[Bug target/112707] [14 regression] gcc 14 outputs invalid assembly on ppc: Error: unrecognized opcode: `fctid'

["linkw at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112707

--- 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?
> > 
> > We really should have a TARGET_FCTID, on for TARGET_POWERPC64 or for cpu 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.
> > 
> > So either a separate OPTION_FCTID for in rs6000-cpus.def, or TARGET_FCTID. 
> > Either
> > works for me.
> > 
> > (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 was
> > implemented
> > on the 476).
> 
> Thanks for your explanation.
> 
> I found "fctid" is supported on PPC64 and PPC476 from assembler source code.
> {“fctid”,       XRC(63,814,0),  XRA_MASK,    PPC64,     PPCVLE,        
> {FRT, FRB}},
> {“fctid”,       XRC(63,814,0),  XRA_MASK,    PPC476,    PPCVLE,        
> {FRT, FRB}},
> 
> But powerpc7450 only enables PPC. That's why assembler complains.
>   { "7450",    PPC_OPCODE_PPC | PPC_OPCODE_7450 | PPC_OPCODE_ALTIVEC, 0 },
> 
> My question is: can "fctid" be executed on powerpc7450 such a 32bit
> processor? If it's supported, should the assembler be changed also (replace
> 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