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From: Ramana Radhakrishnan <ramana.gcc@googlemail.com>
Date: Thu, 10 Nov 2022 19:46:29 +0000
Message-ID: <CAJA7tRbpaQGt6D_=oF+VA_uuJMPgkLf6OmvCUJNJEp-TsSWLZg@mail.gmail.com>
Subject: Re: [Patch Arm] Fix PR 92999
To: Richard Earnshaw <Richard.Earnshaw@foss.arm.com>
Cc: gcc-patches <gcc-patches@gcc.gnu.org>, Richard Earnshaw <Richard.Earnshaw@arm.com>, 
	Alex Coplan <alex.coplan@arm.com>
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On Thu, Nov 10, 2022 at 6:03 PM Richard Earnshaw
<Richard.Earnshaw@foss.arm.com> wrote:
>
>
>
> On 10/11/2022 17:21, Richard Earnshaw via Gcc-patches wrote:
> >
> >
> > On 08/11/2022 18:20, Ramana Radhakrishnan via Gcc-patches wrote:
> >> PR92999 is a case where the VFP calling convention does not allocate
> >> enough FP registers for a homogenous aggregate containing FP16 values.
> >> I believe this is the complete fix but would appreciate another set of
> >> eyes on this.
> >>
> >> Could I get a hand with a regression test run on an armhf environment
> >> while I fix my environment ?
> >>
> >> gcc/ChangeLog:
> >>
> >> PR target/92999
> >> *  config/arm/arm.c (aapcs_vfp_allocate_return_reg): Adjust to handle
> >> aggregates with elements smaller than SFmode.
> >>
> >> gcc/testsuite/ChangeLog:
> >>
> >> * gcc.target/arm/pr92999.c: New test.
> >>
> >>
> >> Thanks,
> >> Ramana
> >>
> >> Signed-off-by: Ramana Radhakrishnan <ramana.gcc@gmail.com>
> >
> > I'm not sure about this.  The AAPCS does not mention a base type of a
> > half-precision FP type as an appropriate homogeneous aggregate for using
> > VFP registers for either calling or returning.

Ooh interesting, thanks for taking a look and poking at the AAPCS and
that's a good catch. BF16 should also have the same behaviour as FP16
, I suspect ?

> >
> > So perhaps the bug is that we try to treat this as a homogeneous
> > aggregate at all.

Yep I agree - I'll take a look again tomorrow and see if I can get a fix.

(And thanks Alex for the test run, I might trouble you again while I
still (slowly) get some of my boards back up)

regards,
Ramana


>
> R.