Added command line flag --sync_with_push (default: true) to...

src/x64/virtual-frame-x64.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 865 matching lines @@
 
 // Clear the dirty bits for the range of elements in
 // [min(stack_pointer_ + 1,begin), end].
 void VirtualFrame::SyncRange(int begin, int end) {
   ASSERT(begin >= 0);
   ASSERT(end < element_count());
   // Sync elements below the range if they have not been materialized
   // on the stack.
   int start = Min(begin, stack_pointer_ + 1);
 
-  // If positive we have to adjust the stack pointer.
-  int delta = end - stack_pointer_;
-  if (delta > 0) {
-    stack_pointer_ = end;
-    __ subq(rsp, Immediate(delta * kPointerSize));
-  }
-
+  // Emit normal 'push' instructions for elements above stack pointer
+  // and use mov instructions if we are below stack pointer.
   for (int i = start; i <= end; i++) {
-    if (!elements_[i].is_synced()) SyncElementBelowStackPointer(i);
+    if (!elements_[i].is_synced()) {
+      if (i <= stack_pointer_) {
+        SyncElementBelowStackPointer(i);
+      } else {
+        SyncElementByPushing(i);
+      }
+    }
   }
 }
 
 
 Result VirtualFrame::InvokeBuiltin(Builtins::JavaScript id,
                                    InvokeFlag flag,
                                    int arg_count) {
   PrepareForCall(arg_count, arg_count);
   ASSERT(cgen()->HasValidEntryRegisters());
   __ InvokeBuiltin(id, flag);
@@ skipping 147 matching lines @@
   // Grow the expression stack by handler size less one (the return
   // address is already pushed by a call instruction).
   Adjust(kHandlerSize - 1);
   __ PushTryHandler(IN_JAVASCRIPT, type);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal