On Mon, Dec 12, 2022 at 11:35 AM Wilco Dijkstra via Libc-alpha <libc-al...@sourceware.org> wrote: > > Hi, > > I don't believe there is a missing optimization here: compilers expand mempcpy > by default into memcpy since that is the standard library call. That means > even > if your source code contains mempcpy, there will never be any calls to > mempcpy. > > The reason is obvious: most targets support optimized memcpy in the C library > while very few optimize mempcpy. The same is true for bzero, bcmp and bcopy. > > Targets can do it differently, IIRC x86 is the only target that emits calls > both to > memcpy and mempcpy.
yeah, x86_64 at least uses both, but I think open coded mempcpy needs to be transformed into a library call anyway. Other optimizations that are actually missing are: - the cases where of snprintf %s could become memccpy - open coded memccpy could also be turned into library calls.
