https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81611
--- Comment #14 from Jeffrey A. Law <law at redhat dot com> --- MEM_REF (as opposed to TARGET_MEM_REF) should be able to handle any simple SSA_NAME + CONSTANT_OFFSET which are all we're really concerned with here. THe target's addressing modes don't really enter the picture (that's what TARGET_MEM_REF is for). I'd look for an issue in the types preventing forwprop from doing its job here.
