Tying the chapter together
This last one is a mash-up. The function leans on an early-return guard to drop junk inputs, runs a little arithmetic, then uses branchless-style clamps to keep the answer in bounds. No new instruction appears. The challenge is recognising machinery you've already built, plus one MWCC habit of welding a clamp's compare onto the arithmetic that just ran.
The weld hangs on the trailing dot. When a mnemonic carries a ., say add. or subf., it updates the condition register as a side effect of its real work. So a freshly computed value that needs clamping skips its own cmpwi; the dotted op already set the flags the branch will test.
In step(pos, delta, limit), a non-positive limit gets ignored outright, pos moves up by delta, and the result ends up wedged inside [0, limit]:
cmpwi r5,0 # guard: limit <= 0 ?
blelr- # yes -> return pos untouched
add. r3,r3,r4 # pos += delta, and set cr0 from the result
bge- .check_hi # result >= 0 -> skip the floor
li r3,0 # floor: clamp up to 0
.check_hi:
cmpw r3,r5 # result vs limit
blelr- # <= limit -> done, return it
mr r3,r5 # otherwise saturate to limit
blr
The blelr- near the top is the guard, gone the moment it must be. Right after, add. does the arithmetic and, for free, arms the floor's bge-. The tail, cmpw into blelr- into mr, holds the value under the ceiling. You've coded each move already; the real exercise is noticing them strung together.
Yours guards and clamps something different, but you read it the same way. The guard and its return value come first, the working arithmetic sits in the middle, a clamp or two fences the result at the end. Spot a dotted op pressed against a branch with no compare in the gap, and the fusion is showing its face again.
Your task
Write apply_damage, taking hp, dmg, and armor (all int), to reproduce the assembly above.