1 files changed, 881 insertions, 0 deletions

diff --git a/tools/profiler/core/ProfileEntry.cpp b/tools/profiler/core/ProfileEntry.cpp
new file mode 100644
index 0000000000..22d53a6f30
--- /dev/null
+++ b/tools/profiler/core/ProfileEntry.cpp
@@ -0,0 +1,881 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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 <ostream>
+#include "platform.h"
+#include "mozilla/HashFunctions.h"
+
+#ifndef SPS_STANDALONE
+#include "nsThreadUtils.h"
+#include "nsXULAppAPI.h"
+
+// JS
+#include "jsapi.h"
+#include "jsfriendapi.h"
+#include "js/TrackedOptimizationInfo.h"
+#endif
+
+// Self
+#include "ProfileEntry.h"
+
+using mozilla::MakeUnique;
+using mozilla::UniquePtr;
+using mozilla::Maybe;
+using mozilla::Some;
+using mozilla::Nothing;
+using mozilla::JSONWriter;
+
+
+////////////////////////////////////////////////////////////////////////
+// BEGIN ProfileEntry
+
+ProfileEntry::ProfileEntry()
+  : mTagData(nullptr)
+  , mTagName(0)
+{ }
+
+// aTagData must not need release (i.e. be a string from the text segment)
+ProfileEntry::ProfileEntry(char aTagName, const char *aTagData)
+  : mTagData(aTagData)
+  , mTagName(aTagName)
+{ }
+
+ProfileEntry::ProfileEntry(char aTagName, ProfilerMarker *aTagMarker)
+  : mTagMarker(aTagMarker)
+  , mTagName(aTagName)
+{ }
+
+ProfileEntry::ProfileEntry(char aTagName, void *aTagPtr)
+  : mTagPtr(aTagPtr)
+  , mTagName(aTagName)
+{ }
+
+ProfileEntry::ProfileEntry(char aTagName, double aTagDouble)
+  : mTagDouble(aTagDouble)
+  , mTagName(aTagName)
+{ }
+
+ProfileEntry::ProfileEntry(char aTagName, uintptr_t aTagOffset)
+  : mTagOffset(aTagOffset)
+  , mTagName(aTagName)
+{ }
+
+ProfileEntry::ProfileEntry(char aTagName, Address aTagAddress)
+  : mTagAddress(aTagAddress)
+  , mTagName(aTagName)
+{ }
+
+ProfileEntry::ProfileEntry(char aTagName, int aTagInt)
+  : mTagInt(aTagInt)
+  , mTagName(aTagName)
+{ }
+
+ProfileEntry::ProfileEntry(char aTagName, char aTagChar)
+  : mTagChar(aTagChar)
+  , mTagName(aTagName)
+{ }
+
+bool ProfileEntry::is_ent_hint(char hintChar) {
+  return mTagName == 'h' && mTagChar == hintChar;
+}
+
+bool ProfileEntry::is_ent_hint() {
+  return mTagName == 'h';
+}
+
+bool ProfileEntry::is_ent(char tagChar) {
+  return mTagName == tagChar;
+}
+
+void* ProfileEntry::get_tagPtr() {
+  // No consistency checking.  Oh well.
