// ASM stream Phase E — multi-output asm that RUNS end-to-end on aarch64. Splits
// a value into low/high bytes via two value outputs, returned + destructured as
// a `(lo, hi)` tuple. The two outputs become an LLVM `{ i64, i64 }` struct =
// sx's tuple. aarch64-pinned via `.build`: executes on a matching host (exit
// reflects lo+hi), ir-only elsewhere.
split :: (x: u64) -> (lo: u64, hi: u64) {
    return asm {
        #string ASM
        and %[l], %[x], #0xff
        lsr %[h], %[x], #8
ASM,
        [l] "=r" -> u64,
        [h] "=r" -> u64,
        [x] "r" = x,
    };
}
main :: () -> i64 {
    lo, hi := split(0x1234);
    return xx (lo + hi);   // 0x34 + 0x12 = 52 + 18 = 70
}