Machine Program and Native Target Boundary

This document owns the handoff from concrete MIR to native executable bytes. Internal mechanisms belong in the nocter-machine, nocter-arm64, and nocter-macho READMEs.

Pipeline

MirProgram
  -> MachineLayoutStore
  -> MachineProgram
  -> Arm64Program
  -> MachOImage

MachineLayoutStore assigns immutable stored layouts to the concrete types already closed by Executable. MachineProgram classifies arguments and results, expands target-independent storage and destruction operations, closes primitive dependencies, and owns deterministic machine linkage.

Arm64Program assigns physical registers and frames, selects and encodes instructions, and resolves branch/data fixups. MachOImage assigns file-format structures and emits final bytes. Artifact publication remains outside all three products.

ABI Ownership

The public ABI contract comes from spec/platform/abi-and-layout.md. Machine is its sole implementation owner for stored layout and argument/result transport. ARM64 consumes already classified machine values; it cannot independently decide aggregate layout or source-level calling convention. Mach-O consumes encoded sections and cannot alter code selection or linkage identity.

Semantic Closure

Machine input contains closed runtime representations and primitive roles. No native stage can inspect a semantic declaration, generic requirement, interface implementation, source path, or rendered type. Structural copy and destruction use explicit concrete schemas rather than recovering field or variant structure from names.

Required Invariants

• Every concrete type has one stored-layout result.
• Every call site and callee use the same machine transport plan.
• Machine linkage names already selected items and never performs semantic lookup.
• ARM64 register allocation cannot change ABI classification.
• Primitive expansion is selected by closed runtime role.
• Mach-O writing is deterministic and cannot introduce executable items.
• No partial image is a successful native artifact.