Implement tracing interface for v8

src/tracing/trace-event.h

Index: src/tracing/trace-event.h
diff --git a/src/tracing/trace-event.h b/src/tracing/trace-event.h
new file mode 100644
index 0000000000000000000000000000000000000000..a9f36c08010515e57b3778b2de073d3e7b7aeff6
--- /dev/null
+++ b/src/tracing/trace-event.h
@@ -0,0 +1,515 @@
+// Copyright 2015 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef SRC_TRACING_TRACE_EVENT_H_
+#define SRC_TRACING_TRACE_EVENT_H_
+
+// This header file defines implementation details of how the trace macros in
+// trace_event_common.h collect and store trace events. Anything not
+// implementation-specific should go in trace_macros_common.h instead of here.
+
+#include "include/v8-tracing.h"
+#include "src/tracing/trace-event-common.h"
+
+// By default, const char* argument values are assumed to have long-lived scope
+// and will not be copied. Use this macro to force a const char* to be copied.
+#define TRACE_STR_COPY(str) v8::internal::tracing::TraceStringWithCopy(str)
+
+// By default, uint64 ID argument values are not mangled with the Process ID in
+// TRACE_EVENT_ASYNC macros. Use this macro to force Process ID mangling.
+#define TRACE_ID_MANGLE(id) v8::internal::tracing::TraceID::ForceMangle(id)
+
+// By default, pointers are mangled with the Process ID in TRACE_EVENT_ASYNC
+// macros. Use this macro to prevent Process ID mangling.
+#define TRACE_ID_DONT_MANGLE(id) v8::internal::tracing::TraceID::DontMangle(id)
+
+// Sets the current sample state to the given category and name (both must be
+// constant strings). These states are intended for a sampling profiler.
+// Implementation note: we store category and name together because we don't
+// want the inconsistency/expense of storing two pointers.
+// |thread_bucket| is [0..2] and is used to statically isolate samples in one
+// thread from others.
+#define TRACE_EVENT_SET_SAMPLING_STATE_FOR_BUCKET(bucket_number, category, \
+                                                  name)                    \
+  v8::internal::tracing::TraceEventSamplingStateScope<bucket_number>::Set( \
+      category "\0" name)
+
+// Returns a current sampling state of the given bucket.
+#define TRACE_EVENT_GET_SAMPLING_STATE_FOR_BUCKET(bucket_number) \
+  v8::internal::tracing::TraceEventSamplingStateScope<bucket_number>::Current()
+
+// Creates a scope of a sampling state of the given bucket.
+//
+// {  // The sampling state is set within this scope.
+//    TRACE_EVENT_SAMPLING_STATE_SCOPE_FOR_BUCKET(0, "category", "name");
+//    ...;
+// }
+#define TRACE_EVENT_SCOPED_SAMPLING_STATE_FOR_BUCKET(bucket_number, category, \
+                                                     name)                    \
+  trace_event_internal::TraceEventSamplingStateScope<bucket_number>           \
+      traceEventSamplingScope(category "\0" name);
+
+
+#define INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE() \
+  *INTERNAL_TRACE_EVENT_UID(category_group_enabled) &                    \
+      (EventTracer::kEnabledForRecording_CategoryGroupEnabledFlags |     \
+       EventTracer::kEnabledForEventCallback_CategoryGroupEnabledFlags)
+
+#define INTERNAL_TRACE_MEMORY(category, name)
+

[dsinclair, 2015/08/25 13:56:22]

Should this be UNIMPLEMENTED()?

[fmeawad, 2015/08/25 21:32:01]

No, because it is OK for it to have no implementation, as it gets called from
all trace events.
For those trace events, they will work as expected except without memory
tracing.
Added a comment.

+////////////////////////////////////////////////////////////////////////////////
+// Implementation specific tracing API definitions.
