The metric is SPEED not just easier development [LWN.net]

The metric is SPEED not just easier development

Posted Mar 27, 2008 10:56 UTC (Thu) by nix (subscriber, #2304)
In reply to: The metric is SPEED not just easier development by khim
Parent article: Striking gold in binutils

One point: RTTI and exception handling don't slow down C++ programs anymore, except if
dynamic_cast<> is used or exceptions are thrown, and those are things which if you implemented
them yourself you'd have a lot of trouble making as efficient as the compiler's implementation
(I doubt that you *can* make them as efficient or reliable without compiler support).

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Since WHEN?

Posted Mar 28, 2008 9:26 UTC (Fri) by khim (subscriber, #9252) [Link]

Last time we've checked (GCC 4.1.x) removal -fnortti and/or -fnoexceptions made real world programs 5-10% slower (up to 15% combined). What change happened in GCC 4.2 and/or GCC 4.3???

If you DO need RTTI and/or exceptions of course it's better to use compiler-provided ones, then to write your own, but if not... For things like gold abort() is perfectly usable alternative to the exceptions...

Since WHEN?

Posted Mar 28, 2008 21:26 UTC (Fri) by nix (subscriber, #2304) [Link]

I think I need to profile this, then, because exception frames should be 
very nearly free to set up and (non-throw) tear down, certainly not as 
expensive as 15%. This wasn't on an sjlj target, was it? 'cos they're *so* 
last millennium.