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Re: question regarding div / std::div implementation

On Wed, Apr 20, 2016 at 7:10 PM, Paul Eggert <> wrote:
> On 04/20/2016 02:55 PM, Daniel Gutson wrote:
>> That fools the compiler.
> Yes, bizarre C code can fool the compiler. I was talking about realistic
> code, not contrived examples.

No need to be bizarre (I just wanted to exaggerate). Code by not
knowledgeable programmers,
or simply programmers that don't know that such optimization exists
(that requires that both lines have to be written adjacent)
will miss the optimization.

> glibc itself uses % and / in places where div/ldiv/lldiv might plausibly be
> used internally, and this is portable and maintainable and efficient and
> there is no real reason to change this, even if div/ldiv/lldiv were tuned.
> Similarly for other C applications.

This discussion has already moved to the compiler arena. Once the
builtins are implemented,
you glibc maintainers may want to consider changing that in order to
use those functions, or not.
In any case, code already using the div/ldiv/lldiv functions will be
benefited, and that's already something good.

Thanks for your feedback.



Daniel F. Gutson
Engineering Manager

San Lorenzo 47, 3rd Floor, Office 5
CÃrdoba, Argentina

Phone:   +54 351 4217888 / +54 351 4218211
Skype:    dgutson

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