Disallow dereferencing deferred handles when generating optimized code.

src/isolate.cc

 // Copyright 2012 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
@@ skipping 489 matching lines @@
 
 void Isolate::IterateDeferredHandles(ObjectVisitor* visitor) {
   for (DeferredHandles* deferred = deferred_handles_head_;
        deferred != NULL;
        deferred = deferred->next_) {
     deferred->Iterate(visitor);
   }
 }
 
 
+#ifdef DEBUG
+bool Isolate::IsDeferredHandle(Object** location) {

[Sven Panne, 2013/04/23 06:42:13]

Some comment would be very appropriate here: It is very hard to understand what
the code below is actually doing and why. Even better: Instead of commenting it,
rip it apart into easily understandable methods.

+  for (DeferredHandles* deferred = deferred_handles_head_;
+       deferred != NULL;
+       deferred = deferred->next_) {
+    List<Object**>* blocks = &deferred->blocks_;
+    if (blocks->first() <= location &&
+        location < deferred->first_block_limit_) {
+      return true;
+    }
+    for (int i = 1; i < blocks->length(); i++) {

[Sven Panne, 2013/04/23 06:42:13]

Why 1 and not 0? Could be correct, but I don't have a clue.

+      if (blocks->at(i) <= location &&
+          location <= blocks->at(i) + kHandleBlockSize) {
+        return true;
+      }
+    }
+  }
+  return false;
+}
+#endif  // DEBUG
+
+
 void Isolate::RegisterTryCatchHandler(v8::TryCatch* that) {
   // The ARM simulator has a separate JS stack.  We therefore register
   // the C++ try catch handler with the simulator and get back an
   // address that can be used for comparisons with addresses into the
   // JS stack.  When running without the simulator, the address
   // returned will be the address of the C++ try catch handler itself.
   Address address = reinterpret_cast<Address>(
       SimulatorStack::RegisterCTryCatch(reinterpret_cast<uintptr_t>(that)));
   thread_local_top()->set_try_catch_handler_address(address);
 }
@@ skipping 1230 matching lines @@
   simulator_i_cache_ = NULL;
   simulator_redirection_ = NULL;
 #endif
 
 #ifdef DEBUG
   // heap_histograms_ initializes itself.
   memset(&js_spill_information_, 0, sizeof(js_spill_information_));
   memset(code_kind_statistics_, 0,
          sizeof(code_kind_statistics_[0]) * Code::NUMBER_OF_KINDS);
 
-  allow_compiler_thread_handle_deref_ = true;
-  allow_execution_thread_handle_deref_ = true;
+  compiler_thread_handle_deref_state_ = HandleDereferenceGuard::ALLOW;
+  execution_thread_handle_deref_state_ = HandleDereferenceGuard::ALLOW;
 #endif
 
 #ifdef ENABLE_DEBUGGER_SUPPORT
   debug_ = NULL;
   debugger_ = NULL;
 #endif
 
   handle_scope_data_.Initialize();
 
 #define ISOLATE_INIT_EXECUTE(type, name, initial_value)                        \
@@ skipping 600 matching lines @@
   if (deferred->next_ != NULL) {
     deferred->next_->previous_ = deferred->previous_;
   }
   if (deferred->previous_ != NULL) {
     deferred->previous_->next_ = deferred->next_;
   }
 }
 
 
 #ifdef DEBUG
-bool Isolate::AllowHandleDereference() {
-  if (allow_execution_thread_handle_deref_ &&
-      allow_compiler_thread_handle_deref_) {
+HandleDereferenceGuard::State Isolate::HandleDereferenceGuardState() {
+  if (execution_thread_handle_deref_state_ == HandleDereferenceGuard::ALLOW &&
+      compiler_thread_handle_deref_state_ == HandleDereferenceGuard::ALLOW) {
     // Short-cut to avoid polling thread id.
-    return true;
+    return HandleDereferenceGuard::ALLOW;
   }
   if (FLAG_parallel_recompilation &&
       optimizing_compiler_thread()->IsOptimizerThread()) {
-    return allow_compiler_thread_handle_deref_;
+    return compiler_thread_handle_deref_state_;
   } else {
-    return allow_execution_thread_handle_deref_;
+    return execution_thread_handle_deref_state_;
   }
 }
 
 
-void Isolate::SetAllowHandleDereference(bool allow) {
+void Isolate::SetHandleDereferenceGuardState(
+    HandleDereferenceGuard::State state) {
   if (FLAG_parallel_recompilation &&
       optimizing_compiler_thread()->IsOptimizerThread()) {
-    allow_compiler_thread_handle_deref_ = allow;
+    compiler_thread_handle_deref_state_ = state;
   } else {
-    allow_execution_thread_handle_deref_ = allow;
+    execution_thread_handle_deref_state_ = state;
   }
 }
 #endif
 
 
 HStatistics* Isolate::GetHStatistics() {
   if (hstatistics() == NULL) set_hstatistics(new HStatistics());
   return hstatistics();
 }
 
@@ skipping 12 matching lines @@
 
 #ifdef DEBUG
 #define ISOLATE_FIELD_OFFSET(type, name, ignored)                       \
 const intptr_t Isolate::name##_debug_offset_ = OFFSET_OF(Isolate, name##_);
 ISOLATE_INIT_LIST(ISOLATE_FIELD_OFFSET)
 ISOLATE_INIT_ARRAY_LIST(ISOLATE_FIELD_OFFSET)
 #undef ISOLATE_FIELD_OFFSET
 #endif
 
 } }  // namespace v8::internal