JIT and AOT execution model

Decision summary

• AOT is the primary production execution path.
• JIT is a thin development-time runner for fast feedback.
• JIT and AOT both consume the same frontend and CLIF lowering.
• Runtime ABI is the single execution boundary for both backends.

Ownership split

• beskid_analysis: parse, resolve, type analysis, diagnostics.
• beskid_codegen: lowering from semantic IR to backend-consumable artifact.
• beskid_engine: thin JIT execution backend for development-time execution.
• beskid_aot: object emission and final artifact linkage for production outputs.
• beskid_runtime: runtime ABI implementation and platform policy ownership.

JIT flow

1. Build host ISA (cranelift_native::builder).
2. Create JITModule via JITBuilder.
3. Declare builtin/runtime imports from the shared runtime ABI manifest.
4. Define functions from CLIF contexts.
5. finalize_definitions() and execute.

JIT scope is intentionally narrow:

• compile + execute host-platform code
• import runtime ABI symbols
• no platform syscall policy and no backend-specific execution behavior

AOT flow

1. Build target ISA.
2. Create ObjectModule via ObjectBuilder.
3. Declare/define functions using the same runtime ABI import surface as JIT.
4. finish() emits an object file for external linking.

AOT owns production deployment concerns (linking/runtime packaging).

Allowed backend differences

• In-memory execution finalization (JIT) vs object and linker pipeline (AOT).
• Host-only execution for JIT vs explicit target triples for AOT.
• Final output form (in-memory code vs object/static/shared/exe artifacts).

Forbidden backend differences

• Divergent language semantics for identical lowered input.
• Divergent runtime ABI symbol surfaces.
• Backend-owned syscall/platform policy bypassing runtime ownership.

Export rules (decision)

• Only pub functions are exported in the final artifact.
• All internal symbols are mangled and not exported.
• Runtime ABI exports remain stable and are versioned separately.

Name mangling

• Uses pn:: prefix and always includes the signature.
• See ../ir-and-lowering/name-mangling.md for full rules.