On Sat, Nov 5, 2022 at 12:44 PM Richard Biener
<[email protected]> wrote:
>
> On Wed, Nov 2, 2022 at 10:47 PM apinski--- via Gcc-patches
> <[email protected]> wrote:
> >
> > From: Andrew Pinski <[email protected]>
> >
> > 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
> >
