> They only execute instructions when they happen... but they still inhibit the optimizer when they don't. Calls that may throw act like branches in the control

> They only execute instructions when they happen... but they still inhibit the optimizer when they don't. Calls that may throw act like branches in the control flow graph. This is a fair point and elucidates the trade off being made. Perhaps this is the reason C++11 has the “nothrow” attribute.