[libcxx] Add support for benchmark tests using Google Benchmark.

Summary:
This patch does the following:

1. Checks in a copy of the Google Benchmark library into the libc++ repo under `utils/google-benchmark`.
2. Teaches libc++ how to build Google Benchmark against both (A) in-tree libc++ and (B) the platforms native STL.
3. Allows performance benchmarks to be built as part of the libc++ build.

Building the benchmarks (and Google Benchmark) is off by default. It must be enabled using the CMake option `-DLIBCXX_INCLUDE_BENCHMARKS=ON`. When this option is enabled the tests under `libcxx/benchmarks`  can be built using the `libcxx-benchmarks` target.

On Linux platforms where libstdc++ is the default STL the CMake option `-DLIBCXX_BUILD_BENCHMARKS_NATIVE_STDLIB=ON` can be used to build each benchmark test against libstdc++ as well. This is useful for comparing performance between standard libraries.

Support for benchmarks is currently very minimal. They must be manually run by the user and there is no mechanism for detecting performance regressions.

Known Issues:

* `-DLIBCXX_INCLUDE_BENCHMARKS=ON` is only supported for Clang, and not GCC, since the `-stdlib=libc++` option is needed to build Google Benchmark.








Reviewers: danalbert, dberlin, chandlerc, mclow.lists, jroelofs

Subscribers: chandlerc, dberlin, tberghammer, danalbert, srhines, hfinkel

Differential Revision: https://reviews.llvm.org/D22240

llvm-svn: 276049

1 files changed, 124 insertions, 0 deletions

diff --git a/libcxx/utils/google-benchmark/src/console_reporter.cc b/libcxx/utils/google-benchmark/src/console_reporter.cc
new file mode 100644
index 00000000000..080c324af11
--- /dev/null
+++ b/libcxx/utils/google-benchmark/src/console_reporter.cc
@@ -0,0 +1,124 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// 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/reporter.h"
+#include "complexity.h"
+
+#include <algorithm>
+#include <cstdint>
+#include <cstdio>
+#include <iostream>
+#include <string>
+#include <tuple>
+#include <vector>
+
+#include "check.h"
+#include "colorprint.h"
+#include "commandlineflags.h"
+#include "internal_macros.h"
+#include "string_util.h"
+#include "walltime.h"
+
+DECLARE_bool(color_print);
+
+namespace benchmark {
+
+bool ConsoleReporter::ReportContext(const Context& context) {
+  name_field_width_ = context.name_field_width;
+
+  PrintBasicContext(&GetErrorStream(), context);
+
+#ifdef BENCHMARK_OS_WINDOWS
+  if (FLAGS_color_print && &std::cout != &GetOutputStream()) {
+      GetErrorStream() << "Color printing is only supported for stdout on windows."
+                          " Disabling color printing\n";
+      FLAGS_color_print = false;
+  }
+#endif
+  std::string str = FormatString("%-*s %13s %13s %10s\n",
+                             static_cast<int>(name_field_width_), "Benchmark",
+                             "Time", "CPU", "Iterations");
+  GetOutputStream() << str << std::string(str.length() - 1, '-') << "\n";
+
+  return true;
+}
+
+void ConsoleReporter::ReportRuns(const std::vector<Run>& reports) {
+  for (const auto& run : reports)
+    PrintRunData(run);
+}
+
+void ConsoleReporter::PrintRunData(const Run& result) {
+  auto& Out = GetOutputStream();
+
+  auto name_color =
+      (result.report_big_o || result.report_rms) ? COLOR_BLUE : COLOR_GREEN;
+  ColorPrintf(Out, name_color, "%-*s ", name_field_width_,
+              result.benchmark_name.c_str());
+
+  if (result.error_occurred) {
+    ColorPrintf(Out, COLOR_RED, "ERROR OCCURRED: \'%s\'",
+                result.error_message.c_str());
+    ColorPrintf(Out, COLOR_DEFAULT, "\n");
+    return;
+  }
+  // Format bytes per second
+  std::string rate;
+  if (result.bytes_per_second > 0) {
+    rate = StrCat(" ", HumanReadableNumber(result.bytes_per_second), "B/s");
+  }
+
+  // Format items per second
+  std::string items;
+  if (result.items_per_second > 0) {
+    items = StrCat(" ", HumanReadableNumber(result.items_per_second),
+                   " items/s");
+ }
+
+  const double real_time = result.GetAdjustedRealTime();
+  const double cpu_time = result.GetAdjustedCPUTime();
+
+  if (result.report_big_o) {
+    std::string big_o = GetBigOString(result.complexity);
+    ColorPrintf(Out, COLOR_YELLOW, "%10.2f %s %10.2f %s ", real_time,
+                big_o.c_str(), cpu_time, big_o.c_str());
+  } else if (result.report_rms) {
+    ColorPrintf(Out, COLOR_YELLOW, "%10.0f %% %10.0f %% ", real_time * 100,
+                cpu_time * 100);
+  } else {
+    const char* timeLabel = GetTimeUnitString(result.time_unit);
+    ColorPrintf(Out, COLOR_YELLOW, "%10.0f %s %10.0f %s ", real_time, timeLabel,
+                cpu_time, timeLabel);
+  }
+
+  if (!result.report_big_o && !result.report_rms) {
+    ColorPrintf(Out, COLOR_CYAN, "%10lld", result.iterations);
+  }
+
+  if (!rate.empty()) {
+    ColorPrintf(Out, COLOR_DEFAULT, " %*s", 13, rate.c_str());
+  }
+
+  if (!items.empty()) {
+    ColorPrintf(Out, COLOR_DEFAULT, " %*s", 18, items.c_str());
+  }
+
+  if (!result.report_label.empty()) {
+    ColorPrintf(Out, COLOR_DEFAULT, " %s", result.report_label.c_str());
+  }
+
+  ColorPrintf(Out, COLOR_DEFAULT, "\n");
+}
+
+}  // end namespace benchmark