Comment by firebacon

You don't need any specific instructions. The hex encoded double contains the final binary representation of the floating point number. So no conversion is required to load it, except maybe for swapping around bytes on some architectures. Conceptually:

    double v;
    memcpy(&v, "\x00\x00\x00\x00\x00\xe4\x94\x40", sizeof(v)); // LE