memory - intrinsic memcmp

Question

According to the gcc docs, memcmp is not an intrinsic function of GCC. If you wanted to speed up glibc's memcmp under gcc, you would need to use the lower level intrinsics defined in the docs. However, when searching around the internet, it seems that many people have the impression that memcmp is a builtin function. Is it for some compilers and not for others?

Answer 1

Note that the repz cmpsb routine might not be faster than glibc's memcmp. In my tests, in fact, it's never faster, even when comparing just a few bytes.

See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43052