Simple google3-compatible benchmarking.

Based on our open-source RE2 benchmarking code.

Includes benchmarks for a handful of <string.h> functions.

Change-Id: I30eb70d25dbf4ad5f2ca44976a8ce3b1ff7dad01
diff --git a/tests/string_benchmark.cpp b/tests/string_benchmark.cpp
new file mode 100644
index 0000000..cbb9771
--- /dev/null
+++ b/tests/string_benchmark.cpp
@@ -0,0 +1,96 @@
+/*
+ * Copyright (C) 2012 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "benchmark.h"
+
+#include <string.h>
+
+#define KB 1024
+#define MB 1024*KB
+
+#define AT_COMMON_SIZES \
+    Arg(8)->Arg(64)->Arg(512)->Arg(1*KB)->Arg(8*KB)->Arg(16*KB)->Arg(32*KB)->Arg(64*KB)
+
+// TODO: test unaligned operation too? (currently everything will be 8-byte aligned by malloc.)
+
+static void BM_memcmp(int iters, int nbytes) {
+  StopBenchmarkTiming();
+  char* src = new char[nbytes]; char* dst = new char[nbytes];
+  memset(src, 'x', nbytes);
+  memset(dst, 'x', nbytes);
+  StartBenchmarkTiming();
+
+  volatile int c __attribute__((unused)) = 0;
+  for (int i = 0; i < iters; i++) {
+    c += memcmp(dst, src, nbytes);
+  }
+
+  StopBenchmarkTiming();
+  SetBenchmarkBytesProcessed(int64_t(iters) * int64_t(nbytes));
+  delete[] src;
+  delete[] dst;
+}
+BENCHMARK(BM_memcmp)->AT_COMMON_SIZES;
+
+static void BM_memcpy(int iters, int nbytes) {
+  StopBenchmarkTiming();
+  char* src = new char[nbytes]; char* dst = new char[nbytes];
+  memset(src, 'x', nbytes);
+  StartBenchmarkTiming();
+
+  for (int i = 0; i < iters; i++) {
+    memcpy(dst, src, nbytes);
+  }
+
+  StopBenchmarkTiming();
+  SetBenchmarkBytesProcessed(int64_t(iters) * int64_t(nbytes));
+  delete[] src;
+  delete[] dst;
+}
+BENCHMARK(BM_memcpy)->AT_COMMON_SIZES;
+
+static void BM_memset(int iters, int nbytes) {
+  StopBenchmarkTiming();
+  char* dst = new char[nbytes];
+  StartBenchmarkTiming();
+
+  for (int i = 0; i < iters; i++) {
+    memset(dst, 0, nbytes);
+  }
+
+  StopBenchmarkTiming();
+  SetBenchmarkBytesProcessed(int64_t(iters) * int64_t(nbytes));
+  delete[] dst;
+}
+BENCHMARK(BM_memset)->AT_COMMON_SIZES;
+
+static void BM_strlen(int iters, int nbytes) {
+  StopBenchmarkTiming();
+  char* s = new char[nbytes];
+  memset(s, 'x', nbytes);
+  s[nbytes - 1] = 0;
+  StartBenchmarkTiming();
+
+  volatile int c __attribute__((unused)) = 0;
+  for (int i = 0; i < iters; i++) {
+    c += strlen(s);
+  }
+
+  StopBenchmarkTiming();
+  SetBenchmarkBytesProcessed(int64_t(iters) * int64_t(nbytes));
+  delete[] s;
+}
+BENCHMARK(BM_strlen)->AT_COMMON_SIZES;