But when you have an explicit nullptr test you will have to mask it before testing the zero-flag in the control register.
And just to make it explicit: you will have to add the masking logic to all comparisons of nullable pointers too if you want to allow comparison of null to be valid.
aptr==bptr => ((aptr&MASK==0)&&(bptr&MASK==0))||aptr==bptr or something like that.
