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

[amonakov at gcc dot gnu.org]

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

Alexander Monakov <amonakov at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2018-06-09
                 CC|                            |amonakov at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #1 from Alexander Monakov <amonakov at gcc dot gnu.org> ---
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.