the unit tests do not test if RA=0 (which triggers zero-imm). this needs to be added where appropriate
in ALUHelpers, (fu/test/common.py) immediate-zero checking is also needed
commit ee5469c03a547493eca63213248af654d5c1ef2b (HEAD -> master) Author: Luke Kenneth Casson Leighton <lkcl@lkcl.net> Date: Sat Aug 22 12:09:19 2020 +0100 r0 zero tests on addis, fails shows that addis is failing (this is good!)