Create libsampler as V8 sampler library.

src/libsampler/v8-sampler.cc

-// Copyright 2013 the V8 project authors. All rights reserved.
+// Copyright 2016 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/sampler.h"
+#include "src/libsampler/v8-sampler.h"
 
 #if V8_OS_POSIX && !V8_OS_CYGWIN
 
 #define USE_SIGNALS
 
 #include <errno.h>
 #include <pthread.h>
 #include <signal.h>
 #include <sys/time.h>
 
@@ skipping 21 matching lines @@
 #endif
 
 #elif V8_OS_WIN || V8_OS_CYGWIN
 
 #include "src/base/win32-headers.h"
 
 #endif
 
 #include "src/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/simulator.h"
-#include "src/v8threads.h"
-#include "src/vm-state-inl.h"
+#include "src/hashmap.h"
+#include "src/isolate.h"
 
 
 #if V8_OS_ANDROID && !defined(__BIONIC_HAVE_UCONTEXT_T)
 
 // Not all versions of Android's C library provide ucontext_t.
 // Detect this and provide custom but compatible definitions. Note that these
 // follow the GLibc naming convention to access register values from
 // mcontext_t.
 //
 // See http://code.google.com/p/android/issues/detail?id=34784
@@ skipping 87 matching lines @@
   mcontext_t uc_mcontext;
   // Other fields are not used by V8, don't define them here.
 } ucontext_t;
 enum { REG_RBP = 10, REG_RSP = 15, REG_RIP = 16 };
 #endif
 
 #endif  // V8_OS_ANDROID && !defined(__BIONIC_HAVE_UCONTEXT_T)
 
 
 namespace v8 {
-namespace internal {
 
 namespace {
 
-class PlatformDataCommon : public Malloced {
+static const int kMaxFramesCountLog2 = 8;
+static const unsigned kMaxFramesCount = (1u << kMaxFramesCountLog2) - 1;
+
+class PlatformDataCommon : public i::Malloced {
  public:
-  PlatformDataCommon() : profiled_thread_id_(ThreadId::Current()) {}
-  ThreadId profiled_thread_id() { return profiled_thread_id_; }
+  PlatformDataCommon() : profiled_thread_id_(i::ThreadId::Current()) {}
+  i::ThreadId profiled_thread_id() { return profiled_thread_id_; }
 
  protected:
   ~PlatformDataCommon() {}
 
  private:
-  ThreadId profiled_thread_id_;
+  i::ThreadId profiled_thread_id_;
 };
 
 
-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);
-}
+#if defined(USE_SIGNALS)
+typedef internal::List<Sampler*> SamplerList;
 
-
-// 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)
 class AtomicGuard {
  public:
-  explicit AtomicGuard(AtomicValue<int>* atomic, bool is_block = true)
+  explicit AtomicGuard(i::AtomicValue<int>* atomic, bool is_block = true)
       : atomic_(atomic),
         is_success_(false) {
     do {
       // Use Acquire_Load to gain mutual exclusion.
       USE(atomic_->Value());
       is_success_ = atomic_->TrySetValue(0, 1);
     } while (is_block && !is_success_);
   }
 
   bool is_success() { return is_success_; }
 
   ~AtomicGuard() {
     if (is_success_) {
       atomic_->SetValue(0);
     }
     atomic_ = NULL;
   }
 
  private:
-  AtomicValue<int>* atomic_;
+  i::AtomicValue<int>* atomic_;
   bool is_success_;
 };
 
 
 // Returns key for hash map.
 void* ThreadKey(pthread_t thread_id) {
   return reinterpret_cast<void*>(thread_id);
 }
 
 
@@ skipping 13 matching lines @@
 
 class Sampler::PlatformData : public PlatformDataCommon {
  public:
   PlatformData() : vm_tid_(pthread_self()) {}
   pthread_t vm_tid() const { return vm_tid_; }
 
  private:
   pthread_t vm_tid_;
 };
 
+
+class SamplerManager {

[fmeawad, 2016/05/02 23:14:37]

maybe SamplingManager?

+ public:
+  static void AddSampler(Sampler* sampler) {
+    AtomicGuard atomic_guard(&samplers_access_counter_);
+    DCHECK(sampler->IsActive());
+    // Add sampler into map if needed.
+    pthread_t thread_id = sampler->platform_data()->vm_tid();
+    i::HashMap::Entry *entry =
+        thread_id_to_samplers_.Pointer()->LookupOrInsert(ThreadKey(thread_id),
+                                                         ThreadHash(thread_id));
+    if (entry->value == NULL) {
+      SamplerList* samplers = new SamplerList();
+      samplers->Add(sampler);
+      entry->value = samplers;
+    } else {
+      SamplerList* samplers = reinterpret_cast<SamplerList*>(entry->value);
+      if (!samplers->Contains(sampler)) {
+        samplers->Add(sampler);
+      }
+    }
+  }
+
+  static void RemoveSampler(Sampler* sampler) {
+    AtomicGuard atomic_guard(&samplers_access_counter_);
+    DCHECK(sampler->IsActive());
+    // Remove sampler from map.
+    pthread_t thread_id = sampler->platform_data()->vm_tid();
+    void* thread_key = ThreadKey(thread_id);
+    uint32_t thread_hash = ThreadHash(thread_id);
+    i::HashMap::Entry* entry =
+        thread_id_to_samplers_.Get().Lookup(thread_key, thread_hash);
+    DCHECK(entry != NULL);
+    SamplerList* samplers = reinterpret_cast<SamplerList*>(entry->value);
+    samplers->RemoveElement(sampler);
+    if (samplers->is_empty()) {
+      thread_id_to_samplers_.Pointer()->Remove(thread_key, thread_hash);
+      delete samplers;
+    }
+  }
+
+ private:
+  struct HashMapCreateTrait {
+    static void Construct(internal::HashMap* allocated_ptr) {
+      new (allocated_ptr) internal::HashMap(internal::HashMap::PointersMatch);
+    }
+  };
+  friend class SignalHandler;
+  static base::LazyInstance<internal::HashMap, HashMapCreateTrait>::type
+      thread_id_to_samplers_;
+  static i::AtomicValue<int> samplers_access_counter_;
+};
+
+
+base::LazyInstance<i::HashMap, SamplerManager::HashMapCreateTrait>::type
+    SamplerManager::thread_id_to_samplers_ = LAZY_INSTANCE_INITIALIZER;
+i::AtomicValue<int> SamplerManager::samplers_access_counter_(0);
+
+
 #elif V8_OS_WIN || V8_OS_CYGWIN
 
