Unify intrinsics body handling in StableMIR

compiler/rustc_smir/src/rustc_smir/context.rs

@@ -63,9 +63,10 @@ impl<'tcx> Context for TablesWrapper<'tcx> {
     }
 
     fn has_body(&self, def: DefId) -> bool {
-        let tables = self.0.borrow();
-        let def_id = tables[def];
-        tables.tcx.is_mir_available(def_id)
+        let mut tables = self.0.borrow_mut();
+        let tcx = tables.tcx;
+        let def_id = def.internal(&mut *tables, tcx);
+        tables.item_has_body(def_id)
     }
 
     fn foreign_modules(&self, crate_num: CrateNum) -> Vec<stable_mir::ty::ForeignModuleDef> {
@@ -322,13 +323,6 @@ impl<'tcx> Context for TablesWrapper<'tcx> {
         tcx.intrinsic(def_id).unwrap().name.to_string()
     }
 
-    fn intrinsic_must_be_overridden(&self, def: IntrinsicDef) -> bool {
-        let mut tables = self.0.borrow_mut();
-        let tcx = tables.tcx;
-        let def_id = def.0.internal(&mut *tables, tcx);
-        tcx.intrinsic_raw(def_id).unwrap().must_be_overridden
-    }
-
     fn closure_sig(&self, args: &GenericArgs) -> PolyFnSig {
         let mut tables = self.0.borrow_mut();
         let tcx = tables.tcx;
@@ -515,7 +509,7 @@ impl<'tcx> Context for TablesWrapper<'tcx> {
         let mut tables = self.0.borrow_mut();
         let instance = tables.instances[def];
         tables
-            .has_body(instance)
+            .instance_has_body(instance)
             .then(|| BodyBuilder::new(tables.tcx, instance).build(&mut *tables))
     }
 

compiler/rustc_smir/src/rustc_smir/mod.rs

@@ -51,16 +51,33 @@ impl<'tcx> Tables<'tcx> {
         self.mir_consts.create_or_fetch(constant)
     }
 
-    pub(crate) fn has_body(&self, instance: Instance<'tcx>) -> bool {
+    /// Return whether the instance as a body available.
+    ///
+    /// Items and intrinsics may have a body available from its definition.
+    /// Shims body may be generated depending on their type.
+    pub(crate) fn instance_has_body(&self, instance: Instance<'tcx>) -> bool {
         let def_id = instance.def_id();
-        self.tcx.is_mir_available(def_id)
+        self.item_has_body(def_id)
             || !matches!(
                 instance.def,
                 ty::InstanceDef::Virtual(..)
                     | ty::InstanceDef::Intrinsic(..)
                     | ty::InstanceDef::Item(..)
             )
     }
+
+    /// Return whether the item has a body defined by the user.
+    ///
+    /// Note that intrinsics may have a placeholder body that shouldn't be used in practice.
+    /// In StableMIR, we handle this case as if the body is not available.
+    pub(crate) fn item_has_body(&self, def_id: DefId) -> bool {
+        let must_override = if let Some(intrinsic) = self.tcx.intrinsic(def_id) {
+            intrinsic.must_be_overridden
+        } else {
+            false
+        };
+        !must_override && self.tcx.is_mir_available(def_id)
+    }
 }
 
 /// Build a stable mir crate from a given crate number.

compiler/stable_mir/src/compiler_interface.rs

@@ -94,10 +94,6 @@ pub trait Context {
     /// Retrieve the plain function name of an intrinsic.
     fn intrinsic_name(&self, def: IntrinsicDef) -> Symbol;
 
-    /// Returns whether the intrinsic has no meaningful body and all backends
-    /// need to shim all calls to it.
-    fn intrinsic_must_be_overridden(&self, def: IntrinsicDef) -> bool;
-
     /// Retrieve the closure signature for the given generic arguments.
     fn closure_sig(&self, args: &GenericArgs) -> PolyFnSig;
 

compiler/stable_mir/src/ty.rs

@@ -658,6 +658,11 @@ impl FnDef {
         with(|ctx| ctx.has_body(self.0).then(|| ctx.mir_body(self.0)))
     }
 
+    // Check if the function body is available.
+    pub fn has_body(&self) -> bool {
+        with(|ctx| ctx.has_body(self.0))
+    }
+
     /// Get the information of the intrinsic if this function is a definition of one.
     pub fn as_intrinsic(&self) -> Option<IntrinsicDef> {
         with(|cx| cx.intrinsic(self.def_id()))
@@ -684,7 +689,7 @@ impl IntrinsicDef {
     /// Returns whether the intrinsic has no meaningful body and all backends
     /// need to shim all calls to it.
     pub fn must_be_overridden(&self) -> bool {
-        with(|cx| cx.intrinsic_must_be_overridden(*self))
+        with(|cx| !cx.has_body(self.0))
     }
 }
 

tests/ui-fulldeps/stable-mir/check_intrinsics.rs

@@ -55,16 +55,19 @@ fn test_intrinsics() -> ControlFlow<()> {
 ///
 /// If by any chance this test breaks because you changed how an intrinsic is implemented, please
 /// update the test to invoke a different intrinsic.
+///
+/// In StableMIR, we only expose intrinsic body if they are not marked with
+/// `rustc_intrinsic_must_be_overridden`.
 fn check_instance(instance: &Instance) {
     assert_eq!(instance.kind, InstanceKind::Intrinsic);
     let name = instance.intrinsic_name().unwrap();
     if instance.has_body() {
         let Some(body) = instance.body() else { unreachable!("Expected a body") };
         assert!(!body.blocks.is_empty());
-        assert_matches!(name.as_str(), "likely" | "vtable_size");
+        assert_eq!(&name, "likely");
     } else {
         assert!(instance.body().is_none());
-        assert_eq!(&name, "size_of_val");
+        assert_matches!(name.as_str(), "size_of_val" | "vtable_size");
     }
 }
 
@@ -75,11 +78,13 @@ fn check_def(fn_def: FnDef) {
 
     let name = intrinsic.fn_name();
     match name.as_str() {
-        "likely" | "size_of_val" => {
+        "likely" => {
             assert!(!intrinsic.must_be_overridden());
+            assert!(fn_def.has_body());
         }
-        "vtable_size" => {
+        "vtable_size" | "size_of_val" => {
             assert!(intrinsic.must_be_overridden());
+            assert!(!fn_def.has_body());
         }
         _ => unreachable!("Unexpected intrinsic: {}", name),
     }
@@ -96,9 +101,9 @@ impl<'a> MirVisitor for CallsVisitor<'a> {
             TerminatorKind::Call { func, .. } => {
                 let TyKind::RigidTy(RigidTy::FnDef(def, args)) =
                     func.ty(self.locals).unwrap().kind()
-                else {
-                    return;
-                };
+                    else {
+                        return;
+                    };
                 self.calls.push((def, args.clone()));
             }
             _ => {}