+  return mTagPtr;
+}
+
+// END ProfileEntry
+////////////////////////////////////////////////////////////////////////
+
+class JSONSchemaWriter
+{
+  JSONWriter& mWriter;
+  uint32_t mIndex;
+
+public:
+  explicit JSONSchemaWriter(JSONWriter& aWriter)
+   : mWriter(aWriter)
+   , mIndex(0)
+  {
+    aWriter.StartObjectProperty("schema");
+  }
+
+  void WriteField(const char* aName) {
+    mWriter.IntProperty(aName, mIndex++);
+  }
+
+  ~JSONSchemaWriter() {
+    mWriter.EndObject();
+  }
+};
+
+#ifndef SPS_STANDALONE
+class StreamOptimizationTypeInfoOp : public JS::ForEachTrackedOptimizationTypeInfoOp
+{
+  JSONWriter& mWriter;
+  UniqueJSONStrings& mUniqueStrings;
+  bool mStartedTypeList;
+
+public:
+  StreamOptimizationTypeInfoOp(JSONWriter& aWriter, UniqueJSONStrings& aUniqueStrings)
+    : mWriter(aWriter)
+    , mUniqueStrings(aUniqueStrings)
+    , mStartedTypeList(false)
+  { }
+
+  void readType(const char* keyedBy, const char* name,
+                const char* location, Maybe<unsigned> lineno) override {
+    if (!mStartedTypeList) {
+      mStartedTypeList = true;
+      mWriter.StartObjectElement();
+      mWriter.StartArrayProperty("typeset");
+    }
+
+    mWriter.StartObjectElement();
+    {
+      mUniqueStrings.WriteProperty(mWriter, "keyedBy", keyedBy);
+      if (name) {
+        mUniqueStrings.WriteProperty(mWriter, "name", name);
+      }
+      if (location) {
+        mUniqueStrings.WriteProperty(mWriter, "location", location);
+      }
+      if (lineno.isSome()) {
+        mWriter.IntProperty("line", *lineno);
+      }
+    }
+    mWriter.EndObject();
+  }
+
+  void operator()(JS::TrackedTypeSite site, const char* mirType) override {
+    if (mStartedTypeList) {
+      mWriter.EndArray();
+      mStartedTypeList = false;
+    } else {
+      mWriter.StartObjectElement();
+    }
+
+    {
+      mUniqueStrings.WriteProperty(mWriter, "site", JS::TrackedTypeSiteString(site));
+      mUniqueStrings.WriteProperty(mWriter, "mirType", mirType);
+    }
+    mWriter.EndObject();
+  }
+};
+
+// As mentioned in ProfileEntry.h, the JSON format contains many arrays whose
+// elements are laid out according to various schemas to help
+// de-duplication. This RAII class helps write these arrays by keeping track of
+// the last non-null element written and adding the appropriate number of null
+// elements when writing new non-null elements. It also automatically opens and
+// closes an array element on the given JSON writer.
+//
+// Example usage:
+//
+//     // Define the schema of elements in this type of array: [FOO, BAR, BAZ]
+//     enum Schema : uint32_t {
+//       FOO = 0,
+//       BAR = 1,
+//       BAZ = 2
+//     };
+//
+//     AutoArraySchemaWriter writer(someJsonWriter, someUniqueStrings);
+//     if (shouldWriteFoo) {
+//       writer.IntElement(FOO, getFoo());
+//     }
+//     ... etc ...
+class MOZ_RAII AutoArraySchemaWriter
+{
+  friend class AutoObjectWriter;
+
+  SpliceableJSONWriter& mJSONWriter;
+  UniqueJSONStrings*    mStrings;
+  uint32_t              mNextFreeIndex;
+
+public:
+  AutoArraySchemaWriter(SpliceableJSONWriter& aWriter, UniqueJSONStrings& aStrings)
+    : mJSONWriter(aWriter)
+    , mStrings(&aStrings)
+    , mNextFreeIndex(0)
+  {
+    mJSONWriter.StartArrayElement();
+  }
+
+  // If you don't have access to a UniqueStrings, you had better not try and
+  // write a string element down the line!
