On Tue, Jun 13, 2023 at 2:16 PM Segher Boessenkool <seg...@kernel.crashing.org> wrote: > > Hi! > > On Tue, Jun 13, 2023 at 10:15:49AM +0800, Jiufu Guo wrote: > > David Edelsohn <dje....@gmail.com> writes: > > > > > > This definitely seems to be a better solution. > > > > > > The TARGET_CONST_ANCHOR change should not be part of this patch. Also > > > there is no ChangeLog for the patch. > > > > Thanks a lot for your quick review!! And sorry for the sending this patch > > in a hurry. I would update the patch accordingly. > > > > This generally looks correct and consistent with other ports. I want > > > to give Segher a chance to double check it, if he wishes. > > The documentation is very clear that the only thing for which you can > have BLKmode is "mem". Not unspec, only "mem". > > Let's not do this. The existing code has clear and obvious semantics, > which is documented as well -- there is no reason to make it worse in > every respect.
Segher, Unfortunately, GCC now is inconsistent and this response is incorrect. The documentation is out of date or was ignored and the "facts on the ground" contradict your review. Yes, (const_int 0) is supposed to be a general no-op and BLKmode only is supposed to be used for MEM, but other major targets (arm, aarch64, riscv, s390) all use unspec:BLK and specifically UNSPEC_TIE. rs6000 is the only port that does not follow this convention. The middle-end has adapted to the behavior of all of the other targets, whether that conformed to the documentation or not. The rs6000 port needs to be fixed and Jiufu's approach is the correct one, consistent with all other targets for stack tie. If the documentation differs, the documentation needs to be updated, not a different approach for the rs6000 port. Jiufu's patch is correct. Thanks, David