+
+// Get a pointer to the enabled state of the given trace category. Only
+// long-lived literal strings should be given as the category group. The
+// returned pointer can be held permanently in a local static for example. If
+// the unsigned char is non-zero, tracing is enabled. If tracing is enabled,
+// TRACE_EVENT_API_ADD_TRACE_EVENT can be called. It's OK if tracing is disabled
+// between the load of the tracing state and the call to
+// TRACE_EVENT_API_ADD_TRACE_EVENT, because this flag only provides an early out
+// for best performance when tracing is disabled.
+// const uint8_t*
+//     TRACE_EVENT_API_GET_CATEGORY_GROUP_ENABLED(const char* category_group)
+#define TRACE_EVENT_API_GET_CATEGORY_GROUP_ENABLED \
+  EventTracer::GetInstance()->GetCategoryGroupEnabled
+
+// Get the number of times traces have been recorded. This is used to implement
+// the TRACE_EVENT_IS_NEW_TRACE facility.
+// unsigned int TRACE_EVENT_API_GET_NUM_TRACES_RECORDED()
+#define TRACE_EVENT_API_GET_NUM_TRACES_RECORDED \
+  EventTracer::GetInstance()->getNumTracesRecorded
+
+// Add a trace event to the platform tracing system.
+// EventTracer::Handle TRACE_EVENT_API_ADD_TRACE_EVENT(
+//                    char phase,
+//                    const uint8_t* category_group_enabled,
+//                    const char* name,
+//                    uint64_t id,
+//                    uint64_t context_id,
+//                    uint64_t bind_id,
+//                    int num_args,
+//                    const char** arg_names,
+//                    const uint8_t* arg_types,
+//                    const uint64_t* arg_values,
+//                    unsigned int flags)
+#define TRACE_EVENT_API_ADD_TRACE_EVENT \
+  EventTracer::GetInstance()->AddTraceEvent
+
+// Set the duration field of a COMPLETE trace event.
+// void TRACE_EVENT_API_UPDATE_TRACE_EVENT_DURATION(
+//     const uint8_t* category_group_enabled,
+//     const char* name,
+//     EventTracer::Handle id)
+#define TRACE_EVENT_API_UPDATE_TRACE_EVENT_DURATION \
+  EventTracer::GetInstance()->UpdateTraceEventDuration
+
+// These operations are atomic in the Chrome tracing implementation
+// to cater to ARM's weak memory consistency; we're just doing read/
+// write here because it's not strictly needed for correctness.
+// So says Nat.
+// FIXME

[dsinclair, 2015/08/25 13:56:22]

crbug?

[fmeawad, 2015/08/25 21:32:01]

I fixed the implementation, was a left out of a copy from Skia that has long
been fix, thanks for the catch.

+
+#define TRACE_EVENT_API_ATOMIC_WORD intptr_t
+#define TRACE_EVENT_API_ATOMIC_LOAD(var) (*(&var))
+#define TRACE_EVENT_API_ATOMIC_STORE(var, value) (var = value)
+
+// Defines visibility for classes in trace_event.h
+// #define TRACE_EVENT_API_CLASS_EXPORT _API
+
+// The thread buckets for the sampling profiler.
+extern TRACE_EVENT_API_ATOMIC_WORD g_trace_state[3];
+
+#define TRACE_EVENT_API_THREAD_BUCKET(thread_bucket) \
+  g_trace_state[thread_bucket]
+
+////////////////////////////////////////////////////////////////////////////////
+
+// Implementation detail: trace event macros create temporary variables
+// to keep instrumentation overhead low. These macros give each temporary
+// variable a unique name based on the line number to prevent name collisions.
+#define INTERNAL_TRACE_EVENT_UID3(a, b) trace_event_unique_##a##b
+#define INTERNAL_TRACE_EVENT_UID2(a, b) INTERNAL_TRACE_EVENT_UID3(a, b)
+#define INTERNAL_TRACE_EVENT_UID(name_prefix) \
+  INTERNAL_TRACE_EVENT_UID2(name_prefix, __LINE__)
+
+// Implementation detail: internal macro to create static category.
