src/vm-state-inl.h

// Copyright 2010 the V8 project authors. All rights reserved.
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#ifndef V8_VM_STATE_INL_H_
#define V8_VM_STATE_INL_H_

#include "vm-state.h"

namespace v8 {
namespace internal {

//
// VMState class implementation.  A simple stack of VM states held by the
// logger and partially threaded through the call stack.  States are pushed by
// VMState construction and popped by destruction.
//
#ifdef ENABLE_VMSTATE_TRACKING
inline const char* StateToString(StateTag state) {
  switch (state) {
    case JS:
      return "JS";
    case GC:
      return "GC";
    case COMPILER:
      return "COMPILER";
    case OTHER:
      return "OTHER";
    default:
      UNREACHABLE();
      return NULL;
  }
}

VMState::VMState(StateTag state)
    : disabled_(true),
      state_(OTHER),
      external_callback_(NULL) {
#ifdef ENABLE_LOGGING_AND_PROFILING
  if (!Logger::is_logging() && !CpuProfiler::is_profiling()) {
    return;
  }
#endif

  disabled_ = false;
#if !defined(ENABLE_HEAP_PROTECTION)
  // When not protecting the heap, there is no difference between
  // EXTERNAL and OTHER.  As an optimization in that case, we will not
  // perform EXTERNAL->OTHER transitions through the API.  We thus
  // compress the two states into one.
  if (state == EXTERNAL) state = OTHER;
#endif
  state_ = state;
  // Save the previous state.
  previous_ = reinterpret_cast<VMState*>(current_state_);
  // Install the new state.
  OS::ReleaseStore(&current_state_, reinterpret_cast<AtomicWord>(this));

#ifdef ENABLE_LOGGING_AND_PROFILING
  if (FLAG_log_state_changes) {
    LOG(UncheckedStringEvent("Entering", StateToString(state_)));
    if (previous_ != NULL) {
      LOG(UncheckedStringEvent("From", StateToString(previous_->state_)));
    }
  }
#endif

#ifdef ENABLE_HEAP_PROTECTION
  if (FLAG_protect_heap) {
    if (state_ == EXTERNAL) {
      // We are leaving V8.
      ASSERT((previous_ != NULL) && (previous_->state_ != EXTERNAL));
      Heap::Protect();
    } else if ((previous_ == NULL) || (previous_->state_ == EXTERNAL)) {
      // We are entering V8.
      Heap::Unprotect();
    }
  }
#endif
}


VMState::~VMState() {
  if (disabled_) return;
  // Return to the previous state.
  OS::ReleaseStore(&current_state_, reinterpret_cast<AtomicWord>(previous_));

#ifdef ENABLE_LOGGING_AND_PROFILING
  if (FLAG_log_state_changes) {
    LOG(UncheckedStringEvent("Leaving", StateToString(state_)));
    if (previous_ != NULL) {
      LOG(UncheckedStringEvent("To", StateToString(previous_->state_)));
    }
  }
#endif  // ENABLE_LOGGING_AND_PROFILING

#ifdef ENABLE_HEAP_PROTECTION
  if (FLAG_protect_heap) {
    if (state_ == EXTERNAL) {
      // We are reentering V8.
      ASSERT((previous_ != NULL) && (previous_->state_ != EXTERNAL));
      Heap::Unprotect();
    } else if ((previous_ == NULL) || (previous_->state_ == EXTERNAL)) {
      // We are leaving V8.
      Heap::Protect();
    }
  }
#endif  // ENABLE_HEAP_PROTECTION
}
#endif  // ENABLE_VMSTATE_TRACKING

} }  // namespace v8::internal

#endif  // V8_VM_STATE_INL_H_