== Blueprints ==
Initial Current Actual
initial-aarch64-backport 31 Oct 2012 30 Nov 2012
aarch64-baremetal-testing 31 Oct 2012 30 Nov 2012
fix-gcc-multiarch-testing 31 Dec 2012 31 Dec 2012
backport-fma-intrinsic 31 Dec 2012 31 Dec 2012
fused-multiply-add-support 31 Dec 2012 31 Dec 2012
gcc-investigate-lra-for-arm 31 Dec 2012 31 Dec 2012
== Progress ==
* Admin
* Interviewing
* Hand over prep with Michael
* Release Week
* Made 2012.11 releases of gcc-linaro 4.6 and 4.7.
* LEG interations:
* Investigated CILK+ and how much work to port to AArch64.
* HOT/COLD partitioning
* Ran benchmarks on ARM
* LRA
* Ran x86-64 benchmarks
== Next Week ==
* Investigate patches for literal pool layout bug
* Post triplet backport patches upstream
* Run HOT/COLD partitioning benchmarks
* Analyse ARM results
* On x86_64 to see what the actual benefit we could get
* initial-aarch64-backport & aarch64-baremetal-testing
* Finish documentation
* gcc-investigate-lra-for-arm
* Analyse benchmarks
* fix-gcc-multiarch-testing
* Come up with strawman proposal for updating testsuite to handle
testing with varying command-line options.
== Future ==
* backport-fma-intrinsic & fused-multiply-add-support
* Backport patches once fix-gcc-multiarch-testing has been done.
--
Matthew Gretton-Dann
Linaro Toolchain Working Group
matthew.gretton-dann(a)linaro.org
== Progress ==
* Infrastructure:
- Managed to have my laptop re-installed by IT with a native Ubuntu 12.04,
(as a beta tester).
- Re-setup my working environment.
* GCC release process familiarization.
* Boehm GC AArch64 support:
- Resume libatomic-ops work.
* Some internal support
== Next ==
* Continue on the Boehm GC AArch64 support.
== Progress ==
* Started working on "Turn off 64 bits Bitops in Neon in GCC" blueprint.
* branch review for aarch64-4.7 merge.
A lot of time wasted due network instability making it difficult to
checkout a GCC branch from launchpad/bzr.
* Internal support for infrastructure problems.
* Resumed discussions with our internal IT and Christian Bejram to try to
decrease our constraints.
The Linaro Toolchain Working Group is pleased to announce the 2012.11
release of both Linaro GCC 4.7 and Linaro GCC 4.6.
Linaro GCC 4.7 2012.11 is the eigth release in the 4.7 series. Based
off the latest GCC 4.7.2+svn193200 release, it includes ARM-focused
performance improvements and bug fixes.
Interesting changes include:
* Updates to GCC 4.7.2+svn193200
* Also includes arm/aarch64-4.7-branch up to svn revision 193328.
Fixes:
* LP #1065122
* LP #1065559
* LP #1067760
Linaro GCC 4.6 2012.11 is the 21st release in the 4.6 series. Based
off the latest GCC 4.6.3+svn193199 release, this is the eigth release
after entering maintenance.
Interesting changes include:
* Updates to 4.6.3+svn193199
The source tarballs are available from:
https://launchpad.net/gcc-linaro/+milestone/4.7-2012.11https://launchpad.net/gcc-linaro/+milestone/4.6-2012.11
Downloads are available from the Linaro GCC page on Launchpad:
https://launchpad.net/gcc-linaro
More information on the features and issues are available from the
release pages:
https://launchpad.net/gcc-linaro/4.7/4.7-2012.11https://launchpad.net/gcc-linaro/4.6/4.6-2012.11
Mailing list: http://lists.linaro.org/mailman/listinfo/linaro-toolchain
Bugs: https://bugs.launchpad.net/gcc-linaro/
Questions? https://ask.linaro.org/
Interested in commercial support? Inquire at support(a)linaro.org
--
Matthew Gretton-Dann
Linaro Toolchain Working Group
matthew.gretton-dann(a)linaro.org
Hi,
I've encountered a case where gcc produces a broken program: a branch that should never be taken is taken, and wrong values are written to memory (and printed out).
