From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-1.mimecast.com (us-smtp-1.mimecast.com [205.139.110.120]) by mx.groups.io with SMTP id smtpd.web10.20806.1590177729199224107 for ; Fri, 22 May 2020 13:02:09 -0700 Authentication-Results: mx.groups.io; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=AWvEIwSJ; spf=pass (domain: redhat.com, ip: 205.139.110.120, mailfrom: lersek@redhat.com) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1590177728; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=s87n9wYtLSM5000CIQM6H4w7tEOXWUPSw4LejdFvt70=; b=AWvEIwSJj141lG17igQ911no6m++T0JWlr7ReZdX0LQAVDTl33SQlNyjS82hfeFoVTcZWU xzOx4iHWKWC+MlZo0nQ/kGoqWyMCv1YbISG0kQQDDkafDa2DyUZyrrF0mM3epH94AR7QTh 3sRnxdbXKjpPBjxvmbOJkNLYcAm/fTk= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-492-5tj5hy6bO3OpPElT75Z-Zw-1; Fri, 22 May 2020 16:01:56 -0400 X-MC-Unique: 5tj5hy6bO3OpPElT75Z-Zw-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id AC68A1855A15; Fri, 22 May 2020 20:01:55 +0000 (UTC) Received: from lacos-laptop-7.usersys.redhat.com (ovpn-112-40.ams2.redhat.com [10.36.112.40]) by smtp.corp.redhat.com (Postfix) with ESMTP id 2F771619C0; Fri, 22 May 2020 20:01:54 +0000 (UTC) Subject: Re: [PATCH] MdePkg/Include: AARCH64: disable outline atomics on GCC 10.2+ To: Ard Biesheuvel , devel@edk2.groups.io Cc: liming.gao@intel.com, leif@nuviainc.com, philmd@redhat.com, mliska@suse.cz References: <20200522101202.15016-1-ard.biesheuvel@arm.com> From: "Laszlo Ersek" Message-ID: <36effdcd-91a7-da00-855d-570e64d650b8@redhat.com> Date: Fri, 22 May 2020 22:01:53 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20200522101202.15016-1-ard.biesheuvel@arm.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit On 05/22/20 12:12, Ard Biesheuvel wrote: > GCC 10 enabled a feature by default that was introduced in GCC 9, > which results in atomic operations to be emitted as function calls > to intrinsics provided by a runtime library. > > Atomics are hardly used in EDK2, which runs on a single CPU anyway, > and any benefit that would result from reusing library code that > implements these operations is defeated by the fact that every EDK2 > module will need to have its own copy anyway. > > So let's disable this feature on GCC versions that support the > pragma to do so (GCC 10.2 and up) > > Link: https://bugzilla.tianocore.org/show_bug.cgi?id=2723 > Signed-off-by: Ard Biesheuvel > --- > The GCC support for this pragma has already been pulled into the 10.2 > release branch. I think we should consider adding this to the stable > tag, so that the issue can easily be resolved by upgrading the compiler. > Whether we add the intrinsics too is a separate matter, but we can > revisit that later. > > MdePkg/Include/AArch64/ProcessorBind.h | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/MdePkg/Include/AArch64/ProcessorBind.h b/MdePkg/Include/AArch64/ProcessorBind.h > index 896bf273ac7a..a3ca8f09e51c 100644 > --- a/MdePkg/Include/AArch64/ProcessorBind.h > +++ b/MdePkg/Include/AArch64/ProcessorBind.h > @@ -24,6 +24,17 @@ > #pragma pack() > #endif > > +#if defined(__GNUC__) && !defined(__clang__) > + > +// > +// Disable GCC outline atomics > +// Link: https://bugzilla.tianocore.org/show_bug.cgi?id=2723 > +// > +#if __GNUC__ > 10 || (__GNUC__ == 10 && __GNUC_MINOR__ >= 2) > +#pragma GCC target "no-outline-atomics" > +#endif > +#endif > + > #if defined(_MSC_EXTENSIONS) > > // > Reviewed-by: Laszlo Ersek But I think it should be merged later, after GCC 10.2 is out. (Obviously I don't "insist" that we follow this approach, I'm just OK with it.) Thanks Laszlo