- linaro-toolchain - lists.linaro.org

by Yao Qi

== Linaro GCC == * Merge ldm/stm patch to Linaro 4.5 tree. Found two regressions on the last minute of proposing merge request in pass ce3. Revert one of ldm/stm patches about ifcvt. Complete testcase in branch. * Try Richard E.'s "TST to LSLS transformation" patch on cortex-a9 with FFMPEG. No speed improvements. * Various Linaro GCC Bug fixing. ** LP:634738 Follow the fix to GCC PR40697, and create a new patch, which emits extzv or shift rather than loading constants in some cases. Tested on FSF GCC trunk, and no regression. However, found a regression by eyes in pr44999.c, in which, ubfx (4byte) is generated, rather than uxth (2byte). uxth is produced by combiner from ashift and lshiftrt. During reading arm.c, find that constant handling in thumb2 should be improved to some extent. ** LP:633243 Re-implement regrename improvement, as Eric B. suggested in gcc-patches. Spend some time on understanding API in GCC related to hard-reg. Tested on x86_64-linux. No regression. ** LP:638935 Update my tree to FSF trunk, and find RTL seq for fldm/fstm peephole disappears due to fix to PR45722. Extend arm-ldmstm.ml to support vfp. Peephole and RTL patterns for vfp are done. Will revise arm.c:{load,store}_multiple_sequence to accept vfp data. Fix a bug in ldm/stm peephole when starting offset is negative. == This week == * LP:634738: Figure out how uxth is produced by combiner. * LP:633243: Test it on ARM. * LP:638935: Revise {load,store}_multiple_sequence to accept vfp data. -- Yao (齐尧)

15 years, 5 months

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GCC SVN vs. BZR/LP

by Andrew Stubbs

Re my recent email "Upstream GCC feature freeze", I think we're agreed that we need to create a branch that tracks GCC 4.6 development, but has our own performance improvements included. The question is where to host it? Option 1: Launchpad/bzr Pros: * We need no permission to do it * The branch will naturally evolve into our 4.6 release series in time. * The 3-way merge works well (if slowly) * We can include patches that we have no intention of posting upstream ever * Our patch tracker will Just Work. * Merge requests will be available. Cons: * Bzr ;) * It's hidden away from the view of most GCC developers Option 2: GCC SVN branch Pros: * We can work in the open, submitting patches via gcc-patches, as usual * The final merge to GCC trunk (come stage 1) will be eased, a little Cons: * We can't really apply anything we want just for ourselves * we may end up maintaining an LP branch shadowing the svn branch * When we do want to do 4.6 in LP, we'll have to backport all our patches from 4.7, and this may no longer be straightforward. * Write permissions not clear. * Although I think you can just go ahead and do it? OK, so I'm sure I've missed some big ones. Please discuss! ;) I think the big question here is, when will we start wanting to make (unstable/experimental) Linaro GCC 4.6 releases? If we want to do it early, then we'll have no choice but to have an LP branch to release from. Andrew

15 years, 5 months

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[ACTIVITY] week 46

by Marcin Juszkiewicz

Like everyone from Toolchain WG I will share my activites in last week: 1. cross compilers for archive - discussed with doko about dropping update-alternatives use - wrote gcc-defaults-armel-cross 1.4 which does proper symlinks for cross compilers - wrote gcc-4.5-armel-cross 1.41 which removes update-alternatives support - wrote gcc-4.4-armel-cross 1.37 which removes update-alternatives support - wrote armel-cross-toolchain-base 1.53 which has all updates which I had - sent all of them to Steve for review Status of changes: - default version of armel cross compiler will be 4.5 like it is in Natty - both 4.4 and 4.5 will be provided as it is for native - any traces of update-alternatives use should be removed Needs to be done: - adding conflicts on older cross compilers to gcc-defaults-armel-cross Order of upload to archive: - armel-cross-toolchain-base - gcc-4.5-armel-cross - gcc-4.4-armel-cross - gcc-defaults-armel-cross 2. Checked few old bugs do they still apply: - Bugs #646729, #637454, #671455 are done with armel-cross-toolchain-base 1.52 (landed in maverick-proposed) Regards, -- JID: hrw(a)jabber.org Website: http://marcin.juszkiewicz.com.pl/ LinkedIn: http://www.linkedin.com/in/marcinjuszkiewicz

