Hi Jeff, > THe part I don't understand is, if you only have BASE+OFF, why does > preventing the calculation of more complex addressing modes matter? ie, > what's the point of computing the cost of something like base + off + > scaled index when the target can't utilize it?
Well, the complexities of all addressing modes other than BASE + OFFSET are equal to 0. For targets like Mips, which only has BASE + OFFSET, it would still be more complex to use a candidate with BASE + INDEX << SCALE + OFFSET than a candidate with BASE + INDEX, for example, as it has to compensate the lack of other addressing modes somehow. If complexities for both of those are equal to 0, in cases where complexities decide which candidate is to be chosen, a more complex candidate may be picked. Regards, Dimitrije From: Jeff Law <jeffreya...@gmail.com> Sent: Friday, October 28, 2022 1:02 AM To: Dimitrije Milosevic <dimitrije.milose...@syrmia.com>; gcc-patches@gcc.gnu.org <gcc-patches@gcc.gnu.org> Cc: Djordje Todorovic <djordje.todoro...@syrmia.com> Subject: Re: [PATCH 1/2] ivopts: Revert computation of address cost complexity. On 10/21/22 07:52, Dimitrije Milosevic wrote: > From: Dimitrije Milošević <dimitrije.milose...@syrmia.com> > > This patch reverts the computation of address cost complexity > to the legacy one. After f9f69dd, complexity is calculated > using the valid_mem_ref_p target hook. Architectures like > Mips only allow BASE + OFFSET addressing modes, which in turn > prevents the calculation of complexity for other addressing > modes, resulting in non-optimal candidate selection. > > gcc/ChangeLog: > > * tree-ssa-address.cc (multiplier_allowed_in_address_p): Change > to non-static. > * tree-ssa-address.h (multiplier_allowed_in_address_p): Declare. > * tree-ssa-loop-ivopts.cc (compute_symbol_and_var_present): >Reintroduce. > (compute_min_and_max_offset): Likewise. > (get_address_cost): Revert > complexity calculation. THe part I don't understand is, if you only have BASE+OFF, why does preventing the calculation of more complex addressing modes matter? ie, what's the point of computing the cost of something like base + off + scaled index when the target can't utilize it? jeff
