The following part of jjsat commit here https://github.com/jjsat/ags/commit/22221b6d3ebffdd7c7e32e5ccb95a590e5a8307a#diff-4db3d150dec6fcd9180c42130e5d06d6f11649403d1a1d46700564785284e0dbR1456-R1481
We see that load.sp.offs was used to load the value of the stack pointer (SP) with an offset, moving the stack pointer up or down.
But then, after the commit, it changed from
case SCMD_LOADSPOFFS:
inst->registers[SREG_MAR] = inst->registers[SREG_SP] - arg1;