GCSPUSHM Guarded Control Stack push This instruction decrements the current Guarded Control Stack pointer register by the size of a Guarded control procedure return record and stores an entry to the Guarded Control Stack. SYS 1 1 0 1 0 1 0 1 0 0 0 0 1 0 1 1 0 1 1 1 0 1 1 1 0 0 0 GCSPUSHM <Xt> SYS #3, C7, C7, #0, <Xt> Unconditionally <Xt> Is the 64-bit name of the general-purpose source register, encoded in the "Rt" field.