[Bug middle-end/109849] suboptimal code for vector walking loop

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109849

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Jan Hubicka from comment #0)
> saving an instruction. Why we do not move stack+8 updating out of the loop?

Maybe because of a clobber:
  cur$second_5 = MEM[(const struct pairD.26349 &)_7 +
18446744073709551608].secondD.27577;
  # PT = nonlocal escaped 
  _4 = _7 + 18446744073709551608;
  # .MEM_9 = VDEF <.MEM_1>
  stackD.26352.D.27437._M_implD.26667.D.26744._M_finishD.26670 = _4;
  # .MEM_10 = VDEF <.MEM_9>
  MEM[(struct pairD.26349 *)_7 + -8B] ={v} {CLOBBER};