1Regression check for optimizing simplify instruction pass.
2
3A pair (sub, neg) should not be transforemd to (sub) for
4fp calculation because we can lose the sign of zero for
5the following expression:
6  - ( A - B ) != B - A ; if B == A
7
8Addition or subtraction with fp zero should not be eliminated
9because:
10  -0.0 + 0.0 = 0.0
11  -0.0 - -0.0 = 0.0
12