Fix edge case where profiler would miss the caller of the top frame

runtime/vm/profiler.h

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_PROFILER_H_
 #define VM_PROFILER_H_
 
 #include "vm/allocation.h"
 #include "vm/code_observers.h"
 #include "vm/globals.h"
@@ skipping 101 matching lines @@
 // The maximum number of stack frames a sample can hold.
 #define kSampleFramesSize 256
 
 // Each Sample holds a stack trace from an isolate.
 class Sample {
  public:
   void Init(Isolate* isolate, int64_t timestamp, ThreadId tid) {
     timestamp_ = timestamp;
     tid_ = tid;
     isolate_ = isolate;
+    pc_marker_ = 0;
     vm_tag_ = VMTag::kInvalidTagId;
     user_tag_ = UserTags::kNoUserTag;
+    sp_ = 0;
+    fp_ = 0;
+    state_ = 0;
     for (intptr_t i = 0; i < kSampleFramesSize; i++) {
       pcs_[i] = 0;
     }
   }
 
   // Isolate sample was taken from.
   Isolate* isolate() const {
     return isolate_;
   }
 
@@ skipping 24 matching lines @@
     vm_tag_ = tag;
   }
 
   uword user_tag() const {
     return user_tag_;
   }
   void set_user_tag(uword tag) {
     user_tag_ = tag;
   }
 
+  uword pc_marker() const {
+    return pc_marker_;
+  }
+
+  void set_pc_marker(uword pc_marker) {
+    pc_marker_ = pc_marker;
+  }
+
+  uword sp() {
+    return sp_;
+  }
+
+  void set_sp(uword sp) {
+    sp_ = sp;
+  }
+
+  uword fp() {
+    return fp_;
+  }
+
+  void set_fp(uword fp) {
+    fp_ = fp;
+  }
+
+  void InsertCallerForTopFrame(uword pc) {
+    // Shift all entries down.
+    for (intptr_t i = 1; i < kSampleFramesSize - 1; i++) {
+      pcs_[i + 1] = pcs_[i];
+    }
+    pcs_[1] = pc;
+  }
+
+  bool processed() const {
+    return ProcessedBit::decode(state_);
+  }
+
+  void set_processed(bool processed) {
+    state_ = ProcessedBit::update(processed, state_);
+  }
+
+  bool leaf_frame_is_dart() const {
+    return LeafFrameIsDart::decode(state_);
+  }
+
+  void set_leaf_frame_is_dart(bool leaf_frame_is_dart) {
+    state_ = LeafFrameIsDart::update(leaf_frame_is_dart, state_);
+  }
+
  private:
+  class ProcessedBit : public BitField<bool, 0, 1> {};
+  class LeafFrameIsDart : public BitField<bool, 1, 1> {};
   int64_t timestamp_;
   ThreadId tid_;
   Isolate* isolate_;
+  uword pc_marker_;
   uword vm_tag_;
   uword user_tag_;
+  uword sp_;
+  uword fp_;
+  uword state_;
   uword pcs_[kSampleFramesSize];
 };
 
 
 // Ring buffer of Samples that is (usually) shared by many isolates.
 class SampleBuffer {
  public:
   static const intptr_t kDefaultBufferCapacity = 120000;  // 2 minutes @ 1000hz.
 
   explicit SampleBuffer(intptr_t capacity = kDefaultBufferCapacity) {
@@ skipping 14 matching lines @@
   intptr_t capacity() const { return capacity_; }
 
   Sample* ReserveSample();
 
   Sample* At(intptr_t idx) const {
     ASSERT(idx >= 0);
     ASSERT(idx < capacity_);
     return &samples_[idx];
   }
 
   void VisitSamples(SampleVisitor* visitor) {

[srdjan, 2014/05/02 18:20:29]

Remove one of VisitSamples/VisitSamplesByReference

[Cutch, 2014/05/02 18:37:03]

Done.

     ASSERT(visitor != NULL);
     Sample sample;
     const intptr_t length = capacity();
     for (intptr_t i = 0; i < length; i++) {
       // Copy the sample.
       sample = *At(i);
       if (sample.isolate() != visitor->isolate()) {
         // Another isolate.
         continue;
       }
       if (sample.timestamp() == 0) {
         // Empty.
         continue;
       }
       if (sample.At(0) == 0) {
         // No frames.
         continue;
       }
       visitor->IncrementVisited();
       visitor->VisitSample(&sample);
     }
   }
 
+  void VisitSamplesByReference(SampleVisitor* visitor) {
+    ASSERT(visitor != NULL);
+    Sample* sample;
+    const intptr_t length = capacity();
+    for (intptr_t i = 0; i < length; i++) {
+      sample = At(i);

[srdjan, 2014/05/02 18:20:29]

You can put Sample* sample = At(i); here.
OR
const Sample& sample = *At(i)l

[Cutch, 2014/05/02 18:37:03]

Done.

+      if (sample->isolate() != visitor->isolate()) {
+        // Another isolate.
+        continue;
+      }
+      if (sample->timestamp() == 0) {
+        // Empty.
+        continue;
+      }
+      if (sample->At(0) == 0) {
+        // No frames.
+        continue;
+      }
+      visitor->IncrementVisited();
+      visitor->VisitSample(sample);
+    }
+  }
+
  private:
   Sample* samples_;
   intptr_t capacity_;
   uintptr_t cursor_;
 
   DISALLOW_COPY_AND_ASSIGN(SampleBuffer);
 };
 
 
 }  // namespace dart
 
 #endif  // VM_PROFILER_H_