[Bug tree-optimization/80928] SLP vectorization does not handle induction in outer loop vectorization

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80928

--- Comment #29 from Richard Biener <rguenth at gcc dot gnu.org> ---
So a testcase for missed outer loop induction SLP (and nested cycle SLP) is
for example

int a[1024];
void foo (unsigned n)
{
  for (int i = 0; i < 1020; i += 4)
    {
      int suma = a[i];
      int sumb = a[i+1];
      int sumc = a[i+2];
      int sumd = a[i+3];
      for (unsigned j = 0; j < 17; ++j)
        {
          suma = (suma ^ i) + 1;
          sumb = (sumb ^ i) + 2;
          sumc = (sumc ^ i) + 3;
          sumd = (sumd ^ i) + 4;
        }
      a[i] = suma;
      a[i+1] = sumb;
      a[i+2] = sumc;
      a[i+3] = sumd;
    }
}