C++ ThreadProfile::bufferGeneration方法代码示例

static
void mergeStacksIntoProfile(ThreadProfile& aProfile, TickSample* aSample, NativeStack& aNativeStack)
{
  PseudoStack* pseudoStack = aProfile.GetPseudoStack();
  volatile StackEntry *pseudoFrames = pseudoStack->mStack;
  uint32_t pseudoCount = pseudoStack->stackSize();

  // Make a copy of the JS stack into a JSFrame array. This is necessary since,
  // like the native stack, the JS stack is iterated youngest-to-oldest and we
  // need to iterate oldest-to-youngest when adding entries to aProfile.

  // Synchronous sampling reports an invalid buffer generation to
  // ProfilingFrameIterator to avoid incorrectly resetting the generation of
  // sampled JIT entries inside the JS engine. See note below concerning 'J'
  // entries.
  uint32_t startBufferGen;
  if (aSample->isSamplingCurrentThread) {
    startBufferGen = UINT32_MAX;
  } else {
    startBufferGen = aProfile.bufferGeneration();
  }
  uint32_t jsCount = 0;
#ifndef SPS_STANDALONE
  JS::ProfilingFrameIterator::Frame jsFrames[1000];
  // Only walk jit stack if profiling frame iterator is turned on.
  if (pseudoStack->mRuntime && JS::IsProfilingEnabledForRuntime(pseudoStack->mRuntime)) {
    AutoWalkJSStack autoWalkJSStack;
    const uint32_t maxFrames = mozilla::ArrayLength(jsFrames);

    if (aSample && autoWalkJSStack.walkAllowed) {
      JS::ProfilingFrameIterator::RegisterState registerState;
      registerState.pc = aSample->pc;
      registerState.sp = aSample->sp;
#ifdef ENABLE_ARM_LR_SAVING
      registerState.lr = aSample->lr;
#endif

      JS::ProfilingFrameIterator jsIter(pseudoStack->mRuntime,
                                        registerState,
                                        startBufferGen);
      for (; jsCount < maxFrames && !jsIter.done(); ++jsIter) {
        // See note below regarding 'J' entries.
        if (aSample->isSamplingCurrentThread || jsIter.isAsmJS()) {
          uint32_t extracted = jsIter.extractStack(jsFrames, jsCount, maxFrames);
          jsCount += extracted;
          if (jsCount == maxFrames)
            break;
        } else {
          mozilla::Maybe<JS::ProfilingFrameIterator::Frame> frame =
            jsIter.getPhysicalFrameWithoutLabel();
          if (frame.isSome())
            jsFrames[jsCount++] = frame.value();
        }
      }
    }
  }
#endif

  // Start the sample with a root entry.
  aProfile.addTag(ProfileEntry('s', "(root)"));

  // While the pseudo-stack array is ordered oldest-to-youngest, the JS and
  // native arrays are ordered youngest-to-oldest. We must add frames to
  // aProfile oldest-to-youngest. Thus, iterate over the pseudo-stack forwards
  // and JS and native arrays backwards. Note: this means the terminating
  // condition jsIndex and nativeIndex is being < 0.
  uint32_t pseudoIndex = 0;
  int32_t jsIndex = jsCount - 1;
  int32_t nativeIndex = aNativeStack.count - 1;

  uint8_t *lastPseudoCppStackAddr = nullptr;

  // Iterate as long as there is at least one frame remaining.
  while (pseudoIndex != pseudoCount || jsIndex >= 0 || nativeIndex >= 0) {
    // There are 1 to 3 frames available. Find and add the oldest.

    uint8_t *pseudoStackAddr = nullptr;
    uint8_t *jsStackAddr = nullptr;
    uint8_t *nativeStackAddr = nullptr;

    if (pseudoIndex != pseudoCount) {
      volatile StackEntry &pseudoFrame = pseudoFrames[pseudoIndex];

      if (pseudoFrame.isCpp())
        lastPseudoCppStackAddr = (uint8_t *) pseudoFrame.stackAddress();

#ifndef SPS_STANDALONE
      // Skip any pseudo-stack JS frames which are marked isOSR
      // Pseudostack frames are marked isOSR when the JS interpreter
      // enters a jit frame on a loop edge (via on-stack-replacement,
      // or OSR).  To avoid both the pseudoframe and jit frame being
      // recorded (and showing up twice), the interpreter marks the
      // interpreter pseudostack entry with the OSR flag to ensure that
      // it doesn't get counted.
      if (pseudoFrame.isJs() && pseudoFrame.isOSR()) {
          pseudoIndex++;
          continue;
      }
#endif

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