On 05.06.2025 19:34, Teddy Astie wrote: > Le 05/06/2025 à 12:28, Jan Beulich a écrit : >> Stop the compiler from inlining non-trivial memset() and memcpy() (for >> memset() see e.g. map_vcpu_info() or kimage_load_segments() for >> examples). This way we even keep the compiler from using REP STOSQ / >> REP MOVSQ when we'd prefer REP STOSB / REP MOVSB (when ERMS is >> available). >> > > If the size is known and constant, and the compiler is able to generate > a trivial rep movs/stos (usually with a mov $x, %ecx before). I don't > see a reason to prevent it or forcing it to make a function call, as I > suppose it is very likely that the plain inline rep movs/stos will > perform better than a function call (even if it is not the prefered rep > movsb/stosb), eventually also being smaller. > > I wonder if it is possible to only generate inline rep movs/stos for > "trivial cases" (i.e preceded with a plain mov $x, %ecx), and rely on > either inline movs or function call in other cases (non-trivial ones).
Note how the description starts with "Stop the compiler from inlining non-trivial ...", which indeed remain unaffected according to my observations (back at the time). Jan
