Re: [PATCH] MATCH: Move `(x | y) & (~x ^ y)` over to use bitwise_inverted_equal_p

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

On Mon, Aug 28, 2023 at 10:15 PM Andrew Pinski via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> This moves the match pattern `(x | y) & (~x ^ y)` over to use bitwise_inverted_equal_p.
> This now also allows to optmize comparisons and also catches the missed `(~x | y) & (x ^ y)`
> transformation into `~x & y`.
>
> OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.

OK

> gcc/ChangeLog:
>
>         PR tree-optmization/111147
>         * match.pd (`(x | y) & (~x ^ y)`) Use bitwise_inverted_equal_p
>         instead of matching bit_not.
>
> gcc/testsuite/ChangeLog:
>
>         PR tree-optmization/111147
>         * gcc.dg/tree-ssa/cmpbit-4.c: New test.
> ---
>  gcc/match.pd                             |  7 +++-
>  gcc/testsuite/gcc.dg/tree-ssa/cmpbit-4.c | 47 ++++++++++++++++++++++++
>  2 files changed, 52 insertions(+), 2 deletions(-)
>  create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/cmpbit-4.c
>
> diff --git a/gcc/match.pd b/gcc/match.pd
> index e6bdc3149b6..47d2733211a 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -1616,8 +1616,11 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
>
>  /* (x | y) & (~x ^ y) -> x & y */
>  (simplify
> - (bit_and:c (bit_ior:c @0 @1) (bit_xor:c @1 (bit_not @0)))
> - (bit_and @0 @1))
> + (bit_and:c (bit_ior:c @0 @1) (bit_xor:c @1 @2))
> + (with { bool wascmp; }
> +  (if (bitwise_inverted_equal_p (@0, @2, wascmp)
> +       && (!wascmp || element_precision (type) == 1))
> +   (bit_and @0 @1))))
>
>  /* (~x | y) & (x | ~y) -> ~(x ^ y) */
>  (simplify
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/cmpbit-4.c b/gcc/testsuite/gcc.dg/tree-ssa/cmpbit-4.c
> new file mode 100644
> index 00000000000..cdba5d623af
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/cmpbit-4.c
> @@ -0,0 +1,47 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-optimized-raw" } */
> +
> +int g(int x, int y)
> +{
> +  int xp = ~x;
> +  return (x | y) & (xp ^ y); // x & y
> +}
> +int g0(int x, int y)
> +{
> +  int xp = ~x;
> +  return (xp | y) & (x ^ y); // ~x & y
> +}
> +
> +_Bool gb(_Bool x, _Bool y)
> +{
> +  _Bool xp = !x;
> +  return (x | y) & (xp ^ y); // x & y
> +}
> +_Bool gb0(_Bool x, _Bool y)
> +{
> +  _Bool xp = !x;
> +  return (xp | y) & (x ^ y); // !x & y
> +}
> +
> +
> +_Bool gbi(int a, int b)
> +{
> +  _Bool x = a < 2;
> +  _Bool y = b < 3;
> +  _Bool xp = !x;
> +  return (x | y) & (xp ^ y); // x & y
> +}
> +_Bool gbi0(int a, int b)
> +{
> +  _Bool x = a < 2;
> +  _Bool y = b < 3;
> +  _Bool xp = !x;
> +  return (xp | y) & (x ^ y); // !x & y
> +}
> +
> +/* All of these should be optimized to `x & y` or `~x & y` */
> +/* { dg-final { scan-tree-dump-times "le_expr, " 3 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times "gt_expr, " 1 "optimized" } } */
> +/* { dg-final { scan-tree-dump-not "bit_xor_expr, " "optimized" } } */
> +/* { dg-final { scan-tree-dump-times "bit_and_expr, " 6 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times "bit_not_expr, " 2 "optimized" } } */
> --
> 2.31.1
>