The Linaro Toolchain Working Group is pleased to announce the 2011.10
release of both Linaro GCC 4.6 and Linaro GCC 4.5.
Linaro GCC 4.6 2011.10 is the eighth release in the 4.6 series. Based
off the latest GCC 4.6.1+svn179483, it contains a range of vectoriser
performance improvements and general bug fixes.
Interesting changes include:
* Updates to 4.6.1+svn179483
* Vectorises more straight-line code with data dependencies
* Now picks the best vector width when vectorising straight line code
* Better handles handling auto increment addresses in SMS
* Changes the default vector width from double word to quad word
* Better handling extracting the top or bottom half of a quad word vector
* Now supports the NEON absolute difference instruction
Fixes:
* LP: #689887 ICE in get_arm_condition_code
* LP: #809761 oss4 version 4.2-build2004-1ubuntu1 failed to build on armel
Linaro GCC 4.5 2011.10 is the fifteenth release in the 4.5
series. Based off the latest GCC 4.5.3+svn179438, this is a
maintenance focused release.
Interesting changes in 4.5 include:
* Updates to 4.5.3+svn179438
Fixes:
* LP: #689887 ICE in get_arm_condition_code
The source tarballs are available from:
https://launchpad.net/gcc-linaro/+milestone/4.6-2011.10https://launchpad.net/gcc-linaro/+milestone/4.5-2011.10
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 page:
https://launchpad.net/gcc-linaro/4.6/4.6-2011.10https://launchpad.net/gcc-linaro/4.5/4.5-2011.10
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
-- Michael
The Linaro Toolchain Working Group is pleased to announce the release
of Linaro GDB 7.3.
Linaro GDB 7.3 2011.10 is the third release in the 7.3 series. Based
off the latest GDB 7.3, it includes a number of ARM-focused bug fixes
and enhancements.
This release contains:
* Support for disabling address space randomization in gdbserver
* Fix for GDB crashes on 3.x kernels
* Fix spurious "CRC mismatch" warnings when using "remote:" sysroot
The source tarball is available at:
https://launchpad.net/gdb-linaro/+milestone/7.3-2011.10
More information on Linaro GDB is available at:
https://launchpad.net/gdb-linaro
Hi,
* Finished a presentation for NEON forum. Revital and Richard kindly
agreed to take a look and gave me some valuable comments. Thanks!
* widen-shifts:
- While preparing the presentation I found some room for improvement
in the pattern detection, so I implemented it. It gave additional 13%
to rgb24tobgr16.
- Ramana suggested a solution on how to check the constant operand of vshll.
Testing these two things on ARM.
* SLP improvements:
- Implemented a patch that swaps operands if necessary to make the
operations isomorphic, and supports loads with different offsets.
Testing it now.
- The three relevant libav loops now get vectorized giving 42%-57% speedup.
Next week holidays: half days Sunday-Wednesday and Thursday.
Ira
Here's my summary from Monday's meeting on the harder parts of binary
toolchains.
Using a 4.6 compiler against a 4.5 based sysroot such as Natty:
* libgcc and libstdc++ are part of the compiler
* The compiler expects features that are in the corresponding runtime
* You can't reliably run or validate against an earlier runtime
The solution is to upgrade the runtime on the sysroot to 4.6. 4.6 is
backwards compatible. Ubuntu did this with Maverick and it caused no
problems, although problems such as Debian #622783 have been seen.
Multiarch:
* The Ubuntu multiarch patch should work with a sysroot
* Multiarch and multilib should work together
Multilib:
* The current ARM multilib rules are old and not very relevant
* Multilib means you need multiple sysroots as well
* Skip multilib for the first release
Other:
* Anything we support in cross we should support native first
* Check that we don't have to directly supply the source that goes
with the binary sysroot
-- Michael
==Progress===
* Out of office for a day.
* Wrote a quick patch to do vcvt.f32.s32 with fractional bits where we
can. Tested no regressions, need to commit this after review upstream.
* Desk move and packing for that.
* Looked at a bug report LP 836588 appears to go away with fno-gcse.
Needs more digging.
=== Plans ===
* Look at LP 836588.
* Finish auto-inc-dec pipeline scheduling work.
* Clear out some of the old patches (POST_MODIFY_DISP for vfp, BRANCH_COST )
* Settle into new desk.
* Again a short week as I'm away for 2 days for an internal training event.
