[gcc r13-6866] match.pd: Fix up fneg/fadd simplification [PR109230]

[gcc r13-6866] match.pd: Fix up fneg/fadd simplification [PR109230]

[Jakub Jelinek]

https://gcc.gnu.org/g:07fc3491260e6b5d261433c977a4e069f5ab40c1

commit r13-6866-g07fc3491260e6b5d261433c977a4e069f5ab40c1
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Sun Mar 26 20:17:00 2023 +0200

    match.pd: Fix up fneg/fadd simplification [PR109230]
    
    The following testcase is miscompiled on aarch64-linux.  match.pd
    has a simplification for addsub, where it negates one of the vectors
    in twice as large floating point element vector (effectively negating every
    other element) and then doing addition.
    But a requirement for that is that the permutation picks the right elements,
    in particular 0, nelts+1, 2, nelts+3, 4, nelts+5, ...
    The pattern tests this with sel.series_p (0, 2, 0, 2) check, which as
    documented verifies that the even elements of the permutation mask are
    identity, but doesn't say anything about the others.
    The following patch fixes it by also checking that the odd elements
    start at nelts + 1 with the same step of 2.
    
    2023-03-26  Jakub Jelinek  <jakub@redhat.com>
    
            PR tree-optimization/109230
            * match.pd (fneg/fadd simplify): Verify also odd permutation indexes.
    
            * gcc.dg/pr109230.c: New test.

Diff:
---
 gcc/match.pd                    |  1 +
 gcc/testsuite/gcc.dg/pr109230.c | 31 +++++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/gcc/match.pd b/gcc/match.pd
index e352bd422f5..b8d3538b809 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -8096,6 +8096,7 @@ and,
        scalar_mode inner_mode = GET_MODE_INNER (vec_mode);
      }
      (if (sel.series_p (0, 2, 0, 2)
+	  && sel.series_p (1, 2, nelts + 1, 2)
 	  && GET_MODE_2XWIDER_MODE (inner_mode).exists (&wide_elt_mode)
 	  && multiple_p (GET_MODE_NUNITS (vec_mode), 2, &wide_nunits)
 	  && related_vector_mode (vec_mode, wide_elt_mode,
diff --git a/gcc/testsuite/gcc.dg/pr109230.c b/gcc/testsuite/gcc.dg/pr109230.c
new file mode 100644
index 00000000000..9c4ff054686
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr109230.c
@@ -0,0 +1,31 @@
+/* PR tree-optimization/109230 */
+/* { dg-do run } */
+/* { dg-options "-O2 -Wno-psabi" } */
+
+#if __SIZEOF_FLOAT__ == __SIZEOF_INT__
+typedef float V __attribute__((vector_size (4 * sizeof (float))));
+typedef int VI __attribute__((vector_size (4 * sizeof (float))));
+
+__attribute__((noipa)) V
+foo (V x, V y)
+{
+  V a = x - y;
+  V b = y + x;
+  return __builtin_shuffle (b, a, (VI) { 0, 5, 2, 3 });
+}
+
+int
+main ()
+{
+  V a = (V) { 1.0f, 2.0f, 3.0f, 4.0f };
+  V b = (V) { 8.0f, 9.0f, 10.0f, 11.0f };
+  V c = foo (a, b);
+  if (c[0] != 9.0f || c[1] != -7.0f || c[2] != 13.0f || c[3] != 15.0f)
+    __builtin_abort ();
+}
+#else
+int
+main ()
+{
+}
+#endif