I have found a potential bug with the loop unrolling of a triangular loop. The example is attached.
[marianne@MarianneFedora15 ~]$ ifort -v
ifort version 13.0.1
[marianne@MarianneFedora15 ~]$ ifort loopUnrolltest.f90
[marianne@MarianneFedora15 ~]$ ./a.out
1000000. 1000000. 3.3835000E+07 0.0000000E+00 0.0000000E+00
0.0000000E+00
[marianne@MarianneFedora15 ~]$ ifort -unroll0 loopUnrolltest.f90
[marianne@MarianneFedora15 ~]$ ./a.out
3.3835000E+07 3.3835000E+07 3.3835000E+07 3.3835000E+07 3.3835000E+07
3.3835000E+07