Rewrite SamplingCircularQueue

src/circular-queue-inl.h

Index: src/circular-queue-inl.h
diff --git a/src/circular-queue-inl.h b/src/circular-queue-inl.h
index b48070ab5d24a064e4f8a91a72020e80d8f02954..4df8ac7d34c43c2790bea6969b4ebc2aeff22d7a 100644
--- a/src/circular-queue-inl.h
+++ b/src/circular-queue-inl.h
@@ -33,30 +33,60 @@
 namespace v8 {
 namespace internal {
 
+template<typename T, unsigned L>
+SamplingCircularQueue<T, L>::SamplingCircularQueue()
+    : enqueue_pos_(buffer_),
+      dequeue_pos_(buffer_) {
+}
+
+
+template<typename T, unsigned L>
+SamplingCircularQueue<T, L>::~SamplingCircularQueue() {
+}
+
+
+template<typename T, unsigned L>
+T* SamplingCircularQueue<T, L>::StartDequeue() {
+  MemoryBarrier();
+  if (NoBarrier_Load(&dequeue_pos_->marker) == kFull) {

[Benedikt Meurer, 2013/08/13 14:29:42]

Thinking about this again, we may need an Acquire_Load() to be safe in addition
to the MemoryBarrier() above.

[yurys, 2013/08/13 14:52:37]

Done.

+    return &dequeue_pos_->record;
+  }
+  return NULL;
+}
+
+
+template<typename T, unsigned L>
+void SamplingCircularQueue<T, L>::FinishDequeue() {
+  Release_Store(&dequeue_pos_->marker, kEmpty);
+  dequeue_pos_ = Next(dequeue_pos_);
+}
 
-void* SamplingCircularQueue::Enqueue() {
-  if (producer_pos_->enqueue_pos == producer_pos_->next_chunk_pos) {
-    if (producer_pos_->enqueue_pos == buffer_ + buffer_size_) {
-      producer_pos_->next_chunk_pos = buffer_;
-      producer_pos_->enqueue_pos = buffer_;
-    }
-    Acquire_Store(producer_pos_->next_chunk_pos, kEnqueueStarted);
-    // Skip marker.
-    producer_pos_->enqueue_pos += 1;
-    producer_pos_->next_chunk_pos += chunk_size_;
+
+template<typename T, unsigned L>
+T* SamplingCircularQueue<T, L>::StartEnqueue() {
+  MemoryBarrier();
+  if (NoBarrier_Load(&enqueue_pos_->marker) == kEmpty) {

[Benedikt Meurer, 2013/08/13 14:29:42]

Also use Acquire_Load() here to be sure.

[yurys, 2013/08/13 14:52:37]

Done.

+    return &enqueue_pos_->record;
   }
-  void* result = producer_pos_->enqueue_pos;
-  producer_pos_->enqueue_pos += record_size_;
-  return result;
+  return NULL;
 }
 
 
-void SamplingCircularQueue::WrapPositionIfNeeded(
-    SamplingCircularQueue::Cell** pos) {
-  if (*pos == buffer_ + buffer_size_) *pos = buffer_;
+template<typename T, unsigned L>
+void SamplingCircularQueue<T, L>::FinishEnqueue() {
+  Release_Store(&enqueue_pos_->marker, kFull);
+  enqueue_pos_ = Next(enqueue_pos_);
 }
 
 
+template<typename T, unsigned L>
+typename SamplingCircularQueue<T, L>::Entry* SamplingCircularQueue<T, L>::Next(
+    Entry* entry) {
+  Entry* next = entry + 1;
+  if (next == &buffer_[L]) return buffer_;
+  return next;
+}
+
 } }  // namespace v8::internal
 
 #endif  // V8_CIRCULAR_QUEUE_INL_H_