[Bug rtl-optimization/86096] [8/9 Regression] ICE: qsort checking failed (error: qsort comparator non-negative on sorted output: 0)

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86096

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Alexander Monakov from comment #1)
> df_mw_compare has:
> 
>    if (mw1->mw_reg != mw2->mw_reg)
>      return mw1->mw_order - mw2->mw_order;
> 
> Note mw_reg in the 'if' vs mw_order in the 'return'. This is invalid.
> 
> It's simpler and more efficient to just use mw_order as the last tie-breaker
> regardless of mw_reg value.

patch is pre-approved