trick fast

inline int abs(int x)
{
    return (x<0) ? -x : x;
}

Which is simple enough but contains an inline if-then-else. As the argument, x, isn’t all that likely to follow a pattern that the branch prediction unit can detect, this simple function becomes potentially costly as the jump will be mispredicted quite often.

How can we remove the if-then-else, then? One solution is to use the right shift operator (>>) and the bitwise XOR operator (^) as following:

inline int abs_no_branch(int x)
{
  int m = (x >> (8 * sizeof(int)-1));
  return ((x ^ m) - m);
}