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Re: [PATCH 00/30] [ARM] Reworking the -mcpu, -march and -mfpu options
- From: Christophe Lyon <christophe dot lyon at linaro dot org>
- To: "Richard Earnshaw (lists)" <Richard dot Earnshaw at arm dot com>
- Cc: "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>
- Date: Mon, 12 Jun 2017 13:49:31 +0200
- Subject: Re: [PATCH 00/30] [ARM] Reworking the -mcpu, -march and -mfpu options
- Authentication-results: sourceware.org; auth=none
- References: <cover.1497004220.git.Richard.Earnshaw@arm.com> <CAKdteOaQMUb=_g5eT0_L+L_A3_bGTC9AjhcL=vjEOWqHOq7gmA@mail.gmail.com> <firstname.lastname@example.org>
On 10 June 2017 at 01:27, Richard Earnshaw (lists)
> On 09/06/17 23:45, Christophe Lyon wrote:
>> Hi Richard,
>> On 9 June 2017 at 14:53, Richard Earnshaw <Richard.Earnshaw@arm.com> wrote:
>>> During the ARM BoF at the Cauldron last year I mentioned that I wanted
>>> to rework the way GCC on ARM handles the command line options. The
>>> problem was that most users, and even many experts, can't remember
>>> which FPU/SIMD unit comes with which CPU and that consequently many
>>> users were inadvertenly generating sub-optimal code for their system.
>>> This patch series implements the proposed change and provides support
>>> for a generic way of adding optional features to architectures and CPU
>>> names. The documentation patches at the end of the series explain the
>>> new syntax, so I won't repeat all that here. Suffice to say here that
>>> the result is that the -mfpu option now defaults to 'auto', which
>>> allows the compiler to infer the floating-point and simd options from
>>> the CPU/architecture options and that these options can normally be
>>> expressed in a context-specific manner like +simd or +fp without
>>> having to know precisely which variant is implemented. Long term I'd
>>> like to deprecate -mfpu and entirely move over to the new syntax; but
>>> it's too early to start that process now.
>>> All the patches in the series should build a working basic compiler,
>>> but the multilib selection will not work correctly until the relevant
>>> patches towards the end are applied. It is not really feasible to
>>> retain that functionality without collapsing too many of the patches
>>> together into one hunk. It's also possible that some tests in the
>>> testsuite may exhibit transient misbehaviour, but there should be no
>>> regressions by the end of the sequence (some tests no-longer run in
>>> the default configurations because the default CPU does not have
>>> floating-point support).
>>> Just two patches are to the generic code, but both are fairly trivial.
>>> One permits the sbitmap code to be used in the driver programs and the
>>> other provides a way of escaping the meta-character in some multilib
>>> reuse strings.
>>> I won't apply any of this series until those two patches have been
>>> approved, and I won't commit anything before the middle of next week
>>> even then. This is a fairly complex change and it deserves some time
>>> for people to comment before committing.
>>> Richard Earnshaw (30):
>>> [arm] Use strings for -march, -mcpu and -mtune options
>>> [arm] Rewrite -march and -mcpu options for passing to the assembler
>>> [arm] Don't pass -mfpu=auto through to the assembler.
>>> [arm] Allow +opt on arbitrary cpu and architecture specifications
>>> [arm] Add architectural options
>>> [arm] Add default FPUs for CPUs.
>>> [build] Make sbitmap code available to the driver programs
>>> [arm] Split CPU, architecture and tuning data tables.
>>> [ARM] Move cpu and architecture option name parsing code to
>>> [arm] Use standard option parsing code for detecting thumb-only
>>> [arm] Allow CPU and architecture extensions to be defined as aliases
>>> [arm] Allow new extended syntax CPU and architecture names during
>>> [arm] Force a CPU default in the config args defaults list.
