Review week 19: subroutines

This week was about subroutines. For review:

• jal / j ra: jal jumps and writes the next line into ra, j ra returns there. Subroutines belong after the main loop.
• Nested: if a subroutine calls jal itself, ra is overwritten. push ra at the start, pop ra before the j ra, on every path. Every level costs one stack slot.
• Calling conditionally: beqal, bneal, bltal, bgtal, bleal, bgeal and the z forms beqzal to bgezal. If nothing is called, ra stays unchanged. A default state belongs before the calls.
• NaN: only the ne forms (bneal, bnezal) call on NaN. bapal and bnaal both do not in the game.
• Tolerance and devices: bapal, bnaal, bapzal, bnazal, bdseal, bdnsal. There is no brXXal or jral.
• One subroutine for many: pass names and stack slots via registers.

You pass from 60 %, the explanations appear after handing in.