Don't do arithmetic on anything smaller than 'int' (was: [PATCH v2] ice: use min_t() to make code cleaner in ice_gnss)

[Paul Menzel]

Dear Linux folks,


Am 22.03.22 um 19:27 schrieb Jakub Kicinski:
> On Tue, 22 Mar 2022 18:12:08 +0000 David Laight wrote:
> > > > Oh FFS why is that u16?
> > > > Don't do arithmetic on anything smaller than 'int'
> > >
> > > Any reasoning? I don't say it's good or bad, just want to hear your
> > > arguments (disasms, perf and object code measurements) etc.
> >
> > Look at the object code on anything except x86.
> > The compiler has to add instruction to mask the value
> > (which is in a full sized register) down to 16 bits
> > after every arithmetic operation.
>
> Isn't it also slower on some modern x86 CPUs?
> I could have sworn someone mentioned that in the past.

I know of Scott’s article *Small Integers: Big Penalty* from 2012 [1].


Kind regards,

Paul


[1]: https://notabs.org/coding/smallIntsBigPenalty.htm
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