ira: Fix old-reload targets [PR103974]

The new IRA heuristics would need more work on old-reload targets,
since flattening needs to be able to undo the cost propagation.
It's doable, but hardly seems worth it.

This patch therefore makes all the new calls to
ira_subloop_allocnos_can_differ_p return false if !ira_use_lra_p.
The color_pass code that predated the new function (and that was
the source of ira_subloop_allocnos_can_differ_p) continues to
behave as before.

It's a hack, but at least it has the advantage that the new parameter
would become obviously unused if reload and (!)ira_use_lra_p were
removed.  The hack should therefore disappear alongside reload.

gcc/
	PR rtl-optimization/103974
	* ira-int.h (ira_subloop_allocnos_can_differ_p): Take an
	extra argument, default true, that says whether old-reload
	targets should be excluded.
	* ira-color.c (color_pass): Pass false.

diff --git a/gcc/ira-color.c b/gcc/ira-color.c
index 36f3f4d..59d978f 100644 (file)
--- a/gcc/ira-color.c
+++ b/gcc/ira-color.c
@@ -3664,7 +3664,8 @@ color_pass (ira_loop_tree_node_t loop_tree_node)
          ira_assert (bitmap_bit_p (subloop_node->all_allocnos,
                                    ALLOCNO_NUM (subloop_allocno)));
          if (ira_single_region_allocno_p (a, subloop_allocno)
-             || !ira_subloop_allocnos_can_differ_p (a, hard_regno >= 0))
+             || !ira_subloop_allocnos_can_differ_p (a, hard_regno >= 0,
+                                                    false))
            {
              gcc_assert (!ALLOCNO_MIGHT_CONFLICT_WITH_PARENT_P
                          (subloop_allocno));

diff --git a/gcc/ira-int.h b/gcc/ira-int.h
index e1e6802..e80fdeb 100644 (file)
--- a/gcc/ira-int.h
+++ b/gcc/ira-int.h
@@ -1607,10 +1607,16 @@ ira_loop_border_costs::move_between_loops_cost () const
 
 /* Return true if subloops that contain allocnos for A's register can
    use a different assignment from A.  ALLOCATED_P is true for the case
-   in which allocation succeeded for A.  */
+   in which allocation succeeded for A.  EXCLUDE_OLD_RELOAD is true if
+   we should always return false for non-LRA targets.  (This is a hack
+   and should be removed along with old reload.)  */
 inline bool
-ira_subloop_allocnos_can_differ_p (ira_allocno_t a, bool allocated_p = true)
+ira_subloop_allocnos_can_differ_p (ira_allocno_t a, bool allocated_p = true,
+                                  bool exclude_old_reload = true)
 {
+  if (exclude_old_reload && !ira_use_lra_p)
+    return false;
+
   auto regno = ALLOCNO_REGNO (a);
 
   if (pic_offset_table_rtx != NULL