing passing in the module/memory to
initialize the wasm instance on multiple threads (sharing both module
and memory).
* The `wasm-bindgen` crate now offers the ability, in `--no-modules`
mode, to get a handle on the `WebAssembly.Module` instance.
* The example itself requires Xargo to recompile the standard library
with atomics and an experimental feature enabled. Afterwards it
experimentally also enables threading support in wasm-bindgen.
I've also added hopefully enough CI support to compile this example in a
builder so we can upload it and poke around live online. I hope to
detail more about the technical details here in a blog post soon as
well!
This shaves a little over 2MB off the download locally for Linux,
removing debuginfo (which no one's probably gonna use anyway) as well as
switching from jemalloc to the system allocator.
I've noticed this in a few cases where it's sometimes easy to have a
`WebAssembly.Module` on-hand for the `--no-modules` mode where you don't
want to necessarily `fetch`. This commit changes the exported
initialization function in `--no-modules` mode to support both!
This commit migrates away from using Serde for the custom section in
wasm executables. This is a refactoring of a purely-internal data
structure to `wasm-bindgen` and should have no visible functional change
on users.
The motivation for this commit is two fold:
* First, the compile times using `serde_json` and `serde_derive` for the
syntax extension isn't the most fun.
* Second, eventually we're going to want to stablize the layout of the
custom section, and it's highly unlikely to be json!
Primarily, though, the intention of this commit is to improve the
cold-cache compile time of `wasm-bindgen` by ensuring that for new users
this project builds as quickly as possible. By removing some heavyweight
dependencies from the procedural macro, `serde`, `serde_derive`, and
`serde_json`, we're able to get a pretty nice build time improvement for
the `wasm-bindgen` crate itself:
| | single-core build | parallel build |
|-------------|-------------------|----------------|
| master | 36.5s | 17.3s |
| this commit | 20.5s | 11.8s |
These are't really end-all-be-all wins but they're much better
especially on the spectrum of weaker CPUs (in theory modeled by the
single-core case showing we have 42% less CPU work in theory).
This commit fixes instantiation of the wasm module even if some of the
improted APIs don't exist. This extends the functionality initially
added in #409 to attempt to gracefully allow importing values from the
environment which don't actually exist in all contexts. In addition to
nonexistent methods being handled now entire nonexistent types are now
also handled.
I suspect that eventually we'll add a CLI flag to `wasm-bindgen` to say
"I assert everything exists, don't check it" to trim out the extra JS
glue generated here. In the meantime though this'll pave the way for a
wasm-bindgen shim to be instantiated in both a web worker and the main
thread, while using DOM-like APIs only on the main thread.
When we add threads it's not actually valid to have a global cache as
the index is only valid on one thread! Instead let's use a per-thread
cache using `thread_local!` which compiles to basically the same code as
before for single-threaded wasm.
This commit adds support for the `slice` function on all `TypedArray`
instances. The `slice` function is similar to `subarray` except that it
actually copies the data, whereas `subarray` just returns a different
view into data.
The `JsValue` type wraps a slab/heap of js objects which is managed by
the wasm-bindgen shim, and everything here is not actually able to cross
any thread boundaries. When wasm actually has threads, for example, each
thread will have to have its own slab of objects generated by
wasm-bindgen, and indices in one slab aren't valid in any other slabs.
This is technically a breaking change because `JsValue` was previously
`Send` and `Sync`, but I'm hoping that in practice this isn't actually a
breaking change because nothing in wasm can be using threads which in
theory shouldn't activate the `Send` and/or `Sync` bounds.
The bindings generation for a class would accidentally omit the `__wrap`
function if it was only discovered very late in the process that
`__wrap` was needed, after we'd already passed the point where we needed
to have decided that.
This commit moves struct field generation of bindings much earlier in
the binding generation process which should ensure everything is all
hooked up by the time we generate the classes themselves.
Closes#949
