--- func_80185840 (line 4227) ---
/* The `register ... __asm__("$4")` pin on the FIRST call argument is load-bearing.
 * The target sets $a0 = 0x6FE in the ENTRY block (dbr steals it into the `bnez`
 * delay slot -- sched.md D1 backward fill), but a plain `s32 id = 0x6FE;` local is
 * rematerialised at the use site (single-set constant pseudo -> REG_EQUIV), so the
 * `li` sinks past the label into the join block and dbr fills the slot with the
 * if-body's `lui` instead (SHIFT-DRIFT/+1). Pinning the local to $a0 makes the `li`
 * a hard-reg set that stays where it is written, and the call's arg move degenerates
 * to a deleted `(set (reg 4) (reg 4))`. */
