Re: toolchain/54428: GCC broken with std::atomic<__int128_t> with -mcx16

[Kamil Rytarowski <n54%gmx.com@localhost>]

The following reply was made to PR toolchain/54428; it has been noted by GNATS.

From: Kamil Rytarowski <n54%gmx.com@localhost>
To: gnats-bugs%netbsd.org@localhost
Cc: 
Subject: Re: toolchain/54428: GCC broken with std::atomic<__int128_t> with
 -mcx16
Date: Fri, 2 Aug 2019 15:04:01 +0200

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 From: Kamil Rytarowski <n54%gmx.com@localhost>
 To: gnats-bugs%netbsd.org@localhost
 Message-ID: <27806673-394e-99cb-702a-fc66487dcc6a%gmx.com@localhost>
 Subject: Re: toolchain/54428: GCC broken with std::atomic<__int128_t> with
  -mcx16
 References: <pr-toolchain-54428%gnats.netbsd.org@localhost>
  <20190801181032.8C15A7A1B4%mollari.NetBSD.org@localhost>
  <20190802052001.66A417A1BB%mollari.NetBSD.org@localhost>
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 On 02.08.2019 07:20, Martin Husemann wrote:
 > The following reply was made to PR toolchain/54428; it has been noted b=
 y GNATS.
 >=20
 > From: Martin Husemann <martin%duskware.de@localhost>
 > To: gnats-bugs%netbsd.org@localhost
 > Cc:=20
 > Subject: Re: toolchain/54428: GCC broken with std::atomic<__int128_t> w=
 ith
 >  -mcx16
 > Date: Fri, 2 Aug 2019 07:15:59 +0200
 >=20
 >  On Thu, Aug 01, 2019 at 06:15:01PM +0000, n54%gmx.com@localhost wrote:
 >  > 1. Revisit the libatomic statement and ship it to those who are awar=
 e about its corner cases.
 >  >=20
 >  > 2. Patch GCC to support 128bit std::atomic without libatomic and reu=
 se lock cmpxchg16b on x86_64.
 > =20
 >  3. do not support std::atomic<__int128_t> at all on amd64
 >  (patch headers to generate an explicit error, or add lib stubs that ma=
 ke
 >  it error out at link time)?
 > =20
 
 It already errors with GCC.
 
 Why to reject it? Relatively recent amd64 does support this operation
 natively in hardware.
 
 > =20
 >  Martin
 > =20
 >=20
 
 
 
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