On Thu, Sep 03, 2020 at 04:46:43PM -0300, Alexandre Oliva wrote: > On Sep 3, 2020, Segher Boessenkool <seg...@kernel.crashing.org> wrote: > > The idea is that none of them will need adjustment. This hook runs > > before the "none" code will run, and it can just clear all clobbers > > then. > > Uhh... That's not how asm expansion works. We process inputs, outputs, > clobbers and labels first, *then* we pass all the cooked ops to the > target hook, so that it gets a chance to, well, adjust stuff.
And after that you do the "none" stuff, not before! > I don't think clobber "none" should disable target adjustments; IMHO, it > should be recognized by target adjustments, and cause them to not add > stuff they normally would. Yeah, big thinko on my side there. But my point remains: if we can do this in generic code (and it looks like we can), don't do it in all 50+ targets (or the tennish affected ones) :-) > > The user could want to use an empty asm to influence what code is > > generated. Yes, I know this isn't a very strong argument :-) > > Well, it is to me, it's exactly what I'm doing here, you know? :-) "I hadn't noticed yet". Hehe. > But it's not the kind of "things going wrong" that I was looking for. > > > just set a flag and not call md_asm_adjust? > > I don't like that. When we move some asm processing between > target-specific and generic, in either direction, suddenly "none" > affects whether or not the processing gets done. I don't like that. But we do not *have* "none" in trunk yet (and so, of course also not in any released GCC version, the important consideration). Or you nmean something else that I don't see? > > Maybe "nodefault" is a > > better name than "none" btw > > For that, I agree, but I don't think that's a good feature to have. I'd > rather have "none" and keep the ability to introduce target-specific > adjustments à-la "=@cc*". There's no good reason IMHO to have that hook > disabled by "none" or by "nodefault". "none" would disable all default *clobbers* only. Not outputs. Segher
