add missing padding

barretenberg/cpp/src/barretenberg/stdlib/hash/poseidon2/poseidon2.cpp

@@ -40,5 +40,6 @@ template <typename C> field_t<C> poseidon2<C>::hash_buffer(C& builder, const std
     return hash(builder, elements);
 }
 template class poseidon2<bb::MegaCircuitBuilder>;
+template class poseidon2<bb::UltraCircuitBuilder>;
 
 } // namespace bb::stdlib

barretenberg/cpp/src/barretenberg/stdlib/hash/poseidon2/poseidon2.test.cpp

@@ -147,7 +147,7 @@ template <typename Builder> class StdlibPoseidon2 : public testing::Test {
     }
 };
 
-using CircuitTypes = testing::Types<bb::MegaCircuitBuilder>;
+using CircuitTypes = testing::Types<bb::MegaCircuitBuilder, bb::UltraCircuitBuilder>;
 
 TYPED_TEST_SUITE(StdlibPoseidon2, CircuitTypes);
 

barretenberg/cpp/src/barretenberg/stdlib_circuit_builders/ultra_circuit_builder.cpp

@@ -2819,6 +2819,9 @@ void UltraCircuitBuilder_<FF>::create_poseidon2_external_gate(const poseidon2_ex
     block.q_aux().emplace_back(0);
     block.q_poseidon2_external().emplace_back(1);
     block.q_poseidon2_internal().emplace_back(0);
+    if constexpr (HasAdditionalSelectors<Arithmetization>) {
+        block.pad_additional();
+    }
     this->check_selector_length_consistency();
     ++this->num_gates;
 }
@@ -2844,6 +2847,9 @@ void UltraCircuitBuilder_<FF>::create_poseidon2_internal_gate(const poseidon2_in
     block.q_aux().emplace_back(0);
     block.q_poseidon2_external().emplace_back(0);
     block.q_poseidon2_internal().emplace_back(1);
+    if constexpr (HasAdditionalSelectors<Arithmetization>) {
+        block.pad_additional();
+    }
     this->check_selector_length_consistency();
     ++this->num_gates;
 }