wasm-bindgen/examples/raytrace-parallel/build.sh
Alex Crichton 25b26f41e7 Implement support for WebAssembly threads
... 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!
2018-10-23 01:20:18 -07:00

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#!/bin/sh
set -ex
# Two critical steps are required here to get this working:
#
# * First, the Rust standard library needs to be compiled. The default version
# is not compatible with atomics so we need to compile a version, with xargo,
# that is compatible.
#
# * Next we need to compile everything with the `atomics` feature enabled,
# ensuring that LLVM will generate atomic instructions and such.
RUSTFLAGS='-C target-feature=+atomics' \
rustup run nightly xargo build --target wasm32-unknown-unknown --release
# Threading support is disabled by default in wasm-bindgen, so use an env var
# here to turn it on for our bindings generation. Also note that webpack isn't
# currently compatible with atomics, so we go with the --no-modules output.
WASM_BINDGEN_THREADS=1 \
cargo +nightly run --manifest-path ../../crates/cli/Cargo.toml \
--bin wasm-bindgen -- \
../../target/wasm32-unknown-unknown/release/raytrace_parallel.wasm --out-dir . \
--no-modules
python3 -m http.server