Sequence of passes in a compilation

Dear all:

I have a question: Assume S1 and S2 be two sequence of passes which
are not equal, i.e., S1 is different from S2. Let there are two
programs P1 and P2. Is it possible that P1 can be compiled
successfully using S1 but not with S2. Similarly P2 can be compiled
successfully with S2 but not with S1.

I am getting this when I am changing the sequence of GCC using the
SPEC benchmark.

Thanks for your help.
Abid