+// No barriers are needed, because this code is designed to operate safely
+// even when the unsigned char* points to garbage data (which may be the case
+// on processors without cache coherency).
+#define INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO_CUSTOM_VARIABLES(             \
+    category_group, atomic, category_group_enabled)                          \
+  category_group_enabled =                                                   \
+      reinterpret_cast<const uint8_t*>(TRACE_EVENT_API_ATOMIC_LOAD(atomic)); \
+  if (!category_group_enabled) {                                             \
+    category_group_enabled =                                                 \
+        TRACE_EVENT_API_GET_CATEGORY_GROUP_ENABLED(category_group);          \
+    TRACE_EVENT_API_ATOMIC_STORE(                                            \
+        atomic, reinterpret_cast<TRACE_EVENT_API_ATOMIC_WORD>(               \
+                    category_group_enabled));                                \
+  }
+
+#define INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group)             \
+  static TRACE_EVENT_API_ATOMIC_WORD INTERNAL_TRACE_EVENT_UID(atomic) = 0; \
+  const uint8_t* INTERNAL_TRACE_EVENT_UID(category_group_enabled);         \
+  INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO_CUSTOM_VARIABLES(                 \
+      category_group, INTERNAL_TRACE_EVENT_UID(atomic),                    \
+      INTERNAL_TRACE_EVENT_UID(category_group_enabled));
+
+// Implementation detail: internal macro to create static category and add
+// event if the category is enabled.
+#define INTERNAL_TRACE_EVENT_ADD(phase, category_group, name, flags, ...)    \
+  do {                                                                       \
+    INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group);                  \
+    if (INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE()) {  \
+      v8::internal::tracing::AddTraceEvent(                                  \
+          phase, INTERNAL_TRACE_EVENT_UID(category_group_enabled), name,     \
+          v8::internal::tracing::kNoId, v8::internal::tracing::kNoId, flags, \
+          ##__VA_ARGS__);                                                    \
+    }                                                                        \
+  } while (0)
+
+// Implementation detail: internal macro to create static category and add begin
+// event if the category is enabled. Also adds the end event when the scope
+// ends.
+#define INTERNAL_TRACE_EVENT_ADD_SCOPED(category_group, name, ...)          \
+  INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group);                   \
+  v8::internal::tracing::ScopedTracer INTERNAL_TRACE_EVENT_UID(tracer);     \
+  if (INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE()) {   \
+    EventTracer::Handle h = v8::internal::tracing::AddTraceEvent(           \
+        TRACE_EVENT_PHASE_COMPLETE,                                         \
+        INTERNAL_TRACE_EVENT_UID(category_group_enabled), name,             \
+        v8::internal::tracing::kNoId, TRACE_EVENT_FLAG_NONE,                \
+        v8::internal::tracing::kNoId, ##__VA_ARGS__);                       \
+    INTERNAL_TRACE_EVENT_UID(tracer)                                        \
+        .Initialize(INTERNAL_TRACE_EVENT_UID(category_group_enabled), name, \
+                    h);                                                     \
+  }
+
+#define INTERNAL_TRACE_EVENT_ADD_SCOPED_WITH_FLOW(category_group, name,     \
+                                                  bind_id, flow_flags, ...) \
+  INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group);                   \
+  v8::internal::tracing::ScopedTracer INTERNAL_TRACE_EVENT_UID(tracer);     \
+  if (INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE()) {   \
+    unsigned int trace_event_flags = flow_flags;                            \
+    v8::internal::tracing::TraceID trace_event_bind_id(bind_id,             \
+                                                       &trace_event_flags); \
+    EventTracer::Handle h = v8::internal::tracing::AddTraceEvent(           \
+        TRACE_EVENT_PHASE_COMPLETE,                                         \
+        INTERNAL_TRACE_EVENT_UID(category_group_enabled), name,             \
+        v8::internal::tracing::kNoId, trace_event_bind_id.data(),           \
+        trace_event_flags, ##__VA_ARGS__);                                  \
+    INTERNAL_TRACE_EVENT_UID(tracer)                                        \
+        .Initialize(INTERNAL_TRACE_EVENT_UID(category_group_enabled), name, \
+                    h);                                                     \
+  }
+
+// Implementation detail: internal macro to create static category and add
+// event if the category is enabled.
