Implement verification of context separation.

src/mark-compact.cc

Index: src/mark-compact.cc
diff --git a/src/mark-compact.cc b/src/mark-compact.cc
index 6c16f61d25f0f1c80f5a62af7121230698b5835c..b875d1519adac321df36cd3345bf64968333210c 100644
--- a/src/mark-compact.cc
+++ b/src/mark-compact.cc
@@ -223,6 +223,99 @@ static void VerifyEvacuation(Heap* heap) {
   VerifyEvacuationVisitor visitor;
   heap->IterateStrongRoots(&visitor, VISIT_ALL);
 }
+
+
+class VerifyGlobalContextSeparationVisitor: public ObjectVisitor {
+ public:
+  VerifyGlobalContextSeparationVisitor() : current_global_context_(NULL) {}
+
+  void VisitPointers(Object** start, Object** end) {
+    for (Object** current = start; current < end; current++) {
+      if ((*current)->IsHeapObject()) {
+        HeapObject* object = HeapObject::cast(*current);
+        if (object->IsString()) continue;
+        switch (object->map()->instance_type()) {
+          case JS_FUNCTION_TYPE:
+            CheckContext(JSFunction::cast(object)->context());
+            break;
+          case JS_GLOBAL_PROXY_TYPE:
+            CheckContext(JSGlobalProxy::cast(object)->context());
+            break;
+          case JS_GLOBAL_OBJECT_TYPE:
+          case JS_BUILTINS_OBJECT_TYPE:
+            CheckContext(GlobalObject::cast(object)->global_context());
+            break;
+          case JS_ARRAY_TYPE:
+          case JS_DATE_TYPE:
+          case JS_OBJECT_TYPE:
+          case JS_REGEXP_TYPE:
+            VisitPointer(HeapObject::RawField(object, JSObject::kMapOffset));
+            break;
+          case MAP_TYPE:
+            VisitPointer(HeapObject::RawField(object, Map::kPrototypeOffset));
+            VisitPointer(HeapObject::RawField(object, Map::kConstructorOffset));
+            break;
+          case FIXED_ARRAY_TYPE:
+            if (object->IsContext()) {
+              CheckContext(object);
+            } else {
+              FixedArray* array = FixedArray::cast(object);
+              int length = array->length();
+              // Set array length to zero to prevent cycles while iterating
+              // over array bodies, this is easier than intrusive marking.
+              array->set_length(0);
+              array->IterateBody(
+                  FIXED_ARRAY_TYPE, FixedArray::SizeFor(length), this);
+              array->set_length(length);
+            }
+            break;
+          case JS_GLOBAL_PROPERTY_CELL_TYPE:
+          case JS_PROXY_TYPE:
+          case JS_VALUE_TYPE:
+          case TYPE_FEEDBACK_INFO_TYPE:
+            object->Iterate(this);
+            break;
+          case ACCESSOR_INFO_TYPE:
+          case BYTE_ARRAY_TYPE:
+          case CALL_HANDLER_INFO_TYPE:
+          case CODE_TYPE:
+          case FIXED_DOUBLE_ARRAY_TYPE:
+          case HEAP_NUMBER_TYPE:
+          case INTERCEPTOR_INFO_TYPE:
+          case ODDBALL_TYPE:
+          case SCRIPT_TYPE:
+          case SHARED_FUNCTION_INFO_TYPE:
+            break;
+          default:
+            UNREACHABLE();
+        }
+      }
+    }
+  }
+
+ private:
+  void CheckContext(Object* context) {
+    if (!context->IsContext()) return;
+    Context* global_context = Context::cast(context)->global_context();
+    if (current_global_context_ == NULL) {
+      current_global_context_ = global_context;
+    } else {
+      CHECK_EQ(current_global_context_, global_context);
+    }
+  }
+
+  Context* current_global_context_;
+};
+
+
+static void VerifyGlobalContextSeparation(Heap* heap) {
+  HeapObjectIterator it(heap->code_space());
+
+  for (Object* object = it.Next(); object != NULL; object = it.Next()) {
+    VerifyGlobalContextSeparationVisitor visitor;
+    Code::cast(object)->CodeIterateBody(&visitor);
+  }
+}
 #endif
 
 
@@ -296,6 +389,12 @@ void MarkCompactCollector::CollectGarbage() {
 
   if (!FLAG_collect_maps) ReattachInitialMaps();
 
+#ifdef DEBUG
+  if (FLAG_verify_global_context_separation) {
+    VerifyGlobalContextSeparation(heap_);
+  }
+#endif
+
   Finish();
 
   tracer_ = NULL;