Split TickSample and Sampler.

Since we are going to move Sampler as library, we creates tick-sample.[h|cc] for
TickSample, in order to maintain legacy code.

BUG=v8:4994
LOG=n

Review-Url: https://codereview.chromium.org/1952393002
Cr-Commit-Position: refs/heads/master@{#36267}

BUILD.gn

@@ -1350,6 +1350,8 @@ v8_source_set("v8_base") {
     "src/profiler/sampling-heap-profiler.h",
     "src/profiler/strings-storage.cc",
     "src/profiler/strings-storage.h",
+    "src/profiler/tick-sample.cc",
+    "src/profiler/tick-sample.h",
     "src/profiler/unbound-queue-inl.h",
     "src/profiler/unbound-queue.h",
     "src/property-descriptor.cc",

src/api.cc

@@ -48,7 +48,7 @@
 #include "src/profiler/heap-profiler.h"
 #include "src/profiler/heap-snapshot-generator-inl.h"
 #include "src/profiler/profile-generator-inl.h"
-#include "src/profiler/sampler.h"
+#include "src/profiler/tick-sample.h"
 #include "src/property-descriptor.h"
 #include "src/property-details.h"
 #include "src/property.h"

src/profiler/cpu-profiler.h

@@ -13,6 +13,7 @@
 #include "src/locked-queue.h"
 #include "src/profiler/circular-queue.h"
 #include "src/profiler/sampler.h"
+#include "src/profiler/tick-sample.h"
 
 namespace v8 {
 namespace internal {

src/profiler/profile-generator.cc

@@ -10,7 +10,7 @@
 #include "src/deoptimizer.h"
 #include "src/global-handles.h"
 #include "src/profiler/profile-generator-inl.h"
-#include "src/profiler/sampler.h"
+#include "src/profiler/tick-sample.h"
 #include "src/splay-tree-inl.h"
 #include "src/unicode.h"
 

src/profiler/sampler.cc

@@ -44,13 +44,10 @@
 
 #include "src/base/atomic-utils.h"
 #include "src/base/platform/platform.h"
-#include "src/flags.h"
-#include "src/frames-inl.h"
-#include "src/log.h"
 #include "src/profiler/cpu-profiler-inl.h"
+#include "src/profiler/tick-sample.h"
 #include "src/simulator.h"
 #include "src/v8threads.h"
-#include "src/vm-state-inl.h"
 
 
 #if V8_OS_ANDROID && !defined(__BIONIC_HAVE_UCONTEXT_T)
@@ -175,68 +172,6 @@ class PlatformDataCommon : public Malloced {
 };
 
 
-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[] = {
-#if V8_HOST_ARCH_IA32
-    // push %ebp
-    // mov %esp,%ebp
-    {3, {0x55, 0x89, 0xe5}, {0, 1, -1}},
-    // pop %ebp
-    // ret N
-    {2, {0x5d, 0xc2}, {0, 1, -1}},
-    // pop %ebp
-    // ret
-    {2, {0x5d, 0xc3}, {0, 1, -1}},
-#elif V8_HOST_ARCH_X64
-    // pushq %rbp
-    // movq %rsp,%rbp
-    {4, {0x55, 0x48, 0x89, 0xe5}, {0, 1, -1}},
-    // popq %rbp
-    // ret N
-    {2, {0x5d, 0xc2}, {0, 1, -1}},
-    // popq %rbp
-    // ret
-    {2, {0x5d, 0xc3}, {0, 1, -1}},
-#endif
-    {0, {}, {}}
-  };
-  for (Pattern* pattern = patterns; pattern->bytes_count; ++pattern) {
-    for (int* offset_ptr = pattern->offsets; *offset_ptr != -1; ++offset_ptr) {
-      int offset = *offset_ptr;
-      if (!offset || IsSamePage(pc, pc - offset)) {
-        MSAN_MEMORY_IS_INITIALIZED(pc - offset, pattern->bytes_count);
-        if (!memcmp(pc - offset, pattern->bytes, pattern->bytes_count))
-          return true;
-      } else {
-        // It is not safe to examine bytes on another page as it might not be
-        // allocated thus causing a SEGFAULT.
-        // Check the pattern part that's on the same page and
-        // pessimistically assume it could be the entire pattern match.
-        MSAN_MEMORY_IS_INITIALIZED(pc, pattern->bytes_count - offset);
-        if (!memcmp(pc, pattern->bytes + offset, pattern->bytes_count - offset))
-          return true;
-      }
-    }
-  }
-  return false;
-}
-
 typedef List<Sampler*> SamplerList;
 
