[Bug tree-optimization/90018] [7/8/9 Regression] r265453 miscompiled 527.cam4_r in SPEC CPU 2017

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90018

--- Comment #18 from Richard Biener <rguenth at gcc dot gnu.org> ---
Created attachment 46131
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=46131&action=edit
patch for GCC 9

So trunk, instead of grouping (a) and (b) groups (d) and (b), leaving (a)
alone.

  for (int i = 0; i < n; ++i)
    {
      /* We may not apply interleaving to the group (a), (b) because of (c). 
*/
      double tem1 = a4[i*4] + a4[i*4+n*4] /* (a) */;
      double tem2 = a4[i*4+2*n*4+1];
      a4[i*4+n*4+1] = tem1; /* (c) */
      a4[i*4+1] = tem2;
      double tem3 = a4[i*4] - tem2;
      double tem4 = tem3 + a4[i*4+n*4];
      a4[i*4+n*4+1] = tem4 + a4[i*4+n*4+1] /* (b) */;
    }