+  explicit AutoArraySchemaWriter(SpliceableJSONWriter& aWriter)
+    : mJSONWriter(aWriter)
+    , mStrings(nullptr)
+    , mNextFreeIndex(0)
+  {
+    mJSONWriter.StartArrayElement();
+  }
+
+  ~AutoArraySchemaWriter() {
+    mJSONWriter.EndArray();
+  }
+
+  void FillUpTo(uint32_t aIndex) {
+    MOZ_ASSERT(aIndex >= mNextFreeIndex);
+    mJSONWriter.NullElements(aIndex - mNextFreeIndex);
+    mNextFreeIndex = aIndex + 1;
+  }
+
+  void IntElement(uint32_t aIndex, uint32_t aValue) {
+    FillUpTo(aIndex);
+    mJSONWriter.IntElement(aValue);
+  }
+
+  void DoubleElement(uint32_t aIndex, double aValue) {
+    FillUpTo(aIndex);
+    mJSONWriter.DoubleElement(aValue);
+  }
+
+  void StringElement(uint32_t aIndex, const char* aValue) {
+    MOZ_RELEASE_ASSERT(mStrings);
+    FillUpTo(aIndex);
+    mStrings->WriteElement(mJSONWriter, aValue);
+  }
+};
+
+class StreamOptimizationAttemptsOp : public JS::ForEachTrackedOptimizationAttemptOp
+{
+  SpliceableJSONWriter& mWriter;
+  UniqueJSONStrings& mUniqueStrings;
+
+public:
+  StreamOptimizationAttemptsOp(SpliceableJSONWriter& aWriter, UniqueJSONStrings& aUniqueStrings)
+    : mWriter(aWriter),
+      mUniqueStrings(aUniqueStrings)
+  { }
+
+  void operator()(JS::TrackedStrategy strategy, JS::TrackedOutcome outcome) override {
+    enum Schema : uint32_t {
+      STRATEGY = 0,
+      OUTCOME = 1
+    };
+
+    AutoArraySchemaWriter writer(mWriter, mUniqueStrings);
+    writer.StringElement(STRATEGY, JS::TrackedStrategyString(strategy));
+    writer.StringElement(OUTCOME, JS::TrackedOutcomeString(outcome));
+  }
+};
+
+class StreamJSFramesOp : public JS::ForEachProfiledFrameOp
+{
+  void* mReturnAddress;
+  UniqueStacks::Stack& mStack;
+  unsigned mDepth;
+
+public:
+  StreamJSFramesOp(void* aReturnAddr, UniqueStacks::Stack& aStack)
+   : mReturnAddress(aReturnAddr)
+   , mStack(aStack)
+   , mDepth(0)
+  { }
+
+  unsigned depth() const {
+    MOZ_ASSERT(mDepth > 0);
+    return mDepth;
+  }
+
+  void operator()(const JS::ForEachProfiledFrameOp::FrameHandle& aFrameHandle) override {
+    UniqueStacks::OnStackFrameKey frameKey(mReturnAddress, mDepth, aFrameHandle);
+    mStack.AppendFrame(frameKey);
+    mDepth++;
+  }
+};
+#endif
+
+uint32_t UniqueJSONStrings::GetOrAddIndex(const char* aStr)
+{
+  uint32_t index;
+  StringKey key(aStr);
+
+  auto it = mStringToIndexMap.find(key);
+
+  if (it != mStringToIndexMap.end()) {
+    return it->second;
+  }
+  index = mStringToIndexMap.size();
+  mStringToIndexMap[key] = index;
+  mStringTableWriter.StringElement(aStr);
+  return index;
+}
+
+bool UniqueStacks::FrameKey::operator==(const FrameKey& aOther) const
+{
+  return mLocation == aOther.mLocation &&
+         mLine == aOther.mLine &&
+         mCategory == aOther.mCategory &&
+         mJITAddress == aOther.mJITAddress &&
+         mJITDepth == aOther.mJITDepth;
+}
+
+bool UniqueStacks::StackKey::operator==(const StackKey& aOther) const
+{
+  MOZ_ASSERT_IF(mPrefix == aOther.mPrefix, mPrefixHash == aOther.mPrefixHash);
+  return mPrefix == aOther.mPrefix && mFrame == aOther.mFrame;
+}
+
+UniqueStacks::Stack::Stack(UniqueStacks& aUniqueStacks, const OnStackFrameKey& aRoot)
+ : mUniqueStacks(aUniqueStacks)
+ , mStack(aUniqueStacks.GetOrAddFrameIndex(aRoot))
+{
+}
+
+void UniqueStacks::Stack::AppendFrame(const OnStackFrameKey& aFrame)
+{
+  // Compute the prefix hash and index before mutating mStack.