+#define INTERNAL_TRACE_EVENT_ADD_WITH_ID(phase, category_group, name, id,      \
+                                         flags, ...)                           \
+  do {                                                                         \
+    INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group);                    \
+    if (INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE()) {    \
+      unsigned int trace_event_flags = flags | TRACE_EVENT_FLAG_HAS_ID;        \
+      v8::internal::tracing::TraceID trace_event_trace_id(id,                  \
+                                                          &trace_event_flags); \
+      v8::internal::tracing::AddTraceEvent(                                    \
+          phase, INTERNAL_TRACE_EVENT_UID(category_group_enabled), name,       \
+          trace_event_trace_id.data(), v8::internal::tracing::kNoId,           \
+          trace_event_flags, ##__VA_ARGS__);                                   \
+    }                                                                          \
+  } while (0)
+
+// Adds a trace event with a given timestamp. Not Implemented.
+#define INTERNAL_TRACE_EVENT_ADD_WITH_TIMESTAMP(phase, category_group, name, \
+                                                timestamp, flags, ...)       \
+  UNIMPLEMENTED()
+
+// Adds a trace event with a given id and timestamp. Not Implemented.
+#define INTERNAL_TRACE_EVENT_ADD_WITH_ID_AND_TIMESTAMP(     \
+    phase, category_group, name, id, timestamp, flags, ...) \
+  UNIMPLEMENTED()
+
+// Adds a trace event with a given id, thread_id, and timestamp. Not
+// Implemented.
+#define INTERNAL_TRACE_EVENT_ADD_WITH_ID_TID_AND_TIMESTAMP(            \
+    phase, category_group, name, id, thread_id, timestamp, flags, ...) \
+  UNIMPLEMENTED()
+
+
+#ifndef INTERNAL_GET_TRACE_CONTEXT_ID
+#define INTERNAL_GET_TRACE_CONTEXT_ID \
+  (uint64_t) v8::internal::Isolate::UnsafeCurrent
+#endif
+
+namespace v8 {
+namespace internal {
+namespace tracing {
+
+// Specify these values when the corresponding argument of AddTraceEvent is not
+// used.
+const int kZeroNumArgs = 0;
+const uint64_t kNoId = 0;
+
+// TraceID encapsulates an ID that can either be an integer or pointer. Pointers
+// are by default mangled with the Process ID so that they are unlikely to
+// collide when the same pointer is used on different processes.
