ADR 0070: GM/Local CUBE Layout Transport

• Issue: #103
• Umbrella: #72
• Baseline: 15dcfc52b2710c28cf7a50da23057b0fcb9fd7c3
• Requirement: PTO-CUBE-CELL-TRANSPORT-001
• Depends on: accepted PTO-CUBE-CELL-STATE-001

Decision

B.DATR.Layout assigns six explicit GM/Local CUBE transformations:

Code	Spelling	Legal operation	Direction
21	ND2M32	TLOAD	GM ordinary to Local CUBE_M32
22	ND2M16	TLOAD	GM ordinary to Local CUBE_M16
23	ND2N8	TLOAD	GM ordinary to Local CUBE_N8
24	M322ND	TSTORE	Local CUBE_M32 to GM ordinary
25	M162ND	TSTORE	Local CUBE_M16 to GM ordinary
26	N82ND	TSTORE	Local CUBE_N8 to GM ordinary

Codes 21 through 23 are illegal for TSTORE. Codes 24 through 26 are illegal for TLOAD. All six are illegal for a Shared Tile binding. A recognized but direction-incompatible conversion raises Tile legality before allocation, source consumption, or memory effects.

Raw representation

Conversion preserves the concrete Tile dtype and every valid element's raw representation. It is a layout transform, not TCVT: it performs no numerical rounding, saturation, canonicalization, widening, narrowing, or type change.

Every dtype with an assigned CUBE b32, b16, b8, or b4 mapping may use the matching conversion when the operation's own dtype profile permits it. HiF4X2 and every b64 dtype reject because they have no legal CUBE CELL state.

TLOAD behavior

GM-to-Local TLOAD derives the persistent destination layout from the selected ND2* code and consumes logical dimensions from the operation's existing dimension schema. Before the first effect it validates:

• exact conversion direction and Local destination form;
• dtype and CELL mapping;
• positive valid dimensions;
• derived CELL geometry and per-PE TSize capacity;
• base, byte row stride, and the complete valid GM footprint; and
• destination availability.

TLOAD reads GM only for valid logical elements. Physical CELL positions outside the valid region receive the resolved PadValue and do not cause GM reads. After all reads succeed, it atomically publishes the Local CUBE descriptor, payload, and definedness state.

TSTORE behavior

Local-to-GM TSTORE requires the source descriptor to match the selected M*2ND or N82ND code. It preflights the complete valid destination footprint before the first write. It writes only valid logical elements in ordinary GM order; physical CELL padding positions never write memory.

TSTORE does not change the persistent Local descriptor, payload, or lifetime.

Fault and restart ordering

Wrong direction, Shared participation, unsupported dtype, descriptor mismatch, invalid dimensions, insufficient capacity, undefined valid source data, and invalid memory footprints reject before effects. A recoverable memory fault retries the first uncommitted access and does not duplicate allocation, source effects, or preceding memory writes.

Defaults and protected behavior

• Layout code zero retains the existing ordinary non-converting transfer.
• Omission never infers a CUBE conversion.
• GM/Shared remains ordinary base-plus-byte-row-stride transport.
• Existing byte-row-stride and packed-memory rules remain unchanged.
• PE mask zero remains a strict no-op before conversion and memory legality.

Explicit exclusions

This decision defines no GM/Shared conversion, Local/Shared conversion, in-place payload reinterpretation, CUBE-to-CUBE conversion, Matrix execution, or new dimension command.

Acceptance criteria

The accepted ASL, generated documentation, and independent decoded tests prove:

1. all six exact encodings and direction restrictions;
2. b32/b16/b8/b4 raw-bit round trips, including M16-b4 interleave;
3. multi-CELL K/N ordering and partial-tail PadValue behavior;
4. no GM access outside the valid region;
5. HiF4X2, b64, Shared, and wrong-direction rejection before effects;
6. first, middle, and last memory-fault rollback and exact restart; and
7. unchanged ordinary TLOAD/TSTORE behavior.

Binary envelope consequence

The common encoded-form envelope remains exactly 540 forms. The only changed fingerprinted input is the assigned-value constraint of the existing B.DATR Layout field, which adds codes 21 through 26. No form identity, instruction length, mask, match, field position, BSTART.TLOAD selector, or BSTART.TSTORE selector changes.

The reviewed encoded-form fingerprint is rebound from 129cb7812264b7e4c5edd088b5aedcc528966eb69c06879dc1919c85106e21b4 to b19b0cc84c9e033f0d74bddcaea82aa935f4000682ed184340481ebb34f46004. The release encoding projection is correspondingly rebound from 9738fbfb67c90b90dacdae926c6ee206a2d517691ae27e5e5fc019702cc0e447 to 882cdc54d00ff7670159f86942f4a4f48e637be4a04975813fda15dacc46f522.