Integer Overflow Checking Cost
danluu.com32 points by iwsk 2 days ago
32 points by iwsk 2 days ago
Definitely cheaper than using Electron I would say
In Swift (Apple’s C++ successor), the normal operators (`+`, `-`, `*`) trap on overflow for integer types. If you want twos complement wrapping, you can use `&+`, `&-`, and `&*`.
Given that Apple has been making its own CPU cores for years now, I suspect overflowing checking on Apple CPUs is virtually free (aside from code size).
> Given that Apple has been making its own CPU cores for years now, I suspect overflowing checking on Apple CPUs is virtually free (aside from code size).
Never make guesses based on a particular programming language. In Apple's own C documentation (https://developer.apple.com/documentation/xcode/integer-over...) it is stated that "Overflows result in undefined behavior." and enabling wrapping behaviour "may adversely impact performance", indicating that overflow detection is in fact not "virtually free".
Code size (and branch table entries) are not free, of course. The other thing to note is that trapping operators often need to trap precisely which can lead to missed optimizations.
2014 (probably? Or 2008. Old and no date) Previously (166 points, 2014, 107 comments) https://news.ycombinator.com/item?id=8765714
Resubmitting it seems timely, given recent Linux kernel news (e.g. https://lwn.net/Articles/1065889/).
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