The paper “Gimli: a cross-platform permutation” contains the following information:
Occasionally (after rounds 24, 20, 16, etc.) Gimli adds an asymmetric constant to entry 0 of the first row. This constant has many bits set (it is essentially the golden ratio
0x9e3779b9, as used in TEA), and is not close to any of its nontrivial rotations (never fewer than 12 bits different)
What does the term “nontrivial rotation” mean? How to distinguish a “nontrivial” rotation from a “trivial” one?