Disconnects code objects from infrequently used unoptimized functions.

runtime/vm/code_generator.cc

 // Copyright (c) 2013, 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/code_generator.h"
 
 #include "vm/assembler.h"
 #include "vm/ast.h"
 #include "vm/bigint_operations.h"
 #include "vm/code_patcher.h"
@@ skipping 1400 matching lines @@
   if (frame->IsEntryFrame()) {
     // Since function's current code is always unpatched, the entry frame always
     // calls to unpatched code.
     UNREACHABLE();
   }
   ASSERT(frame->IsDartFrame());
   const Code& caller_code = Code::Handle(frame->LookupDartCode());
   ASSERT(caller_code.is_optimized());
   const Function& target_function = Function::Handle(
       caller_code.GetStaticCallTargetFunctionAt(frame->pc()));
-  const Code& target_code = Code::Handle(target_function.CurrentCode());
-  CodePatcher::PatchStaticCallAt(frame->pc(), caller_code,
-                                 target_code.EntryPoint());
-  caller_code.SetStaticCallTargetCodeAt(frame->pc(), target_code);
+
+  // Check whether the code object has been detached from the target function.
+  // If it has been detached, reattach it.
+  Code& target_code = Code::Handle();
+  if (target_function.HasCode()) {
+    target_code ^= target_function.CurrentCode();
+    CodePatcher::PatchStaticCallAt(frame->pc(), caller_code,
+                                   target_code.EntryPoint());
+    caller_code.SetStaticCallTargetCodeAt(frame->pc(), target_code);
+  } else {
+    ASSERT(target_function.unoptimized_code() == Code::null());
+    target_code ^= caller_code.GetStaticCallTargetCodeAt(frame->pc());
+    ASSERT(!target_code.IsNull());
+    ASSERT(!target_code.is_optimized());
+    target_function.ReattachCode(target_code);
+  }
   if (FLAG_trace_patching) {
     OS::PrintErr("FixCallersTarget: patching from %#" Px " to '%s' %#" Px "\n",
         frame->pc(),
         Function::Handle(target_code.function()).ToFullyQualifiedCString(),
         target_code.EntryPoint());
   }
   arguments.SetReturn(target_code);
 }
 
 
@@ skipping 268 matching lines @@
   field.UpdateCid(cid);
   intptr_t list_length = Field::kNoFixedLength;
   if ((field.guarded_cid() != kDynamicCid) &&
       field.is_final() && RawObject::IsBuiltinListClassId(cid)) {
     list_length = GetListLength(value);
   }
   field.UpdateLength(list_length);
 }
 
 }  // namespace dart