I tried to bootstrap current GCC trunk and our latest gcc-linaro-4.6
in profile guided, link time optimisation, and SMS modes. The results
are here:
https://wiki.linaro.org/MichaelHope/Sandbox/PGOLTOSMSStatus1
Short story: you can't bootstrap in LTO or PGO on ARM as they run out
of memory. i686 LTO is broken on trunk and gcc-linaro-4.6. SMS is
fine in general.
I'll run these once a week and keep an eye on them. A -fwhopr instead
of -flto may help on ARM. I don't know why the PGO build runs out of
memory.
-- Michael
Måns pointed me at the IDCT throughput test that's included with
libav. I've written up a page on how to build and run it at:
https://wiki.linaro.org/MichaelHope/Sandbox/LibAvDCT
Included are results with and without the vectoriser. In all cases
the vectoriser improves things, including increasing the SIMPLE-C
version by 11 % and the peak by 17 %.
The coefficient of variance is low so the results are consistent. I
haven't investigated the benchmark itself to see if its valid - we
could be vectorising the loop overhead instead of the IDCT itself.
-- Michael
Please coordinate with Jon Masters at RedHat/Fedora and Adam Conrad at
Ubuntu/Debian on this. (Cc'ing the cross-distro list, through which the
recent ARM summit at Linux Plumbers was organized.)
Cheers,
- Michael
On Sep 16, 2011 8:41 AM, "David Gilbert" <david.gilbert(a)linaro.org> wrote:
> OK, so we seem to have agreement here that what we want is autodetect
> for eglibc and
> forget about the triplet; well technically that probably makes my life
> easier, and I don't
> think it's too hard a sell.
>
> Dave
>
> _______________________________________________
> linaro-toolchain mailing list
> linaro-toolchain(a)lists.linaro.org
> http://lists.linaro.org/mailman/listinfo/linaro-toolchain
* Linaro GCC
Spun 4.5 and 4.6 2011.09 GCC release tarballs. Uploaded them to
Michael's server, and kicked off the tests.
Continued work on my new constant optimization experiments. I now have
it tracking all the constants and am looking at how to detect the
optimization opportunities. So far it only calculates how exprensive it
would be to generate a value by adding to an existing constant, which is
a start at least. I'm having difficulties detecting whether changing an
insn will make it's parent (dependency-wise) obsolete, or not (and
therefore whether to count its costs - there's no problem for
instructions that overwrite an entire register, but ones that write to
portions of registers (such as MOVT) make more complex dependency
chains, and the def-use chains don't seem to be sorted into the order of
use.
* Other
Half day vacation on Thursday.
* Added testcases to Richard's micro benchmarks taken from libav.
* Discussed with Ayal the new version of the patch to support
instructions with
REG_INC_NOTE in SMS which causes bootstrap failure. I intend to debug
the bootstrap failure in order to find the cause for it.
(http://gcc.gnu.org/ml/gcc-patches/2011-08/msg01216.html)
== String routines ==
* Tidying up bits of cortex strings for the release process
* Nailing down the behaviour of config.sub and the config systems in
gcc, binutils and eglibc
== Other ==
* A discussion on synchronisation primitives on various CPUs that
started on the gcc list
- looking at http://www.cl.cam.ac.uk/~pes20/cpp/cpp0xmappings.html
- pointing out the 64bit instructions
- asking why they used isb's when neither the kernel or gcc use
them (answer the DMBs should
be fine as well, but there is some debate over which is
quicker, oh and DMBs are
converted to slower dsb's on most A9s due to an errata).
* Looking for docs on the non-core bits of current SoCs
* Extracting some denbench stats from a few months back for Ramana
About a day of non-Linaro IBM stuff.
Dave
RAG:
Red:
Amber:
Green:
NB: since qemu-linaro releases demonstrably go out on schedule
every month I'm dropping them from the milestone tables in these
reports, in favour of blueprint completion dates (usually they'll
be planned for dates coinciding with a qemu-linaro release).
Current Milestones:
|| || Planned || Estimate || Actual ||
||add-omap3-networking || 2011-10-13 || 2011-10-13 || ||
||a15-systemmode-planning || 2011-10-13 || 2011-10-13 || ||
||a15-usermode-support || 2011-11-10 || 2011-11-10 || ||
||upstream-omap3-cleanup || 2011-11-10 || 2011-11-10 || ||
Historical Milestones:
||qemu-linaro 2011-04 || 2011-04-21 || 2011-04-21 || 2011-04-21 ||
||qemu-linaro 2011-05 || 2011-05-19 || 2011-05-19 || n/a ||
||close out 1105 blueprints || 2011-05-28 || 2011-05-28 || 2011-05-19 ||
||complete 1111 planning || 2011-05-28 || 2011-05-28 || 2011-05-27 ||
||qemu-linaro-2011-06 || 2011-06-16 || 2011-06-16 || 2011-06-16 ||
||qemu-linaro-2011-07 || 2011-07-21 || 2011-07-21 || 2011-07-21 ||
||qemu-linaro 2011-08 || 2011-08-18 || 2011-08-18 || 2011-08-18 ||
||qemu-linaro 2011-09 || 2011-09-15 || 2011-09-15 || 2011-09-15 ||
== linaro-qemu-11.11 ==
* completed this month's release
== add-omap3-networking ==
* investigated why qemu's usb-net model didn't work on the beagle;
this was due to a bug in the usb-ohci controller model; patches
sent upstream. Fix will go into qemu-linaro 2011-10.
