5.60 · exercise

Fill in the Blank: Subroutine Linkage

Fill in the missing mnemonics and registers that let an AArch64 subroutine be called, build a frame, return a result, and hand back the registers it borrowed.

0 of 5 correct

Fill in the Blank

Call the subroutine print_sum so that control comes back to the following instruction when it finishes.

print_sum

Fill in the Blank

Open the stack frame: allocate 16 bytes and save the frame pointer and the link register into them with a single instruction.

x29, x30, [sp, -16]!

Fill in the Blank

The caller has reserved space at sp for a structure the subroutine will fill in. Complete the line that passes that address in the indirect result location register.

mov , sp

Fill in the Blank

square calls no other subroutine, so it saves nothing and builds no frame. Complete its final line.

// branch back to the address in x30

Fill in the Blank

A subroutine has to keep a running total across a bl to another subroutine. Complete the mov that parks the total in the lowest callee-saved register.

mov , x0