New assertion from JDK-8293844 was hit on PPC64 while running jdk/jfr/event/gc/configuration/TestGCHeapConfigurationEventWithHeapBasedOops.java:
# Internal Error (/src/hotspot/share/opto/output.cpp:941)
# assert(t->base() == Type::Int || t->base() == Type::Half || t->base() == Type::FloatCon || t->base() == Type::FloatBot) failed: Unexpected type: inst:

Debugging shows that the C2's decodeN_mergeDisjointNode misses a set_oop call which causes the issue.
The usage in decodeN_Disjoint_isel_Ex is not problematic because it is only inserted in the middle of a postalloc_expand sequence. But, the usage in decodeN_Disjoint_notNull_Ex should get fixed because it produces an oop at the end of the postalloc_expand sequence.