> > Not sure, tree-ssa-dse.c doesn't seem to handle MEM_REF with offset? > > VN has adjust_offsets_for_equal_base_address for this purpose. I > agree that some common functionality like > > bool > get_relative_extent_of (const ao_ref *base, const ao_ref *ref, > poly_int64 *offset); > > that computes [offset, offset + ref->[max_]size] of REF adjusted as to > make ao_ref_base have the same address (or return false if not > possible). Then [ base->offset, base->offset + base->max_size ] > can be compared against that.
OK, I will look into that. > > + if (valid_ao_ref_for_dse (write) > > + && operand_equal_p (write->base, ref->base, OEP_ADDRESS_OF) > > + && known_eq (write->size, write->max_size) > > + && normalize_ref (write, ref) > > normalize_ref alters 'write', I think we should work on a local > copy here. See live_bytes_read which takes a copy of 'use_ref'. We never proces same write twice (get_ao_ref is always constructing fresh copy), so this should be safe. Or shall I turn the write parameter to "ao_ref write" instead of "ao_ref *write" just to be sure we do not break infuture? Thank you, Honza
