HELP: Questions on unshare_expr

[Qing Zhao <qing.zhao@oracle.com>]

Hi, 

I have some questions on using the utility routine “unshare_expr”:

From my understanding, there should be NO shared nodes in a GENERIC function. 
 Otherwise, gimplication might fail. 

Therefore, when we insert new tree nodes manually into the GENERIC function, we should
Make sure there is no shared nodes introduced. 

1. Is the above understanding correct?
2. Is there any tool to check there is no shared nodes in the GENERIC function?
3. Are there any tree nodes that are allowed to be shared in a GENERIC function? If so, what are they?

4. For the following:

If both “op1” and “op2” are existing tree nodes in the current GENERIC function, 
and we will insert a new tree node:

tree  new_tree = build2 (CODE, TYPE, op1, op2)


Should we add “unshare_expr” on both “op1” and “op2” as:

Tree new_tree = build2 (CODE, TYPE, unshare_expr (op1), unshare_expr (op2))
?

If op2 is a node that is allowed to be shared, whether the additional “unshare_expr” on it trigger any potential problem?

Thanks a lot for your help.

Qing