Explain purpose for prefetches in getFirstChild

ConflictSet.cpp

@@ -1406,10 +1406,12 @@ TaggedNodePointer getChildGeq(Node *self, int child) {
 
 TaggedNodePointer getFirstChild(Node0 *) { return nullptr; }
 TaggedNodePointer getFirstChild(Node3 *self) {
+  // Improves scan performance
   __builtin_prefetch(self->children[1]);
   return self->children[0];
 }
 TaggedNodePointer getFirstChild(Node16 *self) {
+  // Improves scan performance
   __builtin_prefetch(self->children[1]);
   return self->children[0];
 }