Arnd Bergmann <[email protected]> a écrit :
On Fri, Aug 9, 2019 at 8:21 PM 'Nick Desaulniers' via Clang Built Linux <[email protected]> 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
