What's the meaing of "Incorrect sharing of tree nodes"?

[Haifeng He]

Hi, all

I wrote a pass that will instrument some instructions in the given
program. However,
the pass failed to pass "TODO_verify_stmts". The error message said
"incorrect sharing of tree nodes".
What's the meaning of this error message? If I just ignore
"TODO_verify_stmts", it seems the instrumented program can still run.
Can anybody give me some idea about the error?

Thanks
Haifeng

---------------------------------------------------------------
The particular failed test program is like the following:
Original gimple code:
  D.2582 = l->next

Instrumented code
 +D.2585 = l->next
 +D.2586 = (int) D.2585
D.2582 = l->next
 +_my_call(D.2586)

The error message is:
error: incorrect sharing of tree nodes
D.2582 = lD.2580->nextD.2569

lD.2580->nextD.2569