15 years, 5 months

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[ACTIVITY] 2010-11-19

by David Gilbert

Short week. Finally got external hard drive for my beagle - makes it sanely possible to natively build things. Got eglibc cross built (Thanks to Wookey for pointing me in the right direction with the magic incantation of dpkg-buildpackage -aarmel --target=binary) and easily rebuilding . I have a version with the neon version of my memset built into it - it doesn't seem to make a noticeable difference to my ghostscript benchmark though. Panda's aren't likely to turn up until mid December; arranging borrowing an A9 is turning out to be difficult, but it looks like we should be able to get access to the one in the London datacentre - although it has a disc problem at the moment. I did manage to get a colleague to try my tests on his own Toshiba AC-10 (Tegra-2 - no Neon); the graphs had approximately the same shape as my previous Panda tests. Memchr looked pretty good on there. Also trying to look at the sign off I need for various libc access. Dave

15 years, 5 months

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[ACTIVITY] weekly status

by Ken Werner

I mainly worked on the atomic memory operations blueprint/item: * posted an updated patch for #643171 on the libc-ports ml after running the glibc testsuite natively on the vexpress * continued to learn about the ARM instructions involved :) * started to write some gcc testcases that scan the asm output of the __sync builtins (mainly to detect differences between the gcc versions - not sure how useful those tests would be for upstream as the sequences may easily change) Ken

15 years, 5 months

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[ACTIVITY] report week 46

by Peter Maydell

RAG: Red: Amber: Green: Milestones: | Planned | Estimate | Actual | finish virtio-system | 2010-08-27 | postponed | | get valgrind into linaro PPA | 2010-09-15 | 2010-09-28 | 2010-09-28 | complete a qemu-maemo update | 2010-09-24 | 2010-09-22 | 2010-09-22 | finish testing PCI patches | 2010-10-01 | 2010-10-22 | 2010-10-18 | Progress: * Most of this week spent at the Meego conference in Dublin. This seemed to be a rather apps-developer centric conf, with not much of interest on the low-level side. There were a few useful talks/conversations, though. * Intel were giving away Atom-based netbooks to all attendees; that's a lot of developers who are going to be testing and optimising their apps for Atom devices rather than ARM... * qemu: looked at https://bugs.launchpad.net/bugs/668799 ; we don't seem to be taking the right lock before we manipulate the graph of translation blocks. I have a fix which stops the reported segfault, but the code has a number of "XXX not thread safe" and "FIXME: not SMP safe" comments and generally doesn't seem to have a coherent locking design :-( * qemu: sent some minor patches upstream: + enable iwmmxt coprocessors in user mode + remove some unused functions from target-arm and target-sparc + fix a failure to build bug in a makefile * qemu: some review of a patch to fix semihosting SYS_GET_CMDLINE Plans - qemu consolidation - post-toolchain-review, sort out some milestones for this report Absences: (complete to end of 2010) Thu/Fri 25-26 Nov; Fri 17 Dec - Tue 4 Jan inclusive. (Dallas Linaro sprint 9-15 Jan.)

15 years, 5 months

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[ACTIVITY] Weekly status

by Richard Sandiford

== This week == Started looking at STT_GNU_IFUNC support in BFD. There were a couple of janitorial changes I needed to make in order to prepare elf32-arm.c for the main patch. I tested those separately and submitted them upstream: http://sourceware.org/ml/binutils/2010-11/msg00330.html http://sourceware.org/ml/binutils/2010-11/msg00331.html I've now finished a prototype implementation of the STT_GNU_IFUNC support itself. It wasn't as mechanical as I'd originally assumed, which was nice. Tests that I've run by hand seem to be doing the right thing. I've now started writing tests for the testsuite (meaning: I've completed 1 test so far). == Next week == * Add more tests, including Thumb coverage. * Start on the libc changes. Richard

