Why does this code generate much more assembly than equivalent C++/Clang? [closed]

Answer 1

Compiling with -C opt-level=3 in godbolt gives:

example::f1:
  push rbp
  mov rbp, rsp
  xor dil, 1
  or dil, sil
  mov eax, edi
  pop rbp
  ret

Which looks comparable to the C++ version. See Lukas Kalbertodt's answer for more explanation.

Note: I had to make the function pub extern to stop the compiler optimising it to nothing, as it is unused.