diff --git a/cranelift/isle/TODO b/cranelift/isle/TODO
index 087256a281..dfd7fce33b 100644
--- a/cranelift/isle/TODO
+++ b/cranelift/isle/TODO
@@ -18,3 +18,5 @@
 
 - Ideas from discussion with fitzgen
   - Turn arg-polarity and exprs on extractors into purer "InstFormat"
+  - Emit two contexts: an immutable context for inputs and a mutable context for
+    outputs