Add __cxa_atexit benchmark

The benchmark calls __cxa_atexit 100000 times, then either exits early
without calling the destructors (_Exit) or exits normally, calling them
(exit).

Test: mmma bionic/benchmarks/spawn
Change-Id: I41fe702d6ef11acb7a1dec95bf546b5dc693bd4a

benchmarks/spawn/Android.bp

@@ -68,6 +68,7 @@ cc_benchmark {
 
     // Install these binaries in the same directory as the main benchmark binary.
     data: [
+        ":bench_cxa_atexit",
         ":bench_noop",
         ":bench_noop_nostl",
         ":bench_noop_static",
@@ -75,7 +76,7 @@ cc_benchmark {
 }
 
 cc_defaults {
-    name: "noop_binary_defaults",
+    name: "bionic_spawn_benchmark_binary",
     defaults: ["bionic_spawn_benchmark_targets"],
 
     compile_multilib: "both",
@@ -87,16 +88,11 @@ cc_defaults {
             suffix: "64",
         },
     },
-}
-
-cc_binary {
-    defaults: ["noop_binary_defaults"],
-    name: "bench_noop",
-    srcs: ["noop.cpp"],
 
     // When this binary is installed to host/linux-x86/bin, its runpath is ${ORIGIN}/../lib64, which
     // is fine for finding host/linux-x86/lib64/libc++.so. When it's installed to
-    // host/linux-x86/benchmarktest64/bionic-spawn-benchmarks, the runpath needs an extra "..".
+    // host/linux-x86/benchmarktest64/bionic-spawn-benchmarks, the runpath needs an extra "..". This
+    // argument has no effect when a static executable is produced.
     target: {
         linux_glibc_x86_64: {
             ldflags: [
@@ -107,14 +103,26 @@ cc_binary {
 }
 
 cc_binary {
-    defaults: ["noop_binary_defaults"],
+    defaults: ["bionic_spawn_benchmark_binary"],
+    name: "bench_cxa_atexit",
+    srcs: ["bench_cxa_atexit.cpp"],
+}
+
+cc_binary {
+    defaults: ["bionic_spawn_benchmark_binary"],
+    name: "bench_noop",
+    srcs: ["noop.cpp"],
+}
+
+cc_binary {
+    defaults: ["bionic_spawn_benchmark_binary"],
     name: "bench_noop_nostl",
     srcs: ["noop.cpp"],
     stl: "none",
 }
 
 cc_binary {
-    defaults: ["noop_binary_defaults"],
+    defaults: ["bionic_spawn_benchmark_binary"],
     name: "bench_noop_static",
     srcs: ["noop.cpp"],
     static_executable: true,

benchmarks/spawn/bench_cxa_atexit.cpp

@@ -0,0 +1,67 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <string>
+
+extern "C" int __cxa_atexit(void (*func)(void*), void* arg, void* dso);
+
+extern void* __dso_handle;
+
+static void dtor_func(void*) {}
+
+// Prevent the compiler from optimizing out the __cxa_atexit call.
+void (*volatile g_pdtor_func)(void*) = dtor_func;
+
+int main(int argc, char* argv[]) {
+  auto usage = [&argv]() {
+    fprintf(stderr, "usage: %s COUNT MODE\n", argv[0]);
+    fprintf(stderr, "MODE is one of '_Exit' or 'exit'.\n");
+    exit(1);
+  };
+
+  if (argc != 3) usage();
+
+  int count = atoi(argv[1]);
+
+  // Two modes: "_Exit" ==> exit early w/o calling dtors, "exit" ==> call dtors on exit.
+  std::string mode = argv[2];
+  if (mode != "_Exit" && mode != "exit") usage();
+
+  for (int i = 0; i < count; ++i) {
+    __cxa_atexit(g_pdtor_func, nullptr, &__dso_handle);
+  }
+
+  if (mode == "_Exit") {
+    _Exit(0);
+  } else {
+    exit(0);
+  }
+}

benchmarks/spawn/spawn_benchmarks.cpp

@@ -31,6 +31,8 @@
 SPAWN_BENCHMARK(noop, test_program("bench_noop").c_str());
 SPAWN_BENCHMARK(noop_nostl, test_program("bench_noop_nostl").c_str());
 SPAWN_BENCHMARK(noop_static, test_program("bench_noop_static").c_str());
+SPAWN_BENCHMARK(bench_cxa_atexit, test_program("bench_cxa_atexit").c_str(), "100000", "_Exit");
+SPAWN_BENCHMARK(bench_cxa_atexit_full, test_program("bench_cxa_atexit").c_str(), "100000", "exit");
 
 // Android has a /bin -> /system/bin symlink, but use /system/bin explicitly so we can more easily
 // compare Bionic-vs-glibc on a Linux desktop machine.