Canonicalize handles for optimized compilation.

src/handles.cc

 // Copyright 2012 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/handles.h"
 
+#include "src/address-map.h"
 #include "src/base/logging.h"
+#include "src/identity-map.h"
 #include "src/objects-inl.h"
 
 namespace v8 {
 namespace internal {
 
 #ifdef DEBUG
 bool HandleBase::IsDereferenceAllowed(DereferenceCheckMode mode) const {
   DCHECK_NOT_NULL(location_);
   Object* object = *location_;
   if (object->IsSmi()) return true;
@@ skipping 30 matching lines @@
 
 
 Object** HandleScope::Extend(Isolate* isolate) {
   HandleScopeData* current = isolate->handle_scope_data();
 
   Object** result = current->next;
 
   DCHECK(result == current->limit);
   // Make sure there's at least one scope on the stack and that the
   // top of the scope stack isn't a barrier.
-  if (!Utils::ApiCheck(current->level != 0,
+  if (!Utils::ApiCheck(current->level != current->sealed_level,
                        "v8::HandleScope::CreateHandle()",
                        "Cannot create a handle without a HandleScope")) {
     return NULL;
   }
   HandleScopeImplementer* impl = isolate->handle_scope_implementer();
   // If there's more room in the last block, we use that. This is used
   // for fast creation of scopes after scope barriers.
   if (!impl->blocks()->is_empty()) {
     Object** limit = &impl->blocks()->last()[kHandleBlockSize];
     if (current->limit != limit) {
@@ skipping 41 matching lines @@
 Address HandleScope::current_next_address(Isolate* isolate) {
   return reinterpret_cast<Address>(&isolate->handle_scope_data()->next);
 }
 
 
 Address HandleScope::current_limit_address(Isolate* isolate) {
   return reinterpret_cast<Address>(&isolate->handle_scope_data()->limit);
 }
 
 
+CanonicalHandleScope::CanonicalHandleScope(Isolate* isolate)
+    : isolate_(isolate) {
+  HandleScopeData* handle_scope_data = isolate_->handle_scope_data();
+  prev_canonical_scope_ = handle_scope_data->canonical_scope;
+  handle_scope_data->canonical_scope = this;
+  root_index_map_ = new RootIndexMap(isolate);
+  identity_map_ = new IdentityMap<Object**>(isolate->heap(), &zone_);
+  canonical_level_ = handle_scope_data->level;
+}
+
+
+CanonicalHandleScope::~CanonicalHandleScope() {
+  delete root_index_map_;
+  delete identity_map_;
+  isolate_->handle_scope_data()->canonical_scope = prev_canonical_scope_;
+}
+
+
+Object** CanonicalHandleScope::Lookup(Object* object) {
+  DCHECK_LE(canonical_level_, isolate_->handle_scope_data()->level);
+  if (isolate_->handle_scope_data()->level != canonical_level_) {
+    // We are in an inner handle scope. Do not canonicalize since we will leave
+    // this handle scope while still being in the canonical scope.
+    return HandleScope::CreateHandle(isolate_, object);
+  }
+  if (object->IsHeapObject()) {
+    int index = root_index_map_->Lookup(HeapObject::cast(object));
+    if (index != RootIndexMap::kInvalidRootIndex) {
+      return isolate_->heap()
+          ->root_handle(static_cast<Heap::RootListIndex>(index))
+          .location();
+    }
+  }
+  Object*** entry = identity_map_->Get(object);
+  if (*entry == nullptr) {
+    // Allocate new handle location.
+    *entry = HandleScope::CreateHandle(isolate_, object);
+  }
+  return reinterpret_cast<Object**>(*entry);
+}
+
+
 DeferredHandleScope::DeferredHandleScope(Isolate* isolate)
     : impl_(isolate->handle_scope_implementer()) {
   impl_->BeginDeferredScope();
   HandleScopeData* data = impl_->isolate()->handle_scope_data();
   Object** new_next = impl_->GetSpareOrNewBlock();
   Object** new_limit = &new_next[kHandleBlockSize];
   DCHECK(data->limit == &impl_->blocks()->last()[kHandleBlockSize]);
   impl_->blocks()->Add(new_next);
 
 #ifdef DEBUG
@@ skipping 20 matching lines @@
   data->next = prev_next_;
   data->limit = prev_limit_;
 #ifdef DEBUG
   handles_detached_ = true;
 #endif
   return deferred;
 }
 
 }  // namespace internal
 }  // namespace v8