fwprop: invoke change_is_worthwhile to judge if a replacement is worthwhile

gcc/
	* fwprop.cc (try_fwprop_subst_pattern): Invoke change_is_worthwhile
	to judge if a replacement is worthwhile.  Remove single_set check
	and add is_debug_insn check.
	* recog.cc (swap_change): Invalidate recog_data when the cached INSN
	is swapped out.
	* rtl-ssa/changes.cc (rtl_ssa::changes_are_worthwhile): Check if the
	insn cost of new rtl is unknown and fail the replacement.

1 files changed, 14 insertions, 23 deletions

diff --git a/gcc/fwprop.cc b/gcc/fwprop.cc
index de54392..bfdc7a1 100644
--- a/gcc/fwprop.cc
+++ b/gcc/fwprop.cc
@@ -453,7 +453,7 @@ try_fwprop_subst_pattern (obstack_watermark &attempt, insn_change &use_change,
       && (prop.changed_mem_p ()
 	  || contains_mem_rtx_p (src)
 	  || use_insn->is_asm ()
-	  || !single_set (use_rtl)))
+	  || use_insn->is_debug_insn ()))
     {
       if (dump_file && (dump_flags & TDF_DETAILS))
 	fprintf (dump_file, "cannot propagate from insn %d into"
@@ -471,29 +471,20 @@ try_fwprop_subst_pattern (obstack_watermark &attempt, insn_change &use_change,
       redo_changes (0);
     }
 
-  /* ??? In theory, it should be better to use insn costs rather than
-     set_src_costs here.  That would involve replacing this code with
-     change_is_worthwhile.  */
   bool ok = recog (attempt, use_change);
-  if (ok && !prop.changed_mem_p () && !use_insn->is_asm ())
-    if (rtx use_set = single_set (use_rtl))
-      {
-	bool speed = optimize_bb_for_speed_p (BLOCK_FOR_INSN (use_rtl));
-	temporarily_undo_changes (0);
-	auto old_cost = set_src_cost (SET_SRC (use_set),
-				      GET_MODE (SET_DEST (use_set)), speed);
-	redo_changes (0);
-	auto new_cost = set_src_cost (SET_SRC (use_set),
-				      GET_MODE (SET_DEST (use_set)), speed);
-	if (new_cost > old_cost
-	    || (new_cost == old_cost && !prop.likely_profitable_p ()))
-	  {
-	    if (dump_file)
-	      fprintf (dump_file, "change not profitable"
-		       " (cost %d -> cost %d)\n", old_cost, new_cost);
-	    ok = false;
-	  }
-      }
+  if (ok
+      && !prop.changed_mem_p ()
+      && !use_insn->is_asm ()
+      && !use_insn->is_debug_insn ())
+    {
+      bool strict_p = !prop.likely_profitable_p ();
+      if (!change_is_worthwhile (use_change, strict_p))
+	{
+	  if (dump_file)
+	    fprintf (dump_file, "change not profitable");
+	  ok = false;
+	}
+    }
 
   if (!ok)
     {