== a15-system-mode-planning ==
* wrote up options and my suggestion on the wiki:
https://wiki.linaro.org/PeterMaydell/QemuA15
* just need to discuss with Michael and turn this into a roadmap entry
== a15-usermode-support ==
* complete but untested implementation of UDIV and SDIV
* fused multiply-accumulate: implemented decode, and the special-cases
parts of the softfloat implementation (NaN, inf, etc); the difficult
bit of actually implementing the operation remains
== other ==
* meetings: toolchain, pdsw doughnuts, AFDS
Current qemu patch status is tracked here:
https://wiki.linaro.org/PeterMaydell/QemuPatchStatus
Absences (to end of year):
Sep 19, Sep 29-Oct 07, Oct 17, Nov 21, Dec 15-Jan 03: leave
Oct 30-Nov 04: Linaro Connect Q4.11
As mentioned on the standup call this morning, I've been trying to get my head
around the way different parts of the toolchain using the config scripts and the
triplets. I'd appreciate some thoughts on what the right thing to do
is, especially
since there was some unease at some of the ideas.
My aim here is to add an armv7 specific set of routines to the eglibc
ports and get this picked up
only when eglibc is built for armv7; but it's getting a bit tricky.
eglibc shares with gcc and binutils a script called config.sub (that
lives in a separate repository)
which munges the triplet into a $basic_machine and validates it for a
set of known
triplets.
So for example it has the (shell) pattern:
arm | arm[bl]e | arme[lb] | armv[2345] | armv[345][lb]
to recognise triplets of the form arm- armbe- armle-
armel- armbe- armv5- armv5l- or armv5b-
It also knows more obscure things such as if you're configuring for
a netwinder it's an armv4l- system running linux - but frankly most
of that type of thing are a decade or two out of date. Note it doesn't
yet know about armv6 or armv7.
eglibc builds a search path that at the moment includes a path under
the 'ports' directory of the form
arm/eabi/$machine
where $machine is typically the first part of your triplet; however
at the moment eglibc doesn't have any ARM version specific subdirectories.
If I just added an ports/sysdeps/arm/eabi/armv7 directory it wouldn't
use it because
it searches in arm/eabi/arm if configured with the triplet arm-linux-gnueabi or
--with-cpu sets $submachine (NOT $machine) - so if you pass --with-cpu=armv7
it ends up searching
arm/eabi/arm/armv7
if you used the triplet arm-linux-gnueabi. If you had a triplet like
armel then I think
it would be searching
arm/eabi/armel/armv7
So my original patch (
http://old.nabble.com/-ARM--architecture-specific-subdirectories,-optimised…
)
did the following:
* Modified the paths searched to be arm/eabi (rather than arm/eabi/$machine)
* If $submachine hadn't been set by --with-cpu then autodetect it
from gcc's #defines
which meant that it ignored the start of the triplet and let you
specify --with-cpu=armv7
After some discussion with Joseph Myers, he's convinced me that isn't
what eglibc
is expecting (see later in the thread linked above); what it should
be doing is that
$machine should be armv7 and $submachine should be used if we wanted
say a cortex-a8 or
cortext-a9 specific version.
My current patch:
* adds armv6 and armv7 to config.sub
* adds arm/eabi/armv7 and arm/eabi/armv6t2 and one assembler
routine in there.
* If $machine is just 'arm' then it autodetects from gcc's #defines
* else if $machine is armv.... then that's still $machine
So if you use:
a triplet like arm-linux-gnueabi it looks at gcc and if that's configured
for armv7-a it searches arm/eabi/armv7
a triplet like armv7-linux-gnueabi then it searches arm/eabi/armv7
irrespective
of what gcc was configured for
a triplet like armv7-linux-gnueabi and --with-cpu=cortex-a9 then it searches
arm/eabi/armv7/cortex-a9 then arm/eabi/armv7
As far as I can tell gcc ignores the first part of the triplet, other than
noting it's arm and spotting if it ends with b for big endian; (i.e.
configuring gcc with armv4-linux-gnueabi and armv7-linux-gnueabi
ends up with the same compiler).
binutils also mostly ignores the 1st part of the triple - although is
a bit of a mess
with different parts parsing it differently (it seems to spot arm9e for some odd
reason); as far as I can tell gold will accept armbe* for big endian where as
ld takes arm*b !
If you're still reading, then the questions are:
1) Does the approach I've suggested make sense - in particular that the
machine directory chosen is based either on the triplet or where the triplet
doesn't specify the configuration of gcc; that's my interpretation of what
Joseph is suggesting.
2) Doing (1) would seem to suggest I should give config.sub armv6t2 and
some of the other complex names.
Dave
