Calling the same function more than once with the same arguments

I'm building a function caller() in which a certain function called()
will be called many times in from clauses with the same arguments and
I'm wondering if is there a performance penalty for that or if the sql
engine is smart enough to call called() only once.

I tried to substitute called() in the from clauses for a temporary
table created first in caller() but it refuses to build caller() with
the message "ERROR:  relation "temp_table_name" does not exist". It
does not exist in build time but it will exist in run time.

Regards, Clodoaldo Pinto