Since you are using parameters, I assume you'll enter a zero for the parameter to be ignored? If so, I would do something like the following:

({empfield}=p_empid and {salaryfield}=p_salary) OR
(p_empid=0 and {salaryfield}=p_salary) OR
({empfield}=p_empid and p_salary=0))

It doesn't matter what you use. You have to identify how the user will specify that a parameter isn't going to be used. In a string I assume that is the empty string. For a date, I don't know.  But then compare that field to the 'no-parameter' value. Here, I changed the second line to compare it to an empty string:

(p_empid='' and {salaryfield}=p_salary)....