[llvmlinux] LLVMLinux Meeting 2013-09-04

Behan Webster behanw at converseincode.com
Mon Sep 9 16:52:51 UTC 2013


*

LLVMLinux Project: http://llvm.linuxfoundation.org/


<http://llvm.linuxfoundation.org/>

This week the meeting will be on Thursday, September 4 2013 on Google 
Plus Hangout at 16:00 
UTC.<https://www.google.com/calendar/embed?src=su5vu85fj58ncfrgalmq4vbbf0%40group.calendar.google.com&ctz=GMT>


<https://www.google.com/calendar/embed?src=su5vu85fj58ncfrgalmq4vbbf0%40group.calendar.google.com&ctz=GMT> 


If you haven't use G+ Hangouts before, make sure you have the 
appropriate Chrome or Firefox plugin installed, and tested before the 
time of the meeting. You can try a test hangout with me today before the 
meeting if you want to. G+ recently changed, so hopefully that won't be 
an issue for our meeting.


-------------------------------------------------------------------------------------------------------------------------

Previous meeting's top 2-3 work items:

  *

    This is what people said they'd be working on at the end of the last
    meeting:

      o

        Behan

          +

            LLVM uConf organization and proposal reviews

          +

            Upstreaming kernel patches

          +

            Update talk for LinuxConf North America

          +

            Support Eduard for new clang checkers for Linux Kernel

      o

        Eduard

          +

            Implement checkers inspired by sparse/coccinelle

          +

            Check out tinti's uint32 => uint16 idea

          +

            try out nexus4 kernel images

          +

            get started on plumbers talk

      o

        Jan-Simon

          +

            vexpress bot

          +

            Upstreaming

          +

            Write talk for Plumbers

      o

        Tinti

          +

            Fix the ARM issue on vexpress and other ARM targets

              #

                Already fixed

          +

            Add GDB tutorial on Wiki

          +

            Get our build system working in Gentoo

              #

                Tim reported that he has faced issues to get it working.

-------------------------------------------------------------------------------------------------------------------------

Agenda for this week:


  *

    (5 mins total) Everyone shared a quick summary of the progress
    they've made from the last 4 weeks

      o

        Behan

          +

            Worked on upstreaming kernel patches

          +

            New "for-linus" target which includes ALL patches from
            default x86_64.defconfig

          +

            New llvmlinux/kernel.git repo

          +

            A lot of work herding speakers for the LLVM uConf for Linux
            Plumbers

          +

            Started talk for LCNA

          +

            Most of the arm64 port

      o

        Bernard

          +

            Daily LLVM 3.4 builds for Linaro

          +

            Port Android userland

          +

            Prepare LPC talk

          +

            Looked at Polly (http://polly.llvm.org/), will integrate it
            into future daily builds

      o

        Mark

          +

            New VLAIS patch for netfilter

          +

            Work on Plumbers talk

      o

        Eduard

          +

            Get first checker out

          +

            Do slides for talk at plumbers

      o

        Jan-Simon

          +

            Fixed vexpress bot

              #

                http://buildbot.llvm.linuxfoundation.org/checker/

              #

                http://buildbot.llvm.linuxfoundation.org/checker/scan-build-latest/

          +

            Upstreamed 2 patches

          +

            Write talk for Plumbers

      o

        Vinicius Tinti

          +

            Fixed ARM issue on vexpress target

              #

                It was really an old issue that was not triged before.

              #

                Special thanks to Tim Northover and Joey

          +

            Fixed Nexus 7 build

              #

                Nexus 7 is being build from head now.

          +

            Postponed

              #

                Wiki tutorial

              #

                Gentoo

      o

        Renato

          +

            Writing a document on how to cross-compile, options, and a
            full example on how to cross-compile from x86 to ARM

          +

            Aligning options that accept CPU with each other, fixing
            some bugs in the process

          +

            ARM 64 bit emulator

              #

                http://www.arm.com/products/tools/models/fast-models/foundation-model.php

          +

            Linaro AArch64

              #

                http://www.linaro.org/engineering/engineering-projects/armv8

  *

    (45 mins) General meeting discussions:

      o

        LLVM update (current wish list)

          +

            Tim Northover along with Vinicius and Renato fixed mainline
            clang so it works for ARM again with the Linux kernel
            (vexpress and Nexus 7)

          +

            Clang+LLVM head for x86_64 is still broken (SSE issues in
            Real mode at boot time)

          +

            Behan spoke to Chandler Carruth over the weekend. He is keen
            to help us where possible, including advocacy to the kernel
            team where he works.

          +

            From past weeks, still valid until further notice:

              #

                The decision during the last meeting was that for the
                near future (up until Linux Plumbers at least) people
                should use LLVM/Clang v3.3 and concentrate on
                upstreaming kernel fixes where ever possible. Since
                kernel developers can now use a stock compiler, it's
                important that we get the kernel patches into mainline.

