add new rustc_const_stable_intrinsic attribute for const-stable intrinsics

compiler/rustc_middle/src/ty/intrinsic.rs

@@ -9,6 +9,8 @@ pub struct IntrinsicDef {
     pub name: Symbol,
     /// Whether the intrinsic has no meaningful body and all backends need to shim all calls to it.
     pub must_be_overridden: bool,
+    /// Whether the intrinsic can be invoked from stable const fn
+    pub const_stable: bool,
 }
 
 impl TyCtxt<'_> {

compiler/rustc_middle/src/ty/util.rs

@@ -1789,6 +1789,8 @@ pub fn intrinsic_raw(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option<ty::Intrinsi
         Some(ty::IntrinsicDef {
             name: tcx.item_name(def_id.into()),
             must_be_overridden: tcx.has_attr(def_id, sym::rustc_intrinsic_must_be_overridden),
+            const_stable: tcx.has_attr(def_id, sym::rustc_const_stable_intrinsic)
+                || tcx.lookup_const_stability(def_id).is_some_and(|s| s.is_const_stable()),
         })
     } else {
         None