Re: [PR38711] Use DF_LIVE in IRA if it available (for -O2 and higher)

[Steven Bosscher]

On Sat, Oct 27, 2012 at 11:49 PM, Steven Bosscher wrote:
> So I'm going to revert this patch.

Or actually better, this lighter-weight patch. Will commit after the
usual testing.

        * ira.c (ira): Remove DF_LIVE if the problem is in the stack.
       (do_reload): Add it back at the end.

Index: ira.c
===================================================================
--- ira.c       (revision 192878)
+++ ira.c       (working copy)
@@ -4399,6 +4399,16 @@ ira (FILE *f)
   setup_prohibited_mode_move_regs ();

   df_note_add_problem ();
+
+  /* DF_LIVE can't be used in the register allocator, too many other
+     parts of the compiler depend on using the "classic" liveness
+     interpretation of the DF_LR problem.  See PR38711.
+     Remove the problem, so that we don't spend time updating it in
+     any of the df_analyze() calls during IRA/LRA.  */
+  if (optimize > 1)
+    df_remove_problem (df_live);
+  gcc_checking_assert (df_live == NULL);
+
 #ifdef ENABLE_CHECKING
   df->changeable_flags |= DF_VERIFY_SCHEDULED;
 #endif
@@ -4678,6 +4688,12 @@ do_reload (void)
   df_scan_alloc (NULL);
   df_scan_blocks ();

+  if (optimize > 1)
+    {
+      df_live_add_problem ();
+      df_live_set_all_dirty ();
+    }
+
   if (optimize)
     df_analyze ();