bench: add scrypt

Add an scrypt benchmark that hashes 80 byte inputs (size of a
block header)

src/Makefile.bench.include

@@ -23,7 +23,8 @@ bench_bench_dogecoin_SOURCES = \
   bench/base58.cpp \
   bench/lockedpool.cpp \
   bench/perf.cpp \
-  bench/perf.h
+  bench/perf.h \
+  bench/scrypt.cpp
 
 # bench_bench_dogecoin_SOURCES_DISABLED = \
 #   bench/checkblock.cpp \        # disabled because this checks a specific bitcoin block

src/bench/scrypt.cpp

@@ -0,0 +1,28 @@
+#include <iostream>
+#include <vector>
+
+#include "bench.h"
+#include "crypto/scrypt.h"
+#include "uint256.h"
+#include "utiltime.h"
+#include "utilstrencodings.h"
+
+// 80 bytes input, size of CPureBlockHeader
+static const uint64_t BUFFER_SIZE = 80;
+
+static void Scrypt(benchmark::State& state)
+{
+    uint256 output;
+    std::vector<char> in(BUFFER_SIZE, 0);
+
+#ifdef USE_SSE2
+    scrypt_detect_sse2();
+#endif // USE_SSE2
+
+    while (state.KeepRunning())
+    {
+        scrypt_1024_1_1_256(in.data(), BEGIN(output));
+    }
+}
+
+BENCHMARK(Scrypt);