Note: in some cases (not completely sure if it applies in this situation as I haven't looked into the details of this code enough), using pre-increment AND when the value is used is a dependency on that operation, so "+= 1" is actually faster for out of order execution.

So yeah, as you say, compilers can be very sensitive to this, and in the past (although more than 10 years ago now, so might not be relevant now), ICC often used to generate better (faster executing) code when using "val += 1" vs "++val".