On Fri, Jan 12, 2018 at 10:29:01PM +0100, Arnd Bergmann wrote: > On Fri, Jan 12, 2018 at 9:41 PM, Segher Boessenkool > <segher@xxxxxxxxxxxxxxxxxxx> wrote: > > On Fri, Jan 12, 2018 at 08:43:21PM +0100, Arnd Bergmann wrote: > >> On Fri, Jan 12, 2018 at 5:39 PM, Segher Boessenkool > > >> We could theoretically work around it by turning that into > >> "#if defined(CONFIG_CC_OPTIMIZE_FOR_SIZE) || > >> defined(CONFIG_CRYPTO_AES)", but that seems rather ugly. > >> > >> My earlier patch already tried to be more specific, turning very > >> specific optimizations off rather than moving from -O2 to -Os, > >> but that turned out to lead to significantly worse performance, > >> where -Os improved performance slightly. Is there a way > >> to ask powerpc compilers to use mostly -Os but not the > >> specific thing that makes it link to _restgpr_31_x? > > > > There is no such thing, sorry. Would be very hard to implement, and > > older compilers will never get it, so it won't help you anyway :-( > > We use -Os only for gcc-7.1 and higher, where it produces faster > code for AES and avoids running into > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83356 > > > Maybe for now just enable it in crtsavres.S always, with a comment? > > That -Os workaround is hopefully not going to live long either... > > It depends on whether or how soon someone comes up with a > better fix for PR83356. > gcc-8.0.0 is currently not affected by it, so we could limit the > workaround (and the hack in crtsavres.S) to gcc-7-only. I guess you could enable the _x routines whenever you use ubsan? Ubsan will cause much bigger code growth than the handful of insns in those routines? Segher
