Comment 3 for bug 638014

I think the compiler is only free to do this kind of optimization with standard library functions. memclr and bzero are not in the standard, and so cannot be relied upon. Indeed, the bzero man page says it is deprecated and users should use memset.

However, __aeabi_memclr is probably fair game - it's documented in the ARM EABI, and that makes it standard in our world. Obviously, this would have to be not only ARM specific, but EABI-specific.