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Date: Sat, 8 Apr 2017 16:57:04 +0200
From: Szabolcs Nagy <nsz@...t70.net>
To: musl@...ts.openwall.com
Subject: Re: byteswap.h
* Joakim Sindholt <opensource@...sha.com> [2017-04-07 20:07:42 +0200]:
> On Fri, Apr 07, 2017 at 07:53:09PM +0200, fab10 wrote:
> > I had a look at byteswap.h and it seems to me that the code is not very
> > efficient. Every function in this header could be translated in a single
> > assembly instruction with the gcc intrinsics:
> >
> > __builtin_bswap16
> > __builtin_bswap32
> > __builtin_bswap64
> >
> > Is there a reason to not use these gcc intrinsics?
> >
> > Bye
> >
>
> While musl does employ GNU C features in quite a few places it's just
> plain unnecessary here.
>
rarely in public headers though which have to
be portable to all c source parser tools.
builtins would need to be conditional on __GNUC__
and we still need the portable code as a fallback
which is harder to maintain and test
> https://godbolt.org/g/eLZWwI
>
> When optimized those functions yield a single bswap instruction anyway,
> because GCC is smart enough to deduce this.
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