$END_PROLOGUE marks the end of a routine prologue instruction
    sequence that you code yourself. The prologue instruction
    sequence begins with the first instruction of the routine. There
    can only be one prologue instruction sequence in a routine. The
    prologue is described in detail in the OpenVMS Calling Standard.

    You invoke $END_PROLOGUE after the last instruction in the
    routine prologue code. The last instruction in the routine
    prologue is the one that updates FP (R29, the frame pointer)
    and makes the frame become current. You must use this macro
    when the routine type is stack or register and you specify
    STANDARD_PROLOGUE=FALSE to the $ROUTINE macro.