 // ----------------------------------------------------------------------------
 // Win32 profiler support. On Cygwin we use the same sampler implementation as
 // on Win32.
 
 class Sampler::PlatformData : public PlatformDataCommon {
  public:
   // Get a handle to the calling thread. This is the thread that we are
   // going to profile. We need to make a copy of the handle because we are
@@ skipping 12 matching lines @@
       CloseHandle(profiled_thread_);
       profiled_thread_ = NULL;
     }
   }
 
   HANDLE profiled_thread() { return profiled_thread_; }
 
  private:
   HANDLE profiled_thread_;
 };
-#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
+#endif  // USE_SIGNALS
 
 
 #if defined(USE_SIGNALS)
-
-class SignalHandler : public AllStatic {
+class SignalHandler : public i::AllStatic {
  public:
   static void SetUp() { if (!mutex_) mutex_ = new base::Mutex(); }
   static void TearDown() { delete mutex_; mutex_ = NULL; }
 
   static void IncreaseSamplerCount() {
     base::LockGuard<base::Mutex> lock_guard(mutex_);
     if (++client_count_ == 1) Install();
   }
 
   static void DecreaseSamplerCount() {
     base::LockGuard<base::Mutex> lock_guard(mutex_);
     if (--client_count_ == 0) Restore();
   }
 
   static bool Installed() {
     return signal_handler_installed_;
   }
 
-#if !V8_OS_NACL
-  static void CollectSample(void* context, Sampler* sampler);
-#endif
-
  private:
   static void Install() {
 #if !V8_OS_NACL
     struct sigaction sa;
     sa.sa_sigaction = &HandleProfilerSignal;
     sigemptyset(&sa.sa_mask);
 #if V8_OS_QNX
     sa.sa_flags = SA_SIGINFO;
 #else
     sa.sa_flags = SA_RESTART | SA_SIGINFO;
 #endif
     signal_handler_installed_ =
         (sigaction(SIGPROF, &sa, &old_signal_handler_) == 0);
-#endif
+#endif  // !V8_OS_NACL
   }
 
   static void Restore() {
 #if !V8_OS_NACL
     if (signal_handler_installed_) {
       sigaction(SIGPROF, &old_signal_handler_, 0);
       signal_handler_installed_ = false;
     }
 #endif
   }
@@ skipping 10 matching lines @@
 
 
 base::Mutex* SignalHandler::mutex_ = NULL;
 int SignalHandler::client_count_ = 0;
 struct sigaction SignalHandler::old_signal_handler_;
 bool SignalHandler::signal_handler_installed_ = false;
 
