1 files changed, 109 insertions, 0 deletions
diff --git a/mozglue/misc/AutoProfilerLabel.cpp b/mozglue/misc/AutoProfilerLabel.cpp
new file mode 100644
index 0000000000..5fd820cc5b
--- /dev/null
+++ b/mozglue/misc/AutoProfilerLabel.cpp
@@ -0,0 +1,109 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/AutoProfilerLabel.h"
+
+#include "mozilla/Assertions.h"
+#include "mozilla/PlatformMutex.h"
+
+namespace mozilla {
+
+// RAII class that encapsulates all shared static data, and enforces locking
+// when accessing this data.
+class MOZ_RAII AutoProfilerLabelData {
+ public:
+  AutoProfilerLabelData() { sAPLMutex.Lock(); }
+
+  ~AutoProfilerLabelData() { sAPLMutex.Unlock(); }
+
+  AutoProfilerLabelData(const AutoProfilerLabelData&) = delete;
+  void operator=(const AutoProfilerLabelData&) = delete;
+
+  const ProfilerLabelEnter& EnterCRef() const { return sEnter; }
+  ProfilerLabelEnter& EnterRef() { return sEnter; }
+
+  const ProfilerLabelExit& ExitCRef() const { return sExit; }
+  ProfilerLabelExit& ExitRef() { return sExit; }
+
+  const uint32_t& GenerationCRef() const { return sGeneration; }
+  uint32_t& GenerationRef() { return sGeneration; }
+
+  static bool RacyIsProfilerPresent() { return !!sGeneration; }
+
+ private:
+  // Thin shell around mozglue PlatformMutex, for local internal use.
+  // Does not preserve behavior in JS record/replay.
+  class Mutex : private mozilla::detail::MutexImpl {
+   public:
+    Mutex() = default;
+    void Lock() { mozilla::detail::MutexImpl::lock(); }
+    void Unlock() { mozilla::detail::MutexImpl::unlock(); }
+  };
+
+  // Mutex protecting access to the following static members.
+  static Mutex sAPLMutex MOZ_UNANNOTATED;
+
+  static ProfilerLabelEnter sEnter;
+  static ProfilerLabelExit sExit;
+
+  // Current "generation" of RegisterProfilerLabelEnterExit calls.
+  static uint32_t sGeneration;
+};
+
+/* static */ AutoProfilerLabelData::Mutex AutoProfilerLabelData::sAPLMutex;
+/* static */ ProfilerLabelEnter AutoProfilerLabelData::sEnter = nullptr;
+/* static */ ProfilerLabelExit AutoProfilerLabelData::sExit = nullptr;
+/* static */ uint32_t AutoProfilerLabelData::sGeneration = 0;
+
+void RegisterProfilerLabelEnterExit(ProfilerLabelEnter aEnter,
+                                    ProfilerLabelExit aExit) {
+  MOZ_ASSERT(!aEnter == !aExit, "Must provide both null or both non-null");
+
+  AutoProfilerLabelData data;
+  MOZ_ASSERT(!aEnter != !data.EnterRef(),
+             "Must go from null to non-null, or from non-null to null");
+  data.EnterRef() = aEnter;
+  data.ExitRef() = aExit;
+  ++data.GenerationRef();
+}
+
+bool IsProfilerPresent() {
+  return AutoProfilerLabelData::RacyIsProfilerPresent();
+}
+
+ProfilerLabel ProfilerLabelBegin(const char* aLabelName,
+                                 const char* aDynamicString, void* aSp) {
+  const AutoProfilerLabelData data;
+  void* entryContext = (data.EnterCRef())
+                           ? data.EnterCRef()(aLabelName, aDynamicString, aSp)
+                           : nullptr;
+  uint32_t generation = data.GenerationCRef();
+
+  return std::make_tuple(entryContext, generation);
+}
+
+void ProfilerLabelEnd(const ProfilerLabel& aLabel) {
+  if (!IsValidProfilerLabel(aLabel)) {
+    return;
+  }
+
+  const AutoProfilerLabelData data;
+  if (data.ExitCRef() && (std::get<1>(aLabel) == data.GenerationCRef())) {
+    data.ExitCRef()(std::get<0>(aLabel));
+  }
+}
+
+AutoProfilerLabel::AutoProfilerLabel(const char* aLabel,
+                                     const char* aDynamicString) {
+  std::tie(mEntryContext, mGeneration) =
+      ProfilerLabelBegin(aLabel, aDynamicString, this);
+}
+
+AutoProfilerLabel::~AutoProfilerLabel() {
+  ProfilerLabelEnd(std::make_tuple(mEntryContext, mGeneration));
+}
+
+}  // namespace mozilla