> -----Original Message-----
> From: Damjan Marion <dmar...@me.com>
> Sent: 2020年5月12日 0:46
> To: Lijian Zhang <lijian.zh...@arm.com>
> Cc: vpp-dev <vpp-dev@lists.fd.io>; nd <n...@arm.com>
> Subject: Re: [vpp-dev] clang-9
> 
> 
> Hi Lijian,
> 
> If I got it right, neither gcc or clang available in ubuntu 18.04 LTS are 
> able to
> produce N1 optimised binaries. correct?
Yes, that's right. Support for optimized compiling for N1 starts with gcc-9.2.0 
and clang-10, which are not available in Ubuntu-18.04 yet.
> 
> If yes, can we just add clang-10 from: https://apt.llvm.org to vpp build 
> scripts?
> 
Currently clang-10/clang-11 Aarch64 packages are not available at apt.llvm.org 
yet. Arm compiler team is working on getting AArch64 packages available at 
apt.llvm.org. It may take a couple of weeks.
> In particular:
> 
> # 10
> deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-10 main deb-src
> http://apt.llvm.org/bionic/ llvm-toolchain-bionic-10 main
> 
> 
> Damjan
> 
> 
> > On 9 May 2020, at 12:12, Lijian Zhang <lijian.zh...@arm.com> wrote:
> >
> > Hi Damjan,
> > The patch[2] installs clang-9 in package dependencies and sets “clang-10
> clang-9 gcc-9 cc” as the default compiler.
> >
> > The problem is,
> > 1. clang-9 does not support ‘-mtune=qdf24xx’, ‘-mtune=neoverse-n1’, ‘-
> mcpu=neoverse-n1’, so it cannot do arch-specific compiling and optimal
> function selection for those two CPUs.
> > These options requires gcc-9.2, clang-10 and any newer versions.
> > 2. The clang package servers for Ubuntu-18.04 mentioned in
> https://apt.llvm.org/ support x86, but does not support Arm64, so we cannot
> install clang-10/clang-11 directly via apt commands on Arm servers.
> >
> > I’m thinking two options,
> > 1. remove clang-9 dependency in Makefile or add for x86_64 only, so that
> users should install clang-10/clang-9 for x86 manually, and for Arm, install 
> gcc-
> 9 and clang-10/clang-11(not available yet). Just like CSIT has to update gcc
> version to gcc-8.3 manually(gcc-8.3 not listed in dependencies) previously.
> > 2. there are other several workaround,
> >               2.1 install clang-10 from source code until we can do 
> > clang-10 binary
> install on Ubuntu-18.04 on Arm;
> >               2.2 keep the code as it is now, although it will disable 
> > multi-arch
> support for these two CPUs with clang-9;
> >               2.3 when we are developing code or doing benchmarking, we need
> to hack the code temporarily from “set(CMAKE_C_COMPILER_NAMES clang-
> 10 clang-9 gcc-9 cc)” to “set(CMAKE_C_COMPILER_NAMES clang-10 gcc-9 cc)”,
> so that multi-arch will be supported with gcc-9.
> >
> > Could you suggest on this issue?
> > Thanks.
> > From: vpp-dev@lists.fd.io <vpp-dev@lists.fd.io> On Behalf Of Damjan
> > Marion via lists.fd.io
> > Sent: 2020年4月28日 22:14
> > To: vpp-dev <vpp-dev@lists.fd.io>
> > Subject: [vpp-dev] clang-9
> >
> >
> > Folks,
> >
> > As there is bug in gnu assembler which is shipping with ubuntu 18.04 we are
> not able to produce working binaries with avx512 instruction set.
> > Because of that, I had to change default to avx2. reported bug[1], but it is
> ignored for a year.
> >
> > As alternative[2], I wanted to consider using clang-9 which is shipped with
> ubuntu 18.04 and seems like it is even capable of producing faster binaries
> than gcc.
> > Unfortunately, "make test" is failing at several places including vxlan, 
> > ipsec
> and tcp stack[3].
> >
> > May I ask folks who “own” that code to take a quick look?
> >
> > Thanks,
> >
> > Damjan
> >
> > [1]
> > https://bugs.launchpad.net/ubuntu/cosmic/+source/binutils/+bug/1819961
> > [2] https://gerrit.fd.io/r/c/vpp/+/26744
> > [3]
> > https://jenkins.fd.io/job/vpp-verify-master-ubuntu1804/3615/console
> >
> >
> >
> > 

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