arm: Fix vfp_operand_register for VFP HI regs

[Christophe Lyon]

On Fri, 1 May 2020 at 12:57, Kyrylo Tkachov <Kyrylo.Tkachov@arm.com> wrote:
>
>
>
> > -----Original Message-----
> > From: Christophe Lyon <christophe.lyon@linaro.org>
> > Sent: 30 April 2020 09:51
> > To: Kyrylo Tkachov <Kyrylo.Tkachov@arm.com>
> > Cc: gcc-patches@gcc.gnu.org
> > Subject: Re: arm: Fix vfp_operand_register for VFP HI regs
> >
> > On Wed, 29 Apr 2020 at 18:40, Kyrylo Tkachov <Kyrylo.Tkachov@arm.com>
> > wrote:
> > >
> > > Hi Christophe,
> > >
> > > > -----Original Message-----
> > > > From: Gcc-patches <gcc-patches-bounces@gcc.gnu.org> On Behalf Of
> > > > Christophe Lyon via Gcc-patches
> > > > Sent: 29 April 2020 16:53
> > > > To: gcc Patches <gcc-patches@gcc.gnu.org>
> > > > Subject: arm: Fix vfp_operand_register for VFP HI regs
> > > >
> > > > Hi,
> > > >
> > > > While looking at PR target/94743 I noticed an ICE when I tried to save
> > > > all the FP registers: this was because all HI registers wouldn't match
> > > > vfp_register_operand.
> > >
> > > Hmm, I see that arm_regno_class indeed never returns VFP_REGS and
> > would return VFP_HI_REGS here.
> > > So the patch looks correct to me.
> > > Do you have a testcase for the ICE to add to the testsuite?
> > >
> >
> > No C source code: I found that while extending the list of registers
> > pushed in the prologue of an IRQ handler, more-or-less modifying
> > arm_save_coproc_regs so that more registers are handled by
> > vfp_emit_fstmd.
> > The problem occurs when trying to push d16-d31.
>
> I'd be comfortable taking this now for trunk (GCC 11) so it has time to bake.
> Once you're ready to post the IRQ handler work we can see about backporting this fix it to the branch, if we deem it necessary.
> Thanks,
> Kyrill
>

Hi,

I've just sent several patches for PR 94743:
https://gcc.gnu.org/pipermail/gcc-patches/2020-May/545747.html
is v2 of my previous patch: it only emits a warning, and might be
sufficient to close the PR, if we decide that
we don't want to save the FP registers without explicit user request...

Then,
[1] https://gcc.gnu.org/pipermail/gcc-patches/2020-May/545748.html
[2] https://gcc.gnu.org/pipermail/gcc-patches/2020-May/545749.html
are refactorization patches that would make implementing the patch
attached here easier.

If you apply the attached on top of [1] and [2], you'll notice an ICE
fixed by the original patch of this thread.

So hopefully applying [1], [2] and the attached should help convince you that
the vfp_operand_register is OK.

Thanks

> >
> >
> > > Thanks,
> > > Kyrill
> > >
> > > >
> > > > Regression-tested and bootstrapped OK.
> > > >
> > > > 2020-04-29  Christophe Lyon  <christophe.lyon@linaro.org>
> > > >
> > > >         gcc/
> > > >         * config/arm/predicates.md (vfp_register_operand): Use
> > VFP_HI_REGS
> > > >         instead of VFP_REGS.
> > > >
> > > > OK?
> > > >
> > > > Thanks,
> > > >
> > > > Christophe
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