+  uint32_t prefixHash = mStack.Hash();
+  uint32_t prefix = mUniqueStacks.GetOrAddStackIndex(mStack);
+  mStack.UpdateHash(prefixHash, prefix, mUniqueStacks.GetOrAddFrameIndex(aFrame));
+}
+
+uint32_t UniqueStacks::Stack::GetOrAddIndex() const
+{
+  return mUniqueStacks.GetOrAddStackIndex(mStack);
+}
+
+uint32_t UniqueStacks::FrameKey::Hash() const
+{
+  uint32_t hash = 0;
+  if (!mLocation.IsEmpty()) {
+#ifdef SPS_STANDALONE
+    hash = mozilla::HashString(mLocation.c_str());
+#else
+    hash = mozilla::HashString(mLocation.get());
+#endif
+  }
+  if (mLine.isSome()) {
+    hash = mozilla::AddToHash(hash, *mLine);
+  }
+  if (mCategory.isSome()) {
+    hash = mozilla::AddToHash(hash, *mCategory);
+  }
+  if (mJITAddress.isSome()) {
+    hash = mozilla::AddToHash(hash, *mJITAddress);
+    if (mJITDepth.isSome()) {
+      hash = mozilla::AddToHash(hash, *mJITDepth);
+    }
+  }
+  return hash;
+}
+
+uint32_t UniqueStacks::StackKey::Hash() const
+{
+  if (mPrefix.isNothing()) {
+    return mozilla::HashGeneric(mFrame);
+  }
+  return mozilla::AddToHash(*mPrefixHash, mFrame);
+}
+
+UniqueStacks::Stack UniqueStacks::BeginStack(const OnStackFrameKey& aRoot)
+{
+  return Stack(*this, aRoot);
+}
+
+UniqueStacks::UniqueStacks(JSContext* aContext)
+ : mContext(aContext)
+ , mFrameCount(0)
+{
+  mFrameTableWriter.StartBareList();
+  mStackTableWriter.StartBareList();
+}
+
+#ifdef SPS_STANDALONE
+uint32_t UniqueStacks::GetOrAddStackIndex(const StackKey& aStack)
+{
+  uint32_t index;
+  auto it = mStackToIndexMap.find(aStack);
+
+  if (it != mStackToIndexMap.end()) {
+    return it->second;
+  }
+
+  index = mStackToIndexMap.size();
+  mStackToIndexMap[aStack] = index;
+  StreamStack(aStack);
+  return index;
+}
+#else
+uint32_t UniqueStacks::GetOrAddStackIndex(const StackKey& aStack)
+{
+  uint32_t index;
+  if (mStackToIndexMap.Get(aStack, &index)) {
+    MOZ_ASSERT(index < mStackToIndexMap.Count());
+    return index;
+  }
+
+  index = mStackToIndexMap.Count();
+  mStackToIndexMap.Put(aStack, index);
+  StreamStack(aStack);
+  return index;
+}
+#endif
+
+#ifdef SPS_STANDALONE
+uint32_t UniqueStacks::GetOrAddFrameIndex(const OnStackFrameKey& aFrame)
+{
+  uint32_t index;
+  auto it = mFrameToIndexMap.find(aFrame);
+  if (it != mFrameToIndexMap.end()) {
+    MOZ_ASSERT(it->second < mFrameCount);
+    return it->second;
+  }
+
+  // A manual count is used instead of mFrameToIndexMap.Count() due to
+  // forwarding of canonical JIT frames above.
+  index = mFrameCount++;
+  mFrameToIndexMap[aFrame] = index;
+  StreamFrame(aFrame);
+  return index;
+}
+#else
+uint32_t UniqueStacks::GetOrAddFrameIndex(const OnStackFrameKey& aFrame)
+{
+  uint32_t index;
+  if (mFrameToIndexMap.Get(aFrame, &index)) {
+    MOZ_ASSERT(index < mFrameCount);
+    return index;
+  }
+
+  // If aFrame isn't canonical, forward it to the canonical frame's index.
+  if (aFrame.mJITFrameHandle) {
+    void* canonicalAddr = aFrame.mJITFrameHandle->canonicalAddress();
+    if (canonicalAddr != *aFrame.mJITAddress) {
+      OnStackFrameKey canonicalKey(canonicalAddr, *aFrame.mJITDepth, *aFrame.mJITFrameHandle);
+      uint32_t canonicalIndex = GetOrAddFrameIndex(canonicalKey);
+      mFrameToIndexMap.Put(aFrame, canonicalIndex);
+      return canonicalIndex;
+    }
+  }
+
+  // A manual count is used instead of mFrameToIndexMap.Count() due to
+  // forwarding of canonical JIT frames above.
