This is a bug found in the realtime 64 bit C1 testing. From 6789226:

A compiled method calls a native method that uses a compiled entry
point. The call is an IC call. First thing on method entry: do the IC
check. The code allocates a new tmp register with a push/pop sequence
for this check. When the receiver is NULL the IC check acts as an
implicit null check (triggers a SEGV that the runtime will catch and
convert to a null pointer exception). But the tmp register allocation
changes the stack layout and that's not expected by the runtime when
it throws the exception.

The fix is to use rscratch1 as a tmp instead.

Tested with regression test.