[Bug tree-optimization/123672] [15/16 Regression] __builtin_shufflevector() produces incorrect code with -ftree-forwprop

[jakub at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123672

--- Comment #8 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Slightly improved testcase so that it verifies all elements of all involved
vectors:
typedef int V __attribute__((vector_size (4 * sizeof (int))));

[[gnu::noipa]] void
foo (V *x, V *y)
{
  V a = *x;
  V b = *y;
  V c = __builtin_shufflevector (a, a, 0, 2, 0, 2);
  V d = __builtin_shufflevector (a, a, 1, 3, 1, 3);
  V e = __builtin_shufflevector (b, b, 0, 2, 0, 2);
  V f = __builtin_shufflevector (b, b, 1, 3, 1, 3);
  V g = __builtin_shufflevector (c + d, c - d, 0, 4, 1, 5);
  V h = __builtin_shufflevector (e + f, e - f, 0, 4, 1, 5);
  *x = g;
  *y = h;
}

int
main ()
{
  V a = { 1, 21, 2, 32 };
  V b = { 3, 43, 4, 54 };
  foo (&a, &b);
  if (a[0] != 22 || a[1] != -20 || a[2] != 34 || a[3] != -30
      || b[0] != 46 || b[1] != -40 || b[2] != 58 || b[3] != -50)
    __builtin_abort ();
}