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

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

On Mon, Jul 18, 2022 at 7:31 PM Sam Feifer via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> Just realized I had mixed up the 9 and the 2 when labelling the patch. This
> patch is referring to pr94920 not pr94290. Attached is a fixed patch file.
> Sorry for any confusion.

Can you put the patterns somewhere related?  The abs producing one
seems to fit around line 323, the max producing before line 3415?

+/* (x <= 0 ? -x : 0) -> max(-x, 0).  */
+(simplify
+  (cond (le @0 integer_zerop@1) (negate @0) integer_zerop@1)
+  (max (negate @0) @1))

you can re-use the existing (negate @0) in the result by doing

+/* (x <= 0 ? -x : 0) -> max(-x, 0).  */
+(simplify
+  (cond (le @0 integer_zerop@1) (negate@2 @0) integer_zerop@1)
+  (max @2 @1))

OK with those changes.

Thanks,
Richard.

> On Mon, Jul 18, 2022 at 9:07 AM Sam Feifer <sfeifer@redhat.com> wrote:
>
> > Here's an updated version of the patch.
> >
> > Thanks
> > -Sam
> >
> > On Thu, Jul 14, 2022 at 3:54 PM Andrew Pinski <pinskia@gmail.com> wrote:
> >
> >> 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
> >> >> >> >
> >> >> >>
> >> >>
> >>
> >>