[Bug tree-optimization/121256] [13/14/15/16 regression] ffmpeg miscompiled with -O2 -march=znver2

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121256

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
Nope, it seems the initial recurrence vector is bogus:

  vect_cst__84 = {blue_lsm.10_58, blue_lsm.10_58, blue_lsm.10_58,
blue_lsm.10_58, blue_lsm.10_58, blue_lsm.10_58, blue_lsm.10_58,
blue_lsm.10_58};
..
  # vect_vec_recur_.17_85 = PHI <vect_bt_41.15_48(9), vect_cst__84(2)>