Re: [PATCH 1/2] Fix PR 105532: match.pd patterns calling tree_nonzero_bits with vector types

[Richard Biener <richard.guenther@gmail.com>]

On Sat, Nov 5, 2022 at 12:44 PM Richard Biener
<richard.guenther@gmail.com> wrote:
>
> On Wed, Nov 2, 2022 at 10:47 PM apinski--- via Gcc-patches
> <gcc-patches@gcc.gnu.org> wrote:
> >
> > From: Andrew Pinski <apinski@marvell.com>
> >
> > Even though this PR was reported with an ubsan issue, the problem is
> > tree_nonzero_bits is being called with an expression which is a vector type.
>
> It seems to me the semantics
> for vectors should be clear but the users didn't expect that result?
>
> > This fixes three patterns I noticed which does that.
> > And adds a testcase for one of the patterns.
> >
> > OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions
>
> OK.

You didn't push this yet?

> > gcc/ChangeLog:
> >
> >         PR tree-optimization/105532
> >         * match.pd (~(X >> Y) -> ~X >> Y): Check if it is an integral
> >         type before calling tree_nonzero_bits.
> >         (popcount(X) + popcount(Y)): Likewise.
> >         (popcount(X&C1)): Likewise.
> >
> > gcc/testsuite/ChangeLog:
> >
> >         * gcc.c-torture/compile/vector-shift-1.c: New test.
> > ---
> >  gcc/match.pd                                  | 25 +++++++++++--------
> >  .../gcc.c-torture/compile/vector-shift-1.c    |  8 ++++++
> >  2 files changed, 22 insertions(+), 11 deletions(-)
> >  create mode 100644 gcc/testsuite/gcc.c-torture/compile/vector-shift-1.c
> >
> > diff --git a/gcc/match.pd b/gcc/match.pd
> > index 194ba8f5188..5833e05a926 100644
> > --- a/gcc/match.pd
> > +++ b/gcc/match.pd
> > @@ -1371,7 +1371,8 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> >     /* For logical right shifts, this is possible only if @0 doesn't
> >        have MSB set and the logical right shift is changed into
> >        arithmetic shift.  */
> > -   (if (!wi::neg_p (tree_nonzero_bits (@0)))
> > +   (if (INTEGRAL_TYPE_P (type)
> > +        && !wi::neg_p (tree_nonzero_bits (@0)))
> >      (with { tree stype = signed_type_for (TREE_TYPE (@0)); }
> >       (convert (rshift (bit_not! (convert:stype @0)) @1))))))
> >
> > @@ -7518,7 +7519,8 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> >  /* popcount(X) + popcount(Y) is popcount(X|Y) when X&Y must be zero.  */
> >  (simplify
> >    (plus (POPCOUNT:s @0) (POPCOUNT:s @1))
> > -  (if (wi::bit_and (tree_nonzero_bits (@0), tree_nonzero_bits (@1)) == 0)
> > +  (if (INTEGRAL_TYPE_P (type)
> > +       && wi::bit_and (tree_nonzero_bits (@0), tree_nonzero_bits (@1)) == 0)
> >      (POPCOUNT (bit_ior @0 @1))))
> >
> >  /* popcount(X) == 0 is X == 0, and related (in)equalities.  */
> > @@ -7550,15 +7552,16 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> >  (for pfun (POPCOUNT PARITY)
> >    (simplify
> >      (pfun @0)
> > -    (with { wide_int nz = tree_nonzero_bits (@0); }
> > -      (switch
> > -       (if (nz == 1)
> > -         (convert @0))
> > -       (if (wi::popcount (nz) == 1)
> > -         (with { tree utype = unsigned_type_for (TREE_TYPE (@0)); }
> > -           (convert (rshift:utype (convert:utype @0)
> > -                                  { build_int_cst (integer_type_node,
> > -                                                   wi::ctz (nz)); }))))))))
> > +    (if (INTEGRAL_TYPE_P (type))
> > +     (with { wide_int nz = tree_nonzero_bits (@0); }
> > +       (switch
> > +        (if (nz == 1)
> > +          (convert @0))
> > +        (if (wi::popcount (nz) == 1)
> > +          (with { tree utype = unsigned_type_for (TREE_TYPE (@0)); }
> > +            (convert (rshift:utype (convert:utype @0)
> > +                                   { build_int_cst (integer_type_node,
> > +                                                    wi::ctz (nz)); })))))))))
> >
> >  #if GIMPLE
> >  /* 64- and 32-bits branchless implementations of popcount are detected:
> > diff --git a/gcc/testsuite/gcc.c-torture/compile/vector-shift-1.c b/gcc/testsuite/gcc.c-torture/compile/vector-shift-1.c
> > new file mode 100644
> > index 00000000000..142ea56d5bb
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.c-torture/compile/vector-shift-1.c
> > @@ -0,0 +1,8 @@
> > +typedef unsigned char __attribute__((__vector_size__ (1))) U;
> > +
> > +U
> > +foo (U u)
> > +{
> > +  u = u == u;
> > +  return (~(u >> 255));
> > +}
> > --
> > 2.17.1
> >