fp_to_bp_offset

    const fp_to_bp_offset = off: {
        // On 32-bit PA-RISC, the base pointer is the final word of the frame marker.
        if (native_arch == .hppa) break :off -1 * @sizeOf(usize);
        // On 64-bit PA-RISC, the frame marker was shrunk significantly; now there's just the return
        // address followed by the base pointer.
        if (native_arch == .hppa64) break :off -1 * @sizeOf(usize);
        // On LoongArch and RISC-V, the frame pointer points to the top of the saved register area,
        // in which the base pointer is the first word.
        if (native_arch.isLoongArch() or native_arch.isRISCV()) break :off -2 * @sizeOf(usize);
        // On OpenRISC, the frame pointer is stored below the return address.
        if (native_arch == .or1k) break :off -2 * @sizeOf(usize);
        // On SPARC, the frame pointer points to the save area which holds 16 slots for the local
        // and incoming registers. The base pointer (i6) is stored in its customary save slot.
        if (native_arch.isSPARC()) break :off 14 * @sizeOf(usize);
        // Everywhere else, the frame pointer points directly to the location of the base pointer.
        break :off 0;
    }