In newer versions of glibc, memcpy() does take advantage of SIMD instructions if they are avaialble. It works something like this: The memcpy() function is mar

In newer versions of glibc, memcpy() does take advantage of SIMD instructions if they are avaialble. It works something like this: The memcpy() function is marked specially in the ELF file. On the first invocation, the dynamic linker actually calls the function and then takes the return value and treats it as a function pointer. This function pointer is then used for linking, so that subsequent invocations will call that pointer instead. The memcpy() function in glibc then simply checks which SIMD extensions are available and returns a pointer to the appropriate real memcpy to use.