[Bug middle-end/64498] [5 Regression] Cannot build Firefox with LTO: ICE in substitute_and_fold_dom_walker::before_dom_children

["hubicka at ucw dot cz" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64498

--- Comment #2 from Jan Hubicka <hubicka at ucw dot cz> ---
> Problem is hidden in flag_var_tracking_assignments, which is set to false.
> Thus, MAY_HAVE_DEBUG_INSNS is set to false. Unfortunately, Firefox contains
> couple of third party libraries that have -g as a default option. So that DCE
> after a statements removal does not remove debug statements that use result of
> a statement and verifier fails.

flag_var_tracking_assignments is marked as Optimization in common.opt while
rest
of debug machinery is not Optimization.  This means that we try to preserve
assignments
in functions that was compiled with -g at compile time, but then we never
consume
it....

Shall we drop flag_var_tracking_assignments to 0 and remove the debug
statements after streaming in in these cases? Also inliner probably needs to
remove the statements when it inlines from function with
flag_var_tracking_assignments to one with !flag_var_tracking_assignments

Honza