Here is another rather big example of how C++ is WAY slower than assembler (picture)

Sure - std::copy is convenient
but asm is just way faster.
This code should be compatible with EVERY x86_64 CPU.

I even do duffs device without having the loop:
the loop happens in the rep opcode which allows for prefetching (meaning that it doesnt destroy the prefetch queue and can even allow for preprocessing).

BTW: for those who commented on my comment porn last time: I made sure to satisfy your cravings ;-)

To those who can't make sense of my command line:

C++ 1m24s
ASM 19s

To those who tell me to call clang with -o<something>:
1) clang removes the call to copy on o3 or o2
2) the result isnt better in o1 (well... one second but that might be due to so many other things, and even if... one second isn't that much)