5.20 · exercise

Fizzbuzz, by hand

The classic interview question, on a machine with no remainder instruction: print the numbers 1 through a limit, except say fizz for multiples of 3, buzz for multiples of 5, and fizzbuzz for multiples of both. The starter reads the limit.

AArch64 has division but no remainder instruction. The usual way around that is udiv then msub: divide, multiply the quotient back, subtract, and what is left is the remainder.

What is checked

  • all fifteen lines in order for the 15 in the stdin box
  • the program exits cleanly
  • the remainders come from msub, not from a lookup
  • the same holds for other limits you do not see; a limit of 0 prints nothing

specification

stdin15
stdoutprints the right output
exitexits with the right code
sourceuses msub
sourceuses udiv
hiddenright output and exit code on 4 more inputs you do not see

We run your program on the input above and on the hidden ones, and compare what it does. Nothing is matched against a stored solution.

loading editor...

regfile

N clearZ clearC clearV clear

x0–x30 are the integer registers.

X0arg00x0000000000000000
X1arg10x0000000000000000
X2arg20x0000000000000000
X3arg30x0000000000000000
X4arg40x0000000000000000
X5arg50x0000000000000000
X6arg60x0000000000000000
X7arg70x0000000000000000
X8ind0x0000000000000000
X90x0000000000000000
X100x0000000000000000
X110x0000000000000000
X120x0000000000000000
X130x0000000000000000
X140x0000000000000000
X150x0000000000000000
X16ip00x0000000000000000
X17ip10x0000000000000000
X18pr0x0000000000000000
X190x0000000000000000
X200x0000000000000000
X210x0000000000000000
X220x0000000000000000
X230x0000000000000000
X240x0000000000000000
X250x0000000000000000
X260x0000000000000000
X270x0000000000000000
X280x0000000000000000
X29fp0x0000000000000000
X30lr0x0000000000000000
SP0x0000000080000000
PC0x0000000000400000
console

Output prints here as your program runs.

Press step or run under the editor, or feed stdin from the box below.

not assembled

Open in playground