Re: [Qemu-devel] [PATCH 01/10] target-s390: Move facilities bits to env

[Richard Henderson]

On 10/01/2013 08:48 AM, Alexander Graf wrote:
> On 09/30/2013 09:15 PM, Richard Henderson wrote:
>> On 09/30/2013 11:03 AM, Alexander Graf wrote:
>>> On 09/23/2013 04:04 PM, Richard Henderson wrote:
>>>> Rather than simply hard-coding them in STFL instruction.
>>>>
>>>> Signed-off-by: Richard Henderson<address@hidden>
>>>> ---
>>>>    target-s390x/cpu.c       |  3 +++
>>>>    target-s390x/cpu.h       |  1 +
>>>>    target-s390x/translate.c | 10 +++++-----
>>>>    3 files changed, 9 insertions(+), 5 deletions(-)
>>>>
>>>> diff --git a/target-s390x/cpu.c b/target-s390x/cpu.c
>>>> index 3c89f8a..ff691df 100644
>>>> --- a/target-s390x/cpu.c
>>>> +++ b/target-s390x/cpu.c
>>>> @@ -181,6 +181,9 @@ static void s390_cpu_initfn(Object *obj)
>>>>        env->cpu_num = cpu_num++;
>>>>        env->ext_index = -1;
>>>>
>>>> +    env->facilities[0] = 0xc000000000000000ull;
>>>> +    env->facilities[1] = 0;
>>> Could we add CPU definitions along the way here? I'm fine with making z9 the
>>> default CPU type, but we should make this explicit :).
>> Certainly that's what we should do.  I just hadn't yet researched the
>> currently correct way to do that.  I know there's some amount of out-of-date
>> examples in the current source base.
> 
> I'll leave the answer to that to Andreas :).

Can we leave that for a separate patch series then?

>>>> -    TCGv_i64 f, a;
>>>> -    /* We really ought to have more complete indication of facilities
>>>> -       that we implement.  Address this when STFLE is implemented.  */
>>>> +    TCGv_i64 f = tcg_temp_new_i64();
>>>> +    TCGv_i64 a = tcg_const_i64(200);
>>>> +
>>>>        check_privileged(s);
>>>> -    f = tcg_const_i64(0xc0000000);
>>>> -    a = tcg_const_i64(200);
>>>> +    tcg_gen_ld_i64(f, cpu_env, offsetof(CPUS390XState, facilities[0]));
>>>> +    tcg_gen_shri_i64(f, f, 32);
>>> IMHO the facility list should be stored in DisasContext. That way we can 
>>> check
>>> whether we're generating code against the correct target.
>> See patch 4.
>>
>> As for the code we generate here, does it really matter if we load the value
>> from env, or have it encoded as a constant?  It still has to get stored to
>> memory, so it's not like the TCG optimizer is going to do anything with the
>> constant.
> 
> No, it only seemed more straight forward to me from a "single source of
> information" point of view. But it really doesn't matter. Shifting in C seems
> to be easier to read :).

Fair enough.  I'll rearrange the order of the patches so that we can
update STFL to use the DisasContext data.


r~