15 years, 5 months

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gcc seg fault on kernel build

by Rob Herring

Doing an allmodconfig build on the kernel, I get the following: CC arch/arm/kernel/asm-offsets.s In file included from /home/rob/proj/git/linux-2.6-dt/include/linux/kernel.h:12, from /home/rob/proj/git/linux-2.6-dt/include/linux/sched.h:54, from /home/rob/proj/git/linux-2.6-dt/arch/arm/kernel/asm-offsets.c:13: /usr/lib/gcc/arm-linux-gnueabi/4.4.5/include/stdarg.h:40: internal compiler error: Segmentation fault It occurs on Maverick 4.4, 4.5 and CodeSourcery 2009Q1 cross toolchains. It's confirmed by Codesourcery here: http://www.codesourcery.com/archives/arm-gnu/msg03719.html What's the status on this issue? I didn't see anything in Linaro gcc bugs that looks related. Rob

15 years, 5 months

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[ACTIVITY] November 14-18

by Ira Rosen

Hi, This week I continued looking into vld/vst support in GCC. I also fixed GCC PR 46312 - testsuite failures on ARM. Ira

15 years, 5 months

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STT_GNU_IFUNC and R_ARM_IRELATIVE

by Richard Sandiford

The STT_GNU_IFUNC blueprint: https://wiki.linaro.org/WorkingGroups/ToolChain/Specs/Binutils-STT_GNU_IFUNC says "the ARM EABI will be updated to support STT_GNU_IFUNC's requirements". I suppose the most obvious thing that needs to be defined is the relocation number for R_ARM_IRELATIVE. What's the best way of handling that? The main options seem to be: 1. Reserve a relocation number with ARM first (129?). 2. Go ahead and implement it without having the EABI updated. See whether the results are good before deciding whether to bless it in the EABI. 3. Since STT_GNU_IFUNC is a GNU-specific, treat R_ARM_IRELATIVE as GNU-specific too, and pinch one of the R_ARM_PRIVATE relocs. I'm pretty sure (3)'s not the way to go, but I was aiming for completeness. :-) Richard

15 years, 5 months

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Fwd: Fw: GCC SVN vs. BZR/LP

by Ira Rosen

Hi, On 17 November 2010 05:35, Michael Hope <michael.hope(a)linaro.org> wrote: > 1. How easy is it to frequently merge in SVN? It used to be terrible > as you had to manually track the merges. These days can you do a 'svn > merge trunk' and have it just work? I asked Mike Meissner to answer this question. Mike is very experienced in GCC and GCC SVN branch management. I am attaching his reply. Ira I sent this recently to ppc64-toolchain(a)linux.ibm.com on how to use svnmerge to manage branches: This script (also ~meissner/meissner/bin.sh/svnmerge) is what I use to update svn directories, such as ibm-gcc-4_5-branch. I think I originally got it from Ben E. and it may be in the contrib directory. Typically the way I start a branch, such as my normal power7-meissner branch, I do the following: $ export TRUNK="svn+ssh://@gcc.gnu.org/svn/gcc/trunk" $ export BNAME="power7-meissner" $ export BRANCH="svn+ssh://@gcc.gnu.org/svn/gcc/branches/ibm/$BNAME" $ export SRC="$HOME/fsf-src" $ svn delete -m"delete old branch" $BRANCH $ svn copy -m"Clone new branch" $TRUNK $BRANCH $ cd $SRC $ svn co $BRANCH $ cd $BNAME $ svnmerge init $ svn update # this is sometimes needed $ svn commit -m'Create svnmerge init info' $ export REV="xxxx" # substitute subversion id for xxxxx $ echo "power7-meissner branch, based on $REV." > gcc/REVISION $ touch gcc/ChangeLog.power7 $ <edit gcc/ChangeLog.power to create initial contents> $ svn add gcc/ChangeLog.power gcc/REVISION $ svn commit -m'Add REVISION to branch' In particular, creating GCC/REVISION allows you to tell what subversion revision the source is based against. You can find the information via: $ svn propget svnmerge-integrated but it is a lot easier if you have a compiler tree to do gcc -v. After you do a propget, you will need to do a svn update. In this case, I use gcc/ChangeLog.power7 to hold the ChangeLog entries local to the branch. That way I can see a summary of the changes, but not pollute the normal ChangeLog files. To do merges, you need to make sure that all local changes are checked into the branch. Then do: $ cd $SRC/$BNAME $ svnmerge merge $ <edit gcc/REVISION and ChangeLog.power7 to indicate merge> $ <test merged files, if satisified, check them in> $ export REV="xxxx" # substitute subversion id for xxxxx $ svn update # just in case $ svn commit -m"Update to subversion id $REV" Now, to create a patch file do, make sure the files are checked in: $ cd $SRC/$BNAME $ export PATCHFILE="$HOME/patches/mypatch.patch01" $ <make ChangeLog entries in $PATCHFILE> $ svn diff --old $TRUNK --new . -r $REV >> $PATCHFILE $ <delete ChangeLog.power7, REVISION, property changes from $PATCHFILE> $ submit patch To see if there are changes to be merge in: $ svnmerge avail For example on the ibm-gcc-4_5-branch, the following changes are available to be merged in: 164657-166510 when I originally wrote this message on the 9th of November, and Peter has subsequently updated the merge. I put the folliwng in ~/.subversion/config to provide my own diff command: ### Set diff-cmd to the absolute path of your 'diff' program. ### This will override the compile-time default, which is to use ### Subversion's internal diff implementation. diff-cmd = /home/meissner/bin.sh/svndiff Every so often, I find svnmerge misses, for example in deleting directories. It is helpful to do a diff from the mainline every so often to make sure you are not missing newly created files or still are keeping older files or just missed a change. I'll include svndiff for the smarter svndiff command and mrm-changelog.el that looks for the ChangeLog.<name> files I use in different branches. Feel free to contact me to clarify some stuff. -- Michael Meissner, IBM 5 Technology Place Drive, M/S 2757, Westford, MA 01886-3141, USA meissner(a)linux.vnet.ibm.com fax +1 (978) 399-6899 (See attached file: svnmerge)(See attached file: svndiff)(See attached file: mrm-changelog.el)

