Synthesis cant send variable from LoopBigin to LoopEnd using 1 FRAM

[BasicEC]

Following test fails

unitTestCase "autosynthesis successfully completed" def $ do
                  setNetwork $
                      Bus.defineNetwork "net1" ASync $ do
                          Bus.addCustom "fram1" (framWithSize 32) FramIO
                          Bus.add "accum1" AccumIO
                  setBusType pInt
                  assignLua
                      [__i|
                          function sum(x1, x2)
                              x1 = x1 + x2
                              sum(x1, x2)
                          end
                          sum(1,2)
                          |]
                  synthesizeAndCoSim

Outcome:

autosynthesis successfully completed: FAIL (0.20s)
          test/NITTA/Model/ProcessorUnits/Tests/DSL/Tests.hs:361:
          synthesis is not complete: fromList ["x2^0#1","x2^0#1@buf"]

It is bot a bug, but restricted functions. Support of self-sending can help here.

[BasicEC]

Here the problem is that we cant send x2 from LoopBegin to LoopEnd using one FRAM.
Here's DFG at the moment when synthesis stuck:

[BasicEC]

The point is that the variable is already in FRAM, so I think we can avoid resending. @ryukzak is it right?