VM: Fix race between background compiler and guarded cid update.

runtime/vm/parser.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/parser.h"
 #include "vm/flags.h"
 
 #ifndef DART_PRECOMPILED_RUNTIME
 
 #include "lib/invocation_mirror.h"
@@ skipping 143 matching lines @@
   // finalized yet.
   return a.raw();
 }
 
 
 void ParsedFunction::AddToGuardedFields(const Field* field) const {
   if ((field->guarded_cid() == kDynamicCid) ||
       (field->guarded_cid() == kIllegalCid)) {
     return;
   }
+
   for (intptr_t j = 0; j < guarded_fields_->length(); j++) {
-    if ((*guarded_fields_)[j]->raw() == field->raw()) {
+    const Field* other = (*guarded_fields_)[j];
+    if (field->Original() == other->Original()) {
+      // Abort background compilation early if the guarded state of this field
+      // has changed during compilation. We will not be able to commit
+      // the resulting code anyway.
+      if (Compiler::IsBackgroundCompilation()) {
+        if (!other->IsConsistentWith(*field)) {
+          Compiler::AbortBackgroundCompilation(Thread::kNoDeoptId,
+              "Field's guarded state changed during compilation");
+        }
+      }
       return;
     }
   }
-  guarded_fields_->Add(&Field::ZoneHandle(Z, field->Original()));
+
+  // Note: the list of guarded fields must contain copies during background
+  // compilation because we will look at their guarded_cid when copying
+  // the array of guarded fields from callee into the caller during
+  // inlining.
+  ASSERT(!field->IsOriginal() || Thread::Current()->IsMutatorThread());
+  guarded_fields_->Add(&Field::ZoneHandle(Z, field->raw()));
 }
 
 
 LocalVariable* ParsedFunction::EnsureExpressionTemp() {
   if (!has_expression_temp_var()) {
     LocalVariable* temp =
         new (Z) LocalVariable(function_.token_pos(),
                               Symbols::ExprTemp(),
                               Object::dynamic_type());
     ASSERT(temp != NULL);
@@ skipping 14320 matching lines @@
     const ArgumentListNode& function_args,
     const LocalVariable* temp_for_last_arg,
     bool is_super_invocation) {
   UNREACHABLE();
   return NULL;
 }
 
 }  // namespace dart
 
 #endif  // DART_PRECOMPILED_RUNTIME