[bench] Add benchmark for unserialize prevector

This patch adds 2 benchmarks to measure for performance of
the unserialization of prevector.

src/bench/prevector.cpp

@@ -4,12 +4,17 @@
 
 #include <compat.h>
 #include <prevector.h>
+#include <serialize.h>
+#include <streams.h>
 
 #include <bench/bench.h>
 
 struct nontrivial_t {
     int x;
     nontrivial_t() :x(-1) {}
+    ADD_SERIALIZE_METHODS
+    template <typename Stream, typename Operation>
+    inline void SerializationOp(Stream& s, Operation ser_action) {READWRITE(x);}
 };
 static_assert(!IS_TRIVIALLY_CONSTRUCTIBLE<nontrivial_t>::value,
               "expected nontrivial_t to not be trivially constructible");
@@ -62,6 +67,28 @@ static void PrevectorResize(benchmark::State& state)
     }
 }
 
+template <typename T>
+static void PrevectorDeserialize(benchmark::State& state)
+{
+    CDataStream s0(SER_NETWORK, 0);
+    prevector<28, T> t0;
+    t0.resize(28);
+    for (auto x = 0; x < 900; ++x) {
+        s0 << t0;
+    }
+    t0.resize(100);
+    for (auto x = 0; x < 101; ++x) {
+        s0 << t0;
+    }
+    while (state.KeepRunning()) {
+        prevector<28, T> t1;
+        for (auto x = 0; x < 1000; ++x) {
+            s0 >> t1;
+        }
+        s0.Init(SER_NETWORK, 0);
+    }
+}
+
 #define PREVECTOR_TEST(name, nontrivops, trivops)                       \
     static void Prevector ## name ## Nontrivial(benchmark::State& state) { \
         Prevector ## name<nontrivial_t>(state);                         \
@@ -75,3 +102,4 @@ static void PrevectorResize(benchmark::State& state)
 PREVECTOR_TEST(Clear, 28300, 88600)
 PREVECTOR_TEST(Destructor, 28800, 88900)
 PREVECTOR_TEST(Resize, 28900, 90300)
+PREVECTOR_TEST(Deserialize, 6800, 52000)