Re: [PATCH 00/30] [ARM] Reworking the -mcpu, -march and -mfpu options

[Christophe Lyon <christophe dot lyon at linaro dot org>]

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.
>
> R.
>
> 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-common.c
>   [arm] Use standard option parsing code for detecting thumb-only
>     targets
>   [arm] Allow CPU and architecture extensions to be defined as aliases
>   [arm] Allow new extended syntax CPU and architecture names during
>     configure
>   [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
>
> ----------------2.7.4--
>

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?

Thanks,

Christophe