Four more ways to test against zero
Equality isn't the only cheap comparison against zero. MIPS gives ordering tests their own branch quartet:
blez — branch if <= 0bgtz — branch if > 0bltz — branch if < 0bgez — branch if >= 0
No compare instruction, no at, no constant — the sign test is fused straight into the branch. Here's if (x > 0) return a; return b;:
0: blez a0, 0x10 # x <= 0? take b instead
4: or v0, a2, zero # (delay slot) b, preloaded
8: jr ra
c: or v0, a1, zero # x > 0: return a
10: jr ra
14: nop
The C asks > 0; the branch is blez — its exact opposite, because the branch's job is still to skip the "then". The four mnemonics pair off into inverses: blez ↔ bgtz, bltz ↔ bgez. When you decode, find the mnemonic's partner and that's what the C tests.
Worth noticing: all four are signed tests. "Is it negative" only makes sense for a signed value, and these branches read bit 31 as a sign — which is a quiet type hint about whatever register they examine.
The target picks between its second and third arguments based on a sign test of the first. Invert the mnemonic, pair the exits with their slots, and write the if.
Your task
Write func_8006ca40 to reproduce the target assembly.