ASM Community

So you want to and something with something else?

You sure you've looked for a way to do this?

The mnemonic and performs the bitwise operation and, its not rocket science.
Similarly the test operation performs a bitwise and, except it doesn't store the result it only sets the flags (test for non-zero)

Alternatively as you are checking for the last byte being set how about these:

; assume al holds the byte to check

or al, al

js somewhere ; jump if bit 7 is set - al unchanged



test al, 80h

jnz somewhere ; jump if bit 7 is set - al unchanged



test al, 80h

js somewhere ; jump if bit 7 is set - al unchanged



and al, 80h

jnz somewhere ; jump if bit 7 is set - al = 80h if bit 7 set, else al = 00h



and al, 0FFh

js somewhere ; jump if bit 7 is set - al unchanged



shl al, 1

jc somewhere ; jump if bit 7 was set - al = (al && 7Fh) * 2



xor al, 80h

jns somewhere ; jump if bit 7 was set - al = al with bit 7 inverted



not al

jns somewhere ; jump if bit 7 was set - al = ~al

There are a whole lot more if I can use sub, add, cmp, and the rest of the instructions...
Are you sure you looked for this information?

Mirno