diff --git a/compiler/rustc_codegen_cranelift/src/intrinsics/mod.rs b/compiler/rustc_codegen_cranelift/src/intrinsics/mod.rs
index 37a1e3dc04f33..1c4d307fc50e1 100644
--- a/compiler/rustc_codegen_cranelift/src/intrinsics/mod.rs
+++ b/compiler/rustc_codegen_cranelift/src/intrinsics/mod.rs
@@ -1138,6 +1138,7 @@ pub(crate) fn codegen_intrinsic_call<'tcx>(
         };
 
         black_box, (c a) {
+            // FIXME implement black_box semantics
             ret.write_cvalue(fx, a);
         };
     }