15 years, 5 months

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Public plan review recording

by Michael Hope

Hi there, There's a recording of this mornings public plan review available on the wiki at: https://wiki.linaro.org/Releases/1105/PublicPlanReview Also included is a copy of the slides and supporting documents. Might be interesting for those who missed it. -- Michael

15 years, 5 months

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Thumb-2 performance discussion

by Michael Hope

A heads up. I'd like to have a brainstorming session on potential Thumb-2 performance improvements in GCC. Think about what you'd like in such a session, and what preperation should be done, and we can discuss the discussion (heh) on Monday. -- Michael

15 years, 5 months

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Abstract submissions for QEMU Users Forum (March 18th)

by Christian Robottom Reis

Hi there, I noticed that there's a QEMU users forum at: http://adt.cs.upb.de/quf/ and that the abstract submission phase is still open, and closes November 28th. It would be great to see some participation there and help identify other key people interested in using and improving QEMU. -- Christian Robottom Reis | [+55] 16 9112 6430 | http://launchpad.net/~kiko Linaro Engineering VP | [ +1] 612 216 4935 | http://async.com.br/~kiko

15 years, 5 months

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[ACTIVITY] Digest for 2010-11-16

by Michael Hope

Zach Welch -- == Last Week == * Continued working on libunwind support. Trying to figure out why my signal frame detection doesn't work as expected. * Kept pace with the ltrace tree, testing recent patches on ARM. == This Week == * Continue to work on libunwind signal frame detection. Julian Brown -- == Linaro GCC == * Looked at issues #663198 (double-precision register expected) -- which was already fixed on the linaro branch, but the bug was reported against a version just prior to that, and #667490 -- which involved a possible problem with the NEON "load 0.0" patch. Experimented for a while with the latter, but could not find anything wrong. Followed up upstream, and requested a stand-alone test case. * Worked on a proper solution to the VMOVN-in-big-endian-mode problem, discovering that several other quadword-register operations were similarly broken in the process. WIP patch sent to linaro-toolchain for discussion, but it needs a little more work before it can be applied. Peter Maydell -- Progress: * qemu: more cleanup of signal handler VFP patchset; I think I just need to add iwmmx support and it's good * qemu: VCVT: found yet another bug, did final patchset cleanup: submitted to upstream list [8 patch series] * qemu: submitted a trivial patch to fix a problem where __get_user/_put_user macros had an unnecessary local var which could clash with a var being used by the macro user * set up a tree on git.linaro.org which we can use for a branch to make pull requests for ARM qemu fixes * did a rough estimate of time to do an Eagle qemu model (6 months + testing/bug fixing time) Issues: * lost some time to a problem where Linux VMs stopped being able to talk to the LDAP server; however I have a workaround and IT are investigating Meetings: * toolchain, toolchain standup, pdsw-tools, PD doughnuts Plans - attend Meego conference in Dublin (Nov 15-18 inc travel) http://conference2010.meego.com/ - start on qemu consolidation by upstreaming various ARMv7 correctness fixes Andrew Stubbs -- == GCC 4.5 == * Continued working on LP:663939. * I still have not worked out how best to fix the constant propagation problem that has been thwarting my optimization patch, however I think I understand it better now. * I have started on adding replicated pattern support to the constant splitting. Initial results were good, but I discovered that I had to rearrange the code somewhat to get the cost estimation and negative/inverted constant support working correctly. So far, I have it successfully using 16-bit replication pattern constants for set/add/subtract operations. Other operations appear broken at the moment, but it's almost certainly just a few tweaks required. * TODO: Add support for 32-bit replicated pattern constants. Adjust some of the other two-instruction constant generation techniques to let them fall through to this new code, where it would be beneficial. * Pushed the latest set of GCC patches into Linaro GCC 4.5. Chung-Lin Tang -- == Linaro GCC == * Linaro #672833, one batch of my backports of Bernd's postreload patches exposed some varargs regressions for x86-64, was reverted by Michael. Tested the compiler and found it was fixed on mainline rev.162384. Backporting this revision plus the postreload patches fixed the regressions; x86-64 bootstrap also verified okay. There is however another PR45027 fix that was needed on trunk, but needs a bit more clarification if needed on a 4.5 compiler. * Linaro #641397, CS issue #6753: bitfield optimization. Patch tested without regressions, posted for CS internal review, should soon push for Linaro merge. * Started looking further at some GCC DF, IRA internals. == This week == * Look at more Linaro issues. * Maybe start looking at some GCC bugzilla PRs. * There is a local ARM technical event in Hsinchu on Thursday, might go and look around. Yao Qi -- == Linaro GCC == * Mainline patch backport to Linaro 4.5. ** Patch "Fix an if statement in arm_rtx_costs_1". Verified on Linaro 4.5. 0.1% smaller on size, and 0.2% faster on speed. Merged to Linaro 4.5 by Andrew S. ** Try Nathan F's ifcvt-cond-move patch on cortex-a8 with -O2/O3. No improvements on speed/size for EEMBC. ** Bernd's ldm/stm patch. Analyze the reason of regression on Linaro 4.5. Found something wrong in IRA rtl dump, and spend sometime on understanding IRA rtl dump log. Thanks to Chung-Lin, I realize that IRA dump is correct, and look back to ARM RTL patterns on ldm/stm. Compared RTL patterns in 4.5 and 4.6, found some difference. Regenerate ldmstm.md for Linaro 4.5 after update arm-ldmstm.ml a little bit. Regressions goes away! No speed improvement, but code is smaller by 0.2% in EEMBC. Still prefer to merge to Linaro 4.5. ocaml is an interesting language, but not easy to learn and read in vim. * Some discussion on Linaro development process. * My regrename improvement patch (re. LP:633243). Communicate with Eric Botcazou back and forth, but current patch is still too target-dependent to him, as a Middle-End maintainer. Still need some improvements. * Build FSF GCC trunk. CLoog requirement in configure is wrong, revert configure to previous version, and then pass the version checking during gcc configure.

15 years, 5 months

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Activity reports

by Michael Hope

Hi there. Could everyone in the toolchain working group start sending their activity reports to this list please? Put [ACTIVITY] at the start of the subject line so that they can be filtered. Ta, -- Michael

