ADR 0051: Predicate state namespace boundary (superseded)

• Decision date: 2026-08-01

Current boundary

PTO exposes P0 through P7 as eight independent 32-bit predicate registers. P0 is hardwired to all ones; P1 through P7 reset to zero and are independently trap-preserved. No accepted instruction produces or consumes this register file.

Machine-parallel and machine-sequential block encodings are extension-reserved and have no PTO execution semantics. Their former execution-mask model is not architectural PTO state. Any future predicate namespace or instruction mapping requires an explicit encoding, state, reset, trap, producer, consumer, and executable-test contract.

This file records the superseded decision only. The current executable contract is defined by the ASL programming-model and scalar BRU units.