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Enable threads, multi-memory, and relaxed-simd by default #7285

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Oct 18, 2023
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Enable threads, multi-memory, and relaxed-simd by default #7285

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5fa4e40
Enable threads, multi-memory, and relaxed-simd by default
alexcrichton Oct 18, 2023
835ecc6
Fix an x64-specific test
alexcrichton Oct 18, 2023
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54 changes: 20 additions & 34 deletions crates/wasmtime/src/config.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -230,10 +230,6 @@ impl Config {
ret.wasm_simd(true);
ret.wasm_backtrace_details(WasmBacktraceDetails::Environment);

ret.wasm_relaxed_simd(false);
ret.wasm_threads(false);
ret.wasm_multi_memory(false);

// This is on-by-default in `wasmparser` since it's a stage 4+ proposal
// but it's not implemented in Wasmtime yet so disable it.
ret.features.tail_call = false;
Expand Down Expand Up @@ -660,31 +656,23 @@ impl Config {
self
}

/// Configures whether the WebAssembly threads proposal will be enabled for
/// compilation.
///
/// The [WebAssembly threads proposal][threads] is not currently fully
/// standardized and is undergoing development. Additionally the support in
/// wasmtime itself is still being worked on. Support for this feature can
/// be enabled through this method for appropriate wasm modules.
/// Configures whether the WebAssembly [threads] proposal will be enabled
/// for compilation.
///
/// This feature gates items such as shared memories and atomic
/// instructions. Note that the threads feature depends on the
/// bulk memory feature, which is enabled by default.
/// instructions. Note that the threads feature depends on the bulk memory
/// feature, which is enabled by default. Additionally note that while the
/// wasm feature is called "threads" it does not actually include the
/// ability to spawn threads. Spawning threads is part of the [wasi-threads]
/// proposal which is a separately gated feature in Wasmtime.
///
/// This is `false` by default.
///
/// > **Note**: Wasmtime does not implement everything for the wasm threads
/// > spec at this time, so bugs, panics, and possibly segfaults should be
/// > expected. This should not be enabled in a production setting right
/// > now.
///
/// # Errors
/// Embeddings of Wasmtime are able to build their own custom threading
/// scheme on top of the core wasm threads proposal, however.
///
/// The validation of this feature are deferred until the engine is being built,
/// and thus may cause `Engine::new` fail if the `bulk_memory` feature is disabled.
/// This is `true` by default.
///
/// [threads]: https://github.com/webassembly/threads
/// [wasi-threads]: https://github.com/webassembly/wasi-threads
pub fn wasm_threads(&mut self, enable: bool) -> &mut Self {
self.features.threads = enable;
self
Expand Down Expand Up @@ -750,15 +738,13 @@ impl Config {
/// Configures whether the WebAssembly Relaxed SIMD proposal will be
/// enabled for compilation.
///
/// The [WebAssembly Relaxed SIMD proposal][proposal] is not, at the time of
/// this writing, at stage 4. The relaxed SIMD proposal adds new
/// instructions to WebAssembly which, for some specific inputs, are allowed
/// to produce different results on different hosts. More-or-less this
/// proposal enables exposing platform-specific semantics of SIMD
/// instructions in a controlled fashion to a WebAssembly program. From an
/// embedder's perspective this means that WebAssembly programs may execute
/// differently depending on whether the host is x86_64 or AArch64, for
/// example.
/// The relaxed SIMD proposal adds new instructions to WebAssembly which,
/// for some specific inputs, are allowed to produce different results on
/// different hosts. More-or-less this proposal enables exposing
/// platform-specific semantics of SIMD instructions in a controlled
/// fashion to a WebAssembly program. From an embedder's perspective this
/// means that WebAssembly programs may execute differently depending on
/// whether the host is x86_64 or AArch64, for example.
///
/// By default Wasmtime lowers relaxed SIMD instructions to the fastest
/// lowering for the platform it's running on. This means that, by default,
Expand All @@ -768,7 +754,7 @@ impl Config {
/// deterministic behavior across all platforms, as classified by the
/// specification, at the cost of performance.
///
/// This is `false` by default.
/// This is `true` by default.
///
/// [proposal]: https://github.com/webassembly/relaxed-simd
pub fn wasm_relaxed_simd(&mut self, enable: bool) -> &mut Self {
Expand Down Expand Up @@ -840,7 +826,7 @@ impl Config {
/// This feature gates modules having more than one linear memory
/// declaration or import.
///
/// This is `false` by default.
/// This is `true` by default.
///
/// [proposal]: https://github.com/webassembly/multi-memory
pub fn wasm_multi_memory(&mut self, enable: bool) -> &mut Self {
Expand Down
12 changes: 6 additions & 6 deletions crates/wasmtime/src/engine/serialization.rs
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Expand Up @@ -629,27 +629,27 @@ Caused by:
#[test]
fn test_feature_mismatch() -> Result<()> {
let mut config = Config::new();
config.wasm_simd(true);
config.wasm_threads(true);

let engine = Engine::new(&config)?;
let mut metadata = Metadata::new(&engine);
metadata.features.simd = false;
metadata.features.threads = false;

match metadata.check_compatible(&engine) {
Ok(_) => unreachable!(),
Err(e) => assert_eq!(e.to_string(), "Module was compiled without WebAssembly SIMD support but it is enabled for the host"),
Err(e) => assert_eq!(e.to_string(), "Module was compiled without WebAssembly threads support but it is enabled for the host"),
}

let mut config = Config::new();
config.wasm_simd(false);
config.wasm_threads(false);

let engine = Engine::new(&config)?;
let mut metadata = Metadata::new(&engine);
metadata.features.simd = true;
metadata.features.threads = true;

match metadata.check_compatible(&engine) {
Ok(_) => unreachable!(),
Err(e) => assert_eq!(e.to_string(), "Module was compiled with WebAssembly SIMD support but it is not enabled for the host"),
Err(e) => assert_eq!(e.to_string(), "Module was compiled with WebAssembly threads support but it is not enabled for the host"),
}

Ok(())
Expand Down
4 changes: 2 additions & 2 deletions tests/all/module.rs
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Expand Up @@ -43,7 +43,7 @@ fn caches_across_engines() {
// differ in wasm features enabled (which can affect
// runtime/compilation settings)
let res = Module::deserialize(
&Engine::new(Config::new().wasm_simd(false)).unwrap(),
&Engine::new(Config::new().wasm_threads(false)).unwrap(),
&bytes,
);
assert!(res.is_err());
Expand Down Expand Up @@ -182,7 +182,7 @@ fn serialize_not_overly_massive() -> Result<()> {
#[cfg_attr(any(not(target_arch = "x86_64"), miri), ignore)]
fn missing_sse_and_floats_still_works() -> Result<()> {
let mut config = Config::new();
config.wasm_simd(false);
config.wasm_simd(false).wasm_relaxed_simd(false);
unsafe {
config.cranelift_flag_set("has_sse41", "false");
}
Expand Down