15 years, 5 months

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Status reports

by Michael Hope

Hi there. Attached are the status reports from the Toolchain WG members for last week. -- Michael Ken Werner -- Hi Michael, * got access to the internal wiki/calendar/email :) * continued to setup the borrowed vexpress board * upgraded to the Linaro 10.11 release * encountered various issues until I found that the /etc/hosts is empty (#674090) * learned that the SD card issue is a known problem (#632798) * the network interface sometimes dies if stressed (Matt was able to reproduce this) * the disabled CONFIG_SWAP is being tracked as #672656 * sometimes the entire system hangs (when under heavy load?) * David noticed that /proc/cpuinfo lacks neon support (but his string benchmark/testcase ran fine) * wondering why the kernel reports only about 800 BogoMIPS while it's around 2k on the panda board * started to work on the atomic memory operations item * identified the relevant GCC patches * still looking for a good way to verify the GCC support * posted a patch on the glibc-ports ml with regard to #643171 David A Gilbert -- I managed to get to try Ken Werner's Versatile Express board with an A9MP tile; the shape of the graphs matches that from the Panda, but the raw performance is down by a factor of about 3 - I'm guessing it's clocked lower for some reason. It confirms however that the Neon behaviour I was seeing with memset is not Panda/OMAP4 specific; no one has replied to my post to linaro-toolchain. It's a difficult situation in that my fastest memset on Beagle is with Neon, and my fastest on v9 is without Neon - what would you select on? I've just finished writing memchr tests and my first crack at a faster version; I realised I could use the same trick that I had used for strlen and it works nicely - it seems to be about 50% faster than the libc version; I've not tested against any other versions yet. Paul Mckenney hasn't replied yet about the OSSC stuff, but apparently he's out travelling and back next week; so I'll catch him then. I tried preloading my faster memset into ghostscript, but found it was blatantly ignoring it - I think the memset is being called from somewhere inside libc; I managed to get xdeb to cross build me a libc but haven't yet got my changes into it. My order for a USB hard drive for my beagle seems to have been delayed by the supplier; I'm pushing this but it's starting to be a bit of a pain. Richard Sandiford -- == Last Week == * Pinged my GAS fix for Thumb PLT branches to locally-defined symbols. Committed it to binutils trunk and 2.21 branch after approval. This fixes the libgcc.so build failure that I was seeing with GOLD. * Worked on a patch to fix GOLD's handling of non-function references to weak undefined symbols. This ended up touching every backend (i386, x86_64, ARM, Power and SPARC) and was quite invasive, so it took a while in the end. Committed to binutils trunk after approval. * Ran more tests, both with -marm and -mthumb. I'm getting identical GCC test results (including gfortran and objc) for GOLD and BFD ld, so I think we're at the stage where GOLD is a viable replacement for the BFD linker. == Next Week == * I'll start looking at the IFUNC support. * I'll take another look at launchpad bug 665598. Peter Maydell -- Progress: * qemu: more cleanup of signal handler VFP patchset; I think I just need to add iwmmx support and it's good * qemu: VCVT: found yet another bug, did final patchset cleanup: submitted to upstream list [8 patch series] * qemu: submitted a trivial patch to fix a problem where __get_user/_put_user macros had an unnecessary local var which could clash with a var being used by the macro user * set up a tree on git.linaro.org which we can use for a branch to make pull requests for ARM qemu fixes * did a rough estimate of time to do an Eagle qemu model (6 months + testing/bug fixing time) Issues: * lost some time to a problem where Linux VMs stopped being able to talk to the LDAP server; however I have a workaround and IT are investigating Meetings: * toolchain, toolchain standup, pdsw-tools, PD doughnuts Plans - attend Meego conference in Dublin (Nov 15-18 inc travel) http://conference2010.meego.com/ - start on qemu consolidation by upstreaming various ARMv7 correctness fixes Ira Rosen -- Here is this week report: 1. BeagleBoard installed, now "playing" with it 2. Continued to work on auto-detection of vector size 3. Looked into mixed vector sizes 4. Learning about vld and vst instructions It looks like I won't be able to participate in Wed calls, since I am alone with the kids on Wednesday evenings.

