Add new prevector benchmarks.

>>> backports bitcoin/bitcoin@f0e7aa7

This prepares for a series of two additional commits which optimize
prevector performance.

Github-Pull: PIVX-Project#2083
Rebased-From: e6741d0

src/Makefile.bench.include

@@ -13,7 +13,7 @@ bench_bench_pivx_SOURCES = \
   bench/crypto_hash.cpp \
   bench/perf.cpp \
   bench/perf.h \
-  bench/prevector_destructor.cpp
+  bench/prevector.cpp
 
 bench_bench_pivx_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) $(EVENT_CFLAGS) $(EVENT_PTHREADS_CFLAGS) -I$(builddir)/bench/
 bench_bench_pivx_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)

src/bench/prevector.cpp

@@ -0,0 +1,77 @@
+// 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/bench.h"
+
+#include "compat.h"
+#include "prevector.h"
+
+struct nontrivial_t {
+    int x;
+    nontrivial_t() :x(-1) {}
+};
+static_assert(!IS_TRIVIALLY_CONSTRUCTIBLE<nontrivial_t>::value,
+              "expected nontrivial_t to not be trivially constructible");
+
+typedef unsigned char trivial_t;
+static_assert(IS_TRIVIALLY_CONSTRUCTIBLE<trivial_t>::value,
+              "expected trivial_t to be trivially constructible");
+
+template <typename T>
+static void PrevectorDestructor(benchmark::State& state)
+{
+    while (state.KeepRunning()) {
+        for (auto x = 0; x < 1000; ++x) {
+            prevector<28, T> t0;
+            prevector<28, T> t1;
+            t0.resize(28);
+            t1.resize(29);
+        }
+    }
+}
+
+template <typename T>
+static void PrevectorClear(benchmark::State& state)
+{
+
+    while (state.KeepRunning()) {
+        for (auto x = 0; x < 1000; ++x) {
+            prevector<28, T> t0;
+            prevector<28, T> t1;
+            t0.resize(28);
+            t0.clear();
+            t1.resize(29);
+            t0.clear();
+        }
+    }
+}
+
+template <typename T>
+void PrevectorResize(benchmark::State& state)
+{
+    while (state.KeepRunning()) {
+        prevector<28, T> t0;
+        prevector<28, T> t1;
+        for (auto x = 0; x < 1000; ++x) {
+            t0.resize(28);
+            t0.resize(0);
+            t1.resize(29);
+            t1.resize(0);
+        }
+    }
+}
+
+#define PREVECTOR_TEST(name)                                               \
+    static void Prevector ## name ## Nontrivial(benchmark::State& state) { \
+        PrevectorResize<nontrivial_t>(state);                              \
+    }                                                                      \
+    BENCHMARK(Prevector ## name ## Nontrivial);                            \
+    static void Prevector ## name ## Trivial(benchmark::State& state) {    \
+        PrevectorResize<trivial_t>(state);                                 \
+    }                                                                      \
+    BENCHMARK(Prevector ## name ## Trivial);
+
+PREVECTOR_TEST(Clear)
+PREVECTOR_TEST(Destructor)
+PREVECTOR_TEST(Resize)

src/compat.h

@@ -11,6 +11,16 @@
 #include "config/pivx-config.h"
 #endif
 
+#include <type_traits>
+
+// GCC 4.8 is missing some C++11 type_traits,
+// https://www.gnu.org/software/gcc/gcc-5/changes.html
+#if defined(__GNUC__) && __GNUC__ < 5
+#define IS_TRIVIALLY_CONSTRUCTIBLE std::is_trivial
+#else
+#define IS_TRIVIALLY_CONSTRUCTIBLE std::is_trivially_constructible
+#endif
+
 #ifdef WIN32
 #ifdef _WIN32_WINNT
 #undef _WIN32_WINNT