 
 // As Native Client does not support signal handling, profiling is disabled.
 #if !V8_OS_NACL
-void SignalHandler::CollectSample(void* context, Sampler* sampler) {
-  if (sampler == NULL || (!sampler->IsProfiling() &&
-                          !sampler->IsRegistered())) {
-    return;
-  }
-  Isolate* isolate = sampler->isolate();
-
-  // We require a fully initialized and entered isolate.
-  if (isolate == NULL || !isolate->IsInUse()) return;
-
-  if (v8::Locker::IsActive() &&
-      !isolate->thread_manager()->IsLockedByCurrentThread()) {
-    return;
-  }
-
-  v8::RegisterState state;
-
-#if defined(USE_SIMULATOR)
-  if (!SimulatorHelper::FillRegisters(isolate, &state)) return;
-#else
-  // Extracting the sample from the context is extremely machine dependent.
-  ucontext_t* ucontext = reinterpret_cast<ucontext_t*>(context);
-#if !(V8_OS_OPENBSD || (V8_OS_LINUX && (V8_HOST_ARCH_PPC || V8_HOST_ARCH_S390)))
-  mcontext_t& mcontext = ucontext->uc_mcontext;
-#endif
-#if V8_OS_LINUX
-#if V8_HOST_ARCH_IA32
-  state.pc = reinterpret_cast<Address>(mcontext.gregs[REG_EIP]);
-  state.sp = reinterpret_cast<Address>(mcontext.gregs[REG_ESP]);
-  state.fp = reinterpret_cast<Address>(mcontext.gregs[REG_EBP]);
-#elif V8_HOST_ARCH_X64
-  state.pc = reinterpret_cast<Address>(mcontext.gregs[REG_RIP]);
-  state.sp = reinterpret_cast<Address>(mcontext.gregs[REG_RSP]);
-  state.fp = reinterpret_cast<Address>(mcontext.gregs[REG_RBP]);
-#elif V8_HOST_ARCH_ARM
-#if V8_LIBC_GLIBC && !V8_GLIBC_PREREQ(2, 4)
-  // Old GLibc ARM versions used a gregs[] array to access the register
-  // values from mcontext_t.
-  state.pc = reinterpret_cast<Address>(mcontext.gregs[R15]);
-  state.sp = reinterpret_cast<Address>(mcontext.gregs[R13]);
-  state.fp = reinterpret_cast<Address>(mcontext.gregs[R11]);
-#else
-  state.pc = reinterpret_cast<Address>(mcontext.arm_pc);
-  state.sp = reinterpret_cast<Address>(mcontext.arm_sp);
-  state.fp = reinterpret_cast<Address>(mcontext.arm_fp);
-#endif  // V8_LIBC_GLIBC && !V8_GLIBC_PREREQ(2, 4)
-#elif V8_HOST_ARCH_ARM64
-  state.pc = reinterpret_cast<Address>(mcontext.pc);
-  state.sp = reinterpret_cast<Address>(mcontext.sp);
-  // FP is an alias for x29.
-  state.fp = reinterpret_cast<Address>(mcontext.regs[29]);
-#elif V8_HOST_ARCH_MIPS
-  state.pc = reinterpret_cast<Address>(mcontext.pc);
-  state.sp = reinterpret_cast<Address>(mcontext.gregs[29]);
-  state.fp = reinterpret_cast<Address>(mcontext.gregs[30]);
-#elif V8_HOST_ARCH_MIPS64
-  state.pc = reinterpret_cast<Address>(mcontext.pc);
-  state.sp = reinterpret_cast<Address>(mcontext.gregs[29]);
-  state.fp = reinterpret_cast<Address>(mcontext.gregs[30]);
-#elif V8_HOST_ARCH_PPC
-  state.pc = reinterpret_cast<Address>(ucontext->uc_mcontext.regs->nip);
-  state.sp = reinterpret_cast<Address>(ucontext->uc_mcontext.regs->gpr[PT_R1]);
-  state.fp = reinterpret_cast<Address>(ucontext->uc_mcontext.regs->gpr[PT_R31]);
-#elif V8_HOST_ARCH_S390
-#if V8_TARGET_ARCH_32_BIT
-  // 31-bit target will have bit 0 (MSB) of the PSW set to denote addressing
-  // mode.  This bit needs to be masked out to resolve actual address.
-  state.pc =
-      reinterpret_cast<Address>(ucontext->uc_mcontext.psw.addr & 0x7FFFFFFF);
-#else
-  state.pc = reinterpret_cast<Address>(ucontext->uc_mcontext.psw.addr);
-#endif  // V8_TARGET_ARCH_32_BIT
-  state.sp = reinterpret_cast<Address>(ucontext->uc_mcontext.gregs[15]);
-  state.fp = reinterpret_cast<Address>(ucontext->uc_mcontext.gregs[11]);
-#endif  // V8_HOST_ARCH_*
-#elif V8_OS_MACOSX
-#if V8_HOST_ARCH_X64
-#if __DARWIN_UNIX03
-  state.pc = reinterpret_cast<Address>(mcontext->__ss.__rip);
-  state.sp = reinterpret_cast<Address>(mcontext->__ss.__rsp);
-  state.fp = reinterpret_cast<Address>(mcontext->__ss.__rbp);
-#else  // !__DARWIN_UNIX03
-  state.pc = reinterpret_cast<Address>(mcontext->ss.rip);
-  state.sp = reinterpret_cast<Address>(mcontext->ss.rsp);
-  state.fp = reinterpret_cast<Address>(mcontext->ss.rbp);
-#endif  // __DARWIN_UNIX03
-#elif V8_HOST_ARCH_IA32
-#if __DARWIN_UNIX03
-  state.pc = reinterpret_cast<Address>(mcontext->__ss.__eip);
-  state.sp = reinterpret_cast<Address>(mcontext->__ss.__esp);
-  state.fp = reinterpret_cast<Address>(mcontext->__ss.__ebp);
-#else  // !__DARWIN_UNIX03
-  state.pc = reinterpret_cast<Address>(mcontext->ss.eip);
-  state.sp = reinterpret_cast<Address>(mcontext->ss.esp);
-  state.fp = reinterpret_cast<Address>(mcontext->ss.ebp);
-#endif  // __DARWIN_UNIX03
-#endif  // V8_HOST_ARCH_IA32
-#elif V8_OS_FREEBSD
-#if V8_HOST_ARCH_IA32
-  state.pc = reinterpret_cast<Address>(mcontext.mc_eip);
-  state.sp = reinterpret_cast<Address>(mcontext.mc_esp);
-  state.fp = reinterpret_cast<Address>(mcontext.mc_ebp);
-#elif V8_HOST_ARCH_X64
-  state.pc = reinterpret_cast<Address>(mcontext.mc_rip);
