Add prevector destructor benchmark

src/Makefile.bench.include

@@ -24,7 +24,8 @@ bench_bench_bitcoin_SOURCES = \
   bench/base58.cpp \
   bench/lockedpool.cpp \
   bench/perf.cpp \
-  bench/perf.h
+  bench/perf.h \
+  bench/prevector_destructor.cpp
 
 nodist_bench_bench_bitcoin_SOURCES = $(GENERATED_TEST_FILES)
 

src/bench/prevector_destructor.cpp

@@ -0,0 +1,36 @@
+// Copyright (c) 2015-2017 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.h"
+#include "prevector.h"
+
+static void PrevectorDestructor(benchmark::State& state)
+{
+    while (state.KeepRunning()) {
+        for (auto x = 0; x < 1000; ++x) {
+            prevector<28, unsigned char> t0;
+            prevector<28, unsigned char> t1;
+            t0.resize(28);
+            t1.resize(29);
+        }
+    }
+}
+
+static void PrevectorClear(benchmark::State& state)
+{
+
+    while (state.KeepRunning()) {
+        for (auto x = 0; x < 1000; ++x) {
+            prevector<28, unsigned char> t0;
+            prevector<28, unsigned char> t1;
+            t0.resize(28);
+            t0.clear();
+            t1.resize(29);
+            t0.clear();
+        }
+    }
+}
+
+BENCHMARK(PrevectorDestructor);
+BENCHMARK(PrevectorClear);