re PR rtl-optimization/34012 (Pessimization caused by fwprop)

	PR rtl-optimization/34012
	* fwprop.c (try_fwprop_subst): Do not replace if the new
	SET_SRC has a higher cost than the old one.

	* gcc.target/i386/pr34012.c: New test.

Co-Authored-By: Jakub Jelinek <jakub@redhat.com>

From-SVN: r130043

gcc/ChangeLog

+2007-11-09  Paolo Bonzini  <bonzini@gnu.org>
+	    Jakub Jelinek  <jakub@redhat.com>
+
+	PR rtl-optimization/34012
+	* fwprop.c (try_fwprop_subst): Do not replace if the new
+	SET_SRC has a higher cost than the old one.
+
 2007-11-09  Eric Botcazou  <ebotcazou@libertysurf.fr>
 
 	PR rtl-optimization/33732

gcc/fwprop.c

@@ -675,6 +675,9 @@ try_fwprop_subst (struct df_ref *use, rtx *loc, rtx new, rtx def_insn, bool set_
   rtx insn = DF_REF_INSN (use);
   enum df_ref_type type = DF_REF_TYPE (use);
   int flags = DF_REF_FLAGS (use);
+  rtx set = single_set (insn);
+  int old_cost = rtx_cost (SET_SRC (set), SET);
+  bool ok;
 
   if (dump_file)
     {
@@ -685,11 +688,34 @@ try_fwprop_subst (struct df_ref *use, rtx *loc, rtx new, rtx def_insn, bool set_
       fprintf (dump_file, "\n");
     }
 
-  if (validate_unshare_change (insn, loc, new, false))
+  validate_unshare_change (insn, loc, new, true);
+  if (!verify_changes (0))
+    {
+      if (dump_file)
+	fprintf (dump_file, "Changes to insn %d not recognized\n",
+		 INSN_UID (insn));
+      ok = false;
+    }
+
+  else if (rtx_cost (SET_SRC (set), SET) > old_cost)
+    {
+      if (dump_file)
+	fprintf (dump_file, "Changes to insn %d not profitable\n",
+		 INSN_UID (insn));
+      ok = false;
+    }
+
+  else
     {
-      num_changes++;
       if (dump_file)
 	fprintf (dump_file, "Changed insn %d\n", INSN_UID (insn));
+      ok = true;
+    }
+
+  if (ok)
+    {
+      confirm_change_group ();
+      num_changes++;
 
       df_ref_remove (use);
       if (!CONSTANT_P (new))
@@ -697,13 +723,10 @@ try_fwprop_subst (struct df_ref *use, rtx *loc, rtx new, rtx def_insn, bool set_
 	  update_df (insn, loc, DF_INSN_USES (def_insn), type, flags);
 	  update_df (insn, loc, DF_INSN_EQ_USES (def_insn), type, flags);
 	}
-      return true;
     }
   else
     {
-      if (dump_file)
-	fprintf (dump_file, "Changes to insn %d not recognized\n",
-		 INSN_UID (insn));
+      cancel_changes (0);
 
       /* Can also record a simplified value in a REG_EQUAL note, making a
 	 new one if one does not already exist.  */
@@ -724,9 +747,9 @@ try_fwprop_subst (struct df_ref *use, rtx *loc, rtx new, rtx def_insn, bool set_
 			 type, DF_REF_IN_NOTE);
 	    }
 	}
-
-      return false;
     }
+
+  return ok;
 }
 
 

gcc/testsuite/ChangeLog

+2007-11-09  Paolo Bonzini  <bonzini@gnu.org>
+	    Jakub Jelinek  <jakub@redhat.com>
+
+	PR rtl-optimization/34012
+	* gcc.target/i386/pr34012.c: New test.
+
 2007-11-09  Richard Guenther  <rguenther@suse.de>
 
 	PR tree-optimization/33604

gcc/testsuite/gcc.target/i386/pr34012.c

+/* PR rtl-optimization/34012 */
+/* { dg-do compile } */
+/* { dg-require-effective-target lp64 } */
+/* { dg-options "-O2" } */
+
+void bar (long int *);
+void
+foo (void)
+{
+  long int buf[10];
+  buf[0] = 0x0808080808080808;
+  buf[1] = 0x0808080808080808;
+  buf[2] = 0x0808080808080808;
+  buf[3] = 0x0808080808080808;
+  buf[4] = 0x0808080808080808;
+  buf[5] = 0x0808080808080808;
+  buf[6] = 0x0808080808080808;
+  buf[7] = 0x0808080808080808;
+  buf[8] = 0x0808080808080808;
+  buf[9] = 0x0808080808080808;
+  bar (buf);
+}
+
+/* Check that CSE did its job and fwprop hasn't undone it.  */
+/* { dg-final { scan-assembler-times "578721382704613384|0808080808080808" 1 } } */