-  state.sp = reinterpret_cast<Address>(mcontext.mc_rsp);
-  state.fp = reinterpret_cast<Address>(mcontext.mc_rbp);
-#elif V8_HOST_ARCH_ARM
-  state.pc = reinterpret_cast<Address>(mcontext.mc_r15);
-  state.sp = reinterpret_cast<Address>(mcontext.mc_r13);
-  state.fp = reinterpret_cast<Address>(mcontext.mc_r11);
-#endif  // V8_HOST_ARCH_*
-#elif V8_OS_NETBSD
-#if V8_HOST_ARCH_IA32
-  state.pc = reinterpret_cast<Address>(mcontext.__gregs[_REG_EIP]);
-  state.sp = reinterpret_cast<Address>(mcontext.__gregs[_REG_ESP]);
-  state.fp = reinterpret_cast<Address>(mcontext.__gregs[_REG_EBP]);
-#elif V8_HOST_ARCH_X64
-  state.pc = reinterpret_cast<Address>(mcontext.__gregs[_REG_RIP]);
-  state.sp = reinterpret_cast<Address>(mcontext.__gregs[_REG_RSP]);
-  state.fp = reinterpret_cast<Address>(mcontext.__gregs[_REG_RBP]);
-#endif  // V8_HOST_ARCH_*
-#elif V8_OS_OPENBSD
-#if V8_HOST_ARCH_IA32
-  state.pc = reinterpret_cast<Address>(ucontext->sc_eip);
-  state.sp = reinterpret_cast<Address>(ucontext->sc_esp);
-  state.fp = reinterpret_cast<Address>(ucontext->sc_ebp);
-#elif V8_HOST_ARCH_X64
-  state.pc = reinterpret_cast<Address>(ucontext->sc_rip);
-  state.sp = reinterpret_cast<Address>(ucontext->sc_rsp);
-  state.fp = reinterpret_cast<Address>(ucontext->sc_rbp);
-#endif  // V8_HOST_ARCH_*
-#elif V8_OS_SOLARIS
-  state.pc = reinterpret_cast<Address>(mcontext.gregs[REG_PC]);
-  state.sp = reinterpret_cast<Address>(mcontext.gregs[REG_SP]);
-  state.fp = reinterpret_cast<Address>(mcontext.gregs[REG_FP]);
-#elif V8_OS_QNX
-#if V8_HOST_ARCH_IA32
-  state.pc = reinterpret_cast<Address>(mcontext.cpu.eip);
-  state.sp = reinterpret_cast<Address>(mcontext.cpu.esp);
-  state.fp = reinterpret_cast<Address>(mcontext.cpu.ebp);
-#elif V8_HOST_ARCH_ARM
-  state.pc = reinterpret_cast<Address>(mcontext.cpu.gpr[ARM_REG_PC]);
-  state.sp = reinterpret_cast<Address>(mcontext.cpu.gpr[ARM_REG_SP]);
-  state.fp = reinterpret_cast<Address>(mcontext.cpu.gpr[ARM_REG_FP]);
-#endif  // V8_HOST_ARCH_*
-#elif V8_OS_AIX
-  state.pc = reinterpret_cast<Address>(mcontext.jmp_context.iar);
-  state.sp = reinterpret_cast<Address>(mcontext.jmp_context.gpr[1]);
-  state.fp = reinterpret_cast<Address>(mcontext.jmp_context.gpr[31]);
-#endif  // V8_OS_AIX
-#endif  // USE_SIMULATOR
-  sampler->SampleStack(state);
-}
-#endif  // V8_OS_NACL
-
-#endif  // USE_SIGNALS
-
-
-class SamplerThread : public base::Thread {
- public:
-  static const int kSamplerThreadStackSize = 64 * KB;
-
-  explicit SamplerThread(int interval)
-      : Thread(base::Thread::Options("SamplerThread", kSamplerThreadStackSize)),
-        interval_(interval) {}
-
-  static void SetUp() { if (!mutex_) mutex_ = new base::Mutex(); }
-  static void TearDown() { delete mutex_; mutex_ = NULL; }
-
-  static void AddActiveSampler(Sampler* sampler) {
-    bool need_to_start = false;
-    base::LockGuard<base::Mutex> lock_guard(mutex_);
-    if (instance_ == NULL) {
-      // Start a thread that will send SIGPROF signal to VM threads,
-      // when CPU profiling will be enabled.
-      instance_ = new SamplerThread(sampler->interval());
-      need_to_start = true;
-    }
-
-    DCHECK(sampler->IsActive());
-    DCHECK(instance_->interval_ == sampler->interval());
-
-#if defined(USE_SIGNALS)
-    AddSampler(sampler);
-#else
-    DCHECK(!instance_->active_samplers_.Contains(sampler));
-    instance_->active_samplers_.Add(sampler);
-#endif  // USE_SIGNALS
-
-    if (need_to_start) instance_->StartSynchronously();
-  }
-
-  static void RemoveSampler(Sampler* sampler) {
-    SamplerThread* instance_to_remove = NULL;
-    {
-      base::LockGuard<base::Mutex> lock_guard(mutex_);
-
-      DCHECK(sampler->IsActive() || sampler->IsRegistered());
-#if defined(USE_SIGNALS)
-      {
-        AtomicGuard atomic_guard(&sampler_list_access_counter_);
-        // Remove sampler from map.
-        pthread_t thread_id = sampler->platform_data()->vm_tid();
-        void* thread_key = ThreadKey(thread_id);
-        uint32_t thread_hash = ThreadHash(thread_id);
-        HashMap::Entry* entry =
-            thread_id_to_samplers_.Get().Lookup(thread_key, thread_hash);
-        DCHECK(entry != NULL);
-        SamplerList* samplers = reinterpret_cast<SamplerList*>(entry->value);
-        samplers->RemoveElement(sampler);
-        if (samplers->is_empty()) {
-          thread_id_to_samplers_.Pointer()->Remove(thread_key, thread_hash);
-          delete samplers;
-        }
-        if (thread_id_to_samplers_.Get().occupancy() == 0) {
-          instance_to_remove = instance_;
-          instance_ = NULL;
-        }
-      }
-#else
-      bool removed = instance_->active_samplers_.RemoveElement(sampler);
-      DCHECK(removed);
-      USE(removed);
-
-      // We cannot delete the instance immediately as we need to Join() the
