Jlong conversions
-----------------
Casting a jlong to a jlong is unnecessary and does not work if a jlong is a
structure.

src\share\native\java\lang\double.c

/*
 * Find the double float corresponding to a given bit pattern
 */
JNIEXPORT jdouble JNICALL
Java_java_lang_Double_longBitsToDouble(JNIEnv *env, jclass unused, jlong v)
{
    union {
        jlong l;
        double d;
    } u;
    jlong_to_jdouble_bits(&v);
#if defined IBM_ALL /*ibm*/
    u.l = v;
#else /*ibm*/
    u.l = (jlong)v;
#endif /*ibm*/
    return (jdouble)u.d;
}

/*
 * Find the bit pattern corresponding to a given double float
 */
JNIEXPORT jlong JNICALL
Java_java_lang_Double_doubleToLongBits(JNIEnv *env, jclass unused, jdouble v)
{
    union {
        jlong l;
        double d;
    } u;
    if (JVM_IsNan((double)v)) {
        u.l = jint_to_jlong(0x7ff80000);
        return jlong_shl(u.l, 32);
    }
    jdouble_to_jlong_bits(&v);
    u.d = (double)v;
#if defined IBM_ALL /*ibm*/
    return u.l;
#else /*ibm*/
    return (jlong)u.l;
#endif /*ibm*/
}