On Tue, 9 Jul 2019, Jan Hubicka wrote: > > > tree_int_cst_equal will return false if offsets are not INTEGER_CST. > > > I was not sure if I can safely use operand_equal_p. What happens for > > > fields with variable offsets when I inline two copies of same function > > > which takes size as parameter and make the size different? Will I get > > > here proper SSA name so operand_equal_p will work? > > > > No, you get a DECL, but yes, I think operand_equal_p will work. > > Consider two _same_ variable sizes, you'll not see that you > > have to return zero then? But yes, in case you have types > > globbed to the canonical type (but not FIELD_DECLs) then > > you'll get false !operand_equal_p as well. > > > > The question is really what is desired here. If you want/need precision > > for non-constant offsets then you have to look at the COMPONENT_REF > > trees because the relevant offset (SSA name) is only there > > (in TREE_OPERAND (component_ref, 2)). > > > > If you want to give up for non-constants and can do that without > > correctness issue then fine (but Ada probably would like to have > > it - so also never forget to include Ada in testing here ;)) > > I would like to have precision here. so perhaps as incremental change I > can > 1) reorganize callers to pass refs rather than just field_decls > 2) check if TREE_OPERAND (component_ref, 2) is non-NULL in both case > a) if so do operand_equal_p on them and return 0 on match > b) if there is no match see if I have same canonical types and > return 1 then > c) return -1 otherwise
makes sense > 3) continue with parsing FIELD_DECLS we work on now. > > > > Oh, OK ... a bit more explaining commentary might be nice > > (at the top of the function - basically what the input > > constraints to the FIELD_DECLs are). > > OK, will try to improve comments (though i tried to be relatively > thorough). > > Honza > > > > Btw, the offsets in FIELD_DECLs are relative to DECL_CONTEXT so > > comparing when DECL_CONTEXT are not related at all doesn't make > > any sense. Well, unless we know _those_ are at the same offset, > > so - the constraint for the FIELD_DECLs we compare is that > > the containing structure type object instances live at the same > > address? > > > > Richard. > -- Richard Biener <rguent...@suse.de> SUSE Linux GmbH, Maxfeldstrasse 5, 90409 Nuernberg, Germany; GF: Felix Imendörffer, Mary Higgins, Sri Rasiah; HRB 21284 (AG Nürnberg)