-      // thread but we are holding mutex_ and the thread may try to acquire it.
-      if (instance_->active_samplers_.is_empty()) {
-        instance_to_remove = instance_;
-        instance_ = NULL;
-      }
-#endif  // USE_SIGNALS
-    }
-
-    if (!instance_to_remove) return;
-    instance_to_remove->Join();
-    delete instance_to_remove;
-  }
-
-  // Unlike AddActiveSampler, this method only adds a sampler,
-  // but won't start the sampler thread.
-  static void RegisterSampler(Sampler* sampler) {
-    base::LockGuard<base::Mutex> lock_guard(mutex_);
-#if defined(USE_SIGNALS)
-    AddSampler(sampler);
-#endif  // USE_SIGNALS
-  }
-
-  // Implement Thread::Run().
-  virtual void Run() {
-    while (true) {
-      {
-        base::LockGuard<base::Mutex> lock_guard(mutex_);
-#if defined(USE_SIGNALS)
-        if (thread_id_to_samplers_.Get().occupancy() == 0) break;
-        if (SignalHandler::Installed()) {
-          for (HashMap::Entry *p = thread_id_to_samplers_.Get().Start();
-               p != NULL; p = thread_id_to_samplers_.Get().Next(p)) {
-            pthread_t thread_id = reinterpret_cast<pthread_t>(p->key);
-            pthread_kill(thread_id, SIGPROF);
-          }
-        }
-#else
-        if (active_samplers_.is_empty()) break;
-        // When CPU profiling is enabled both JavaScript and C++ code is
-        // profiled. We must not suspend.
-        for (int i = 0; i < active_samplers_.length(); ++i) {
-          Sampler* sampler = active_samplers_.at(i);
-          if (!sampler->IsProfiling()) continue;
-          sampler->DoSample();
-        }
-#endif  // USE_SIGNALS
-      }
-      base::OS::Sleep(base::TimeDelta::FromMilliseconds(interval_));
-    }
-  }
-
- private:
-  // Protects the process wide state below.
-  static base::Mutex* mutex_;
-  static SamplerThread* instance_;
-
-  const int interval_;
-
-#if defined(USE_SIGNALS)
-  struct HashMapCreateTrait {
-    static void Construct(HashMap* allocated_ptr) {
-      new (allocated_ptr) HashMap(HashMap::PointersMatch);
-    }
-  };
-  friend class SignalHandler;
-  static base::LazyInstance<HashMap, HashMapCreateTrait>::type
-      thread_id_to_samplers_;
-  static AtomicValue<int> sampler_list_access_counter_;
-  static void AddSampler(Sampler* sampler) {
-    AtomicGuard atomic_guard(&sampler_list_access_counter_);
-    // Add sampler into map if needed.
-    pthread_t thread_id = sampler->platform_data()->vm_tid();
-    HashMap::Entry *entry =
-        thread_id_to_samplers_.Pointer()->LookupOrInsert(ThreadKey(thread_id),
-                                                         ThreadHash(thread_id));
-    if (entry->value == NULL) {
-      SamplerList* samplers = new SamplerList();
-      samplers->Add(sampler);
-      entry->value = samplers;
-    } else {
-      SamplerList* samplers = reinterpret_cast<SamplerList*>(entry->value);
-      if (!samplers->Contains(sampler)) {
-        samplers->Add(sampler);
-      }
-    }
-  }
-#else
-  SamplerList active_samplers_;
-#endif  // USE_SIGNALS
-
-  DISALLOW_COPY_AND_ASSIGN(SamplerThread);
-};
-
-
-base::Mutex* SamplerThread::mutex_ = NULL;
-SamplerThread* SamplerThread::instance_ = NULL;
-#if defined(USE_SIGNALS)
-base::LazyInstance<HashMap, SamplerThread::HashMapCreateTrait>::type
-    SamplerThread::thread_id_to_samplers_ = LAZY_INSTANCE_INITIALIZER;
-AtomicValue<int> SamplerThread::sampler_list_access_counter_(0);
-
-// As Native Client does not support signal handling, profiling is disabled.
-#if !V8_OS_NACL
 void SignalHandler::HandleProfilerSignal(int signal, siginfo_t* info,
                                          void* context) {
   USE(info);
   if (signal != SIGPROF) return;
-  AtomicGuard atomic_guard(&SamplerThread::sampler_list_access_counter_, false);
+  AtomicGuard atomic_guard(&SamplerManager::samplers_access_counter_, false);
   if (!atomic_guard.is_success()) return;
   pthread_t thread_id = pthread_self();
-  HashMap::Entry* entry =
-      SamplerThread::thread_id_to_samplers_.Pointer()->Lookup(
+  i::HashMap::Entry* entry =
+      SamplerManager::thread_id_to_samplers_.Pointer()->Lookup(
           ThreadKey(thread_id), ThreadHash(thread_id));
   if (entry == NULL)
     return;
   SamplerList* samplers = reinterpret_cast<SamplerList*>(entry->value);
   for (int i = 0; i < samplers->length(); ++i) {
     Sampler* sampler = samplers->at(i);
-    CollectSample(context, sampler);
+    if (sampler == NULL || !sampler->IsProfiling()) {
+      return;
+    }
+    Isolate* isolate = sampler->isolate();
+
+    // We require a fully initialized and entered isolate.
+    if (isolate == NULL || !isolate->IsInUse()) return;
+
+    if (v8::Locker::IsActive() && !Locker::IsLocked(isolate)) {
+      return;
+    }
+
+    v8::RegisterState state;

