Move stack trace extraction code out of TickSample::Init

src/profiler/tick-sample.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/profiler/tick-sample.h"
 
 #include "src/frames-inl.h"
 #include "src/vm-state-inl.h"
 
 
 namespace v8 {
 namespace internal {
 
 namespace {
 
 bool IsSamePage(byte* ptr1, byte* ptr2) {
   const uint32_t kPageSize = 4096;
   uintptr_t mask = ~static_cast<uintptr_t>(kPageSize - 1);
   return (reinterpret_cast<uintptr_t>(ptr1) & mask) ==
          (reinterpret_cast<uintptr_t>(ptr2) & mask);
 }
 
-
 // Check if the code at specified address could potentially be a
 // frame setup code.
 bool IsNoFrameRegion(Address address) {
   struct Pattern {
     int bytes_count;
     byte bytes[8];
     int offsets[4];
   };
   byte* pc = reinterpret_cast<byte*>(address);
   static Pattern patterns[] = {
@@ skipping 36 matching lines @@
         if (!memcmp(pc, pattern->bytes + offset, pattern->bytes_count - offset))
           return true;
       }
     }
   }
   return false;
 }
 
 }  // namespace
 
-
 //
 // StackTracer implementation
 //
 DISABLE_ASAN void TickSample::Init(Isolate* isolate,
                                    const v8::RegisterState& regs,
                                    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;
+  SampleInfo info;
+  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 = nullptr;
+  }
+}
+
+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();
+  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 (pc && IsNoFrameRegion(pc)) {
-    // Can't collect stack. Mark the sample as spoiled.
-    timestamp = base::TimeTicks();
-    pc = 0;
-    return;
+  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) {
-    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;
+    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);
-  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) {
-    // It is executing JS but failed to collect a stack trace.
-    // Mark the sample as spoiled.
-    timestamp = base::TimeTicks();
-    pc = 0;
-  }
-}
-
-
-void 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;
-
-  Address js_entry_sp = isolate->js_entry_sp();
-  if (js_entry_sp == 0) return;  // Not executing JS now.
-
-  SafeStackFrameIterator it(isolate, reinterpret_cast<Address>(regs.fp),
-                            reinterpret_cast<Address>(regs.sp), js_entry_sp);
   size_t i = 0;
   if (record_c_entry_frame == kIncludeCEntryFrame && !it.done() &&
       it.top_frame_type() == StackFrame::EXIT) {
     frames[i++] = isolate->c_function();
   }
   while (!it.done() && i < frames_limit) {
     if (it.frame()->is_interpreted()) {
       // For interpreted frames use the bytecode array pointer as the pc.
       InterpretedFrame* frame = static_cast<InterpretedFrame*>(it.frame());
       // Since the sampler can interrupt execution at any point the
       // bytecode_array might be garbage, so don't dereference it.
       Address bytecode_array =
           reinterpret_cast<Address>(frame->GetBytecodeArray()) - kHeapObjectTag;
       frames[i++] = bytecode_array + BytecodeArray::kHeaderSize +
                     frame->GetBytecodeOffset();
     } else {
       frames[i++] = it.frame()->pc();
     }
     it.Advance();
   }
   sample_info->frames_count = i;
+  return true;
 }
 
-
 #if defined(USE_SIMULATOR)
 bool SimulatorHelper::FillRegisters(Isolate* isolate,
                                     v8::RegisterState* state) {
   Simulator *simulator = isolate->thread_local_top()->simulator_;
   // Check if there is active simulator.
   if (simulator == NULL) return false;
 #if V8_TARGET_ARCH_ARM
   if (!simulator->has_bad_pc()) {
     state->pc = reinterpret_cast<Address>(simulator->get_pc());
   }
@@ skipping 36 matching lines @@
     // it is not guaranteed to be atomic even when both host and target
     // are of same bitness.
     return false;
   }
   return true;
 }
 #endif  // USE_SIMULATOR
 
 }  // namespace internal
 }  // namespace v8