Re: [Qemu-devel] [PATCH v2 08/11] target/ppc: update ov/ov32 for nego

[Richard Henderson]

On 02/22/2017 10:03 PM, Nikunj A Dadhania wrote:
> Richard Henderson <address@hidden> writes:
>
> > On 02/22/2017 08:29 PM, Nikunj A Dadhania wrote:
> > > For 64-bit mode if the register RA contains 0x8000_0000_0000_0000, OV
> > > and OV32 are set to 1.
> > >
> > > For 32-bit mode if the register RA contains 0x8000_0000, OV and OV32 are
> > > set to 1.
> > >
> > > Use the tcg-ops for negation (neg_tl) and drop gen_op_arith_neg() as
> > > nego was the last user.
> > >
> > > Signed-off-by: Nikunj A Dadhania <address@hidden>
> > > ---
> > >  target/ppc/translate.c | 26 +++++++++++++++++---------
> > >  1 file changed, 17 insertions(+), 9 deletions(-)
> > >
> > > diff --git a/target/ppc/translate.c b/target/ppc/translate.c
> > > index eecdfe9..2a9f508 100644
> > > --- a/target/ppc/translate.c
> > > +++ b/target/ppc/translate.c
> > > @@ -1473,14 +1473,6 @@ static void gen_subfic(DisasContext *ctx)
> > >  }
> > >
> > >  /* neg neg. nego nego. */
> > > -static inline void gen_op_arith_neg(DisasContext *ctx, bool compute_ov)
> > > -{
> > > -    TCGv zero = tcg_const_tl(0);
> > > -    gen_op_arith_subf(ctx, cpu_gpr[rD(ctx->opcode)], cpu_gpr[rA(ctx->opcode)],
> > > -                      zero, 0, 0, compute_ov, Rc(ctx->opcode));
> > > -    tcg_temp_free(zero);
> > > -}
> > > -
> > >  static void gen_neg(DisasContext *ctx)
> > >  {
> > >      tcg_gen_neg_tl(cpu_gpr[rD(ctx->opcode)], cpu_gpr[rA(ctx->opcode)]);
> > > @@ -1491,7 +1483,23 @@ static void gen_neg(DisasContext *ctx)
> > >
> > >  static void gen_nego(DisasContext *ctx)
> > >  {
> > > -    gen_op_arith_neg(ctx, 1);
> > > +    TCGv t0 = tcg_temp_new();
> > > +    TCGv zero = tcg_const_tl(0);
> > > +
> > > +    if (NARROW_MODE(ctx)) {
> > > +        tcg_gen_xori_tl(t0, cpu_gpr[rA(ctx->opcode)], INT32_MIN);
> > > +    } else {
> > > +        tcg_gen_xori_tl(t0, cpu_gpr[rA(ctx->opcode)], (target_ulong)INT64_MIN);
> > > +    }
> > > +
> > > +    tcg_gen_setcond_tl(TCG_COND_EQ, cpu_ov, t0, zero);
> > > +    tcg_gen_mov_tl(cpu_ov32, cpu_ov);
> >
> > I think we just now covered this is wrong in the v1 thread.
>
> With respect to the simulator, right?
>
> I will restore the same neg/nego behaviour using subf, as OV/OV32 will
> be updated as per the simulator.

Yes.  It's the only solution that makes sense to me.


r~