[alph, 2016/05/03 18:48:07]

You can move register filling out of the loop. Moreover it's better to have it
as a separate function, as it has clean interface and quite lengthy.

[lpy, 2016/05/04 00:09:24]

Done.

+
+    // Extracting the sample from the context is extremely machine dependent.
+    ucontext_t* ucontext = reinterpret_cast<ucontext_t*>(context);
+#if !(V8_OS_OPENBSD || (V8_OS_LINUX && (V8_HOST_ARCH_PPC || V8_HOST_ARCH_S390)))
+    mcontext_t& mcontext = ucontext->uc_mcontext;
+#endif
+#if V8_OS_LINUX
+#if V8_HOST_ARCH_IA32
+    state.pc = reinterpret_cast<void*>(mcontext.gregs[REG_EIP]);
+    state.sp = reinterpret_cast<void*>(mcontext.gregs[REG_ESP]);
+    state.fp = reinterpret_cast<void*>(mcontext.gregs[REG_EBP]);
+#elif V8_HOST_ARCH_X64
+    state.pc = reinterpret_cast<void*>(mcontext.gregs[REG_RIP]);
+    state.sp = reinterpret_cast<void*>(mcontext.gregs[REG_RSP]);
+    state.fp = reinterpret_cast<void*>(mcontext.gregs[REG_RBP]);
+#elif V8_HOST_ARCH_ARM
+#if V8_LIBC_GLIBC && !V8_GLIBC_PREREQ(2, 4)
+    // Old GLibc ARM versions used a gregs[] array to access the register
+    // values from mcontext_t.
+    state.pc = reinterpret_cast<void*>(mcontext.gregs[R15]);
+    state.sp = reinterpret_cast<void*>(mcontext.gregs[R13]);
+    state.fp = reinterpret_cast<void*>(mcontext.gregs[R11]);
+#else
+    state.pc = reinterpret_cast<void*>(mcontext.arm_pc);
+    state.sp = reinterpret_cast<void*>(mcontext.arm_sp);
+    state.fp = reinterpret_cast<void*>(mcontext.arm_fp);
+#endif  // V8_LIBC_GLIBC && !V8_GLIBC_PREREQ(2, 4)
+#elif V8_HOST_ARCH_ARM64
+    state.pc = reinterpret_cast<void*>(mcontext.pc);
+    state.sp = reinterpret_cast<void*>(mcontext.sp);
+    // FP is an alias for x29.
+    state.fp = reinterpret_cast<void*>(mcontext.regs[29]);
+#elif V8_HOST_ARCH_MIPS
+    state.pc = reinterpret_cast<void*>(mcontext.pc);
+    state.sp = reinterpret_cast<void*>(mcontext.gregs[29]);
+    state.fp = reinterpret_cast<void*>(mcontext.gregs[30]);
+#elif V8_HOST_ARCH_MIPS64
+    state.pc = reinterpret_cast<void*>(mcontext.pc);
+    state.sp = reinterpret_cast<void*>(mcontext.gregs[29]);
+    state.fp = reinterpret_cast<void*>(mcontext.gregs[30]);
+#elif V8_HOST_ARCH_PPC
+    state.pc = reinterpret_cast<void*>(ucontext->uc_mcontext.regs->nip);
+    state.sp =
+        reinterpret_cast<void*>(ucontext->uc_mcontext.regs->gpr[PT_R1]);
+    state.fp =
+        reinterpret_cast<void*>(ucontext->uc_mcontext.regs->gpr[PT_R31]);
+#elif V8_HOST_ARCH_S390
+#if V8_TARGET_ARCH_32_BIT
+    // 31-bit target will have bit 0 (MSB) of the PSW set to denote addressing
+    // mode.  This bit needs to be masked out to resolve actual address.
+    state.pc =
+        reinterpret_cast<void*>(ucontext->uc_mcontext.psw.addr & 0x7FFFFFFF);
+#else
+    state.pc = reinterpret_cast<void*>(ucontext->uc_mcontext.psw.addr);
+#endif  // V8_TARGET_ARCH_32_BIT
+    state.sp = reinterpret_cast<void*>(ucontext->uc_mcontext.gregs[15]);
+    state.fp = reinterpret_cast<void*>(ucontext->uc_mcontext.gregs[11]);
+#endif  // V8_HOST_ARCH_*
+#elif V8_OS_MACOSX
+#if V8_HOST_ARCH_X64
+#if __DARWIN_UNIX03
+    state.pc = reinterpret_cast<void*>(mcontext->__ss.__rip);
+    state.sp = reinterpret_cast<void*>(mcontext->__ss.__rsp);
+    state.fp = reinterpret_cast<void*>(mcontext->__ss.__rbp);
+#else  // !__DARWIN_UNIX03