15 years, 5 months

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Assembler bug blocking Thumb-2 kernel builds

by Dave Martin

Hi all, I've hit a probable assembler bug trying to build a Thumb-2 kernel: Trying to assemble the attached file, I get: arch/arm/kernel/relocate_kernel.S: Assembler messages: arch/arm/kernel/relocate_kernel.S:10: Error: invalid offset, value too big (0xFFFFFFFFFFFFFFFC) arch/arm/kernel/relocate_kernel.S:11: Error: invalid offset, value too big (0xFFFFFFFFFFFFFFFC) arch/arm/kernel/relocate_kernel.S:58: Error: invalid offset, value too big (0xFFFFFFFFFFFFFFFC) arch/arm/kernel/relocate_kernel.S:59: Error: invalid offset, value too big (0xFFFFFFFFFFFFFFFC) The code appears correct and resonable, except that there should be a .align directive before the data words at the end of the file (but adding this doesn't fix the error) Assembling in ARM (i.e., without -mthumb), or deleting the .globl lines associated with the affected target symbols, the problem goes away. I believe this may be already by tracked by CodeSourcery as is issue #8775 (?) Has anyone hit this issue before? Is it fixed upstream? Any help much appreciated. Cheers ---Dave

15 years, 6 months

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A9 Neon confusion

by David Gilbert

Hi, I've been looking at some basic libc routine optimisation and have a curious problem with memset and wondered if anyone can offer some insights. Some graphs and links to code are on https://wiki.linaro.org/WorkingGroups/ToolChain/Benchmarks/InitialMemset I've written a simple memset in both a with and without Neon variety and tested them on a Beagle(C4) and a Panda board and I'm finding that the Neon version is faster than the non-neon version (a bit) on the Beagle but a LOT slower on the Panda - and I'd like to understand why it's slower than the non-neon version - I'm guessing it's some form of cache interaction. The graphs on that page are all generated by timing a loop that repeatedly memsets the same area of memory; the X axis is the size of the memset. Prior to the test loop the area is read into cache (I came to the conclusion the A8 didn't write allocate?). There are two variants of the graphs - absolute in MB/s on Y, and a relative set (below the absolute) that are relative to the performance of the libc routines. (The ones below those pairs are just older versions). if you look at the top left graph on that page you can see that on the Beagle (left) my Neon routine beats my Thumb routine a bit (both beating libc). If you look on the top right you see the Panda performance with my Thumb code being the fastest and generally following libc, but the Neon code (red line) topping out at about 2.5GB/s which is substantially below the peak of the libc and ARM code. The core loop of the Neon code (see the bzr link for the full thing) is: 4: subs r4,r4,#32 vst2.8 {d0,d1,d2,d3}, [ r3:256 ]! bne 4b while the core of the non-Neon version is: 4: subs r4,r4,#16 stmia r3!,{r1,r5,r6,r7} bne 4b I've also tried vst1 and vstm in the neon loop and it still won't match the non-Neon version. All suggestions welcome, plus I'd appreciate if anyone can suggest which particular limit it's hitting - does anyone have figures for the theoretical bus and L1 and L2 write bandwidths for a Panda (and Beagle) ? Thanks in advance, Dave

15 years, 6 months

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Draft of next weeks public review

by Michael Hope

Hi there. I've uploaded a draft of the slides and notes for next weeks public review at: http://bazaar.launchpad.net/~linaro-toolchain-wg/+junk/publicreview1105/fil… 'Toolchain Public Review 11.05.odp' is a set of slides I'll talk to. The first 15-20 minutes will go through these to describe our focus and goals and how they tie together the blueprints and priorities. The rest of the session will go through the current blueprints and priorities. See: Toolchain Blueprints (short).pdf for the summary version and: Toolchain Blueprints (long).pdf for the long version. The long version is interesting if you can't find a particular tool or technology. It may be small enough to be called out as a single work item. These are only a draft, but I realised I haven't shared the plans with the rest of the group very well and Monday's meeting won't be the best. I'm on holiday tomorrow but feel free to send me any comments, -- Michael

15 years, 6 months

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Reviewing blueprints for the TSC

by Michael Hope

Hi there. I've been going through the blueprints in preparation for next weeks TSC review. The top level topics are good, and I'd like to have the rest of the engineering blueprints checked over and updated to match what we talked about at the summit. Ira, could you please create blueprints for the areas you plan to look into? Anything that will take longer than a month should have a blueprint. It's worth having a catch-all blueprint for anything left over. Please add these as a dependency to: https://blueprints.launchpad.net/linaro/+spec/tr-toolchain-neon-performance Zach, could you check: https://blueprints.launchpad.net/linaro-toolchain-misc/+spec/ltrace-support https://blueprints.launchpad.net/linaro/+spec/tr-toolchain-openocd Peter, there's a whole range of QEMU ones that could do with a pass over. For more about the review, see: https://wiki.linaro.org/Releases/1105/PublicPlanReview For a list of all of the toolchain blueprints, see: http://ex.seabright.co.nz/helpers/blueprints#toolchain -- Michael