+  index = mFrameCount++;
+  mFrameToIndexMap.Put(aFrame, index);
+  StreamFrame(aFrame);
+  return index;
+}
+#endif
+
+uint32_t UniqueStacks::LookupJITFrameDepth(void* aAddr)
+{
+  uint32_t depth;
+
+  auto it = mJITFrameDepthMap.find(aAddr);
+  if (it != mJITFrameDepthMap.end()) {
+    depth = it->second;
+    MOZ_ASSERT(depth > 0);
+    return depth;
+  }
+  return 0;
+}
+
+void UniqueStacks::AddJITFrameDepth(void* aAddr, unsigned depth)
+{
+  mJITFrameDepthMap[aAddr] = depth;
+}
+
+void UniqueStacks::SpliceFrameTableElements(SpliceableJSONWriter& aWriter)
+{
+  mFrameTableWriter.EndBareList();
+  aWriter.TakeAndSplice(mFrameTableWriter.WriteFunc());
+}
+
+void UniqueStacks::SpliceStackTableElements(SpliceableJSONWriter& aWriter)
+{
+  mStackTableWriter.EndBareList();
+  aWriter.TakeAndSplice(mStackTableWriter.WriteFunc());
+}
+
+void UniqueStacks::StreamStack(const StackKey& aStack)
+{
+  enum Schema : uint32_t {
+    PREFIX = 0,
+    FRAME = 1
+  };
+
+  AutoArraySchemaWriter writer(mStackTableWriter, mUniqueStrings);
+  if (aStack.mPrefix.isSome()) {
+    writer.IntElement(PREFIX, *aStack.mPrefix);
+  }
+  writer.IntElement(FRAME, aStack.mFrame);
+}
+
+void UniqueStacks::StreamFrame(const OnStackFrameKey& aFrame)
+{
+  enum Schema : uint32_t {
+    LOCATION = 0,
+    IMPLEMENTATION = 1,
+    OPTIMIZATIONS = 2,
+    LINE = 3,
+    CATEGORY = 4
+  };
+
+  AutoArraySchemaWriter writer(mFrameTableWriter, mUniqueStrings);
+
+#ifndef SPS_STANDALONE
+  if (!aFrame.mJITFrameHandle) {
+#else
+  {
+#endif
+#ifdef SPS_STANDALONE
+    writer.StringElement(LOCATION, aFrame.mLocation.c_str());
+#else
+    writer.StringElement(LOCATION, aFrame.mLocation.get());
+#endif
+    if (aFrame.mLine.isSome()) {
+      writer.IntElement(LINE, *aFrame.mLine);
+    }
+    if (aFrame.mCategory.isSome()) {
+      writer.IntElement(CATEGORY, *aFrame.mCategory);
+    }
+  }
+#ifndef SPS_STANDALONE
+  else {
+    const JS::ForEachProfiledFrameOp::FrameHandle& jitFrame = *aFrame.mJITFrameHandle;
+
+    writer.StringElement(LOCATION, jitFrame.label());
+
+    JS::ProfilingFrameIterator::FrameKind frameKind = jitFrame.frameKind();
+    MOZ_ASSERT(frameKind == JS::ProfilingFrameIterator::Frame_Ion ||
+               frameKind == JS::ProfilingFrameIterator::Frame_Baseline);
+    writer.StringElement(IMPLEMENTATION,
+                         frameKind == JS::ProfilingFrameIterator::Frame_Ion
+                         ? "ion"
+                         : "baseline");
+
+    if (jitFrame.hasTrackedOptimizations()) {
+      writer.FillUpTo(OPTIMIZATIONS);
+      mFrameTableWriter.StartObjectElement();
+      {
+        mFrameTableWriter.StartArrayProperty("types");
+        {
+          StreamOptimizationTypeInfoOp typeInfoOp(mFrameTableWriter, mUniqueStrings);
+          jitFrame.forEachOptimizationTypeInfo(typeInfoOp);
+        }
+        mFrameTableWriter.EndArray();
+
+        JS::Rooted<JSScript*> script(mContext);
+        jsbytecode* pc;
+        mFrameTableWriter.StartObjectProperty("attempts");
+        {
+          {
+            JSONSchemaWriter schema(mFrameTableWriter);
+            schema.WriteField("strategy");
+            schema.WriteField("outcome");
+          }
+
+          mFrameTableWriter.StartArrayProperty("data");
+          {
+            StreamOptimizationAttemptsOp attemptOp(mFrameTableWriter, mUniqueStrings);