 #if defined(USE_SIGNALS)
@@ -331,61 +266,6 @@ class Sampler::PlatformData : public PlatformDataCommon {
 #endif
 
 
-#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());
-  }
-  state->sp = reinterpret_cast<Address>(simulator->get_register(Simulator::sp));
-  state->fp = reinterpret_cast<Address>(simulator->get_register(
-      Simulator::r11));
-#elif V8_TARGET_ARCH_ARM64
-  state->pc = reinterpret_cast<Address>(simulator->pc());
-  state->sp = reinterpret_cast<Address>(simulator->sp());
-  state->fp = reinterpret_cast<Address>(simulator->fp());
-#elif V8_TARGET_ARCH_MIPS || V8_TARGET_ARCH_MIPS64
-  if (!simulator->has_bad_pc()) {
-    state->pc = reinterpret_cast<Address>(simulator->get_pc());
-  }
-  state->sp = reinterpret_cast<Address>(simulator->get_register(Simulator::sp));
-  state->fp = reinterpret_cast<Address>(simulator->get_register(Simulator::fp));
-#elif V8_TARGET_ARCH_PPC
-  if (!simulator->has_bad_pc()) {
-    state->pc = reinterpret_cast<Address>(simulator->get_pc());
-  }
-  state->sp = reinterpret_cast<Address>(simulator->get_register(Simulator::sp));
-  state->fp = reinterpret_cast<Address>(simulator->get_register(Simulator::fp));
-#elif V8_TARGET_ARCH_S390
-  if (!simulator->has_bad_pc()) {
-    state->pc = reinterpret_cast<Address>(simulator->get_pc());
-  }
-  state->sp = reinterpret_cast<Address>(simulator->get_register(Simulator::sp));
-  state->fp = reinterpret_cast<Address>(simulator->get_register(Simulator::fp));
-#endif
-  if (state->sp == 0 || state->fp == 0) {
-    // It possible that the simulator is interrupted while it is updating
-    // the sp or fp register. ARM64 simulator does this in two steps:
-    // first setting it to zero and then setting it to the new value.
-    // Bailout if sp/fp doesn't contain the new value.
-    //
-    // FIXME: The above doesn't really solve the issue.
-    // If a 64-bit target is executed on a 32-bit host even the final
-    // write is non-atomic, so it might obtain a half of the result.
-    // Moreover as long as the register set code uses memcpy (as of now),
-    // it is not guaranteed to be atomic even when both host and target
-    // are of same bitness.
-    return false;
-  }
-  return true;
-}
-#endif  // USE_SIMULATOR
-
-
 #if defined(USE_SIGNALS)
 
 class SignalHandler : public AllStatic {
@@ -811,103 +691,6 @@ void SignalHandler::HandleProfilerSignal(int signal, siginfo_t* info,
 #endif  // USE_SIGNALs
 
 
-//
-// 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;
-
-  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) {
-    // 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;
-}
-
-
 void Sampler::SetUp() {
 #if defined(USE_SIGNALS)
   SignalHandler::SetUp();

src/profiler/sampler.h

@@ -8,14 +8,13 @@
 #include "include/v8.h"
 
 #include "src/base/atomicops.h"
-#include "src/base/platform/time.h"
+#include "src/base/macros.h"
-#include "src/frames.h"
-#include "src/globals.h"
 
 namespace v8 {
 namespace internal {
 
 class Isolate;
+struct TickSample;
 
 // ----------------------------------------------------------------------------
 // Sampler
@@ -24,43 +23,6 @@ class Isolate;
 // (if used for profiling) the program counter and stack pointer for
 // the thread that created it.
 
-// TickSample captures the information collected for each sample.
-struct TickSample {
-  // Internal profiling (with --prof + tools/$OS-tick-processor) wants to
-  // include the runtime function we're calling. Externally exposed tick
-  // samples don't care.
-  enum RecordCEntryFrame { kIncludeCEntryFrame, kSkipCEntryFrame };
-
-  TickSample()
-      : state(OTHER),
-        pc(NULL),
-        external_callback_entry(NULL),
-        frames_count(0),
-        has_external_callback(false),
-        update_stats(true),
-        top_frame_type(StackFrame::NONE) {}
-  void Init(Isolate* isolate, const v8::RegisterState& state,
-            RecordCEntryFrame record_c_entry_frame, bool update_stats);
-  static void GetStackSample(Isolate* isolate, const v8::RegisterState& state,
-                             RecordCEntryFrame record_c_entry_frame,
-                             void** frames, size_t frames_limit,
-                             v8::SampleInfo* sample_info);
-  StateTag state;  // The state of the VM.
-  Address pc;      // Instruction pointer.
-  union {
-    Address tos;   // Top stack value (*sp).
-    Address external_callback_entry;
-  };
-  static const unsigned kMaxFramesCountLog2 = 8;
-  static const unsigned kMaxFramesCount = (1 << kMaxFramesCountLog2) - 1;
-  Address stack[kMaxFramesCount];  // Call stack.
-  base::TimeTicks timestamp;
-  unsigned frames_count : kMaxFramesCountLog2;  // Number of captured frames.
-  bool has_external_callback : 1;
-  bool update_stats : 1;  // Whether the sample should update aggregated stats.
-  StackFrame::Type top_frame_type : 5;
-};
-
 class Sampler {
  public:
   // Initializes the Sampler support. Called once at VM startup.
@@ -140,17 +102,6 @@ class Sampler {
   DISALLOW_IMPLICIT_CONSTRUCTORS(Sampler);
 };
 
