**

VALUE
rb_big_pow(VALUE x, VALUE y)
{
    double d;
    SIGNED_VALUE yy;

  again:
    if (y == INT2FIX(0)) return INT2FIX(1);
    if (RB_FLOAT_TYPE_P(y)) {
        d = RFLOAT_VALUE(y);
        if ((!BIGNUM_SIGN(x) && !BIGZEROP(x)) && d != round(d))
            return rb_funcall(rb_complex_raw1(x), rb_intern("**"), 1, y);
    }
    else if (RB_BIGNUM_TYPE_P(y)) {
        y = bignorm(y);
        if (FIXNUM_P(y))
            goto again;
        rb_warn("in a**b, b may be too big");
        d = rb_big2dbl(y);
    }
    else if (FIXNUM_P(y)) {
        yy = FIX2LONG(y);

        if (yy < 0)
            return rb_funcall(rb_rational_raw1(x), rb_intern("**"), 1, y);
        else {
            VALUE z = 0;
            SIGNED_VALUE mask;
            const size_t xbits = rb_absint_numwords(x, 1, NULL);
            const size_t BIGLEN_LIMIT = 32*1024*1024;

            if (xbits == (size_t)-1 ||
                (xbits > BIGLEN_LIMIT) ||
                (xbits * yy > BIGLEN_LIMIT)) {
                rb_warn("in a**b, b may be too big");
                d = (double)yy;
            }
            else {
                for (mask = FIXNUM_MAX + 1; mask; mask >>= 1) {
                    if (z) z = bigsq(z);
                    if (yy & mask) {
                        z = z ? bigtrunc(bigmul0(z, x)) : x;
                    }
                }
                return bignorm(z);
            }
        }
    }
    else {
        return rb_num_coerce_bin(x, y, rb_intern("**"));
    }
    return DBL2NUM(pow(rb_big2dbl(x), d));
}