>>> [arm] Generate a canonical form for -march
>>> [arm] Make -mfloat-abi=softfp work when there are no FPU instructions
>>> [arm] Update basic multilib configuration
>>> [arm] Make 'auto' the default FPU selection option.
>>> [arm] Rewrite t-aprofile using new selector methodology
>>> [arm] Explicitly set .fpu in cmse_nonsecure_call.S
>>> [genmultilib] Allow explicit periods to be escaped in MULTILIB_REUSE
>>> [arm][testsuite] Use -march=armv7-a+fp when testing hard-float ABI.
>>> [arm] Rewrite t-rmprofile multilib specification
>>> [arm][rtems] Update t-rtems for new option framework
>>> [arm][linux-eabi] Ensure all multilib variables are reset
>>> [arm][phoenix] reset all multilib variables
>>> [arm] Rework multlib builds for symbianelf
>>> [arm][fuchsia] Rework multilib support
>>> [arm] Add a few missing architecture extension options.
>>> [arm][doc] Document new -march= syntax.
>>> [arm][doc] Document changes to -mcpu, -mtune and -mfpu.
>>> gcc/Makefile.in | 2 +-
>>> gcc/common/config/arm/arm-common.c | 651 +++++++-
>>> gcc/config.gcc | 17 +-
>>> gcc/config/arm/arm-builtins.c | 4 +-
>>> gcc/config/arm/arm-cpu-cdata.h | 2444 +++++++++++++++++++++++------
>>> gcc/config/arm/arm-cpu-data.h | 1410 ++---------------
>>> gcc/config/arm/arm-cpu.h | 38 +
>>> gcc/config/arm/arm-cpus.in | 237 ++-
>>> gcc/config/arm/arm-isa.h | 20 +-
>>> gcc/config/arm/arm-protos.h | 56 +-
>>> gcc/config/arm/arm-tables.opt | 21 +-
>>> gcc/config/arm/arm.c | 337 ++--
>>> gcc/config/arm/arm.h | 75 +-
>>> gcc/config/arm/arm.opt | 15 +-
>>> gcc/config/arm/bpabi.h | 4 -
>>> gcc/config/arm/elf.h | 6 +-
>>> gcc/config/arm/linux-elf.h | 3 -
>>> gcc/config/arm/netbsd-elf.h | 4 -
>>> gcc/config/arm/parsecpu.awk | 295 +++-
>>> gcc/config/arm/t-aprofile | 200 +--
>>> gcc/config/arm/t-arm-elf | 173 +-
>>> gcc/config/arm/t-fuchsia | 33 +
>>> gcc/config/arm/t-linux-eabi | 4 +
>>> gcc/config/arm/t-multilib | 126 +-
>>> gcc/config/arm/t-phoenix | 20 +-
>>> gcc/config/arm/t-rmprofile | 147 +-
>>> gcc/config/arm/t-rtems | 49 +-
>>> gcc/config/arm/t-symbian | 34 +-
>>> gcc/config/arm/vxworks.h | 2 -
>>> gcc/doc/fragments.texi | 10 +-
>>> gcc/doc/invoke.texi | 371 ++++-
>>> gcc/genmultilib | 4 +-
>>> gcc/testsuite/gcc.dg/pr59418.c | 2 +-
>>> gcc/testsuite/gcc.target/arm/multilib.exp | 685 ++++++++
>>> gcc/testsuite/gcc.target/arm/pr51915.c | 2 +-
>>> gcc/testsuite/gcc.target/arm/pr52006.c | 2 +-
>>> gcc/testsuite/gcc.target/arm/pr53187.c | 2 +-
>>> libgcc/config/arm/cmse_nonsecure_call.S | 8 +
>>> 38 files changed, 5073 insertions(+), 2440 deletions(-)
>>> create mode 100644 gcc/config/arm/t-fuchsia
>>> create mode 100644 gcc/testsuite/gcc.target/arm/multilib.exp
>> I wanted to run a validation with the full series applied as one patch
>> over r249050,
>> so I just downloaded all the patches, concatenated them in order, but the result
>> fails to apply. (conflicts with arm-cpu-cdata.h, arm-cpus.in,
>> t-aprofile, t-rmprofile)
>> Am I missing something?
