Feature: LLVM Backend

Purpose

Code generation goes through LLVM: the front end (lexer, parser, semantic analysis) is owned by Elseon; the backend is LLVM, which already knows every target the kernel cares about and applies decades of optimization work Elseon will never need to redo — PFE applied to compilers.

Requirements

• LLVM-R001 — The compiler must lower Elseon through LLVM for code generation.
• LLVM-R002 — Deterministic memory layout is a front-end contract: semantic analysis decides representation; conformance tests check the backend against the promised layout (struct layout, padding, alignment).
• LLVM-R003 — The generated code must satisfy the Kernel Test: no runtime, no GC, no hidden allocations, no hidden control flow beyond what the source spells out.
• LLVM-R004 — The toolchain must be kernel-adjacent: buildable with a pinned LLVM version, with no runtime dependency beyond what a kernel build already accepts.
• LLVM-R005 — The LLVM version and the API choice (C API vs. C++ API; static vs. shared linking) must be pinned and recorded in the project.
• LLVM-R006 — The elseon driver and toolchain live in sources/; make build builds them from phase 3 onward (site build remains part of make site).

Behavior

• A conformance test must compile an Elseon program to an object file with the pinned LLVM and link it against a C program, verifying layout and call boundaries.
• A live-state test (per the test tiers in prompts/02-workflow.md) must compile a kernel-adjacent subsystem and report PASS/WARN/FAIL against the declared prerequisites.

Dependencies

• Feature 03-language-core.md (Language Core) — the Kernel Test guarantees the backend must honor.
• Feature 04-c-header-ingestion.md (C-Header Ingestion) — the checked call boundaries the backend must lower.