Tweak MPT value storage

evm/src/cpu/kernel/asm/mpt/hash.asm

@@ -137,6 +137,8 @@ encode_node_branch:
     // stack: rlp_pos', node_payload_ptr, encode_value, retdest
     SWAP1
     %add_const(16)
+    // stack: value_ptr_ptr, rlp_pos', encode_value, retdest
+    %mload_trie_data
     // stack: value_len_ptr, rlp_pos', encode_value, retdest
     DUP1 %mload_trie_data
     // stack: value_len, value_len_ptr, rlp_pos', encode_value, retdest
@@ -257,7 +259,10 @@ encode_node_leaf:
 encode_node_leaf_after_hex_prefix:
     // stack: rlp_pos, node_payload_ptr, encode_value, retdest
     SWAP1
-    %add_const(3) // The value starts at index 3, after num_nibbles, packed_nibbles, and value_len.
+    %add_const(2) // The value pointer starts at index 3, after num_nibbles and packed_nibbles.
+    // stack: value_ptr_ptr, rlp_pos, encode_value, retdest
+    %mload_trie_data
+    %increment // skip over length prefix
     // stack: value_ptr, rlp_pos, encode_value, retdest
     %stack (value_ptr, rlp_pos, encode_value, retdest)
         -> (encode_value, rlp_pos, value_ptr, encode_node_leaf_after_encode_value, retdest)

evm/src/cpu/kernel/asm/mpt/load.asm

@@ -76,9 +76,14 @@ load_mpt_branch:
     %get_trie_data_size
     // stack: ptr_children, retdest
     DUP1 %add_const(16)
-    // stack: ptr_leaf, ptr_children, retdest
+    // stack: ptr_value, ptr_children, retdest
     %set_trie_data_size
     // stack: ptr_children, retdest
+    // We need to append a pointer to where the value will live.
+    // %load_leaf_value will append the value just after this pointer;
+    // we add 1 to account for the pointer itself.
+    %get_trie_data_size %increment %append_to_trie_data
+    // stack: ptr_children, retdest
     %load_leaf_value
 
     // Load the 16 children.
@@ -128,6 +133,11 @@ load_mpt_leaf:
     PROVER_INPUT(mpt) // read packed_nibbles
     %append_to_trie_data
     // stack: retdest
+    // We need to append a pointer to where the value will live.
+    // %load_leaf_value will append the value just after this pointer;
+    // we add 1 to account for the pointer itself.
+    %get_trie_data_size %increment %append_to_trie_data
+    // stack: retdest
     %load_leaf_value
     // stack: retdest
     JUMP

evm/src/cpu/kernel/asm/mpt/read.asm

@@ -1,6 +1,6 @@
-// Given an address, return a pointer to the associated account data, which
-// consists of four words (nonce, balance, storage_root, code_hash), in the
-// state trie. Returns 0 if the address is not found.
+// Given an address, return a pointer to the associated (length-prefixed)
+// account data, which consists of four words (nonce, balance, storage_root,
+// code_hash), in the state trie. Returns 0 if the address is not found.
 global mpt_read_state_trie:
     // stack: addr, retdest
     // The key is the hash of the address. Since KECCAK_GENERAL takes input from
@@ -24,7 +24,7 @@ mpt_read_state_trie_after_mstore:
 // - the key, as a U256
 // - the number of nibbles in the key (should start at 64)
 //
-// This function returns a pointer to the leaf, or 0 if the key is not found.
+// This function returns a pointer to the length-prefixed leaf, or 0 if the key is not found.
 global mpt_read:
     // stack: node_ptr, num_nibbles, key, retdest
     DUP1
@@ -75,6 +75,8 @@ mpt_read_branch_end_of_key:
     %stack (node_payload_ptr, num_nibbles, key, retdest) -> (node_payload_ptr, retdest)
     // stack: node_payload_ptr, retdest
     %add_const(16) // skip over the 16 child nodes
+    // stack: value_ptr_ptr, retdest
+    %mload_trie_data
     // stack: value_len_ptr, retdest
     DUP1 %mload_trie_data
     // stack: value_len, value_len_ptr, retdest
@@ -147,7 +149,9 @@ mpt_read_leaf:
     JUMP
 mpt_read_leaf_found:
     // stack: node_payload_ptr, retdest
-    %add_const(3) // The value is located after num_nibbles, the key, and the value length.
+    %add_const(2) // The value pointer is located after num_nibbles and the key.
+    // stack: value_ptr_ptr, retdest
+    %mload_trie_data
     // stack: value_ptr, retdest
     SWAP1
     JUMP

evm/src/cpu/kernel/tests/mpt/load.rs

@@ -48,6 +48,7 @@ fn load_all_mpts() -> Result<()> {
             type_leaf,
             3.into(),     // 3 nibbles
             0xDEF.into(), // key part
+            9.into(),     // value pointer
             4.into(),     // value length
             account.nonce,
             account.balance,

evm/src/cpu/kernel/tests/mpt/read.rs

@@ -44,11 +44,12 @@ fn mpt_read() -> Result<()> {
 
     assert_eq!(interpreter.stack().len(), 1);
     let result_ptr = interpreter.stack()[0].as_usize();
-    let result = &interpreter.get_trie_data()[result_ptr..][..4];
-    assert_eq!(result[0], account.nonce);
-    assert_eq!(result[1], account.balance);
-    assert_eq!(result[2], account.storage_root.into_uint());
-    assert_eq!(result[3], account.code_hash.into_uint());
+    let result = &interpreter.get_trie_data()[result_ptr..][..5];
+    assert_eq!(result[0], 4.into());
+    assert_eq!(result[1], account.nonce);
+    assert_eq!(result[2], account.balance);
+    assert_eq!(result[3], account.storage_root.into_uint());
+    assert_eq!(result[4], account.code_hash.into_uint());
 
     Ok(())
 }