Make is_intrinsic query return the intrinsic name

compiler/rustc_mir_transform/src/cost_checker.rs

@@ -70,7 +70,7 @@ impl<'tcx> Visitor<'tcx> for CostChecker<'_, 'tcx> {
             TerminatorKind::Call { func: Operand::Constant(ref f), unwind, .. } => {
                 let fn_ty = self.instantiate_ty(f.const_.ty());
                 self.cost += if let ty::FnDef(def_id, _) = *fn_ty.kind()
-                    && tcx.is_intrinsic(def_id)
+                    && tcx.intrinsic(def_id).is_some()
                 {
                     // Don't give intrinsics the extra penalty for calls
                     INSTR_COST