[PATCH][GCC] arm: add armv9-a architecture to -march

[Christophe Lyon]

Hi,

Indeed I wasn't asking for a ~partial revert, rather making sure the new
behaviour is intended: current GCC trunk
won't build with A-profile multilibs unless using trunk binutils. We
probably had the same situation when
v8-a was introduced, just maybe I wasn't running CI with multilibs enabled
at that time.

Anyway, as Richard & Ramana said, if there is no real need for v9-a
multilibs, dropping them would save
build time and disk size.

Thanks,

Christophe


On Tue, Nov 16, 2021 at 1:29 PM Ramana Radhakrishnan <
Ramana.Radhakrishnan@arm.com> wrote:

> Hi There,
>
>
>
> I think for AArch32 mapping it back to armv8-a sounds sufficient.  Unless
> we have string or math routines in newlib that make use of any ACLE guards
> that are beyond armv8-a …
>
>
>
> Ramana
>
>
>
>
>
> *From: *Richard Earnshaw <Richard.Earnshaw@foss.arm.com>
> *Date: *Tuesday, 16 November 2021 at 11:48
> *To: *Christophe Lyon <christophe.lyon.oss@gmail.com>, Przemyslaw Wirkus <
> Przemyslaw.Wirkus@arm.com>
> *Cc: *Ramana Radhakrishnan <Ramana.Radhakrishnan@arm.com>,
> gcc-patches@gcc.gnu.org <gcc-patches@gcc.gnu.org>, Richard Earnshaw <
> Richard.Earnshaw@arm.com>
> *Subject: *Re: [PATCH][GCC] arm: add armv9-a architecture to -march
>
> You can't make an omelette without breaking eggs, as they say.  New
> architectures need new assemblers.
>
> However, I wonder if there's anything in v9-a that significantly affects
> the quality of the base multilib code needed for building the libraries.
>   It might be that we can deal with v9-a by just mapping it to the v8-a
> equivalents.  That would then avoid the need for an updated assembler,
> and reduce the build time and install footprint.
>
> R.
>
>
> On 16/11/2021 08:03, Christophe Lyon via Gcc-patches wrote:
> > Hi,
> >
> >
> > On Tue, Nov 9, 2021 at 12:36 PM Przemyslaw Wirkus via Gcc-patches <
> > gcc-patches@gcc.gnu.org> wrote:
> >
> >>>>> -----Original Message-----
> >>>>> From: Przemyslaw Wirkus
> >>>>> Sent: 18 October 2021 10:37
> >>>>> To: gcc-patches@gcc.gnu.org
> >>>>> Cc: Richard Earnshaw <Richard.Earnshaw@arm.com>; Ramana
> >>>>> Radhakrishnan <Ramana.Radhakrishnan@arm.com>; Kyrylo Tkachov
> >>>>> <Kyrylo.Tkachov@arm.com>; nickc@redhat.com
> >>>>> Subject: [PATCH][GCC] arm: add armv9-a architecture to -march
> >>>>>
> >>>>> Hi,
> >>>>>
> >>>>> This patch is adding `armv9-a` to -march in Arm GCC.
> >>>>>
> >>>>> In this patch:
> >>>>>    + Add `armv9-a` to -march.
> >>>>>    + Update multilib with armv9-a and armv9-a+simd.
> >>>>>
> >>>>> After this patch three additional multilib directories are available:
> >>>>>
> >>>>> $ arm-none-eabi-gcc --print-multi-lib .; [...vanilla multi-lib
> >>>>> dirs...] thumb/v9-a/nofp;@mthumb@march=armv9-a@mfloat-abi=soft
> >>>>> thumb/v9-a+simd/softfp;@mthumb@march=armv9-a+simd@mfloat-
> >>>>> abi=softfp
> >>>>> thumb/v9-a+simd/hard;@mthumb@march=armv9-a+simd@mfloat-
> >>>>> abi=hard
> >>>>>
> >>
> >
> > This is causing a GCC build failure when using "old" binutils (I'm using
> > 2.36.1),
> > because the new -march=armv9-a option is not supported. This breaks the
> > multilib support.
> >
> > I don't remember how we handled similar cases in the past? Is that just
> > "expected", and
> > "current" GCC needs "current" binutils, or should we have a multilib list
> > dependent on
> > the actual binutils support? (I think this is not the case, and it sounds
> > like an undesirable
> > extra complication in an already overcrowded mutilib-Makefile)
> >
> > Christophe
> >
> >>>> New multi-lib directories under
> >>>>> $GCC_INSTALL_DIE/lib/gcc/arm-none-eabi/12.0.0/thumb are created:
> >>>>>
> >>>>> thumb/
> >>>>> +--- v9-a
> >>>>> |    |--- nofp
> >>>>> |
> >>>>> +--- v9-a+simd
> >>>>>       |--- hard
> >>>>>       |--- softfp
> >>>>>
> >>>>> Regtested on arm-none-eabi cross and no issues.
> >>>>>
> >>>>> OK for master?
> >>
> >> Thanks.
> >>
> >> commit 32ba7860ccaddd5219e6dae94a3d0653e124c9dd
> >>
> >>> Ok.
> >>> Thanks,
> >>> Kyrill
> >>>
> >>>
> >>>>>
> >>>>> gcc/ChangeLog:
> >>>>>
> >>>>>    * config/arm/arm-cpus.in (armv9): New define.
> >>>>>    (ARMv9a): New group.
> >>>>>    (armv9-a): New arch definition.
> >>>>>    * config/arm/arm-tables.opt: Regenerate.
> >>>>>    * config/arm/arm.h (BASE_ARCH_9A): New arch enum value.
> >>>>>    * config/arm/t-aprofile: Added armv9-a and armv9+simd.
> >>>>>    * config/arm/t-arm-elf: Added arm9-a, v9_fps and all_v9_archs
> >>>>>    to MULTILIB_MATCHES.
> >>>>>    * config/arm/t-multilib: Added v9_a_nosimd_variants and
> >>>>>    v9_a_simd_variants to MULTILIB_MATCHES.
> >>>>>    * doc/invoke.texi: Update docs.
> >>>>>
> >>>>> gcc/testsuite/ChangeLog:
> >>>>>
> >>>>>    * gcc.target/arm/multilib.exp: Update test with armv9-a entries.
> >>>>>    * lib/target-supports.exp (v9a): Add new armflag.
> >>>>>    (__ARM_ARCH_9A__): Add new armdef.
> >>>>>
> >>>>> --
> >>>>> kind regards,
> >>>>> Przemyslaw Wirkus
> >>
> >>
>