Revert "VM: Materialize stub pc-markers (smi 0) eagerly on deoptimization."

runtime/vm/deferred_objects.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/deferred_objects.h"
 
 #include "vm/code_patcher.h"
 #include "vm/compiler.h"
 #include "vm/deopt_instructions.h"
 #include "vm/flags.h"
@@ skipping 143 matching lines @@
   }
 }
 
 
 void DeferredPcMarker::Materialize(DeoptContext* deopt_context) {
   Thread* thread = deopt_context->thread();
   Zone* zone = deopt_context->zone();
   uword* dest_addr = reinterpret_cast<uword*>(slot());
   Function& function = Function::Handle(zone);
   function ^= deopt_context->ObjectAt(index_);
-  // Null case is already handled in DeoptPcMarkerInstr::Execute.
-  ASSERT(!function.IsNull());
+  if (function.IsNull()) {
+    // Callee's PC marker is not used (pc of Deoptimize stub). Set to 0.
+    *dest_addr = 0;
+    return;
+  }
   const Error& error = Error::Handle(zone,
       Compiler::EnsureUnoptimizedCode(thread, function));
   if (!error.IsNull()) {
     Exceptions::PropagateError(error);
   }
   const Code& code = Code::Handle(zone, function.unoptimized_code());
   ASSERT(!code.IsNull());
   ASSERT(function.HasCode());
   const intptr_t pc_marker =
       code.EntryPoint() + Assembler::EntryPointToPcMarkerOffset();
@@ skipping 156 matching lines @@
           OS::PrintErr("    null Field @ offset(%" Pd ") <- %s\n",
                        offset.Value(),
                        value.ToCString());
         }
       }
     }
   }
 }
 
 }  // namespace dart