bt{wl} imm8, r/m[16|32] bt{wl} reg[16|32], r/m[16|32]
BIT [LeftSRC, RightSRC] -> CF
The bit indicated by the first operand (base) and the second operand (offset) are saved by bt into CF (carry flag).
btl $253, 4(%edi) btl %edx, 4(%edi)