SQL Server Short-circuits WHERE Condition Evaluation

Hi I am trying to create stored proc and having some performance issue.

Here is the requirement,

Stored Proc parameters A,B
A is required.
B is optional. The default value for B is 0.

Here is the code inside stored proc:

IF (B = 0)
SET B = 1


SELECT * FROM TABLE1
INNER JOIN TABLE2 ON TABLE1.Column1 = TABLE2.Column1
WHERE A= 2008
AND (table2.ColumnB = B or 1 = B)

If I am passing B as 20 I am having performance issue to pull the data.
If I replace B with any other number the query is working fine.