tree-ssa-forwprop.c (simplify_gimple_switch): Enhance check for which sign-changes we allow when...

2014-04-14  Richard Biener  <rguenther@suse.de>

	* tree-ssa-forwprop.c (simplify_gimple_switch): Enhance
	check for which sign-changes we allow when forwarding
	a converted value into a switch.

	* g++.dg/tree-ssa/forwprop-switch.C: New testcase.

From-SVN: r209372

gcc/ChangeLog

+2014-04-14  Richard Biener  <rguenther@suse.de>
+
+	* tree-ssa-forwprop.c (simplify_gimple_switch): Enhance
+	check for which sign-changes we allow when forwarding
+	a converted value into a switch.
+
 2014-04-14  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* stor-layout.c (place_field): Finalize non-constant offset for the

gcc/testsuite/ChangeLog

+2014-04-14  Richard Biener  <rguenther@suse.de>
+
+	* g++.dg/tree-ssa/forwprop-switch.C: New testcase.
+
 2014-04-14  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>
 
 	* gcc.dg/lto/pr55113_0.c: Skip on i?86-*-solaris2.1[0-1]*.

gcc/testsuite/g++.dg/tree-ssa/forwprop-switch.C

+// { dg-do compile }
+// { dg-options "-O -fdump-tree-cddce1" }
+
+enum Scale  { E1, E2, E3, E4, E5, E6, E7, E8 };
+
+int Test(Scale s)
+{ 
+  switch(s)
+    {
+      case E1: return 12;
+      case E2: return 17;
+      case E3: return 22;
+      case E4: return 42;
+      default:  break;
+    }
+  return 0;
+}
+
+// tree forwprop should have eliminated the (int) s cast for the
+// switch value and directly switch on the 's' parameter
+
+// { dg-final { scan-tree-dump-not "\\\(int\\\)" "cddce1" } }
+// { dg-final { scan-tree-dump "switch \\\(s_.\\\(D\\\)\\\)" "cddce1" } }
+// { dg-final { cleanup-tree-dump "cddce1" } }

gcc/tree-ssa-forwprop.c

@@ -1356,43 +1356,38 @@ simplify_gimple_switch_label_vec (gimple stmt, tree index_type)
 static bool
 simplify_gimple_switch (gimple stmt)
 {
-  tree cond = gimple_switch_index (stmt);
-  tree def, to, ti;
-  gimple def_stmt;
-
   /* The optimization that we really care about is removing unnecessary
      casts.  That will let us do much better in propagating the inferred
      constant at the switch target.  */
+  tree cond = gimple_switch_index (stmt);
   if (TREE_CODE (cond) == SSA_NAME)
     {
-      def_stmt = SSA_NAME_DEF_STMT (cond);
-      if (is_gimple_assign (def_stmt))
+      gimple def_stmt = SSA_NAME_DEF_STMT (cond);
+      if (gimple_assign_cast_p (def_stmt))
 	{
-	  if (gimple_assign_rhs_code (def_stmt) == NOP_EXPR)
-	    {
-	      int need_precision;
-	      bool fail;
-
-	      def = gimple_assign_rhs1 (def_stmt);
-
-	      to = TREE_TYPE (cond);
-	      ti = TREE_TYPE (def);
-
-	      /* If we have an extension that preserves value, then we
-		 can copy the source value into the switch.  */
-
-	      need_precision = TYPE_PRECISION (ti);
-	      fail = false;
-	      if (! INTEGRAL_TYPE_P (ti))
-		fail = true;
-	      else if (TYPE_UNSIGNED (to) && !TYPE_UNSIGNED (ti))
-		fail = true;
-	      else if (!TYPE_UNSIGNED (to) && TYPE_UNSIGNED (ti))
-		need_precision += 1;
-	      if (TYPE_PRECISION (to) < need_precision)
-		fail = true;
+	  tree def = gimple_assign_rhs1 (def_stmt);
+	  if (TREE_CODE (def) != SSA_NAME)
+	    return false;
 
-	      if (!fail)
+	  /* If we have an extension or sign-change that preserves the
+	     values we check against then we can copy the source value into
+	     the switch.  */
+	  tree ti = TREE_TYPE (def);
+	  if (INTEGRAL_TYPE_P (ti)
+	      && TYPE_PRECISION (ti) <= TYPE_PRECISION (TREE_TYPE (cond)))
+	    {
+	      size_t n = gimple_switch_num_labels (stmt);
+	      tree min = NULL_TREE, max = NULL_TREE;
+	      if (n > 1)
+		{
+		  min = CASE_LOW (gimple_switch_label (stmt, 1));
+		  if (CASE_HIGH (gimple_switch_label (stmt, n - 1)))
+		    max = CASE_HIGH (gimple_switch_label (stmt, n - 1));
+		  else
+		    max = CASE_LOW (gimple_switch_label (stmt, n - 1));
+		}
+	      if ((!min || int_fits_type_p (min, ti))
+		  && (!max || int_fits_type_p (max, ti)))
 		{
 		  gimple_switch_set_index (stmt, def);
 		  simplify_gimple_switch_label_vec (stmt, ti);