well you did not find false path.
your synthesis has some timing issue, so two possibilities:
1- the designer claims this path is false, so you could add this path to false in your SDC.
2- the designer claims this path is true, then you have a timing issue, to solve by pipeline or rewrite RTL to push combinational logic before or after flops.
Thanks.
Then how can designer know the designer's rtl design have false paths?
Even they have mistake and incorrect infomations.
How can make this issues?
Then it seems to be definite the false path.
Actually, how many case exist the false path?
I am designer but i don't have memory what claim to synthesis designers.
It is really design dependant, some design does not have any false-path, because everything is pipeline.
Normaly the synthesis does not request any false path, only to reach timing, that could help.