The code is fairly ordinary and small. It can be seen here: http://pastebin.com/0Hspz8mw
This happens when -funroll-loops flag is used in conjunction with -O2 or -O3. It doesn't seem to happen when it is used with -O1.
Another few things that influences the program flow from from incorrect to correct run (gives expected outpus) are:
- Adding/removing printf's inside the inner loop
- Changing the order of the expressions in the "if" clause. i.e. from this:
if ((y < mu) || (y >= H - md) ||
(x < ml) || (x >= W - mr))
to this:
if ((x < ml) || (y >= H - md) ||
(y < mu) || (x >= W - mr))
- Assigning ml inside f() to the same value (3) it's getting from the function arguments.
All of these shouldn't change how the program behaves but it does.
I compiled this with two different compilers/environments:
1. g++ (Ubuntu/Linaro 4.6.3-1ubuntu5) 4.6.3, running on 3.2.1-42-linaro-lt-mx6 (native compilation on the ARM board)
Compilation command:
g++ -march=armv7-a -mfpu=neon -mfloat-abi=hard -mtune=cortex-a9 -O3 -std=c++0x -funroll-loops -o test_bug_sa_loops_linaro test_bug.cxx
2. arm-fsl-linux-gnueabi-g++ (Freescale MAD -- Linaro 2011.07 -- Built at 2011/08/10 09:20) 4.6.2 20110630 (prerelease)
Running on a freescale LTIB built linux (3.0.15-1359-g1b64ead)
Compilation command:
arm-fsl-linux-gnueabi-g++ -march=armv7-a -mfpu=neon -mfloat-abi=hard -mtune=cortex-a9 -O3 -std=c++0x -funroll-loops -o test_bug_sa_loops test_bug.cxx
In all the variations I tried it seems that -funroll-loops is critical for this problem to appear.
I'd be glad to hear some comments on this.
Mickey.
This mail was sent via Mail-SeCure system.
On 10 November 2012 05:11, "Frank Müller" <franky1976(a)gmx.net> wrote:
> Michael Hope <michael.hope(a)linaro.org>:
>> My suspicion is that we/crosstool-NG enable extra features like
>> Graphite or GCC is built with a different level of checking. If you
>
> I suspected Graphite as well and removed it in my own builds without noticable difference.
>
>> have the time, could you check the flags passed to GCCs configure?
>> You can do this on Ubuntu using:
>>
>> apt-get build-dep gcc
>> apt-get source gcc
>> dpkg-buildpackage -uc -us -b
>>
>> and compare the configure line with the one in crosstool-NG's build.log.
>
> Isn't this the same as gcc -v? I've posted the lines at http://lists.linaro.org/pipermail/linaro-toolchain/2012-October/002913.html
Good point. There's nothing obvious in the list. Ubuntu explicitly
adds --enable-checking=release but it's the default for release
branches like ours.
I can reproduce the slowdown in a smaller testcase. Compiling pcre
with -O3 -mfpu=neon -march=armv7-a -mtune=cortex-a8 takes 18.8 s for
the Ubuntu Precise 4.6 compiler, 17.8 s for the Ubuntu Quantal 4.7
compiler, and 41.2 s for the Linaro 4.7 2012.10 build. I've logged
LP: #1077739 to track. I'll spin a --enable-checking=release build
just to check.
> The above lines do not work for me, the last line misses a changelog file:
>
> # dpkg-buildpackage -uc -us -b
> tail: cannot open `debian/changelog' for reading: No such file or directory
> dpkg-buildpackage: error: tail of debian/changelog gave error exit status 1
Yip, you need to change to the just-extracted source directory first.
-- Michael