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Date:      Tue, 15 Jun 2021 00:15:42 +0200
From:      Dimitry Andric <dim@FreeBSD.org>
To:        Mark Millard <marklmi@yahoo.com>
Cc:        freebsd-current <freebsd-current@freebsd.org>
Subject:   Re: git: 790a6be5a169 - main - Export various 128 bit long double  functions from libgcc_s.so.1
Message-ID:  <D9EDC624-1FB4-4F80-8667-3A47EA63E909@FreeBSD.org>
In-Reply-To: <38C7A31A-CB21-4C3C-98D0-38F91EBC35D3@yahoo.com>
References:  <38C7A31A-CB21-4C3C-98D0-38F91EBC35D3.ref@yahoo.com> <38C7A31A-CB21-4C3C-98D0-38F91EBC35D3@yahoo.com>

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On 14 Jun 2021, at 22:38, Mark Millard <marklmi@yahoo.com> wrote:
>=20
> Dimitry Andric dim at FreeBSD.org wrote on
> Mon Jun 14 19:17:40 UTC 2021 :
>=20
>> The branch main has been updated by dim:
>>=20
>> URL:
>> =
https://cgit.FreeBSD.org/src/commit/?id=3D790a6be5a1699291c6da87871426d0c5=
6dedcc89
>>=20
>>=20
>> commit 790a6be5a1699291c6da87871426d0c56dedcc89
>> Author:     Dimitry Andric <dim at FreeBSD.org>
>> AuthorDate: 2021-06-14 19:17:05 +0000
>> Commit:     Dimitry Andric <dim at FreeBSD.org>
>> CommitDate: 2021-06-14 19:17:05 +0000
>>=20
>>    Export various 128 bit long double functions from libgcc_s.so.1
>>=20
>>    These were already compiled for some time on aarch64 and riscv, by
>>    including lib/libcompiler_rt/Makefile.inc, but never exported in =
the
>>    shared library. Since gcc exports these under version GCC_4.6.0, =
we do
>>    the same.
>>=20
>>    This review should replace D11482 for now. For e.g. amd64 more =
work is
>>    still to be done, as compiler-rt does not seem to support 128 bit =
long
>>    double math for that architecture.
>=20
> Given that "man arch" explicitly reports:
>=20
>           Architecture    void *    long double    time_t
> . . .
>           amd64           8         16             8
> . . .
>=20
> and also:
>=20
>           Architecture    float, double    long double
> . . .
>           amd64           hard             hard, 80 bit
> . . .

Yeah this is a bit confusing, since padding is never mentioned.


> (so there is guaranteed pad involved), would amd64 having 128
> bit long doubles (no pad by default?) be an FreeBSD ABI change,
> possibly needing a discussion on freebsd-arch and
> freebsd-numerics ? (Or may be it happened and I just do not
> remember. Or may be it would take special enabling of the
> alternate ABI's use and not be a default configuration.)
>=20
> (i386 only has "12", not "16", for its "80 bit", so 96 bits:
> less pad.)

There's nothing to worry about, the "tf" variants in this update are
only enabled for aarch64 and riscv; see lib/libcompiler_rt/Makefile.inc:

#
# 128-bit quad precision long double support,
# only used on some architectures.
#
.if ${MACHINE_CPUARCH} =3D=3D "aarch64" || ${MACHINE_CPUARCH} =3D=3D =
"riscv"
SRCF+=3D          addtf3
SRCF+=3D          comparetf2
SRCF+=3D          divtf3
SRCF+=3D          extenddftf2
SRCF+=3D          extendsftf2
SRCF+=3D          fixtfdi
SRCF+=3D          fixtfsi
SRCF+=3D          fixtfti
SRCF+=3D          fixunstfdi
SRCF+=3D          fixunstfsi
SRCF+=3D          fixunstfti
SRCF+=3D          floatsitf
SRCF+=3D          floattitf
SRCF+=3D          floatunsitf
SRCF+=3D          floatuntitf
SRCF+=3D          multf3
SRCF+=3D          subtf3
SRCF+=3D          trunctfdf2
SRCF+=3D          trunctfsf2
.endif

I'm sorry to have sowed confusion here, as the commit message was mostly
copy/pasted from the Phabricator review. Please consider the amd64
sentence to be 'cancelled'. :)

-Dimitry


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