# KOS_OP_LABEL
- **Style**: COMPILE. Compile-time only.
- **Stack**: No change.
- **Invariants**: Not present in final bytecode after normal finalize; or executed as no-op if retained.
- **Behavior**: Jump target placeholder. Finalize resolves branch targets to the LABEL's pc, then **strips** the LABEL instruction (branch args are adjusted to point at the next instruction). If a LABEL is retained, it advances PC only (safety net).
- **Compiler form:** Pre-compile arg = label name, a str or int. Branches refer to this name; finalize resolves names to pcs and strips LABEL. Post-compile: **normally omitted**; if retained, arg is 0 or unused.

**Pre-compile example:** List of (opcode, arg) pairs. The label name `"done"` is used by JUMP; finalize resolves it and then strips the LABEL.

```
["JUMP", "done"],
["CONST", 99],
["LABEL", "done"],
["RETURN", 1],
```

**Post-compile (normal):** LABEL is stripped. JUMP's target was the LABEL at index 2; after stripping, that target becomes index 1 (the next instruction). Constant 99 is in the pool at index 0.

| index | opcode | arg | arg view | comment |
|------:|--------|-----|----------|---------|
| 0     | JUMP   | 1   | 1 (-> 1) | branch to "done" (was LABEL at 2; after strip, target is 1) |
| 1     | CONST  | 0   | 0 (99)   | dead code; pool 0 = 99 |
| 2     | RETURN | 1   | 1        | (was index 3 before strip) |

**Post-compile (if LABEL retained):** Safety-net case only. If the LABEL were not stripped, it would appear as below and execute as a no-op.

| index | opcode | arg | arg view | comment |
|------:|--------|-----|----------|---------|
| 0     | JUMP   | 2   | 2 (-> 2) | branch to label |
| 1     | CONST  | 0   | 0 (99)   | dead code |
| 2     | LABEL  | 0   | --        | target "done"; no-op if executed |
| 3     | RETURN | 1   | 1        | |