Add benchmark

Internal.h

@@ -4,6 +4,7 @@
 
 #include <bit>
 #include <cassert>
+#include <compare>
 #include <cstddef>
 #include <cstdint>
 #include <cstdlib>
@@ -19,6 +20,18 @@
 
 #define DEBUG_VERBOSE 0
 
+[[nodiscard]] inline auto
+operator<=>(const std::span<const uint8_t> &lhs,
+            const std::span<const uint8_t> &rhs) noexcept {
+  int cl = std::min<int>(lhs.size(), rhs.size());
+  if (cl > 0) {
+    if (auto c = memcmp(lhs.data(), rhs.data(), cl) <=> 0; c != 0) {
+      return c;
+    }
+  }
+  return lhs.size() <=> rhs.size();
+}
+
 // This header contains code that we want to reuse outside of ConflictSet.cpp or
 // want to exclude from coverage since it's only testing related.
 
@@ -181,9 +194,9 @@ template <class T> using Vector = std::vector<T, ArenaAlloc<T>>;
 template <class T> auto vector(Arena &arena) {
   return Vector<T>(ArenaAlloc<T>(&arena));
 }
-template <class T> using Set = std::set<T, std::less<T>, ArenaAlloc<T>>;
-template <class T> auto set(Arena &arena) {
-  return Set<T>(ArenaAlloc<T>(&arena));
+template <class T, class C> using Set = std::set<T, C, ArenaAlloc<T>>;
+template <class T, class C = std::less<T>> auto set(Arena &arena) {
+  return Set<T, C>(ArenaAlloc<T>(&arena));
 }
 
 template <class T> struct MyHash;