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From: "linkw at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/112707] [14 regression] gcc 14 outputs invalid assembly
 on ppc: Error: unrecognized opcode: `fctid'
Date: Tue, 28 Nov 2023 02:26:13 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D112707

--- Comment #10 from Kewen Lin <linkw at gcc dot gnu.org> ---
(In reply to HaoChen Gui from comment #9)
> (In reply to Segher Boessenkool from comment #8)
> > Yeah, it tested for ISA 2.04 before.  That was an attempt at including =
476
> > probably?
> >=20
> > We really should have a TARGET_FCTID, on for TARGET_POWERPC64 or for cp=
u 476
> > (so
> > NOT user-selectable separately, of course!); not try to use pre-existing
> > flags for this, which might work but will forever stay confusing.
> >=20
> > So either a separate OPTION_FCTID for in rs6000-cpus.def, or TARGET_FCT=
ID.=20
> > Either
> > works for me.
> >=20
> > (Background: in ISA 1.xx it was for 64-bit implementations only.  But it
> > does not
> > need 64-bit registers or a 64-bit integer pipeline at all, it is an FP
> > instruction
> > that works on FP registers, which always are 64-bit.  The instruction w=
as
> > implemented
> > on the 476).
>=20
> Thanks for your explanation.
>=20
> I found "fctid" is supported on PPC64 and PPC476 from assembler source co=
de.
> {=E2=80=9Cfctid=E2=80=9D,       XRC(63,814,0),  XRA_MASK,    PPC64,     P=
PCVLE,=20=20=20=20=20=20=20=20
> {FRT, FRB}},
> {=E2=80=9Cfctid=E2=80=9D,       XRC(63,814,0),  XRA_MASK,    PPC476,    P=
PCVLE,=20=20=20=20=20=20=20=20
> {FRT, FRB}},
>=20
> But powerpc7450 only enables PPC. That's why assembler complains.
>   { "7450",    PPC_OPCODE_PPC | PPC_OPCODE_7450 | PPC_OPCODE_ALTIVEC, 0 },
>=20
> My question is: can "fctid" be executed on powerpc7450 such a 32bit
> processor? If it's supported, should the assembler be changed also (repla=
ce
> the PPC64 with PPC for fctid)?

Good question, I think it's no, the assembler implementation looks to match=
 the
documentation, as I can't find insn fctid in powerpc7450 doc:
https://www.nxp.com.cn/docs/en/reference-manual/MPC7450UM.pdf=