feat: implement build_note_tag_for_local_account in masm

CHANGELOG.md

@@ -8,6 +8,7 @@
 - [BREAKING] Allowed account components to share identical account code procedures ([#2164](https://github.com/0xMiden/miden-base/pull/2164)).
 - Add `From<&ExecutedTransaction> for TransactionHeader` implementation ([#2178](https://github.com/0xMiden/miden-base/pull/2178)).
 - Add `AccountId::parse()` helper function to parse both hex and bech32 formats ([#2223](https://github.com/0xMiden/miden-base/pull/2223)).
+- Added `note::build_note_tag_for_local_account` procedure ([#2235](https://github.com/0xMiden/miden-base/pull/2235)).
 
 ### Changes
 

crates/miden-protocol/asm/protocol/note.masm

@@ -252,3 +252,62 @@ pub proc build_note_tag_for_network_account
     drop
     # => [network_account_tag]
 end
+
+#! Constructs a LocalAny note tag from the given account_id.
+#!
+#! This procedure implements the same logic as the Rust NoteTag::from_local_account_id()
+#! but assumes tag_len to be 14 bits.
+#!
+#! The tag is constructed as follows:
+#! - The two most significant bits are set to `0b11` to indicate a LOCAL_ANY tag.
+#! - The next 14 bits are set to the most significant bits of the account ID prefix.
+#! - The remaining bits are set to zero.
+#!
+#! Inputs:  [account_id_prefix, account_id_suffix]
+#! Outputs: [local_account_tag]
+#!
+#! Invocation: exec
+pub proc build_note_tag_for_local_account
+    # => [account_id_prefix, account_id_suffix]
+
+    # Drop the suffix as we only need the prefix
+    swap drop
+    # => [account_id_prefix]
+
+    # Convert prefix to u64 by splitting into high and low parts
+    u32split
+    # => [prefix_hi, prefix_lo]
+
+    # Shift the high bits of the account ID such that they are laid out as:
+    # [34 zero bits | remaining high bits (30 bits)]
+    push.2
+    # => [2, prefix_hi, prefix_lo]
+
+    exec.u64::shr
+    # => [shifted_hi, shifted_lo]
+
+    # This is equivalent to the following layout, interpreted as a u32:
+    # [2 zero bits | remaining high bits (30 bits)]
+    swap drop
+    # => [high_bits]
+
+    # Select the top 14 bits of the account ID, i.e.:
+    # [2 zero bits | remaining high bits (14 bits) | (30 - 14) zero bits]
+    # Create mask: u32::MAX << (32 - 2 - 14) = u32::MAX << 16
+    push.4294967295
+    push.16
+    # => [16, u32::MAX, high_bits]
+
+    u32shl
+    # => [mask, high_bits]
+
+    u32and
+    # => [masked_high_bits]
+
+    # Set the local execution tag in the two most significant bits
+    push.3221225472  # 0xc0000000 = LOCAL_ANY
+    # => [LOCAL_ANY, masked_high_bits]
+
+    u32or
+    # => [local_account_tag]
+end

crates/miden-testing/src/kernel_tests/tx/test_note.rs

@@ -24,6 +24,7 @@ use miden_protocol::note::{
 };
 use miden_protocol::testing::account_id::{
     ACCOUNT_ID_NETWORK_FUNGIBLE_FAUCET,
+    ACCOUNT_ID_PRIVATE_SENDER,
     ACCOUNT_ID_REGULAR_PRIVATE_ACCOUNT_UPDATABLE_CODE,
     ACCOUNT_ID_SENDER,
 };
@@ -594,3 +595,39 @@ async fn test_build_note_tag_for_network_account() -> anyhow::Result<()> {
 
     Ok(())
 }
+
+#[tokio::test]
+async fn test_build_note_tag_for_local_account() -> anyhow::Result<()> {
+    let tx_context = TransactionContextBuilder::with_existing_mock_account().build()?;
+
+    let account_id = AccountId::try_from(ACCOUNT_ID_PRIVATE_SENDER)?;
+    let expected_tag = NoteTag::from_account_id(account_id).as_u32();
+
+    let prefix: u64 = account_id.prefix().into();
+    let suffix: u64 = account_id.suffix().into();
+
+    let code = format!(
+        "
+        use miden::core::sys
+        use miden::protocol::note
+
+        begin
+            push.{suffix}.{prefix}
+
+            exec.note::build_note_tag_for_local_account
+            # => [local_account_tag]
+
+            exec.sys::truncate_stack
+        end
+        ",
+        suffix = suffix,
+        prefix = prefix,
+    );
+
+    let exec_output = tx_context.execute_code(&code).await?;
+    let actual_tag = exec_output.stack[0].as_int();
+
+    assert_eq!(expected_tag, actual_tag as u32,);
+
+    Ok(())
+}