Add wasi-exec-model cg option for emitting wasi reactors

compiler/rustc_session/src/config.rs

@@ -2086,6 +2086,7 @@ crate mod dep_tracking {
         SymbolManglingVersion, TrimmedDefPaths,
     };
     use crate::lint;
+    use crate::options::WasiExecModel;
     use crate::utils::NativeLibKind;
     use rustc_feature::UnstableFeatures;
     use rustc_span::edition::Edition;
@@ -2141,6 +2142,7 @@ crate mod dep_tracking {
     impl_dep_tracking_hash_via_hash!(Option<RelocModel>);
     impl_dep_tracking_hash_via_hash!(Option<CodeModel>);
     impl_dep_tracking_hash_via_hash!(Option<TlsModel>);
+    impl_dep_tracking_hash_via_hash!(Option<WasiExecModel>);
     impl_dep_tracking_hash_via_hash!(Option<PanicStrategy>);
     impl_dep_tracking_hash_via_hash!(Option<RelroLevel>);
     impl_dep_tracking_hash_via_hash!(Option<lint::Level>);

compiler/rustc_session/src/options.rs

@@ -278,6 +278,7 @@ macro_rules! options {
         pub const parse_tls_model: &str =
             "one of supported TLS models (`rustc --print tls-models`)";
         pub const parse_target_feature: &str = parse_string;
+        pub const parse_wasi_exec_model: &str = "either `command` or `reactor`";
     }
 
     #[allow(dead_code)]
@@ -708,6 +709,15 @@ macro_rules! options {
                 None => false,
             }
         }
+
+        fn parse_wasi_exec_model(slot: &mut Option<WasiExecModel>, v: Option<&str>) -> bool {
+            match v {
+                Some("command")  => *slot = Some(WasiExecModel::Command),
+                Some("reactor") => *slot = Some(WasiExecModel::Reactor),
+                _ => return false,
+            }
+            true
+        }
     }
 ) }
 
@@ -1147,9 +1157,17 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
         "in general, enable more debug printouts (default: no)"),
     verify_llvm_ir: bool = (false, parse_bool, [TRACKED],
         "verify LLVM IR (default: no)"),
+    wasi_exec_model: Option<WasiExecModel> = (None, parse_wasi_exec_model, [TRACKED],
+        "whether to build a wasi command or reactor"),
 
     // This list is in alphabetical order.
     //
     // If you add a new option, please update:
-    // - src/librustc_interface/tests.rs
+    // - compiler/rustc_interface/src/tests.rs
+}
+
+#[derive(Clone, Hash)]
+pub enum WasiExecModel {
+    Command,
+    Reactor,
 }

compiler/rustc_session/src/session.rs

@@ -796,6 +796,14 @@ impl Session {
         self.opts.debugging_opts.tls_model.unwrap_or(self.target.tls_model)
     }
 
+    pub fn is_wasi_reactor(&self) -> bool {
+        self.target.options.os == "wasi"
+            && matches!(
+                self.opts.debugging_opts.wasi_exec_model,
+                Some(config::WasiExecModel::Reactor)
+            )
+    }
+
     pub fn must_not_eliminate_frame_pointers(&self) -> bool {
         // "mcount" function relies on stack pointer.
         // See <https://sourceware.org/binutils/docs/gprof/Implementation.html>.