The Linaro Toolchain Working Group (TCWG) is pleased to announce the 2018.04
snapshot of Linaro GCC 6 and 7 source packages.
o The GCC 7 series introduced an ABI change for ARM targets by fixing a bug
(present since GCC 5, see link below) that affects conformance to the procedure
call standard (AAPCS). The bug affects some C++ code where class objects are
passed by value to functions and could result in incorrect or inconsistent code
being generated. If the option -Wpsabi is enabled (on by default) the compiler
will emit a diagnostic note for code that might be affected by this ABI change.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77728
For an explanation of the changes please see the following website:
https://gcc.gnu.org/gcc-7/changes.html
o Linaro GCC 7 monthly snapshot[1] is based on FSF GCC 7.3+svn259627 and
includes performance improvements and bug fixes backported from mainline GCC.
The contents of this snapshot will be part of the 2018.05 stable[2] quarterly
release.
This snapshot tarball is available on:
http://snapshots.linaro.org/components/toolchain/gcc-linaro/7.3-2018.04/
Interesting changes in this GCC source package snapshot include:
* Updates to GCC 7.3+svn259627
o Linaro GCC 6 monthly snapshot[1] is based on FSF GCC 6.4+svn259634 and
includes performance improvements and bug fixes backported from mainline GCC.
This snapshot contents will be part of the next maintenance release.
This snapshot tarball is available on:
http://snapshots.linaro.org/components/toolchain/gcc-linaro/6.4-2018.04/
Interesting changes in this GCC source package snapshot include:
* Updates to GCC 6.4+svn259634
o Subscribe to the important Linaro mailing lists and join our IRC channels to
stay on top of Linaro development.
** Linaro Toolchain Development "mailing list":
http://lists.linaro.org/mailman/listinfo/linaro-toolchain
** Linaro Toolchain IRC channel on irc.freenode.net at @#linaro-tcwg@
* Bug reports should be filed in Bugzilla against GCC product:
http://bugs.linaro.org/enter_bug.cgi?product=GCC
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mailto:support@linaro.org
[1]. Source package snapshots are defined when the compiler is only
put through unit-testing and full validation is not performed.
[2]. Stable source package releases are defined as releases where the
full Linaro Toolchain validation plan is executed.
* Short week - a public holiday
* Return jump function
- Writing up issues with test cases for upstream discussion based on
the ipa-cp implementation
* LLVM astar regression
- Trying to reproduce with trunk LLVM vs trunk gcc
- Clang build fails in tx1 (likely due to not enough memory ?)
- Set it up on dev-01. I see about ~2% difference. The difference
goes away when I use -fno-devirtualize-speculative. This suggests the
issue is still present. Perf results are also consistent with this.
- Reducing a self-contained test case
== Progress ==
o GNU releases
* Various support on process and infra.
o LLVM
* Benchmarking job on-going
* Buildbots baby-sitting
* Completed EuroLLVM feedback
* Created ticket: outliner support on ARM
After internal and upstream discussions.
o Misc
* Various meetings and discussions.
Progress:
[Upstream]
Patch set posted implementing some missing ARMv8.2-FP16 instructions.
I believe Alex has gone back to double check if there are any more.
[VIRT-243]
Initial patch posted for the ARMv8.1-Atomics extension.
Looking at the summary from Friday night's test run suggests there are
errors; I'll be looking at those next week.
r~
Activity:
[TCWG-1384] Add support for missing TLS local exec relocations tl LLD
Have an implementation ready to go upstream next week. In process
found that Gold and BFD disagreed on test output. Turns out that there
was a bug in BFD, reviewed Renlin Li's patch for it. Took rather more
of my time than I expected.
[TCWG-1375] Set 4 patches upstream to complete the removal of the
global subtarget
No response as yet.
Raised https://bugs.llvm.org/show_bug.cgi?id=37212 clang and gcc are
producing technically illegal ELF for debug information (references to
local symbols defined in comdat groups), both gold and bfd have
special case code to handle this case, lld does not. Leads to loss of
debug illusion for templated and inlined C++ functions.
Other
- Some research into how spec files and multilib works in gcc to see
how it could fit into clang's driver model.
- Joined the ELF ABI google group to fulfil a promise I'd made at Euro
LLVM to comment on a thread about debug information in comdat groups.
Holiday on Tuesday
Plans:
- Ping reviews.
- Push fix for TCWG-1384 upstream alongside some refactoring patches.
- Add some more tests to LLD to close some holes in the code-coverage
statistics.
- Continue looking at laundry list of small LLD changes.
- Get back to building Android.
=== Work done during this GCC week ===
* stack-protector failure on GCC ARM: need feedback from community
+ prevent CSE of stack protector's guard first by adding some extra
UNSPEC then instead by making all memory accesses involved volatile
+ write 2 monstro regex (251 & 377 characters respectively) to catch the
bug on ARM, Thumb-2 and Thumb-1
+ testing and will submit for review later today once I have all test
results
+ discuss raising a CVE
* Misc:
+ Arm meetings
+ Meeting with ST to discuss how to implement something akin to multilib
+ spec files for LLVM
+ Linary syncs
+ review of "Implement getConstraintRegister for ARM and AArch64" patch
by Mikhail Maltsev
=== Plan for weeks up to 25 ===
* Paternity leave
* Get stack-protector failure fix committed
* DSGHACK-25 (Support arithmetic on FileCheck regex variable): finish patch
* Start looking into LLVM SPEC optimizations Linaro tickets
Progress:
* VIRT-65 [QEMU upstream maintainership]
+ 2.12 release kicked out the door; hopefully I can do a bit more
actual development work for a bit now...
+ investigating problems with execute-in-place-from-MMIO-device
functionality : the test case (for a Xilinx board model) crashes
reliably for me. I cooked up an RFC patch and sent it, but it
includes one weird hack and I'm not sure if it's the right approach...
+ we got a Coverity Scan run through after a couple of months of not
having one, and a pile of issues have accumulated. Waded through some
of them and flagged them up with the patch submitters who added the
code that introduced them.
Notes:
* QEMU will have not one but two interns working on Cortex-M0
and micro:bit support (one from Google Summer of Code and
one from Outreachy) !
* QEMU turns 15 years old this year. To celebrate we plan to
make the next release be 3.0 (and perhaps to have birthday
cake at KVM Forum?)
thanks
-- PMM
