https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78041
--- Comment #6 from Richard Earnshaw <rearnsha at gcc dot gnu.org> --- (In reply to Bernd Edlinger from comment #5) > (In reply to Wilco from comment #4) > > However dealing with partial overlaps is complex so maybe the best option > > would be to add alternatives to <shift>di3_neon to either allow full overlap > > "r 0 X X X" or no overlap "&r r X X X". The shift code works with full > > overlap. > > That sounds like a good idea. > > Then this condition in <shift>di3_neon could go away too: > > && (!reg_overlap_mentioned_p (operands[0], operands[1]) > || REGNO (operands[0]) == REGNO (operands[1]))) Note that we don't want to restrict complete overlaps, only partial overlaps. Restricting complete overlaps leads to significant increase in register pressure and a lot of redundant copying.
