Move stack trace extraction code out of TickSample::Init

src/profiler/tick-sample.cc

Index: src/profiler/tick-sample.cc
diff --git a/src/profiler/tick-sample.cc b/src/profiler/tick-sample.cc
index 3edd964c86d56bd8ec881007050241d7fbb3b632..4b481325fa64734fa818b85b158f44ee6a123cd4 100644
--- a/src/profiler/tick-sample.cc
+++ b/src/profiler/tick-sample.cc
@@ -20,7 +20,6 @@ bool IsSamePage(byte* ptr1, byte* ptr2) {
          (reinterpret_cast<uintptr_t>(ptr2) & mask);
 }
 
-
 // Check if the code at specified address could potentially be a
 // frame setup code.
 bool IsNoFrameRegion(Address address) {
@@ -77,7 +76,6 @@ bool IsNoFrameRegion(Address address) {
 
 }  // namespace
 
-
 //
 // StackTracer implementation
 //
@@ -86,68 +84,63 @@ DISABLE_ASAN void TickSample::Init(Isolate* isolate,
                                    RecordCEntryFrame record_c_entry_frame,
                                    bool update_stats) {
   timestamp = base::TimeTicks::HighResolutionNow();
-  pc = reinterpret_cast<Address>(regs.pc);
-  state = isolate->current_vm_state();
   this->update_stats = update_stats;
 
-  // Avoid collecting traces while doing GC.
-  if (state == GC) return;
-
-  Address js_entry_sp = isolate->js_entry_sp();
-  if (js_entry_sp == 0) return;  // Not executing JS now.
-
-  if (pc && IsNoFrameRegion(pc)) {
-    // Can't collect stack. Mark the sample as spoiled.
-    timestamp = base::TimeTicks();
-    pc = 0;
-    return;
-  }
-
-  ExternalCallbackScope* scope = isolate->external_callback_scope();
-  Address handler = Isolate::handler(isolate->thread_local_top());
-  // If there is a handler on top of the external callback scope then
-  // we have already entrered JavaScript again and the external callback
-  // is not the top function.
-  if (scope && scope->scope_address() < handler) {
-    external_callback_entry = *scope->callback_entrypoint_address();
-    has_external_callback = true;
-  } else {
-    // sp register may point at an arbitrary place in memory, make
-    // sure MSAN doesn't complain about it.
-    MSAN_MEMORY_IS_INITIALIZED(regs.sp, sizeof(Address));
-    // Sample potential return address value for frameless invocation of
-    // stubs (we'll figure out later, if this value makes sense).
-    tos = Memory::Address_at(reinterpret_cast<Address>(regs.sp));
-    has_external_callback = false;
-  }
-
-  SafeStackFrameIterator it(isolate, reinterpret_cast<Address>(regs.fp),
-                            reinterpret_cast<Address>(regs.sp), js_entry_sp);
-  top_frame_type = it.top_frame_type();
-
   SampleInfo info;
-  GetStackSample(isolate, regs, record_c_entry_frame,
-                 reinterpret_cast<void**>(&stack[0]), kMaxFramesCount, &info);
-  frames_count = static_cast<unsigned>(info.frames_count);
-  if (!frames_count) {
+  if (GetStackSample(isolate, regs, record_c_entry_frame,
+                     reinterpret_cast<void**>(&stack[0]), kMaxFramesCount,
+                     &info)) {
+    state = info.vm_state;
+    pc = static_cast<Address>(regs.pc);
+    frames_count = static_cast<unsigned>(info.frames_count);
+    has_external_callback = info.external_callback_entry != nullptr;
+    if (has_external_callback) {
+      external_callback_entry =
+          static_cast<Address>(info.external_callback_entry);
+    } else if (frames_count) {
+      // sp register may point at an arbitrary place in memory, make
+      // sure MSAN doesn't complain about it.
+      MSAN_MEMORY_IS_INITIALIZED(regs.sp, sizeof(Address));
+      // Sample potential return address value for frameless invocation of
+      // stubs (we'll figure out later, if this value makes sense).
+      tos = Memory::Address_at(reinterpret_cast<Address>(regs.sp));
+    } else {
+      tos = nullptr;
+    }
+  } else {
     // It is executing JS but failed to collect a stack trace.
     // Mark the sample as spoiled.
     timestamp = base::TimeTicks();
-    pc = 0;
+    pc = nullptr;
   }
 }
 
-
-void TickSample::GetStackSample(Isolate* isolate, const v8::RegisterState& regs,
+bool TickSample::GetStackSample(Isolate* isolate, const v8::RegisterState& regs,
                                 RecordCEntryFrame record_c_entry_frame,
                                 void** frames, size_t frames_limit,
                                 v8::SampleInfo* sample_info) {
   sample_info->frames_count = 0;
   sample_info->vm_state = isolate->current_vm_state();
-  if (sample_info->vm_state == GC) return;
+  sample_info->external_callback_entry = nullptr;
+  if (sample_info->vm_state == GC) return true;
 
   Address js_entry_sp = isolate->js_entry_sp();
-  if (js_entry_sp == 0) return;  // Not executing JS now.
+  if (js_entry_sp == 0) return true;  // Not executing JS now.
+
+  if (regs.pc && IsNoFrameRegion(static_cast<Address>(regs.pc))) {
+    // Can't collect stack.
+    return false;
+  }
+
+  ExternalCallbackScope* scope = isolate->external_callback_scope();
+  Address handler = Isolate::handler(isolate->thread_local_top());
+  // If there is a handler on top of the external callback scope then
+  // we have already entrered JavaScript again and the external callback
+  // is not the top function.
+  if (scope && scope->scope_address() < handler) {
+    sample_info->external_callback_entry =
+        *scope->callback_entrypoint_address();
+  }
 
   SafeStackFrameIterator it(isolate, reinterpret_cast<Address>(regs.fp),
                             reinterpret_cast<Address>(regs.sp), js_entry_sp);
@@ -172,9 +165,9 @@ void TickSample::GetStackSample(Isolate* isolate, const v8::RegisterState& regs,
     it.Advance();
   }
   sample_info->frames_count = i;
+  return true;
 }
 
-
 #if defined(USE_SIMULATOR)
 bool SimulatorHelper::FillRegisters(Isolate* isolate,
                                     v8::RegisterState* state) {