Add new prevector benchmarks.

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

src/Makefile.bench.include

@@ -27,7 +27,7 @@ bench_bench_bitcoin_SOURCES = \
   bench/lockedpool.cpp \
   bench/perf.cpp \
   bench/perf.h \
-  bench/prevector_destructor.cpp
+  bench/prevector.cpp
 
 nodist_bench_bench_bitcoin_SOURCES = $(GENERATED_BENCH_FILES)
 

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 <compat.h>
+#include <prevector.h>
+
+#include <bench/bench.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, nontrivops, trivops)                       \
+    static void Prevector ## name ## Nontrivial(benchmark::State& state) { \
+        PrevectorResize<nontrivial_t>(state);                           \
+    }                                                                   \
+    BENCHMARK(Prevector ## name ## Nontrivial, nontrivops);             \
+    static void Prevector ## name ## Trivial(benchmark::State& state) { \
+        PrevectorResize<trivial_t>(state);                              \
+    }                                                                   \
+    BENCHMARK(Prevector ## name ## Trivial, trivops);
+
+PREVECTOR_TEST(Clear, 28300, 88600)
+PREVECTOR_TEST(Destructor, 28800, 88900)
+PREVECTOR_TEST(Resize, 28900, 90300)

src/bench/prevector_destructor.cpp

@@ -1,36 +0,0 @@
-// 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 <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, 5700);
-BENCHMARK(PrevectorClear, 5600);

src/compat.h

@@ -10,6 +10,16 @@
 #include <config/bitcoin-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