There are hints for taken/non-taken branches in x86. However, the only family to use them was Pentium 4; other processors silently ignore those hints. As for t

There are hints for taken/non-taken branches in x86. However, the only family to use them was Pentium 4; other processors silently ignore those hints. As for the write side, you'll find it here: https://opensource.apple.com/source/libdispatch/libdispatch-339.90.1/src/once.c https://opensource.apple.com/source/libdispatch/libdispatch-...