"rsandifo at gcc dot gnu.org via Gcc-bugs" <gcc-bugs@gcc.gnu.org> writes:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97092 > > --- Comment #6 from rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.org> > --- > (In reply to Andrea Corallo from comment #5) >> "rsandifo at gcc dot gnu.org via Gcc-bugs" <gcc-bugs@gcc.gnu.org> >> writes: >> >> > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97092 >> > >> > --- Comment #4 from rsandifo at gcc dot gnu.org <rsandifo at gcc dot >> > gnu.org> --- >> > (In reply to Andrea Corallo from comment #3) >> >> Created attachment 49710 [details] >> >> PR97092.patch >> >> >> >> What is going on is that in 'update_costs_from_allocno' we try to >> >> identify the smallest mode using narrower_subreg_mode to then update the >> >> costs. >> >> >> >> The two modes involved here are E_DImode and E_VNx2QImode, cause these >> >> are not ordered we ICE in 'paradoxical_subreg_p'. >> >> >> >> Now I don't know if the strategy we want is: >> >> >> >> - In 'update_costs_from_allocno' when modes are not ordered instead of >> >> calling 'narrower_subreg_mode' just keep the current one. >> >> >> >> - Always select the cheapest mode in terms of cost. >> >> >> >> The attached I'm testing implements the second. >> >> Hi Richard, >> >> thanks for commenting. >> >> > I think instead we should consider recomputing “mode” in each >> > iteration of the loop, rather than carry over the result of >> > previous iterations. I.e. use: >> > >> > mode = narrower_subreg_mode (ALLOCNO_MODE (cp->first), >> > ALLOCNO_MODE (cp->second)); >> >> Are we garanteed to have ALLOCNO_MODE (cp->first) and ALLOCNO_MODE >> (cp->second) always satisfying 'ordered_p'? > Yeah, I think so. If the modes aren't ordered then we shouldn't > create a copy between them. Great, I'm going to test the suggested then. Thanks Andrea
