threads: add feature flags (#10206)

* threads: add feature flags

This adds both the Cargo-level and CLI-level flags for the
shared-everything-threads proposal.

* Remove Cargo-level feature flags

As recommended in a review, we can probably use the `threads` feature
flag instead for the same kind of conditional compilation.

* Remove CLI-level flags

Since we don't expect users to be interacting with
shared-everything-threads modules from the command line, hide this for
now.

* Add internal flags necessary for testing

Author: abrown

crates/fuzzing/src/generators/config.rs

@@ -131,6 +131,7 @@ impl Config {
             custom_page_sizes,
             multi_memory,
             threads,
+            shared_everything_threads,
             gc,
             function_references,
             relaxed_simd,
@@ -173,6 +174,7 @@ impl Config {
         config.tail_call_enabled = tail_call.unwrap_or(false);
         config.custom_page_sizes_enabled = custom_page_sizes.unwrap_or(false);
         config.threads_enabled = threads.unwrap_or(false);
+        config.shared_everything_threads_enabled = shared_everything_threads.unwrap_or(false);
         config.gc_enabled = gc.unwrap_or(false);
         config.reference_types_enabled = config.gc_enabled
             || self.module_config.function_references_enabled

crates/test-util/src/wasmtime_wast.rs

@@ -29,6 +29,7 @@ pub fn apply_test_config(config: &mut Config, test_config: &wast::TestConfig) {
         custom_page_sizes,
         multi_memory,
         threads,
+        shared_everything_threads,
         gc,
         function_references,
         relaxed_simd,
@@ -54,6 +55,7 @@ pub fn apply_test_config(config: &mut Config, test_config: &wast::TestConfig) {
     let custom_page_sizes = custom_page_sizes.unwrap_or(false);
     let multi_memory = multi_memory.unwrap_or(false);
     let threads = threads.unwrap_or(false);
+    let shared_everything_threads = shared_everything_threads.unwrap_or(false);
     let gc = gc.unwrap_or(false);
     let tail_call = tail_call.unwrap_or(false);
     let extended_const = extended_const.unwrap_or(false);
@@ -78,6 +80,7 @@ pub fn apply_test_config(config: &mut Config, test_config: &wast::TestConfig) {
     config
         .wasm_multi_memory(multi_memory)
         .wasm_threads(threads)
+        .wasm_shared_everything_threads(shared_everything_threads)
         .wasm_memory64(memory64)
         .wasm_function_references(function_references)
         .wasm_gc(gc)

crates/test-util/src/wast.rs

@@ -230,6 +230,7 @@ macro_rules! foreach_config_option {
             custom_page_sizes
             multi_memory
             threads
+            shared_everything_threads
             gc
             function_references
             relaxed_simd

crates/wasmtime/src/config.rs

@@ -848,6 +848,21 @@ impl Config {
         self
     }
 
+    /// Configures whether the WebAssembly [shared-everything-threads] proposal
+    /// will be enabled for compilation.
+    ///
+    /// This feature gates extended use of the `shared` attribute on items other
+    /// than memories, extra atomic instructions, and new component model
+    /// intrinsics for spawning threads. It depends on the
+    /// [`wasm_threads`][Self::wasm_threads] being enabled.
+    ///
+    /// [shared-everything-threads]:
+    ///     https://github.com/webassembly/shared-everything-threads
+    pub fn wasm_shared_everything_threads(&mut self, enable: bool) -> &mut Self {
+        self.wasm_feature(WasmFeatures::SHARED_EVERYTHING_THREADS, enable);
+        self
+    }
+
     /// Configures whether the [WebAssembly reference types proposal][proposal]
     /// will be enabled for compilation.
     ///

crates/wasmtime/src/engine/serialization.rs

@@ -192,6 +192,7 @@ struct WasmFeatures {
     simd: bool,
     tail_call: bool,
     threads: bool,
+    shared_everything_threads: bool,
     multi_memory: bool,
     exceptions: bool,
     legacy_exceptions: bool,
@@ -219,6 +220,7 @@ impl Metadata<'_> {
             component_model,
             simd,
             threads,
+            shared_everything_threads,
             tail_call,
             multi_memory,
             exceptions,
@@ -229,7 +231,6 @@ impl Metadata<'_> {
             function_references,
             gc,
             custom_page_sizes,
-            shared_everything_threads,
             cm_async,
             cm_async_builtins,
             cm_async_stackful,
@@ -253,7 +254,6 @@ impl Metadata<'_> {
         assert!(!memory_control);
         assert!(!cm_nested_names);
         assert!(!cm_values);
-        assert!(!shared_everything_threads);
 
         Metadata {
             target: engine.compiler().triple().to_string(),
@@ -267,6 +267,7 @@ impl Metadata<'_> {
                 component_model,
                 simd,
                 threads,
+                shared_everything_threads,
                 tail_call,
                 multi_memory,
                 exceptions,
@@ -481,6 +482,7 @@ impl Metadata<'_> {
             simd,
             tail_call,
             threads,
+            shared_everything_threads,
             multi_memory,
             exceptions,
             legacy_exceptions,
@@ -540,6 +542,11 @@ impl Metadata<'_> {
             other.contains(F::THREADS),
             "WebAssembly threads support",
         )?;
+        Self::check_bool(
+            shared_everything_threads,
+            other.contains(F::SHARED_EVERYTHING_THREADS),
+            "WebAssembly shared-everything-threads support",
+        )?;
         Self::check_bool(
             multi_memory,
             other.contains(F::MULTI_MEMORY),

tests/misc_testsuite/shared-everything-threads/flags.wast

@@ -0,0 +1,3 @@
+;;! shared_everything_threads = true
+
+(module)