Found by Linux Verification Center (linuxtesting.org) with SVACE.
Reported-by: Artem Semenov <savoptik@altlinux.org>.

The defect has been detected and confirmed in the function ArchDesc::declareClasses() located in the file src/hotspot/share/adlc/output_h.cpp with static code analysis. This defect can potentially lead to a null pointer dereference.

The pointer instr->_matrule is dereferenced in line 1952 without checking for nullptr, although earlier in line 1858 the same pointer is checked for nullptr, which indicates that it can be null.