Save the entry context for a function that has captured loop variables.

runtime/vm/flow_graph_builder.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/flow_graph_builder.h"
 
 #include "lib/invocation_mirror.h"
 #include "vm/ast_printer.h"
 #include "vm/bit_vector.h"
 #include "vm/class_finalizer.h"
 #include "vm/exceptions.h"
 #include "vm/flags.h"
 #include "vm/flow_graph.h"
 #include "vm/flow_graph_compiler.h"
 #include "vm/heap.h"
 #include "vm/il_printer.h"
 #include "vm/intermediate_language.h"
 #include "vm/isolate.h"
 #include "vm/longjump.h"
 #include "vm/object.h"
+#include "vm/object_store.h"
 #include "vm/os.h"
 #include "vm/parser.h"
 #include "vm/resolver.h"
 #include "vm/scopes.h"
 #include "vm/stack_frame.h"
 #include "vm/stub_code.h"
 #include "vm/symbols.h"
 #include "vm/token.h"
 #include "vm/zone.h"
 
@@ skipping 3426 matching lines @@
           Do(BuildStoreLocal(parameter, load));
           // Write NULL to the source location to detect buggy accesses and
           // allow GC of passed value if it gets overwritten by a new value in
           // the function.
           Value* null_constant =
               Bind(new ConstantInstr(Object::ZoneHandle()));
           Do(BuildStoreLocal(*temp_local, null_constant));
         }
       }
     }
+  } else if (MustSaveRestoreContext(node)) {
+    // Even when the current scope has no context variables, we may
+    // still need to save the current context if, for example, there
+    // are loop scopes below this which will allocate a context
+    // object.
+    BuildSaveContext(
+        *owner()->parsed_function()->saved_entry_context_var());
+    AddInstruction(
+        new StoreContextInstr(Bind(new ConstantInstr(Object::ZoneHandle(
+            Isolate::Current()->object_store()->empty_context())))));
   }
 
   // This check may be deleted if the generated code is leaf.
   // Native functions don't need a stack check at entry.
   const Function& function = owner()->parsed_function()->function();
   if ((node == owner()->parsed_function()->node_sequence()) &&
       !function.is_native()) {
     // Always allocate CheckOverflowInstr so that deopt-ids match regardless
     // if we inline or not.
     CheckStackOverflowInstr* check =
@@ skipping 47 matching lines @@
     node->NodeAt(i++)->Visit(&for_effect);
     Append(for_effect);
     if (!is_open()) {
       // E.g., because of a JumpNode.
       break;
     }
   }
 
   if (is_open()) {
     if (MustSaveRestoreContext(node)) {
-      ASSERT(num_context_variables > 0);
       BuildRestoreContext(
           *owner()->parsed_function()->saved_entry_context_var());
     } else if (num_context_variables > 0) {
       UnchainContexts(1);
     }
   }
 
   // If this node sequence is labeled, a break out of the sequence will have
   // taken care of unchaining the context.
   if (nested_block.break_target() != NULL) {
@@ skipping 354 matching lines @@
                                   function.token_pos(),
                                   LanguageError::kError,
                                   Heap::kNew,
                                   "FlowGraphBuilder Bailout: %s %s",
                                   String::Handle(function.name()).ToCString(),
                                   reason));
   Isolate::Current()->long_jump_base()->Jump(1, error);
 }
 
 }  // namespace dart