Disconnects code objects from infrequently used unoptimized functions.

runtime/vm/code_generator.cc

Index: runtime/vm/code_generator.cc
===================================================================
--- runtime/vm/code_generator.cc	(revision 29013)
+++ runtime/vm/code_generator.cc	(working copy)
@@ -1418,10 +1418,22 @@
   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(),