efficiently assigning initialization slot

noir-projects/aztec-nr/aztec/src/state_vars/shared_immutable.nr

@@ -1,9 +1,8 @@
 use crate::{
-    context::{Context}, hash::pedersen_hash,
-    history::public_value_inclusion::prove_public_value_inclusion,
+    context::Context, history::public_value_inclusion::prove_public_value_inclusion,
     oracle::{storage::{storage_read, storage_write}}, state_vars::storage::Storage
 };
-use dep::protocol_types::{constants::GENERATOR_INDEX__IMMUTABLE_INITIALIZE_PLACEHOLDER, traits::{Deserialize, Serialize}};
+use dep::protocol_types::traits::{Deserialize, Serialize};
 
 struct SharedImmutable<T>{
     context: Context,
@@ -18,7 +17,9 @@ impl<T> SharedImmutable<T> {
         context: Context,
         storage_slot: Field
     ) -> Self {
-        assert(storage_slot != 0, "Storage slot 0 not allowed. Storage slots must start from 1.");
+        assert(
+            (storage_slot != 0) & (storage_slot != 1), "Storage slots 0 and 1 not allowed. Storage slots must start from 2."
+        );
         Self { context, storage_slot }
     }
 
@@ -32,16 +33,13 @@ impl<T> SharedImmutable<T> {
         //     self.context.public.unwrap_unchecked().is_deployment(), "SharedImmutable can only be initialized during contract deployment"
         // );
 
-        // We check that the struct is not yet initialized by checking if the placeholder slot is 0
-        let placeholder_storage_slot = pedersen_hash(
-            [self.storage_slot],
-            GENERATOR_INDEX__IMMUTABLE_INITIALIZE_PLACEHOLDER
-        );
-        let fields_read: [Field; 1] = storage_read(placeholder_storage_slot);
+        // We check that the struct is not yet initialized by checking if the initialization slot is 0
+        let initialization_slot = self.storage_slot - 1;
+        let fields_read: [Field; 1] = storage_read(initialization_slot);
         assert(fields_read[0] == 0, "SharedImmutable already initialized");
 
-        // We populate the placeholder slot with a non-zero value to indicate that the struct is initialized
-        storage_write(placeholder_storage_slot, [0xdead]);
+        // We populate the initialization slot with a non-zero value to indicate that the struct is initialized
+        storage_write(initialization_slot, [0xdead]);
 
         let fields_write = T::serialize(value);
         storage_write(self.storage_slot, fields_write);

noir-projects/noir-protocol-circuits/src/crates/types/src/constants.nr

@@ -230,4 +230,3 @@ global GENERATOR_INDEX__VK = 41;
 global GENERATOR_INDEX__PRIVATE_CIRCUIT_PUBLIC_INPUTS = 42;
 global GENERATOR_INDEX__PUBLIC_CIRCUIT_PUBLIC_INPUTS = 43;
 global GENERATOR_INDEX__FUNCTION_ARGS = 44;
-global GENERATOR_INDEX__IMMUTABLE_INITIALIZE_PLACEHOLDER = 45;

noir/aztec_macros/src/lib.rs

@@ -932,7 +932,8 @@ fn assign_storage_slots(
                 )),
             }?;
 
-            let mut storage_slot: u64 = 1;
+            // We start from 2 because 0 storage slot is buggy and 1 is reserved for the initialization slot
+            let mut storage_slot: u64 = 2;
             for (index, (_, expr_id)) in storage_constructor_expression.fields.iter().enumerate() {
                 let fields = r#struct.borrow().get_fields(&[]);
                 let (_, field_type) = fields.get(index).unwrap();
@@ -979,7 +980,9 @@ fn assign_storage_slots(
                     ));
                 });
 
-                storage_slot += type_serialized_len;
+                // We add 1 on the next line because some of the types use value in initialization storage slot
+                // (set as "type storage slot - 1") to determine whether the value in the type was already initialized.
+                storage_slot += type_serialized_len + 1;
             }
         }
     }

yarn-project/circuits.js/src/constants.gen.ts

@@ -144,5 +144,4 @@ export enum GeneratorIndex {
   PRIVATE_CIRCUIT_PUBLIC_INPUTS = 42,
   PUBLIC_CIRCUIT_PUBLIC_INPUTS = 43,
   FUNCTION_ARGS = 44,
-  IMMUTABLE_INITIALIZE_PLACEHOLDER = 45,
 }