armarmv8

Adding 32 bit register to 64 bit register in ARM

I have code something like this:

mov x24, 5
mov w25, 5
add x24, x24, w25

I am getting a "Missing extend operator at operand 3". I know I could just switch both to 64bit operators but I'm wondering if its still possible to add 32bit numbers and 64bit numbers together like the above

Solution

  • You have to put the optional extend operator
    unsigned:

    add x24, x24, w25, uxtw

    signed:

    add x24, x24, w25, sxtw

    The extension can be:

    uxtb: unsigned 8bit
sxtb: signed 8bit
uxth: unsigned 16bit
sxth: signed 16bit
uxtw: unsigned 32bit
sxtw: signed 32bit