# sx Inline Assembly — Checkpoint (ASM stream)

Companion to `current/PLAN-ASM.md`; design in
[docs/inline-asm-design.md](../docs/inline-asm-design.md). Update after every
commit, one step at a time per the cadence rule (no commit may both add a test
and make it pass).

## Last completed step
**0.0** — corpus runner target-gating + `<name>.build` JSON config. Added
`BuildConfig` (`std.json.parseFromSliceLeaky` → `struct { aot, target }`,
unknown-key ⇒ `error.UnknownField`) replacing the standalone `.aot` marker;
migrated the 2 existing `.aot` markers (1226/1227) to `{ "aot": true }`; threaded
`--target` into the `run`/`build`/`ir` spawns via `withTarget`; added
`hostMatchesTarget` (shorthand-expand + arch/os token match, `arm64`→`aarch64`)
gating the execute path. Cross-target mismatch fails **loudly** (placeholder until
0.1's ir-only branch) — verified the bail fires (`target=linux,
host=aarch64-macos`). Locked with `examples/1638-platform-target-host.sx`
(`.build` `{ "target": "macos" }`, runs natively + asserts stdout) + unit tests
for the JSON parse and `hostMatchesTarget`. `zig build test` green (646 corpus, 0
failed; 444 unit, 0 failed). Files: `src/corpus_run.test.zig`,
`examples/1638-*`, `examples/expected/{1226,1227,1638}-*`.

## Current state
Phase 0 step 0.0 landed (test-infra only — no compiler code touched). The corpus
runner now reads `expected/<name>.build` and threads/gates `--target`; an
arch-pinned example whose target matches the host **executes**, a mismatch
currently **bails loudly** ("cross-target ir-only mode not yet implemented"). Phase
A–E feasibility already confirmed against the live tree (`LLVMGetInlineAsm` /
`LLVMBuildCall2` / `LLVMAppendModuleInlineAsm` in LLVM@19 `Core.h`; ERR-stream
`extractvalue`→tuple machinery in `emit_llvm.zig:726-927`; lib-less `extern`, 60
sites; `--target` a global CLI flag).

## Next step
**0.1** — implement the **mismatch ⇒ ir-only** branch in `sweepRoot` (replace the
loud placeholder bail): when `cfg.target` doesn't match the host, skip
run/build/exec and assert only `.exit`+`.ir`+`.stderr` from `sx ir --target`;
require an `.ir` snapshot (loud failure if absent). Lock with
`examples/16xx-platform-target-cross.sx` (asm-free `() -> i64 { return 0; }`),
`.build` `{ "target": "x86_64-linux" }`, + a checked-in `.ir` snapshot. Then 0.2
(CLAUDE.md §Testing/§Test-layout docs for `.build`), then Phase A (`kw_asm`). See
`PLAN-ASM.md` Phase 0.

## Log
- (init) Plan + design doc written; ASM stream opened.
- (0.0) Corpus runner target-gating: `<name>.build` JSON config (replaces `.aot`
  marker), `--target` threading, `hostMatchesTarget` execute-gate, loud
  cross-target placeholder bail. Migrated 1226/1227 `.aot`→`.build`; locked with
  1638 fixture + unit tests. `zig build test` green.

## Known issues
None yet.