GCSSTR Guarded Control Stack store register This instruction stores a doubleword from a register to memory. The address that is used for the store is calculated from a base register. 1 1 0 1 1 0 0 1 0 0 0 1 1 1 1 1 0 0 0 0 1 1 GCSSTR <Xt>, [<Xn|SP>] if !IsFeatureImplemented(FEAT_GCS) then EndOfDecode(Decode_UNDEF); end; let t : integer{} = UInt(Rt); let n : integer{} = UInt(Rn); <Xt> Is the 64-bit name of the general-purpose register to be transferred, encoded in the "Rt" field. <Xn|SP> Is the 64-bit name of the general-purpose base register or stack pointer, encoded in the "Rn" field. var address : bits(64); let effective_el : bits(2) = PSTATE.EL; if effective_el == PSTATE.EL then CheckGCSSTREnabled(); end; let privileged : boolean = effective_el != EL0; let accdesc : AccessDescriptor = CreateAccDescGCS(MemOp_STORE, privileged); if n == 31 then CheckSPAlignment(); address = SP{64}(); else address = X{64}(n); end; Mem{64}(address, accdesc) = X{64}(t); 2026-03-12 12:23:09 2025-09_rel_asl1