+            jitFrame.forEachOptimizationAttempt(attemptOp, script.address(), &pc);
+          }
+          mFrameTableWriter.EndArray();
+        }
+        mFrameTableWriter.EndObject();
+
+        if (JSAtom* name = js::GetPropertyNameFromPC(script, pc)) {
+          char buf[512];
+          JS_PutEscapedFlatString(buf, mozilla::ArrayLength(buf), js::AtomToFlatString(name), 0);
+          mUniqueStrings.WriteProperty(mFrameTableWriter, "propertyName", buf);
+        }
+
+        unsigned line, column;
+        line = JS_PCToLineNumber(script, pc, &column);
+        mFrameTableWriter.IntProperty("line", line);
+        mFrameTableWriter.IntProperty("column", column);
+      }
+      mFrameTableWriter.EndObject();
+    }
+  }
+#endif
+}
+
+struct ProfileSample
+{
+  uint32_t mStack;
+  Maybe<double> mTime;
+  Maybe<double> mResponsiveness;
+  Maybe<double> mRSS;
+  Maybe<double> mUSS;
+  Maybe<int> mFrameNumber;
+  Maybe<double> mPower;
+};
+
+static void WriteSample(SpliceableJSONWriter& aWriter, ProfileSample& aSample)
+{
+  enum Schema : uint32_t {
+    STACK = 0,
+    TIME = 1,
+    RESPONSIVENESS = 2,
+    RSS = 3,
+    USS = 4,
+    FRAME_NUMBER = 5,
+    POWER = 6
+  };
+
+  AutoArraySchemaWriter writer(aWriter);
+
+  writer.IntElement(STACK, aSample.mStack);
+
+  if (aSample.mTime.isSome()) {
+    writer.DoubleElement(TIME, *aSample.mTime);
+  }
+
+  if (aSample.mResponsiveness.isSome()) {
+    writer.DoubleElement(RESPONSIVENESS, *aSample.mResponsiveness);
+  }
+
+  if (aSample.mRSS.isSome()) {
+    writer.DoubleElement(RSS, *aSample.mRSS);
+  }
+
+  if (aSample.mUSS.isSome()) {
+    writer.DoubleElement(USS, *aSample.mUSS);
+  }
+
+  if (aSample.mFrameNumber.isSome()) {
+    writer.IntElement(FRAME_NUMBER, *aSample.mFrameNumber);
+  }
+
+  if (aSample.mPower.isSome()) {
+    writer.DoubleElement(POWER, *aSample.mPower);
+  }
+}
+
+void ProfileBuffer::StreamSamplesToJSON(SpliceableJSONWriter& aWriter, int aThreadId,
+                                        double aSinceTime, JSContext* aContext,
+                                        UniqueStacks& aUniqueStacks)
+{
+  Maybe<ProfileSample> sample;
+  int readPos = mReadPos;
+  int currentThreadID = -1;
+  Maybe<double> currentTime;
+  UniquePtr<char[]> tagBuff = MakeUnique<char[]>(DYNAMIC_MAX_STRING);
+
+  while (readPos != mWritePos) {
+    ProfileEntry entry = mEntries[readPos];
+    if (entry.mTagName == 'T') {
+      currentThreadID = entry.mTagInt;
+      currentTime.reset();
+      int readAheadPos = (readPos + 1) % mEntrySize;
+      if (readAheadPos != mWritePos) {
+        ProfileEntry readAheadEntry = mEntries[readAheadPos];
+        if (readAheadEntry.mTagName == 't') {
+          currentTime = Some(readAheadEntry.mTagDouble);
+        }
+      }
+    }
+    if (currentThreadID == aThreadId && (currentTime.isNothing() || *currentTime >= aSinceTime)) {
+      switch (entry.mTagName) {
+      case 'r':
+        if (sample.isSome()) {
+          sample->mResponsiveness = Some(entry.mTagDouble);
+        }
+        break;
+      case 'p':
+        if (sample.isSome()) {
+          sample->mPower = Some(entry.mTagDouble);
+        }
+        break;
+      case 'R':
+        if (sample.isSome()) {
+          sample->mRSS = Some(entry.mTagDouble);
+        }
+        break;
+      case 'U':
+        if (sample.isSome()) {
