[Bug rtl-optimization/97286] simplified subreg used outside of the loop can cause conflict and cause an extra move inside the loop

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97286

--- Comment #10 from Richard Sandiford <rsandifo at gcc dot gnu.org> ---
(In reply to Richard Sandiford from comment #9)
> … Or perhaps we
> could do the optimisation in gimple, so that there is only one loop-carried
> dependency coming into expand.
That is, replace:

  <bb 4> [local count: 955630224]:
  # c_21 = PHI <c_17(4), c_11(3)>
  # ivtmp.7_31 = PHI <ivtmp.7_30(4), ivtmp.7_29(3)>

with a single phi and adjust references accordingly.