-
-#if defined(USE_SIMULATOR)
-class SimulatorHelper : AllStatic {
- public:
-  // Returns true if register values were successfully retrieved
-  // from the simulator, otherwise returns false.
-  static bool FillRegisters(Isolate* isolate, v8::RegisterState* state);
-};
-#endif  // USE_SIMULATOR
-
-
 }  // namespace internal
 }  // namespace v8
 

src/profiler/tick-sample.cc

@@ -0,0 +1,233 @@
+// 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[] = {
+#if V8_HOST_ARCH_IA32
+    // push %ebp
+    // mov %esp,%ebp
+    {3, {0x55, 0x89, 0xe5}, {0, 1, -1}},
+    // pop %ebp
+    // ret N
+    {2, {0x5d, 0xc2}, {0, 1, -1}},
+    // pop %ebp
+    // ret
+    {2, {0x5d, 0xc3}, {0, 1, -1}},
+#elif V8_HOST_ARCH_X64
+    // pushq %rbp
+    // movq %rsp,%rbp
+    {4, {0x55, 0x48, 0x89, 0xe5}, {0, 1, -1}},
+    // popq %rbp
+    // ret N
+    {2, {0x5d, 0xc2}, {0, 1, -1}},
+    // popq %rbp
+    // ret
+    {2, {0x5d, 0xc3}, {0, 1, -1}},
+#endif
+    {0, {}, {}}
+  };
+  for (Pattern* pattern = patterns; pattern->bytes_count; ++pattern) {
+    for (int* offset_ptr = pattern->offsets; *offset_ptr != -1; ++offset_ptr) {
+      int offset = *offset_ptr;
+      if (!offset || IsSamePage(pc, pc - offset)) {
+        MSAN_MEMORY_IS_INITIALIZED(pc - offset, pattern->bytes_count);
+        if (!memcmp(pc - offset, pattern->bytes, pattern->bytes_count))
+          return true;
+      } else {
+        // It is not safe to examine bytes on another page as it might not be
+        // allocated thus causing a SEGFAULT.
+        // Check the pattern part that's on the same page and
+        // pessimistically assume it could be the entire pattern match.
+        MSAN_MEMORY_IS_INITIALIZED(pc, pattern->bytes_count - offset);
+        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;
+
+  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) {
+    // 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;
+}
+
+
+#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());
+  }
+  state->sp = reinterpret_cast<Address>(simulator->get_register(Simulator::sp));
+  state->fp = reinterpret_cast<Address>(simulator->get_register(
+      Simulator::r11));
+#elif V8_TARGET_ARCH_ARM64
+  state->pc = reinterpret_cast<Address>(simulator->pc());
+  state->sp = reinterpret_cast<Address>(simulator->sp());
+  state->fp = reinterpret_cast<Address>(simulator->fp());
+#elif V8_TARGET_ARCH_MIPS || V8_TARGET_ARCH_MIPS64
+  if (!simulator->has_bad_pc()) {
+    state->pc = reinterpret_cast<Address>(simulator->get_pc());
+  }
+  state->sp = reinterpret_cast<Address>(simulator->get_register(Simulator::sp));
+  state->fp = reinterpret_cast<Address>(simulator->get_register(Simulator::fp));
+#elif V8_TARGET_ARCH_PPC
+  if (!simulator->has_bad_pc()) {
+    state->pc = reinterpret_cast<Address>(simulator->get_pc());
+  }
+  state->sp = reinterpret_cast<Address>(simulator->get_register(Simulator::sp));
+  state->fp = reinterpret_cast<Address>(simulator->get_register(Simulator::fp));
+#elif V8_TARGET_ARCH_S390
+  if (!simulator->has_bad_pc()) {
+    state->pc = reinterpret_cast<Address>(simulator->get_pc());
+  }
+  state->sp = reinterpret_cast<Address>(simulator->get_register(Simulator::sp));
+  state->fp = reinterpret_cast<Address>(simulator->get_register(Simulator::fp));
+#endif
+  if (state->sp == 0 || state->fp == 0) {
+    // It possible that the simulator is interrupted while it is updating
+    // the sp or fp register. ARM64 simulator does this in two steps:
+    // first setting it to zero and then setting it to the new value.
+    // Bailout if sp/fp doesn't contain the new value.
+    //
+    // FIXME: The above doesn't really solve the issue.
+    // If a 64-bit target is executed on a 32-bit host even the final
+    // write is non-atomic, so it might obtain a half of the result.
+    // Moreover as long as the register set code uses memcpy (as of now),
+    // 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

