Fix unsafe use of register in virtual frame.

src/virtual-frame.cc

 // Copyright 2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 175 matching lines @@
     ASSERT(!cgen_->allocator()->is_used(result));
   }
   return result;
 }
 
 
 // Make the type of the element at a given index be MEMORY.
 void VirtualFrame::SpillElementAt(int index) {
   if (!elements_[index].is_valid()) return;
 
+  SyncElementAt(index);
   if (elements_[index].is_register()) {
     Unuse(elements_[index].reg());
   }
-  SyncElementAt(index);
   // The element is now in memory.
   elements_[index] = FrameElement::MemoryElement();
 }
 
 
 // Clear the dirty bits for the range of elements in [begin, end).
 void VirtualFrame::SyncRange(int begin, int end) {
   ASSERT(begin >= 0);
   ASSERT(end <= elements_.length());
   for (int i = begin; i < end; i++) {
@@ skipping 300 matching lines @@
     if (frame_registers_.count(i) != other->frame_registers_.count(i)) {
       return false;
     }
   }
 
   return true;
 }
 #endif
 
 } }  // namespace v8::internal