Attempt to reduce performance penalty for logging and profiling

src/log-inl.h

Index: src/log-inl.h
===================================================================
--- src/log-inl.h	(revision 0)
+++ src/log-inl.h	(revision 0)
@@ -0,0 +1,126 @@
+// Copyright 2006-2009 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef V8_LOG_INL_H_
+#define V8_LOG_INL_H_
+
+#include "log.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_LOGGING_AND_PROFILING
+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) {
+  if (!Logger::is_logging()) {
+    return;
+  }
+
+  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;
+  previous_ = Logger::current_state_;
+  Logger::current_state_ = this;
+
+  if (FLAG_log_state_changes) {
+    LOG(UncheckedStringEvent("Entering", StateToString(state_)));
+    if (previous_ != NULL) {
+      LOG(UncheckedStringEvent("From", StateToString(previous_->state_)));
+    }
+  }
+
+#ifdef ENABLE_HEAP_PROTECTION
+  if (FLAG_protect_heap && previous_ != NULL) {
+    if (state_ == EXTERNAL) {
+      // We are leaving V8.
+      ASSERT(previous_->state_ != EXTERNAL);
+      Heap::Protect();
+    } else if (previous_->state_ == EXTERNAL) {
+      // We are entering V8.
+      Heap::Unprotect();
+    }
+  }
+#endif
+}
+
+
+VMState::~VMState() {
+  if (disabled_) return;
+  Logger::current_state_ = previous_;
+
+  if (FLAG_log_state_changes) {
+    LOG(UncheckedStringEvent("Leaving", StateToString(state_)));
+    if (previous_ != NULL) {
+      LOG(UncheckedStringEvent("To", StateToString(previous_->state_)));
+    }
+  }
+
+#ifdef ENABLE_HEAP_PROTECTION
+  if (FLAG_protect_heap && previous_ != NULL) {
+    if (state_ == EXTERNAL) {
+      // We are reentering V8.
+      ASSERT(previous_->state_ != EXTERNAL);
+      Heap::Unprotect();
+    } else if (previous_->state_ == EXTERNAL) {
+      // We are leaving V8.
+      Heap::Protect();
+    }
+  }
+#endif
+}
+#endif
+
+
+} }  // namespace v8::internal
+
+#endif  // V8_LOG_INL_H_