+class TraceID {
+ public:
+  class DontMangle {
+   public:
+    explicit DontMangle(const void* id)
+        : data_(static_cast<uint64_t>(reinterpret_cast<uintptr_t>(id))) {}
+    explicit DontMangle(uint64_t id) : data_(id) {}
+    explicit DontMangle(unsigned int id) : data_(id) {}
+    explicit DontMangle(uint16_t id) : data_(id) {}
+    explicit DontMangle(unsigned char id) : data_(id) {}
+    explicit DontMangle(int64_t id) : data_(static_cast<uint64_t>(id)) {}
+    explicit DontMangle(int id) : data_(static_cast<uint64_t>(id)) {}
+    explicit DontMangle(int16_t id) : data_(static_cast<uint64_t>(id)) {}
+    explicit DontMangle(signed char id) : data_(static_cast<uint64_t>(id)) {}
+    uint64_t data() const { return data_; }
+
+   private:
+    uint64_t data_;
+  };
+
+  class ForceMangle {
+   public:
+    explicit ForceMangle(uint64_t id) : data_(id) {}
+    explicit ForceMangle(unsigned int id) : data_(id) {}
+    explicit ForceMangle(uint16_t id) : data_(id) {}
+    explicit ForceMangle(unsigned char id) : data_(id) {}
+    explicit ForceMangle(int64_t id) : data_(static_cast<uint64_t>(id)) {}
+    explicit ForceMangle(int id) : data_(static_cast<uint64_t>(id)) {}
+    explicit ForceMangle(int16_t id) : data_(static_cast<uint64_t>(id)) {}
+    explicit ForceMangle(signed char id) : data_(static_cast<uint64_t>(id)) {}
+    uint64_t data() const { return data_; }
+
+   private:
+    uint64_t data_;
+  };
+
+  TraceID(const void* id, unsigned int* flags)
+      : data_(static_cast<uint64_t>(reinterpret_cast<uintptr_t>(id))) {
+    *flags |= TRACE_EVENT_FLAG_MANGLE_ID;
+  }
+  TraceID(ForceMangle id, unsigned int* flags) : data_(id.data()) {
+    *flags |= TRACE_EVENT_FLAG_MANGLE_ID;
+  }
+  TraceID(DontMangle id, unsigned int* flags) : data_(id.data()) {}
+  TraceID(uint64_t id, unsigned int* flags) : data_(id) { (void)flags; }
+  TraceID(unsigned int id, unsigned int* flags) : data_(id) { (void)flags; }
+  TraceID(uint16_t id, unsigned int* flags) : data_(id) { (void)flags; }
+  TraceID(unsigned char id, unsigned int* flags) : data_(id) { (void)flags; }
+  TraceID(int64_t id, unsigned int* flags) : data_(static_cast<uint64_t>(id)) {
+    (void)flags;
+  }
+  TraceID(int id, unsigned int* flags) : data_(static_cast<uint64_t>(id)) {
+    (void)flags;
+  }
+  TraceID(int16_t id, unsigned int* flags) : data_(static_cast<uint64_t>(id)) {
+    (void)flags;
+  }
+  TraceID(signed char id, unsigned int* flags)
+      : data_(static_cast<uint64_t>(id)) {
+    (void)flags;
+  }
+
+  uint64_t data() const { return data_; }
+
+ private:
+  uint64_t data_;
+};
+
+// Simple union to store various types as uint64_t.
+union TraceValueUnion {
+  bool as_bool;
+  uint64_t as_uint;
+  int64_t as_int;
+  double as_double;
+  const void* as_pointer;
+  const char* as_string;
+};
+
+// Simple container for const char* that should be copied instead of retained.
+class TraceStringWithCopy {
+ public:
+  explicit TraceStringWithCopy(const char* str) : str_(str) {}
+  operator const char*() const { return str_; }
+
+ private:
+  const char* str_;
+};
+
+// Define SetTraceValue for each allowed type. It stores the type and
+// value in the return arguments. This allows this API to avoid declaring any
+// structures so that it is portable to third_party libraries.
+#define INTERNAL_DECLARE_SET_TRACE_VALUE(actual_type, union_member,      \
+                                         value_type_id)                  \
+  static inline void SetTraceValue(actual_type arg, unsigned char* type, \
+                                   uint64_t* value) {                    \
+    TraceValueUnion type_value;                                          \
+    type_value.union_member = arg;                                       \
+    *type = value_type_id;                                               \
+    *value = type_value.as_uint;                                         \
+  }
+// Simpler form for int types that can be safely casted.