              #

                This doesn't mean that people can't work on LLVM/Clang,
                just that the focus has moved from Clang to the kernel

              #

                All kernel upstreaming is currently being performed with
                LLVM 3.3

      o

        Kernel Patch triage (highest priority now)

          +

            Kernel 3.12 merge window should now be open

          +

            Patches will be pushed to a kernel tree for kernel devs to
            play with

          +

            Patch review

          +

            wait/wound mutexes use __builtin_constant_p which breaks
            clang (kernel doesn't boot without this update removed or
            patched out)

              #

                The author of the code claims the use of
                __builtin_constant_p provides an optimization, but it
                seems to be a misuse

              #

                __builtin_constant_p strictly speaking should be used to
                detect constant pointers (instead of constant compares
                as in this case) and should provide a failure path
                (which it doesn't seem to).

          +

            ARM64 port in progress:

              #

                ARM64 emulator available

              #

                http://www.arm.com/products/tools/models/fast-models/foundation-model.php

              #

                http://www.linaro.org/engineering/engineering-projects/armv8

          +

            From past weeks, still in progress:

              #

                This should now be the focus of our combined efforts for
                the next month or so.

              #

                Behan and Jan-Simon have been triaging, fixing and
                upstreaming patches

              #

                The best way to participate in upstreaming patches is
                with the following spreadsheet. Ask for access if you
                want to be able to update it

              #

                https://docs.google.com/spreadsheet/ccc?key=0Ao2VHhaw1DTqdERLUDBmVlpiY2pUNUlLa1k3ck1Zc1E#gid=0

              #

                The above spreadsheet has the most up to date info about
                each patch in the LLVMLinux repo, what needs to be done,
                and what state it's in.

              #

                Patches have been divided into patches which will be
                sent to Linus Torvalds at the end, patches which are
                required, but can be upstreamed separately, patches
                which don't strictly matter for now (which have been
                archived) and other (which are being sorted into the
                other categories, or being made obsolete).

              #

                A number of patches have been rewritten to be upstream-able.

              #

                Once non-upstreamable patches have been fixed, they will
                be sent to Bruce Ashfield (yocto) (Real Soon Now!).

      o

        LLVMLinux build system

          +

            Nothing changed in the past weeks

          +

            A request for gentoo support, Eduard says it mostly works
            with gentoo and arch

      o

        Merged globals/section mismatches update

          +

            Still needs more investigation (has been low priority for
            many months)

          +

            Investigation so far
            https://lftraining.dyndns.org/pad/p/llvm-section-mismatch

          +

            These dropped attributes mess up where init and exit code is
            linked which is causing the section mismatches

      o

        Tools

          +

            Clang Static Analyzer

              #

                TBD

              #

                New build targets have been added to LLVMLinux mainline:
                kernel-scan-build and kernel-check-build

              #

                Full x86_64 builds are currently failing due to apparent
                out-of-memory problems (clang or perl might be causing
                the problem)

              #

                Eduard and Jan-Simon are working to find the issue

              #

                vexpress builds now work with clanf static analyzer
                (LLVM v3.3)

              #

                The latest demo checker can be seen here:
                http://buildbot.llvm.linuxfoundation.org/checker/scan-build-latest/

              #

                Many false positives have been removed

              #

                Eduard is now working on writing custom checkers for the
                kernel

      o

        Linaro Connect

          +

            Renato is pushing LLVM and LLVMLinux at Linaro Connect

      o

        LLVM micro conference at Linux Plumbers Conference

          +

            Linux Plumbers coming up in 2 weeks!

          +

            We have 3h30m for 7 speakers!

          +

            There are 2 time slots (LLVM1, and LLVM2)

              #

                LLVM1 (2h30m):
                http://www.linuxplumbersconf.org/2013/ocw/events/LPC2013/tracks/171

              #

                LLVM2 (1h):
                http://www.linuxplumbersconf.org/2013/ocw/events/LPC2013/tracks/219

          +

            All speakers (to Behan's knowledge) have registered (Which
            is good because registration is otherwise closed)

  *

    (5 mins) Each meeting attendee listed the top 2 items to be worked
    on for the next 2 weeks

      o

        Behan

          +

            Any last minute LLVM uConf organization

          +

            Upstreaming kernel patches

          +

            Following up with Linus

          +

            Update talk for LinuxConf North America

          +

            Support Eduard for new clang checkers for Linux Kernel

      o

        Bernhard

          +

            LPC talk

          +

            3.4 Android userland build

      o

        Eduard

          +

            Checkers, checkers, checkers!

          +

            LPC talk

      o

        Jan-Simon

          +

            Talk for Plumbers

          +

            Patchwork

          +

            x86 + clang HEAD

          +

            Section issues

      o

        Mark

          +

            VLAIS slides

          +

            Look at section issue with Vinicius

          +

            Verify current build state for vexpress

      o

        Tinti

          +

            Work on "Merged globals/section mismatches update" with JSM
            and Mark

          +

            Add documentation to wiki

          +

            Add gentoo


Next meeting in 2-ish weeks. doodle poll to follow.

*

-- 
Behan Webster
behanw at converseincode.com

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