Re: [PATCH] match.pd: Add bitwise and pattern [PR106243]

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

On Wed, Aug 3, 2022 at 9:11 PM Sam Feifer via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> This patch adds a new optimization to match.pd. The pattern, -x & 1,
> now gets simplified to x & 1, reducing the number of instructions
> produced.
>
> This patch also adds tests for the optimization rule.
>
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
>
>         PR tree-optimization/106243
>
> gcc/ChangeLog:
>
>         * match.pd (-x & 1): New simplification.
>
> gcc/testsuite/ChangeLog:
>
>         * gcc.dg/pr106243-1.c: New test.
>         * gcc.dg/pr106243.c: New test.
> ---
>  gcc/match.pd                      |  5 ++++
>  gcc/testsuite/gcc.dg/pr106243-1.c | 18 +++++++++++++
>  gcc/testsuite/gcc.dg/pr106243.c   | 43 +++++++++++++++++++++++++++++++
>  3 files changed, 66 insertions(+)
>  create mode 100644 gcc/testsuite/gcc.dg/pr106243-1.c
>  create mode 100644 gcc/testsuite/gcc.dg/pr106243.c
>
> diff --git a/gcc/match.pd b/gcc/match.pd
> index 562138a8034..78b32567836 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -8061,3 +8061,8 @@ and,
>        (if (TYPE_UNSIGNED (TREE_TYPE (@0)))
>          (bit_and @0 @1)
>        (cond (le @0 @1) @0 (bit_and @0 @1))))))
> +
> +/* -x & 1 -> x & 1.  */
> +(simplify
> +  (bit_and:c (negate @0) integer_onep@1)

Note the bit_and doesn't need :c because constant operands are always
canonicalized second.

OK with that change.
Thanks,
Richard.

> +  (bit_and @0 @1))
> diff --git a/gcc/testsuite/gcc.dg/pr106243-1.c b/gcc/testsuite/gcc.dg/pr106243-1.c
> new file mode 100644
> index 00000000000..b1dbe5cbe44
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr106243-1.c
> @@ -0,0 +1,18 @@
> +/* PR tree-optimization/106243 */
> +/* { dg-do run } */
> +/* { dg-options "-O2" } */
> +
> +#include "pr106243.c"
> +
> +int main () {
> +
> +    if (foo(3) != 1
> +        || bar(-6) != 0
> +        || baz(17) != 1
> +        || qux(-128) != 0
> +        || foo(127) != 1) {
> +            __builtin_abort();
> +        }
> +
> +    return 0;
> +}
> diff --git a/gcc/testsuite/gcc.dg/pr106243.c b/gcc/testsuite/gcc.dg/pr106243.c
> new file mode 100644
> index 00000000000..ee2706f2bf9
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr106243.c
> @@ -0,0 +1,43 @@
> +/* PR tree-optimization/106243 */
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-optimized" } */
> +
> +#define vector __attribute__((vector_size(4*sizeof(int))))
> +
> +/* Test from PR.  */
> +__attribute__((noipa)) int foo (int x) {
> +    return -x & 1;
> +}
> +
> +/* Other test from PR.  */
> +__attribute__((noipa)) int bar (int x) {
> +    return (0 - x) & 1;
> +}
> +
> +/* Forward propogation.  */
> +__attribute__((noipa)) int baz (int x) {
> +    x = -x;
> +    return x & 1;
> +}
> +
> +/* Commutative property.  */
> +__attribute__((noipa)) int qux (int x) {
> +    return 1 & -x;
> +}
> +
> +/* Vector test case.  */
> +__attribute__((noipa)) vector int waldo (vector int x) {
> +    return -x & 1;
> +}
> +
> +/* Should not simplify.  */
> +__attribute__((noipa)) int thud (int x) {
> +    return -x & 2;
> +}
> +
> +/* Should not simplify.  */
> +__attribute__((noipa)) int corge (int x) {
> +    return -x & -1;
> +}
> +
> +/* { dg-final {scan-tree-dump-times "-" 2 "optimized" } } */
>
> base-commit: 388fbbd895e72669909173c3003ae65c6483a3c2
> --
> 2.31.1
>