https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94148
--- Comment #5 from Segher Boessenkool <segher at gcc dot gnu.org> --- commit 5c7e6d4bdf879b437b43037e10453275acabf521 Author: Segher Boessenkool <seg...@kernel.crashing.org> Date: Thu Mar 12 07:12:50 2020 +0000 df: Don't abuse bb->aux (PR94148, PR94042) The df dataflow solvers use the aux field in the basic_block struct, although that is reserved for any use by passes. And not only that, it is required that you set all such fields to NULL before calling the solvers, or you quietly get wrong results. This changes the solvers to use a local array for last_change_age instead, just like it already had a local array for last_visit_age. PR rtl-optimization/94148 PR rtl-optimization/94042 * df-core.c (BB_LAST_CHANGE_AGE): Delete. (df_worklist_propagate_forward): New parameter last_change_age, use that instead of bb->aux. (df_worklist_propagate_backward): Ditto. (df_worklist_dataflow_doublequeue): Use a local array last_change_age.