[llvmlinux] LLVMLinux Meeting 2013-09-26 Minutes

Behan Webster behanw at converseincode.com
Fri Oct 4 22:46:20 UTC 2013


*

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


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

This week the meeting will be on Thursday, September 26 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

          +

            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

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

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

          +

            Getting ready for LinuxCon and Plumbers

          +

            Gave talk at LinuxCon

          +

            Ran LLVM microconference

          +

            Talked to many kernel devs about LLVM/clang

          +

            Followed up with many people from the conference

          +

            Working on upstreaming VLAIS patches with Mark

              #

                Mark

          +

            Spoke at LLVM microconference

          +

            Followed up with Paul McKenny

          +

            Re-submitted VLAIS gadget patch

              #

                2 versions: multiple kmalloc with no macros, and single
                kmalloc with macros

          +

            Investigated vexpress build issues

              #

                Merge window issue for vexpress

              #

                Problems with 3.3 vs 3.4 and -MT and -dependency-file

                  *

                    3.4 seems to require -MT before -dependency-file

                  *

                    Trying to make a unit test, will file a bug if isolated

              #

                Verified HEAD vexpress and prebuilt clang - seems to work

      o

        Eduard

          +

            Preparation for the conference

          +

            Talk at Plumbers/LLVM micronference (+ prep)

          +

            Investigating clang failure with static analyzer

          +

            Finalizing GSoC (evaluation, etc.)

      o

        Jan-Simon

          +

            Talk at Plumbers

          +

            w/w mutex fix (resolved with upstream, travelling into master)

          +

            sync x86

          +
      o

        Vinicius Tinti

          +

            Postponed

  *

    (45 mins) General meeting discussions:

      o

        ARM breakage with clang/llvm on master

          +

            iomap-b1b974.s:120: Error: junk at end of line, first
            unrecognized character is `"'

          +

            clang-3.4: error: unknown argument: '-mlittle-endian'

          +

            clang-3.4: error: unknown argument:
            '-fno-delete-null-pointer-checks'

          +

            clang-3.4: error: unknown argument:
            '-fno-inline-functions-called-once'

          +

            clang-3.4: error: unknown argument: '-fconserve-stack'

          +

            Several things have broken since the merge window.

          +

            cc-option seems to be broken

          +

            Several compiler options seem to be misordered

          +

            There was an issue with --mcpu not being set.

          +

            Mark can build vexpress with 3.4:

              #

                LLVM version 3.4svn commit
                84569698f01bcb49afe5b6140bf0d61cf4f3cf5a

              #

                clang version 3.4 commit
                472e66e9d32e587a028bc676aa63bd7137f3d4d4

      o

        X86 breakage with clang/llvm on master

          +

            also cc-options bail out with clang TIP

          +

            boot broken on clang TIP

          +

            vxlan.c  compiler ICE  -
             http://llvm.org/bugs/show_bug.cgi?id=17210

      o

        Conference followup

          +

            LLVMLinux talk at LinuxCon

              #

                Lots of input from Peter Anvin

              #

                One of the things he talked about is whether clang can
                size-optimize kernel code better than gcc

          +

            LLVM microconference

              #

                Jan-Simon: status of X86_64 kernel compiled with clang

              #

                Bryce: Enabling IA in the kernel build

              #

                Mark: VLAIS

              #

                Bero: Android

              #

                Anshu & Pavell: Enabling Linux kernel and userspace with
                clang on hexagon

              #

                Sylvestre: Debian

              #

                Eduard: Clang Static Analyzer

          +

            Several kernel devs were in attendance, including Linus Torvalds

              #

                Many questions were asked and discussed

          +

            Overall both conferences were a great success

      o

        LLVM update

          +

            LLVM is broken again for ARM. Vinicius to investigate

          +

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

          +

            Mark, Behan, Jan-Simon and Bryce discussed getting
            __builtin_stack_pointer() added to both clang and gcc in
            order to fix the named register problem as far as the stack
            pointer is concerned.

              #

                Mark has already prototyped it for clang

      o

        Kernel Patch triage (highest priority now)

          +

            Kernel 3.12 merge window is now closed

          +

            USB VLAIS patch now upstream?

          +

            Netfilter VLAIS patch to be tried next

          +

            Named registers for ARM and x86

              #

                __builtin_stack_pointer should make those patches easier

          +

            A lot of suggestions from the conferences mean that almost
            all patches need rewriting or at least further review

          +

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

          +

            wait/wound mutexes use __builtin_constant_p issue has been
            largely resolved

          +

            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

  *

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

      o

        Behan

          +

            Work on fixing vexpress

          +

            Update patches with advice from conferences

          +

            Upstream kernel patches (named registers, VLAIS)

          +

            Follow up with people from conference

          +

            Talk to chandler about __builtin_stack_pointer

          +

            Prepare for courses

          +

            Update website

      o

        Jan-Simon

          +

            Bring x86_64 back working for HEAD

          +

            XMM issue during low-level bootup

          +

            Checkpoint

      o

        Vinicius Tinti

          +

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

              #

                We need to gather Eduards findings

          +

            Add documentation to wiki

          +

            Add gentoo

      o

        Mark

          +

            Investigate issues with LLVM/clang HEAD and vexpress

          +

            Unit test for -MT and -dependency-file

          +

            Update patches?

          +

            AARCH64


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

*

-- 
Behan Webster
behanw at converseincode.com

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