On Wed, Jul 13, 2022 at 12:26 PM Sam Feifer via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> This patch is intended to fix a missed optimization in match.pd. It optimizes
> (x >= 0 ? x : 0) + (x <= 0 ? -x : 0) to just abs(x). I had to write a second
> simplification in match.pd to handle the commutative property as the match
> was not ocurring otherwise. Additionally, the pattern (x <= 0 ? -x : 0) now
> gets optimized to max(-x, 0), which helps with the other simplification rule.
You could use :c for the commutative property instead and that should
simplify things.
That is:
(simplify
(plus:c (max @0 integer_zerop) (max (negate @0) integer_zerop))
(abs @0))
Also since integer_zerop works on vectors, it seems like you should
add a testcase or two for the vector case.
Also would be useful if you write a testcase that uses different
statements rather than one big one so it gets exercised in the
forwprop case.
Note also if either of the max are used more than just in this
simplification, it could increase the lifetime of @0, maybe you need
to add :s to the max expressions.
Thanks,
Andrew
>
> Tests are also included to be added to the testsuite.
>
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
>
> PR tree-optimization/94290
>
> gcc/ChangeLog:
>
> * match.pd (x >= 0 ? x : 0) + (x <= 0 ? -x : 0): New simplification.
> * match.pd (x <= 0 ? -x : 0): New Simplification.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.c-torture/execute/pr94290-1.c: New test.
> * gcc.dg/pr94290-2.c: New test.
> * gcc.dg/pr94290.c: New test.
> ---
> gcc/match.pd | 15 ++++++
> .../gcc.c-torture/execute/pr94290-1.c | 16 +++++++
> gcc/testsuite/gcc.dg/pr94290-2.c | 15 ++++++
> gcc/testsuite/gcc.dg/pr94290.c | 46 +++++++++++++++++++
> 4 files changed, 92 insertions(+)
> create mode 100644 gcc/testsuite/gcc.c-torture/execute/pr94290-1.c
> create mode 100644 gcc/testsuite/gcc.dg/pr94290-2.c
> create mode 100644 gcc/testsuite/gcc.dg/pr94290.c
>
> diff --git a/gcc/match.pd b/gcc/match.pd
> index 45aefd96688..55ca79d7ac9 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -7848,3 +7848,18 @@ and,
> (if (TYPE_UNSIGNED (TREE_TYPE (@0)))
> (bit_and @0 @1)
> (cond (le @0 @1) @0 (bit_and @0 @1))))))
> +
> +/* (x >= 0 ? x : 0) + (x <= 0 ? -x : 0) -> abs x. */
> +(simplify
> + (plus (max @0 integer_zerop) (max (negate @0) integer_zerop))
> + (abs @0))
> +
> +/* (x <= 0 ? -x : 0) + (x >= 0 ? x : 0) -> abs x. */
> +(simplify
> + (plus (max (negate @0) integer_zerop) (max @0 integer_zerop) )
> + (abs @0))
> +
> +/* (x <= 0 ? -x : 0) -> max(-x, 0). */
> +(simplify
> + (cond (le @0 integer_zerop@1) (negate @0) integer_zerop@1)
> + (max (negate @0) @1))
> diff --git a/gcc/testsuite/gcc.c-torture/execute/pr94290-1.c
> b/gcc/testsuite/gcc.c-torture/execute/pr94290-1.c
> new file mode 100644
> index 00000000000..93b80d569aa
> --- /dev/null
> +++ b/gcc/testsuite/gcc.c-torture/execute/pr94290-1.c
> @@ -0,0 +1,16 @@
> +/* PR tree-optimization/94290 */
> +
> +#include "../../gcc.dg/pr94290.c"
> +
> +int main() {
> +
> + if (foo(0) != 0
> + || foo(-42) != 42
> + || foo(42) != 42
> + || baz(-10) != 10
> + || baz(-10) != 10) {
> + __builtin_abort();
> + }
> +
> + return 0;
> +}
> diff --git a/gcc/testsuite/gcc.dg/pr94290-2.c
> b/gcc/testsuite/gcc.dg/pr94290-2.c
> new file mode 100644
> index 00000000000..ea6e55755f5
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr94290-2.c
> @@ -0,0 +1,15 @@
> +/* PR tree-optimization/94290 */
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-optimized" } */
> +
> +/* Form from PR. */
> +__attribute__((noipa)) unsigned int foo(int x) {
> + return x <= 0 ? -x : 0;
> +}
> +
> +/* Changed order. */
> +__attribute__((noipa)) unsigned int bar(int x) {
> + return 0 >= x ? -x : 0;
> +}
> +
> +/* { dg-final {scan-tree-dump-times " MAX_EXPR " 2 "optimized" } } */
> diff --git a/gcc/testsuite/gcc.dg/pr94290.c b/gcc/testsuite/gcc.dg/pr94290.c
> new file mode 100644
> index 00000000000..47617c36c02
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr94290.c
> @@ -0,0 +1,46 @@
> +/* PR tree-optimization/94290 */
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-optimized" } */
> +
> +
> +/* Same form as PR. */
> +__attribute__((noipa)) unsigned int foo(int x) {
> + return (x >= 0 ? x : 0) + (x <= 0 ? -x : 0);
> +}
> +
> +/* Signed function. */
> +__attribute__((noipa)) int bar(int x) {
> + return (x >= 0 ? x : 0) + (x <= 0 ? -x : 0);
> +}
> +
> +/* Commutative property. */
> +__attribute__((noipa)) unsigned int baz(int x) {
> + return (x <= 0 ? -x : 0) + (x >= 0 ? x : 0);
> +}
> +
> +/* Flipped order for max expressions. */
> +__attribute__((noipa)) unsigned int quux(int x) {
> + return (0 <= x ? x : 0) + (0 >= x ? -x : 0);
> +}
> +
> +/* Not zero so should not optimize. */
> +__attribute__((noipa)) unsigned int waldo(int x) {
> + return (x >= 4 ? x : 4) + (x <= 4 ? -x : 4);
> +}
> +
> +/* Not zero so should not optimize. */
> +__attribute__((noipa)) unsigned int fred(int x) {
> + return (x >= -4 ? x : -4) + (x <= -4 ? -x : -4);
> +}
> +
> +/* Incorrect pattern. */
> +__attribute__((noipa)) unsigned int goo(int x) {
> + return (x <= 0 ? x : 0) + (x >= 0 ? -x : 0);
> +}
> +
> +/* Incorrect pattern. */
> +__attribute__((noipa)) int qux(int x) {
> + return (x >= 0 ? x : 0) + (x >= 0 ? x : 0);
> +}
> +
> +/* { dg-final {scan-tree-dump-times " ABS_EXPR " 4 "optimized" } } */
>
> base-commit: 6af530f914801f5e561057da55c41480f28751f7
> --
> 2.31.1
>