+#define INTERNAL_DECLARE_SET_TRACE_VALUE_INT(actual_type, value_type_id) \
+  static inline void SetTraceValue(actual_type arg, unsigned char* type, \
+                                   uint64_t* value) {                    \
+    *type = value_type_id;                                               \
+    *value = static_cast<uint64_t>(arg);                                 \
+  }
+
+INTERNAL_DECLARE_SET_TRACE_VALUE_INT(uint64_t, TRACE_VALUE_TYPE_UINT)
+INTERNAL_DECLARE_SET_TRACE_VALUE_INT(unsigned int, TRACE_VALUE_TYPE_UINT)
+INTERNAL_DECLARE_SET_TRACE_VALUE_INT(uint16_t, TRACE_VALUE_TYPE_UINT)
+INTERNAL_DECLARE_SET_TRACE_VALUE_INT(unsigned char, TRACE_VALUE_TYPE_UINT)
+INTERNAL_DECLARE_SET_TRACE_VALUE_INT(int64_t, TRACE_VALUE_TYPE_INT)
+INTERNAL_DECLARE_SET_TRACE_VALUE_INT(int, TRACE_VALUE_TYPE_INT)
+INTERNAL_DECLARE_SET_TRACE_VALUE_INT(int16_t, TRACE_VALUE_TYPE_INT)
+INTERNAL_DECLARE_SET_TRACE_VALUE_INT(signed char, TRACE_VALUE_TYPE_INT)
+INTERNAL_DECLARE_SET_TRACE_VALUE(bool, as_bool, TRACE_VALUE_TYPE_BOOL)
+INTERNAL_DECLARE_SET_TRACE_VALUE(double, as_double, TRACE_VALUE_TYPE_DOUBLE)
+INTERNAL_DECLARE_SET_TRACE_VALUE(const void*, as_pointer,
+                                 TRACE_VALUE_TYPE_POINTER)
+INTERNAL_DECLARE_SET_TRACE_VALUE(const char*, as_string,
+                                 TRACE_VALUE_TYPE_STRING)
+INTERNAL_DECLARE_SET_TRACE_VALUE(const TraceStringWithCopy&, as_string,
+                                 TRACE_VALUE_TYPE_COPY_STRING)
+
+#undef INTERNAL_DECLARE_SET_TRACE_VALUE
+#undef INTERNAL_DECLARE_SET_TRACE_VALUE_INT
+
+// These AddTraceEvent template
+// function is defined here instead of in the macro, because the arg_values
+// could be temporary objects, such as std::string. In order to store
+// pointers to the internal c_str and pass through to the tracing API,
+// the arg_values must live throughout these procedures.
+
+static inline EventTracer::Handle AddTraceEvent(
+    char phase, const uint8_t* category_group_enabled, const char* name,
+    uint64_t id, uint64_t bind_id, unsigned int flags) {
+  return TRACE_EVENT_API_ADD_TRACE_EVENT(
+      phase, category_group_enabled, name, id, INTERNAL_GET_TRACE_CONTEXT_ID(),
+      bind_id, kZeroNumArgs, NULL, NULL, NULL,
+      flags | TRACE_EVENT_FLAG_HAS_CONTEXT_ID);
+}
+
+template <class ARG1_TYPE>
+static inline EventTracer::Handle AddTraceEvent(
+    char phase, const uint8_t* category_group_enabled, const char* name,
+    uint64_t id, uint64_t bind_id, unsigned int flags, const char* arg1_name,
+    const ARG1_TYPE& arg1_val) {
+  const int num_args = 1;
+  uint8_t arg_types[1];
+  uint64_t arg_values[1];
+  SetTraceValue(arg1_val, &arg_types[0], &arg_values[0]);
+  return TRACE_EVENT_API_ADD_TRACE_EVENT(
+      phase, category_group_enabled, name, id, INTERNAL_GET_TRACE_CONTEXT_ID(),
+      bind_id, num_args, &arg1_name, arg_types, arg_values,
+      flags | TRACE_EVENT_FLAG_HAS_CONTEXT_ID);
+}
+
+template <class ARG1_TYPE, class ARG2_TYPE>
+static inline EventTracer::Handle AddTraceEvent(
+    char phase, const uint8_t* category_group_enabled, const char* name,
+    uint64_t id, uint64_t bind_id, unsigned int flags, const char* arg1_name,
+    const ARG1_TYPE& arg1_val, const char* arg2_name,
+    const ARG2_TYPE& arg2_val) {
+  const int num_args = 2;
+  const char* arg_names[2] = {arg1_name, arg2_name};
+  unsigned char arg_types[2];
+  uint64_t arg_values[2];
+  SetTraceValue(arg1_val, &arg_types[0], &arg_values[0]);
+  SetTraceValue(arg2_val, &arg_types[1], &arg_values[1]);
+  return TRACE_EVENT_API_ADD_TRACE_EVENT(
+      phase, category_group_enabled, name, id, INTERNAL_GET_TRACE_CONTEXT_ID(),
+      bind_id, num_args, arg_names, arg_types, arg_values,
+      flags | TRACE_EVENT_FLAG_HAS_CONTEXT_ID);
+}
+
+// Used by TRACE_EVENTx macros. Do not use directly.