+    state.pc = reinterpret_cast<void*>(mcontext->ss.rip);
+    state.sp = reinterpret_cast<void*>(mcontext->ss.rsp);
+    state.fp = reinterpret_cast<void*>(mcontext->ss.rbp);
+#endif  // __DARWIN_UNIX03
+#elif V8_HOST_ARCH_IA32
+#if __DARWIN_UNIX03
+    state.pc = reinterpret_cast<void*>(mcontext->__ss.__eip);
+    state.sp = reinterpret_cast<void*>(mcontext->__ss.__esp);
+    state.fp = reinterpret_cast<void*>(mcontext->__ss.__ebp);
+#else  // !__DARWIN_UNIX03
+    state.pc = reinterpret_cast<void*>(mcontext->ss.eip);
+    state.sp = reinterpret_cast<void*>(mcontext->ss.esp);
+    state.fp = reinterpret_cast<void*>(mcontext->ss.ebp);
+#endif  // __DARWIN_UNIX03
+#endif  // V8_HOST_ARCH_IA32
+#elif V8_OS_FREEBSD
+#if V8_HOST_ARCH_IA32
+    state.pc = reinterpret_cast<void*>(mcontext.mc_eip);
+    state.sp = reinterpret_cast<void*>(mcontext.mc_esp);
+    state.fp = reinterpret_cast<void*>(mcontext.mc_ebp);
+#elif V8_HOST_ARCH_X64
+    state.pc = reinterpret_cast<void*>(mcontext.mc_rip);
+    state.sp = reinterpret_cast<void*>(mcontext.mc_rsp);
+    state.fp = reinterpret_cast<void*>(mcontext.mc_rbp);
+#elif V8_HOST_ARCH_ARM
+    state.pc = reinterpret_cast<void*>(mcontext.mc_r15);
+    state.sp = reinterpret_cast<void*>(mcontext.mc_r13);
+    state.fp = reinterpret_cast<void*>(mcontext.mc_r11);
+#endif  // V8_HOST_ARCH_*
+#elif V8_OS_NETBSD
+#if V8_HOST_ARCH_IA32
+    state.pc = reinterpret_cast<void*>(mcontext.__gregs[_REG_EIP]);
+    state.sp = reinterpret_cast<void*>(mcontext.__gregs[_REG_ESP]);
+    state.fp = reinterpret_cast<void*>(mcontext.__gregs[_REG_EBP]);
+#elif V8_HOST_ARCH_X64
+    state.pc = reinterpret_cast<void*>(mcontext.__gregs[_REG_RIP]);
+    state.sp = reinterpret_cast<void*>(mcontext.__gregs[_REG_RSP]);
+    state.fp = reinterpret_cast<void*>(mcontext.__gregs[_REG_RBP]);
+#endif  // V8_HOST_ARCH_*
+#elif V8_OS_OPENBSD
+#if V8_HOST_ARCH_IA32
+    state.pc = reinterpret_cast<void*>(ucontext->sc_eip);
+    state.sp = reinterpret_cast<void*>(ucontext->sc_esp);
+    state.fp = reinterpret_cast<void*>(ucontext->sc_ebp);
+#elif V8_HOST_ARCH_X64
+    state.pc = reinterpret_cast<void*>(ucontext->sc_rip);
+    state.sp = reinterpret_cast<void*>(ucontext->sc_rsp);
+    state.fp = reinterpret_cast<void*>(ucontext->sc_rbp);
+#endif  // V8_HOST_ARCH_*
+#elif V8_OS_SOLARIS
+    state.pc = reinterpret_cast<void*>(mcontext.gregs[REG_PC]);
+    state.sp = reinterpret_cast<void*>(mcontext.gregs[REG_SP]);
+    state.fp = reinterpret_cast<void*>(mcontext.gregs[REG_FP]);
+#elif V8_OS_QNX
+#if V8_HOST_ARCH_IA32
+    state.pc = reinterpret_cast<void*>(mcontext.cpu.eip);
+    state.sp = reinterpret_cast<void*>(mcontext.cpu.esp);
+    state.fp = reinterpret_cast<void*>(mcontext.cpu.ebp);
+#elif V8_HOST_ARCH_ARM
+    state.pc = reinterpret_cast<void*>(mcontext.cpu.gpr[ARM_REG_PC]);
+    state.sp = reinterpret_cast<void*>(mcontext.cpu.gpr[ARM_REG_SP]);
+    state.fp = reinterpret_cast<void*>(mcontext.cpu.gpr[ARM_REG_FP]);
+#endif  // V8_HOST_ARCH_*
+#elif V8_OS_AIX
+    state.pc = reinterpret_cast<void*>(mcontext.jmp_context.iar);
+    state.sp = reinterpret_cast<void*>(mcontext.jmp_context.gpr[1]);
+    state.fp = reinterpret_cast<void*>(mcontext.jmp_context.gpr[31]);
+#endif  // V8_OS_AIX
+    sampler->SampleStack(state);
   }
 }
-#endif  // !V8_OS_NACL
-#endif  // USE_SIGNALs
+#endif  // V8_OS_NACL
 
