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

[Philippe Mathieu-Daudé]

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?

-- >8 --
@@ -643,6 +643,7 @@ static void tcg_out_movext3(TCGContext *s, const 
TCGMovExtend *i1,
 #define C_O1_I4(O1, I1, I2, I3, I4)     C_PFX5(c_o1_i4_, O1, I1, I2, 
I3, I4),

 #define C_N1_I2(O1, I1, I2)             C_PFX3(c_n1_i2_, O1, I1, I2),
+#define C_N1_O1_I4(O1, I1, I2, I3, I4)  C_PFX5(c_n1_o1_i4_, O1, I1, I2, 
I3, I4),

 #define C_O2_I1(O1, O2, I1)             C_PFX3(c_o2_i1_, O1, O2, I1),
 #define C_O2_I2(O1, O2, I1, I2)         C_PFX4(c_o2_i2_, O1, O2, I1, I2),
---

Thanks,

Phil.