PowerOf2 MMIX

powerOf2.mms

        LOC #100

% Entry point
Main    SETI $1,20
        PUSHJ $0,IntegerPowerOfTwo  % compute 2^$1
        JMP Done

% ----------------------------------------------------
% compute the power of 2 to the n where n is in $1
% result is returned in $0
% ----------------------------------------------------
IntegerPowerOfTwo
        SETI $0, 0  % initialize counter to 0
        SETI $2, 1
CountLoop
        CMP     $5,$0,$1
        BZ      $5,CountEnd
        MULUI   $2,$2,2  % double the value in $2 each iteration
        ADDUI   $0,$0,1
        JMP     CountLoop
CountEnd
        SET     $0,$2
        POP     1,0  % return to caller (rJ)

Done
        TRAP    0,Halt,0