Shuffling a hole shut
The generic stack (a sibling of the queue — its struct is in the context) sometimes needs to remove an element from the middle: cancel one queued effect, keep the rest in order. The shipped answer is honest brute force — bcopy every element above the hole down one slot.
This is your first target with the full non-leaf loop apparatus: five saved registers, a call per iteration, and pointer arithmetic done once up front. Here's the skeleton on its own, in flushRange — walk a byte range, calling out once per chunk:
0: addiu sp, sp, -40
4: sw s2, 32(sp)
8: sw s1, 28(sp)
c: sw s0, 24(sp)
10: or s0, a0, zero # cursor → s0: it must survive the calls
14: or s1, a2, zero # chunk → s1
18: or s2, a1, zero # end → s2
1c: sw ra, 36(sp)
20: sltu at, s0, s2 # cursor < end? pointers compare UNSIGNED
24: beqz at, 0x44 # empty range → skip the loop entirely
28: or a0, s0, zero # (slot) first call's argument
2c: jal flush
30: or a1, s1, zero # (slot) second argument rides the jal
34: addu s0, s0, s1 # cursor += chunk
38: sltu at, s0, s2
3c: bnezl at, 0x2c # more → go again
40: or a0, s0, zero # (slot) refresh the argument
44: lw ra, 36(sp)
48: lw s0, 24(sp)
4c: lw s1, 28(sp)
50: lw s2, 32(sp)
54: jr ra
58: addiu sp, sp, 40
Every piece is a tier-3 lesson doing its job: loop values in s-registers because t-registers die at each jal, the guard test cloned above the loop, call arguments staged in delay slots, sltu because pointer comparisons are unsigned.
The target stacks three wrinkles on top. The loop bounds are computed: an end pointer from count, a source pointer from idx + 1 — watch for an addiu of 1 before one of the two multus — and a destination trailing the source by one element (subu right at the branch). The element size rides in an s-register but is re-read from the struct inside the loop — after a call, the compiler re-proves what memory holds, and your C must leave it the freedom to do so by using the field, not a stashed local, for the advances. And when the loop settles, count drops by one.
Label the three pointers on paper first. The C is shorter than the listing wants you to believe.
Your task
Write func_800c0620 to reproduce the target assembly.