Hi Jeff, > This is exactly what I was trying to get to. If the addressing mode > isn't supported, then we shouldn't be picking it as a candidate. If it > is, then we've probably got a problem somewhere else in this code and > this patch is likely papering over it.
I'll take a deeper look into the candidate selection algorithm then. Will get back to you. Regards, Dimitrije ________________________________________ From: Jeff Law <jeffreya...@gmail.com> Sent: Tuesday, November 1, 2022 7:46 PM To: Richard Biener; Dimitrije Milosevic Cc: gcc-patches@gcc.gnu.org; Djordje Todorovic Subject: Re: [PATCH 1/2] ivopts: Revert computation of address cost complexity. On 10/28/22 01:00, Richard Biener wrote: > On Fri, Oct 28, 2022 at 8:43 AM Dimitrije Milosevic > <dimitrije.milose...@syrmia.com> wrote: >> 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. > But something is wrong then - it shouldn't ever pick a candidate with > an addressing > mode that isn't supported? So you say that the cost of expressing > 'BASE + INDEX << SCALE + OFFSET' as 'BASE + OFFSET' is not computed > accurately? This is exactly what I was trying to get to. If the addressing mode isn't supported, then we shouldn't be picking it as a candidate. If it is, then we've probably got a problem somewhere else in this code and this patch is likely papering over it. Jeff
