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 --git a/gcc/match.pd b/gcc/match.pd
index e352bd422f52338d5deea38820c8287d9622b29e..b8d3538b80947dfc46d0f90d246317d64a4ace5d 100644 (file)
--- 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 (file)
index 0000000..9c4ff05
--- /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