https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122635
--- Comment #9 from Greg McGary <gkm at rivosinc dot com> ---
gimple_fold_partial_load_store_mem_ref () handles MASK_LEN_{LOAD,STORE}. When
it folds, it returns a new RHS tree, or NULL_TREE if there is no change.
it currently only handles the case where mask is all 1s, when it returns a
simple MEM_REF.
it needs to detect length zero, and return something that will tell its callers
elide the entire statement. I have tried a couple things, but haven't gotten it
right yet, as evidenced by assertions and/or SEGVs.
