Date: Tue, 6 Dec 2016 10:43:29 -0300
From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: "Wangnan (F)" <wangnan0@huawei.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>,
        Alexei Starovoitov <alexei.starovoitov@gmail.com>, ast@fb.com,
        lizefan@huawei.com, hekuang@huawei.com, Ingo Molnar <mingo@kernel.org>,
        linux-kernel@vger.kernel.org, pi3orama@163.com, joe@ovn.org,
        Jiri Olsa <jolsa@kernel.org>
Subject: Re: [PATCH v3 10/30] perf clang: Add builtin clang support ant test
 case
Message-ID: <20161206134329.GE28260@kernel.org>
References: <20161126070354.141764-1-wangnan0@huawei.com>
 <20161126070354.141764-11-wangnan0@huawei.com>
 <20161202154440.GB5931@redhat.com>
 <20161205165055.GB79989@ast-mbp.thefacebook.com>
 <20161205210248.GA2247@redhat.com>
 <20161205214832.GB2247@redhat.com>
 <58461D77.8070202@huawei.com>
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Em Tue, Dec 06, 2016 at 10:07:51AM +0800, Wangnan (F) escreveu:
> On 2016/12/6 5:48, Arnaldo Carvalho de Melo wrote:
> > Em Mon, Dec 05, 2016 at 07:02:48PM -0200, Arnaldo Carvalho de Melo escreveu:
> > > Em Mon, Dec 05, 2016 at 08:51:01AM -0800, Alexei Starovoitov escreveu:
> > > > yeah. it's kinda high. I'm guessing rpm llvm libs are in debug mode.
> > > > Try llvm-config --build-mode --assertion-mode
> > > > it should be Release OFF
> > > Probably this was with 3.9 and built from git, quite a while ago, now I
> > > removed it from /usr/local/ and installed what is in f25, but I fear it
> > > will be insufficient, does 3.8 cuts it for what we're testing? Humm, it
> > > looks like it will:

> > > [root@jouet ~]# llc --version
> > > LLVM (http://llvm.org/):
> > >    LLVM version 3.8.0

> > > But I'm now running the container based tests to send a pull req, will
> > > check later, after that.
> > Not really, Wang, we need to update that feature detection test to state what
> > is the minimum required LLVM/clang version, one that has those functions,
> > which, unfortunately, isn't the one in the latest fedora, fedora 25:
 
> I'll set the minimum required LLVM version to 3.9, and report
> warning when LLVM is too old. However, since LLVM interface is
> keep changing, finally we will have problem if we want to support
> 2 or 3 different clang/LLVM. We should keep moving minimum
> requirement LLVM version if we don't want to see '#ifdef's
> spread in our code.

If this area is in that much flux, I see no problem in us both not
enabling this by default, which is the case right now, and go on moving
the minimum required version for LLVM/clang, hopefully at some point
this will get stable and widely available (as in what distros ship),
when we then switch to doing the feature detection automatically.

I see you already submitted the patch to do this test, thanks, will
check and continue processing your series.

- Arnaldo