-
-//
-// 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;
-}
+#endif  // USE_SIGNALS
 
 
 void Sampler::SetUp() {
 #if defined(USE_SIGNALS)
   SignalHandler::SetUp();
 #endif
-  SamplerThread::SetUp();
 }
 
 
 void Sampler::TearDown() {
-  SamplerThread::TearDown();
 #if defined(USE_SIGNALS)
   SignalHandler::TearDown();
 #endif
 }
 
-Sampler::Sampler(Isolate* isolate, int interval)
+Sampler::Sampler(Isolate* isolate)
     : isolate_(isolate),
-      interval_(interval),
       profiling_(false),
-      has_processing_thread_(false),
       active_(false),
-      registered_(false),
       is_counting_samples_(false),
       js_sample_count_(0),
       external_sample_count_(0) {
   data_ = new PlatformData;
 }
 
 Sampler::~Sampler() {
   DCHECK(!IsActive());
-  if (IsRegistered()) {
-    SamplerThread::RemoveSampler(this);
-  }
   delete data_;
 }
 
 void Sampler::Start() {
   DCHECK(!IsActive());
   SetActive(true);
-  SamplerThread::AddActiveSampler(this);
+  SamplerManager::AddSampler(this);
 }
 
 
 void Sampler::Stop() {
+  SamplerManager::RemoveSampler(this);
   DCHECK(IsActive());
-  SamplerThread::RemoveSampler(this);
   SetActive(false);
-  SetRegistered(false);
 }
 
 
 void Sampler::IncreaseProfilingDepth() {
   base::NoBarrier_AtomicIncrement(&profiling_, 1);
 #if defined(USE_SIGNALS)
   SignalHandler::IncreaseSamplerCount();
 #endif
 }
 
 
 void Sampler::DecreaseProfilingDepth() {
 #if defined(USE_SIGNALS)
   SignalHandler::DecreaseSamplerCount();
 #endif
   base::NoBarrier_AtomicIncrement(&profiling_, -1);
 }
 
 
 void Sampler::SampleStack(const v8::RegisterState& state) {
-  TickSample* sample = isolate_->cpu_profiler()->StartTickSample();
-  TickSample sample_obj;
-  if (sample == NULL) sample = &sample_obj;
-  sample->Init(isolate_, state, TickSample::kIncludeCEntryFrame, true);
-  if (is_counting_samples_ && !sample->timestamp.IsNull()) {
-    if (sample->state == JS) ++js_sample_count_;
-    if (sample->state == EXTERNAL) ++external_sample_count_;
-  }
-  Tick(sample);
-  if (sample != &sample_obj) {
-    isolate_->cpu_profiler()->FinishTickSample();
+  const void* frames_[kMaxFramesCount];
+  v8::SampleInfo sample_info;
+
+  isolate_->GetStackSample(state, reinterpret_cast<void**>(frames_),
+                           kMaxFramesCount, &sample_info);
+
+  if (is_counting_samples_) {
+    if (sample_info.vm_state == JS) ++js_sample_count_;
+    if (sample_info.vm_state == EXTERNAL) ++external_sample_count_;
   }
 }
 
 
 #if defined(USE_SIGNALS)
 
 void Sampler::DoSample() {
   if (!SignalHandler::Installed()) return;
-  if (!IsActive() && !IsRegistered()) {
-    SamplerThread::RegisterSampler(this);
-    SetRegistered(true);
-  }
   pthread_kill(platform_data()->vm_tid(), SIGPROF);
 }
 
 #elif V8_OS_WIN || V8_OS_CYGWIN
 
 void Sampler::DoSample() {
   HANDLE profiled_thread = platform_data()->profiled_thread();
   if (profiled_thread == NULL) return;
 
   const DWORD kSuspendFailed = static_cast<DWORD>(-1);
   if (SuspendThread(profiled_thread) == kSuspendFailed) return;
 
   // Context used for sampling the register state of the profiled thread.
   CONTEXT context;
   memset(&context, 0, sizeof(context));
   context.ContextFlags = CONTEXT_FULL;
   if (GetThreadContext(profiled_thread, &context) != 0) {
     v8::RegisterState state;
-#if defined(USE_SIMULATOR)
-    if (!SimulatorHelper::FillRegisters(isolate(), &state)) {
-      ResumeThread(profiled_thread);
-      return;
-    }
+#if V8_HOST_ARCH_X64
+    state.pc = reinterpret_cast<void*>(context.Rip);
+    state.sp = reinterpret_cast<void*>(context.Rsp);
+    state.fp = reinterpret_cast<void*>(context.Rbp);
 #else
-#if V8_HOST_ARCH_X64
-    state.pc = reinterpret_cast<Address>(context.Rip);
-    state.sp = reinterpret_cast<Address>(context.Rsp);
-    state.fp = reinterpret_cast<Address>(context.Rbp);
-#else
-    state.pc = reinterpret_cast<Address>(context.Eip);
-    state.sp = reinterpret_cast<Address>(context.Esp);
-    state.fp = reinterpret_cast<Address>(context.Ebp);
+    state.pc = reinterpret_cast<void*>(context.Eip);
+    state.sp = reinterpret_cast<void*>(context.Esp);
+    state.fp = reinterpret_cast<void*>(context.Ebp);
 #endif
-#endif  // USE_SIMULATOR
     SampleStack(state);
   }
   ResumeThread(profiled_thread);
 }
 
 #endif  // USE_SIGNALS
 
 
-}  // namespace internal
 }  // namespace v8