C2's Local Code Motion (LCM) can hoist DecodeN nodes into a different block. Depending on CompressedOops mode and platform, they can have MachTemp input nodes representing temp registers as needed by the platform code and /or other input nodes.

PPC64 and s390 have DecodeN implementations which use a MachTemp input. When LCM hoists the DecodeN, they reside in the old block, but should get hoisted together with the DecodeN node.

Load Base is a further possible input node (e.g. on s390).

This can be observed by the new assertion introduced by JDK-8263227 when running e.g. compiler/runtime/Test6826736.java.
Crashes are not observed in product build. However, the register allocation may produce sub-optimal results.