The register structure is the same for windowed and call0 ABIs because
currently linux kernel internally requires windowed registers, so they
are always present.
gdb/gdbserver/
2017-03-27 Max Filippov <jcmvbkbc@gmail.com>
* linux-xtensa-low.c (xtensa_fill_gregset): Call collect_register
for all registers in a0_regnum..a0_regnum + C0_NREGS range.
(xtensa_store_gregset): Call supply_register for all registers in
a0_regnum..a0_regnum + C0_NREGS range.