src/profiler/tick-sample.h

@@ -0,0 +1,76 @@
+// 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.
+
+#ifndef V8_PROFILER_TICK_SAMPLE_H_
+#define V8_PROFILER_TICK_SAMPLE_H_
+
+#include "include/v8.h"
+
+#include "src/base/platform/time.h"
+#include "src/frames.h"
+#include "src/globals.h"
+
+namespace v8 {
+namespace internal {
+
+class Isolate;
+
+// ----------------------------------------------------------------------------
+// Sampler
+//
+// A sampler periodically samples the state of the VM and optionally
+// (if used for profiling) the program counter and stack pointer for
+// the thread that created it.
+
+// TickSample captures the information collected for each sample.
+struct TickSample {
+  // Internal profiling (with --prof + tools/$OS-tick-processor) wants to
+  // include the runtime function we're calling. Externally exposed tick
+  // samples don't care.
+  enum RecordCEntryFrame { kIncludeCEntryFrame, kSkipCEntryFrame };
+
+  TickSample()
+      : state(OTHER),
+        pc(NULL),
+        external_callback_entry(NULL),
+        frames_count(0),
+        has_external_callback(false),
+        update_stats(true),
+        top_frame_type(StackFrame::NONE) {}
+  void Init(Isolate* isolate, const v8::RegisterState& state,
+            RecordCEntryFrame record_c_entry_frame, bool update_stats);
+  static void GetStackSample(Isolate* isolate, const v8::RegisterState& state,
+                             RecordCEntryFrame record_c_entry_frame,
+                             void** frames, size_t frames_limit,
+                             v8::SampleInfo* sample_info);
+  StateTag state;  // The state of the VM.
+  Address pc;      // Instruction pointer.
+  union {
+    Address tos;   // Top stack value (*sp).
+    Address external_callback_entry;
+  };
+  static const unsigned kMaxFramesCountLog2 = 8;
+  static const unsigned kMaxFramesCount = (1 << kMaxFramesCountLog2) - 1;
+  Address stack[kMaxFramesCount];  // Call stack.
+  base::TimeTicks timestamp;
+  unsigned frames_count : kMaxFramesCountLog2;  // Number of captured frames.
+  bool has_external_callback : 1;
+  bool update_stats : 1;  // Whether the sample should update aggregated stats.
+  StackFrame::Type top_frame_type : 5;
+};
+
+
+#if defined(USE_SIMULATOR)
+class SimulatorHelper {
+ public:
+  // Returns true if register values were successfully retrieved
+  // from the simulator, otherwise returns false.
+  static bool FillRegisters(Isolate* isolate, v8::RegisterState* state);
+};
+#endif  // USE_SIMULATOR
+
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_PROFILER_TICK_SAMPLE_H_

src/v8.gyp

@@ -1005,6 +1005,8 @@
         'profiler/sampling-heap-profiler.h',
         'profiler/strings-storage.cc',
         'profiler/strings-storage.h',
+        'profiler/tick-sample.cc',
+        'profiler/tick-sample.h',
         'profiler/unbound-queue-inl.h',
         'profiler/unbound-queue.h',
         'property-descriptor.cc',

test/cctest/test-log-stack-tracer.cc

@@ -36,7 +36,7 @@
 #include "src/disassembler.h"
 #include "src/isolate.h"
 #include "src/log.h"
-#include "src/profiler/sampler.h"
+#include "src/profiler/tick-sample.h"
 #include "src/vm-state-inl.h"
 #include "test/cctest/cctest.h"
 #include "test/cctest/trace-extension.h"

test/cctest/trace-extension.cc

@@ -27,7 +27,7 @@
 
 #include "test/cctest/trace-extension.h"
 
-#include "src/profiler/sampler.h"
+#include "src/profiler/tick-sample.h"
 #include "src/vm-state-inl.h"
 #include "test/cctest/cctest.h"