问题
i need to find a way to check number of bits that is current on (1) in the ax register. i was thinking to use in shl or shr, but i do not know how exactly i suppose to use them. this is my code so far:
org 100h
mov ax, 0xffffh
;shr ax TO DO
int 16h
ret
i red in some place that the shift right function can move the bits to the right. so i might should use it by try to "push" the 16 bits to the right every time, and then check the LSB 1 or 0 flag? it sound to me as good idea.
回答1:
Use the popcnt instruction:
popcnt bx,ax
This sets bx to the number of bits set in ax. You need a somewhat recent CPU for this instruction to be available though.
回答2:
The shifted bit goes in the CF(carry flag) so one solution is that everytime after each shift you check that if CF=1 then increment a count variable that will tell the num of ON bits at the end.
来源：https://stackoverflow.com/questions/47161950/check-number-of-bits-on-in-ax