15 years, 6 months

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Mixed vector sizes

by Ira Rosen

Hi, I started to look into mixed vector sizes (in the same loop). My main reason for this was to allow widening and narrowing instructions, that have different vector sizes for src and dest, to work properly. My example was widen_mult (int = short * short), I thought its implementation was not optimal. But now that I have a working GCC mainline for ARM, I see that it works just fine. short ub[], uc[]; int c[]; for (i = 0; i < n; i++) c[i] = ub[i] * ua[i]; is compiled as: .L11: add r1, r1, #1 vldmia r4!, {d18-d19} cmp r5, r1 vldmia ip!, {d16-d17} vmull.s16 q10, d18, d16 vstr d20, [r3, #-32] vstr d21, [r3, #-24] vmull.s16 q8, d19, d17 vstr d16, [r3, #-16] vstr d17, [r3, #-8] add r3, r3, #32 bhi .L11 which looks good to me at least from the vmull point of view. Does anyone have an example when mixed vector size instructions are not used properly? Another reason for mixed sizes could be cases where only part of the loop can be vectorized with the wider vectors. I don't know how common this is. Are there any other reasons to implement mixed vector sizes? I understand that this can be a useful feature, I am just not sure it's the most important one. Thanks, Ira

15 years, 6 months

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Backport criteria

by Michael Hope

I've been going through the ChangeLog for the release and am having trouble justifying some of the changes brought in. In particular: * -fstrict-volatile-bitfields, which is more appropriate for bare metal/kernel code * Cortex-M4 support * C locale support in libstdc++-v3 The march/mcpu clean up is OK but marginal. Our focus is time based performance on the Cortex-A series with an implied applications over kernel/bare metal. This is a very narrow view, but every non-performance line of code we bring in can also bring in a bug. Any thoughts? For those who are looking at using our toolchain, is earlier access to other toolchain improvements interesting? -- Michael

15 years, 6 months

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Upstream GCC feature freeze

by Andrew Stubbs

Hi all, As you may or may not know, upstream GCC has now entered 'stage 3' of it's development cycle. This will last until spring. This means that they are only accepting bug fixes and documentation improvements. New features and any performance improvements must wait until GCC 4.6 branches, prior to release, and GCC 4.7 development opens. During this process, our usual preferred work flow (upstream first) will not work, so we'll have to do something else. Here's my proposal: * Create a new Launchpad branch for GCC 4.6. * Synchronize this branch with upstream regularly * once per week, perhaps. * Try to get upstream approval for all new patches in the usual way * on the understanding that they won't be applied until stage 1 * bug fixes are unaffected and may commit as usual. * Commit all pending patches to our own 4.6 branch * and backport them to our 4.5, branch, of course. * Usual "no test regressions" policy applies to our own patches * but beware regressions from merges from upstream. * we may want to track the clean 4.6 test results for comparison This is little different to what we do with the 4.5 release branch now. Thoughts? Andrew

15 years, 6 months

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Linaro GCC 4.5 2010-11 released

by Michael Hope

The Linaro Toolchain Working Group is pleased to announce the latest release of Linaro GCC 4.5. Linaro GCC 4.5 is the fourth release in the 4.5 series. Based off the latest GCC 4.5.1+svn164911, it includes many ARM-focused performance improvements and bug fixes. Interesting changes include: * Various NEON related fixes * Performance improvements * A clean up of some of the testsuite test cases * An updated version of the __sync multicore primitives * Improvements in data packing when optimising for size * C locale support in libstdc++-v3 This release adds the new option -fstrict-volatile-bitfields and enables it by default on ARM. See doc/invoke.texi for more information. The source tarball is available from: https://launchpad.net/gcc-linaro/+milestone/4.5-2010.11-0 Downloads are available from the Linaro GCC page on Launchpad: https://launchpad.net/gcc-linaro Note that there were no changes to the 4.4 series. -- Michael

15 years, 6 months

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