https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105533
--- Comment #10 from rguenther at suse dot de <rguenther at suse dot de> --- On Wed, 6 Mar 2024, jakub at gcc dot gnu.org wrote: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105533 > > Jakub Jelinek <jakub at gcc dot gnu.org> changed: > > What |Removed |Added > ---------------------------------------------------------------------------- > CC| |rguenth at gcc dot gnu.org > > --- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> --- > The second UB is on > #2 ao_ref_init_from_vn_reference (ref=<optimized out>, set=1, base_set=1, > type=<optimized out>, ops=...) at ../../gcc/tree-ssa-sccvn.cc:1224 > 1224 offset += op->off << LOG2_BITS_PER_UNIT; > where op->off is negative. > Isn't this just an unnecessary optimization? I mean can't we just do > offset += op->off * BITS_PER_UNIT; > BITS_PER_UNIT is a constant 8 on all targets we support... It's a habit from dealing with offset_int (but this is poly_int64) where the multiply is possibly a lot more costly than a shift. So yeah, a multiply is fine I guess.
