Re: Ping: [PATCH v2] RISC-V: correct FCVT.Q.L[U]

[Andrew Waterman <andrew@sifive.com>]

Approved.  The old mapping is harmless, but the new mapping honors the
recommendation in the ISA spec for instructions that don't round.
I'll also add the corresponding note in the ISA spec for these
instructions.

On Mon, Mar 28, 2022 at 1:52 AM Jan Beulich <jbeulich@suse.com> wrote:
>
> On 04.03.2022 13:41, Jan Beulich via Binutils wrote:
> > While the spec isn't explicit about this, it pointing out the similarity
> > with the D extension ought to extend to the ignoring of a meaningless
> > rounding mode: "Note FCVT.D.W[U] always produces an exact result and is
> > unaffected by rounding mode." Hence the chosen encodings also ought to
> > match.
> >
> > Note that to avoid breaking existing code the forms with a 3rd operand
> > are not removed, which means there continues to be a difference to
> > FCVT.D.W[U].
>
> I'd prefer to not commit such without arch maintainer approval; I guess
> I'll give it another week and the will assume the absence of comments to
> mean consent.
>
> Thanks, Jan
>
> > ---
> > Oddly enough there's looks to be no testing of the Q (or D/F) extension
> > beyond what was recently added for Zqinx (Zdinx/Zfinx).
> > ---
> > v2: Re-base.
> >
> > --- a/gas/testsuite/gas/riscv/zqinx.d
> > +++ b/gas/testsuite/gas/riscv/zqinx.d
> > @@ -28,8 +28,8 @@ Disassembly of section .text:
> >  [    ]+[0-9a-f]+:[   ]+46158553[     ]+fcvt.q.d[     ]+a0,a1
> >  [    ]+[0-9a-f]+:[   ]+d6058553[     ]+fcvt.q.w[     ]+a0,a1
> >  [    ]+[0-9a-f]+:[   ]+d6158553[     ]+fcvt.q.wu[    ]+a0,a1
> > -[    ]+[0-9a-f]+:[   ]+d625f553[     ]+fcvt.q.l[     ]+a0,a1
> > -[    ]+[0-9a-f]+:[   ]+d635f553[     ]+fcvt.q.lu[    ]+a0,a1
> > +[    ]+[0-9a-f]+:[   ]+d6258553[     ]+fcvt.q.l[     ]+a0,a1
> > +[    ]+[0-9a-f]+:[   ]+d6358553[     ]+fcvt.q.lu[    ]+a0,a1
> >  [    ]+[0-9a-f]+:[   ]+26c58553[     ]+fsgnj.q[      ]+a0,a1,a2
> >  [    ]+[0-9a-f]+:[   ]+26c59553[     ]+fsgnjn.q[     ]+a0,a1,a2
> >  [    ]+[0-9a-f]+:[   ]+26c5a553[     ]+fsgnjx.q[     ]+a0,a1,a2
> > --- a/opcodes/riscv-opc.c
> > +++ b/opcodes/riscv-opc.c
> > @@ -763,9 +763,9 @@ const struct riscv_opcode riscv_opcodes[
> >  {"fcvt.l.q",  64, INSN_CLASS_Q_OR_ZQINX,   "d,S,m",     MATCH_FCVT_L_Q, MASK_FCVT_L_Q, match_opcode, 0 },
> >  {"fcvt.lu.q", 64, INSN_CLASS_Q_OR_ZQINX,   "d,S",       MATCH_FCVT_LU_Q|MASK_RM, MASK_FCVT_LU_Q|MASK_RM, match_opcode, 0 },
> >  {"fcvt.lu.q", 64, INSN_CLASS_Q_OR_ZQINX,   "d,S,m",     MATCH_FCVT_LU_Q, MASK_FCVT_LU_Q, match_opcode, 0 },
> > -{"fcvt.q.l",  64, INSN_CLASS_Q_OR_ZQINX,   "D,s",       MATCH_FCVT_Q_L|MASK_RM, MASK_FCVT_Q_L|MASK_RM, match_opcode, 0 },
> > +{"fcvt.q.l",  64, INSN_CLASS_Q_OR_ZQINX,   "D,s",       MATCH_FCVT_Q_L, MASK_FCVT_Q_L|MASK_RM, match_opcode, 0 },
> >  {"fcvt.q.l",  64, INSN_CLASS_Q_OR_ZQINX,   "D,s,m",     MATCH_FCVT_Q_L, MASK_FCVT_Q_L, match_opcode, 0 },
> > -{"fcvt.q.lu", 64, INSN_CLASS_Q_OR_ZQINX,   "D,s",       MATCH_FCVT_Q_LU|MASK_RM, MASK_FCVT_Q_LU|MASK_RM, match_opcode, 0 },
> > +{"fcvt.q.lu", 64, INSN_CLASS_Q_OR_ZQINX,   "D,s",       MATCH_FCVT_Q_LU, MASK_FCVT_Q_LU|MASK_RM, match_opcode, 0 },
> >  {"fcvt.q.lu", 64, INSN_CLASS_Q_OR_ZQINX,   "D,s,m",     MATCH_FCVT_Q_LU, MASK_FCVT_Q_LU, match_opcode, 0 },
> >
> >  /* Compressed instructions.  */
> >
>