  Energy bands of non-Hermitian crystalline systems are described in terms of
the generalized Brillouin zone (GBZ) having unique features which are absent in
Hermitian systems. In this paper, we show that in one-dimensional non-Hermitian
systems with both sublattice symmetry and time-reversal symmetry such as the
non-Hermitian Su-Schrieffer-Heeger model, a topological semimetal phase with
exceptional points is stabilized by the unique features of the GBZ. Namely,
under a change of a system parameter, the GBZ is deformed so that the system
remains gapless. It is also shown that each energy band is divided into three
regions, depending on the symmetry of the eigenstates, and the regions are
separated by the cusps and the exceptional points in the GBZ.