+          sample->mUSS = Some(entry.mTagDouble);
+         }
+        break;
+      case 'f':
+        if (sample.isSome()) {
+          sample->mFrameNumber = Some(entry.mTagInt);
+        }
+        break;
+      case 's':
+        {
+          // end the previous sample if there was one
+          if (sample.isSome()) {
+            WriteSample(aWriter, *sample);
+            sample.reset();
+          }
+          // begin the next sample
+          sample.emplace();
+          sample->mTime = currentTime;
+
+          // Seek forward through the entire sample, looking for frames
+          // this is an easier approach to reason about than adding more
+          // control variables and cases to the loop that goes through the buffer once
+
+          UniqueStacks::Stack stack =
+            aUniqueStacks.BeginStack(UniqueStacks::OnStackFrameKey("(root)"));
+
+          int framePos = (readPos + 1) % mEntrySize;
+          ProfileEntry frame = mEntries[framePos];
+          while (framePos != mWritePos && frame.mTagName != 's' && frame.mTagName != 'T') {
+            int incBy = 1;
+            frame = mEntries[framePos];
+
+            // Read ahead to the next tag, if it's a 'd' tag process it now
+            const char* tagStringData = frame.mTagData;
+            int readAheadPos = (framePos + 1) % mEntrySize;
+            // Make sure the string is always null terminated if it fills up
+            // DYNAMIC_MAX_STRING-2
+            tagBuff[DYNAMIC_MAX_STRING-1] = '\0';
+
+            if (readAheadPos != mWritePos && mEntries[readAheadPos].mTagName == 'd') {
+              tagStringData = processDynamicTag(framePos, &incBy, tagBuff.get());
+            }
+
+            // Write one frame. It can have either
+            // 1. only location - 'l' containing a memory address
+            // 2. location and line number - 'c' followed by 'd's,
+            // an optional 'n' and an optional 'y'
+            // 3. a JIT return address - 'j' containing native code address
+            if (frame.mTagName == 'l') {
+              // Bug 753041
+              // We need a double cast here to tell GCC that we don't want to sign
+              // extend 32-bit addresses starting with 0xFXXXXXX.
+              unsigned long long pc = (unsigned long long)(uintptr_t)frame.mTagPtr;
+              snprintf(tagBuff.get(), DYNAMIC_MAX_STRING, "%#llx", pc);
+              stack.AppendFrame(UniqueStacks::OnStackFrameKey(tagBuff.get()));
+            } else if (frame.mTagName == 'c') {
+              UniqueStacks::OnStackFrameKey frameKey(tagStringData);
+              readAheadPos = (framePos + incBy) % mEntrySize;
+              if (readAheadPos != mWritePos &&
+                  mEntries[readAheadPos].mTagName == 'n') {
+                frameKey.mLine = Some((unsigned) mEntries[readAheadPos].mTagInt);
+                incBy++;
+              }
+              readAheadPos = (framePos + incBy) % mEntrySize;
+              if (readAheadPos != mWritePos &&
+                  mEntries[readAheadPos].mTagName == 'y') {
+                frameKey.mCategory = Some((unsigned) mEntries[readAheadPos].mTagInt);
+                incBy++;
+              }
+              stack.AppendFrame(frameKey);
+#ifndef SPS_STANDALONE
+            } else if (frame.mTagName == 'J') {
+              // A JIT frame may expand to multiple frames due to inlining.
