On Tue, Oct 20, 2020 at 09:44:33AM +0200, Christophe Leroy wrote: > Le 19/10/2020 à 22:24, Segher Boessenkool a écrit : > >>but the associated "<>" constraint is missing. > > > >But that is just fine. Pointless, sure, but not a bug. > > Most of those are from prehistoric code. So at some point in time it was > effective. Then one day GCC changed it's way and they became pointless. So, > not a software bug, but still a regression at some point. > > >>Use UPD_CONSTR macro everywhere %Un modifier is used. > > > >Eww. My poor stomach. > > There are not that many :)
Heh, your pain threshold is much higher than mine I guess :-) > >Have you verified that update form is *correct* in all these, and that > >we even *want* this there? > > I can't see anything that would militate against it, do you ? > > I guess if the elders have put %Us there, it was wanted. On old CPUs, update form load/stores actually executed faster than a "normal" memory access and an addi (or plain add). But on more recent stuff it mostly saves code size. Which is nice of course, and can speed up your code a bit, in theory at least. It is quite hard to trigger the compiler to generate update form insns in asm, sigh. So testing will probably not show anything either way. Oh well :-) Segher
