Messages in this thread | | | Date | Fri, 09 Aug 2019 22:03:01 +0200 | From | Christophe Leroy <> | Subject | Re: [PATCH] powerpc: fix inline asm constraints for dcbz |
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Arnd Bergmann <arnd@arndb.de> a écrit :
> On Fri, Aug 9, 2019 at 8:21 PM 'Nick Desaulniers' via Clang Built > Linux <clang-built-linux@googlegroups.com> wrote: > >> static inline void dcbz(void *addr) >> { >> - __asm__ __volatile__ ("dcbz %y0" : : "Z"(*(u8 *)addr) : "memory"); >> + __asm__ __volatile__ ("dcbz %y0" : "=Z"(*(u8 *)addr) :: "memory"); >> } >> >> static inline void dcbi(void *addr) >> { >> - __asm__ __volatile__ ("dcbi %y0" : : "Z"(*(u8 *)addr) : "memory"); >> + __asm__ __volatile__ ("dcbi %y0" : "=Z"(*(u8 *)addr) :: "memory"); >> } > > I think the result of the discussion was that an output argument only kind-of > makes sense for dcbz, but for the others it's really an input, and clang is > wrong in the way it handles the "Z" constraint by making a copy, which it > doesn't do for "m". > > I'm not sure whether it's correct to use "m" instead of "Z" here, which > would be a better workaround if that works. More importantly though, > clang really needs to be fixed to handle "Z" correctly.
As the benefit is null, I think the best is probably to reverse my original commit until at least CLang is fixed, as initialy suggested by mpe
Christophe
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