Regression check for optimizing simplify instruction pass.

A pair (sub, neg) should not be transforemd to (sub) for
fp calculation because we can lose the sign of zero for
the following expression:
  - ( A - B ) != B - A ; if B == A

Addition or subtraction with fp zero should not be eliminated
because:
  -0.0 + 0.0 = 0.0
  -0.0 - -0.0 = 0.0
