// https://www.ibm.com/support/pages/sites/default/files/2021-05/SA22-7871-10.pdf
// https://www.ibm.com/docs/en/SSQ2R2_15.0.0/com.ibm.tpf.toolkit.hlasm.doc/dz9zr006.pdf
// https://github.com/lucab/s390-tools/blob/7217903ce44909a230003a3d4dd38c8ddf6bdb9d/include/boot/s390.h#L476

struct ExtendedFacilityList([u64; 4]);

impl ExtendedFacilityList {
    fn new() -> Self {
        let mut result: [u64; 4] = [0; 4];
        unsafe {
            core::arch::asm!(
                "lgr %r0, {0}",  // Load reg0 with size - 1
                // equivalently ".insn s, 0xb2b00000, 0({1})",
                "stfle 0({1})",
                in(reg) result.len() as u64 - 1,
                in(reg_addr) result.as_mut_ptr() ,
                options(nostack, preserves_flags )
            );
        }
        Self(result)
    }

    const fn get(&self, n: usize) -> bool {
        // of course they number bits from the left...
        self.0[n / 64] & (1 << (63 - (n % 64))) != 0
    }
}