Comment by Someone

And “happen to work on x86-64 processors” also will depend on the compiler. If you write

  *a = 1;
  *b = 'p';

both the compiler and the CPU can freely pick the order in which those two happen (or even execute them in parallel, or do half of one first, then the other, then the other half of the first, but I think those are hypothetical cases)

x86-64 will never do such a swap, but x86-64 compilers might.

If you write

  *a = 1;
  *b = 2;

, things might be different for the C compiler because a and b can alias. The hardware still is free to change that order, though.