Re: [PATCH] match.pd: Add new division pattern [PR104992]

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

On Tue, Jul 26, 2022 at 4:32 PM Sam Feifer via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> >
> > int f(_Complex int x, _Complex int y)
> > {
> >   return x == x / y * y;
> > }
> >
>
> After some research about mod with complex types, I found that the binary
> mod operation does not work with complex types. If so, the complex test
> case should not be simplified. Is this correct?
>
> I should also note that the above function, f, causes a segmentation fault.
> I can only get a function with complex types to compile by breaking up the
> operations like I would in a forward propagation test case. When I do this,
> it does not simplify into mod, which I think is right.

_Complex int are strange beasts, I'd simply avoid the transform for them.

Can you please move the pattern next to the existing div/mod patterns,
like after the related

/* Simplify (A / B) * B + (A % B) -> A.  */
(for div (trunc_div ceil_div floor_div round_div)
     mod (trunc_mod ceil_mod floor_mod round_mod)
  (simplify
   (plus:c (mult:c (div @0 @1) @1) (mod @0 @1))
   @0))

pattern?

+/* x / y * y == x -> x % y == 0.  */
+(simplify
+  (eq (mult (trunc_div @0 @1) @1) @0)
+  (eq (trunc_mod @0 @1) { build_zero_cst TREE_TYPE(@0); }))

there are parens missing around the TREE_TYPE (@0), how did you test
the patch?  You probably want :s on the trunc_div and as Andrew said
:c on the eq and the mult.

Richard.

> Thanks
> -Sam
>
>
> > For vector try (which works for both the C and C++ front-end):
> > #define vector __attribute__((vector_size(4*sizeof(int)) ))
> > vector int f(vector int x, vector int y)
> > {
> >   return x == x / y * y;
> > }
> >
> > That is for the vector case, == still returns a vector type.
> >
> > Thanks,
> > Andrew Pinski
> >
> > >
> > > Thanks
> > > -Sam
> > >
> > >> Thanks,
> > >> Andrew Pinski
> > >>
> > >> > diff --git a/gcc/testsuite/gcc.dg/pr104992-1.c
> > b/gcc/testsuite/gcc.dg/pr104992-1.c
> > >> > new file mode 100644
> > >> > index 00000000000..a80e5e180ce
> > >> > --- /dev/null
> > >> > +++ b/gcc/testsuite/gcc.dg/pr104992-1.c
> > >> > @@ -0,0 +1,30 @@
> > >> > +/* PR tree-optimization/104992 */
> > >> > +/* { dg-do run } */
> > >> > +/* { dg-options "-O2"} */
> > >> > +
> > >> > +#include "pr104992.c"
> > >> > +
> > >> > +int main () {
> > >> > +
> > >> > +    /* Should be true.  */
> > >> > +    if (!foo(6, 3)
> > >> > +        || !bar(12, 2)
> > >> > +        || !baz(34, 17)
> > >> > +        || !qux(50, 10)
> > >> > +        || !fred(16, 8)
> > >> > +        || !baz(-9, 3)
> > >> > +        || !baz(9, -3)
> > >> > +        || !baz(-9, -3)
> > >> > +        ) {
> > >> > +            __builtin_abort();
> > >> > +         }
> > >> > +
> > >> > +    /* Should be false.  */
> > >> > +    if (foo(5, 30)
> > >> > +        || bar(72, 27)
> > >> > +        || baz(42, 15)) {
> > >> > +            __builtin_abort();
> > >> > +        }
> > >> > +
> > >> > +    return 0;
> > >> > +}
> > >> > diff --git a/gcc/testsuite/gcc.dg/pr104992.c
> > b/gcc/testsuite/gcc.dg/pr104992.c
> > >> > new file mode 100644
> > >> > index 00000000000..b4b0ca53118
> > >> > --- /dev/null
> > >> > +++ b/gcc/testsuite/gcc.dg/pr104992.c
> > >> > @@ -0,0 +1,35 @@
> > >> > +/* PR tree-optimization/104992 */
> > >> > +/* { dg-do compile } */
> > >> > +/* { dg-options "-O2 -fdump-tree-optimized" } */
> > >> > +
> > >> > +/* Form from PR.  */
> > >> > +__attribute__((noipa)) unsigned foo(unsigned x, unsigned y)
> > >> > +{
> > >> > +    return x / y * y == x;
> > >> > +}
> > >> > +
> > >> > +__attribute__((noipa)) unsigned bar(unsigned x, unsigned y) {
> > >> > +    return x == x / y * y;
> > >> > +}
> > >> > +
> > >> > +/* Signed test case.  */
> > >> > +__attribute__((noipa)) unsigned baz (int x, int y) {
> > >> > +    return x / y * y == x;
> > >> > +}
> > >> > +
> > >> > +/* Changed order.  */
> > >> > +__attribute__((noipa)) unsigned qux (unsigned x, unsigned y) {
> > >> > +    return y * (x / y) == x;
> > >> > +}
> > >> > +
> > >> > +/* Wrong order.  */
> > >> > +__attribute__((noipa)) unsigned fred (unsigned x, unsigned y) {
> > >> > +    return y * x / y == x;
> > >> > +}
> > >> > +
> > >> > +/* Wrong pattern.  */
> > >> > +__attribute__((noipa)) unsigned waldo (unsigned x, unsigned y,
> > unsigned z) {
> > >> > +    return x / y * z == x;
> > >> > +}
> > >> > +
> > >> > +/* { dg-final {scan-tree-dump-times " % " 4 "optimized" } } */
> > >> >
> > >> > base-commit: 633e9920589ddfaf2d6da1c24ce99b18a2638db4
> > >> > --
> > >> > 2.31.1
> > >> >
> > >>
> >
> >