[Bug tree-optimization/66163] New: [6 Regression] Not working Firefox built with LTO

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66163

            Bug ID: 66163
           Summary: [6 Regression] Not working Firefox built with LTO
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: hubicka at ucw dot cz
          Reporter: marxin at gcc dot gnu.org
  Target Milestone: ---

I've just built FF with LTO and -O3 and the browser is unable to render a
complex page. Unfortunately that's an error in MessageChannel, can't catch it
in gdb:

###!!! [Parent][MessageChannel] Error: Channel error: cannot send/recv

Starting from r222054, where following hunk is responsible for the error:

+  /* THIS argument of method is always non-NULL.  */
+  if (TREE_CODE (TREE_TYPE (current_function_decl)) == METHOD_TYPE
+      && arg == DECL_ARGUMENTS (current_function_decl)
+      && flag_delete_null_pointer_checks)
+    return true;

As I added dump for cases where we return, it's more than 100k occurrences.
Any idea Honza how to isolate the issue?

Thanks,
Martin