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

[David Gibson <david@gibson.dropbear.id.au>]

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On Wed, Mar 11, 2020 at 04:00:22PM +0300, Vitaly Chikunov wrote:
> 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: qemu-stable@nongnu.org
> > > Signed-off-by: Vitaly Chikunov <vt@altlinux.org>
> > 
> > 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.

Adding CC to Mike Roth who looks after the stable branch.

Can you include this one, please.

> 
> 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

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