+class ScopedTracer {
+ public:
+  // Note: members of data_ intentionally left uninitialized. See Initialize.
+  ScopedTracer() : p_data_(NULL) {}
+
+  ~ScopedTracer() {
+    if (p_data_ && *data_.category_group_enabled)
+      TRACE_EVENT_API_UPDATE_TRACE_EVENT_DURATION(
+          data_.category_group_enabled, data_.name, data_.event_handle);
+  }
+
+  void Initialize(const uint8_t* category_group_enabled, const char* name,
+                  EventTracer::Handle event_handle) {
+    data_.category_group_enabled = category_group_enabled;
+    data_.name = name;
+    data_.event_handle = event_handle;
+    p_data_ = &data_;
+  }
+
+ private:
+  // This Data struct workaround is to avoid initializing all the members
+  // in Data during construction of this object, since this object is always
+  // constructed, even when tracing is disabled. If the members of Data were
+  // members of this class instead, compiler warnings occur about potential
+  // uninitialized accesses.
+  struct Data {
+    const uint8_t* category_group_enabled;
+    const char* name;
+    EventTracer::Handle event_handle;
+  };
+  Data* p_data_;
+  Data data_;
+};
+
+// Used by TRACE_EVENT_BINARY_EFFICIENTx macro. Do not use directly.
+class ScopedTraceBinaryEfficient {
+ public:
+  ScopedTraceBinaryEfficient(const char* category_group, const char* name);
+  ~ScopedTraceBinaryEfficient();
+
+ private:
+  const uint8_t* category_group_enabled_;
+  const char* name_;
+  EventTracer::Handle event_handle_;
+};
+
+// TraceEventSamplingStateScope records the current sampling state
+// and sets a new sampling state. When the scope exists, it restores
+// the sampling state having recorded.
+template <size_t BucketNumber>
+class TraceEventSamplingStateScope {
+ public:
+  explicit TraceEventSamplingStateScope(const char* category_and_name) {
+    previous_state_ = TraceEventSamplingStateScope<BucketNumber>::Current();
+    TraceEventSamplingStateScope<BucketNumber>::Set(category_and_name);
+  }
+
+  ~TraceEventSamplingStateScope() {
+    TraceEventSamplingStateScope<BucketNumber>::Set(previous_state_);
+  }
+
+  static inline const char* Current() {
+    return reinterpret_cast<const char*>(
+        TRACE_EVENT_API_ATOMIC_LOAD(g_trace_state[BucketNumber]));
+  }
+
+  static inline void Set(const char* category_and_name) {
+    TRACE_EVENT_API_ATOMIC_STORE(g_trace_state[BucketNumber],
+                                 reinterpret_cast<TRACE_EVENT_API_ATOMIC_WORD>(
+                                     const_cast<char*>(category_and_name)));
+  }
+
+ private:
+  const char* previous_state_;
+};
+
+}  // namespace tracing
+}  // namespace internal
+}  // namespace v8
+
+#endif  // SRC_TRACING_TRACE_EVENT_H_