Re:Investigating the Performance Overhead of C++ Exceptions
by daemin on Thursday February 13, 2020 @07:32AM
(#22317211)
The fact that just enabling exceptions adds a non-zero cost to the runtime of your program, even if the code itself does not use them, means that they are slower than just checking the return values. I've seen values from 5% to 15% slower runtime performance for just enabling exceptions and not even using them. I don't think removing the error checks will give you back those percentages.
The problem with proving something like this is you have to build and maintain two separate sets of code for the same project, one that uses exceptions in the correct manner, and another which does error checking to the same degree. Nobody has time to do that for a significant project.
The time to run exceptions is a lot less than to run failure checks, except in extreme cases as in the synthetic (not to say phony) benchmark presented. If the time spent throwing matters, you're Doing It Wrong.
The branch prediction slots that failure checks burn are rare and precious: much bigger than a general purpose register, and much faster than L1 cache. Blowing your branch prediction cache has costs hard to measure, although the perf registers help some.
The only substantial cost is object-code file size, and that mainly because precious little effort has been spent to minimize it, because really hardly anybody (i.e., only embedded) cares.