folly: replace old-style header guards with "pragma once"

[folly.git] / folly / Benchmark.h

diff --git a/folly/Benchmark.h b/folly/Benchmark.h
index 0ca2b167bb531478d51acc7bd29b7e769953947a..0a384b40aaef98799b76ebf9b9ef102943cbbde2 100644 (file)
--- a/folly/Benchmark.h
+++ b/folly/Benchmark.h
@@ -1,5 +1,5 @@
 /*
- * Copyright 2014 Facebook, Inc.
+ * Copyright 2016 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -14,11 +14,13 @@
  * limitations under the License.
  */
 
-#ifndef FOLLY_BENCHMARK_H_
-#define FOLLY_BENCHMARK_H_
+#pragma once
+
+#include <folly/Portability.h>
+#include <folly/Preprocessor.h> // for FB_ANONYMOUS_VARIABLE
+#include <folly/ScopeGuard.h>
+#include <folly/portability/Time.h>
 
-#include "folly/Portability.h"
-#include "folly/Preprocessor.h" // for FB_ANONYMOUS_VARIABLE
 #include <cassert>
 #include <ctime>
 #include <boost/function_types/function_arity.hpp>
@@ -26,6 +28,7 @@
 #include <glog/logging.h>
 #include <gflags/gflags.h>
 #include <limits>
+#include <type_traits>
 
 DECLARE_bool(benchmark);
 
@@ -75,10 +78,11 @@ inline uint64_t timespecDiff(timespec end, timespec start) {
     assert(end.tv_nsec >= start.tv_nsec);
     return end.tv_nsec - start.tv_nsec;
   }
-  assert(end.tv_sec > start.tv_sec &&
-         end.tv_sec - start.tv_sec <
+  assert(end.tv_sec > start.tv_sec);
+  auto diff = uint64_t(end.tv_sec - start.tv_sec);
+  assert(diff <
          std::numeric_limits<uint64_t>::max() / 1000000000UL);
-  return (end.tv_sec - start.tv_sec) * 1000000000UL
+  return diff * 1000000000UL
     + end.tv_nsec - start.tv_nsec;
 }
 
@@ -116,7 +120,7 @@ struct BenchmarkSuspender {
   }
 
   BenchmarkSuspender(const BenchmarkSuspender &) = delete;
-  BenchmarkSuspender(BenchmarkSuspender && rhs) {
+  BenchmarkSuspender(BenchmarkSuspender && rhs) noexcept {
     start = rhs.start;
     rhs.start.tv_nsec = rhs.start.tv_sec = 0;
   }
@@ -148,13 +152,19 @@ struct BenchmarkSuspender {
     CHECK_EQ(0, clock_gettime(detail::DEFAULT_CLOCK_ID, &start));
   }
 
+  template <class F>
+  auto dismissing(F f) -> typename std::result_of<F()>::type {
+    SCOPE_EXIT { rehire(); };
+    dismiss();
+    return f();
+  }
+
   /**
-   * This helps the macro definition. To get around the dangers of
-   * operator bool, returns a pointer to member (which allows no
-   * arithmetic).
+   * This is for use inside of if-conditions, used in BENCHMARK macros.
+   * If-conditions bypass the explicit on operator bool.
    */
-  operator int BenchmarkSuspender::*() const {
-    return nullptr;
+  explicit operator bool() const {
+    return false;
   }
 
   /**
@@ -248,11 +258,18 @@ void doNotOptimizeAway(T&& datum) {
 
 #pragma optimize("", on)
 
+#elif defined(__clang__)
+
+template <class T>
+__attribute__((__optnone__)) void doNotOptimizeAway(T&& /* datum */) {}
+
 #else
+
 template <class T>
 void doNotOptimizeAway(T&& datum) {
   asm volatile("" : "+r" (datum));
 }
+
 #endif
 
 } // namespace folly
@@ -284,11 +301,11 @@ void doNotOptimizeAway(T&& datum) {
   static unsigned funName(paramType paramName)
 
 /**
- * Introduces a benchmark function. Use with either one one or two
- * arguments. The first is the name of the benchmark. Use something
- * descriptive, such as insertVectorBegin. The second argument may be
- * missing, or could be a symbolic counter. The counter dictates how
- * many internal iteration the benchmark does. Example:
+ * Introduces a benchmark function. Use with either one or two arguments.
+ * The first is the name of the benchmark. Use something descriptive, such
+ * as insertVectorBegin. The second argument may be missing, or could be a
+ * symbolic counter. The counter dictates how many internal iteration the
+ * benchmark does. Example:
  *
  * BENCHMARK(vectorPushBack) {
  *   vector<int> v;
@@ -518,5 +535,3 @@ void doNotOptimizeAway(T&& datum) {
   if (auto FB_ANONYMOUS_VARIABLE(BENCHMARK_SUSPEND) =   \
       ::folly::BenchmarkSuspender()) {}                 \
   else
-
-#endif // FOLLY_BENCHMARK_H_