RFR: 8228622: [lworld] Ineffective codegeneration for flattened arrays checks causes large performance regression on List iteration

[Roland Westrelin]

> I haven't looked at this in detail yet but I've submitted testing and I'm seeing the following
> failures with the Valhalla compiler tests:
>
> #  Internal Error (open/src/hotspot/share/opto/parse1.cpp:1738), pid=15342, tid=15354
> #  assert(!t->isa_valuetype() || n->is_ValueType()) failed: inconsistent typeflow info
>
> #  Internal Error (open/src/hotspot/share/opto/graphKit.cpp:2895), pid=15099, tid=15112
> #  assert(!gvn().type(res)->maybe_null()) failed: receiver should never be null
>
> #  Internal Error (open/src/hotspot/share/runtime/deoptimization.cpp:1140), pid=1741, tid=1742
> #  assert(value->type() == T_OBJECT) failed: object element expected
>
> Also, some tests fail due to invalid results.

Thanks. Here is an updated webrev:

http://cr.openjdk.java.net/~roland/8228622/webrev.01/

Roland.