RFR[S] : JDK-8244867 : 2 vector api tests crash with assert(is_reference_type(basic_type())) failed: wrong type

[Bhateja, Jatin]

Hi All,

Following patch fixes the failing jtreg regressions

JBS : https://bugs.openjdk.java.net/browse/JDK-8244867
Webrev: http://cr.openjdk.java.net/~jbhateja/vectorIntrinsics/BUGS/JDK-8244867/webrev.02/

As per JVM specification section 5.5[1] a meager reference of class passed as parameter (ldc #class.ref)
to a method invocation does not trigger class initialization.

In this case since JVM flags -Xcomp and -XX:-TieredCompilation are used compilation is triggered at first invocation of the method.
For gather operation a vector comparison is performed to check if indices are in the valid range

    @Override
    @ForceInline
    public final IntMaxMask compare(Comparison op, Vector<Integer> v) {
        return super.compareTemplate(IntMaxMask.class, op, v);  // specialize
    }

In above vector compare API a mask class is passed as a parameter, eager compilation(-Xcomp) gets triggered and compiler receives an
uninitialized class as an argument. This causes an assertion failure while validating static fields (ETYPE and LENGTH)
Of this un-initialized mask class.

Values of these static fields are used during vector object re-construction in case of deoptimization. Adding safety checks
to prevent intrincifiation if class arguments of non-primitive types are uninitialized.

Thanks,
Jatin

[1] : https://docs.oracle.com/javase/specs/jvms/se14/html/jvms-5.html#jvms-5.5