# PR-1.6 — Canonical Function Boundaries & `FRAME_SYNC` Placement (Bytecode Layout)

### Briefing

GC and coroutine scheduling rely on deterministic safepoints. The bytecode layout must define canonical function boundaries and `FRAME_SYNC` semantics at the bytecode layer.

### Target

* Enforce canonical function ranges and end labels.
* Ensure `FRAME_SYNC` placement rules are representable and checkable.

### Work items

* Review current layout utilities and make them canonical for:

    * Computing function `code_len`.
    * Determining valid jump targets (instruction boundaries).
    * Determining function end boundary.
* Document `FRAME_SYNC` at the bytecode level:

    * What it signals.
    * Where it is required (as per updated specs).
* Update disasm to clearly display `FRAME_SYNC`.

### Acceptance checklist

* [ ] Function boundaries are computed via a single canonical routine.
* [ ] `FRAME_SYNC` is clearly represented and documented.
* [ ] Existing verifier/layout tests (if any) are updated.
* [ ] `cargo test` passes.

### Tests

* Add or update unit tests for layout boundary correctness (e.g., end-exclusive semantics).

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# PR-1.7 — Bytecode Roundtrip Tests (Encode/Decode/Disasm Sanity)

### Briefing

Before touching VM behavior, we want confidence that the bytecode toolchain is coherent after the ISA reset.

### Target

* Add roundtrip tests that validate:

    * Encode → decode preserves structure.
    * Disasm prints stable, readable output.

### Work items

* Add a small set of “known-good” bytecode samples built using the new minimal ISA.
* Implement tests:

    * Encode then decode equals original structure.
    * Disasm output contains expected instruction names and operands.
* Keep samples intentionally tiny and deterministic.

### Acceptance checklist

* [ ] Roundtrip tests exist and pass.
* [ ] Samples do not depend on legacy semantics.
* [ ] `cargo test` passes.

### Tests

* New unit tests for encode/decode/disasm roundtrip.