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Re: RFC: Saving and restoring the assembler state during assembly

by Richard Sandiford

Dave Martin <dave.martin(a)linaro.org> writes: > However, there's not really anything fundamentally > architecture-specific about this problem, and ideally the solution and > the directives should not be architecture-specific either. > One option which appeals to me is to have some directives which can > exist across all architectures, and do something analogous to what > .set push and ,set pop do on MIPS. FWIW, this sounds like a really good idea to me. I won't argue about the syntax (I have no particular preference). > I feel that the environment should also include global, > target-independent state such as the current macro mode (.altmacro > versus .noaltmacro) and current ELF section stack state, but not > symbols or macro definitions themselves. Sounds reasonable. To state the obvious, we'd have to make the existing target-dependent groupings (like .set push/pop on MIPS) work with this new scheme, but those directives musn't affect this extra target-independent information. So the new directives would interact with both the traditional .pushsection and the traditional target-dependent directives, even though those two features would otherwise remain independent. That is, .pushsection and .set push/pop operate on conceptually separate stacks whoses pushes and pops can be freely mixed. But .pushsection and the new directives would need to be strictly stacked; pops must have the same form as their corresponding pushes. Combinations of .set push/pop and the new directives would also need to be strictly stacked. Nothing a bit of code can't handle though. Richard

13 years, 3 months

RFC: Saving and restoring the assembler state during assembly

by Dave Martin

Hi all, On ARM, we've now hit the problem a few times of temporarily overriding the assembler state (or rather, not being able to do this reliably). For example, sometimes there's a need to assemble a few instructions for a different architecture version so we can optionally execute or skip them at run-time is not really possible at present. This sort of feature is especially useful in macros but can be useful elsewhere too. There seem to be some target-specific solutions to this problem already. MIPS has its "option stack", maintained by .set push and .set pop directives. From the documentation, it sounds like this saves/restores a somewhat comprehensive set of state, but doesn't make much syntactic sense on arches which use .set to define symbols (i.e., most arches). PowerPC also has .machine push and .machine pop, but those only act on one specific aspect of the assembler state, and therefore aren't as portable a concept. However, there's not really anything fundamentally architecture-specific about this problem, and ideally the solution and the directives should not be architecture-specific either. One option which appeals to me is to have some directives which can exist across all architectures, and do something analogous to what .set push and ,set pop do on MIPS. My names would be .pushenv and .popenv, but obviously, they can be named any way people like. (For now I'm stealing groff's "environment" terminology to refer to such saved and restored state -- hence "env". Again, the nomenclature is arbitrary.) These directives would save and restore a target-specific set of state, which the philosophy that anything that can reasonably be changed with a directive mid-file can also be saved and restored with .pushenv/.popenv. Effectively, .popenv would be equivalent to issuing the necessary set of assembler directives to restore the assembler state to whatever it was at the last .pushenv (including the state of the environment stack itself) I feel that the environment should also include global, target-independent state such as the current macro mode (.altmacro versus .noaltmacro) and current ELF section stack state, but not symbols or macro definitions themselves. Currently, neither the macro mode nor the behaviour of .previous is reliably restorable after being changed (unless I missed something). This can result in unexpected behaviour after a macro which switches sections or changes the macro mode. This seems unfortunate since on most arches there is no syntactic difference between a machine instruction and a macro invocation -- hence in the presence of macros, the only time you're really 100% certain what .previous will do is immediately after a .pushsection or .section directive (which obviously is not much use). Comments are welcome -- at the moment this is just a fuzzy idea for a feature which might prove useful. I haven't investigated the implementation implications -- maybe it could be built straightforwardly around the current MIPS directives. Cheers ---Dave

13 years, 3 months

[ACTIVITY] August 7-11

by Ira Rosen

Hi, * fixed PR 50014 and 50039 - to be backported to linaro-gcc * tested the patch to change the default vector size on NEON * found one test that fails with quad-words - gcc.c-torture/execute/mode-dependent-address.c. Debugging it with Ramana. * started looking into widening shifts Vacation plans: next week Monday and Wednesday and August 22 - 30. Ira

13 years, 3 months

ld in current (4.6-2011.07-0-8-2011-07-25_12-42-06) toolchain fails to link uboot

