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

[Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>]

Richard Henderson <rth@twiddle.net> 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 <nikunj@linux.vnet.ibm.com>
>> ---
>>  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.

Regards
Nikunj