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In-Reply-To: <ydd7dcesyb7.fsf@CeBiTec.Uni-Bielefeld.DE>
From: Jonathan Wakely <jwakely@redhat.com>
Date: Wed, 8 Dec 2021 19:21:22 +0000
Message-ID: <CACb0b4mK2+6Kit3ikEFpPEabZyy=e5Jq4kcj09mGOCZpR0P3oA@mail.gmail.com>
Subject: Re: [PATCH] libstdc++: Skip atomic instructions in
 _Sp_counted_base::_M_release when both counts are 1
To: Rainer Orth <ro@cebitec.uni-bielefeld.de>
Cc: Jonathan Wakely via Gcc-patches <gcc-patches@gcc.gnu.org>,
 "libstdc++" <libstdc++@gcc.gnu.org>
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On Wed, 8 Dec 2021 at 19:17, Rainer Orth wrote:
>
> Hi Jonathan,
>
> > I've pushed this change to trunk now (it was posted and reviewed in
> > stage 1, I just didn't get around to pushing it until now).
> >
> > The final version of the patch is attached to this mail.
>
> unfortunately, it breaks Solaris/SPARC bootstrap:
>
> In file included from /var/gcc/regression/master/11.4-gcc-gas/build/sparc=
-sun-solaris2.11/sparcv9/libstdc++-v3/include/bits/shared_ptr.h:53,
>                  from /var/gcc/regression/master/11.4-gcc-gas/build/sparc=
-sun-solaris2.11/sparcv9/libstdc++-v3/include/memory:77,
>                  from /vol/gcc/src/hg/master/local/libstdc++-v3/include/p=
recompiled/stdc++.h:82:
> /var/gcc/regression/master/11.4-gcc-gas/build/sparc-sun-solaris2.11/sparc=
v9/libstdc++-v3/include/bits/shared_ptr_base.h: In member function 'void st=
d::_Sp_counted_base<_Lp>::_M_release() [with __gnu_cxx::_Lock_policy _Lp =
=3D __gnu_cxx::_S_atomic]':
> /var/gcc/regression/master/11.4-gcc-gas/build/sparc-sun-solaris2.11/sparc=
v9/libstdc++-v3/include/bits/shared_ptr_base.h:329:26: error: right operand=
 of shift expression '(1 << 64)' is greater than or equal to the precision =
64 of the left operand [-fpermissive]
>   329 |             =3D 1LL + (1LL << (__CHAR_BIT__ * sizeof(_Atomic_word=
)));
>       |                     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~=
~
> make[9]: *** [Makefile:1875: sparc-sun-solaris2.11/bits/stdc++.h.gch/O2gg=
nu++0x.gch] Error 1
>
> For 64-bit SPARC, _Atomic_word is long.

Ah yes, so we need to disable this optimization. Patch coming up ...