[OT] The Usual Arithmetic Confusions
Ola Fosheim Grøstad
ola.fosheim.grostad at gmail.com
Mon Jan 31 16:42:32 UTC 2022
On Monday, 31 January 2022 at 16:09:33 UTC, Ola Fosheim Grøstad
> On Monday, 31 January 2022 at 11:00:26 UTC, Elronnd wrote:
>> Please show me a case where it matters. I already asked for
>> this: show me a case where a large-scale c or c++ application
>> performs appreciably better because signed overflow is UB. It
>> is easy to test this: simply tell gcc or clang -fwrapv and
>> they will stop treating overflow as UB.
> I've already answered this. You can say this about most
> individual optimizations. That does not mean that they don't
> have an impact when you didn't get them.
That sentence came out wrong.
What I meant is that missing an optimization is impactfull where
it matters. In this case I pointed out that this is most
impactfull in inner loops, but that current C/C++ codebases tend
not to use high level programming in performance sensitive
Meaning: the whole argument you are presenting is pointless. You
will obviously not find conditionals that are always true/false
in handt-tuned inner loops.
The crux is this: people don't want to hand tune inner loops if
they can avoid it!
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