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

[Philippe Mathieu-Daudé]

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.