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Date: Wed, 4 Dec 2013 10:40:21 +0100
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Subject: Fwd: nonportable-atomics configure.in setting
From: Yann Ylavic <ylavic.dev@gmail.com>
To: dev@httpd.apache.org
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Sorry, I had no intention to send this offlist.

---------- Forwarded message ----------
From: Yann Ylavic <ylavic.dev@gmail.com>
Date: Wed, Dec 4, 2013 at 10:37 AM
Subject: Re: nonportable-atomics configure.in setting
To: Daniel Lescohier <daniel.lescohier@cbsi.com>


On Wed, Dec 4, 2013 at 1:22 AM, Daniel Lescohier
<daniel.lescohier@cbsi.com>wrote:

> I see this in configure.in:
>
> AC_ARG_ENABLE(nonportable-atomics,
> [  --enable-nonportable-atomics  Use optimized atomic code which may
> produce nonportable binaries],
> [if test $enableval = yes; then
>    force_generic_atomics=no
>  else
>    force_generic_atomics=yes
>  fi
> ],
> [case $host_cpu in
>    i[[456]]86) force_generic_atomics=yes ;;
>    *) force_generic_atomics=no ;;
> esac
> ])
>
> I was wondering why the three host_cpus i486, i586, and i686 have special
> treatment for the default setting as compared to all other cpu
> architectures?
>
>
I don't see any reason since the code in "srclib/apr/atomic/unix/ia32.c"
seems compatible with >i386 (cmpxchg starts with i486), and atomic builtins
work with gcc-v2+ (at worst USE_ATOMICS_IA32 could be defined for gcc-v1).

The issue could have been in apr_atomic_casptr() and apr_atomic_xchgptr(),
but APR_SIZEOF_VOIDP is checked to do the right thing with 32bits cpus...

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<div dir=3D"ltr"><div class=3D"gmail_default" style=3D"font-family:arial,he=
lvetica,sans-serif">Sorry, I had no intention to send this offlist.<br></di=
v><br><div class=3D"gmail_quote">---------- Forwarded message ----------<br=
>From: <b class=3D"gmail_sendername">Yann Ylavic</b> <span dir=3D"ltr">&lt;=
<a href=3D"mailto:ylavic.dev@gmail.com" target=3D"_blank">ylavic.dev@gmail.=
com</a>&gt;</span><br>

Date: Wed, Dec 4, 2013 at 10:37 AM<br>Subject: Re: nonportable-atomics <a h=
ref=3D"http://configure.in" target=3D"_blank">configure.in</a> setting<br>T=
o: Daniel Lescohier &lt;<a href=3D"mailto:daniel.lescohier@cbsi.com" target=
=3D"_blank">daniel.lescohier@cbsi.com</a>&gt;<br>

<br><br><div dir=3D"ltr"><div><div>On Wed, Dec 4, 2013 at 1:22 AM, Daniel L=
escohier <span dir=3D"ltr">&lt;<a href=3D"mailto:daniel.lescohier@cbsi.com"=
 target=3D"_blank">daniel.lescohier@cbsi.com</a>&gt;</span> wrote:<br>
</div></div><div class=3D"gmail_extra"><div><div><div class=3D"gmail_quote"=
>

<blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-=
left:1px solid rgb(204,204,204);padding-left:1ex"><div dir=3D"ltr"><div>I s=
ee this in <a href=3D"http://configure.in" target=3D"_blank">configure.in</=
a>:<br>


<br>AC_ARG_ENABLE(nonportable-atomics,<br>[=A0 --enable-nonportable-atomics=
=A0 Use optimized atomic code which may produce nonportable binaries],<br>
[if test $enableval =3D yes; then<br>=A0=A0 force_generic_atomics=3Dno<br>=
=A0else<br>=A0=A0 force_generic_atomics=3Dyes<br>=A0fi<br>],<br>[case $host=
_cpu in<br>=A0=A0 i[[456]]86) force_generic_atomics=3Dyes ;;<br>=A0=A0 *) f=
orce_generic_atomics=3Dno ;;<br>


esac<br>])<br><br></div>I was wondering why the three host_cpus i486, i586,=
 and i686 have special treatment for the default setting as compared to all=
 other cpu architectures?<br><br></div>
</blockquote></div><br></div></div><div style=3D"font-family:arial,helvetic=
a,sans-serif">I don&#39;t see any reason since the code in &quot;srclib/apr=
/atomic/unix/ia32.c&quot; seems compatible with &gt;i386 (cmpxchg starts wi=
th i486), and atomic builtins work with gcc-v2+ (at worst USE_ATOMICS_IA32 =
could be defined for gcc-v1).<br>


</div><br><div style=3D"font-family:arial,helvetica,sans-serif">The issue c=
ould have been in apr_atomic_casptr() and apr_atomic_xchgptr(), but APR_SIZ=
EOF_VOIDP is checked to do the right thing with 32bits cpus...<br>

</div><br></div></div>
</div><br></div>

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