perf: misc changes (#5701)

crates/primitives/src/trie/hash_builder/mod.rs

@@ -203,20 +203,24 @@ impl HashBuilder {
 
         trace!(target: "trie::hash_builder", ?current, ?succeeding, "updating merkle tree");
 
-        let mut i = 0;
+        let mut i = 0usize;
+        let span = tracing::trace_span!(
+            target: "trie::hash_builder",
+            "loop",
+            i = tracing::field::Empty,
+            current = tracing::field::Empty,
+            build_extensions = tracing::field::Empty,
+        )
+        .entered();
         loop {
-            let span = tracing::span!(
-                target: "trie::hash_builder",
-                tracing::Level::TRACE,
-                "loop",
-                i,
-                ?current,
-                ?build_extensions
-            );
-            let _enter = span.enter();
+            if !span.is_disabled() {
+                span.record("i", i);
+                span.record("current", &format!("{current:?}"));
+                span.record("build_extensions", build_extensions);
+            }
 
             let preceding_exists = !self.groups.is_empty();
-            let preceding_len: usize = self.groups.len().saturating_sub(1);
+            let preceding_len = self.groups.len().saturating_sub(1);
 
             let common_prefix_len = succeeding.common_prefix_length(current.as_slice());
             let len = std::cmp::max(preceding_len, common_prefix_len);
@@ -254,7 +258,7 @@ impl HashBuilder {
             if !succeeding.is_empty() || preceding_exists {
                 len_from += 1;
             }
-            trace!(target: "trie::hash_builder", "skipping {} nibbles", len_from);
+            trace!(target: "trie::hash_builder", "skipping {len_from} nibbles");
 
             // The key without the common prefix
             let short_node_key = current.slice(len_from..);

crates/primitives/src/trie/nibbles.rs

@@ -67,7 +67,6 @@ impl Compact for StoredNibblesSubKey {
 /// The internal representation is a [`SmallVec`] that stores one nibble per byte. This means that
 /// each byte has its upper 4 bits set to zero and the lower 4 bits representing the nibble value.
 #[derive(
-    Clone,
     Default,
     PartialEq,
     Eq,
@@ -83,6 +82,19 @@ impl Compact for StoredNibblesSubKey {
 #[cfg_attr(any(test, feature = "arbitrary"), derive(arbitrary::Arbitrary))]
 pub struct Nibbles(SmallVec<[u8; 64]>);
 
+// Override `SmallVec::from` since it's not specialized for `Copy` types.
+impl Clone for Nibbles {
+    #[inline]
+    fn clone(&self) -> Self {
+        Self(SmallVec::from_slice(&self.0))
+    }
+
+    #[inline]
+    fn clone_from(&mut self, source: &Self) {
+        self.0.clone_from(&source.0);
+    }
+}
+
 impl alloy_rlp::Encodable for Nibbles {
     #[inline]
     fn length(&self) -> usize {

crates/primitives/src/trie/nodes/mod.rs

@@ -28,5 +28,9 @@ fn rlp_node(rlp: &[u8]) -> Vec<u8> {
 // TODO: this could return [u8; 33] but Vec is needed everywhere this function is used
 #[inline]
 pub fn word_rlp(word: &B256) -> Vec<u8> {
-    [&[EMPTY_STRING_CODE + B256::len_bytes() as u8][..], &word[..]].concat()
+    // Gets optimized to alloc + write directly into it: https://godbolt.org/z/rfWGG6ebq
+    let mut arr = [0; 33];
+    arr[0] = EMPTY_STRING_CODE + 32;
+    arr[1..].copy_from_slice(word.as_slice());
+    arr.to_vec()
 }