diff --git a/src/field/extension_field/target.rs b/src/field/extension_field/target.rs
index 1691fba2..9d078e15 100644
--- a/src/field/extension_field/target.rs
+++ b/src/field/extension_field/target.rs
@@ -151,6 +151,7 @@ impl<F: Extendable<D>, const D: usize> CircuitBuilder<F, D> {
         sum
     }
 
+    /// TODO: Change this to using an `arithmetic_extension` function once `MulExtensionGate` supports addend.
     pub fn sub_extension(
         &mut self,
         mut a: ExtensionTarget<D>,
@@ -231,6 +232,7 @@ impl<F: Extendable<D>, const D: usize> CircuitBuilder<F, D> {
 
     /// Like `mul_add`, but for `ExtensionTarget`s. Note that, unlike `mul_add`, this has no
     /// performance benefit over separate muls and adds.
+    /// TODO: Change this to using an `arithmetic_extension` function once `MulExtensionGate` supports addend.
     pub fn mul_add_extension(
         &mut self,
         a: ExtensionTarget<D>,
@@ -243,6 +245,7 @@ impl<F: Extendable<D>, const D: usize> CircuitBuilder<F, D> {
 
     /// Like `mul_sub`, but for `ExtensionTarget`s. Note that, unlike `mul_sub`, this has no
     /// performance benefit over separate muls and subs.
+    /// TODO: Change this to using an `arithmetic_extension` function once `MulExtensionGate` supports addend.
     pub fn scalar_mul_sub_extension(
         &mut self,
         a: Target,
diff --git a/src/gadgets/rotate.rs b/src/gadgets/rotate.rs
index b7041510..12bf3bc0 100644
--- a/src/gadgets/rotate.rs
+++ b/src/gadgets/rotate.rs
@@ -7,6 +7,9 @@ impl<F: Extendable<D>, const D: usize> CircuitBuilder<F, D> {
     /// Selects `x` or `y` based on `b`, which is assumed to be binary.
     /// In particular, this returns `if b { x } else { y }`.
     /// Note: This does not range-check `b`.
+    // TODO: This uses 10 gates per call. If addends are added to `MulExtensionGate`, this will be
+    // reduced to 2 gates. We could also use a new degree 2 `SelectGate` for this.
+    // If `num_routed_wire` is larger than 26, we could batch two `select` in one gate.
     pub fn select(
         &mut self,
         b: Target,