Re: [PATCH] target/ppc: Fix rlwinm on ppc64

[Vitaly Chikunov]

David,

On Wed, Mar 11, 2020 at 10:15:03AM +1100, David Gibson wrote:
> On Mon, Mar 09, 2020 at 11:45:57PM +0300, Vitaly Chikunov wrote:
> > rlwinm cannot just AND with Mask if shift value is zero on ppc64 when
> > Mask Begin is greater than Mask End and high bits are set to 1.
> > 
> > Note that PowerISA 3.0B says that for `rlwinm' ROTL32 is used, and
> > ROTL32 is defined (in 3.3.14) so that rotated value should have two
> > copies of lower word of the source value.
> > 
> > This seems to be another incarnation of the fix from 820724d170
> > ("target-ppc: Fix rlwimi, rlwinm, rlwnm again"), except I leave
> > optimization when Mask value is less than 32 bits.
> > 
> > Fixes: 7b4d326f47 ("target-ppc: Use the new deposit and extract ops")
> > Cc: address@hidden
> > Signed-off-by: Vitaly Chikunov <address@hidden>
> 
> Applied to ppc-for-5.0.

Thanks! FYI, there is at least one real case of this bug:
  https://github.com/iovisor/bcc/issues/2771
so this is not theoretical, and, probably, should go to the stable
too.

Thanks,


> 
> > ---
> >  target/ppc/translate.c | 20 +++++++++++---------
> >  1 file changed, 11 insertions(+), 9 deletions(-)
> > 
> > diff --git a/target/ppc/translate.c b/target/ppc/translate.c
> > index 36fa27367c..127c82a24e 100644
> > --- a/target/ppc/translate.c
> > +++ b/target/ppc/translate.c
> > @@ -1938,15 +1938,17 @@ static void gen_rlwinm(DisasContext *ctx)
> >          me += 32;
> >  #endif
> >          mask = MASK(mb, me);
> > -        if (sh == 0) {
> > -            tcg_gen_andi_tl(t_ra, t_rs, mask);
> > -        } else if (mask <= 0xffffffffu) {
> > -            TCGv_i32 t0 = tcg_temp_new_i32();
> > -            tcg_gen_trunc_tl_i32(t0, t_rs);
> > -            tcg_gen_rotli_i32(t0, t0, sh);
> > -            tcg_gen_andi_i32(t0, t0, mask);
> > -            tcg_gen_extu_i32_tl(t_ra, t0);
> > -            tcg_temp_free_i32(t0);
> > +        if (mask <= 0xffffffffu) {
> > +            if (sh == 0) {
> > +                tcg_gen_andi_tl(t_ra, t_rs, mask);
> > +            } else {
> > +                TCGv_i32 t0 = tcg_temp_new_i32();
> > +                tcg_gen_trunc_tl_i32(t0, t_rs);
> > +                tcg_gen_rotli_i32(t0, t0, sh);
> > +                tcg_gen_andi_i32(t0, t0, mask);
> > +                tcg_gen_extu_i32_tl(t_ra, t0);
> > +                tcg_temp_free_i32(t0);
> > +            }
> >          } else {
> >  #if defined(TARGET_PPC64)
> >              tcg_gen_deposit_i64(t_ra, t_rs, t_rs, 32, 32);
> 
> -- 
> David Gibson                  | I'll have my music baroque, and my code
> david AT gibson.dropbear.id.au        | minimalist, thank you.  NOT _the_ 
> _other_
>                               | _way_ _around_!
> http://www.ozlabs.org/~dgibson