Re: [PATCH] match.pd: Add new abs pattern [PR94290]

[Andrew Pinski <pinskia@gmail.com>]

On Thu, Jul 14, 2022 at 12:38 PM Sam Feifer <sfeifer@redhat.com> wrote:
>
>
>
> On Thu, Jul 14, 2022 at 1:24 PM Andrew Pinski <pinskia@gmail.com> wrote:
>>
>> On Thu, Jul 14, 2022 at 7:09 AM Sam Feifer <sfeifer@redhat.com> wrote:
>> >
>> >
>> > On Wed, Jul 13, 2022 at 3:36 PM Andrew Pinski <pinskia@gmail.com> wrote:
>> >>
>> >> 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 for the feedback. I'm not quite sure what a vector test case would look like for this. Could I get some guidance on that?
>>
>> Yes this should produce the pattern at forwprop1 time (with the C++
>> front-end, the C front-end does not support vector selects):
>> typedef int __attribute__((vector_size(4*sizeof(int)))) vint;
>>
>> vint foo(vint x) {
>>     vint t = (x >= 0 ? x : 0) ;
>>     vint xx = -x;
>>     vint t1 =  (xx >= 0 ? xx : 0);
>>     return t + t1;
>> }
>>
>> int foo(int x) {
>>     int t = (x >= 0 ? x : 0) ;
>>     int xx = -x;
>>     int t1 =  (xx >= 0 ? xx : 0);
>>     return t + t1;
>> }
>>
>> Thanks,
>> Andrew Pinski
>>
>
> Thanks for the help. I'm still having trouble with the vector test, though. When I try to compile, I get an error saying "used vector type where scalar is required", referring to the max expressions. How do I use the max expression with two vectors as the inputs?

As I mentioned it only works with the C++ front-end :). The C
front-end does not support ?: with vectors types.

Thanks,
Andrew Pinski

>
> Thanks
> -Sam
>>
>>
>> >
>> > Thanks
>> > -Sam
>> >
>> >>
>> >> 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
>> >> >
>> >>
>>