Meetings:
* 1-1s
* TCWG calls
Absences.
* 5th October - out of office.
* 13th - 14th October - Out of Office - Internal training event.
* 31st Oct - 4th Nov - Linaro Summit Orlando - Travel booked -
* 08 Nov - 11 Nov - Tentatively booked
* Dec 19 - 31st Dec - Tentatively booked
== Last week ==
* Patch review.
* Backported second attempt to fix get_arm_condition_code ICE.
* Worked on -fsched-pressure. Experimented with various combinations
of ideas. This is giving some good results (e.g. a 2x improvement
in libav's put_h264_qpel8_hv_lowpass_8) but needs a bit more work
to fix some outliers.
I'll be away from 18th Oct to 14th Nov.
Richard
Random data for the day: Dave Pigott has installed some new PandaBoard
build machines in the validation lab. They're identical to mine
except that root is on USB Flash instead of NFS, and they have a much
faster flash drive for the build area.
The time taken to bootstrap and test gcc-linaro-2011.09 with C, C++,
Fortran, and LTO is:
* ursa3, ursa4 (Toshiba USB stick): 301 minutes build / 369 test
* ursa2 (no-name USB stick): 324 minutes build / 422 test
* tcpanda (fast USB stick): 274 minutes build / 265 test
So the new combo gives a 1.38 x faster build. I'm surprised as I
though the build was CPU bound. I'd hate to see what building on an
SD card is like.
Note that /tmp is in RAM, /scratch is ext4, the new boards use
noatime, and the kernel doesn't have the new USB performance fix.
-- Michael
Continue working on estimating register pressure with SMS:
- Discussed current approach with Richard which gave useful leads.
- Started to implement this approach.
- Doing experiments on libav microbench.
The unaligned accesses in libpng are, for the large copies, a bug. Our attempt to align the row buffer to a 16 byte boundary was off-by-one so we end up always mis-aligning it. I've posted a patch on the png-mng-implement list:
http://sourceforge.net/mailarchive/message.php?msg_id=28194444
The time spent in memcpy() is probably an illusion. The data out of zlib gets copied to one row buffer where it is unfiltered (if necessary) then a copy is made in a separate buffer that is only used for the filter handling. If you test using images with large rows (I don't know what pngbench does) the copy buffer may well get flushed out of the second level cache between each row, then the memcpy will stall bringing it back in.
If you have machine level profiling you may see this as a massive time spike on some probably unrelated instruction which just happens to be in the PC when the stall stops everything.
Anyway, I have several ideas of how to avoid the copy when it isn't required.
John Bowler <jbowler(a)acm.org>
-----Original Message-----
From: Glenn Randers-Pehrson [mailto:glennrp@gmail.com]
Sent: Monday, October 03, 2011 1:15 PM
To: PNG/MNG implementation discussion list
Subject: [png-mng-implement] Use of memcpy() in libpng [Fwd from linaro-toolchain list]
Re: Use of memcpy() in libpng
David Gilbert
Tue, 27 Sep 2011 06:20:14 -0700
On 27 September 2011 14:16, Christian Robottom Reis <k...(a)linaro.org> wrote:
> On Tue, Sep 27, 2011 at 09:47:33AM +0100, Ramana Radhakrishnan wrote:
>> On 26 September 2011 21:51, Michael Hope <michael.h...(a)linaro.org> wrote:
>> > Saw this on the linaro-multimedia list:
>> >
>> > http://lists.linaro.org/pipermail/linaro-multimedia/2011-September/
>> > 000074.html
>> >
>> > libpng spends a significant amount of time in memcpy(). This might
>> > tie in with Ramana's investigation or the unaligned access work by
>> > allowing more memcpy()s to be inlined.
>>
>> It's the unaligned access and the change / improvements to the memcpy
>> that *might* help in this case. But that ofcourse depends on the
>> compiler knowing when it can do such a thing. Ofcourse what might be
>> more interesting is the kind of workload analysis that Dave's done in
>> the past with memcpy to know what the alignment and size of the
>> buffer being copied is.
>
> If you guys could take a look at this there is a potential requirement
> for the MMWG around libpng optimization; we could fit this in along
> with other work (possible vectorizing, etc) on that component.
It wouldn't take long to analyse the memcpy calls - life would be easier if we had the test program and some details on things like what size of images were used in these benchmarks.
Dave