+              void* pc = frame.mTagPtr;
+              unsigned depth = aUniqueStacks.LookupJITFrameDepth(pc);
+              if (depth == 0) {
+                StreamJSFramesOp framesOp(pc, stack);
+                JS::ForEachProfiledFrame(aContext, pc, framesOp);
+                aUniqueStacks.AddJITFrameDepth(pc, framesOp.depth());
+              } else {
+                for (unsigned i = 0; i < depth; i++) {
+                  UniqueStacks::OnStackFrameKey inlineFrameKey(pc, i);
+                  stack.AppendFrame(inlineFrameKey);
+                }
+              }
+#endif
+            }
+            framePos = (framePos + incBy) % mEntrySize;
+          }
+
+          sample->mStack = stack.GetOrAddIndex();
+          break;
+        }
+      }
+    }
+    readPos = (readPos + 1) % mEntrySize;
+  }
+  if (sample.isSome()) {
+    WriteSample(aWriter, *sample);
+  }
+}
+
+void ProfileBuffer::StreamMarkersToJSON(SpliceableJSONWriter& aWriter, int aThreadId,
+                                        double aSinceTime, UniqueStacks& aUniqueStacks)
+{
+  int readPos = mReadPos;
+  int currentThreadID = -1;
+  while (readPos != mWritePos) {
+    ProfileEntry entry = mEntries[readPos];
+    if (entry.mTagName == 'T') {
+      currentThreadID = entry.mTagInt;
+    } else if (currentThreadID == aThreadId && entry.mTagName == 'm') {
+      const ProfilerMarker* marker = entry.getMarker();
+      if (marker->GetTime() >= aSinceTime) {
+        entry.getMarker()->StreamJSON(aWriter, aUniqueStacks);
+      }
+    }
+    readPos = (readPos + 1) % mEntrySize;
+  }
+}
+
+int ProfileBuffer::FindLastSampleOfThread(int aThreadId)
+{
+  // We search backwards from mWritePos-1 to mReadPos.
+  // Adding mEntrySize makes the result of the modulus positive.
+  for (int readPos  = (mWritePos + mEntrySize - 1) % mEntrySize;
+           readPos !=  (mReadPos + mEntrySize - 1) % mEntrySize;
+           readPos  =   (readPos + mEntrySize - 1) % mEntrySize) {
+    ProfileEntry entry = mEntries[readPos];
+    if (entry.mTagName == 'T' && entry.mTagInt == aThreadId) {
+      return readPos;
+    }
+  }
+
+  return -1;
+}
+
+void ProfileBuffer::DuplicateLastSample(int aThreadId)
+{
+  int lastSampleStartPos = FindLastSampleOfThread(aThreadId);
+  if (lastSampleStartPos == -1) {
+    return;
+  }
+
+  MOZ_ASSERT(mEntries[lastSampleStartPos].mTagName == 'T');
+
+  addTag(mEntries[lastSampleStartPos]);
+
+  // Go through the whole entry and duplicate it, until we find the next one.
+  for (int readPos = (lastSampleStartPos + 1) % mEntrySize;
+       readPos != mWritePos;
+       readPos = (readPos + 1) % mEntrySize) {
+    switch (mEntries[readPos].mTagName) {
+      case 'T':
+        // We're done.
+        return;
+      case 't':
+        // Copy with new time
+        addTag(ProfileEntry('t', (mozilla::TimeStamp::Now() - sStartTime).ToMilliseconds()));
+        break;
+      case 'm':
+        // Don't copy markers
+        break;
+      // Copy anything else we don't know about
+      // L, B, S, c, s, d, l, f, h, r, t, p
+      default:
+        addTag(mEntries[readPos]);
+        break;
+    }
+  }
+}
+
+// END ProfileBuffer
+////////////////////////////////////////////////////////////////////////
+
+
+////////////////////////////////////////////////////////////////////////
+// BEGIN ThreadProfile
+
+// END ThreadProfile
+////////////////////////////////////////////////////////////////////////