bench: Benchmark GCS filter creation and matching.

src/Makefile.bench.include

@@ -22,6 +22,7 @@ bench_bench_bitcoin_SOURCES = \
   bench/rollingbloom.cpp \
   bench/crypto_hash.cpp \
   bench/ccoins_caching.cpp \
+  bench/gcs_filter.cpp \
   bench/merkle_root.cpp \
   bench/mempool_eviction.cpp \
   bench/verify_script.cpp \

src/bench/gcs_filter.cpp

@@ -0,0 +1,43 @@
+// Copyright (c) 2018 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <bench/bench.h>
+#include <blockfilter.h>
+
+static void ConstructGCSFilter(benchmark::State& state)
+{
+    GCSFilter::ElementSet elements;
+    for (int i = 0; i < 10000; ++i) {
+        GCSFilter::Element element(32);
+        element[0] = static_cast<unsigned char>(i);
+        element[1] = static_cast<unsigned char>(i >> 8);
+        elements.insert(std::move(element));
+    }
+
+    uint64_t siphash_k0 = 0;
+    while (state.KeepRunning()) {
+        GCSFilter filter(siphash_k0, 0, 20, 1 << 20, elements);
+
+        siphash_k0++;
+    }
+}
+
+static void MatchGCSFilter(benchmark::State& state)
+{
+    GCSFilter::ElementSet elements;
+    for (int i = 0; i < 10000; ++i) {
+        GCSFilter::Element element(32);
+        element[0] = static_cast<unsigned char>(i);
+        element[1] = static_cast<unsigned char>(i >> 8);
+        elements.insert(std::move(element));
+    }
+    GCSFilter filter(0, 0, 20, 1 << 20, elements);
+
+    while (state.KeepRunning()) {
+        filter.Match(GCSFilter::Element());
+    }
+}
+
+BENCHMARK(ConstructGCSFilter, 1000);
+BENCHMARK(MatchGCSFilter, 50 * 1000);