Re: Using __builtin_expect (likely/unlikely macros)

[John Carter <john.carter@taitradio.com>]

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As a small datapoint I recently converted the largish (about 2megasloc)
code base I maintain to using likely/unlikely.

I have been very pleasantly surprised by how much more readable it made the
__builtin's..

And then surprised again by how much more readable it makes code in general.

I now occasionally add them to my code, not so much as an optimization
hint, but as documentation to indicate the expected "Happy Path".

In fact, so much so, I find interesting those cases where I consider it....
and then say, meh, I don't know which path is more likely...



On Mon, Apr 15, 2019 at 1:19 PM Paul Eggert <eggert@cs.ucla.edu> wrote:

> Alex Gramiak wrote:
> > the likely/unlikely
> > macros are a nice way to indicate that a branch is exceedingly
> > rare/common.
>
> The cost (in making the C code harder to read, write and maintain) so
> often
> exceeds that benefit that I'd rather avoid these macros unless there's a
> good
> performance case for putting them in.
>
>

-- 
John Carter
Phone : (64)(3) 358 6639
Tait Electronics
PO Box 1645 Christchurch
New Zealand

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