Re: [PATCH v2 06/14] tcg/{i386, s390x}: Add earlyclobber to the op_add2's first output

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 19/7/23 14:30, Ilya Leoshkevich wrote:
> On Wed, 2023-07-19 at 14:08 +0200, Philippe Mathieu-Daudé wrote:
>> Hi Ilya,
>>
>> On 19/7/23 11:44, Ilya Leoshkevich wrote:
>>> i386 and s390x implementations of op_add2 require an earlyclobber,
>>> which is currently missing. This breaks VCKSM in s390x guests.
>>> E.g., on
>>> x86_64 the following op:
>>>
>>>       add2_i32 tmp2,tmp3,tmp2,tmp3,tmp3,tmp2   dead: 0 2 3 4 5
>>> pref=none,0xffff
>>>
>>> is translated to:
>>>
>>>       addl     %ebx, %r12d
>>>       adcl     %r12d, %ebx
>>>
>>> Introduce a new C_N1_O1_I4 constraint, and make sure that
>>> earlyclobber
>>> of aliased outputs is honored.
>>>
>>> Cc: qemu-stable@nongnu.org
>>> Fixes: 82790a870992 ("tcg: Add markup for output requires new
>>> register")
>>> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
>>> ---
>>>    tcg/i386/tcg-target-con-set.h  | 2 +-
>>>    tcg/i386/tcg-target.c.inc      | 2 +-
>>>    tcg/s390x/tcg-target-con-set.h | 5 ++---
>>>    tcg/s390x/tcg-target.c.inc     | 4 ++--
>>>    tcg/tcg.c                      | 8 +++++++-
>>>    5 files changed, 13 insertions(+), 8 deletions(-)
>>
>>
>>> diff --git a/tcg/tcg.c b/tcg/tcg.c
>>> index 652e8ea6b93..ddfe9a96cb7 100644
>>> --- a/tcg/tcg.c
>>> +++ b/tcg/tcg.c
>>> @@ -648,6 +648,7 @@ static void tcg_out_movext3(TCGContext *s,
>>> const TCGMovExtend *i1,
>>>    #define C_O2_I2(O1, O2, I1, I2)         C_PFX4(c_o2_i2_, O1, O2,
>>> I1, I2),
>>>    #define C_O2_I3(O1, O2, I1, I2, I3)     C_PFX5(c_o2_i3_, O1, O2,
>>> I1, I2, I3),
>>>    #define C_O2_I4(O1, O2, I1, I2, I3, I4) C_PFX6(c_o2_i4_, O1, O2,
>>> I1, I2, I3, I4),
>>> +#define C_N1_O1_I4(O1, O2, I1, I2, I3, I4) C_PFX6(c_n1_o1_i4_, O1,
>>> O2, I1, I2, I3, I4),
>>
>> No need for O2. Also can you place it earlier just after C_N1_I2?
> 
> Shouldn't it still be a 6-argument constraint?
> INDEX_op_add2_i32 and friends take 6 arguments after all.

Oops sorry, you are right.