by Bernhard Rosenkranzer

Hi, ld in the current (4.6-2011.07-0-8-2011-07-25_12-42-06) Android toolchain fails to link uboot: arm-eabi-ld: /mnt/user/bero/android-iMX53-20110716151649/out/target/product/iMX53/obj/u-boot/lib/libgeneric.o: Unknown mandatory EABI object attribute 44 arm-eabi-ld: failed to merge target specific data of file /mnt/user/bero/android-iMX53-20110716151649/out/target/product/iMX53/obj/u-boot/lib/crc16.o arm-eabi-ld: /mnt/user/bero/android-iMX53-20110716151649/out/target/product/iMX53/obj/u-boot/lib/libgeneric.o: Unknown mandatory EABI object attribute 44 arm-eabi-ld: failed to merge target specific data of file /mnt/user/bero/android-iMX53-20110716151649/out/target/product/iMX53/obj/u-boot/lib/crc32.o arm-eabi-ld: /mnt/user/bero/android-iMX53-20110716151649/out/target/product/iMX53/obj/u-boot/lib/ctype.o: Unknown mandatory EABI object attribute 44 arm-eabi-ld: failed to merge target specific data of file /mnt/user/bero/android-iMX53-20110716151649/out/target/product/iMX53/obj/u-boot/lib/ctype.o arm-eabi-ld: /mnt/user/bero/android-iMX53-20110716151649/out/target/product/iMX53/obj/u-boot/lib/div64.o: Unknown mandatory EABI object attribute 44 arm-eabi-ld: failed to merge target specific data of file /mnt/user/bero/android-iMX53-20110716151649/out/target/product/iMX53/obj/u-boot/lib/div64.o arm-eabi-ld: /mnt/user/bero/android-iMX53-20110716151649/out/target/product/iMX53/obj/u-boot/lib/errno.o: Unknown mandatory EABI object attribute 44 arm-eabi-ld: failed to merge target specific data of file /mnt/user/bero/android-iMX53-20110716151649/out/target/product/iMX53/obj/u-boot/lib/errno.o arm-eabi-ld: /mnt/user/bero/android-iMX53-20110716151649/out/target/product/iMX53/obj/u-boot/lib/ldiv.o: Unknown mandatory EABI object attribute 44 arm-eabi-ld: failed to merge target specific data of file /mnt/user/bero/android-iMX53-20110716151649/out/target/product/iMX53/obj/u-boot/lib/ldiv.o I believe this is already fixed in upstream binutils (or at least in hjl's 2.21.52.0.2 release from kernel.org /pub/linux/devel/binutils). ttyl bero

13 years, 3 months

tomorrow's call cancelled.

by Ramana Radhakrishnan

Given I'm away at some internal training and we had one last week . I decided to cancel this. Ramana

13 years, 3 months

[ACTIVITY] report week 31

by Peter Maydell

RAG: Red: Amber: OMAP3 patch upstreaming is slower progress than hoped Green: Current Milestones: || || Planned || Estimate || Actual || ||qemu-linaro 2011-08 || 2011-08-18 || 2011-08-18 || || 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 || == upstream-omap3-patches == * discussion with upstream about how best to model omap-gpmc as qdev == other == * Attended Linaro Connect Q3.11 * submitted some patches which fix minor bugs that were preventing the QEMU M3 model from booting the Keil example binary images * miscellaneous upstream patch review Current qemu patch status is tracked here: https://wiki.linaro.org/PeterMaydell/QemuPatchStatus Absences: 9, 10 August: manning Linaro demo stand at APM 15-19 August: KVM Forum and LinuxCon NA, Vancouver

13 years, 3 months

[ACTIVITY] Weekly status

by Richard Sandiford

== Last week (Linaro Connect) == * Reran libav comparisons after Ira's fix for excessive promotion. The vectorized versions are now at least as good as the non-vectorised ones. Updated wiki page with new asm output and microbenchmark results. * More work on SMS. I have some patches that wire up the ddg code to IV analysis. It gave some nice benchmark improvements, but also some regressions. Traced the regressions down to cases where the schedule for small iis generated too many moves. E.g. in a small microbenchmark, we were able to schedule 6 instructions with an ii of 3 (i.e. in a loop iteration of 3 cycles), but then needed to add ~9 moves in order to keep the dependencies correct. We got much better code with a larger ii and fewer moves. Wrote a patch to estimate how many moves would be added, and to try to a larger ii if the number of moves is too high. This improved the results for one benchmark independently of the iv patch, and had no effect on the others. Discussed this with Revital, who said that Mustafa had tried a similar thing but seen no benefit. * Got powerpc-ibm-aix5.3 bootstraps working. Needs a few local fixes due to C++ bootstrapping. Used it to test a couple of preparatory patches for the IV work. Submitted those patches upstream. * Ran benchmarks with -fno-schedule-insns after seeing that the first scheduling pass was responsible for the main NEON-vs.-non-NEON regression in EEMBC. It fixed that case, but as expected, made others worse. Mentioned this to Ramana, who pointed me at -fsched-pressure. Reran the benchmarks with -fsched-pressure instead of -fno-schedule-insns. It too fixed the main regression, and improved a couple of other tests too. It showed a regression in another test though. Looked at that regression. It was a case where many registers were live across a loop, but not used in it. This was causing the loop to have a very conservative schedule. It would be better to spill some of the other registers instead. Wrote a patch to take loops into account, and it seemed to do the right thing for EEMBC. Sent it to Andreas, after Ulrich mentioned that he had been looking at -fsched-pressure problems on s390. Andreas is away for a while, though, so I might put this on the back burner until he gets back. == This week == * SMS * auto inc/dec * libav, perhaps Richard

13 years, 3 months

[ACTIVITY] Aug 1-5

by Ira Rosen

Hi, * committed upstream a patch that reduces over-promotion of vector operations * started to work on a new version of the patch to change the default vector size for Neon * attended Linaro connect Ira

13 years, 3 months

[ACTIVITY] Weekly status

by Revital Eres

* Committed a set of SMS patches to trunk and gcc-linaro branch. * Implemented a hack to evaluate the potential of SMS on SPEC2006/libqauntum. * involved in non linaro issue

13 years, 3 months

[ACTIVITY] 2011-08-05

by David Gilbert

== QEMU == * After discussion with Peter started writing QEMU fixup for 64bit atomic helper version location. * Sent fixes for soc-dma code to qemu list * Trying to understand just how much of omap_dma's code is needed. == Other == * Travelling to/from connect * Wanted to dial into some of the seessions in Corpus and Magdelen rooms but the remote audio from them was unusable. Dave

13 years, 3 months

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