// ASM stream — the round trip: sx → asm → sx. A global-asm routine (`_caller`)
// CALLS BACK into an sx function (`cb`) by its symbol, then returns. For the asm
// `bl _cb` to resolve, the sx callback needs EXTERNAL LINKAGE and a stable C
// symbol — that is exactly what `export` provides (it also implies the C ABI, so
// no hidden context parameter). `callconv(.c)` alone is NOT enough: it sets the
// ABI but leaves the function `internal`, so it is dead-code-eliminated (nothing
// in the IR references it — the `bl` is opaque to the optimizer) and `_cb` is
// undefined at link. macOS gives `export "cb"` the symbol `_cb` (leading
// underscore), which the template references. aarch64-macos-pinned; runs under
// the JIT here (sx run), ir-only elsewhere.

// The sx callback — `export` gives it external linkage + the `_cb` symbol + C ABI.
cb :: (n: i64) -> i64 export "cb" {
    return n + 1;
}

// A global-asm trampoline that calls back into `cb`. It saves/restores the link
// register (x30) around the `bl` — it was itself reached via `bl`, so the return
// address must survive the nested call.
asm {
    #string ASM
.global _caller
_caller:
    stp x29, x30, [sp, #-16]!
    bl _cb                      // x0 = cb(x0)  — back into sx
    ldp x29, x30, [sp], #16
    ret
ASM,
};

caller :: (n: i64) -> i64 extern;

main :: () -> i64 {
    return caller(41);          // sx main → asm caller → bl _cb → sx cb → 42
}