> I really appreciate you trying to do this...
> I rebased the patch series sometime on Tuesday/Wednesday just before Jim
> Wilson committed his falkor change; you'll need to back out to just
> before r248944. I can't think of anything else that might have just
> gone in that might conflict. For arm-cpu-cdata.h (and the other
> auto-generated files, like arm-cpu-data.h) you can just delete the file
> and it will be rebuilt automatically, the others really do need the
> conflict to be resolved.
> Obviously I'll rebase again just before the commit, but propagating such
> changes through the patch series is quite tedious and I don't want to do
> it any more than necessary :-).
> It would be easier if the generated files weren't checked in to the
Starting a validation of the whole patch against r248942 did work, thanks.
The results are here:
Regressions are detected in many configurations, unfortunately.
Some may be caused by the fact that I've upgraded to dejagnu-1.6+ for
and thus "multilib flags" are now prepended rather than appended, but
I don't think that's the majority.
To help you understand/group all the reports:
- all "arm-none-linux-gnueabi" with REGRESSED now have:
FAIL: gcc.target/arm/neon-thumb2-move.c (test for excess errors)
FAIL: gcc.target/arm/no-volatile-in-it.c scan-assembler-not ldrgt
- same for the 2 configs arm-none-eabi --with-cpu=cortex-a9
- all "arm-none-linux-gnueabihf" and "armeb-none-linux-gnueabihf" with
REGRESSED now have:
FAIL: gcc.target/arm/no-volatile-in-it.c scan-assembler-not ldrgt
- arm-none-eabi --with-cpu=cortex-m3 now has:
gcc.target/arm/no-volatile-in-it.c scan-assembler-not ldrgt
gcc.target/arm/thumb2-slow-flash-data-2.c (test for excess errors)
gcc.target/arm/thumb2-slow-flash-data-3.c (test for excess errors)
gcc.target/arm/thumb2-slow-flash-data-4.c (test for excess errors)
gcc.target/arm/thumb2-slow-flash-data-5.c (test for excess errors)
gcc.target/arm/thumb2-slow-flash-data-4.c scan-assembler-times #1\\.0e\\+0 3
gcc.target/arm/thumb2-slow-flash-data-5.c scan-assembler-not #1\\.0e\\+0
- The 2 cells with "BIG-REG" mean regressions where detected, but the report
is >100kb so it was attached as a .xz file, click on 'BIG-REG" to download it.
- the cells with "BETTER" can be questionable: it means no new failure
appeared, but PASS -> UNSUPPORTED is considered as "better". Here
we have cases with several thousands (!) of tests becoming unsupported,
which looks a bit suspicious.
Among other things, I've noticed that when passing -march=armv5t,
xgcc -march=armv5t -fno-diagnostics-show-caret
-fdiagnostics-color=never -mfpu=neon -mfloat-abi=softfp -march=
armv7-a -c -o arm_neon_ok15574.o arm_neon_ok15574.c
arm_neon_ok15574.c:9:4: error: #error Architecture does not support NEON.
compiler exited with status 1
I'd expect -march=armv7-a to allow to use -mfpu=neon?
Regarding the new multilib.exp tests introduced by the patch, my testing
did not run it because I have no configuration setting aprofile or rmprofile.
Maybe it's time I add one, or update the existing ones.
I didn't see any message "skipping multilib tests due to
but I guess that's because my runs are not verbose enough. That being said,
I'm not sure how the multilib_flags are set in board_info? Is that derived from
>From this report page, you can also click on "sum" and "log" (when
present) to download the gcc.sum or gcc.log files.
Feel free to ask more details if I haven't been clear enough.