On Wed, Nov 2, 2022 at 10:47 PM apinski--- via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> From: Andrew Pinski <apin...@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.
> 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
>
