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Using __builtin_add_overflow and friends for overflow checking

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Lukas Mai
October 23, 2017 21:34
Using __builtin_add_overflow and friends for overflow checking
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I think it would be a good idea to use compiler intrinsics for overflow 
checks where available.

I've pushed a branch that implements this at mauke/overflow:

Dave: I've CC'd you directly because you last worked on this code 
(commit 230ee21f3e366901ce5769d324124c522df7ce8a, "faster add, subtract, 

My changes affect pp_add, pp_subtract, and pp_multiply. I think the new 
code is nicer because it's easier to understand than all the low-level 
bit fiddling, and it passes all tests on my machine. However, I haven't 
done any benchmarks to see how it affects performance (if at all).

Things I need help with:

- code review
- testing on different platforms / architectures
- benchmarks (compared to a17768d7c7b82c136fbeacd85db3451973a8007a)

Lukas Mai <>

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